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Solar Power

We recommend research and development programs into concentrated solar, advanced solar cells, and luminescent solar concentrators, but not space-based solar power. These solutions are detailed below.

Costs

While there are outliers, utility-scale solar photovoltaics typically produce power at a competitive 4-6 ¢/kWh. Solar PV technologies that are still under development, such as organic PV and perovskites, may achieve this range as well.

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Estimates of mainstream PV technology from the Electric Power Research Institute 1, International Renewable Energy Agency 2, Kost et al. 3, Lazard 4, Logan et al. 5, OpenEI6, EIA 7. Projected costs from perovskite and organic PVs are given by Cai et al. 8 and Guo and Min 9 respectively.

Problem:
Need to Achieve Net Zero Emissions
Solution:
Accelerate Investment into Solar Energy

Following are estimated costs of concentrated solar power, distributed solar, and several emerging and speculative non-PV technologies.

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For concentrated solar power, see the Electric Power Research Institute 1, International Renewable Energy Agency 2, Lazard 4, Logan et al. 5, OpenEI 6, EIA 7, World Energy Council10. For distributed PV, see EPRI 1, Guo et al. 11, Kost et al. 3, and Lazard 4. For concentrated PV, see Phillips et al. 12. For solar updraft towers, see Schlaich Bergermann Solar GmbH 13 and Zhu et al. 14. For space-based solar, see Mankins 15.

Distributed Solar

Distributed (e.g. rooftop) solar has the advantage of not requiring dedicated land, but the costs of installation logistics and grid management are higher. In the United States, rooftop solar could in theory provide 1432 terawatt-hours 16, of which 297 TWh would be economical 17. These figures are 34% and 7% of U.S. electricity production, respectively 18. About a third of US solar comes from distributed sources 19.

As the price of solar cells decreases, soft (non-hardware) costs of the system become more important.

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Hardware and soft (non-hardware) costs of solar PVs as of 2018, given by Fu, Feldman, Margolis 20.

Distributed energy sources complete in the retail electricity market, not the wholesale market, and thus the threshhold for grid parity is higher. In 2015, Deutsche Bank found that rooftop solar has achieved grid parity in half the countries surveyed and 14 U.S. states 21.

Regulatory reforms could cut US solar soft costs. A residential solar installation in the United States is over twice as expensive as in Australia, due primarily to the lengthier and costlier installation process mandated by the U.S. National Electrical Code, as well as higher U.S. permitting costs 22.

Problem:
High Cost of Rooftop Solar
Solution:
Regulatory Reform - U.S.

Solar Roads

Several pilot projects have been attempted placing solar panels on roadways. Test results have been disappointing and the concept is not likely to be feasible 23.

Environmental and Externalized Impacts

Solar power shows the following median environmental impacts.

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Environmental impacts of solar power, assessed on a per-kWh basis. While solar power does not emit greenhouse gases directly, there are indirect emissions arising from the manufacture, distribution, and maintenance of equipment, as estimated by Schlömer et al. 24 and valued at $50/ton CO2-equivalent 25. Non-greenhouse gas pollution impacts are estimated by Samadi 26, and land use is estimated by Ong et al. 27. Among solar thermal systems, tower systems are the most land-efficient 27.

To put the land use issue into perspective, supplying all the electricity demand of the United States with solar power would require about 33,000 square kilometers, or 0.4% of all land in the U.S. 28. This is close to what is currently disturbed by coal mining, less than the area taken by major roads, and about half of what is devoted to growing corn ethanol 28.

The manufacture of solar cells requires toxic heavy metals and imposes local habitat disruption 29. There are additional costs, unquantified above, in the disposal of panels at the end of their life 30.

Due to the intermittent nature of solar power, grid integration costs have been estimated at 1.5 ¢/kWh 31.

The aluminum to manufacture solar panels has been estimated to carry a greenhouse gas gost of about 2.2 g/kWh, about 0.011 ¢/kWh at $50/ton, assuming the panels last for 20 years and operate at 30% capacity factor 32.

Solar Thermal

A solar thermal plant, including concentrating solar power (CSP), concentrates sunlight for the production of heat, which can then be used either directly for industrial applications or to generate electricity. As of 2018, there is about 1.5% as much solar thermal electrical generation capacity as solar PV 33. Modern CSP plants include thermal storage, often in the form of molten salt, to reduce intermittency 34.

