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Renewable Energy 63 (2014) 153e161

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Renewable Energy

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Analysis of renewable energy development to power generation in theUnited States

Alireza Aslani a, b, *, Kau-Fui V. Wong b

a Industrial Management Department, Faculty of Technology, University of Vaasa, Vaasa 65101, Finlandb 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

Article history:Received 2 May 2013Accepted 28 August 2013Available online

Keywords:Renewable energy portfolioCost analysisElectricity generationUSSystem dynamics

* Corresponding author. Industrial Management Dnology, University of Vaasa, Vaasa 65101, Finland. Tel

E-mail address: Alireza.aslani@uva.fi (A. Aslani).

0960-1481/$ e see front matter � 2013 Elsevier Ltd.http://dx.doi.org/10.1016/j.renene.2013.08.047

a b s t r a c t

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, andthreats of climate changes have encouraged US policy makers to think and debate about diversificationstrategy in the energy supply and promotion of renewables. The current paper discusses the role ofrenewable portfolio in the US energy action plan during 2010e2030. A system dynamics model isconstructed to evaluate different costs of renewable energy utilization by 2030. Results show that whilerenewables will create a market with near 10 billion $ worth (in the costs level) in 2030, the total value ofrenewable energy promotion and utilization in the US will be more than 170 billion $(in the costs level)during 2010e2030.

� 2013 Elsevier Ltd. All rights reserved.

1. Introduction

One of the important factors of US energy production system issecurity of energy supply at this time. Energy security concernsalong with consumption growth are rapidly rising in importance inthe US. In response, renewable energy resources (RER) are optionsto reduce dependency on imported energy and provide social andenvironmental benefits. However, a key question is how RERs canbe used to meet US energy needs and U.S. electricity needs?

RERs are typically used in three main frames: electricity genera-tion, bio-products, and in heating/cooling systems. To succeeddiffusion programs of renewable energy (RE) development, differentstrategies such as technological improvements, increased economiesof scale, and strong policy support have been contributed in the US.Nevertheless, compared to traditional energy sources, promotion ofelectricity generation from RERs is limited because of its relativeinvestment high costs, and strong penetration of nuclear and fossilfuel power plants in the US.

This study provides an evaluation to analyze the costs of REpromotion and operation according to the U.S. Department of En-ergy action plan for RE development by 2030. Owning to thecomplexity of such studies, as well as different factors and policies

epartment, Faculty of Tech-.: þ358 44 255 0010.

All rights reserved.

effects on costs analysis, the system dynamics approach is imple-mented to analyze the effectiveness of RE policies.

The work is organized based on the following sections. Energystructure, supply, and consumption in the US are reviewedin Section 2. In Section 3, the role of RE utilization is discussed inthe US. The important RERs and their potentials are also reviewedin that section. Related polices and government’s schemes to pro-motion of RE utilization in the US are described in Section 4.Different parts of the development costs of RE in the US arereviewed in Section 5. Finally, a system dynamics model for costanalysis of RE utilization in the US during 2011e2030 is proposedin Section 6.

2. Energy structure in the US

The US with 315,746,720 populations (4.5% of world) consumesaround 19.2% of the world’s energy (83% of North America) [1,2].The country is also the second largest energy consumer after Chinaand ranks seventh in energy consumption per-capita after Canadaand 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 energyconsumption in the US in 2009 [3]. RERs had a share of 5.8% in totalprimary energy supply in 2009 [3]. Fig.1 and Table 1 show the shareand amount of each renewables in both electricity and heat gen-eration in the US in 2009 [4]. As Fig. 1 illustrates, the main RER inthe US is hydropower utilized from hydroelectric dams.

Fig. 1. Share of each renewables in electricity generation in US in 2009 [4].

Fig. 2. U.S. primary energy consumption by source and sector [5].

A. Aslani, K.-F.V. Wong / Renewable Energy 63 (2014) 153e161154

While 41% of energy demand in the US was used for electricitygeneration, around 28% of energy demand was used for trans-portation in 2009 (20% industry and 11% residential and commer-cial). Fig. 2 shows the share of each source in each sector [5].

As energy consumption has always increased at a faster ratethan energy production over the last decades in the US, the countryis dependent to imports particularly for transportation sector. Ac-cording to statistics, while total energy production in the USwas1686.4 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 ofnatural gas increased [7].

