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South Africans Revolutionize Concentrated Solar Power With Mini Heliostats
Taffykay writes: Concentrated Solar Power (CSP) offers significant benefits, but it's often prohibitively expensive. Paul Gauché from Stellenbosch University in South Africa hopes to change that with Helio 100, a series of 'plonkable' miniature heliostats that require no installation or concrete, and offer solar energy that's cheaper than diesel. The Guardian reports: "Helio100 is a pilot project with over 100 heliostats of 2.2 sq meters each, generating 150 Kilowatts (kW) of power in total – enough to power about 10 households. According to Gauché, the array is already cheaper than using diesel, the go-to fuel for most companies and businesses during regular power outages in the country.
Imagine if these cut diesel fuel usage in africa by 30% over the next 5 years.
She was like chocolate when she drank... semi-sweet at first and then increasingly bitter.
Heliostats work by heating a salt to high temperatures then using the heat to power a turbine in a traditional heat engine. The latter tends to be highly efficient (over 90%), while the former is around 75% efficient or more.
I think you're trying to say that mirrors can heat salt with >75% efficiency and heat engines tend to be >90% efficient. The first claim seems vaguely plausible, but the second claim is certainly false. Typical single-cycle power plants have efficiencies around 35%, and combined cycle plants (combustion turbine plus heat-recovery steam generator) have efficiencies up to about 50%.
With a heat engine operating at normal terrestrial temperatures (say 300 K on the cold side and 1000 K on the hot side), the maximum possible efficiency is 70%. To achieve 90% efficiency, the high temperature side would have to be at least 3000 K (half as hot as the sun). I doubt this system is that hot.