A solar thermal plant can produce heat for industrial processes. Modern solar thermal could, in priciple, supply up to about half of industrial heat demand, though at significantly higher cost than fossil fuel options. Higher temperature CSP plants for direct heat, which would be suitable for metallic minerals and thermochemical hydrogen production, are under development 35.

Interest in solar thermal has diminished due to the decrease in PV prices. Even with subsidies, CSP is not competitive in the United States 28. By its nature, CSP installations need to be large to be economical. This makes it difficult for private investors to build experimental projects, and a significant public R&D gap is in building pilot projects to test new designs 28.

Problem:
Cost of Concentrated Solar
Solution:
Concentrated Solar R&D - U.S.

Advanced Solar Cells

The SunShot Vision study recognizes that their aggressive cost reduction goals may require commercialization of new technologies 36. As the cells themselves are now a small portion of the cost of a solar installation, the most important advances in solar cell technology are improved efficiency to reduce system costs.

The following are state of the art solar cell efficiencies, current efficiencies for utility solar, current efficiencies for distributed solar, and conversion efficiency of plants to bioenergy.

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State of the art solar cell efficiency reported by the National Renewable Energy Laboratory 37, current utility efficiency from Bolinger and Seel 38, distributed efficiency from Fu et al. 20, algae conversion efficiency from Larkum 39, and C3 and C4 crops from Sarkar and Shimizu 40. It should be noted that biomass, the energy product of plants, is a lower quality fuel than electricity.

The dominant commercial solar technology is crystalline silicon, while CdTe (cadmium telluride), CIGS (copper indium gallium selenide), and amorphous silicon are the main thin film technologies. Multijunction cells are used in spacecraft and concentrator photovoltaics.

Any solar technology that relies on rare materials may be unable to scale to provide a large fraction of the world's electricity. Therefore, R&D should emphasize technologies that use Earth-abundant materials, such as CZTS (copper zinc tin sulfide), rather than tellerium, gallium, indium, or selenium 28. Among solar technologies under development, perovskites have advanced rapidly and may be the most promising 41, with a potential LCOE of 3.5-4.9 ¢/kWh 42.

Problem:
Cost of Advanced Solar Cells
Solution:
Advanced Solar Cell R&D

Emerging Solar Technology

There are several advanced solar concepts under development. See also our analysis of space-based solar power in the context of resources from space.

Concentrating Photovoltaics

Concentrating PV (CPV) is a method of solar energy capture in which an optical device concentrates sunlight at a rate of anywhere from 2-1200 suns onto a high-efficiency photovoltaic cell. Multijunction cells, which harvest a larger portion of the solar spectrum, may achieve efficiencies as high as 50% 43, saving land relative to conventional PV 44. The long-term economics may be more promising than conventional PV 12, but deployment has fallen since 2014 45. Challenges include reliability of the optics and the tracking system and longevity of cells under high radiation 44.

Problem:
Cost of Concentrating PV
Solution:
Concentrating PV R&D

For a large-scale CPV industry, availability of germanium for high-efficiency multijunction cells may also be an issue 12.

Luminescent Solar Concentrators

A luminescent solar concentrator (LSC, also called building-integrated solar) is a flat device that collects solar energy and redirects it to a solar cell. Unlike traditional solar collectors, an LSC can function with diffuse sunlight. This allows harvesting of energy on cloudy days, dispensing of tracking systems, and reduction of intermittency 46. LSC could be especially useful in building integration 47. The technology is not yet commercially available.

Problem:
Cost of Luminescent Solar Concentrator Technology
Solution:
LSC R&D

Solar Updraft Tower

A solar updraft tower is a proposed design that uses concentrated sunlight to heat the air in a base structure, causing the air to rise through a chimney and turn a turbine. After the failed Manzanares experiment in the 1980s, there have been no physical prototypes 48.

For Further Reading

Detailed IEEE Spectrum article on JAXA's space solar program.

