Renewable Energy 63 (2014) 153e161
Contents lists available at ScienceDirect
Renewable Energy
journal homepage: www.elsevier.com/locate/renene
Analysis of renewable energy development to power generation in the
United States
Alireza Aslani a, b, *, Kau-Fui V. Wong b
a
b
Industrial Management Department, Faculty of Technology, University of Vaasa, Vaasa 65101, Finland
Department of Mechanical and Aerospace Engineering, College of Engineering, University of Miami, Miami, FL 33146, USA
a r t i c l e i n f o
a b s t r a c t
Article history:
Received 2 May 2013
Accepted 28 August 2013
Available online 28 September 2013
Renewable energy resources have historically played a small role for electricity generation in the US.
However, concerns such as security of energy supply, limitations and price fluctuations of fossil fuels, and
threats of climate changes have encouraged US policy makers to think and debate about diversification
strategy in the energy supply and promotion of renewables. The current paper discusses the role of
renewable portfolio in the US energy action plan during 2010e2030. A system dynamics model is
constructed to evaluate different costs of renewable energy utilization by 2030. Results show that while
renewables will create a market with near 10 billion $ worth (in the costs level) in 2030, the total value of
renewable energy promotion and utilization in the US will be more than 170 billion $(in the costs level)
during 2010e2030.
Ó 2013 Elsevier Ltd. All rights reserved.
Keywords:
Renewable energy portfolio
Cost analysis
Electricity generation
US
System dynamics
1. Introduction
One of the important factors of US energy production system is
security of energy supply at this time. Energy security concerns
along with consumption growth are rapidly rising in importance in
the US. In response, renewable energy resources (RER) are options
to reduce dependency on imported energy and provide social and
environmental benefits. However, a key question is how RERs can
be used to meet US energy needs and U.S. electricity needs?
RERs are typically used in three main frames: electricity generation, bio-products, and in heating/cooling systems. To succeed
diffusion programs of renewable energy (RE) development, different
strategies such as technological improvements, increased economies
of scale, and strong policy support have been contributed in the US.
Nevertheless, compared to traditional energy sources, promotion of
electricity generation from RERs is limited because of its relative
investment high costs, and strong penetration of nuclear and fossil
fuel power plants in the US.
This study provides an evaluation to analyze the costs of RE
promotion and operation according to the U.S. Department of Energy action plan for RE development by 2030. Owning to the
complexity of such studies, as well as different factors and policies
* Corresponding author. Industrial Management Department, Faculty of Technology, University of Vaasa, Vaasa 65101, Finland. Tel.: þ358 44 255 0010.
E-mail address: Alireza.aslani@uva.fi (A. Aslani).
0960-1481/$ e see front matter Ó 2013 Elsevier Ltd. All rights reserved.
http://dx.doi.org/10.1016/j.renene.2013.08.047
effects on costs analysis, the system dynamics approach is implemented to analyze the effectiveness of RE policies.
The work is organized based on the following sections. Energy
structure, supply, and consumption in the US are reviewed
in Section 2. In Section 3, the role of RE utilization is discussed in
the US. The important RERs and their potentials are also reviewed
in that section. Related polices and government’s schemes to promotion of RE utilization in the US are described in Section 4.
Different parts of the development costs of RE in the US are
reviewed in Section 5. Finally, a system dynamics model for cost
analysis of RE utilization in the US during 2011e2030 is proposed
in Section 6.
2. Energy structure in the US
The US with 315,746,720 populations (4.5% of world) consumes
around 19.2% of the world’s energy (83% of North America) [1,2].
The country is also the second largest energy consumer after China
and ranks seventh in energy consumption per-capita after Canada
and some small countries [2]. According to IEA energy statistics,
fossil fuels are the majority of total primary energy supply (84.3%
share in 2009) [3]. Oil with 37.1%, natural gas with 24.7%, and coal/
peat with 22.5% are the main sources of fossil fuels for energy
consumption in the US in 2009 [3]. RERs had a share of 5.8% in total
primary energy supply in 2009 [3]. Fig. 1 and Table 1 show the share
and amount of each renewables in both electricity and heat generation in the US in 2009 [4]. As Fig. 1 illustrates, the main RER in
the US is hydropower utilized from hydroelectric dams.
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A. Aslani, K.-F.V. Wong / Renewable Energy 63 (2014) 153e161
Fig. 1. Share of each renewables in electricity generation in US in 2009 [4].
While 41% of energy demand in the US was used for electricity
generation, around 28% of energy demand was used for transportation in 2009 (20% industry and 11% residential and commercial). Fig. 2 shows the share of each source in each sector [5].
