Editing Renewable energy (section)

=== Others ===

====Algae fuels====
{{main|Algae fuels}}

Producing liquid fuels from oil-rich (fat-rich) varieties of algae is an ongoing research topic. Various microalgae grown in open or closed systems are being tried including some systems that can be set up in brownfield and desert lands.<ref>{{Cite news|date=2008-10-09|title=In bloom: growing algae for biofuel|url=http://news.bbc.co.uk/2/hi/science/nature/7661975.stm|access-date=2021-12-31}}</ref>

====Space-based solar power====
{{main|space-based solar power}}

There have been numerous proposals for [[space-based solar power]], in which very large satellites with photovoltaic panels would be equipped with [[microwave]] transmitters to beam power back to terrestrial receivers. A 2024 study by the [[NASA]] Office of Science and Technology Policy examined the concept and concluded that with current and near-future technologies it would be economically uncompetitive.<ref>{{Cite book |last1=Rodgers |first1=Erica |url=https://www.nasa.gov/wp-content/uploads/2024/01/otps-sbsp-report-final-tagged-approved-1-8-24-tagged-v2.pdf |title=Space-Based Solar Power |last2=Gertsen |first2=Ellen |last3=Sotudeh |first3=Jordan |last4=Mullins |first4=Carie |last5=Hernandez |first5=Amanda |last6=Le |first6=Hanh Nguyen |last7=Smith |first7=Phil |last8=Joseph |first8=Nikoli |date=January 11, 2024 |publisher=[[NASA]] |location=Washington, DC |department=Office of Technology, Policy and Strategy}}</ref>

====Water vapor====
Collection of static electricity charges from water droplets on metal surfaces is an experimental technology that would be especially useful in [[Developing country|low-income countries]] with relative air humidity over 60%.<ref>{{Cite web|title=Water vapor in the atmosphere may be prime renewable energy source|url=https://techxplore.com/news/2020-06-vapor-atmosphere-prime-renewable-energy.html|access-date=9 June 2020|website=techxplore.com|archive-date=9 June 2020|archive-url=https://web.archive.org/web/20200609172357/https://techxplore.com/news/2020-06-vapor-atmosphere-prime-renewable-energy.html|url-status=live}}</ref>

====Nuclear energy====
[[Breeder reactor]]s could, in principle, depending on the fuel cycle employed, extract almost all of the energy contained in [[uranium]] or [[thorium]], decreasing fuel requirements by a factor of 100 compared to widely used once-through [[light water reactors]], which extract less than 1% of the energy in the actinide metal (uranium or thorium) mined from the earth.<ref name="Argonne">{{cite web |title=Pyroprocessing Technologies: Recycling Used Nuclear Fuel For A Sustainable Energy Future |publisher=Argonne National Laboratory |url=https://www.anl.gov/sites/www/files/2023-09/Recycling%20Used%20Nuclear%20Fuel%20Brochure.pdf |url-status=live |archive-url=https://web.archive.org/web/20130219051536/http://www.ne.anl.gov/pdfs/12_Pyroprocessing_bro_5_12_v14%5B6%5D.pdf |archive-date=19 February 2013}}</ref> The high fuel-efficiency of breeder reactors could greatly reduce concerns about fuel supply, energy used in mining, and storage of [[radioactive waste]]. With [[seawater uranium extraction]] (currently too expensive to be economical), there is enough fuel for breeder reactors to satisfy the world's energy needs for 5 billion years at 1983's total energy consumption rate, thus making nuclear energy effectively a renewable energy.<ref name="sustainablenuclear">{{cite web |title=Breeder reactors: A renewable energy source |last=Cohen |first=Bernard L. |publisher=Argonne National Laboratory |url=http://www.sustainablenuclear.org/PADs/pad11983cohen.pdf |access-date=25 December 2012 |url-status=dead |archive-url=https://web.archive.org/web/20130114062518/http://sustainablenuclear.org/PADs/pad11983cohen.pdf |archive-date=14 January 2013}}</ref><ref>Weinberg, A. M., and R. P. Hammond (1970). "Limits to the use of energy," ''Am. Sci.'' 58, 412.</ref> In addition to seawater the average crustal granite rocks contain significant quantities of uranium and thorium with which breeder reactors can supply abundant energy for the remaining lifespan of the sun on the main sequence of stellar evolution.<ref>{{cite web |title=There's Atomic Energy in Granite |date=8 February 2013 |url=https://www.nuenergy.org/theres-atomic-energy-in-granite/}}</ref>

