What is Solar Thermal Electric/CSP?
Concentrating Solar Power with Storage (CSPwS): Foundation of the Renewable Grid in The West
We now have the clean sustainable technology to end our dependence on fossil fuels.
Solar Thermal Electric also known as CSP (Concentrating Solar Power) power plants are large solar energy farms located in desert areas that concentrate the heat of the sun with mirrors. The concentrated heat of the sun is either stored or used directly to generate steam, drive a turbine and generate electricity.
Solar thermal power plants have been generating electricity since the 1980's however current policy does not enable the development of the full potential of this crucial technology. In the last few years in the Southwest, utilities are contracting to buy power from new CSP plants but most cannot afford to pay for the optional thermal storage that can hold the heat of the sun for use whenever power is needed. CSP with storage can emulate the power output of coal or natural gas power plants which is a big help to grid operators and utilities.
The deserts of the world have, in a small fraction of their area, more than enough incident sunshine to supply the power needs of all human societies. These power plants, like the one pictured above, have very little impact on the natural environment of the desert and are far preferable to the consequences, for the natural and the human world, of unchecked coal and natural gas power plant emissions.
These are the only clean, renewable power plants we currently have that can both produce the type of power that the power system needs and scale up to replace a vast majority of fossil fuel plants within the next decades.
To have an entirely clean, sustainable energy system we will have to build energy storage systems; fossil fuels have been our energy storage system for over 200 years. We have discovered in the last two decades that fossil fuel use is endangering our climate system as well as creating geopolitical and economic risks. Thermal storage is now the least expensive clean energy storage options we have, but we can only significantly reduce its cost further through deployment and economies of scale.
The Solar Southwest Initiative is working on creating the policy conditions that will allow CSP plant builders and utilities to work together to realize the potential of desert power through integrating solar thermal plants with 6 to 24 hours of thermal storage. One of the main powerhouses of our future renewable energy system will be solar thermal electric power which will reduce and eventually eliminate our dependence upon coal and other fossil fuels.
If you are interested in working with the Solar Southwest Initiative, please send an email to us at info at solarsouthwest.org.
What is CSP/Solar Thermal Electric?
Most people think of rooftop or poletop solar panels when then think of solar energy. These applications of solar energy are called photovoltaic panels or modules, which use a specially prepared material that generates electricity when light hits it. Sometimes there are also small to medium-size solar thermal collectors on rooftops which are used to heat domestic hot water; these have become popular in some regions of the world as an inexpensive alternative to natural gas water heating.
Solar Thermal Electric or CSP (Concentrating Solar Power)
Unlike the mostly smaller installations of photovoltaic or solar water heating, solar thermal electric plants are very large installations that may stretch for many acres or even square miles. The large expanse of solar collectors contain mirrors that are oriented via motors to track the sun across the sky. When the sun strikes the mirrors they concentrate the rays of the sun on a receptor. Different designs of solar thermal power plant concentrate more or less rays of the sun on the receiver, yielding a lower or higher temperature at the of concentration on the receiver.
The receiver contains a liquid which absorbs the heat of the sun. The liquid, oil, water or molten salt, is called the heat transfer fluid. In most solar thermal electric plants, the heat transfer fluid is pumped some distance to either a power block or a storage tank.
In the power block, a structure that contains machinery, the heat from the heat transfer fluid is run through heat exchanger inside a steam generator or, if heat transfer fluid is itself water, it is alllowed to evaporate creating steam. The pressure of the expanding steam is used, as in a conventional power plant to drive a turbine that turns the coils of a generator that generates electricity. Power engineers are quite familiar with the latter part of the CSP process as this type of power block is quite common.
Those few current CSP power plants that have the storage tanks work almost exactly the same way, except the heat from the heat transfer fluid is stored in a storage tank. The heat is then tapped into by pumping out heated fluid to the steam generator when power is needed. Current storage facility designs lose about 1% of stored heat per day, a negligible amount. The storage tanks enable a solar thermal electric plant to dispatch power at any time that there is stored heat in the tanks. Dispatchable power is more valuable to the managers of the grid than non-dispatchable power.