As energy consumption has always increased at a faster rate
than energy production over the last decades in the US, the country
is dependent to imports particularly for transportation sector. According to statistics, while total energy production in the US
was1686.4 Mtoe, the net imports was 559.01 Mtoe in 2009 (33%)
[6]. During 2010e2011, while use of coal and oil fell in the US, use of
natural gas increased [7].
3. Renewable energy utilization in the US
RERs in the United States accounted for 11.1% of the electricity
generation in 2009 [8]. This was increased to 13.2% in 2012 (19%
growth). Fig. 3 shows the trend of electricity generation by RE in
recent years.
Although the major RER for electricity generation in the US is
hydropower (Table 1), some states such as California, Iowa, and
North Dakota have generated more than 10% of their electricity just
from wind power, solar power, and geothermal.
As diffusion of RERs along with improving energy efficiency are
two important subjects of White house energy policies in order to
response to challenges of energy security and climate change,
development of RER utilization have been emphasized by the US
policy makers in different levels and states [10]. According to the
“New Energy for America plan”, the share of RERs in electricity
generation should be increased to 25% by 2025 [11].
On the other hand, Feasibility studies show that all US states
have strong potential for RER utilization at least in one source. For
instance, a quarter of the U.S. land area has high potential for
electricity generation from wind power with the same price of
natural gas or coal. Further, solar energy in seven southwest states
can provide 10 times of the current electric generation in the US
[12]. Fig. 4 shows the portfolio map of RERs in the US extracted from
the National Renewable Energy Laboratory (NREL) database [13].
As Fig. 4 illustrates, US has a strong potential for solar energy
utilization. With annual growth averaging 11.7%, solar power along
with wind power is the fastest growing of RERs in the country [23].
Fig. 2. U.S. primary energy consumption by source and sector [5].
While new and more efficient solar technologies are being developed, utilization of this source will be more popular [34]. Today
Both Sandia National Laboratories and the National Renewable
Energy Laboratory (NREL), as the main government organizations
for supporting RE utilization, have heavy funded solar research
programs. The Ivanpah solar project with 392 MW capacity is a
solar thermal power facility that is under construction in southeastern California [16]. However, because it currently accounts for
only 0.5% of total renewable generation, solar would remain a minor part of the renewable mix.
Wind power utilization has swiftly grown over the past decade,
from 18 GW to 179 GW during 2000e2010. It had a big jump, 26%
growth, during 2010e2011 [7]. Western US, Alaska, and Appalachians are regions with strongest wind in the US. Texas, with
9728 MW and Iowa with 3670 MW are two examples of wind power utilization in the US.
On the other hand, the western US is the best region for
geothermal utilization. Geothermal technologies can be used in
three frames: heat pumps, direct systems, and deep reservoirs to
generate electricity [14]. It is estimated the total production of
geothermal will be15,000 MW by 2025 [17]. Indeed, major hydroelectric dams are located in the Northwest, on the Colorado River,
and Tennessee Valley. They provide about 67% of total electricity
generation by RERs. Finally, biomass can potentially be produced
almost anywhere in the US, in particular eastern US. In general, the
share of total electricity generation by non-hydropower renewable
generation should be increased from about 4 percent in 2010 to 9
percent in 2035 [23].
4. Policies related to renewable energy development in the US
The share of RERs in electricity generation in the US should grow
to 25% by 2025 [30]. Most of the growth in RE electricity generation
is the result of state renewable portfolio standards requirements,
Table 1
Details of utilization of renewables for electricity and heat generation in the US in 2009 [4].
Resource
Biomass
Details
Municipal
waste
Industrial
waste
Primary solid
biofuels
Biogases
Liquid
biofuels
Geothermal
Gross elec. generation (GWh)
Gross heat production (TJ)
16,909
11,736
5532
3818
40,478
30,839
9281
999
91
e
17,046
e
Hydropower
298,410
e
Solar
Wind
Photovoltaic
Thermal
1698
e
816
e
74,226
e
A. Aslani, K.-F.V. Wong / Renewable Energy 63 (2014) 153e161
155
Table 2
Examples of US’s polices to diffusion and promotion of RERs [18,19].
Provisions
-
-
Fig. 3. Total renewable electricity net generation (billion KW) [9].
federal tax credits, and the availability of low-cost feedstocks. Due
to the especial emphasis of the US president to clean and secure
energy, and in order to diffusion of RE utilization, several policies
and encouragement packages have been introduced by US energy
policy makers. As an example, the Defense department has
committed to purchase 1000 MW of electricity generated by RERs.
The Interior department commitment is also to permit 10,000 MW
of RE projects on public land in 2012 [15].