==== Artificial photosynthesis ====
{{main|Artificial photosynthesis}}

Artificial photosynthesis uses techniques including [[nanotechnology]] to store solar electromagnetic energy in chemical bonds by splitting water to produce hydrogen and then using carbon dioxide to make methanol.<ref>Collings AF and Critchley C (eds). Artificial Photosynthesis{{spaced ndash}}From Basic Biology to Industrial Application (Wiley-VCH Weinheim 2005) p ix.</ref> Researchers in this field strived to design molecular mimics of photosynthesis that use a wider region of the solar spectrum, employ catalytic systems made from abundant, inexpensive materials that are robust, readily repaired, non-toxic, stable in a variety of environmental conditions and perform more efficiently allowing a greater proportion of photon energy to end up in the storage compounds, i.e., carbohydrates (rather than building and sustaining living cells).<ref name="faunce">{{cite journal |last1=Faunce |first1=Thomas A. |last2=Lubitz |first2=Wolfgang |author-link2=Wolfgang Lubitz |last3=Rutherford |first3=A. W. (Bill) |last4=MacFarlane |first4=Douglas |last5=Moore |first5=Gary F. |last6=Yang |first6=Peidong |last7=Nocera |first7=Daniel G. |last8=Moore |first8=Tom A. |last9=Gregory |first9=Duncan H. |last10=Fukuzumi |first10=Shunichi |last11=Yoon |first11=Kyung Byung |last12=Armstrong |first12=Fraser A. |last13=Wasielewski |first13=Michael R. |last14=Styring |first14=Stenbjorn |year=2013 |title=Energy and environment policy case for a global project on artificial photosynthesis |journal=Energy & Environmental Science |publisher=RSC Publishing |volume=6 |issue=3 |page=695 |doi=10.1039/C3EE00063J|bibcode=2013EnEnS...6..695F }}</ref> However, prominent research faces hurdles, Sun Catalytix a MIT spin-off stopped scaling up their prototype fuel-cell in 2012 because it offers few savings over other ways to make hydrogen from sunlight.<ref>{{cite journal |author=jobs |date=23 May 2012 |title='Artificial leaf' faces economic hurdle: Nature News & Comment |url=http://www.nature.com/news/artificial-leaf-faces-economic-hurdle-1.10703 |url-status=live |journal=Nature News |publisher=Nature.com |doi=10.1038/nature.2012.10703 |s2cid=211729746 |archive-url=https://web.archive.org/web/20121201123957/http://www.nature.com/news/artificial-leaf-faces-economic-hurdle-1.10703 |archive-date=1 December 2012 |access-date=7 November 2012 |doi-access=free}}</ref> 

Recent research emphasizes that while artificial photosynthesis shows promise in splitting water to generate hydrogen, its broader significance lies in the ability to produce dense, carbon-based solar fuels suitable for transport applications, such as aviation and long-haul shipping. These fuels, if derived from carbon dioxide and water using sunlight, could close the carbon loop and reduce reliance on fossil-based hydrocarbons. However, realizing this potential requires overcoming major technical hurdles, including the development of efficient, durable catalysts for water oxidation and CO₂ reduction, and careful attention to land use and public perception.<ref>{{Cite journal |last=Cogdell |first=Richard J |first2=Brotosudarmo ,Tatas HP |first3=Gardiner ,Alastair T |first4=Sanchez ,Pedro M |last5=and Cronin |first5=Leroy |date=2010-11-01 |title=Artificial photosynthesis – solar fuels: current status and future prospects |url=https://www.tandfonline.com/doi/full/10.4155/bfs.10.62 |journal=Biofuels |volume=1 |issue=6 |pages=861–876 |doi=10.4155/bfs.10.62 |issn=1759-7269}}</ref>