The Solar Tower project is based on a novel technology that enables solar power generation around the clock, without consuming fuel resources or emitting greenhouse gases. The technology is based on the simple and well-known principle, which is that hot air rises. The Sun’s radiation is used to heat air that is captured underneath an expansive plastic roof – the “solar collector”. The collector is a transparent circular cover made of conventional greenhouse plastic and polycarbonate sheeting. It lets through infrared radiation and is resistant to ultra-violet light, which tends to degrade plastic. The hot air trapped under the solar collector rises upward, and is forced to pass through the only exit, which is a chimney in the center of the roof. Accelerating to 70km/h, the air drives the 32 wind turbines installed at the base of the chimney, which generate electricity just like turbines in conventional wind farms.
A prototype tower, which was constructed in the 1980’s in Manzanares, Spain, has successfully produced electricity for seven years. This relatively small-scale pilot plant consistently generated an output of 50kW of green energy and proved that Solar Tower technology is efficient and reliable. The pilot project also showed that the system operates efficiently even on cloudy days, with only a slight drop in the power output.
The system is capable of generating power also at nighttime. This is due to the fact that not only the air, but also the ground beneath it, is heated during the day. The heat absorbed by the ground is re-radiated during the night, keeping the air in the collector warm so that it continuously rises through the chimney and drives the wind turbines. The scientists say such thermal power stations could decrease power production costs to below 0.07 EUR/kWh (about $0.1/kWh), meaning that this technology will be able to compete even with the current lowest conventional power production costs.
EnviroMission is planning to build a 400m-high solar plant, with a 25,000-acre solar collector at its base. The solar plant is expected to generate 200MW of power each year, and prevent over 900,000 tons of greenhouse gases from reaching the atmosphere. Meanwhile, however, the company is planning a smaller-scale device – a solar tower with the capacity to generate 50MW. The company hopes to build the smaller tower by the end of 2009.
Since the collector will be covering vast areas of the ground, the scientists have already thought of making use of the ground beneath. While the prototype solar plant allowed some plants to grow in its collection zone, the larger-scale towers are unlikely to support any greenery. Roger Davey, CEO of EnviroMission in Australia, suggested that the area could be used to dehydrate fruits and vegetables. Davey added that he is very optimistic in regards to the new solar power plant technology, which he said “represents a new category of renewable energy: a technology that is able to meet the demand profile.”
TFOT has previously written about a number of innovative solar power technologies, such as the “nano-flakes” – a newly discovered crystalline material that efficiently converts almost twice the amount of solar energy into electricity than conventional solar panels. You can also read about Nanosolar’s innovative ink, which is used to cost-efficiently “print” the semiconductors used in solar cells. TFOT also covered a Canadian open-source renewable energy project which aims to create a new power plant design that will use a combination of solar and geothermal energy for use in more distant locations without polluting the environment.