RELIABILITY OF RENEWABLE ENERGY: SOLAR
Jordan Lofthouse, BS, Strata Policy
Randy T Simmons, PhD, Utah State University
Ryan M. Yonk, PhD, Utah State University
The Institute of Political Economy (IPE) at Utah State University seeks to promote a better understanding of the
foundations of a free society by conducting research and disseminating findings through publications, classes,
seminars, conferences, and lectures. By mentoring students and engaging them in research and writing projects, IPE
creates diverse opportunities for students in graduate programs, internships, policy groups, and business.
PRIMARY INVESTIGATORS:
Jordan Lofthouse, BS
Strata Policy
Randy T Simmons, Phd
Utah State University
Ryan M. Yonk, Phd
Utah State University
STUDENT RESEARCH ASSOCIATES:
Camille Harmer
Jadyn Naylor
Zach Hopkins
Ryan Taylor
Devin Stein
Garrett White
Bracken Allen
Michael Palmer
TABLE OF CONTENTS
Executive Summary ............................................................................................................................................................. 1
Introduction ......................................................................................................................................................................... 2
Defining Reliability........................................................................................................................................................ 2
How Solar Energy Works .............................................................................................................................................. 2
Photovoltaic Panels ....................................................................................................................................................... 2
Concentrated Solar Power Systems ............................................................................................................................. 3
Economic Reliability of Solar Energy .................................................................................................................................. 6
The High Cost of Solar .................................................................................................................................................. 6
Policies at the State Level ............................................................................................................................................ 6
Incentives at the National Level ................................................................................................................................... 9
Verdict on Economic Reliability .................................................................................................................................... 9
Physical Reliability of Solar Energy .................................................................................................................................. 10
Variability of Solar Energy .......................................................................................................................................... 10
Efficiency and Capacity Factor .................................................................................................................................... 10
Location ....................................................................................................................................................................... 10
Implications for the Electric Grid ................................................................................................................................ 11
What is the Grid? ........................................................................................................................................................ 11
Intermittency ............................................................................................................................................................... 11
Grid Imbalances .......................................................................................................................................................... 12
Using Energy Storage.................................................................................................................................................. 13
Net Metering............................................................................................................................................................... 14
The Need for Long-Distance Transmission................................................................................................................. 15
Verdict on Physical Reliability..................................................................................................................................... 16
Environmental Reliability of Solar Energy ........................................................................................................................ 17
Water .......................................................................................................................................................................... 17
Emissions .................................................................................................................................................................... 18
Manufacturing, Recycling, and Foreign Pollution ....................................................................................................... 19
WildlifeImpacts .......................................................................................................................................................... 20
Verdict on Environmental Reliability........................................................................................................................... 21
Case Study: Solar Energy in Germany .............................................................................................................................. 22
Exaggerated Claims of German Solar Power.............................................................................................................. 22
Economic Reliability .................................................................................................................................................... 22
Physical Reliability ...................................................................................................................................................... 23
Environmental Reliability ............................................................................................................................................ 24
German Solar Power Analysis .................................................................................................................................... 25
Conclusion ......................................................................................................................................................................... 26
EXECUTIVE SUMMARY
Solar power’s growth is driven mainly by government policies rather than market forces. Because policymakers continue
to favor the solar industry with renewable energy mandates and subsidies, the reliability of solar power becomes a
more pressing question. The Institute of Political Economy (IPE) at Utah State University examined the economic,
physical, and environmental implications of solar power to determine its overall reliability. IPE determined that using
tax dollars to mandate and subsidize solar power is not a worthwhile investment because the high costs of overcoming
solar power's unreliability outweigh its limited environmental benefits.
First, solar power is heavily dependent on government subsidies and mandates, and the solar industry is not
economically viable without them. State mandates attempt to increase solar energy production by requiring utilities to
provide a certain amount of power from solar energy. Despite mandates and billions of taxpayer dollars in subsidies,
solar power only supplied 0.4 percent of the United States’ electricity in 2014. Solar power would not exist even on
this small scale without government assistance.
Second, solar power cannot effectively meet electricity demand because it is inefficient and variable. Solar plants are
some of the least efficient electricity generators of all major energy sources. Intermittent cloud cover requires solar
plants to be backed up by traditional fossil fuel plants; solar is not able to supply power consistently without serious
assistance from fossil fuels. Because government policies are causing the solar industry to grow artificially fast, current
infrastructure cannot keep up with solar power’s growth.
Most solar is generated during times of the day when electricity is demanded least. Current solar facilities are generally
located far from population centers, and costly transmission lines have to connect the facilities to distant consumers.
Households that generate their own solar power and sell their surplus place mechanical stress on the electric grid as
electricity flows both to and away from homes, increasing maintenance costs.
Third, hidden environmental costs make solar power less beneficial than most people think. Solar power reduces carbon
emissions because it does not require a fuel source to burn for energy production. Solar power’s intermittency requires
it to be backed up by fossil fuel plants, so the emission benefits of solar power are reduced whenever fossil fuels need
to be burned to maintain a constant supply of power. Chinese manufacturing of solar parts also reduces net
environmental benefits because of destructive waste disposal processes.
Utility-scale solar power plants also use large volumes of water in drought-stricken regions, and the facilities displace
local endangered wildlife. While this report concedes the benefits of solar power’s carbon-free emissions, all of the
aforementioned factors decrease solar power’s net environmental benefits, making it a less worthwhile investment.
Governments are distorting energy markets and misallocating taxpayer dollars by mandating and subsidizing solar
power. Whether solar power will become reliable within the next few decades is an open question best addressed by
markets, not subsidies or mandates.
Reliability of Renewable Energy: Solar
1
INTRODUCTION
Many Americans view solar energy as an environmentally friendly substitute for traditional energy sources. Government
officials reinforce this opinion by subsidizing and mandating solar energy production. It is primarily government policies,
not market forces, that continue to drive the growth of solar power. The United States Energy Information
Administration reported more than $5 billion spent on solar subsidies in 2013, yet solar power provided only 0.3 percent
of U.S. electricity in 2013.1,2 If solar power is not reliable, it is illogical to mandate its use and to invest billions of tax
dollars in it.
DEFINING RELIABILITY
The term “reliability” is ambiguous and goes beyond an energy source’s ability to generate power consistently. To gain
a more comprehensive understanding of solar power, IPE considered solar power’s reliability in terms of its economic,
physical, and environmental implications.
We first explore solar power’s economic reliability, which we define as the ability of an energy source to be selfsustaining and affordable without government mandates or subsidies.
Second, we examine solar power’s physical reliability. For an energy source to be physically reliable, it must be able to
consistently meet electricity demands by supplying and transmitting its power without interruption.
Finally, we examine solar power's environmental reliability. To be environmentally reliable, an alternative energy
source must have fewer environmental impacts than traditional fossil fuels.
HOW SOLAR ENERGY WORKS
PHOTOVOLTAIC PANELS
Photovoltaic (PV) panels directly convert sunlight into electricity. The cells of a PV panel contain materials which absorb
particles of light and emit electrons, generating an electrical current. 3 The three main types of PV panels are
monocrystalline silicon, polycrystalline silicon, and thin-film.4
Of the three panel types, monocrystalline silicon panels are made of the highest-grade silicon, making them the most
efficient type of panel. These panels convert 15-20 percent of incoming sunlight into electricity. Because
monocrystalline panels are the most efficient type, they require the least surface area per unit of energy produced.
They are the most expensive panel type.5
U.S. Energy Information Administration. (2015, March 12). Direct federal financial interventions and subsidies in energy in fiscal year 2013.
Retrieved from
http://www.eia.gov/analysis/requests/subsidy/
2
U.S. Energy Information Administration. (2015, July). Monthly Energy Review. Retrieved from
http://www.eia.doe.gov/totalenergy/data/monthly/pdf/sec1_7.pdf
3
Gil Knier. (2008, August 6) How Do Photovoltaics Work?. NASA Science. Retrieved from http://science.nasa.gov/science-news/science-atnasa/2002/solarcells/
4
SolarEnergy.net. Solar Panel Photovoltaic (PV) Systems. Retrieved from http://solarenergy.net/solar-installation/solar-panel-photovoltaic-pvsystems/
5
Maehlum, M. A. (2015, May 18). Which solar panel type is best? Mono- vs. polycrystalline vs. thin film. Energy Informative. Retrieved from
http://energyinformative.org/best-solar-panel-monocrystalline-polycrystalline-thin-film/
1
Reliability of Renewable Energy: Solar
2
Polycrystalline silicon panels contain lower-grade silicon than monocrystalline panels. The panels are less efficient
than monocrystalline panels, converting only 13-16 percent of incoming sunlight into electricity. These panels require
a larger surface area to generate the same amount of electricity produced by monocrystalline panels.6
Thin-film solar cells consist of one or more ultra-thin light-absorbing layers.7 The thin-film manufacturing process is
simpler than the monocrystalline or polycrystalline manufacturing process but results in panels with lower electricity
conversion rates that range from 7-13 percent.8 Because of these lower conversion rates, even more surface area is
needed to achieve the same energy generation as either of the other panel types. Thin-film solar cells are the cheapest
PV panel system.9
CONCENTRATED SOLAR POWER SYSTEMS
Concentrated solar power (CSP) systems, also known as thermal solar power systems, do not directly convert sunlight
into electricity like PV panels. These systems consist of an array of mirrors or lenses that focus the sun's rays onto a
thermal receiver. The concentrated energy is used to heat water, and the resulting steam is used to drive turbines
which generate electricity.10
There are three main types of CSP systems. The first is a linear concentrator system, depicted in Figure 1. Long Ushaped mirrors focus sunlight onto fluid-filled tubes that run along each mirror. Once the fluid is heated, it flows to a
heat exchanger where it is used to boil water into steam. The steam runs a turbine generator, producing electricity.11
Ibid.
