Solar power tower

From Wikipedia, the free encyclopedia
Jump to navigation Jump to search
Ivanpah Solar Power Facility Online.jpgIvanpah Solar Power Facility (2).jpg
PS10 solar power tower 2.jpg
Thémis.jpgSolarthermisches Versuchskraftwerk Jülich STJ.jpg
Concentrating solar power towers:
  • Top: Solar towers of the Ivanpah facility, the world's largest solar thermal power station in the Mojave Desert, southeastern California
  • Middle: PS10, the world's first commercial solar power tower in Andalusia, Spain
  • Bottom: The THEMIS solar power tower in the Eastern Pyrenees, France (left) and the German experimental Jülich tower (right)

The solar power tower, also known as 'central tower' power plants or 'heliostat' power plants or power towers, is a type of solar furnace using a tower to receive the focused sunlight. It uses an array of flat, movable mirrors (called heliostats) to focus the sun's rays upon a collector tower (the target). Concentrated solar thermal is seen as one viable solution for renewable, pollution-free energy.

Early designs used these focused rays to heat water, and used the resulting steam to power a turbine. Newer designs using liquid sodium have been demonstrated, and systems using molten salts (40% potassium nitrate, 60% sodium nitrate) as the working fluids are now in operation. These working fluids have high heat capacity, which can be used to store the energy before using it to boil water to drive turbines. These designs also allow power to be generated when the sun is not shining.


In 2017, the US National Renewable Energy Laboratory (NREL) has estimated that by 2020 electricity could be produced from power towers for 5.47 cents per kWh.[1] In 2007, companies such as ESolar (then backed by were developing cheap, low maintenance, mass producible heliostat components that were to reduce costs in the near future.[2] ESolar's design used large numbers of small mirrors (1.14 m²), to reduce costs for installing mounting systems such as concrete, steel, drilling, and cranes. In October 2017, an article in GreenTech Media suggested that eSolar ceased business in late 2016.[3]

Improvements in working fluid systems, such as moving from current two tank (hot/cold) designs to single tank thermocline systems with quartzite thermal fillers and oxygen blankets will improve material efficiency and reduce costs further.


Ashalim Power Station, Israel, on its completion the tallest solar tower in the world.
The decommissioned Solar Two in California
  • Some concentrating solar power towers are air-cooled instead of water-cooled, to avoid using limited desert water[4]
  • Flat glass is used instead of the more expensive curved glass[4]
  • Thermal storage to store the heat in molten salt containers to continue producing electricity while the sun is not shining
  • Steam is heated to 500 °C to drive turbines that are coupled to generators which produce electricity
  • Control systems to supervise and control all the plant activity including the heliostat array positions, alarms, other data acquisition and communication.

Generally, installations use from 150 hectares (1,500,000 m2) to 320 hectares (3,200,000 m2).

Environmental concerns[edit]

There is evidence that such large area solar concentrating installations can kill birds that fly over them. Near the center of the array temperatures can reach 550 oC which, with the solar flux itself, is enough to incinerate birds while further away feathers are scorched leading to the eventual death of the bird. Workers at the Ivanpah solar power plant call these birds “streamers,” as they ignite in midair and plummet to the ground trailing smoke. During testing of the initial standby position for the heliostats, 115 birds were killed as they entered the concentrated solar flux. During the first 6 months of operations, a total of 321 birds were killed. After altering the standby procedure to focus no more than four heliostats on any one point, there have been no further bird fatalities.[5]

The Ivanpah Solar Power Facility is classified as a greenhouse gas emitter by the State of California because it has to burn fossil fuel for several hours each morning so that it can quickly reach its operating temperature.[6]

Commercial applications[edit]

Recently, there has been a renewed interest in solar tower power technology, as is evident from the fact that there are several companies involved in planning, designing and building utility size power plants. This is an important step towards the ultimate goal of developing commercially viable plants. There are numerous examples of case studies of applying innovative solutions to solar power.[7] Beam down tower application is also feasible with heliostats to heat the working fluid.[8]

Examples of solar power towers[edit]

