Solar updraft tower

Power output depends primarily on two factors: collector area and chimney height. A larger area collects and warms a greater volume of air to flow up the chimney; collector areas as large as {{convert|7|km|mi|1}} in diameter have been discussed. A larger chimney height increases the pressure difference via the stack effect; chimneys as tall as {{convert|1000|m|ft|0}} have been discussed.{{cite book|title=Renewable energy technology, economics, and environment|date=2007|publisher=Springer|location=Berlin|isbn=978-3-540-70949-7|page=223|editor=Martin Kaltschmitt|editor-link=Martin Kaltschmitt|editor2=Wolfgang Streicher|editor3=Andreas Wiese}}

Heat is stored inside the collector area allowing SUTs to operate 24 hours a day. The ground beneath the solar collector, water in bags or tubes, or a saltwater thermal sink in the collector could add thermal capacity and inertia to the collector. Humidity of the updraft and release of the latent heat of condensation in the chimney could increase the energy flux of the system.{{cite web|url=http://www.greenidealive.org/110599/466/solar-pond-tower-for-5-ct/kwh.html |title=Solar pond tower for 5 €ct/kWh|publisher=GreenIdeaLive |access-date=2011-09-11}}{{cite journal |doi=10.1115/1.1823493 |title=Design of Commercial Solar Updraft Tower Systems—Utilization of Solar Induced Convective Flows for Power Generation |journal=Journal of Solar Energy Engineering |volume=127 |pages=117–24 |year=2005 |last1=Schlaich |first1=Jörg |last2=Bergermann |first2=Rudolf |last3=Schiel |first3=Wolfgang |last4=Weinrebe |first4=Gerhard }}

Turbines with a horizontal axis can be installed in a ring around the base of the tower, as once planned for an Australian project and seen in the diagram above; or—as in the prototype in Spain—a single vertical axis turbine can be installed inside the chimney.

A nearly negligible amount of carbon dioxide is produced as part of operations, while construction material manufacturing can create emissions.{{cite conference |last1=Niemann |first1=H.-J. |last2=Lupi |first2=F. |last3=Hoeffer |first3=R. |last4=Hubert |first4=W. |last5=Borri |first5=C. |conference=5th European & African conference on wind engineering |location=Florence Italy |date=July 2009 |title=The Solar Updraft Power Plant: Design and Optimization of the Tower for Wind Effects |publisher=Firenze University Press |url=https://www.iawe.org/Proceedings/5EACWE/136.pdf |doi=10.1400/116481 }} Net energy payback is estimated to be 2–3 years.

Since solar collectors occupy significant amounts of land, deserts and other low-value sites are most likely. Improvements in the solar heat collection efficiency by using unglazed transpired collector can significantly reduce the land required for the solar array.

A small-scale solar updraft tower may be an attractive option for remote regions in developing countries.{{cite journal |doi=10.1016/j.fuel.2006.04.029 |title=The potential of solar chimney for application in rural areas of developing countries |journal=Fuel |volume=85 |issue=17–18 |pages=2561–6 |year=2006 |last1=Onyango |first1=F |last2=Ochieng |first2=R |bibcode=2006Fuel...85.2561O }}{{cite journal |doi=10.1016/S0960-1481(02)00227-6 |id={{INIST|14497497}} |title=Case study of solar chimney power plants in Northwestern regions of China |journal=Renewable Energy |volume=28 |issue=8 |pages=1295–304 |year=2003 |last1=Dai |first1=Y.J |last2=Huang |first2=H.B |last3=Wang |first3=R.Z |bibcode=2003REne...28.1295D }} The relatively low-tech approach could allow local resources and labour to be used for construction and maintenance.

Locating a tower at high latitudes could produce up to 85 percent of the output of a similar plant located closer to the equator, if the collection area is sloped significantly toward the equator. The sloped collector field, which also functions as a chimney, is built on suitable mountainsides, with a short vertical chimney on the mountaintop to accommodate the vertical axis air turbine. The results showed that solar chimney power plants at high latitudes may have satisfactory thermal performance.{{cite journal |doi=10.1016/j.solener.2005.01.003 |id={{INIST|17275884}} |title=Solar chimney power plants for high latitudes |journal=Solar Energy |volume=79 |issue=5 |pages=449–58 |year=2005 |last1=Bilgen |first1=E. |last2=Rheault |first2=J. |bibcode=2005SoEn...79..449B }}

File:Smoke-jack.jpg

A chimney turbine was envisioned as a smoke jack, and illustrated 500 years ago by Leonardo da Vinci. An animal spitted above a fire or in an oven could be turned by a vertical axis turbine with four angled vanes in the chimney updraft.

Alfred Rosling Bennett published the first patent describing a "Convection Mill" in 1896.{{Cite patent|country=GB|number=189608711|pubdate=1897-04-24|title=An improved differential temperature air motor, adapted for scientific applications, for philosophical toys, and for advertising and other purposes|inventor1-last=Bennett|inventor1-first=Alfred Rosling}} Even if in the title of the patent and in the claims the word "Toy" clearly appears and even if in the overall description made inside the patent it is evident that the idea was to produce small devices, in page 3 at lines 49–54 Bennett envisions much larger devices for bigger scale applications. A model of this "convection mill", built in 1919 by Albert H. Holmes & Son (London) to demonstrate the phenomenon of convection currents, is on display in the Science Museum, London.