Most energy policies related to diffusion and promotion of RE
utilization take the form of financial incentives in the US. Tax breaks
and reductions, tax exemptions, loans, rebates, and specific funding
are examples of incentives. The targets are increasing security of
energy supply via decreasing dependency on energy imports (oil),
Subsidies for wind, solar, and geothermal producers
Biomass grants
Increasing the amount of biofuel that must be mixed with gasoline
Making geothermal energy more competitive with fossil fuels in generating
electricity
Tax reductions: e.g., $2.7 billion to extend the renewable electricity production credit, or $500 million Clean Renewable Energy Bonds (CREBS) for government agencies for renewable energy projects.
Loan guarantees
Renewable portfolio standard in each states
Taxpayer funding of research and development of solar energy, geothermal
energy, and marine and hydrokinetic renewable energy technologies.
Creation of a training program for “Energy efficiency and renewable energy”
workers
creating jobs, and developing industries, and achieving to a clean
and sustainable society. According to the Energy Policy Act of 2005,
tax incentives and loan guarantees are two main subjects of
improving energy security and promotion of RE in the US [18].
Table 2 summarizes some of the important provisions of “Energy
Policy Act of 2005” and “Energy Independence and Security Act of
2007” related to RE development.
More than 30 states have renewable portfolio standards or
similar laws to promote RERs utilization. According to these standards, electricity providers must generate a minimum amount of
electricity from RE by a specified date [29,33]. This means that each
state determines its own level of RE utilization and noncompliance
penalties. The standards present targets for RE as 1) share of a
utility’s total retail electricity sales, 2) an increase in generating
capacity or 3) share of the growth in retail electricity [29]. As an
example and according to the California renewable portfolio
Fig. 4. Portfolio map of renewables in the US [13].
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Table 3
Renewable portfolio standards in five selected states [23].
State
Selected program mandate
Connecticut
- RERs should account for 27% of sales by 2020,
- The State’s Clean Energy Finance and Investment
Authority is responsible for creating an investment
program for 30 MW residential solar installation,
- 25% of sales from renewable sources by 2025
for large utilities,
- 20% of sales from renewable generation by 2022,
- Designation of waste-to-energy facilities as qualifying
to meet the 20-percent target beyond 2022,
- Solar sources account for 2% of electricity sales by 2022,
- 5880 MW RE utilization by 2015,
- 500 MW of renewable capacity other than wind,
- 15% of sales from the State’s largest generators must
come from RERs by 2020,
- The administrative penalty of 5% per KWh for noncompliance.
Illinois
Maryland
Texas
Washington
standard, 33% of electricity sales should be met by RERs by 2020.
Indeed, the investor-owned utilities should be 20% of sales from
RERs [23]. Table 3 reviews the important targets of renewable
portfolio standard of some selected states.
5. Costs of renewable energy utilization
Investment is a key point for diffusion of RE technologies [24]. To
utilization of RERs economically reasonable, sources should be
adopted pervasively by supports of the government and contributions of the private sector [25]. Researches show that financial
measurement that indicates the required investment and other
costs of RE utilization (e.g., maintenance and operation), as well as
efficiency of each energy source (performance) are two key criteria
for RE promotion [26,27]. Table 4 shows different estimated costs of
electricity generation by RERs in 2017 based on the Energy Information Administration (EIA) analysis (Levelized Cost of Generation
Resources) [20]. Levelized cost shows the competiveness of
different sources to electricity generation and represents KWh of
capital and operating costs of a generating plant over financial life
and duty cycle [20]. Levelized cost include different costs including
capital costs, fuel costs, fixed and variable operations and maintenance (O&M) costs, financing costs, as well as capacity factor of
each plant type [20]. These costs are based on the US national averages that would be different in the local scale costs because of
factors such as local labor markets, cost, and availability of fuel or
the level of accessibility of energy sources.
The capacity factor corresponds to the maximum availability of
each renewable technology directly affects the levelized cost. For
RERs such as wind and solar as the operator cannot control the
amount of utilization and they are dependent on the weather
conditions, the capacity factor is small compared to other RE
technologies. In other word, although the average annual capacity
factor of these sources would be similar to other technologies, the
availabilities are not dependent on operator’s control. Therefore,
the intermittent technologies cannot provide the same contribution to system reliability as operator-controlled technologies can
and they may require additional investment for back-up power.
6. System dynamics model
System dynamics is a methodology based on system thinking to
understand and model the behavior and activities of the complex
systems over time [21]. The methodology is based on the feedback
structure, meaning that decisions with specific goals alter the world
and subsequently lead to new decisions [22]. The process of system
dynamics analysis is comprised of six steps, which are (1) system
understanding, (2) problem identification and definition, (3) system
conceptualization, (4) Simulation and validation, (5) policy/decision
analyzing and improvement, and (6) policy/decision implementation.