Harris, W. (n.d.). How thin-film solar cells work. How Stuff Works. Retrieved July 7, 2015, from
http://science.howstuffworks.com/environmental/green-science/thin-film-solar-cell1.htm
8
Maehlum, M. A. (2015, May 18). Which solar panel type is best? Mono- vs. polycrystalline vs. thin film. Retrieved from
http://energyinformative.org/best-solar-panel-monocrystalline-polycrystalline-thin-film/#thin-film-solar-cells
9
Solar lease - Solar Panel Costs. (2015, May 8). Retrieved July 7, 2015, from http://www.sunrun.com/solar-lease/cost-of-solar/solar-panels
10
National Renewable Energy Laboratory. (2014, July 25). Concentrating solar power basics. Retrieved from
http://www.nrel.gov/learning/re_csp.html
11
National Renewable Energy Laboratory. (2013, August 20). Linear Concentrator System Basics for Concentrating Solar Power. Retrieved from
http://energy.gov/eere/energybasics/articles/linear-concentrator-system-basics-concentrating-solar-power
6
7
Reliability of Renewable Energy: Solar
3
FIGURE 1. LINEAR CONCENTRATOR SYSTEM.12
The second type of CSP system is a dish/engine system, as shown in Figure 2. Dish-shaped mirrors concentrate light
onto a power conversion unit. Inside this unit, a fluid-filled thermal receiver is heated to power a small electricitygenerating turbine.13
FIGURE 2. DISH/ENGINE SYSTEM.14
Yokogawa Corporation of America. (n.d.) Example of Trough Technology. Retrieved from at
http://c15181564.r64.cf2.rackcdn.com/image_3294.jpg
13
National Renewable Energy Laboratory. (2013, August 20). Concentrating Solar Power Dish/Engine System Basics. Retrieved from
http://energy.gov/eere/energybasics/articles/concentrating-solar-power-dishengine-system-basics
14
US Department of Energy. (2013, August 20). Concentrating Solar Power Dish/Engine System Basics. Retrieved from
http://energy.gov/eere/energybasics/articles/concentrating-solar-power-dishengine-system-basics
12
Reliability of Renewable Energy: Solar
4
The third type of CSP system is the power tower. A field of large, flat mirrors focus sunlight onto a thermal receiver on
top of a tower. The receiver heats a fluid that is used to boil water. The steam from this water turns electricitygenerating turbines.15
FIGURE 3. POWER TOWER SYSTEM.16
National Renewable Energy Laboratory. (2014, July 25). Concentrating solar power basics. Retrieved from
http://www.nrel.gov/learning/re_csp.html
16
Department of Energy. (1996). Concentrating Solar Tower Plant Illustration. Retrieved from
https://www.eeremultimedia.energy.gov/solar/graphics/concentrating_solar_power_tower_plant_illustration
15
Reliability of Renewable Energy: Solar
5
ECONOMIC RELIABILITY
For solar power to be economically reliable, it must be a financially viable source of energy without government
incentives. Federal and state governments encourage solar energy production through mandates, subsidies, and
financial incentive programs. The cost of funding these incentives is borne by American taxpayers and places a heavier
burden on the lower class through raised energy prices. In many states, electric utilities struggle to keep up with
ambitious renewable energy requirements set by their governments. Solar energy is not yet an economically viable
source of energy because it is expensive, relies heavily on government assistance, and is a burden to American
taxpayers.
THE HIGH COST OF SOLAR
Solar is a more expensive electricity source than traditional alternatives like coal or natural gas. Cost estimates for
electricity production are typically given in the form of a Levelized Cost of Electricity (LCOE), which measures a power
plant’s average costs over its lifetime, including its construction, fuel, operations, maintenance, and efficiency. The
levelized cost of solar power is $125.3 per megawatt-hour for a PV plant and $239.7 per megawatt-hour for solar
thermal plants. In comparison, conventional coal plants cost $95.1 per megawatt-hour, natural gas combined cycle
plants cost $75.2 per megawatt-hour, and advanced nuclear plants cost $95.2 per megawatt-hour.17 Solar power plants
may have zero fuel costs, but their electricity still comes at a high price compared to other electricity sources when
lifetime costs are taken into consideration.
Though LCOEs show that solar is an expensive form of energy, these numbers still underestimate the costs associated
with solar. LCOEs are inaccurate assessments of intermittent energy sources because they do not include the costs of
balancing intermittency. When intermittent power sources are added to a power system, conventional power plants
have to be held on standby so they can be ramped up when an intermittent plant is not generating enough power.
Because the costs of ramping traditional power plants are not included in LCOEs,18 solar and wind power are portrayed
to be more cost-effective than they actually are.
POLICIES AT THE STATE LEVEL
RENEWABLE PORTFOLIO STANDARDS AND SOLAR CARVE OUTS
Even though solar power is expensive, states mandate its adoption. Renewable portfolio standards (RPS) are statebased policies that mandate certain portions of a state’s energy production come from renewable sources. Within these
standards, some states mandate which renewable sources of energy they will use to accomplish their overall RPS goal.
These specifications are called carve outs. New Jersey, for instance, has a carve out mandating that 4.1 percent of its
electricity must come from solar power by 2028.19
Solar is a key feature of many states’ RPS mandates. Out of the 29 states with RPS mandates, 20 have set aside solar
carve outs or provisions for distributed generation.20 Distributed generation refers to energy that is produced near the
U.S. Energy Information Administration. (2015, June 3). Levelized cost and levelized avoided cost of new generation resources in the annual
energy outlook 2015. Retrieved from http://www.eia.gov/forecasts/aeo/electricity_generation.cfm
18
Sun, wind and drain. (2014, July 26). The Economist. Retrieved from http://www.economist.com/news/finance-and-economics/21608646wind-and-solar-power-are-even-more-expensive-commonly-thought-sun-wind-and
19
U.S. Department of Energy. (2015, May 20). Renewable Portfolio Standard. DSIRE. Retrieved from
http://programs.dsireusa.org/system/program/detail/564
20
U.S. Department of Energy. (2015, March). Renewable portfolio standards (RPS) with solar or distributed generation provisions. DSIRE.
17
Reliability of Renewable Energy: Solar
6
place it is consumed. A large portion of distributed generation is produced by small scale PV panels. States’
requirements for distributed generation and solar carve outs vary. North Carolina, for example, requires only 0.2 percent
solar generation by 2018, while Arizona requires 4.5 percent distributed generation by 2025.21
Despite their efforts, many states have been unable to meet their general RPS mandates. According to the Institute for
Energy Research, California’s RPS mandated that by 2010 a full 20 percent of its electricity would be generated through
renewables. By the end of 2009, California was only producing 13 percent of its electricity from renewable sources.22
Similarly, New Jersey called for 6.5 percent of its electricity to be generated by renewable sources by 2009, but
achieved only 1.53 percent renewable generation.23
States that have RPS mandates have seen significant economic damage since RPS implementation. A recent study
analyzed state economies 48 months before and after a state adopted RPS. On average, states that enacted RPS
experienced a 10 percent increase in unemployment, a 14 percent decline in electricity sales, and nearly a 4 percent
drop in the state’s real income.24 RPS mandates may be contributing to these economic downturns by skewing market
incentives for electricity producers, encouraging expensive renewable energies like solar, and increasing electricity
prices.
STATE-BASED SUBSIDIES AND FINANCING FOR SOLAR POWER
Because solar power is an expensive energy source, it is expensive to subsidize. Some states, such as Connecticut and
New Jersey, have had to cut back incentive availability and rebates for solar installers.25 For California to achieve its
mandate of 33 percent renewable energy by 2020, an estimated $115 billion would need to be spent on infrastructure
alone.26
Even when states are able to fund their solar programs, the environmental benefits are minimal, making solar subsidy
money better suited for use in other sectors. A study from the George Washington Institute of Public Policy analyzed
the effects of solar incentive programs in ten states and estimated that existing solar incentive programs would save
6.1 million metric tons of carbon dioxide over a 20 year period.27 This 20 year reduction is less than what two coal
Retrieved from http://ncsolarcen-prod.s3.amazonaws.com/wp-content/uploads/2015/01/RPS-carveout-map1.pdf
21
National Renewable Energy Laboratory. (n.d.) Renewable portfolio standards. Retrieved from
http://www.nrel.gov/tech_deployment/state_local_governments/basics_portfolio_standards.html
22
Institute for Energy Research. (n.d.) The status of renewable electricity mandates in the states. p. 25. Retrieved from
https://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=1&cad=rja&uact=8&ved=0CB4QFjAA&url=http%3A%2F%2Finstitutefor
energyresearch.org%2Fwp-content%2Fuploads%2F2011%2F01%2FIER-RPS-StudyFinal.pdf&ei=l32MVa3mAsTaoATN4azIAg&usg=AFQjCNGiPd81QNVqWxAl2waz0UMzsdpxww&bvm=bv.96782255,d.cGU
23
Institute for Energy Research. (n.d.) The status of renewable electricity mandates in the states. p. 50. Retrieved from
https://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=1&cad=rja&uact=8&ved=0CB4QFjAA&url=http%3A%2F%2Finstitutefor
energyresearch.org%2Fwp-content%2Fuploads%2F2011%2F01%2FIER-RPS-StudyFinal.pdf&ei=l32MVa3mAsTaoATN4azIAg&usg=AFQjCNGiPd81QNVqWxAl2waz0UMzsdpxww&bvm=bv.96782255,d.cGU
24
Simmons, R. T., Brough, T., Sim, K., Fishbeck, J. (2015). Renewable Portfolio Standards: Kansas. The Institute of Political Economy, Utah State
University. Retrieved from: http://www.strata.org/wp-content/uploads/2015/03/Final-Report.pdf
25
Sarzynski, A. (2009, November). The impact of solar incentive programs in ten states. George Washington Institute of Public Policy. p. 34.
