Many MindedA solar thermal plant that can burn fuel when the sun is gone
US startup 247Solar is developing a concentrated solar system with fossil-fuel backup built into the same machinery. India has contracted the company to build and operate a plant of about 1 megawatt, which will also include photovoltaics. It is still in development, not operating.
Heliostats focus sunlight on a receiver that heats ambient-pressure air to roughly 970° C. The receiver is an updated version of hardware from a German company. Heat is stored in golf-ball-sized ceramic pellets rather than molten salts. Company representative Mark von Keszycki says that can generate power for 9 to 20 hours after sunset, depending on the storage setup. The hot air feeds a heat exchanger built as a drop-in replacement for the combustor in a standard turbine. Because the same exchanger can be heated by burning various fuels, the backup shares the generating hardware. Von Keszycki says this adds under 10 percent to total system cost. Exhaust air near 250° C could serve industrial processes or absorption cooling.
Why it matters: solar panels are now the cheapest power in most places, and concentrated solar has largely stopped being built. Firm, around-the-clock clean power is the harder part of the energy problem. If a plant can promise output without a separate backup station, the cost of reliability falls. Its value is mostly where heat storage and process heat are useful.
Caveats are large. The first installation is tiny, two 200 kW generators using off-the-shelf packages apart from the heat exchanger, and mainly meant to validate the engineering. 247Solar's Bruce Anderson names "unknown unknowns" as the main worry. Cost claims are company statements, unproven at scale. A 3 megawatt design is in engineering. Few grid incentives reward around-the-clock renewable power, and backup costs often fall on others. Our source text was truncated, so some analysis is missing.
Source: Ars Technica