3. Renewable energy utilization in the US

RERs in the United States accounted for 11.1% of the electricitygeneration in 2009 [8]. This was increased to 13.2% in 2012 (19%growth). Fig. 3 shows the trend of electricity generation by RE inrecent years.

Although the major RER for electricity generation in the US ishydropower (Table 1), some states such as California, Iowa, andNorth Dakota have generated more than 10% of their electricity justfrom wind power, solar power, and geothermal.

As diffusion of RERs along with improving energy efficiency aretwo important subjects of White house energy policies in order toresponse to challenges of energy security and climate change,development of RER utilization have been emphasized by the USpolicy makers in different levels and states [10]. According to the“New Energy for America plan”, the share of RERs in electricitygeneration should be increased to 25% by 2025 [11].

On the other hand, Feasibility studies show that all US stateshave strong potential for RER utilization at least in one source. Forinstance, a quarter of the U.S. land area has high potential forelectricity generation from wind power with the same price ofnatural gas or coal. Further, solar energy in seven southwest statescan provide 10 times of the current electric generation in the US[12]. Fig. 4 shows the portfolio map of RERs in the US extracted fromthe National Renewable Energy Laboratory (NREL) database [13].

As Fig. 4 illustrates, US has a strong potential for solar energyutilization. With annual growth averaging 11.7%, solar power alongwith wind power is the fastest growing of RERs in the country [23].

Table 1Details of utilization of renewables for electricity and heat generation in the US in 2009

Resource Biomass

Details Municipalwaste

Industrialwaste

Primary solidbiofuels

Biogases

Gross elec. generation (GWh) 16,909 5532 40,478 9281Gross heat production (TJ) 11,736 3818 30,839 999

While new and more efficient solar technologies are being devel-oped, utilization of this source will be more popular [34]. TodayBoth Sandia National Laboratories and the National RenewableEnergy Laboratory (NREL), as the main government organizationsfor supporting RE utilization, have heavy funded solar researchprograms. The Ivanpah solar project with 392 MW capacity is asolar thermal power facility that is under construction in south-eastern California [16]. However, because it currently accounts foronly 0.5% of total renewable generation, solar would remain a mi-nor 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 Appala-chians are regions with strongest wind in the US. Texas, with9728 MW and Iowa with 3670 MW are two examples of wind po-wer utilization in the US.

On the other hand, the western US is the best region forgeothermal utilization. Geothermal technologies can be used inthree frames: heat pumps, direct systems, and deep reservoirs togenerate electricity [14]. It is estimated the total production ofgeothermal will be15,000 MW by 2025 [17]. Indeed, major hydro-electric dams are located in the Northwest, on the Colorado River,and Tennessee Valley. They provide about 67% of total electricitygeneration by RERs. Finally, biomass can potentially be producedalmost anywhere in the US, in particular eastern US. In general, theshare of total electricity generation by non-hydropower renewablegeneration should be increased from about 4 percent in 2010 to 9percent in 2035 [23].

4. Policies related to renewable energy development in the US

The share of RERs in electricity generation in the US should growto 25% by 2025 [30]. Most of the growth in RE electricity generationis the result of state renewable portfolio standards requirements,

[4].

Geothermal Hydropower Solar Wind

Liquidbiofuels

Photovoltaic Thermal

91 17,046 298,410 1698 816 74,226e e e e e e

Fig. 3. Total renewable electricity net generation (billion KW) [9].

Table 2Examples of US’s polices to diffusion and promotion of RERs [18,19].

Provisions

- 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 generatingelectricity

- Tax reductions: e.g., $2.7 billion to extend the renewable electricity produc-tion credit, or $500 million Clean Renewable Energy Bonds (CREBS) for gov-ernment agencies for renewable energy projects.

- Loan guarantees- Renewable portfolio standard in each states- Taxpayer funding of research and development of solar energy, geothermalenergy, and marine and hydrokinetic renewable energy technologies.