Retrieved from http://gwipp.gwu.edu/files/downloads/GWIPP_Impact10.pdf
26
California Public Utilities Commission. (2009, June). 33% renewables portfolio standard implementation analysis preliminary results. p. 4.
Retrieved from http://docs.cpuc.ca.gov/PUBLISHED/GRAPHICS/102354.PDF
27
Sarzynski, A. (2009, November). The impact of solar incentive programs in ten states. George Washington Institute of Public Policy. Retrieved
from http://gwipp.gwu.edu/files/downloads/GWIPP_Impact10.pdf
Reliability of Renewable Energy: Solar
7
power plants emit in a single year. 28 These ten states are spending money that could be put to better uses to
inefficiently reduce carbon emissions.
Studies differ in their claims about how effectively state level incentives increase solar power adoption. A study from
the University of Colorado Boulder estimates that the California Solar Initiative (CSI) and its associated rebates were
directly responsible for 58 percent of all residential and commercial solar panel installations in California between
2007 and 2012.29 Scientists from Vanderbilt University and Sandia National Laboratories, however, came to a different
conclusion after conducting an experiment comparing California’s solar market to a similar market without solar
incentives. Their study found that the program had only a modest impact on solar adoption rates.30 While the studies
disagree about the effectiveness of the CSI in solar adoption rates, they both agree that the CSI generally increases
solar installments. State level incentives can increase solar power adoption, but it is still unclear as to how effectively
they do so.
Not only is it unclear how effective the CSI was in solar adoption, but the emissions benefits gained from the program
are small relative to the program’s costs. The Boulder study estimates that the CSI only reduced carbon dioxide and
nitric oxide emissions by about as much as eliminating one small to mid-sized natural gas power plant.31 Essentially,
California taxpayers have spent $437 million on the CSI to close the equivalent of one natural gas power plant (the
cleanest burning fossil fuel plant) for 20 years. These small environmental benefits do not justify spending such an
exorbitant amount of taxpayer dollars.
NET METERING
Net metering is a state policy that allows residential solar producers to be compensated for surplus power they send
back into the electric grid. Electric utilities are required to purchase electricity generated by residential solar arrays.
Forty-four states, the District of Columbia, and four U.S. territories have established net metering policies. 32 Net
metering benefits those who install residential solar panels, but increases the cost of electricity for regular consumers
and expands costs to utility companies.
Net metering inflicts mechanical stress on the electric grid and incurs other costs that fall disproportionately on
America’s poor. A study conducted by the California Public Utilities Commission estimates that by 2020, costs
associated with net energy metering in California alone would be $1.1 billion.33 Utilities are not allowed by most net
metering laws to charge solar producers for the added grid stress that results from feeding electricity back into the
grid. To compensate for increased costs, utility companies raise electricity prices for everyone. Energy consumers who
To determine this, we used the EPA’s Greenhouse Gas Equivalencies Calculator. We entered the 6,100,000 metric tons of CO2 into the
calculator’s emissions data. The calculator determined that this would be the equivalent of the emissions generated by 1.6 coal-fired power
plants in one year.
United States Environmental Protection Agency. (n.d.) Greenhouse Gas Equivalencies Calculator. Retrieved from:
http://www.epa.gov/cleanenergy/energy-resources/calculator.html#results
29
Hughes, J. E. & Podolefsky, M. (2014, May 6). Getting green with solar subsidies: evidence from the california solar initiative. Retrieved from
http://spot.colorado.edu/~jonathug/Jonathan_E._Hughes/Main_files/PV_Subsidies.pdf
30
Zhang, H., Vorobeychik, Y., Letchford, J., Lakkaraju, K. (2015, May). Data-Driven Agent-Based Modeling, with Application to Rooftop Solar
Adoption. Retrieved from: http://vorobeychik.com/2015/abmsolar.pdf
31
Hughes, J. E. & Podolefsky, M. (2014, May 6). Getting green with solar subsidies: evidence from the California solar initiative. Retrieved from
http://spot.colorado.edu/~jonathug/Jonathan_E._Hughes/Main_files/PV_Subsidies.pdf
32
U.S. Department of Energy. (2015, March). Net Metering. DSIRE. Retrieved from http://ncsolarcen-prod.s3.amazonaws.com/wpcontent/uploads/2015/04/Net-Metering-Policies.pdf
33
Energy and Environmental Economics, Inc. (2013, September 26). California net energy metering (NEM) draft cost-effectiveness evaluation. p.
6. Retrieved from http://www.cpuc.ca.gov/NR/rdonlyres/BD9EAD36-7648-430B-A692-8760FA186861/0/CPUCNEMDraftReport92613.pdf
28
Reliability of Renewable Energy: Solar
8
do not have their own solar panels bear the brunt of these raised prices, even though they do not directly contribute to
the costs associated with net metering.34
INCENTIVES AT THE NATIONAL LEVEL
The United States government subsidizes solar energy in several ways. The Solar Investment Tax Credit allows owners
of residential or commercial solar systems to claim up to 30 percent of the system’s expenditures on their federal taxes.
Since the tax credit was enacted in 2006, solar installations have increased at an average of 76 percent per year.35 The
tax credit increases solar installments, but it also makes solar dependent on government assistance. The Solar Energy
Industries Association expects a 57 percent reduction of installed solar capacity if Congress does not extend the
Investment Tax Credit before it expires at the end of 2016.36
Another federal financial incentive is the 1603 Treasury Program, which uses taxpayer dollars to provide capital to start
renewable energy projects. The 1603 Treasury Program has granted $7.8 billion for solar projects as of January 5,
2015.37
When government support is withdrawn, solar power falters. In 2008, the Spanish national government withdrew much
of its support of solar energy. Since then, more than half of Spain’s photovoltaic companies have declared bankruptcy.38
Solar power’s dependence on government support illustrates its lack of profitability in an unsubsidized market setting.
VERDICT ON ECONOMIC RELIABILITY
Because solar energy is expensive, relies heavily on government assistance, and burdens American taxpayers, it is not
yet an economically reliable source of energy. Federal and state governments have spent billions of taxpayer dollars in
subsidies to encourage solar power’s development and use, but the benefits of doing so have been minimal. States
attempt to increase solar power capacity by implementing RPS, but struggle to meet these mandates even with the
help of subsidies. For these reasons, solar power is not a worthwhile investment of taxpayer dollars.
Tanton, T. (2014, March). Reforming net metering - Providing a bright and equitable future. p. 7-8. Retrieved from http://alec.org/docs/NetMetering-reform-web.pdf
35
Solar Energy Industries Association. (2014). Solar investment tax credit (ITC). Retrieved from http://www.seia.org/policy/finance-tax/solarinvestment-tax-credit
36
Solar Energy Industries Association. (n.d.) Solar industry data. Retrieved from http://www.seia.org/research-resources/solar-industry-data
37
Overview and Status Update of the §1603 Program. (2015, January 8). Retrieved from
http://www.treasury.gov/initiatives/recovery/Documents/STATUS%20OVERVIEW.pdf
38
Gray, A., Clark, P. (2014, July 6). Insurers to cover withdrawal of solar and wind subsidies. The Financial Times. Retrieved from
http://www.ft.com/cms/s/0/badcbca0-0386-11e4-817f-00144feab7de.html#axzz3e7FNKeKt
34
Reliability of Renewable Energy: Solar
9
PHYSICAL RELIABILITY
For solar power to be considered physically reliable, it must consistently meet consumers’ energy demands without
causing detrimental effects to grid operations or infrastructure. Solar energy struggles to meet these criteria relative
to traditional energy sources. Solar power is inconsistent, inefficient, and cannot consistently meet demand. To
mitigate these problems, expensive new transmission infrastructure and grid management techniques would be
needed.
VARIABILITY OF SOLAR ENERGY
EFFICIENCY AND CAPACITY FACTOR
The availability of sunlight is inconsistent, which causes solar power to have a low capacity factor. A capacity factor
is a measurement that compares the amount of energy a plant actually produces to the energy that it would produce if
operating at full capacity for the same amount of time.39
The median capacity factors for various utility-scale electricity sources are approximated as follows:40
•
•
•
•
•
•
•
•
Photovoltaic
Typical onshore wind power
Concentrated solar power
Hydropower
Combined cycle gas plant
Nuclear
Enhanced geothermal system
Large coal plants
20 percent
37 percent
38 percent
45 percent
87 percent
90 percent
90 percent
93 percent
Photovoltaic and concentrated solar power have some of the lowest capacity factors of any major energy source. Their
low capacity factors indicate that solar resources rarely produce near their full capacity.
