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Energy towers touted as future source of electricity

Posted By Stuart Winer On September 14, 2003 @ 10:28 pm In | No Comments

Energy towers are the brain-child of Professor Dan Zaslavsky and make use of the convection of air through a hollow tower to turn turbines.

From giant energy towers to new solar power units, alternative forms of energy came to the forefront last month at a joint Israeli-U.S. conference in Jerusalem. And the participants, including senior officials at the U.S. Department of Energy, said they duly impressed by Israel’s innovations that will help generate news forms of electricity.

When President George W. Bush delivered his state of the union address in January 2003 he called for energy revolution as a national target for the United States. “Our third goal is to promote energy independence for our country, while dramatically improving the environment,” Bush said.

The energy requirements of Western countries largely fall into two categories: powering vehicles and generating electricity.

The conference – called Cooperation for Energy Independence of Democracies – kicked off with the first ever demonstration of a commercial hydrogen fuel cell in Israel. The cell, slightly smaller than a desktop computer, generated enough electricity to run a laptop computer using hydrogen from an attached gas cylinder.

Former US senator Rod Grams, addressing the conference, stressed the importance of energy independence to both Israel and the United States. “We have faced energy crises and Israel has no natural energy resources of its own,” Grams said. “By gaining independence we lessen the chance of energy being used as a weapon. Israel does have brain power, so let’s turn that into energy.”

The choice of location for the conference was significant according to various speakers. The Honorable Admiral (ret.) Thomas J. Gross, US Deputy Assistant Secretary of Energy, who attended the conference, said “Israel is a superior location for technical and scientific talent.”

Whereas hydrogen fuel cells, which generate electricity from liquefied hydrogen gas, are seen as the future replacement for gasoline and diesel, conference participants learned that a variety of methods are being investigated in Israel as alternative, renewable methods of producing electricity.

Israel, as a desert country, is one of the world leaders in the field of solar power and local companies used to conference to show what the future holds in power from the sun.

“A square yard of desert absorbs as much energy over a year as you can get out of a barrel of oil,” says Professor David Faiman, of the Ben Gurion University Solar Energy Center.
Producing the hundreds of megawatts of energy required by communities in developed nations requires vast areas of desert covered with solar panels.

However, research by Israeli companies is working to improve efficiency of solar systems.

Barbra Shaw, marketing manager for Solel, a Beit Shemesh based company says that the turbulent energy supplies in California and the southwest of the United States, coupled with world events over the last two years shows that it is time to develop solar power sources. Solel took over Luz, a solar company that set up solar power units in California nearly 20 years ago. The units use ‘troughs’, rectangular mirrors with a parabolic curve that focuses the sun’s rays to provide energy.

Today the company has nine plants in the Mohab desert, operated by three different local power companies. Between them, the solar plants, which cover an area of 500,000 square meters provide over 350 megawatts of electricity to half a million Californians.

That output, says Shaw, is about to get even better. By improving the technologies of the heat collecting panels the company hopes to increase power output by up to 20 percent.

“That is very significant,” Shaw says. “It means the size of the plant can be smaller which brings down set-up costs.

Solel’s expertise is in the coating of a heat collecting glass element that runs the length of each parabolic mirror. Reflected rays from the sun heat the oil which is used to turn water into steam to power turbines.

“What makes it so efficient is the coating on the glass,” Shaw says. Solel is also developing technologies to use solar power for air-conditioning.

Hot water at 100 degrees centigrade passes through an ‘absorption chiller’ where a chemical process turns the hot water in to cool air. “It is like an air-conditioner with out a compressor,” Shaw says.

Solel is now posed to build larger, more powerful plants. The company is seeking to form alliances with American companies in order to build five 100 megawatt plants in the southwest United States.

The problem of providing power at night or in winter is can be solved by have a natural gas back-up source.

“A solar thermal power plant is like a regular plant just its fuel source is the sun,” Shaw explains. “It has turbines that produce electricity. For night or winter you can change the energy source to use natural gas.”

However, one group of researchers at the Faculty of Agricultural Engineering, Technion-Israel Institute of Technology is taking an entirely new approach to generating electricity: Energy Towers.

The idea is the brain-child of Professor Dan Zaslavsky and makes use of the convection of air through a hollow tower to turn turbines. Cold water droplets sprayed into the top of tower evaporates cooling the air which then sinks to the bottom of the tower and turns the turbines.
Zaslavsky claims that forty such towers could generate enough electricity for the whole world, not just today, but for the foreseeable future.

The team set up Sharav Sluices to promote the idea and Doctor Rami Guetta, project manager says the company is already in negotiations to build a 10 megawatt tower in India. Other countries that have shown a serious interest are Australia, Chile, and a French engineering company that is interested in providing the mechanical infrastructure for the towers.

A 50 megwatt energy tower would have to be more than 600 meters high with a 400 meter diameter.

Although the total area required for such a plant would be twice that of a conventional power plant, it is only a tenth of the area required to generate the same electricity from solar panels and the plant can work both day and night without interruption, Zaslavsky told the conference. Following Zaslavsky’s presentation at the Jerusalem conference, Guetta says the Department of Energy officials from the United States expressed an interest in learning more about the energy towers.

“We covered everything that the conference was about. It is a cheap, reliable, and clean energy source that is not dependant on oil,” Guetta
says.

Due to the enormous size of the towers the team has yet to build a working model. However a 21 meter tower in the Technion provided much of
the research data required and Zavlavsky and Guetta spent seven years conducting wind-tunnel test on small scale models of a tower.

“No one denies that the theory works,” Guetta says.

Guetta estimates a 50 megawatt, 600 meter high tower, will cost about 200 million dollars to build.

“The location makes a big difference,” Guetta explains. “The hotter and drier the air the better, and the more electricity a tower can produce, which affects the size required.”

International Energy Consultant and former Assistant Deputy Secretary of Energy Randa Fahmy Hudome, who attended the conference, said North
American attitudes and willingness to change to an alternative energy source depend on reliability.

“Americans are all about consumption,” she says. “If it doesn’t disrupt their lives they are happy with it. As long as the dishwasher goes on when they press the button they are happy.”


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