- Creation of a training program for “Energy efficiency and renewable energy”workers

A. Aslani, K.-F.V. Wong / Renewable Energy 63 (2014) 153e161 155

federal tax credits, and the availability of low-cost feedstocks. Dueto the especial emphasis of the US president to clean and secureenergy, and in order to diffusion of RE utilization, several policiesand encouragement packages have been introduced by US energypolicy makers. As an example, the Defense department hascommitted to purchase 1000 MW of electricity generated by RERs.The Interior department commitment is also to permit 10,000 MWof RE projects on public land in 2012 [15].

Most energy policies related to diffusion and promotion of REutilization take the form of financial incentives in the US. Tax breaksand reductions, tax exemptions, loans, rebates, and specific fundingare examples of incentives. The targets are increasing security ofenergy supply via decreasing dependency on energy imports (oil),

Fig. 4. Portfolio map of ren

creating jobs, and developing industries, and achieving to a cleanand sustainable society. According to the Energy Policy Act of 2005,tax incentives and loan guarantees are two main subjects ofimproving energy security and promotion of RE in the US [18].Table 2 summarizes some of the important provisions of “EnergyPolicy Act of 2005” and “Energy Independence and Security Act of2007” related to RE development.

More than 30 states have renewable portfolio standards orsimilar laws to promote RERs utilization. According to these stan-dards, electricity providers must generate a minimum amount ofelectricity from RE by a specified date [29,33]. This means that eachstate determines its own level of RE utilization and noncompliancepenalties. The standards present targets for RE as 1) share of autility’s total retail electricity sales, 2) an increase in generatingcapacity or 3) share of the growth in retail electricity [29]. As anexample and according to the California renewable portfolio

ewables in the US [13].

Table 3Renewable 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 InvestmentAuthority is responsible for creating an investmentprogram for 30 MW residential solar installation,

Illinois - 25% of sales from renewable sources by 2025for large utilities,

Maryland - 20% of sales from renewable generation by 2022,- Designation of waste-to-energy facilities as qualifyingto meet the 20-percent target beyond 2022,

- Solar sources account for 2% of electricity sales by 2022,Texas - 5880 MW RE utilization by 2015,

- 500 MW of renewable capacity other than wind,Washington - 15% of sales from the State’s largest generators must

come from RERs by 2020,- The administrative penalty of 5% per KWh for noncompliance.

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standard, 33% of electricity sales should be met by RERs by 2020.Indeed, the investor-owned utilities should be 20% of sales fromRERs [23]. Table 3 reviews the important targets of renewableportfolio standard of some selected states.

5. Costs of renewable energy utilization

Investment is a key point for diffusion of RE technologies [24]. Toutilization of RERs economically reasonable, sources should beadopted pervasively by supports of the government and contribu-tions of the private sector [25]. Researches show that financialmeasurement that indicates the required investment and othercosts of RE utilization (e.g., maintenance and operation), as well asefficiency of each energy source (performance) are two key criteriafor RE promotion [26,27]. Table 4 shows different estimated costs ofelectricity generation by RERs in 2017 based on the Energy Infor-mation Administration (EIA) analysis (Levelized Cost of GenerationResources) [20]. Levelized cost shows the competiveness ofdifferent sources to electricity generation and represents KWh ofcapital and operating costs of a generating plant over financial lifeand duty cycle [20]. Levelized cost include different costs includingcapital costs, fuel costs, fixed and variable operations and mainte-nance (O&M) costs, financing costs, as well as capacity factor ofeach plant type [20]. These costs are based on the US national av-erages that would be different in the local scale costs because offactors such as local labor markets, cost, and availability of fuel orthe level of accessibility of energy sources.

The capacity factor corresponds to the maximum availability ofeach renewable technology directly affects the levelized cost. ForRERs such as wind and solar as the operator cannot control theamount of utilization and they are dependent on the weatherconditions, the capacity factor is small compared to other REtechnologies. In other word, although the average annual capacity

Table 4Estimated levelized cost of electricity generation by renewables in 2017 in the US ($/MW

Plant type Capacity factor (%) Levelizedcapital cost

Fixed O

Dispatchable renewable technologiesGeothermal 91 75.1 11.9Biomass 83 56 13.8Non-dispatchable renewable technologiesWind 33 82.5 9.8Solar PV 25 140.7 7.7Solar thermal 20 195.6 40.1Hydro 53 76.9 4

factor of these sources would be similar to other technologies, theavailabilities are not dependent on operator’s control. Therefore,the intermittent technologies cannot provide the same contribu-tion to system reliability as operator-controlled technologies canand they may require additional investment for back-up power.

