Posted 02 January 2012 - 10:44 AM
Published: January 01, 2012 07:39 PM
Reliability is the greatest weakness of solar power. The sun provides an abundant, clean source of power to run steam generators that produce electricity. But it is ineffective after the sun sets.
To address that shortcoming, solar plant developers have plans to build facilities in Inland Southern California to store the sun’s power as heat that can be tapped to run steam generators in the late afternoon and evenings when demand for electricity is greatest.
BrightSource Energy Inc., based in Oakland, recently announced plans to add storage to three of six tower-style concentrating thermal solar plants it will build in Riverside and San Bernardino counties to provide electricity for Southern California Edison customers.
The storage is expected to add enough power production capacity so that BrightSource can eliminate plans for a seventh 200-megawatt solar plant and still meet its contract obligation to deliver 4 million megawatt hours of power annually to the utility.
If the contract amendment is approved by the California Public Utilities Commission, “it will represent the largest deployment of thermal energy storage in the world,” said Joe Desmond, former chairman of the California Energy Commission who is senior vice president at BrightSource.
The addition of solar storage will also result in lower costs for utility ratepayers, the company said. Another benefit will be 1,280 acres of desert land that can remain undisturbed if a seventh plant isn’t needed, said BrightSource. BrightSource is altering its construction plans to accommodate storage because its utility customers including Southern California Edison are asking for it, said Desmond.
In its contract with Edison, BrightSource is proposing to add storage to plants that are not too far along in the government permitting process to make a design change, Desmond said.
Storage will be a component of two BrightSource solar plants in San Bernardino County and one in Riverside County, the company said, declining to identify the exact locations. Those three solar plants, each with 250 megawatts of power production capacity, are expected to start generating electricity in 2016 and 2017.
The way BrightSource technology works is that a vast array of mirrors concentrates sunlight on water-filled boilers atop towers to create high-temperature, pressurized steam. The steam is piped through a conventional steam turbine generator that produces electricity.
To store the sun’s power, some of the steam produced during the day at BrightSource plants will be used to super heat molten salts held in a tank. Molten salts are used as a storage medium because they can absorb and hold heat at extremely high temperatures without changing to steam. The heat retained in the molten salts later will convert water to steam to run the plants’ turbines and produce electricity when the sun isn’t shining.
The storage capacity of the BrightSource solar plants will be three to six hours, meaning they could operate that long without daylight. The storage provided will be determined by Southern California Edison, BrightSource said.
Shared by E3wise
Posted 02 January 2012 - 02:32 PM
Posted 02 January 2012 - 08:52 PM
Posted 03 January 2012 - 04:44 AM
Posted 04 January 2012 - 03:47 PM
The reason steam is used so much for electrical generation is that water expands 1500 times when heated to super heated steam. That’s why, when hydro was not available electric utilities have used coal, natural gas, oil, and nuclear fuels to transfer heat to water and make steam to run turbines. Storage was to keep enough fuel on hand to run the generation plant for a few days or weeks.
Concentrated Solar Power (CSP) - is not new and it is one of the most promising ways to use solar to generate electricity cheaply and cleanly. One of the first designs was tested in Israel and is being adopted by desert countries because it also provides the ability to also distill salt water to fresh water easily. It uses Molten Salts that reach temperatures high enough to provide steam for 12 to 16 hours storage, storing solar heat to make steam at night. Since its instillation it has been expanded to also include batteries that now provide enough energy for 48 hours - 4 days.
There are four different types of (CSP) Parabolic Trough, Solar Power Tower, Fresnel Reflectors and Dish Stirling each has specific advantages. The ability to store excess energy for night time electrical production has been incorporated in every facility. Here in the United States several test facilities have been developed by electrical producers and have overseen by the National Renewable Energy Laboratory (NREL). My point is that there have been good pilots developed what we need now is mass scale up in areas that meet Concentrated Solar guidelines.
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