LOCATION
Solar energy production is more efficient in areas with a high number of sunny days. Efficiency also increases when
sunlight hits the panels more directly. Some solar panels are equipped with a moveable tracking system that allows
them to follow the sun through the day, increasing their efficiency.41 Not all panels are equipped to follow the sun, and
many places experience indirect sunlight for much of the year, making solar panels less efficient.
Comparing southern California and New York illustrates the importance of location in solar energy production.
Sacramento, California averages 188 clear days and 3,608 hours of sunlight per year,42 compared to Buffalo, New York,
which averages 54 clear days and 2,207 hours of sunlight per year.43 A rooftop solar panel system that would produce
Capacity Factor. (n.d.). In U.S. Energy Information Administration Glossary. Retrieved from http://www.eia.gov/tools/glossary/index.cfm?id=C
Open Energy Index. (n.d.) Transparent cost database - LCOE. Retrieved from http://en.openei.org/apps/TCDB/
41
Siemens AG. (n.d.). Solar Panels Track the Sun For More Efficiency. Retrieved from
http://www.siemens.com/innovation/en/news/2011/solar-panels-track-the-sun-for-more-efficiency.htm
42
Osborn, L. (n.d.). Sunniest US Cities. Retrieved December 14, 2014, from http://www.currentresults.com/Weather-Extremes/US/sunniestcities.php
43
Current Results. (n.d.) Average annual sunshine in American cities. Retrieved from http://www.currentresults.com/Weather/US/average39
40
Reliability of Renewable Energy: Solar
10
4,774 kilowatt-hours of electricity a year in Buffalo would produce 6,093 kilowatt-hours a year in Sacramento.44 Solar
plants make far more sense in sunny areas, yet they are incentivized and implemented across the United States.
IMPLICATIONS FOR THE ELECTRIC GRID
WHAT IS THE GRID?
The electric grid includes everything needed to generate and transmit electricity. The American network includes power
plants, transformers, and over 450,000 miles of transmission lines.45 Electricity fed into the grid must be consistently
supplied to users at the rate it is demanded, because energy cannot be effectively stored for later use. Thus, energy
must be generated, transmitted, and used immediately. If too much electricity is supplied, the voltage within the grid
becomes unstable, which strains grid infrastructure. Power plants have to decrease their output and they lose money
as a result. On the other hand, when too little electricity is supplied, restrictions on the availability of electricity, called
brownouts, can occur. 46 Because solar power is intermittent and unpredictable, it makes it more difficult for grid
operators to maintain this delicate balance between electricity supply and demand.
INTERMITTENCY
The U.S. electric grid is designed to transmit electricity from power plants whose output can be controlled by power
grid operators. Solar power is not easily controllable because its fuel source is at the mercy of the weather and cannot
be transported. These characteristics necessitate more complex grid management techniques and new grid
infrastructure.
Accurate solar forecasting is crucial for the efficient use of solar power. Solar power’s variability is more manageable
if power grid operators can anticipate how solar power output is going to change throughout the day. When solar
provides less power than was forecasted, grid operators have to ramp backup power plants. Conversely, when solar
power provides more power than was forecasted, grid operators have to manually reduce power system output. These
practices are costly. To illustrate the importance of accurate forecasting, a study by the NREL on the impact of solar
forecasts estimated that improving solar forecasts by 25 percent would save the New England independent system
operator $46.5 million in generation costs.47 Methods for solar power forecasting include cloud tracking and numerical
weather prediction models, which use current weather data to predict future weather patterns.48
Because solar power output varies across all time scales, both long and short term forecasts are used by system
operators. For example, an independent system operator in California (CAISO) uses day-ahead and hour-ahead
forecasts, and is planning on developing forecasts that predict solar output at 5 minute intervals.49 Solar forecasts will
never be completely accurate, but researchers are working to develop more accurate solar power prediction software.
annual-sunshine-by-city.php
44
National Renewable Energy Laboratory. (n.d.) Solar resource data. Retrieved from http://pvwatts.nrel.gov/pvwatts.php
45
Department of Energy. (2014, November 20). Top 9 things you didn’t know about America’s power grid. Retrieved from
http://www.energy.gov/articles/top-9-things-you-didnt-know-about-americas-power-grid
46
Blume, S. (2007). Electric Power System Basics for the Nonelectrical Professional p. 198-199. Hoboken, New Jersey: John Wiley & Sons, Inc.
Retrieved from http://s1.downloadmienphi.net/file/downloadfile6/192/1385055.pdf
47
National Renewable Energy Laboratory. (September 2014). The Impact of Improved Solar Forecasts on Bulk Power System Operations in ISONE. pg 1. Retrieve from http://www.nrel.gov/docs/fy14osti/62817.pdf
48
Zhang, J., Hodge, B-M., & Florita, A. (May 2013). Investigating the correlation between wind and solar power forecast errors in the Western
Interconnection. p. 2. Retrieved from http://www.nrel.gov/docs/fy13osti/57816.pdf
49
International Energy Agency. (October 2013). Photovoltaic and Solar Forecasting: State of the Art. p. 8. Retrieved from http://ieapvps.org/index.php?id=3&eID=dam_frontend_push&docID=1690
Reliability of Renewable Energy: Solar
11
Connecting solar plants over large areas can mitigate some of solar power’s variability. Weather patterns are more
predictable and stable over larger areas. Aggregating solar plants gives grid operators a larger network of plants from
which to draw power, reducing an area’s dependence on backup power plants. If one solar plant suffers from cloud
cover, another plant may be available to compensate for some loss of power. The United States Department of Energy
states that while aggregating solar would decrease fluctuations in solar power output, there is not yet enough data to
accurately quantify the effect that connecting solar plants would have.50
Aggregating multiple power plants also reduces the need for reserves, regardless of the type of generation. For
example, the Midwest Independent Transmission System Operator, Inc. consolidated 26 balancing authorities, which
are organizations that balance electricity supply and demand within a specific area. This consolidation decreased
reserve capacity needs over the areas covered from 1,200 megawatts to 400 megawatts.51
GRID IMBALANCES
If aggregating multiple solar facilities is not feasible, operating reserves can be called upon to provide power when
solar fails.52 But most traditional power plants are designed to provide a steady baseload of energy and are unequipped
to ramp up and down quickly to compensate for solar power’s variability. Increasing cycling to compensate for
inconsistent solar results in higher operation and maintenance costs for conventional power plants.53
During peak solar hours electricity demand is low, and the combined generation of solar and baseload power plants
can frequently produce more energy than is needed, leading to problems with overgeneration.54 Certain power plants,
called baseload generators, must always be running at a minimum output to meet reliability criteria or to fulfill basic
energy demands. When solar power plants produce too much electricity, grid system operators have to order them to
decrease their output so that electricity supply and demand can be balanced.55 Curtailments and the resulting financial
losses become more common as more solar-generated electricity is integrated into the grid.56
Figure 4 demonstrates the magnitude of solar power’s overgeneration problem. The “Duck Curve” shows the amount
of energy that the traditional power plants of the California Independent System Operator will have to supply on a
typical day in March.57 During the day, when solar plants are most productive, demand for electricity from traditional
power plants plummets. In the evening, the need for traditional power increases due to the combined effect of solar
output decreasing and energy demand increasing. Existing traditional power plants are expected to make up the
difference, but most of these older plants require several hours to ramp up sufficiently. Fossil-fueled plants historically
have been built to provide constant power, and it is difficult for them to meet increased demand on such short notice.58
U.S. Department of Energy. (2011, May.) The Role of Large Balancing Areas in Integrating Solar Generation. Retrieved from
http://www1.eere.energy.gov/solar/pdfs/50059.pdf
51
Ibid.
52
National Renewable Energy Laboratory. (2013, September 24). NREL calculates emissions and costs of power plant cycling necessary for
increased wind and solar in the West. Retrieved from http://energy.gov/eere/articles/energy-department-report-calculates-emissions-andcosts-power-plant-cycling-necessary
53
Ibid.
54
Trabish, H. K. (2014, October 22.) The 'epic fail' on solar's doorstep—and how the grid can help. Retrieved from
http://www.utilitydive.com/news/the-epic-fail-on-solars-doorstepand-how-the-grid-can-help/324411/
55
Howarth, D., Monsen, B. (n.d.) Renewable energy faces daytime curtailment in California. Retrieved from
http://www.nawindpower.com/issues/NAW1412/FEAT_04_Renewable-Energy-Faces-Daytime-Curtailment-In-California.html
56
Trabish, H. K. (2014, October 22.) The 'epic fail' on solar's doorstep—and how the grid can help. Retrieved from
http://www.utilitydive.com/news/the-epic-fail-on-solars-doorstepand-how-the-grid-can-help/324411/
57
Smith, O., Bell, M. (2013, October 29.) Renewables’ bird problem. Retrieved from
http://blog.rmi.org/blog_2013_10_29_renewables_bird_problem
58
Ibid.
50
Reliability of Renewable Energy: Solar
12
As seen in Figure 4, the problem of overgeneration and increased ramping needs are expected to worsen in the coming
years as mandates and incentives for renewable energy continue to increase the use of solar.
FIGURE 4. THE DUCK CURVE SHOWING RAMPING NEEDS AND OVERGENERATION RISK.
59
Solar power’s intermittency makes it a difficult energy source for grid operators to balance with electricity demand.