In 1903, Isidoro Cabanyes, a colonel in the Spanish army, proposed a solar chimney power plant in the magazine La energía eléctrica.{{cite web |last1=Lorenzo |first1=E. |language=es |url=http://www.fotovoltaica.com/chimenea.pdf |title=Las chimeneas solares:De una propuesta española en 1903 a la Central de Manzanares |publisher=De Los Archivos Históricos De La Energía Solar |url-status=dead |archive-url=https://web.archive.org/web/20200206105819/http://www.fotovoltaica.com/chimenea.pdf |archive-date=2020-02-06 }} Another early description was published in 1931 by German author Hanns Günther.{{cite book |last=Günther |first=Hanns | author-link=Walter de Haas | date=1931| title=In hundert Jahren — Die künftige Energieversorgung der Welt| location=Stuttgart| publisher=Kosmos, Gesellschaft der Naturfreunde}} Beginning in 1975, Robert E. Lucier applied for patents on a solar chimney electric power generator; between 1978 and 1981 patents (since expired) were granted in Australia,{{Cite patent|country=AU|number=499934|pubdate=1977-08-18|title=Apparatus for converting solar to electrical energy|inventor1-last=Lucier|inventor1-first=R.}} Canada,{{Cite patent|country=CA|number=1023564|pubdate=1978-01-03|title=Utilization of solar energy|inventor1-last=Lucier|inventor1-first=Robert E.}} Israel,{{Cite patent|country=IL|number=50721|pubdate=1979-12-30|title=System and apparatus for converting solar heat to electrical energy|inventor1-last=Lucier|inventor1-first=R.}} and the US.{{Cite patent|number=4275309|country=US|pubdate=1981-06-23|title=System for converting solar heat to electrical energy|inventor1-last=Lucier|inventor1-first=Robert E.}}

In 1926 Prof Engineer Bernard Dubos proposed to the French Academy of Sciences the construction of a Solar Aero-Electric Power Plant in North Africa with its solar chimney on the slope of a large mountain.{{Cite patent|country=US|number=7026723|pubdate=2006-04-11|title=Air filtering chimney to clean pollution from a city and generate electric power|assign1=Handels und Finanz AG|inventor1-last=Moreno|inventor1-first=Mauricio Rodolfo}} {{Citation needed span|text=A mountainside updraft tower can also function as a vertical greenhouse.|date=August 2012}}

In 1956, Edgard Nazare, after observing several dust devils in the southern Sahara, filed his first patent in Algiers on the artificial cyclone generator. This patent was re-filed later in Paris {{Cite patent|country=FR|number=1439849|pubdate=1966-05-27|title=Générateur de cyclones artificiels|inventor1-last=Nazare|inventor1-first=Edgard}}

File:Solar Chimney Manzanares view through the polyester collector roof.jpg

In 1982, a small-scale experimental model of a solar draft tower{{cite news |title=Solar Updraft Tower Pilot Plant Manzanares |url=https://www.sbp.de/en/project/solar-chimney-pilot-plant-manzanares/ |work=Schlaich Bergermann Partner }} was built in Manzanares, Ciudad Real, 150 km south of Madrid, Spain at {{coord|39|02|34.45|N|3|15|12.21|W|type:landmark|name=Manzanares Solar Updraft Tower}}. The power plant operated for approximately eight years. The tower's guy-wires were not protected against corrosion and failed due to rust and storm winds. The tower blew over and was decommissioned in 1989.{{cite journal |doi=10.1016/S0038-092X(03)00102-6 |id={{INIST|15396794}} |title=Advances in solar thermal electricity technology |journal=Solar Energy |volume=76 |issue=1–3 |pages=19–31 |year=2004 |last1=Mills |first1=D. |bibcode=2004SoEn...76...19M }}

File:AWK von La Solana aus.JPG

Inexpensive materials were used in order to evaluate their performance. The solar tower was built of iron plating only {{convert|1.25|mm|in}} thick under the direction of a German engineer, Jörg Schlaich. The project was funded by the German government.{{cite journal |doi=10.1080/01425918308909911 |title=Solar Chimneys Part I: Principle and Construction of the Pilot Plant in Manzanares |journal=International Journal of Solar Energy |volume=2 |issue=1 |pages=3–20 |year=2007 |last1=Haaf |first1=W. |last2=Friedrich |first2=K. |last3=Mayr |first3=G. |last4=Schlaich |first4=J. |bibcode=1983IJSE....2....3H }}{{cite journal |doi=10.1080/01425918408909921 |title=Solar Chimneys Part II: Preliminary Test Results from the Manzanares Pilot Plant |journal=International Journal of Solar Energy |volume=2 |issue=2 |pages=141–61 |year=2007 |last1=Haaf |first1=W. |bibcode=1984IJSE....2..141H }}

The chimney had a height of {{convert|195|m|ft}} and a diameter of {{convert|10|m|ft}} with a collection area (greenhouse) of {{convert|4.6|ha}} and a diameter of {{convert|244|m|ft}}, obtaining a maximum power output of about 50 kW. Various materials were used for testing, such as single or double glazing or plastic (which turned out not to be durable enough). One section was used as an actual greenhouse. During its operation, 180 sensors measured inside and outside temperature, collecting humidity and wind speed data on a second-by-second basis.Schlaich J, Schiel W (2001), "Solar Chimneys", in RA Meyers (ed), Encyclopedia of Physical Science and Technology, 3rd Edition, Academic Press, London. {{ISBN|0-12-227410-5}} {{cite web |url= http://www.solarmillennium.de/pdf/SolarCh.pdf |title= download |url-status= dead |archive-url= https://web.archive.org/web/20070615183950/http://www.solarmillennium.de/pdf/SolarCh.pdf |archive-date= 2007-06-15 }} {{small|(180 KB)}} This experimental setup did not sell energy.

