WRSC Renewable Energy
Solutions
For Utility-Scale Applications
Images: Cleantechia.com, biocomicfuel.com
METHODOLOGY
METRICS
For each Renewable Option, the following factors were compiled and analyzed:
Capacity
Reliability
Technology Risk
Legal/Regulatory
Available
Incentives
Carbon Footprint
Environmental
Impact
Payback Period
Marginal Cost
Ease of
Implementation
The factors highlighted in grey are evaluated in the following report.
All sources listed on accompanying spreadsheet
RENEWABLE ENERGY
SOLUTIONS
Concentrating solar power (CSP) technologies use mirrors to reflect and concentrate sunlight onto receivers
that collect the solar energy and convert it to heat. This thermal energy can then be used to produce
electricity via a steam turbine or heat engine driving a generator. The following four technologies are forms
of CSP:
Solution
Parabolic Trough (CSP)
Overview
Trough technology is a type of solar thermal energy collector and is constructed as a long
parabolic mirror. Sunlight is reflected by the mirror and concentrated on a central tube. It uses
one-axis (usually North to South) tracking and achieves a maximum temperature of about
400°C. This relatively low operating temperature makes it very difficult to provide the amount
of heat storage (in a cost-effective manner) that is required for around-the-clock availability.
Power Tower (CSP)
Tower receiver technology uses two-axis tracking and achieves a maximum temperature of
about 650°C. The higher operating temperature of tower technology reduces susceptibility of
these systems to efficiency losses, especially when dry cooling is used.
Dish Sterling/Dish Engine
(CSP)
Dish Engine systems convert solar thermal energy into mechanical energy and then to
electrical energy
in much the same way that conventional power plants convert thermal energy from combustion
of a fossil fuel to electricity. They use a mirror array to reflect and concentrate incoming
sunlight onto a receiver. Dish Engine systems have the inherent hybrid capability to operate on
either solar energy or a fossil fuel, or both, making them an attractive option.
Linear Fresnel Reflector
(CSP)
Linear Fresnel reflector technology uses one-axis tracking and achieves a maximum
temperature of about 400°C. The reduced efficiency (15% to 25%) compared to troughs is
expected to be offset by substantially lower capital costs.
RENEWABLE ENERGY SOLUTIONS
Solar PV
Large Scale Solar PV Installations generate electrical power by converting solar radiation into
direct current electricity using semiconductor panels. Rapid advancements in PV technology
are making it an increasingly cost-effective option for utilities who require it in their energy
portfolio.
Big Wind
Large wind farms, thanks to increased investment and policy, are very prevalent across the
US. With a very low marginal cost ($0.01-$0.02/kWh) and several mechanisms in place to
expedite their development in California, utility use of wind power continues to grow. Storage
issues, however, limit the availability of energy needed to match peak loads, making new
transmission infrastructure a critical factor in their development.
Biomass/Biogas
Biomass includes agricultural residues, forest resources, perennial grasses, woody energy,
crops, wastes (municipal solid waste, urban wood waste, and food waste), and algae. It is
unique among renewable energy resources in that it can be converted to carbon-based fuels
and chemicals, in addition to power.
Geothermal
Utility-scale geothermal power production employs three main technologies. These are known
as dry steam, flash steam and binary cycle systems. The technology employed depends on the
temperature and pressure of the geothermal reservoir. Unlike solar, wind, and hydro-based
renewable power, geothermal power plant operation is independent of fluctuations in daily and
seasonal weather.
CAPACITY
To measure the productivity of a renewable energy option, we use its Capacity Factor (CF), which is the
amount of energy a power station generates over time (usually a year) compared to what it could have
produced if it had been running at full power for the whole period. Capacity Factor is important not only
because it reflects the performance of a power station, but also because a higher capacity factor represents
a more stable power grid.
0 .9
0 .8 5
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Renewable Energy Options
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Capacity Factor
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CAPACITY INSIGHTS
Renewable Energy
Option
Capacity Factor
Geothermal
.85
Biomass/Biogas
.70
Parabolic
Technologies:
• Parabolic Trough
• Linear Fresnel
Nuclear .95 - .98
Coal .65 - .75
Reflector
.56
.54
Geothermal Energy’s high capacity factor is due to the nature of its source, the Earth’s heat, which is
independent of daily and seasonal weather fluctuations, allowing it to run at full power most of the time.