Aggregating multiple solar plants can help mitigate solar power’s intermittency, but it is expensive to do and not all
solar facilities are close enough to each other for aggregation to be feasible. In other cases, traditional energy sources
can back up solar when the sun is not shining but many of these facilities are not built to handle the ramping
requirements as more solar power is integrated into the grid. No matter the method used, reducing solar power’s
intermittency is costly.
USING ENERGY STORAGE
The peak demand for energy often occurs in the evening when solar power is least productive and cannot reliably meet
demand.60 The inconsistency of solar energy could be alleviated through energy storage, but because traditional fuel
sources can be utilized any time of the day or year, commercial-scale energy storage is uncommon.
California Independent System Operator. (2013.) What the duck curve tells us about managing a green grid. p.3 Retrieved from
http://www.caiso.com/documents/flexibleresourceshelprenewables_fastfacts.pdf
60
U.S. Energy Information Administration. (2011, April 6). Demand for electricity changes throughout the day. Retrieved from
http://www.eia.gov/todayinenergy/detail.cfm?id=830
59
Reliability of Renewable Energy: Solar
13
Different types of energy storage would be needed to accommodate solar energy’s variability at different timescales.61
On short timescales, grid operators would need to utilize low-capacity, fast-response storage. Some fast-response
storage possibilities include batteries, flywheels (which store energy as momentum in spinning disks), and high-energy
capacitors (which store energy in the form of an electrostatic field between its two conducting plates). 62 For
unpredictable weather patterns that occur on long timescales, high-capacity and slower-response storage would be
needed. Slower-response storage possibilities include pumped hydroelectric storage and compressed air energy
storage.63
Because it is uncommon, regulatory uncertainty surrounds grid-level energy storage. Utility companies hesitate to
invest in energy storage because it is difficult to estimate how the government will regulate energy storage projects
and how those regulations will affect profits.64 In 2013, the California Public Utilities Commission approved a mandate
requiring 1.3 gigawatts of energy storage to be added to the grid by 2020.65 In an effort to reach this goal, one utility
company, Southern California Edison, has invested $50 million to develop 8 megawatts of power storage with lithiumion batteries.66 Southern California Edison has warned that California’s energy storage mandate "could cost up to $3
billion with uncertain net benefits for customers."67
NET METERING
When private owners of small scale solar systems produce more power than they can use, their surplus power is fed
back into the grid and purchased by electricity utilities. Because the grid was designed for one-directional flow rather
than two-directional flow, accepting electricity from consumers places undue stress on the grid.68 In Hawaii, where
solar power installations have experienced rapid growth, subsidies for rooftop solar had to be cut in half when
residential solar production began destabilizing the power grid. Solar power’s intermittency caused fluctuation in grid
power supply that made areas vulnerable to blackouts.69 Additionally, officials at the California Independent System
Operator say renewable energy producers make management of the California grid more complex. Bob Foster, mayor
of Long Beach and a member of the system operator board, said, "We are getting to the point where we will have to
pay people not to produce power."70
American Physical Society. Integrating renewable electricity on the grid. p.16. Retrieved from http://www.aps.org/policy/reports/popareports/upload/integratingelec.pdf
62
U.S. Energy Information Administration. (2011, December 14.) Electricity storage technologies can be used for energy management and power
quality. Retrieved from http://www.eia.gov/todayinenergy/detail.cfm?id=4310
63
Ibid.
64
American Physical Society. Integrating renewable electricity on the grid. p.19. Retrieved from http://www.aps.org/policy/reports/popareports/upload/integratingelec.pdf
65
St. John, J. (2013, October 27.) California passes huge grid energy storage mandate. Retrieved from
http://www.greentechmedia.com/articles/read/california-passes-huge-grid-energy-storage-mandate
66
Macgill, Bobby. (2015, January 15). California Takes Lead in Developing Energy Storage. Discovery News. Retrieved from
http://news.discovery.com/earth/california-takes-lead-in-developing-energy-storage-150115.htm
67
Halper, E. (2013, December 2.) Power struggle: Green energy versus a grid that's not ready. Los Angeles Times. Retrieved from
http://articles.latimes.com/2013/dec/02/nation/la-na-grid-renewables-20131203#axzz2mXIfGQrx
68
Ferber, D. (2013, March 5). Can the grid handle distributed renewable energy? Retrieved from:
http://midwestenergynews.com/2013/03/05/can-the-grid-handle-distributed-renewable-energy/
69
Carducci, A. (2013, January 11.) Hawaii Cuts Back on Solar Power Subsidies. Retrieved from http://news.heartland.org/newspaperarticle/2013/01/11/hawaii-cuts-back-solar-power-subsidies
70
Halper, E. (2013, December 2.) Power struggle: Green energy versus a grid that's not ready. Los Angeles Times. Retrieved from
http://articles.latimes.com/2013/dec/02/nation/la-na-grid-renewables-20131203#axzz2mXIfGQrx
61
Reliability of Renewable Energy: Solar
14
THE NEED FOR LONG-DISTANCE TRANSMISSION
The U.S. electric grid was designed to supply power at the local and regional level. But, with the exception of Southern
California, the areas with the greatest solar potential are located far from densely populated areas on the coasts. Figure
5 displays the availability of solar energy in the United States.
FIGURE 5. PHOTOVOLTAIC SOLAR RESOURCES OF THE UNITED STATES.71
Because solar power plants are generally located far from population centers, they necessitate the construction of
long-distance transmission lines. A study by GE Energy concluded that integrating 30 percent wind and solar power
would cost $13.7 billion in transmission costs for the PJM Interconnection, a large transmission system that brings
power to 13 eastern states and the District of Columbia.72 Similarly, in 2009 the California Public Utilities Commission
estimated that meeting the state’s 2010 and 2020 renewable energy requirements would cost $16 billion in
transmission infrastructure alone.73
National Renewable Energy Laboratory. (2013, September 3.) Solar maps. Retrieved from http://www.nrel.gov/gis/solar.html
PJM Interconnection. (2014, February 14.) Executive summary of renewable integration study for PJM. Retrieved from
http://www.google.com/url?q=http%3A%2F%2Fwww.pjm.com%2F~%2Fmedia%2Fcommitteesgroups%2Fcommittees%2Fmic%2F20140303%2F20140303-pris-pjm-coverletter.ashx&sa=D&sntz=1&usg=AFQjCNE5f_6bzHY2fBbqIFcTt4yDzKYfkw
73
California Public Utilities Commission. (June 2009). 33% Percent Renewables Portfolio Standard Implementation Analysis Preliminary
Results. Retrieved from http://docs.cpuc.ca.gov/PUBLISHED/GRAPHICS/102354.PDF
71
72
Reliability of Renewable Energy: Solar
15
Despite these high costs, in recent years levels of investment in electricity transmission have reached record highs.74
Part of this growth is attributed to efforts to connect remote sources of wind and solar power to the grid.75 A highvoltage transmission project called SunZia, for example, will span 515-miles and cost $2.2 billion. The SunZia line is
just one of several transmission projects being developed to move wind and solar power through Arizona, Colorado,
New Mexico, and Utah. Together these projects will cost over $6 billion to build, in addition to the $20 billion needed
to build the renewable power plants. Developers count on these projects becoming more economically feasible in the
future as new federal carbon regulations are passed. Developers also predict that more aggressive RPS in western
states will lead to an increased demand for renewable energy and long distance transmission.76
TECHNICAL CHALLENGES OF LONG-DISTANCE TRANSMISSION
Because remotely-located energy sources require long-distance transmission, scientists are looking for ways to improve
long-distance transmission capabilities. Currently, electricity is transmitted as alternating current (AC). Physicists at
the American Physical Society suggest using direct current (DC) for long-distance transmission to reduce electricity
loss.77
Since electricity is generated and used as AC, power would have to be converted from AC to DC for transmission and
then back to AC for consumers. The process of long-distance DC transmission and conversion between AC and DC
could result in electrical losses of up to ten percent. To minimize these losses, the voltage can be increased. Such high
voltages, however, make it more difficult for semiconductors to convert electricity between AC and DC, which drives
up the cost of transmission. Long-distance DC transmission will raise costs because it will require the construction of
semiconductors that convert electricity between AC and DC and new high voltage DC transmission infrastructure.78
While utilizing DC would make long-distance transmission more efficient and feasible, it would do so at a high cost.
VERDICT ON PHYSICAL RELIABILITY
Because solar power is intermittent and inefficient, it increases the need for backup power plants. Solar power is also
commonly generated in remote locations, far from high electricity demand. Making solar power reliable would require
expensive investments in grid-level energy storage and transmission infrastructure. The current costs of making solar
power physically reliable outweigh its limited benefits.
Edison Electric Institute. (2015, January 8). Actual and Planned Transmission Investment By Shareholder-Owned Utilities (2008–2017).
Retrieved from http://www.eei.org/issuesandpolicy/transmission/documents/bar_transmission_investment.pdf
75
U.S. Energy and Information Administration (2014, August 26) Investment in electricity transmission infrastructure shows steady increase.
Retrieved from http://www.eia.gov/todayinenergy/detail.cfm?id=17711
76
Robinson-Avila, K. (2015, June 21). SunZia’s $2B dream still a gamble. Albuquerque Journal. Retrieved from
http://www.abqjournal.com/601834/news/sunzias-2b-dream-still-a-gamble.html
77
American Physical Society. (2010). Integrating Renewable Electricity on the Grid: A Report by the APS Panel on Public Affairs. Retrieved from
http://www.aps.org/policy/reports/popa-reports/upload/integratingelec.pdf
78
American Physical Society. (2010). Integrating Renewable Electricity on the Grid: A Report by the APS Panel on Public Affairs. p. 22-23.