In December 2010, a tower in Jinshawan in Inner Mongolia, China started operation, producing 200 kilowatts.{{cite web |url=http://www.gov.cn/english/2010-12/28/content_1773883.htm |title=China's first solar chimney plant starts operating in desert |publisher=Gov.cn |date=2010-12-28 |access-date=2011-09-11 |archive-date=2012-01-06 |archive-url=https://web.archive.org/web/20120106202639/http://www.gov.cn/english/2010-12/28/content_1773883.htm |url-status=dead }}{{cite web |author=www.margotweb.net |url=http://www.solar-chimney.biz/new.php?PHPSESSID=160852743538f135a1ef6e9c58c983a4 |title=NEW about solar chimney power plants |publisher=Solar-chimney.biz |date=2010-09-30 |access-date=2011-09-11 |url-status=dead |archive-url=https://archive.today/20120910185933/http://www.solar-chimney.biz/new.php?PHPSESSID=160852743538f135a1ef6e9c58c983a4 |archive-date=2012-09-10 }} The 1.38 billion RMB (USD 208 million) project was started in May 2009. It was intended to cover {{convert|277|ha|acre}} and produce 27.5 MW by 2013, but had to be scaled back. The solar chimney plant was expected to improve the climate by covering loose sand, restraining sandstorms.{{cite web |url=http://news.xinhuanet.com/english2010/china/2010-12/27/c_13666710.htm |title=Xianha: China's first solar chimney plant starts operating in desert |publisher=News.xinhuanet.com |date=2010-12-27 |access-date=2011-09-11 |url-status=dead |archive-url=https://web.archive.org/web/20120730051352/http://news.xinhuanet.com/english2010/china/2010-12/27/c_13666710.htm |archive-date=2012-07-30 }} Critics have said that the 50m tall tower is too short to work properly and that it was a mistake to use glass in metal frames for the collector, as many of them cracked and shattered in the heat.

File:SolarChimneyManzanares view from 8km south direction.JPG

A proposal to construct a solar updraft tower in Fuente el Fresno, Ciudad Real, Spain, entitled Ciudad Real Torre Solar would be the first of its kind in the European Union{{cite news |first=J.V. |last=Muñoz-Lacuna |title=Ciudad Real tendrá una torre solar que doblará en alturaa las Torres Gemelas |url=http://www.lasprovincias.es/valencia/pg060213/prensa/noticias/Espana/200602/13/VAL-ESP-051.html |work=lasprovincias.es |date=13 February 2006 |access-date=26 March 2007|language=es}} and would stand {{convert|750|m|ft}} tall,{{cite web |url=http://skyscraperpage.com/cities/?buildingID=46210 |title=Ciudad Real Torre Solar, Ciudad Real - SkyscraperPage.com |access-date=27 July 2014 |date=2007 |work=SkyscraperPage.com}} covering an area of {{convert|350|ha|acres}}.{{cite news|first=Julio |last=Plaza |title=La Torre Solar |url=http://www.hispalibertas.com/noticias/2006/02/28/la-torre-solar.html |work=HispaLibertas |date=28 February 2006 |access-date=26 March 2007 |archive-url=https://web.archive.org/web/20070427090637/http://www.hispalibertas.com/noticias/2006/02/28/la-torre-solar.html |archive-date=27 April 2007 |language=es |url-status=dead }}

It is expected to produce 40 MW.{{cite web |url=http://urbanity.blogsome.com/2006/02/13/torre-solar-de-750-metros-en-ciudad-real/ |title=Torre Solar de 750 metros en Ciudad Real |access-date=27 March 2007 |date=13 February 2006 |work=Urbanity.es |language=es |url-status=dead |archive-url=https://web.archive.org/web/20070427095503/http://urbanity.blogsome.com/2006/02/13/torre-solar-de-750-metros-en-ciudad-real/ |archive-date=27 April 2007 }} At that height, it would be nearly twice as tall as the Belmont TV Mast, which was once the tallest structure in the European Union, before being shortened by 24 meter.{{cite web |url=http://www.aerialsandtv.com/belmonttx.html |title=Belmont Transmitter |access-date=26 March 2007 |work=A.T.V (Aerials and Television)}}

File:Solar Chimney Manzanares-view of the tower through the collector glass roof.JPG