It’s ability to match peak loads, makes it a promising option to replace dirty coal in the energy mix.
Similarly, with a steady supply, Biomass/gas plants can run at full power around the clock.
Of the four CSP based Solutions, Parabolic Reflector Technologies - Linear Fresnel and Parabolic
Trough have significantly greater productivity and grid stability than the other two options. It should be
noted, however, that Power Tower technologies, have a projected Capacity Factor of .73. Although
development is less advanced than Parabolic Reflector based systems, they offer higher efficiency and
better energy storage capability, which is required for around-the-clock dispatchability (NREL).
RELIABILITY
An Availability Factor (AF) is used to determine how reliable or constant an energy source is, especially
during peak loads. Note, this is different from capacity factor which measures what percentage of the time the
plant is able to run at full capacity. When looking at the AF it is important not only to compare across
renewable sources but also to conventional fossil fuel based sources.
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Renewable Energy Options
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Availability Factor 1 (Low) - 5 (High)
0 .9
RELIABILITY INSIGHTS
Renewable Energy Option
Availability Factor
Geothermal
.80
Concentrated Solar Technologies
.70
Wind
Biomass/Biogas
.30
.80
Coal
.65 - .90
Nuclear .70 - .90 (depending on how new the
plant is)
Geothermal is considered the most reliable source due to its ability to generate a steady stream of
energy 24/7.
Although Solar is an intermittent resource, concentrated solar energy can be stored at high
temperatures using molten salts. Salts are an effective storage medium because they are low-cost,
have a high specific heat capacity and can deliver heat at temperatures compatible with
conventional power systems.
Wind and Biomass/Biogas are less reliable since their energy source is more variable.
INSIGHTS CONT…
BioMass/Gas Source Breakdown
Wood
Municiple Waste
Agricultural Waste
Land Fill Gas
Wood comprises the majority of the energy source.
Therefore, logging regulations and transportation
costs vary greatly depending on the location of the
plant.
Wind, also an intermittent source, cannot guarantee
constant availability. And without storage, must be
used as soon as it is produced, or immediately
transported to where it can be used, through
transmission lines. Improved reliability is possible
with a widely geographically dispersed set of wind
farms, raising its availability factor to .85.
Image: http://www.dasgelbeforum.de.org/
TECHNOLOGY RISK
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Technology Risk Ratings 1 (High Risk) - 5 (Low Risk)
Technology Risk is the degree of uncertainty associated with technology performing according to its planned
or desired functionality. It is important when considering renewable energy options because performance in
lab or pilot studies can vary greatly from installed & operational performance.
TECHNOLOGY RISK INSIGHTS
Renewable Energy Option
Parabolic Trough
Solar PV
Wind
Biomass/Biogas
Linear Fresnel
Geothermal
Power Tower
Dish Sterling (Dish Engine)
Rating
5 (Low)
4
3
(Moderate)
2 (High)
• Trough technology is further advanced than tower, fresnel and dish technology, with 354 MW of commercial generation in
operation in US. It is fully mature and there is low technical and financial risk in developing near-term plants.
• Solar PV, Wind & Biomass/gas are all well established technologies with proven operational performance.
• Linear Fresnel, while the oldest CSP technology, suffers from a lack of reference plants already built, as well as up and
running.
• Geothermal energy provided 16,010 GWh of electricity in 2005. However, larger scale use is limited unless permeability can
be increased. The DOE has determined that the most critical near-term goal is the successful demonstration of Enhanced
Geothermal Systems (EGS) and has identified 2015 as the key decision point for determining if it is technically feasible.
• Tower technology has been successfully demonstrated with a conceptual and pilot plants (Solar One and Solar Two) but has
not been proven in a large commercial application.
• Dish Engine systems face high technology development risk. The DOE is currently working with companies to design,
develop, install, and test pre-production prototype 25-kilowatt systems.
ENVIRONMENTAL RISK
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Environmental Risk Ratings 1 (High Risk) - 5 (Low Risk)
Environmental Risks associated with utility-scale Renewable Energy Installations can be very high and vary greatly on a siteby-site basis. Mitigating these risks can delay projects for years and cost millions in legal fees. Additionally, over the life of a
plant the laws and regulations governing the environmental impacts are likely to change.