Retrieved from http://www.aps.org/policy/reports/popa-reports/upload/integratingelec.pdf
74
Reliability of Renewable Energy: Solar
16
ENVIRONMENTAL RELIABILITY
An alternative energy source must have fewer environmental impacts than traditional fossil fuels to be considered
environmentally reliable. According to this definition, solar power is environmentally reliable, but this report also finds
that solar power’s edge over fossil fuels is not as pronounced when all environmental costs are considered. Although
solar power does not emit greenhouse gases during electrical production, its environmental benefits are diminished by
its water usage in arid regions, its need for fossil fuel backup reserves, the pollution caused by the PV panel
manufacturing process, and its impact on wildlife populations.
WATER
Solar power plants utilize water for cooling and cleaning purposes. The construction and maintenance of solar facilities
also require large volumes of water. The construction of utility-scale PV projects requires nearly 400 million gallons of
water. Maintenance tasks, such as washing dust from the panels, require an additional 7 million gallons of water each
year.79 Overall, PV plants have an estimated lifetime water consumption rate of 520 gallons per megawatt-hour for
typical crystalline silicon panels.80 According to a study done by the International Energy Agency, the water withdrawal
and consumption rates of PV plants are below those of coal, natural gas, and nuclear plants.81
CSP plants, however, commonly use more water than PV plants. The biggest water consumption in CSP plants occurs
when steam exiting the turbines is cooled. Wet-cooling technology is the most commonly found cooling system in CSP
plants. CSP plants that use wet-circulation cooling systems use an estimated 1,240 gallons of water per megawatthour, but dry-cooling systems are gaining popularity to limit water consumption.82
WET-CIRCULATION VS DRY-COOLING
In wet-circulation systems, the heated water is spread out over a large surface area and exposed to cooler water. As
the heated water cools, a small portion of the water is lost through evaporation while the remainder is reused.83
Although wet-cooling is used in coal, nuclear, and natural gas plants, CSP power plants with wet-circulation cooling
systems require more water per unit of electricity generated than traditional fossil fuel facilities using the same
technologies. 84 Unfortunately, solar plants are most often constructed in areas with high temperatures, high sun
exposure, and most importantly, scarce water supplies. CSP plants compete for water with agricultural users, local
municipalities, and wildlife.
Mulvaney, D. (2014, August 26). Solar energy isn’t always as green as you think. Retrieved from http://spectrum.ieee.org/greentech/solar/solar-energy-isnt-always-as-green-as-you-think
We converted the numbers given in liters to gallons by multiplying the number of liters by 0.264172.
80
Keith, G., Jackson, S., Napoleon, A., Comings, T., Ramey, J. A. (2012, September 19). The hidden costs of electricity. 62. Prepared for The
Civil Society Institute. Retrieved from
http://www.civilsocietyinstitute.org/media/pdfs/091912%20Hidden%20Costs%20of%20Electricity%20report%20FINAL2.pdf
81
International Energy Agency. (2012). Water for energy - Is energy becoming a thirstier resource? p. 10. Retrieved from
http://www.iea.org/media/weowebsite/2012/WEO_2012_Water_Excerpt.pdf
82
Keith, G., Jackson, S., Napoleon, A., Comings, T., Ramey, J. A. (2012, September 19).The hidden costs of electricity. p. 62. Prepared for The
Civil Society Institute. Retrieved from
http://www.civilsocietyinstitute.org/media/pdfs/091912%20Hidden%20Costs%20of%20Electricity%20report%20FINAL2.pdf
83
Union of Concerned Scientists. (2013, March 5). Environmental impacts of solar power. Retrieved from
http://www.ucsusa.org/clean_energy/our-energy-choices/renewable-energy/environmental-impacts-solar-power.html#.VLBdD2TF-mm
84
Carter, N. T., Campbell, R. J. (2009, June 8). Water issues of concentrating solar power (CSP) electricity in the U.S. southwest. Prepared for
Congressional Research Service. Retrieved from http://www.circleofblue.org/waternews/wp-content/uploads/2010/08/Solar-Water-UseIssues-in-Southwest.pdf
79
Reliability of Renewable Energy: Solar
17
In efforts to reduce the stress on local water supplies, developers in Idaho, Arizona, California, and Nevada have been
driven to use dry-cooling systems.85 Rather than relying on water to cool the steam exiting turbines, dry-cooling systems
expose the steam to the cooler outside air to condense the steam. Dry-cooling systems can decrease power plant water
consumption by around 90 percent.86 Solar power, however, is already intermittent and expensive, and switching to dry
cooling results in a 7 percent drop in electricity production and a 10 percent increase in capital costs.87
The drop in electricity production and increased costs are further exacerbated by the hot and arid locations that most
CSP plants tends to be built in. Dry-cooling systems require a significant difference between the temperature of the
exhaust steam and the outside air to condense steam back into water, and, as a result, dry-cooling technology is much
less effective in locations with temperatures consistently above 100 degrees Fahrenheit.88 This means that CSP plants
in the hot and arid southwest will run even less efficiently using dry-cooling systems. Water usage is greatly decreased,
but less power is produced than normal, making solar power even less physically reliable.
EMISSIONS
When solar energy is integrated into a power system, grid operators cycle conventional power plants to compensate
for decreases in solar power output. Cycling conventional power plants increases the plant’s emissions per unit of
electricity produced, negating some of solar power’s environmental benefits.89 A 2013 study completed by the National
Renewable Energy Laboratory (NREL), however, concluded that the added carbon emissions caused specifically by
cycling are "negligible" when compared to the carbon reductions from using wind and solar.90
Solar power has emission costs beyond those caused by cycling. Manufacturing, transportation of materials,
installation and construction, maintenance, and the decommissioning of solar-power facilities also contribute to solar
power’s net carbon footprint. These emissions all contribute to the life cycle emissions of solar, which is an assessment
of the total carbon emissions produced over a solar plant’s life.91
Figure 6 shows the results from an NREL study comparing the life cycle greenhouse gas emissions of various energy
sources. Other sources of energy emit more greenhouse gases over their lifetime compared to solar energy.
Union of Concerned Scientists. (2011, November). Freshwater use by US power plants. 2. Retrieved from
http://www.ucsusa.org/sites/default/files/attach/2014/08/ew3-freshwater-use-by-us-power-plants-exec-sum.pdf
86
Union of Concerned Scientists. (2013, March 5). Environmental impacts of solar power. Retrieved from
http://www.ucsusa.org/clean_energy/our-energy-choices/renewable-energy/environmental-impacts-solar-power.html#.VLBdD2TF-mm
87
International Renewable Energy Agency. (2013, January). Concentrating solar power. 12. Retrieved from
http://www.irena.org/DocumentDownloads/Publications/IRENA-ETSAP%20Tech%20Brief%20E10%20Concentrating%20Solar%20Power.pdf
88
Union of Concerned Scientists. (n.d.) Environmental impacts of solar power. Retrieved from http://www.ucsusa.org/clean_energy/our-energychoices/renewable-energy/environmental-impacts-solar-power.html#.VcJ2XBNVhBc
89
National Renewable Energy Laboratory. (n.d.) Impacts on conventional generators. Retrieved from
http://www.nrel.gov/analysis/key_activities_integ_impacts.html
90
National Renewable Energy Laboratory. (2013, September 24). NREL calculates emissions and costs of power plant cycling necessary for
increased wind and solar in the West. Retrieved from http://www1.eere.energy.gov/wind/pdfs/55588.pdf
91
Union of Concerned Scientists. (2013, March 5). Environmental impacts of solar power. Retrieved January 5, 2015, from
http://www.ucsusa.org/clean_energy/our-energy-choices/renewable-energy/environmental-impacts-solar-power.html#.VLBdD2TF-mm
85
Reliability of Renewable Energy: Solar
18
FIGURE 6. LIFE CYCLE GREENHOUSE GAS EMISSIONS FOR VARIOUS ENERGY SOURCES.92
Although the emissions from cycling and other parts of a solar panel’s life negate some of its environmental benefits,
solar power plants have significantly fewer emissions over their lifetime than conventional power plants.
MANUFACTURING, RECYCLING, AND FOREIGN POLLUTION
Potentially harmful substances such as silicon tetrachloride, hydrochloric acid, and hydrofluoric acid are used in the
production of solar panels.93 When waste products from solar panel manufacturing are improperly disposed of, they
may harm human health and contaminate the environment. Facilities in China have caused health problems for
residents by dumping chemical wastes used to manufacture solar panels in rivers and fields near their facilities. Local
residents have experienced inflamed eyes and throats, and polluted waterways have killed fish and livestock. The soil
of these areas has also been poisoned, making future agriculture difficult.94
China is currently the world’s leader in PV panel manufacturing, accounting for over 60 percent of global production.95
Chinese manufacturing, per panel produced, has a carbon footprint that is twice as large as Europe’s solar panel
manufacturing process. 96 95 percent of Chinese panels are exported to other countries, but China is left with the
pollution.97 Europe, Japan, and the United States continue to claim solar power is environmentally friendly, but these
countries do not pay the full environmental costs of the manufacturing process.