In 2001, EnviroMission{{cite web|last=Davey |first=R |title=New Green energy technology launches |publisher=Australian Securities Exchange |date=6 August 2001 |url=http://www.asx.com.au/asx/statistics/showSignalgDetail.do?issuerId=4715&announcementId=414439 |access-date=31 March 2007 |archive-url=https://web.archive.org/web/20070926225534/http://www.asx.com.au/asx/statistics/showSignalgDetail.do?issuerId=4715&announcementId=414439 |archive-date=26 September 2007 |url-status=dead }} proposed to build a solar updraft tower power generating plant known as Solar Tower Buronga near Buronga, New South Wales.{{cite news | last = Woody | first = Todd | title = Tower of Power | publisher = CNN | date = 2 October 2006 | url = https://money.cnn.com/magazines/business2/business2_archive/2006/08/01/8382232/index.htm | access-date = 9 March 2007 }} The company did not complete the project. They have plans for a similar plant in Arizona,{{cite web |url=http://www.enviromission.com.au/EVM/Company/ShowPage.aspx/PDFs/1273-76736470/OperationalOverviewJuly1December312010 |title=ENVIROMISSION Operational Overview |date=July 1 – December 31, 2010 |publisher=EnviroMission Limited |format=PDF |access-date=2012-03-30 |url-status=dead |archive-url=https://web.archive.org/web/20120331154722/http://www.enviromission.com.au/EVM/Company/ShowPage.aspx/PDFs/1273-76736470/OperationalOverviewJuly1December312010 |archive-date=March 31, 2012 }} and most recently (December 2013) in Texas,{{cite web | url=http://www.enviromission.com.au/irm/Company/ShowPage.aspx/PDFs/1413-31639141/TexasTraction | title=EnviroMission Limited }} but there is no sign of 'breaking ground' in any of Enviromission's proposals.

In December 2011, Hyperion Energy, controlled by Western Australians Tony Sage and Dallas Dempster, was reported to be planning to build a 1-km-tall solar updraft tower near Meekatharra to supply power to Mid-West mining projects.{{cite news|url=http://www.perthnow.com.au/business/business-old/dallas-dempsters-sky-high-comeback/story-e6frg2qu-1226233935573 |title=Dallas Dempster's sky-high comeback |first=Nick |last=Evans |work=The Sunday Times |date=31 December 2011}}

File:Sicht vom Turm auf das Vordach mit geschwärztem Boden.jpg

In mid-2008, the Namibian government approved a proposal for the construction of a 400 MW solar chimney called the 'Greentower'. The tower is planned to be {{convert|1.5|km|ft}} tall and {{convert|280|m|ft}} in diameter, and the base will consist of a {{convert|37|km2|mi2}} greenhouse in which cash crops can be grown.{{cite web | last = Cloete| first = R | title =Solar tower sheds light on little-used technology | publisher = Engineering News Online | date = 25 July 2008 | url = http://www.engineeringnews.co.za/article.php?a_id=137580 | access-date = 17 October 2008 }}

A model solar updraft tower was constructed in Turkey as a civil engineering project.Archived at [https://ghostarchive.org/varchive/youtube/20211211/-j1K1vwPZS8 Ghostarchive]{{cbignore}} and the [https://web.archive.org/web/20130708181153/http://www.youtube.com/watch?v=-j1K1vwPZS8 Wayback Machine]{{cbignore}}: {{cite web|url=https://www.youtube.com/watch?v=-j1K1vwPZS8 |title=solar chimney www.unienerji.com|publisher=YouTube |date=2010-08-21 |access-date=2011-09-11}}{{cbignore}} Functionality and outcomes are obscure.{{cite web|url=http://www.unienerji.com/?p=310#more-310 |archive-url=https://web.archive.org/web/20110717162810/http://www.unienerji.com/?p=310#more-310 |url-status=usurped |archive-date=July 17, 2011 |title=Güneş Santrali {{pipe}} Güneş Pili |publisher=Unienerji.com |access-date=2011-09-11}}{{cite journal |author=Koyun A |author2=Üçgül İ |author3=Acar M |author4=Şenol R |title=Güneş Bacası Sisteminin Termal Özet Dizaynı |journal=Tesisat Mühendisliği Dergisi |volume=98 |pages=45–50 |date=2007 |url=http://www.mmoistanbul.org/yayin/tesisat/98/6 |url-status=dead |archive-url=https://web.archive.org/web/20100415001750/http://www.mmoistanbul.org/yayin/tesisat/98/6/ |archive-date=2010-04-15 }}

A second solar updraft tower using a transpired collector is operating at Trakya University in Edirne, Turkey, and is being used to test various innovations in SUT designs including the ability to recover heat from photovoltaic (PV) arrays.{{citation needed|date=December 2015}}

File:Solar power tower with PV.jpg

A grade-school pupil's home do-it-yourself SUT demonstration for a school science fair was constructed and studied in 2012, in a suburban Connecticut setting.{{Cite web|url=http://newtownbee.com/news/education/2013/03/07/st-rose-student-creates-solar-updraft-tower/7775|archive-url=https://web.archive.org/web/20131203051959/http://newtownbee.com/news/education/2013/03/07/st-rose-student-creates-solar-updraft-tower/7775|url-status=dead|title=St Rose Student Creates Solar Updraft Tower {{pipe}} The Newtown Bee|archive-date=December 3, 2013}}{{cite web |last=Herrick |first=Grace |url=http://wtnh.com/2013/02/20/a-model-solar-updraft-tower-power-plant/ |title={{pipe}} A Model Solar Updraft Tower Power Plant |publisher=WTNH.com |date=2013-02-20 |access-date=2018-03-05 |archive-url=https://web.archive.org/web/20180306022942/http://wtnh.com/2013/02/20/a-model-solar-updraft-tower-power-plant/ |archive-date=2018-03-06 |url-status=dead }} With a 7-metre stack and 100 square metre collector, this generated a daily average 6.34 mW, from a computer fan as a turbine. Insolation and wind were the major factors on variance (range from 0.12 to 21.78 mW) in output.