Power plants Installed maximum
Yearly total energy
Country Developer/Owner Completed
Ivanpah Solar Power Facility 392 (U/C) 650 United States BrightSource Energy 2013
Ashalim Power Station 121 (U/C) 320 Israel[9] Megalim Solar Power 2018
Crescent Dunes Solar Energy Project 110 (U/C) 500 United States SolarReserve 2015
PS20 solar power tower 20[10] 44 Spain Abengoa 2009
Gemasolar[11][12] 17 100 Spain Sener 2011
PS10 solar power tower 11[13] 24 Spain Abengoa 2006
Sierra SunTower 5[14] United States eSolar 2009
Jülich Solar Tower 1.5[15][16] Germany DLR (German Aerospace Center) 2008
Greenway CSP Mersin Solar Tower Plant 5[17] Turkey Greenway CSP 2013
National Solar Thermal Test Facility 1 (5 - 6 MWt) United States U.S. Department of Energy 1978
Khi Solar One 50 180 South Africa Abengoa 2016

* peak power generation achievable in best possible (weather, etc) conditions

Novel applications[edit]

Pit Power Tower concept in Bingham Canyon mine

The Pit Power Tower[18][19] combines a solar power tower and an aero-electric power tower[20] in a decommissioned open pit mine. Traditional solar power towers are constrained in size by the height of the tower and closer heliostats blocking the line of sight of outer heliostats to the receiver. The use of the pit mine's "stadium seating" helps overcome the blocking constraint.

As solar power towers commonly use steam to drive the turbines, and water tends to be scarce in regions with high solar energy, another advantage of open pits is that they tend to collect water, having been dug below the water table. The Pit Power Tower uses low heat steam to drive the pneumatic tubes in a co-generation system. A third benefit of re-purposing a pit mine for this kind of project is the possibility of reusing mine infrastructure such as roads, buildings and electricity.

See also[edit]


  1. ^ John Lowry (2017). Avoiding Carbon Apocalypse Through Alternative Energy: Life After Fossil Fuels. Springer. p. 33.
  2. ^ Google's Goal: Renewable Energy Cheaper than Coal November 27, 2007
  3. ^ Deign, Jason (12 October 2017). "Concentrated Solar Power Contender ESolar Goes AWOL". GreenTech Media. Retrieved 13 June 2019.
  4. ^ a b "FAQs". Retrieved 2019-09-28.
  5. ^ Kraemer, Susan (16 April 2015). "One Weird Trick Prevents Bird Deaths At Solar Towers". Clean Technica. Retrieved 20 February 2017.
  6. ^ Danelski, David (21 October 2015). "It's not easy being green: Ivanpah solar plant near Nevada burns much natural gas, making it a greenhouse gas emitter under state law". Orange County Register. Santa Ana, California. Retrieved 14 September 2016.
  8. ^ "Three solar modules of world's first commercial beam-down tower Concentrated Solar Power project to be connected to grid". Retrieved 18 August 2019.
  9. ^ Ashalim Power Station, Israel
  10. ^ Abengoa Solar Begins Operation of World's Largest Solar Power Tower Plant Archived 2009-06-18 at the Wayback Machine
  11. ^ Torresol Energy commissions Gemasolar Power Plant in Spain Archived 2012-02-05 at the Wayback Machine
  12. ^ Seba, Tony (2011-06-20). "Gemasolar - The World's First Baseload (24/7) Solar Power Plant". Retrieved 2020-01-12.
  13. ^ First EU Commercial Concentrating Solar Power Tower Opens in Spain
  14. ^ eSolar Ushers in New Era of Solar Energy with Unveiling of Sierra Power Plant Archived 2009-08-11 at the Wayback Machine
  15. ^ RenewableEnergyWorld: Salt-Free Solar: CSP Tower Using Air
  16. ^ DLR: Jülich solar tower power plant – research facility officially handed over to the operator
  17. ^ [1]
  18. ^ Pit Power Tower - Alternative Energy News Feb 2009
  19. ^ Pit Power Tower US Patent
  20. ^ Energy tower

External links[edit]

Institutional links[edit]

Commercial links[edit]