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October 2, 2015 | South Africa Finds a Cheaper Way to Create Concentrated Solar Power
A heliostat, derived from the two Greek words “helio” for sun and “stat” for stationary, is a device that uses a mirror that tracks the sun as it crosses the sky during the day. The mirror focuses the light with a series of additional mirrors on one stationary point. The mirrors are all controlled by computers to track the sun exactly to catch its sunlight throughout the day. In the solar energy industry, that stationary point is a solar power tower that has a steam engine on top. The engine uses sunlight to heat a liquid that generates electricity with a turbine. Large-scale, grid-capable solar power plants often use many heliostats to generate power.
However, as the Guardian newspaper points out, the problem with this kind of solar energy is that it tends to be expensive to install. Concentrated solar power (CSP), as it is called, requires a lot of expensive wiring and highly-trained technicians to install it. Additionally, these concentrated solar power plants have been difficult to make work on a small scale. The current technology simply cannot compete with photovoltaic panels, which have gone down in price and up in efficiency in recent years. Concentrated solar power, on the other hand, costs three times as much to generate the same amount of electricity as a hybrid solar/wind unit. As a result, concentrated solar power has undergone a period of decline after its initial growth spurt, at least until now.
The Solar Thermal Research Group at Stellenbosch University in South Africa believes they may now have solved the problem. The goal of the group is to create a unit that is cheap and easy to install, and it seems that they may have found a way to do that. Recently, the team developed a CSP unit that can be installed by only two people and that does not require complex wiring. The mirrors are smaller than those used in standard heliostats, which also makes them easy to deploy. It also works on a small enough scale that it can be a viable option for small communities in the developing world, many of which do not have access to the power grid or a stable electrical supply.
Instead of building heliostats secured by concrete, the South African team’s approach lays out a steel frame to which the heliostats are attached. The heliostats are arrayed around a central tower where the steam turbine is located. The controls that cause the mirrors to track the sun are all wireless, which also cuts down on expenses.
A prototype of the CSP unit, called Helio100, has already been deployed and is generating 150 kilowatts of power, enough to power ten households. Helio100 consists of 100 of the smaller, easily-deployable heliostats, each occupying 2.2 square meters of space. And because of its cost effectiveness, the South African team’s CSP unit is competitive with generators powered by diesel fuel, which are frequently used during power blackouts, a recurring problem in South Africa.
The South Africans do not envision their new technology replacing grid power altogether. Rather, they envision their small-scale concentrated solar power as a supplement and a backup for grid power when blackouts occur. This approach would eliminate the need to use diesel generators, cutting fuel costs and cutting down on the production of greenhouse gasses. It will also provide power to rural communities that do not have access to the grid.
The beauty of small-scale, easily deployable concentrated solar power is that it can be built using labor and materials available in countries like South Africa, which lack a high-tech base. Once the technology is further refined and is produced on an industrial scale, CSP will become part of the solution to provide clean, renewable power to parts of the world that, thus far, lack reliable access to electricity. It might also be used in the developed world by businesses and communities looking for better ways to provide power during blackouts or when the grid is down due to a natural disaster.