Through a review of existing literature among over 1500 pages
of documents and articles including annual reports, detailed government, project reports, and published investigations, we have
assessed the US energy sector to (1) define the main problems and
objectives of renewable energy utilization, and (2) identify the key
variables and policies. Through a review of existing literature, the
causal relationships of renewable energy development and related
costs are extracted and variables can be quantitatively examined
via collecting relevant data. Next section shows the integrated
stockeflow diagram to simulate relationships and behaviors [35].
6.1. Dynamic analysis of renewable energy utilization plans
Fig. 5 shows the proposed system dynamics model of costs and
capacity of electricity generation by renewables in the US during
2010e2030. There are five stocks in the proposed model including
capacity of hydropower electricity, capacity of biomass electricity,
capacity of solar electricity, capacity of wind power electricity, and
capacity of geothermal electricity. The capacity of each RER influenced by current renewable systems operating and new installations (based on the policies and plans), as well as decreased
number of RER systems affected by delay time (depreciation). We
assume that the depreciation periods of RER systems are 20 years
for solar, 25 years for wind, 25 years for geothermal, 30 years for
biomass plants, and 15 years for small hydropower. The number of
increased RER systems (rates in the system dynamics model) are
directly affected by plans and government policies discussed in the
sections 3 and 4. Indeed, the investment, O&M, and fuel costs (for
Biomass) also depend on the US policies and related technologies.
To develop the quantitative model, the data was collected from
Annual Energy Outlook 2011 and 2012 prepared by U.S. Energy
Information Administration (U.S. Department of Energy) [20,23].
Fig. 6 shows the total estimated amount of electricity generated
by RERs in the US during 2010e2030 extracted from the model. The
Table 4
Estimated levelized cost of electricity generation by renewables in 2017 in the US ($/MWh) [20].
Plant type
Capacity factor (%)
Dispatchable renewable technologies
Geothermal
91
Biomass
83
Non-dispatchable renewable technologies
Wind
33
Solar PV
25
Solar thermal
20
Hydro
53
Levelized
capital cost
Fixed O&M
Variable O&M
(including fuel)
Transmission
investment
Total system
levelized cost
75.1
56
11.9
13.8
9.6
44.3
1.5
1.3
98.2
115.4
82.5
140.7
195.6
76.9
9.8
7.7
40.1
4
0
0
0
6
3.8
4.3
6.3
2.1
96
152.7
242
88.9
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157
Fig. 5. System dynamics model of renewable energy development in the US during 2010e2030.
total amount of electricity generated by RERs should reach to
603,166 GWh that means 208,336 GWh new RE systems installation during 2010e2030. According to the defined policy by US
department of energy, RE utilization for electricity generation will
have a fast growth during 2010e2015 (28.5% growth). That is
mainly because of new capacities from wind power (56480 GWh)
and hydropower (40110 GWh). During 2015e2025, this growth will
continue with a slower slope as most of the wind and hydropower
Fig. 6. Total electricity generated by renewable energy resources in the US (GWh).
158
A. Aslani, K.-F.V. Wong / Renewable Energy 63 (2014) 153e161
Fig. 7. Total costs of wind power during 2010e2030 in the US ($).
Fig. 8. Total costs of solar power during 2010e2030 in the US ($).
Fig. 9. Total costs of hydropower during 2010e2030 in the US ($).
A. Aslani, K.-F.V. Wong / Renewable Energy 63 (2014) 153e161
Fig. 10. Total costs of biomass during 2010e2030 in the US ($).
Fig. 11. Total costs of geothermal during 2010e2030 in the US ($).
Fig. 12. Comparing total costs of electricity generation by renewables during 2010e2030 in the US ($).
159
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Table 5
Comparing the amount of total, investment, and O&M costs of renewable portfolio and each source in the selected years ($).
Year
2015
Source/cost
detail
Total cost
Investment
cost
O&M costa
Total cost
Investment cost
O&M costa
Total cost
Investment
cost
O&M costa
Wind powerb
Solar power
Hydropower
Biomass
Geothermal
Total
2,047,490,000
187,745,000
1,878,270,000
2,469,860,000
335,973,000
6,919,338,000
1,980,000
336,300
78,591,800
339,696,000
86,064,600
506,668,700
2,045,510,000
187,408,700
1,799,678,200
2,130,164,000
249,908,400
6,412,669,300
2,330,470,000
269,576,000
1,894,380,000
4,637,000,000
545,944,000
9,677,370,000
147,015,000
60,197,700
36,912,000
0
125,567,000
369,691,700
2,183,455,000
209,378,300
1,857,468,000
4,637,000,000
420,377,000
9,307,678,300
2,430,000,000
321,322,000
1,908,880,000
4,600,000,000
656,848,000
9,917,050,000
147,015,000
65,000,000
36,900,000
0
125,000,000
373,915,000
2,282,985,000
256,322,000
1,871,980,000
4,600,000,000
531,848,000
9,543,135,000
a
b
2025
2030
Including fuel cost for biomass.