6. System dynamics model

System dynamics is a methodology based on system thinking tounderstand and model the behavior and activities of the complexsystems over time [21]. The methodology is based on the feedbackstructure, meaning that decisions with specific goals alter the worldand subsequently lead to new decisions [22]. The process of systemdynamics analysis is comprised of six steps, which are (1) systemunderstanding, (2) problem identification and definition, (3) systemconceptualization, (4) Simulation and validation, (5) policy/decisionanalyzing and improvement, and (6) policy/decision implementation.

Through a review of existing literature among over 1500 pagesof documents and articles including annual reports, detailed gov-ernment, project reports, and published investigations, we haveassessed the US energy sector to (1) define the main problems andobjectives of renewable energy utilization, and (2) identify the keyvariables and policies. Through a review of existing literature, thecausal relationships of renewable energy development and relatedcosts are extracted and variables can be quantitatively examinedvia collecting relevant data. Next section shows the integratedstockeflow 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 andcapacity of electricity generation by renewables in the US during2010e2030. There are five stocks in the proposed model includingcapacity of hydropower electricity, capacity of biomass electricity,capacity of solar electricity, capacity of wind power electricity, andcapacity of geothermal electricity. The capacity of each RER influ-enced by current renewable systems operating and new in-stallations (based on the policies and plans), as well as decreasednumber of RER systems affected by delay time (depreciation). Weassume that the depreciation periods of RER systems are 20 yearsfor solar, 25 years for wind, 25 years for geothermal, 30 years forbiomass plants, and 15 years for small hydropower. The number ofincreased RER systems (rates in the system dynamics model) aredirectly affected by plans and government policies discussed in thesections 3 and 4. Indeed, the investment, O&M, and fuel costs (forBiomass) also depend on the US policies and related technologies.

To develop the quantitative model, the data was collected fromAnnual Energy Outlook 2011 and 2012 prepared by U.S. EnergyInformation Administration (U.S. Department of Energy) [20,23].

Fig. 6 shows the total estimated amount of electricity generatedby RERs in the US during 2010e2030 extracted from themodel. The

h) [20].

&M Variable O&M(including fuel)

Transmissioninvestment

Total systemlevelized cost

9.6 1.5 98.244.3 1.3 115.4

0 3.8 960 4.3 152.70 6.3 2426 2.1 88.9

Fig. 5. System dynamics model of renewable energy development in the US during 2010e2030.

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total amount of electricity generated by RERs should reach to603,166 GWh that means 208,336 GWh new RE systems installa-tion during 2010e2030. According to the defined policy by USdepartment of energy, RE utilization for electricity generation will

Fig. 6. Total electricity generated by renewa

have a fast growth during 2010e2015 (28.5% growth). That ismainly because of new capacities from wind power (56480 GWh)and hydropower (40110 GWh). During 2015e2025, this growth willcontinue with a slower slope as most of the wind and hydropower

ble energy resources in the US (GWh).

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) 153e161158

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 ($).

A. Aslani, K.-F.V. Wong / Renewable Energy 63 (2014) 153e161 159

Table 5Comparing the amount of total, investment, and O&M costs of renewable portfolio and each source in the selected years ($).

Year 2015 2025 2030

Source/costdetail

Total cost Investmentcost

O&M costa Total cost Investment cost O&M costa Total cost Investmentcost

O&M costa

Wind powerb 2,047,490,000 1,980,000 2,045,510,000 2,330,470,000 147,015,000 2,183,455,000 2,430,000,000 147,015,000 2,282,985,000Solar power 187,745,000 336,300 187,408,700 269,576,000 60,197,700 209,378,300 321,322,000 65,000,000 256,322,000Hydropower 1,878,270,000 78,591,800 1,799,678,200 1,894,380,000 36,912,000 1,857,468,000 1,908,880,000 36,900,000 1,871,980,000Biomass 2,469,860,000 339,696,000 2,130,164,000 4,637,000,000 0 4,637,000,000 4,600,000,000 0 4,600,000,000Geothermal 335,973,000 86,064,600 249,908,400 545,944,000 125,567,000 420,377,000 656,848,000 125,000,000 531,848,000Total 6,919,338,000 506,668,700 6,412,669,300 9,677,370,000 369,691,700 9,307,678,300 9,917,050,000 373,915,000 9,543,135,000

a Including fuel cost for biomass.b Compared to 2015e2025, wind power will have a fast growth rate during 2010e2015.

