Solar power tower

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 Google.org) 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).

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]

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]

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.

• Concentrated solar power
• Feed-in tariff
• List of concentrating solar thermal power companies
• List of solar thermal power stations
• National Solar Thermal Test Facility (NSTTF)
• Solar furnace
• Solar thermal energy

• Cleantech Group picks winners and losers in concentrated solar thermal
• 'CSP' posts in Green Tech
• eSolar's demonstration plant in Lancaster, Calif.
• National Solar Thermal Test Facility
• Detailed Description of Central Receiver Systems
• Power Station Harnesses Sun's Rays BBC article about solar plant near Seville in Spain
• Description of first commercial Solar Power Tower
• vICERP A research cooperation with a demonstration plant in Juelich, Germany
• Solar Tower Plant Juelich Germany's first solar tower power plant in Juelich
• Heliostat fields on Google maps List of solar tower plants and solar furnaces with heliostat field on Google maps
• Zero Carbon Australia Stationery Energy Plan