In Xi'an, central China, a 60-metre urban chimney with surrounding collector has significantly reduced urban air pollution. This demonstration project was led by Cao Jun Ji, a chemist at the Chinese Academy of Sciences' Key Laboratory of Aerosol Chemistry and Physics.{{Cite journal | title=China tests giant air cleaner to combat smog| journal=Nature| volume=555| issue=7695| pages=152–153| date=2018-03-06| bibcode=2018Natur.555..152C| last1=Cyranoski| first1=David| doi=10.1038/d41586-018-02704-9| pmid=29517032| doi-access=free}} This work has since been published on, with performance data and modelling.{{cite journal |last1=Cao |first1=Qingfeng |last2=Kuehn |first2=Thomas H. |last3=Shen |first3=Lian |last4=Chen |first4=Sheng-Chieh |last5=Zhang |first5=Ningning |last6=Huang |first6=Yu |last7=Cao |first7=Junji |last8=Pui |first8=David Y.H. |title=Urban-scale SALSCS, Part I: Experimental Evaluation and Numerical Modeling of a Demonstration Unit |journal=Aerosol and Air Quality Research |date=2018 |volume=18 |issue=11 |pages=2865–2878 |doi=10.4209/aaqr.2018.06.0238 |doi-access=free }}{{cite journal |last1=Cao |first1=Qingfeng |last2=Huang |first2=Minghua |last3=Kuehn |first3=Thomas H. |last4=Shen |first4=Lian |last5=Tao |first5=Wen-Quan |last6=Cao |first6=Junji |last7=Pui |first7=David Y.H. |title=Urban-scale SALSCS, Part II: A Parametric Study of System Performance |journal=Aerosol and Air Quality Research |date=2018 |volume=18 |issue=11 |pages=2879–2894 |doi=10.4209/aaqr.2018.06.0239 |doi-access=free }}

The traditional solar updraft tower has a power conversion rate considerably lower than many other designs in the (high temperature) solar thermal group of collectors. The low conversion rate is balanced to some extent by the lower cost per square metre of solar collection.{{cite web|url= http://www.eere.energy.gov/troughnet/pdfs/status-part1.pdf |title=3. Solar Energy Systems }} {{small|(1.24 MB)}} Status Report on Solar Trough Power Plants (1996){{cite journal |doi=10.1016/S0038-092X(97)80946-2 |title=Solar electricity generation—A comparative view of technologies, costs and environmental impact |journal=Solar Energy |volume=59 |issue=1–3 |pages=89–99 |year=1997 |last1=Trieb |first1=Franz |last2=Langniβ |first2=Ole |last3=Klaiβ |first3=Helmut |bibcode=1997SoEn...59...89T }}

Model calculations estimate that a 100 MW plant would require a 1,000 m tower and a greenhouse of {{convert|20|km2}}. A 200 MW tower of the same height would require a collector 7 kilometres in diameter (total area of about {{cvt|38|sqkm|sqmi}}). One 200 MW power station will provide enough electricity for around 200,000 typical households and will abate over 900,000 tons of greenhouse producing gases from entering the environment annually. The glazed collector area is expected to extract about 0.5 percent, or 5 W/m² of 1 kW/m², of the solar energy that falls upon it. If a transpired solar collector is used in place of the glazed collector, the efficiency is doubled.

Additional efficiency improvements are possible by modifying the turbine and chimney design to increase air speed using a venturi configuration. Concentrating thermal (CSP) or photovoltaic (CPV) solar power plants range between 20% and 31.25% efficiency (dish Stirling). Overall CSP/CPV efficiency is reduced because collectors do not cover the entire footprint. Without further tests, the accuracy of these calculations is uncertain.{{cite journal |doi=10.1016/j.solener.2005.04.001 |id={{INIST|17773321}} |title=Critical evaluation of solar chimney power plant performance |journal=Solar Energy |volume=80 |issue=5 |pages=535–44 |year=2006 |last1=Pretorius |first1=J.P. |last2=Kröger |first2=D.G. |bibcode=2006SoEn...80..535P |doi-access=free }} Most of the projections of efficiency, costs and yields are calculated theoretically, rather than empirically derived from demonstrations, and are seen in comparison with other collector or solar heat transducing technologies.{{cite book |doi=10.1007/978-94-007-7275-5 |title=Harnessing Solar Heat |series=Lecture Notes in Energy |date=2014 |volume=18 |isbn=978-94-007-7274-8 |first1=Brian |last1=Norton }}{{page needed|date=June 2017}}

An innovative concept recombining a thermal power plant dry cooling tower with a solar chimney was first introduced by Zandian and Ashjaee{{cite journal |doi=10.1016/j.renene.2012.09.051 |title=The thermal efficiency improvement of a steam Rankine cycle by innovative design of a hybrid cooling tower and a solar chimney concept |journal=Renewable Energy |volume=51 |pages=465–473 |year=2013 |last1=Zandian |first1=A |last2=Ashjaee |first2=M |bibcode=2013REne...51..465Z }} in 2013 to increase the efficiency of the solar updraft towers. This hybrid cooling-tower-solar-chimney (HCTSC) system was shown to be able to produce an over ten times increase in output power compared to the conventional solar chimney power plants like Manzanares, Ciudad Real, with similar geometrical dimensions. In addition, it was shown that with an increase in chimney diameter, the power generation can reach to MW-graded power output without the necessity of building huge individual solar chimney panels. The results showed a maximum of 3 MW power output from the HCTSC system which resulted in 0.37% increase in the thermal efficiency of a typical 250 MW fossil fuel power plant, with a chimney diameter of only {{convert|50|m|ft}}. The new hybrid design made the solar updraft tower feasible again, and proved it to be economical in saving much construction cost and time. This concept also recaptures the heat of radiators that are thrown out into the atmosphere without efficient utilization, and prevents generation of excessive greenhouse gasses.