National Renewable Energy Laboratory. (2014, July 21). Life cycle assessment harmonization results and findings. Retrieved from
http://www.nrel.gov/analysis/sustain_lca_results.html
93
Galland, A. (2012). Clean & green: Best practices in photovoltaics. 21. Retrieved from http://www.clca.columbia.edu/Clean&GreenPhotovoltaics.pdf
94
Mulvaney, D. (2014, August 26). Solar energy isn’t always as green as you think. Retrieved from http://spectrum.ieee.org/greentech/solar/solar-energy-isnt-always-as-green-as-you-think
95
Ramzy, A. (2014, June 2). China's Solar Panel Production Comes at a Dirty Cost. Retrieved from
http://sinosphere.blogs.nytimes.com/2014/06/02/chinas-solar-panel-production-comes-at-a-dirty-cost/
96
Lerner, L. (2014, May 29). Solar panel manufacturing is greener in Europe than China, study says. Retrieved from
http://www.anl.gov/articles/solar-panel-manufacturing-greener-europe-china-study-says
97
Worldwatch Institute. (November 2012). India’s National Solar Mission: A Market Analysis of Phase 1. Retrieved from
http://www.worldwatch.org/system/files/WW%20Research%20Note%20India%20Solar%20Market%20Analysis%20Phase%201_FINAL_0.p
df
92
Reliability of Renewable Energy: Solar
19
At the end of a solar panel's life cycle, it can be recycled into a product almost as efficient as new solar panels. The
recycling process reduces the environmental burden of the demand for new materials.98 Solar panel recycling is limited,
however, because there are not yet enough obsolete solar panels to make recycling economically viable. 99 Until
recycling solar panels becomes economically viable, expanding the solar industry will continue to result in Chinese
manufacturing and its associated environmental harms.
WILDLIFEIMPACTS
CSP and PV plants infringe on wildlife habitat and harm or displace threatened species because of the large amount of
undeveloped land they require. The Topaz Solar Farm, located in the Carrizo Plain in California, occupies the habitats
of numerous protected species, including the San Joaquin kit fox, the golden eagle, and the giant kangaroo rat. The
Topaz solar plant’s project developers have negotiated with the United States Fish and Wildlife Service to develop a
conservation plan that minimizes the impacts of the Topaz solar plant on these wildlife populations.100 The Ivanpah
Solar Farm, located in the Mojave desert, has displaced 144 desert tortoises. The desert tortoise is on the threatened
species list and is the state reptile of Nevada and California.101 BrightSource Energy, the developer of the Ivanpah Solar
Farm, has had to spend over $56 million capturing the displaced tortoises and reintroducing them safely into the wild.102
In CSP tower systems, the concentrated heat and large cooling towers can affect birds as they fly through the solar
plants. When birds see the reflective surfaces of a solar plant they often confuse them for a body of water and fly
towards them.103 Jeff Holland, a representative of Ivanpah, officially reported 321 bird or bat fatalities over a 6-month
period, many of which were caused by impacts with solar towers or singeing from concentrated heat.104 233 Yuma
clapper rails, an endangered bird, have been found on three other solar plants in the California desert. Because this
species is endangered, concerned conservation groups have threatened to sue the federal government if government
agencies do not more fully evaluate future solar plants’ potential bird impacts.105
Efforts by the EPA and California lawmakers may decrease these wildlife impacts. The EPA has recently identified at
least 80,000 abandoned mining sites and other contaminated lands that can be used for the construction of future
renewable energy plants.106 The EPA provides information and technical support for those who are trying to reuse these
abandoned mining sites.107
Bine Informationsdienst. (n.d.) Recycling photovoltaic modules. Retrieved from
http://www.bine.info/fileadmin/content/Publikationen/Englische_Infos/projekt_0210_engl_internetx.pdf
99
Nunez, C. (2014, November 11). How Green Are Those Solar Panels, Really?. National Geographic. Retreived from
http://news.nationalgeographic.com/news/energy/2014/11/141111-solar-panel-manufacturing-sustainability-ranking/
100
Moler, Robert. (14, May 2015) Wildlife and Creating Renewable Energy on the Carizzo Plain. Sacramento Fish and Wildlife Office. Retrieved
from http://www.fws.gov/sacramento/outreach/Featured-Stories/RenewableEnergy-CarrizoPlain/RenewableEnergy-CarrizoPlain.htm
101
U.S. Fish and Wildlife Service. Desert tortoise (Gopherus agassizii). Retrieved from
http://ecos.fws.gov/speciesProfile/profile/speciesProfile?spcode=C04L
102
Wells, K. (2012, October 10). Where Tortoises and Solar Power Don't Mix. Retrieved from http://www.bloomberg.com/bw/articles/2012-1004/where-tortoises-and-solar-power-dont-mix
103
Uptown, John. (27, August 2014). Solar Farms Threaten Birds. Scientific American. Retrived from
http://www.scientificamerican.com/article/solar-farms-threaten-birds/
104
Kraemer, S. (2014, September 3). For the Birds: How Speculation Trumped Fact at Ivanpah. Retrieved from
http://www.renewableenergyworld.com/rea/news/article/2014/09/for-the-birds-how-speculation-trumped-fact-at-ivanpah
105
Uptown, John. (27, August 2014). Solar Farms Threaten Birds. Scientific American. Retrived from
http://www.scientificamerican.com/article/solar-farms-threaten-birds/
106
Environmental Protection Agency. (2011, December 1). Shining Light on a Bright Opportunity. p. 11. Retrieved from
http://www.epa.gov/aml/revital/amlsolarfact.pdf
107
Page, Samantha. (28, April 2015). California Wants To Make it Easier to Cover Old Mines With Renewable Energy. ThinkProgress. Retrived
from http://thinkprogress.org/climate/2015/04/28/3652072/californias-mines-are-going-solar/
98
Reliability of Renewable Energy: Solar
20
Furthermore, a California bill was passed in April of 2015 which allows solar and wind projects that are built on mining
sites to forego the expensive and time-consuming environmental reviews that solar and wind projects usually require.
The bill’s author expects that the bill will encourage more solar projects to be built on already-used land rather than
pristine desert.108
VERDICT ON ENVIRONMENTAL RELIABILITY
Governments and individuals pursue solar power because they view it as an environmentally friendly electricity source.
Solar power does reduce greenhouse gas emissions, but it still relies heavily on fossil fuels for backup power. Solar
plants are usually built in deserts where increased water usage strains local water supply. Because solar panel
producers rely heavily on Chinese manufacturing, China bears the brunt of solar pollution. Utility scale solar plants
require large areas, negatively impacting local wildlife and their habitats. Solar has environmental benefits, but its
hidden environmental costs make it a less environmentally reliable energy source than most people believe.
108
Ibid.
Reliability of Renewable Energy: Solar
21
CASE STUDY: SOLAR ENERGY IN GERMANY
In Germany, a government program and social movement called the Energiewende (roughly translated as “energy
revolution”) pushes German electricity consumers toward reliance on solar generation. The Energiewende began in the
1970s as a movement against nuclear energy and was strengthened by both the Chernobyl accident in 1986 and the
Fukushima earthquake in 2011. Today, the Energiewende is a government movement to boost renewable energy
sources, reduce dependence on neighboring countries for fossil fuels, and move away from the perceived threat of
nuclear energy. The German government also asserts that solar energy and other renewable energy sources will
improve local economies.109 Now, many people view Germany as the international standard of solar energy production.
Germany's intensive solar incentives have boosted its solar industry more quickly than other countries, but this boom
has proven to be unreliable and economically unstable. What appears to be a simple story of implementing an
environmentally friendly energy source is more complex than it appears.
EXAGGERATED CLAIMS OF GERMAN SOLAR POWER
On the afternoon of June 9, 2014, German solar energy plants produced 23.1 gigawatts of energy between 1:00 and
2:00 pm, which amounted to 50.6 percent of the country’s energy demand for that time.110 But overall, solar electricity
met only 20.9 percent of that day’s total electricity demand.111 Furthermore, because that day was a national holiday,
offices and factories were closed, making electricity demand unusually low. And so, what might have been an average
output of solar power broke a record for solar energy production.112
Solar power did produce a significant amount of electricity in the summer, but solar power performed less admirably
the rest of the year. On January 18, 2014, Germany produced only 0.1 percent of that day’s electricity demand from
solar power. 113 These examples illustrate how solar power advocates can exaggerate solar power's success by
handpicking their facts. The big picture shows a less attractive side of solar.
