One of solar power’s biggest drawbacks is its inability to generate electricity at night. It struggles even on a cloudy day. Part of the problem is that electricity is quite difficult to store and batteries are not efficient enough to contain energy on a large enough scale. However, new approaches being explored by the solar power industries, could soon eliminate the problem.

Power towers – water tanks on stilts, surrounded by hundreds of mirrors that tilt on two axes – will follow the sun as it moves across the sky during the day and continue to track it over the course of a year. Beneath each tower will be a large tank, containing tens of thousands of gallons of molten salt.

The salt, which is non-flammable and non-toxic, melts at 220 degrees celsius and can be kept liquid at 290 degrees in an insulated “cold” storage facility. When electricity is needed, the salt is pumped out of the storage tank to the top of the tower, where concentrated sunlight heats it up to 565 degrees celsius. The hot salt then produces superheated steam and is piped into a series of turbines, causing them to spin and make electricity.

The uniqueness of this solar system is that power can be generated even in periods of cloudy weather or at night, by using the stored thermal energy in the hot salt tanks. The containers are well insulated and could store energy for up to a week. The towers will supply 540 megawatts of heat and in turn, produce 250 megawatts of electricity – enough to power a city.

“You take the energy the sun is putting into the earth that day, store it, capture it, put it into the reservoir and use it on demand,” explains Terry Murphy, chief executive of Solar Reserve, who plan to have their first molten salt solar power plant up and running by 2010.

This breakthrough technology comes at a time when governments are actively seeking to promote renewable energy resources on an industrial scale. It will put solar power firmly into the race to become the world’s dominant electricity source. Economically competitive and not reliant on fossil fuels to operate, the process has zero harmful emissions and is oblivious to the increasing price of oil, gas, coal or other dwindling fuels.

Contact: SolarReserve, 2425 Olympic Boulevard, Suite 500 East,
Santa Monica, California 90404, USA
Website: www.solar-reserve.com

Artist’s rendition of solar farm concept
Photo: courtesy of ucdcms.ucdavis.edu/solar2