The performance of an updraft tower may be degraded by factors such as atmospheric winds,{{cite book |doi=10.1115/HT-FED2004-56651 |chapter=Computing Flow in a Solar Chimney Plant Subject to Atmospheric Winds |title=Volume 2, Parts a and B |pages=1153–62 |year=2004 |last1=Serag-Eldin |first1=M. A. |isbn=978-0-7918-4691-9 }}{{cite journal |doi=10.1080/01425910212851 |title=The effect of wind speed at the top of the tower on the performance and energy generated from _thermosyphon solar turbine |journal=International Journal of Solar Energy |volume=22 |issue=1 |pages=9–18 |year=2002 |last1=El-Haroun |first1=A. A. |bibcode=2002IJSE...22....9E |s2cid=108960377 }} by drag induced by the bracings used for supporting the chimney,{{cite journal |doi=10.1115/1.1530198 |title=Calculation of Pressure and Density in Solar Power Plant Chimneys |journal=Journal of Solar Energy Engineering |volume=125 |issue=1 |pages=127–9 |year=2003 |last1=von Backström |first1=Theodor W. }} and by reflection off the top of the greenhouse canopy. However, updraft may be enhanced by crosswind at the upper level – creating a low pressure vortex across the top of the chimney would increase updraft.{{cite journal |last1=Watanabe |first1=Koichi |last2=Fukutomi |first2=Sho |last3=Ohya |first3=Yuji |last4=Uchida |first4=Takanori |title=An Ignored Wind Generates More Electricity: A Solar Updraft Tower to a Wind Solar Tower |journal=International Journal of Photoenergy |date=11 March 2020 |volume=2020 |pages=1–9 |doi=10.1155/2020/4065359 |doi-access=free |hdl=2324/3000484 |hdl-access=free }}

• The atmospheric vortex proposal{{cite web|url=http://vortexengine.ca/index.shtml |title=Atmospheric Vortex Engine |publisher=Vortexengine.ca |access-date=2011-09-11}} replaces the physical chimney by a controlled or 'anchored' cyclonic updraft vortex. Depending on the column gradient of temperature and pressure, or buoyancy, and stability of the vortex, very high-altitude updraft may be achievable. As an alternative to a solar collector, industrial and urban waste-heat could be used to initiate and sustain the updraft in the vortex.
• Telescopic or retractable design may lower a very high chimney for maintenance, or to prevent storm damage. Hot-air balloon chimney suspension has also been proposed.
• A form of solar boiler technology placed directly above the turbine at the base of the tower might increase the up-draught.{{citation needed|date=September 2011}}
• Moreno (2006) proposed that a chimney can be economically placed on a hill or mountain slope. Klinkman (2014) elaborated on constructing diagonal chimneys.{{cite patent|country=US|number=8823197|pubdate=2014-09-02|title=Diagonal solar chimney|inventor1-last=Klinkman|inventor1-first=Paul}} A structure as simply built as a high hoop tunnel, but much longer in length and on a slope, can permanently generate an airflow for producing electricity. Changing the chimney's height differential from 200 m (the Manzanares experiment) to 2000 m (Charleston Peak in Nevada has a rise of over 2500 m, for example) will transfer a factor of ten more of captured solar heat into electric power. Increasing the temperature differential between chimney air and outside air by a factor of ten increases the same chimney's power by one further factor of ten, assuming that the chimney's walls are engineered to take the extra heat. Concentrating solar heat is often done with reflection.
• An inflatable solar chimney power plant has been evaluated analytically and simulated by computational fluid dynamics (CFD) modeling. This idea has been registered as a patent, including the optimal shape of the collector and the analytical profile for the self standing inflatable tower.{{cite journal |doi=10.1016/j.solener.2013.07.010 |title=Inflatable free-standing flexible solar towers |journal=Solar Energy |volume=98 |pages=85–98 |year=2013 |last1=Putkaradze |first1=Vakhtang |last2=Vorobieff |first2=Peter |last3=Mammoli |first3=Andrea |last4=Fathi |first4=Nima |bibcode=2013SoEn...98...85P }} The CFD simulation has been evaluated by verification, validation, and uncertainty quantification (VVUQ) of computer simulations by American Society of Mechanical Engineers 2009 standards.Fathi, Nima, Peter Vorobief, and Seyed Sobhan Aleyasin. "V&V exercise for a solar tower power plant." In ASME Verification and Validation Symposium. 2014.Vorobieff, Peter V., et al. "Inflatable, free-standing solar updraft tower with optimal geometry and active control." U.S. Patent No. 10,006,443. 26 Jun. 2018.
• Airtower is a proposal by architect Julian Breinersdorfer to better exploit the high initial capital outlay of building a very high structure by incorporating it into a high rise building core. The proximity of producer and consumer can also reduce transmission losses.{{cite news|url=https://www.faz.net/aktuell/wissen/natur/generationenvertrag-vorwaerts-zur-natur-1626516.html |title=Vorwärts zur Natur |newspaper=faz.net |access-date=2011-05-03|last1=Schellnhuber |first1=Hans Joachim }}