Compared to 2015e2025, wind power will have a fast growth rate during 2010e2015.
capacities will be utilized. The total amount of electricity generation from RERs will be increased around 15% during 2015e2025.
Finally, during 2025e2030 this growth will continue with slower
rate because of using the capacities for wind, hydropower and
biomass, as well as depreciation of current installations. The most
growth during 2025e2030 will be happened by solar and
geothermal technologies.
Figs. 7e11 show the total costs of electricity generation for each
RER. These costs include current RE systems (O&M and fuel costs)
and new installations (investment costs) during 2010e2030. As
Fig. 7 illustrates, the most investment in the wind power are being
happened during 2010e2015 (56480 GWh new capacities). The
reduction in the total costs after 2015 is because of the reduction in
new capacities investment (due to almost high investment cost).
Thereby, most part of the cost is O&M cost.
Fig. 12 compares the total costs of electricity generation from
each RERs with portfolio of renewables. According to the figure, the
total costs of RERs utilization will be rise from 6,613,930,000$ (for
394,830 GWh utilization) in 2010 to 9,917,050,000$ (for
603,166 GWh utilization) in 2030 (53% growth in utilization
compared to 50% growth in the costs).
Table 5 shows the amount of total, investment and O&M costs of
renewable portfolio and each source in the three selected years
2015, 2025, and 2030.
7. Validation and testing of the model
Testing and validation of the models are very important in the
system dynamics research. Model testing and validation in the
current research are based on the matching the models’ results
with the real system. The first aim of the model validation is to
provide good and accurate statistical information as decisions may
be made based on the model contributions [31]. As Kelton and Law
(1991) highlight, if a model has not a “valid” illustration of a system,
the model results serve little useful information about the real
system. To test and validate the system dynamics model we
implemented two approach: model structure validation, and model
behavior validation [32].
According to the “structure validation”, the structure of system
dynamics model is suitable if it is internally consistent with its
assumptions and the causal structures contains the keys feedback
loops for describing the model and real system. The model implemented in the current research responses to these factors from two
viewpoints. First, our system dynamics model describes the
behavior of the system based on the identified variables and causal
loop extracted by the researcher’s observation and expert’s opinions. Second, it was designed based on the real data, trends, and
opinions of the professionals in the energy sector. In particular, the
researchers tried to involve stakeholders and decision makers of
the policy options from the beginning of the model building.
Therefore, changes in the simulation forecast closely follow
changes in the real world systems.
From behavior validation aspect, our system dynamics model
were checked by two methods; 1) Reviewing the process of the
modeling and results and comparing with historical patterns and 2)
testing the results with experts and comparing with the plans
defined by US targets.
8. Conclusion
Today one of the important factors for robust development of an
economic is security of energy supply [28]. Energy security concerns
along with threats of carbon dioxide emission and consequently
global warming are rapidly rising in importance for developed
countries. To response the challenges, diversification in the energy
sources is debated as one of the important strategies by policy makers.
Due to the energy consumption growth and dependency on
fossil fuels in the US, diffusion of electricity/heat generation from
renewables creates an import part of the US energy policies for the
future. Our studies show that the US is one of the richest countries
in terms of renewable energy portfolio. However, commercial
development of renewable energy systems is highly dependent to
the utilization costs and government policies. This article discussed
about a system dynamics model to evaluate different costs of
renewable energy development in the US during 2010e2030. Due
to the role of electricity in energy portfolio of US residential/commercial and industries, the analysis focused on electricity generation. Depending to the economic growth, renewable energy
utilization would change from 102% increase in the High Economic
Growth scenario to 62% increase in the Low Economic Growth
scenario in the US [23].
As future research, the created system dynamics model can be
implemented in other countries and the results can be compared
with current work. Further, the total costs of renewable energy
development in the US can be compared with other sources along
with risk analysis to indicate the strength and weaknesses of the
renewables in the US. Finally, accurate analysis of each parameters
of renewable energy utilization, strategies for cost reduction via
issues such as combination of markets, tax, and regulatory incentives are subjects that are suggested by authors.
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