For those of you who went to camp in the summer, you may remember burning your initials on a piece of wood by focusing the sun’s rays with a magnifying glass. That’s pretty much the idea behind the Crescent Dunes concentrated solar power project in Nevada. It is now online and generating enough electricity to power 75,000 homes.
Crescent Dunes uses an array of sun tracking mirrors called heliostats to concentrate sunlight and beam it to the top of a nearby tower. There, the sun’s power is used to heat salt to 1,050 degrees Fahrenheit. The molten salt is then stored in tanks, where it can cool to as little as 500 degrees F before being reheated the next day when the sun rises again. Unlike a traditional photovoltaic solar facility, the Crescent Dunes installation can tap the heat of the stored molten salt to create steam to turn traditional electric turbines for up to 10 hours after the sun goes down.
The plant can react to a demand for electricity within 20 minutes of receiving a request from a grid operator for electricity. Solar Reserve, the owner/operator of Crescent Dunes, says the system is 99% efficient. It has a 25 year power purchase agreement with NV Energy to buy the electricity it makes.
NV Energy has been in the news lately, as it has bullied the Nevada Public Utilities Commission into passing new regulations that are highly unfavorable to people with rooftop solar systems in Nevada. Owned by Warren Buffett’s Berkshire Hathaway, NV Energy is a big supporter of solar energy, just as long as it controls the market and the retail price consumers pay for electricity.
Concentrated solar power is significantly less expensive that using conventional lithium ion batteries to store electricity. The Crescent Dunes facility can store enough solar energy to generate more than 1,000 megawatt hours of electricity during a 24 hour period. By comparison, one of the largest battery storage installations in the world, located in Hawaii, can store only 50 megawatt hours. CSP costs about $25 per kilowatt-hour. Even when Tesla’s Gigafactory is fully functional, the batteries it manufactures are expected to cost around $100 per kilowatt-hour.
“It is shortsighted to only look at the immediate cost, and not really on the value that you can give to the energy system, the role that CSP can play to backup, and in combination with PV and wind add up to a really very high share of renewables, because it can provide power on demand when other fluctuating renewables can’t do it,” said Christof Richter, Executive Secretary of SolarPACES. “To fully de-carbonize the grid, we need PV for days and CSP for nights.”
And fully de-carbonizing the electrical grid has to be one of the primary concerns of all the world’s nations as they struggle to lower carbon emissions before global climate change races out of control.