• A saltwater thermal sink in the collector could 'flatten' the diurnal variation in energy output, while airflow humidification in the collector and condensation in the updraft could increase the energy flux of the system.
• As with other solar technologies, some mechanism is required to mix its varying power output with other power sources. Heat can be stored in heat-absorbing material or saltwater ponds. Electricity can be cached in batteries or other technologies.{{cite web|title=Integration of Wind Energy into the Grid |publisher=European Wind Energy Association — EWEA |date=2005–2007 |url=http://www.ewea.org/index.php?id=196 |access-date=29 May 2007 |url-status=dead |archive-url=https://web.archive.org/web/20070625173146/http://www.ewea.org/index.php?id=196 |archive-date=June 25, 2007 }}
• A recent innovation has been the use of transpired collectors in place of the traditional glazing covers.[http://solarwall.com/en/home.php] {{Webarchive|url=https://web.archive.org/web/20170504161209/http://solarwall.com/en/home.php|date=2017-05-04}}{{full citation needed|date=June 2017}} Transpired collectors have efficiencies in the 60% to 80% range or three times the 25% efficiency measured with the greenhouse collectors.{{cite journal |doi=10.1016/j.enconman.2017.03.052 |title=Thermal performance of a transpired solar collector updraft tower |journal=Energy Conversion and Management |volume=142 |pages=286–95 |year=2017 |last1=Eryener |first1=Dogan |last2=Hollick |first2=John |last3=Kuscu |first3=Hilmi |bibcode=2017ECM...142..286E }} The large solar collector field can now be reduced to half or less making solar updraft towers much more cost effective. A patent has been granted on a solar tower system using transpired collectors.{{Cite patent|country=US|number=9097241|pubdate=2015-08-04|title=Transpired solar collector chimney tower|assign1=Hollick SOlar Systems Ltd.|inventor1-last=Hollick|inventor1-first=John C.|inventor2-last=Eryener|inventor2-first=Dogan}}

• If the chimney updraft is an ionized vortex, then the electro-magnetic field could be tapped for electricity, using the airflow and chimney as a generator.{{citation needed|date=September 2011}}

• Release of humid ground-level air from an atmospheric vortex or solar chimney at altitude could form clouds or precipitation, potentially altering local hydrology.{{cite journal |doi=10.1016/j.atmosres.2008.05.003 |title=Numerical investigation of a plume from a power generating solar chimney in an atmospheric cross flow |journal=Atmospheric Research |volume=91 |issue=1 |pages=26–35 |year=2009 |last1=Zhou |first1=Xinping |last2=Yang |first2=Jiakuan |last3=Ochieng |first3=Reccab M. |last4=Li |first4=Xiangmei |last5=Xiao |first5=Bo |bibcode=2009AtmRe..91...26Z }}{{cite journal |doi=10.1115/1.3028041 |title=Cloud Formation in the Plumes of Solar Chimney Power Generation Facilities: A Modeling Study |journal=Journal of Solar Energy Engineering |volume=131 |page=011009 |year=2009 |last1=Vanreken |first1=Timothy M. |last2=Nenes |first2=Athanasios |citeseerx=10.1.1.172.2449 }} Some of these ideas originated in work by Niewiadomski and Haman who studied cooling tower dynamics.{{cite journal |doi=10.1016/0004-6981(84)90019-2 |title=The rainfall enhancement by washout of cooling tower plumes: A numerical experiment |journal=Atmospheric Environment |volume=18 |issue=11 |pages=2483–9 |year=1984 |last1=Niewiadomski |first1=Michal |last2=Haman |first2=Krzysztof E. |bibcode=1984AtmEn..18.2483N }} Local de-desertification, or afforestation could be achieved if a regional water cycle were established and sustained in an otherwise arid area.
• The solar cyclone distiller{{cite journal |last1=Kashiwa |first1=B.A. |last2=Kashiwa |first2=Corey B. |title=The solar cyclone: A solar chimney for harvesting atmospheric water |journal=Energy |date=February 2008 |volume=33 |issue=2 |pages=331–339 |doi=10.1016/j.energy.2007.06.003 |bibcode=2008Ene....33..331K }} could extract atmospheric water by condensation in the updraft of the chimney. This solar cyclonic water distiller in the updraft above a solar collector pond could adapt the solar collector-chimney system for large-scale desalination of collected brine, brackish- or waste-water pooled in the collector base.{{cite journal |doi=10.1016/j.desal.2009.03.007 |title=Comparison of classical solar chimney power system and combined solar chimney system for power generation and seawater desalination |journal=Desalination |volume=250 |pages=249–56 |year=2010 |last1=Zhou |first1=Xinping |last2=Xiao |first2=Bo |last3=Liu |first3=Wanchao |last4=Guo |first4=Xianjun |last5=Yang |first5=Jiakuan |last6=Fan |first6=Jian |issue=1 |bibcode=2010Desal.250..249Z }}
• Fitted with a vortex chimney scrubber, the updraft could be cleaned of particulate air pollution. An experimental demonstration tower is cleaning the air in a Chinese city with little external energy input.{{cite news|last1=Chen|first1=Stephen|title=China builds 'world's biggest air purifier' (and it seems to be working)|url=http://www.scmp.com/news/china/society/article/2128355/china-builds-worlds-biggest-air-purifier-and-it-seems-be-working|access-date=22 January 2018|work=South China Morning Post|date=16 January 2018}}{{cite news | url=http://www.digitaljournal.com/tech-and-science/technology/china-tests-giant-chimney-to-combat-air-pollution/article/516647 | title=China tests giant chimney to combat air pollution| newspaper=Digital Journal| date=2018-03-07}}
• Alternately to scrubbing, particulate air pollution caught in the updraft and released could serve as a nucleation stimulus for precipitationCloud condensation nuclei either in the chimney, or at release altitude as cloud seeds.
• Removal of urban air pollution raised and dispersed at altitude could reflect insolation, reducing ground-level solar warming.Smog tower{{Circular reference|date=April 2023}}
• Energy production, water desalination or simple atmospheric water extraction could be used to support carbon-fixing or food-producing local agriculture,{{cite web|author=Tom Bosschaert |url=http://www.except.nl/consult/SolarUpdraftTower/solar_updraft_research.html |title=Solar Updraft Tower Research: Except Consulting |publisher=Except.nl |date=2008-09-26 |access-date=2011-09-11}} and for intensive aquaculture and horticulture under the solar collector as a greenhouse.
• A balloon-suspended lightweight extensible chimney anchored from an urban tether, rising from low level warm air to high altitude could remove low lying air pollution without the need for a broad collector at the base, given adequate height of release. This might improve air quality in highly polluted megacities without the burden and cost of major fixed construction.

