75 000 homes are being powered by solar energy in Nevada 24/7 without the sun. This is a first in the world and has been made possible through the Crescent Dunes project which is a revolutionary plant using molten salt to store energy.This technology is also known as concentrated solar power. It was designed by SolarReserve, a world leader in solar energy projects on a large scale. With a concentrated solar power plant, more than 10 000 mobile mirrors or heliostats reflect solar energy to a central tower of 640 feet high heating the salt to 1050 degrees Fahrenheit.
The salt is used for two purposes. Firstly, it maintains very high levels of heat, making it like a thermal battery that can be used day and night, regardless of the sun. Secondly, when electricity is required on the gate, the molten salt is sent to a heat exchanger to create superheated steam in order to supply a conventional steam turbine.
This process is not so different from a conventional fossil fuel or nuclear power plants, except that it hardly emits carbon or hazardous waste. The whole project costs a little less than a billion US dollars. SolarReserve landed a 25-year contract to supply NV Energy for $ 135 US dollars per megawatt hour. The tower produces 110 megawatts of power for 12 hours per day, corresponding to about 1 million megawatts per year.
This method of using salt is different compared to photovoltaic technology, which converts sunlight into electricity. While photovoltaic arrays have many advantages and the technology has been well tried and tested, its biggest shortcoming arises when the sun plays conspicuously absent.
With Crescent Dunes, this is no longer an obstacle since the properties of salt can maintain the heat overnight and constantly distribute the energy produced during the day. This innovation will also allow solar power to make big savings because it will be no longer necessary to have two power plants to store energy captured during the day.
Salt can maintain the heat overnight
Apart from Crescent Dunes, SolarReserve is developing two other solar plants using salt. This project aims to develop solar thermal power Redstone in the town of Postmasburg in South Africa. It will be the first plant using concentrated solar energy in Africa. The other is the solar project Copiapó in Chile that will combine concentrated solar power and photovoltaic solar energy. This would be another energy revolution in this South American country.