ECONOMIC RELIABILITY
Solar power’s costs are heavier than most people think. Estimates show that German taxpayers paid $23 billion for
solar energy that has a market value of less than $4 billion. On Germany’s solar investment, Colin Vance, from the
German economic research institute RWI, said, “The least competitive renewable energy is getting the most support,”
he said. “There is a certain insanity to it, yes.”114
From 1998 to 2015, Germany’s residential electricity prices rose by about 50 percent. In 2013, German electricity cost
around 29 cents per kilowatt-hour.115 For comparison, residential electricity in the United States in May, 2015 costs
Heinrich Böll Foundation. (n.d.). Why the Energiewende. Retrieved from http://energytransition.de/
Luntz, S. (2014, June 14.) Germany now produces half of its energy using solar. Retrieved from
http://www.iflscience.com/technology/germany-now-produces-half-its-energy-using-solar
111
Wilson, R. (2014, August 8). Reality check: Germany does not get half of its energy from solar panels. Retrieved from
http://theenergycollective.com/robertwilson190/456961/reality-check-germany-does-not-get-half-its-energy-solar
112
Luntz, S. (2014, June 14.) Germany now produces half of its energy using solar. Retrieved from
http://www.iflscience.com/technology/germany-now-produces-half-its-energy-using-solar
113
Wilson, R. (2014, August 8). Reality check: Germany does not get half of its energy from solar panels. Retrieved from
http://theenergycollective.com/robertwilson190/456961/reality-check-germany-does-not-get-half-its-energy-solar
114
McGrath, M. (2013, July 9). Can Germany its ‘energy bender’ shift to green power? BBC News. Retrieved from
http://www.bbc.com/news/science-environment-23127175
115
Weiss, J. (2014, July). Solar Energy Support in Germany: A Closer Look. SEIA. Retrieved from: http://www.seia.org/researchresources/solar-energy-support-germany-closer-look
109
110
Reliability of Renewable Energy: Solar
22
about 13 cents per kilowatt-hour.116 High retail electricity costs in Germany are due in part to investments in renewable
energy like solar.117
In recent years, Germany has been phasing out solar subsidies that it cannot afford to sustain. In 2012, the German
Environmental Minister conceded that while solar energy is a desired goal for Germany’s energy portfolio, “the cost
factor has to be at acceptable levels.”118 Germany’s solar subsidies have incentivized solar power installations, but at
an unsustainably high cost.
The German government is not alone in paying large sums of money on behalf of solar power. Because solar power is
intermittent, traditional electricity producers have had to make substantial changes to their plants to handle the
fluctuating electricity demands. RWE, a German electricity company, has invested 700 million Euros (833 million 2015
U.S. dollars) to adapt their lignite (soft coal) plants to the changing energy demands.119 Ulrich Hartmann, executive vice
president of RWE, said, “Back in the days, our lignite plants were inflexible, produced power around the clock and were
always earning money. Now they are as flexible as gas plants.”120
Solar power has proven to be an expensive form of energy for the German government and energy companies. The
fiscal issues surrounding German solar subsidies and high energy prices compound to create a dismal outlook for the
German solar market.
PHYSICAL RELIABILITY
Solar energy production in Germany is illogical because of the country's low solar resources. Figure 7 shows solar
potential in the United States compared to Spain and Germany.
U.S. Energy Information Administration. (2015, July 27). Electric power monthly. Retrieved from
http://www.eia.gov/electricity/monthly/epm_table_grapher.cfm?t=epmt_5_6_a
117
Weiss, J. (2014, July). Solar Energy Support in Germany: A Closer Look. SEIA. Retrieved from: http://www.seia.org/researchresources/solar-energy-support-germany-closer-look
118
Connolley, Kate. (2, March 2012). Germany to cut solar power subsidies. The Guardian. Retrieved from
http://www.theguardian.com/world/2012/mar/02/germany-cuts-solar-power-subsidies
119
Mengewein, J. (2014, July 30). German Utilities Bail Out Electric Grid at Wind's Mercy. Retrieved from
http://www.bloomberg.com/news/articles/2014-07-24/german-utilities-bail-out-electric-grid-at-wind-s-mercy
120
Ibid.
116
Reliability of Renewable Energy: Solar
23
FIGURE 7. SOLAR RESOURCES IN THE UNITED STATES, SPAIN, AND GERMANY.121
The irony is blatant–solar energy potential in Germany is comparable to solar potential in Alaska, yet solar energy was
and still is heavily incentivized by the German government. The German government has managed to achieve high solar
penetration in Germany by incentivizing household PV systems, which are less expensive than CSP plants for both utility
companies and the government.122
ENVIRONMENTAL RELIABILITY
One of the reasons Germany has focused on building up its renewable energy portfolio is to lessen its dependency on
neighboring countries for fossil fuels. But solar installations do not eliminate the need for fossil fuels because solar
power must be backed up by other energy sources, which are often fossil fuels.123
Roberts, B. J. (2009, November 23). Photovoltaic solar resource: The United States of America, Spain and Germany. National Renewable
Energy Laboratory. Retrieved from http://www.gosolarsantafe.com/solar-radiation-map
122
Wirth, H. (2015, May 19). Recent facts about photovoltaics in Germany. Fraunhofer Institute for Solar Energy Systems. p. 33. Retrieved from
http://www.ise.fraunhofer.de/en/publications/veroeffentlichungen-pdf-dateien-en/studien-und-konzeptpapiere/recent-facts-aboutphotovoltaics-in-germany.pdf
123
Energy Transition: The German Energiewende. (2015, February 19). How is Germany integrating and balancing renewable energy today?
121
Reliability of Renewable Energy: Solar
24
From 1990 to 2012, Germany has reduced its emissions by 24.7 percent. 124 Germany’s emissions from electricity
production contribute to a combined emissions cap that the entire European Union is supposed to stay under.125 So,
while Germany might be limiting their emissions, this allows countries like Portugal and Greece to produce more energy
with much cheaper coal. Despite the vast amounts of money and labor Germany has spent in efforts to reduce
emissions, there is no net change in emissions for the European Union as a whole.126
Countries pursue renewable sources of energy to reduce greenhouse gas emissions and environmental impacts.
Unfortunately, even with the money Germany has invested in solar energy, the environment is only marginally cleaner,
if at all. In its entirety, Germany’s solar-energy production will cut carbon dioxide emissions in Germany by only one
percent over the next 20 years – in other words, as explained by Bjørn Lomborg, director of the Copenhagen Consensus
Center, “By the end of the century, Germany’s $130 billion solar panel subsidies will have postponed temperature
increases by 23 hours.”127
GERMAN SOLAR POWER ANALYSIS
Other countries extol Germany's successes with solar power, but upon closer inspection, Germany’s solar progress is
less spectacular than it initially appears. Germany has invested billions of dollars in solar energy over several decades,
but its solar subsidies were unsustainable and have neither decreased emissions nor made Germany independent of
other countries for fossil fuels. Germany’s solar experience reveals that solar power’s limited benefits do not outweigh
its prohibitively high costs.
Retrieved from: http://energytransition.de/2015/02/how-germany-integrates-renewable-energy/
124
Federal Ministry for the Environment, Nature Conservation, Building and Nuclear Safety. (2014, January 16.) Hendricks strives for more
ambitious climate targets. [Press Release]. Retrieved from http://www.bmub.bund.de/en/press/press-releases/detailansichten/artikel/hendricks-beim-klimaschutz-ehrgeiziger-werden/?tx_ttnews%5BbackPid%5D=114
125
European Commission. (2015, July 15). The EU Emissions Trading System (EU ETS). Retrieved from:
http://ec.europa.eu/clima/policies/ets/index_en.htm
126
Lomborg, B. (2012, February 18). Goodnight sunshine. Slate. Retrieved from
http://www.slate.com/articles/news_and_politics/project_syndicate/2012/02/why_germany_is_phasing_out_its_solar_power_subsidies_.ht
ml
127
Lomborg, B. (2012, February 18). Goodnight sunshine. Slate. Retrieved from
http://www.slate.com/articles/news_and_politics/project_syndicate/2012/02/why_germany_is_phasing_out_its_solar_power_subsidies_.ht
ml
Reliability of Renewable Energy: Solar
25
CONCLUSION
Solar power remains an expensive form of energy generation compared to fossil fuels, requiring extensive state and
federal subsidies to incentivize its use. States also mandate the use of solar power through renewable portfolio
standards, but have had difficulty attaining those standards even after spending billions of dollars incentivizing and
integrating renewable energy. Because the solar industry is dependent on these mandates and subsidies, it is an an
economically unreliable energy source. For how little emission benefits solar power has provided, it is not a worthwhile
investment of taxpayer dollars.
Solar energy is physically unreliable because it is inconsistent and inefficient. The sun is not always shining, so solar
plants cannot always produce power. As a result, utilizing solar energy is an inefficient way to produce electricity and
is dependent on more reliable energy sources like coal and natural gas for backup power.
Because solar power is intermittent and remotely located, our current grid infrastructure is ill-equipped to integrate
significant amounts of solar power into the United States power system. Even rooftop solar causes energy congestion
problems and complicates the management of electric grids. Improved solar forecasting, grid-level energy storage, the
aggregation of multiple solar plants, and new transmission lines may make solar power more physically reliable in the
future, but utilizing these technologies would cost billions of dollars and it is difficult to evaluate the costs and benefits
of incorporating them.
Solar power does reduce carbon emissions, and is overall less harmful to the environment than traditional fossil fuels.
One of solar power’s biggest environmental drawbacks, however, is its need for water in arid regions. Solar plants can
use cooling systems that use less water, but they produce less electricity and pay higher capital costs when these
systems are utilized. Another drawback of solar power is that the primary manufacturer of solar panels is China, where
manufacturing companies have been known to harm residents and ecosystems through their disposal of toxic
chemicals.
Germany has spent billions of dollars on solar, but the country's implementation of solar power has had many negative
side effects, such as fiscal instability and high electricity prices, and practically no net environmental benefits.
If solar power truly is a viable alternative for more traditional energy sources, as solar energy advocates claim, it should
be able to compete in the market without decades of government assistance. It is a mistake to view solar energy as an
obvious alternative to conventional energy sources. Spending billions of taxpayer dollars on a system that is not
predictable, efficient, or reliable is wasteful and illogical.
We conclude that solar-generated electricity is unreliable in two of the three aspects that we explored. The “green”
face of solar is appealing to many, but the environmental benefits of solar energy are outweighed by its economic and
physical costs.
Reliability of Renewable Energy: Solar
26