References

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  2. International Renewable Energy Agency. "Renewable Power Generation Costs in 2017". January 2018. ↩ ↩2

  3. Kost, C., Shammugam, S., Jülch, V., Nguyen, H., Schlegl, T. "Levelized Cost of Electricity: Renewable Energy Technologies". Fraunhofer Institute for Solar Energy Systems ISE. March 2018. ↩ ↩2

  4. Lazard. "Lazard's Levelized Cost of Energy Analysis - Version 12.0". November 2018. ↩ ↩2 ↩3

  5. Logan, J. et al. "Electricity Generation Baseline Report". National Renewable Energy Laboratory. January 2017. ↩ ↩2

  6. OpenEI. "Transparent Cost Database". Accessed May 11, 2019. ↩ ↩2

  7. U.S. Energy Information Administration. "Levelized Cost and Levelized Avoided Cost of New Generation". February 2019. ↩ ↩2

  8. Cai, M., Wu. Y., Chen, H., Yang, X., Qiang, Y., Han, L. "Cost‐Performance Analysis of Perovskite Solar Modules". Advanced Science 4(1). January 2017. ↩

  9. Guo, J., Min, J. "A Cost Analysis of Fully Solution‐Processed ITO‐Free Organic Solar Modules". Advanced Energy Materials. November 2018. ↩

  10. World Energy Council. "World Energy Resources, 2013 Survey". 2013. ↩

  11. Guo, S., Zhao, H., Zhao, H. "The Most Economical Mode of Power Supply for Remote and Less Developed Areas in China: Power Grid Extension or Micro-Grid?". Sustainability 9(6), p. 910. 2017. ↩

  12. Phillips, S., Bett, A., Horowitz, K., Kurtz, S. "Current Status of Concentrator Photovoltaic (CPV) Technology". Fraunhofer Institute for Solar Energy Systems, National Renewable Energy Laboratory. January 2015. ↩ ↩2 ↩3

  13. Schlaich Bergermann Solar GmbH. "Solar Updraft Tower". October 2011. ↩

  14. Zhu, Y., Zhai, R., Yang, Y., Reyes-Belmonte, M. "Techno-Economic Analysis of Solar Tower Aided Coal-Fired Power Generation System". Energies. September 2017. ↩

  15. Mankins, J. "New Developments in Space Solar Power". National Space Society Space Settlement Journal. December 2017. ↩

  16. Gagnon, P., Margolis, R., Melius, J., Phillips, C., Elmore, R. "Rooftop Solar Photovoltaic Technical Potential in the United States: A Detailed Assessment". National Renewable Energy Laboratory. January 2016. ↩

  17. Brown, A. et al. "Estimating Renewable Energy Economic Potential in the United States: Methodology and Initial Results". National Renewable Energy Laboratory. August 2016. ↩

  18. U.S. Energy Information Administration. "What is U.S. electricity generation by energy source?". Accessed July 30, 2019. ↩

  19. U.S. Energy Information Administration. "Table 1.17.B. Net Generation from Solar Photovoltaic". Electric Power Monthly. Accessed July 30, 2019. ↩

  20. Fu, R., Feldman, D., Margolis, R. "U.S. Solar Photovoltaic System Cost Benchmark: Q1 2018". National Renewable Energy Laboratory. November 2018. ↩ ↩2

  21. Shah, V., Booream-Phelps, J. "Crossing the Chasm". Deutsche Bank. February 2015. ↩

  22. Birch, A. "How to Halve the Cost of Residential Solar in the US". Greentech Media. January 2018. ↩

  23. Ryan, D. "Solar panels replaced tarmac on a motorway. Here are the results.". Ars Technica. September 2018. ↩

  24. Schlömer S., T. Bruckner, L. Fulton, E. Hertwich, A. McKinnon, D. Perczyk, J. Roy, R. Schaeffer, R. Sims, P. Smith, and R. Wiser. Annex III: Technology-specific cost and performance parameters. In Climate Change 2014: Mitigation of Climate Change. Contribution of Working Group III to the Fifth Assessment Report of the Intergovernmental Panel on Climate Change [Edenhofer, O., R. Pichs-Madruga, Y. Sokona, E. Farahani, S. Kadner, K. Seyboth, A. Adler, I. Baum, S. Brunner, P. Eickemeier, B. Kriemann, J. Savolainen, S. Schlömer, C. von Stechow, T. Zwickel and J.C. Minx (eds.)]. Cambridge University Press, Cambridge, United Kingdom and New York, NY, USA. 2014. ↩