ENVIRONMENTAL RISK INSIGHTS
Renewable Energy Option
Wind
Linear Fresnel Reflector
Solar PV
Biogas
Geothermal
Power Tower
Parabolic Trough
Dish Engine
Biomass
Rating
5 (Low)
3 (Moderate)
2 (High)
• Wind carries low environmental risk because land is minimally effected and can still be used for agriculture/livestock.
Additionally, it is well established and environmental risk assessments are easily carried out.
• Linear Fresnel installations use less than 4 acres/MW, making the land requirement less than trough plants because more
surface area can be covered with mirrors.
• Solar PV installations use 4 acres/MW, and have minor panel disposal issues.
• Biogas generation typically improves air quality, since methane from landfills is used as an energy source instead of being
released into the atmosphere.
• Geothermal energy has low environmental risk and impact. When used with a closed-loop binary power plant, geothermal
systems emit zero greenhouse gas emissions and have a near zero environmental risk or impact.
Typically parabolic trough power plants use about 8-10 acres/MW, Tower and Dish Engine use 10-15 acres/MW. Installations
are usually are in remote desert areas, however unique plants and animals have to be protected costing time and money.
Biomass power raises the most environmental issues.. Combustion of biomass and biomass-derived fuels produces air
pollution; beyond this, there are concerns about the impacts of using land to grow energy crops that could be used for food.
MARGINAL COST ESTIMATES
One of the most important factors in evaluating how competitive renewable energy options are with traditional fossil
fuels is the Levelized Cost of Energy (LCOE), or constant price per unit of energy that causes the utility company’s
investment to break even. The LCOE equation evaluates the life-cycle energy cost and production of a power plant,
allowing alternative renewable energy options to be compared.
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Marginal Cost ($/kWh)
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.30 - .40
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.06 - .10
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.08 - .10
.04 - .06
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.06
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Renewable Opt ions
Renewable
Energy Options
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MARGINAL COST INSIGHTS
Renewable Energy Option
Levelized Energy Cost ($/kWh)
Wind
Power Tower
$0.01 - $0.02
$0.04 - $0.06
Geothermal
Biomass/Biogas
Dish Sterling/Dish Engine
Linear Fresnel
Parabolic Trough
$0.08 - 0.10
$0.05 - $0.08
$0.06
$0.07
$0.06 - $0.10
Solar PV
$0.30 - $0.40
• Even with wind generation’s high upfront costs, low maintenance and low operational costs drive
the LCOE down.
• With advances in technology, Power Towers are expected to be the most economical solar energy
technology with estimates of less than 4 cents/kWh.
•The other 3 CSP technologies range between $0.06 - $0.10/kWh. Prices are expected to drop as
more plants become operational and efficiencies are gained from new technologies.
• Biomass prices depend on the price of its source, which can vary widely at times.
Utility-Scale Solar PV installation have the highest LCOE, which is greatly influenced by the plants
capacity factor. By raising the capacity factor, the LCOE can decrease substantially, even up to four
times lower.
AVAILABLE INCENTIVES
Incentives Rating 1 (Low) - 5 (High)
Federal/State policy and tax incentives greatly influence utility investment in renewables and can help them
offset high initial costs. The availability and degree of incentives for renewable energy options varies across
industries and
states.
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Renewable Energy Options
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INCENTIVES INSIGHTS
Renewable Energy Option
Wind
Solar PV
Power Tower
Parabolic Trough
Dish Engine
Linear Fresnel Reflector
Biomass/Biogas
Geothermal
Rating
5 (High)
3 (Moderate)
2 (Low)
Wind and Solar PV receive a high degree of tax and policy incentives. Large Federal tax incentives and new
state policies that expedite permitting, environmental reviews and approval processes for new Wind Farms
and Solar PV installations have enabled both industries to flourish. c
• Concentrated Solar Technology is also receiving a relatively high degree of support. The same federal tax
incentives are available to utilities looking to utilize these renewable energy supplies and, in California,
efforts are being made to streamline the approval processes for new CSP plants as well.
• New National and DOE incentives are aimed at expanding the scope of Biomass/Biogas to include the
development of other advanced biofuels that will contribute to the requirements of the Renewable Fuels
Standard (RFS).
The largest problem facing the geothermal industry is the lack of a Federal policy promoting geothermal
development. The economic viability of most geothermal electricity production projects continues to be
dependent on the financial support created by state energy policy.
CASE STUDIES
Utility-Scale Case Studies (OSTI,
NREL):
http://www.osti.gov/accomplishments/NRELprofiles.html