Solar Updraft Power tower Technology for Renewable energy

Ramesh Shivanna

Solar energy Expert, Director -FKCCI

Solar Updraft Tower Power (SUTP) generation will be the potential Renewable power to stave off the Lithium storage dumping? 

The environmental and benefits are driving the paradigm shift towards the Renewable energy generation and increasing the share of the national energy mix among all our generations. The notion of going green is not strictly a new technological concept, and any naturally available and theoretically inexhaustible energy such as wind, biomass, solar, tidal, wave, hydroelectric power  that is not derived from fossil or nuclear fuel is referred to as renewable energy. The relevance of these emerging field became more pronounced when the need to produce clean, safe and efficient energy devices without trading off environmental friendliness arise. 

A typical Solar Updraft Tower Plant (SUTP) consists of a circular greenhouse type collector and a tall tower (chimney) at its center. Solar updraft technology is a futuristic power source, but the concept was first suggested 101 years ago by Isidoro Cabanyes, a Spanish army colonel.

In SUPT Air flowing radially inwards under the air collector is heated from the collector floor and roof, and through a turbine enters the chimney. Thereby staging a pressure build up along the tower, and the heat transfer fluid, HTF is warmed up in order to drive the turbine, hence produces energy in the form of electricity. 

As the share of Renewable energy increases the Grid management is becoming the challenge to the utilities because of  flexibility and reliability. The Solar PV generates only when sun shines but it is not flexible, Wind generates only when wind blows not but it is not reliable.   The Solar Updraft Tower Power (SUPT), which uses the greenhouse effect and thermal convection to drive wind turbines and produce electricity, has been hailed as a novel and promising approach to renewable energy generation.

"It's perfect for where you have lots of sun and lots of cheap, flat land," said Patrick Cottam, a doctoral engineering student at University College London's Center for Urban Sustainability and Resilience, who has become an expert on the technology for his thesis. (See related story: "As Solar Power Grows, Dispute Flares Over U.S. Utility Bills.")

The main advantage of solar updraft over PV panels, Cottam said, is "it overcomes the intermittency of solar power." It doesn't need sunlight to operate, just warm air, so it continues to churn out power after sundown. That's because the energy that's absorbed by the land when the sun is shining keeps the air in the collector warm enough at night to keep the turbines spinning.

That effect can be easily and cheaply enhanced by covering the ground with gravel or bitumen, or burying sealed bags of water just below the surface. PV solar plants cannot provide power at night unless they're equipped with expensive, complicated storage solutions that can dissipate very high temperature.

Moreover, PV cells can lose much of their efficiency if they're covered by even a thin layer of dust. That's a problem in desert areas, which are not only dusty, but also very short of the water needed to keep solar panels clean. SUPT need no water, and their canopies, which are less affected by grit, can be dusted clean without water.

So why aren't the world's deserts dotted with many hundreds of solar towers? "The capital costs are very high," said Rudolf Bergermann, co-founder of Schlaich Bergermann and Partner (SBP), a German engineering firm. Who designed  prototype.  

There is no point in building a smaller facility, according to Bergermann (1982). A solar updraft plant "only makes sense on a large scale,"  because the up-front costs are so high. Solar updraft is much less efficient than PV—only 1 to 2 percent of the energy that goes in to the tower gets converted into usable power, compared to PV's efficiency rate of 10 to 20  percent—but that doesn't matter.

If it is built big enough, a solar updraft plant could produce electricity at a cost per kilowatt-hour that is competitive with conventional solar PV power, depending on the plant's financing. And because the only moving parts of a solar updraft plant are the turbines and generator, the overall cost of running and maintaining is also very low. (See also "Mojave Mirrors: World's Largest Solar Energy Ready to Shine.")

A Toppled Test in Spain

So far, there has been only one long-term test of the technology. Back in 1982, with German government funding, SBP built and ran a small, experimental 50-kilowatt solar updraft plant in the south of Spain. It consisted of a 195-meter (640-foot) tower, fashioned from corrugated steel, and a canopy 244 meters (800 feet) in diameter.

And it worked like a charm. The pilot plant was designed as a temporary structure that would last just three years, but it kept running until 1989. By then, however, its steel guy cables had rusted, and it finally toppled in a strong windstorm. According to Bergermann, ”it gave  a great understanding of the thermodynamics that could have been  extrapolate for use on a larger plant," 

Recent discussion on SUPT technological advancement had with Dr Ilan Kuppusamy, Chairman, Clearspan strategic USA/India (www.clearspanstrategic.com/india) and emphasized  to choose India as a suitable environment for this technology as technologically and environmentally sustainable and planning to invest in India for minimum size of One Giga Watt power generation besides it create 12000 skilled and semi- skilled local employment in India. National Academic Research Institution in Basic and Applied Sciences and Engineering, Indian Institute of Engineering and National Institute of Engineering will collaborate in research, mathematical model and simulation studies to deploy SUPT in India along with Clearspan Strategic USA/India  and make it the First tallest structural installation (Tower height 1000m)  in the world.