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capacities will be utilized. The total amount of electricity genera-tion from RERs will be increased around 15% during 2015e2025.Finally, during 2025e2030 this growth will continue with slowerrate because of using the capacities for wind, hydropower andbiomass, as well as depreciation of current installations. The mostgrowth during 2025e2030 will be happened by solar andgeothermal technologies.

Figs. 7e11 show the total costs of electricity generation for eachRER. These costs include current RE systems (O&M and fuel costs)and new installations (investment costs) during 2010e2030. AsFig. 7 illustrates, the most investment in the wind power are beinghappened during 2010e2015 (56480 GWh new capacities). Thereduction in the total costs after 2015 is because of the reduction innew 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 fromeach RERs with portfolio of renewables. According to the figure, thetotal costs of RERs utilization will be rise from 6,613,930,000$ (for394,830 GWh utilization) in 2010 to 9,917,050,000$ (for603,166 GWh utilization) in 2030 (53% growth in utilizationcompared to 50% growth in the costs).

Table 5 shows the amount of total, investment and O&M costs ofrenewable portfolio and each source in the three selected years2015, 2025, and 2030.

7. Validation and testing of the model

Testing and validation of the models are very important in thesystem dynamics research. Model testing and validation in thecurrent research are based on the matching the models’ resultswith the real system. The first aim of the model validation is toprovide good and accurate statistical information as decisions maybe 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 realsystem. To test and validate the system dynamics model weimplemented two approach: model structure validation, andmodelbehavior validation [32].

According to the “structure validation”, the structure of systemdynamics model is suitable if it is internally consistent with itsassumptions and the causal structures contains the keys feedbackloops for describing the model and real system. The model imple-mented in the current research responses to these factors from twoviewpoints. First, our system dynamics model describes thebehavior of the system based on the identified variables and causalloop extracted by the researcher’s observation and expert’s opin-ions. Second, it was designed based on the real data, trends, andopinions of the professionals in the energy sector. In particular, theresearchers tried to involve stakeholders and decision makers ofthe policy options from the beginning of the model building.

Therefore, changes in the simulation forecast closely followchanges in the real world systems.

From behavior validation aspect, our system dynamics modelwere checked by two methods; 1) Reviewing the process of themodeling and results and comparingwith historical patterns and 2)testing the results with experts and comparing with the plansdefined by US targets.

8. Conclusion

Today one of the important factors for robust development of aneconomic is security of energy supply [28]. Energy security concernsalong with threats of carbon dioxide emission and consequentlyglobal warming are rapidly rising in importance for developedcountries. To response the challenges, diversification in the energysources is debatedasoneof the important strategiesbypolicymakers.

Due to the energy consumption growth and dependency onfossil fuels in the US, diffusion of electricity/heat generation fromrenewables creates an import part of the US energy policies for thefuture. Our studies show that the US is one of the richest countriesin terms of renewable energy portfolio. However, commercialdevelopment of renewable energy systems is highly dependent tothe utilization costs and government policies. This article discussedabout a system dynamics model to evaluate different costs ofrenewable energy development in the US during 2010e2030. Dueto the role of electricity in energy portfolio of US residential/com-mercial and industries, the analysis focused on electricity genera-tion. Depending to the economic growth, renewable energyutilization would change from 102% increase in the High EconomicGrowth scenario to 62% increase in the Low Economic Growthscenario in the US [23].

As future research, the created system dynamics model can beimplemented in other countries and the results can be comparedwith current work. Further, the total costs of renewable energydevelopment in the US can be compared with other sources alongwith risk analysis to indicate the strength and weaknesses of therenewables in the US. Finally, accurate analysis of each parametersof renewable energy utilization, strategies for cost reduction viaissues such as combination of markets, tax, and regulatory in-centives are subjects that are suggested by authors.

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