It was a good year for solar power in the USA, with over six gigawatts of photovoltaic (PV) capacity and more than one gigawatt of concentrated solar power (CSP) being added in 2014, bringing the nation’s total solar power capacity to more than 17 gigawatts. That’s a 41% increase in solar power capacity in just one year. While PV gets most of the attention due to it being more flexible, concentrated solar power is beginning to shine on a large scale. Let’s take a quick look the advantages and disadvantages of CSP and then check out the utility-scale CSP plants that came online in 2014.
Photovoltaic vs Concentrated Solar Power
Photovoltaic technology converts light directly into electricity. PV panels produce DC, which needs to be converted to AC before being placed on the grid. PV panels work best in direct sunlight when they’re pointed perpendicular to the sun’s rays, but they also work reasonably well in diffuse light, even when not pointed directly at the sun. This makes them inexpensive and suitable for rooftops, since solar tracking isn’t required. PV also works in climates that aren’t particularly sunny; Germany gets less sunlight than the northern US, and yet it has a large portion of its power generated by PV.
Concentrated solar power, on the other hand, requires direct sunlight and solar tracking. CSP focuses the sun’s energy and uses the resulting heat to create steam that drives a traditional turbine generator. Even better, the heat can be stored - usually in the form of molten salts - so the CSP plant can generate electricity even when the sun isn’t shining. Because CSP relies on direct sunlight, it’s most suitable for very sunny locations like the American southwest. Here are two popular types of CSP: trough and tower.
Images: US Department of Energy
US Concentrated Solar Power in 2014
These five major CSP plants went online in 2014 (give or take a few months - one went live in late 2013):
Gila Bend, AZ is the home of the Solana parabolic trough power plant, which provides 250 MW of power to residents of Arizona. The turbine It went live in October of 2013. Spanning 1920 acres, the solar farm includes over two million square meters of reflective troughs and two tanks of molten salts, which provide up to six hours of thermal energy storage. If the stored energy is depleted and the sun isn’t shining, the turbine can be powered by natural gas as a backup.
The Genesis power plant in Blythe CA generates 250 MW of power using a parabolic trough array consisting of more than half a million mirrors. Unlike the Solana plant, Genesis includes no storage or backup fuel. Brought online in April of 2014, designers expect it to generate about 600 GWh of energy each year.
Probably the most famous CSP plant in the US, and the largest of its kind in the world, is the Ivanpah Solar Electric Generating System in Ivanpah Dry Lake CA, about 50 miles south of Las Vegas NV. Its three power towers fired up in February 2014, and the facility now produces 377 MW of power. Its annual production is expected to exceed one terawatt-hour. Ivanpah includes natural gas as its backup, but has no on-site storage.
About 270 miles northwest of Ivanpah is the Crescent Dunes Solar Energy Project in Tonopah, NV. Originally planned to go online in late 2014, the start date has been pushed back to January of 2015. When operational, this 110 MW power tower should produce nearly 500 GWh per year. Crescent Dunes uses molten salt to store heat, allowing it to generate power for ten hours without sunlight.
The Mojave Solar One facility came online in late 2014 and now generates 250 MW of electricity. Located about 100 miles northeast of Los Angeles CA, this parabolic trough array feeds a pair of 125 MW steam turbine generators. The plant should produce about 600 GWh per year.
From a dollars-per-watt standpoint, these CSP plants do not provide the most bang for the buck. They do, however, generate renewable power that doesn’t depend on fossil fuels. This clean energy will prevent about 1.8 million tons of CO2 from entering the atmosphere each year. When you factor in the hidden costs of burning fossil fuels such as climate change and military factors, the cost of solar doesn’t look bad at all.