Several hours down Interstate 15, which passes through the US states of California and Nevada, the vast and desolate Mojave desert starts to bloom. From a high vantage point, an alien landscape reveals itself in which fields of mirrors encircle three tall towers.
The Ivanpah Solar Power Station cost $2.18 billion to build and is the biggest solar thermal project in the world at the moment, generating 392MW of electricity. Its developers, NRG Energy and BrightSource Energy (in partnership with Bechtel and Google), have already used more than 150,000 of what will be the final 173,500 mirrors, called heliostats, to reflect sunlight that heats boilers housed in the three towers. Six years in the making and a month to go before operations, the plant spans 3500 acres—almost the size of 2000 soccer fields—and will produce enough energy to power 140,000 homes in California at about 25c/kwh in its initial years (conventional power is much cheaper, though, averaging about 12c/kwh in the United States).
The plant has had to face many challenges to its construction. First, solar plants consume large quantities of water to cool down, and water is scarce in the Mojave. Add to this the mirrors, which need a daily cleaning of dust raised from the desert. Because dust isn’t transparent, a single gram of dust per square metre of a solar panel can reduce its efficiency by 40 per cent, BrightSource has tried to reduce its water consumption by 90 per cent using ‘dry cooling’ instead of ‘wet cooling’. The plant built for transmission of power was named El Dorado and millions of dollars had to be spent in high-voltage power lines.
Environmentalists have raised concerns about the plant’s effect on the fragile desert ecosystems around it. The land on which the plant now stands was inhabited by the desert tortoise (Gopherus agassizii), a species threatened with extinction. BrightSource’s biologists found and relocated almost 200 of these tortoises to new habitats in the Mojave at the cost of about $55,000 per animal, but the animals may not easily adapt to their new surroundings. It is also possible that the heated air emerging from the towers could singe migrating birds.
A similar project coming up in Indio, California, has concerned the Native American community residing there, because its construction will destroy ancient tribal trails.