A solar updraft power station would require a large initial capital outlay, but would have relatively low operating cost.

Capital outlays would be roughly the same as next-generation nuclear plants such as the AP-1000 at roughly $5 per watt of capacity. As with other renewable power sources, towers have no need for fuel. Overall costs are largely determined by interest rates and years of operation, varying from 5 eurocents per kWh for 4% and 20 years to 15 eurocents per kWh for 12% and 40 years."The Solar Chimney" by Jörg Schlaich, 1995

Estimates of total costs range from 7 (for a 200 MW plant) and 21 (for a 5 MW plant) euro cents per kWh to 25–35 cents per kWh.{{note|PhysicaPlus}} {{cite journal | last = Zaslavsky | first = Dan | title = Energy Towers | journal = PhysicaPlus | issue = 7 | date = 2006 | url = http://physicaplus.org.il/zope/home/en/1124811264/1137833043_en | access-date = 30 March 2007 | url-status = dead | archive-url = https://web.archive.org/web/20060814030113/http://physicaplus.org.il/zope/home/en/1124811264/1137833043_en | archive-date = 14 August 2006 }} The levelized cost of energy (LCOE) is approximately 3 Euro cents per KWh for a 100 MW wind or natural gas plant.[http://www.energy.ca.gov/electricity/levelized_cost.html Levelized Costs of Electricity Production by Technology] {{webarchive|url=https://web.archive.org/web/20080508185408/http://www.energy.ca.gov/electricity/levelized_cost.html |date=2008-05-08 }} California Energy Commission, 2003 No actual data are available for a utility-scale power plant.{{cite web | last = Groenendaal | first = B.J. | title = Solar Thermal Power Technologies | work = Monograph in the framework of the VLEEM Project | publisher = Energy Research Centre of the Netherlands |date=July 2002 | url = http://www.ecn.nl/docs/library/report/2002/c02062.pdf | access-date = 30 March 2007 |url-status=dead |archive-url=https://web.archive.org/web/20180304224320/http://www.ecn.nl/docs/library/report/2002/c02062.pdf |archive-date=2018-03-04}}

• Energy tower (downdraft)
• Smog tower
• Solar pond
• Vortex engine
• Windcatcher

{{reflist}}

{{Commons category}}

• [http://www.solar-updraft-tower.com/en Schlaich Bergermann Solar]
• [http://hyperionenergy.com.au/about-us/ Hyperion project, Western Australia]
• [https://www.youtube.com/watch?v=pAsvmA4Xym8&playnext=1&list=PLE0765FB6E0ACDB0B video link Spanish solar updraft tower]
• [https://www.youtube.com/watch?v=cLIiGTZxH5s video link Australian tower proposal ]
• [http://www.globalwarmingsolutions.co.uk/TheSolarNozzle.html Solar Nozzle]
• [https://money.cnn.com/2006/08/01/technology/towerofpower0802.biz2/index.htm CNN money article] 2006-10-26
• {{structurae|id=20004871|title=Mildura Solar Tower}}
• [https://web.archive.org/web/20071124034345/http://www.greentower.net/UNIVERSITY%20STUDY.htm University of Stellenbosch study]
• [http://www1.eere.energy.gov/solar/index.html U.S. Department of Energy's Solar Energy Technologies program]
• [http://vortexengine.ca/index.shtml Atmospheric Vortex alternative to Solar Chimney]
• [http://www.scpt2010.de/ 2nd International Conference on Solar Chimney Power Technology] {{Webarchive|url=https://web.archive.org/web/20140518111954/http://scpt2010.de/ |date=2014-05-18 }}
• [https://web.archive.org/web/20130509104840/http://sutpt2012.org/ 3rd International Conference on Solar Updraft Tower Power Technology]
• {{cite web |title=Solar Updraft Tower |url=https://demonstrations.wolfram.com/SolarUpdraftTower/ |website=Wolfram Demonstrations Project }}

{{Authority control}}

Category:Energy conversion

Category:Power station technology

Category:Solar power

Category:Sustainable energy