Concentrated solar power uses mirrors to turn sunlight into heat rather than converting photons directly into electricity. Although thermal storage once suggested that these systems could generate power around the clock, rapidly falling solar-panel prices have made conventional solar power difficult to beat. A small business is pursuing a different approach: combining solar heat with fossil-fuel backup while allowing both systems to share most of the same power-generation hardware.
Until about a decade ago, concentrated solar power was widely seen as having a bright future. Improvements in thermal storage offered a way to generate electricity even when the sun was not shining, potentially enabling continuous operation.
That promise has not materialized. The cost of concentrated solar power has fallen enough to compete with nuclear power, but the price of electricity from solar panels has dropped much further. In most places, solar panels are now the cheapest source of electricity, and where conditions are suitable for solar generation, their economics are difficult to beat.
As a result, additional facilities are generally needed to meet demand at night and during periods of unfavorable weather. These are typically some combination of battery storage and natural-gas plants. The small business described here aims to avoid building a separate backup facility by designing its concentrated-solar system so that the fossil-fuel backup shares most of the power-generation equipment used by the solar side.
Back to the Future?
Concentrated solar heating, also known as solar thermal power, is simple in principle. Most of the site is covered with heliostats—mirrors mounted on motorized tracking systems that keep sunlight focused as the sun moves across the sky.
The mirrors direct sunlight to a focal point, typically inside a tower, where it heats a working fluid. The hot fluid can drive a conventional steam turbine, or its heat can be stored and used later to generate electricity at night.
There are many variations on this design. Systems can use different working fluids and thermal-storage methods, while trough-shaped mirrors can eliminate the need for a tower. These approaches are intended to address challenges inherent in solar thermal power, including the large number of moving parts and the use of potentially corrosive fluids.
Those challenges, along with a lack of standardization, have kept the cost of concentrated-solar power plants from falling as quickly as the cost of solar panels.
Source: arstechnica.com
