Published on February 17th, 2009 | by Fred Etcheverry8
Solar Thermal:The Other Solar Energy
The American smart grid promises to increase the efficiency of solar voltaic and wind energy. These sources are still limited to about a 20 to 30% of our electric demand. With current technology, they cannot replace base-load (constant output sources) such as coal that supplies 50% of US electricity. In about ten years, solar thermal may compete with coal as a base-load source.
The European Union is investigating connecting a smart grid to solar thermal generators in Egypt and the Mediterranean. Mexico is also investigating solar thermal. Test plants have been built in Spain, California and Colorado.
Solar thermal used to generate electricity is also called Concentrating Solar Power (CSP) or high temperature solar thermal. Low temperature solar thermal is often used to heat building and swimming pools and can even drive heat pumps to cool air. While low temperature solar thermal can cut electrical and heating fuel consumption, only CSP is used to produce electricity.
Solar voltaic is the most common solar energy used today. It utilizes panels of semiconductor solar cells that convert light immediately into electricity. It only delivers energy during sunlight. Solar thermal uses mirrors or lens to focus the suns ray to heat a medium (usually molten salt) that is then stored in a thermally insulated vault.
The heat from this vault is used to run an engine that recycles its steam. This stored energy can be used to generate electricity when needed (dispatchability) day or night. While solar voltaic will deliver reduced energy during overcast, solar thermal requires a clear sky since it focuses sunlight.
The best locations for solar thermal plants are in hot dry deserts usually found in the Sun Belt such as Egypt, Mediterranean, North African countries, the US southwest and Mexico. Mexico is investigating solar thermal and the EU and Egypt are planning solar thermal instillations.
According to a EU-Egyptian panel, there will be more than 400 MW of solar thermal connected to the European grid by 2010. By 2020 Mediterranean countries could contribute more than 30,000 MW to the EU at a price that can compete with coal-generated electricity.
Not only can solar thermal replace base-load plants, but also its dispatchability enables it to act in load-following and peaking mode. Load following is the ability to ramp up and down to accommodate demand. Peaking is the ability to respond quickly to sudden load transients. The downside of using solar thermal plants to peak is that they must run well below capacity to peak. Since the cost of the output of such plants is primarily based on initial capitalization, electricity produced running below capacity is expensive.
Peaker plants usually using natural gas produce about 20% of US electricity. It is the most expensive electricity.
Peaking is often required to handle air conditioners during a hear wave. A smart grid working with smart programmable thermostats and well insulated houses and building could greatly reduce the need for peaking.
The smart grid will work with the smart meters to reflect the real cost of electricity. Improvements in houses and building to conserve expensive electricity will deliver an immediate return-on-investment. Making such investments will increase the real value of houses.
Photo Credit: fplsolar via Flickr’s Media Commons