The planned 100MW Redstone concentrated solar thermal power (CSP) plant, which forms part of the South African Renewable Energy Independent Power Producer Procurement Program (REIPPPP), will be the biggest in South Africa.
SolarReserve announced on 11 November 2014 that the 96 megawatt (MW) photovoltaic (PV) Jasper solar power project completed construction and was fully operational.
The PV Jasper plant is currently the biggest solar power plant in South Africa. However, the 100MW Redstone CSP plant is set to overtake it.
SolarReserve, along with its partner ACWA Power, is bidding for the planned Redstone CSP project which is likely to feature SolarReserve’s CSP technology with integrated energy storage.
SolarReserve spokesperson Mary Grikas told MyBroadband that due to the fully integrated thermal energy storage, the Redstone plant will provide non-intermittent dispatchable power on-demand.
“This provides the utility a power source which powers the grid just like conventional coal, oil, nuclear, or natural gas-fired power plants,” said Grikas.
The biggest benefit of the CSP plant is that it produces electricity without harmful emissions or hazardous materials, and without any fuel cost for the 30+ year life of the project.
“We, along with other industry participants, are awaiting announcement by the South Africa DoE, which could happen by the end of the year, hopefully sooner,” said Grikas.
How a CSP plant works
CSP uses thousands of mirrors to reflect and concentrate sunlight onto a central point to generate heat, which in turn is used to generate electricity.
More than 10,000 tracking mirrors called heliostats reside in a 1,500 acre field where they reflect and concentrate sunlight onto a large heat exchanger, called a receiver, which sits atop a 550-foot tower.
Within the receiver fluid flows through piping which forms the external walls – this fluid absorbs the heat from the concentrated sunlight.
In SolarReserve’s technology the fluid utilised is molten salt, which is heated from 500 to over 1,000 degrees Fahrenheit.
Molten salt is an ideal heat capture medium as it maintains its liquid state even above 1,000 degrees Fahrenheit, allowing the system to operate at low pressure for energy capture and storage.
After passing through the receiver, the molten salt then flows down the piping inside the tower and into a thermal storage tank where the energy is stored as high-temperature molten salt until electricity is needed.
SolarReserve’s technology leverages liquid molten salt as both the energy collection and storage mechanism.
When electricity is required by the utility, day or night, the high-temperature molten salt flows into the steam generator, as water is piped in from the water storage tank, to generate steam.
Once the hot salt is used to create steam, it cools. The cooled molten salt is then piped back into the cold salt storage tank where it will then flow back up the receiver to be reheated as the process continues.
The hot molten salt generates superheated steam to drive a standard steam turbine at maximum efficiency to generate electricity during peak demand hours.
After the steam is used to drive the steam turbine it is condensed back into water and returned to the water storage tank.
The steam generation process is identical to the process used in conventional power plants, except that it is 100 percent renewable.