When it comes to solar power, we probably think of photovoltaic panels spread across a roof or laid out in fields on a solar farm, their cells converting light energy directly into electricity. But, of course, there are other options, including using thermal energy from the sun to create electricity – a process which proponents say has important advantages.
Out in California’s vast Mojave Desert a giant solar power plant is taking shape. This facility uses mirrors to focus the sun’s energy on tower-mounted boilers, turning water into steam that drives specially adapted turbines.
Indeed, it seems appropriate to refer to this facility as a plant, with its 170,000 reflectors arranged around a central tower, like petals clustered around the pistil of a flower. And just like the humble daisy, these reflectors – called heliostats – track the sun as it journeys through the sky each day, in order to focus maximum energy onto the towers.
The Ivanpah Solar Electric Generating System (SEGS) – owned by NRG Energy, search giant Google, and BrightSource Energy – is being developed by NRG and Bechtel. It is now nearing completion and aims to be generating electricity later this year. When finished, the plant will be the largest solar thermal power tower system in the world.
The three-unit power complex is located in Ivanpah Dry Lake, on approximately 3,500 acres of public desert land. Advocates say electricity from Ivanpah will avoid millions of tons of carbon dioxide and other air pollutants – the equivalent of taking 70,000 cars off the road – while creating more than 2,100 jobs for construction workers and support staff and 86 jobs for operations and maintenance employees.
“The $2.2 billion project represents a durable model for far-reaching employment and economic benefit both locally and nationally,” an Ivanpah spokesperson declares.
Construction workers have been rigging the heliostats at a brisk 500 a day as they work to complete installation of a total of the 173,500 heliostats needed to power the plant. When finished, the Unit 2 solar field alone will incorporate 60,000 heliostats to produce 133 MW gross of clean electrical energy. In total, the plant is expected to generate at least 377 MW of electricity, enough to power 140,000 homes.
The scheme does have its detractors, however. Native Americans objected to its impact on burial grounds. Meanwhile, construction was temporarily halted in the spring of 2011 so that rare desert tortoises could be relocated away from the facility.
So, why has the consortium opted to deploy this technology? Using mirrors to concentrate sunlight offers a number of advantages including the ability to track the sun (albeit that this is a complex undertaking) as well as efficiency and storage benefits. No solar technology can collect energy at night but storing thermal energy is much easier than storing electrical energy, even given recent advances in battery technology. However, Google announced that it was ceasing investment in CSP (Concentrating Solar Power) due to the rapid price decline of photovoltaic technology and stopped research associated with the project.
Where do you think energy of the future will come from?