  25. Interagency Working Group on Social Cost of Carbon. "Technical Support Document: Technical Update of the Social Cost of Carbon for Regulatory Impact Analysis". Under Executive Order 12866, United States Government. August 2016. ↩

  26. Samadi, S. "The Social Costs of Electricity Generation-Categorising Different Types of Costs and Evaluating Their Respective Relevance". Energies 10(3), pp. 356. 2017. ↩

  27. Ong, S., Campbell, C., Denholm, P., Margolis R., Heath, G. "Land-Use Requirements for Solar Power Plants in the United States". June 2013. ↩ ↩2

  28. Massachusetts Institute of Technology. "The Future of Solar". Energy Initiative. 2015. ↩ ↩2 ↩3 ↩4 ↩5

  29. Aman, M. et al. "A review of Safety, Health and Environmental (SHE) issues of solar energy system". Renewable and Sustainable Energy Systems 41, pp. 1190-1204. January 2015. ↩

  30. Jinhui, Y., Tan, Q., Peters, A., Yang, C. "Global status of recycling waste solar panels: A review". Waste Management 75, pp. 450-458. May 2018. ↩

  31. Organization for Economic Co-Operation and Development Nuclear Energy Agency. "Nuclear Energy and Renewables: System Effects in Low-carbon Electricity Systems". 2012. ↩

  32. Lennon A., Lunardi M., Hallam B., Dias P. R. "The aluminium demand risk of terawatt photovoltaics for net zero emissions by 2050". Nature Sustainability 5(4), pp. 357-363. April 2022. ↩

  33. International Energy Agency. "Solar energy". Accessed July 31, 2019. ↩

  34. International Energy Agency. "Technology Roadmap - Solar Thermal Electricity, 2014 Edition". 2014. ↩

  35. SOLPART. "Home Page". Accessed July 31, 2019. ↩

  36. U.S. Department of Energy. "Sunshot Vision Study". February 2012. ↩

  37. National Renewable Energy Laboratory. "Best Research-Cell Efficiency Chart". Accessed July 31, 2019. ↩

  38. Bolinger, M., Seel, J. "Utility-Scale Solar: Empirical Trends in Project Technology, Cost, Performance, and PPA Pricing in the United States - 2018 Edition". Lawrence Berkeley National Laboratory. September 2018. ↩

  39. Larkum, A. "Limitations and prospects of natural photosynthesis for bioenergy production". Current Opinion in Biotechnology 21(3), pp. 271-276. June 2010. ↩

  40. Sarkar, D., Shimizu, K. "An overview on biofuel and biochemical production by photosynthetic microorganisms with understanding of the metabolism and by metabolic engineering together with efficient cultivation and downstream processing". Bioresources and Bioprocessing 2(17). April 2015. ↩

  41. Extance, A. "The reality behind solar power’s next star material". Nature 570, pp. 429-432, News Feature. June 2019. ↩

  42. Cai, M., Wu, Y., Chen, H., Yang, X., Qiang, Y., Han, L. "Cost‐Performance Analysis of Perovskite Solar Modules". Advanced Science 4(1). September 2016. ↩

  43. International Renewable Energy Agency. "Solar Photovoltaics". Renewable Energy Technologies: Cost Analysis Series, Volume 1: Power Sector. June 2012. ↩

  44. Kurtz, S. "Opportunities and Challenges for Development of a Mature Concentrating Photovoltaic Power Industry". National Renewable Energy Laboratory. November 2012. ↩ ↩2

  45. Fraunhofer Institute for Solar Energy Systems, ISE. "Photovoltaics Report". March 2019. ↩

  46. Rowan, B., Wilson, L, , Richards, B. "Advanced Material Concepts for Luminescent Solar Concentrators". IEEE Journal of Selected Topics in Quantum Electronics, Vol. 14, No. 5. September/October 2008. ↩

  47. Meinardi, F., Bruni, F., Brovelli, S. "Luminescent solar concentrators for building-integrated photovoltaics". Nature Reviews Materials 2: Article Number 17072. November 2017. ↩

  48. Boretti, A., Al-Zubaidy, S. "Maturity assessment of the solar updraft tower technology". Renewable Energy Focus 27, pp. 135-144. December 2018. ↩