IBM Solar Tech Conjures Power of 2,000 Suns to Heat, Cool, Desalinate

By Darryl K. Taft  |  Posted 2013-04-23

IBM Solar Tech Conjures Power of 2,000 Suns to Heat, Cool, Desalinate

IBM announced its involvement in a collaboration to develop an affordable photovoltaic system capable of concentrating solar radiation 2,000 times and converting 80 percent of the incoming radiation into useful energy.

The effort to develop a High Concentration Photovoltaic Thermal (HCPVT) system is funded by a three-year, $2.4 million grant from the Swiss Commission for Technology and Innovation awarded to scientists at IBM Research; Airlight Energy, a supplier of solar power technology; ETH Zurich’s Professorship of Renewable Energy Carriers and Interstate University of Applied Sciences Buchs NTB (Institute for Micro- and Nanotechnology MNT). The HCPVT system can provide desalinated water and cool air in sunny, remote locations where they are often in short supply.

IBM made its announcement on April 22, Earth Day. Based on a study by the European Solar Thermal Electricity Association and Greenpeace International, technically, it would only take 2 percent of the solar energy from the Sahara Desert to supply the world's electricity needs. Unfortunately, current solar technologies on the market today are too expensive and slow to produce, require rare Earth minerals and lack the efficiency to make such massive installations practical, IBM said.

“The prototype High Concentration Photovoltaic Thermal (HCPVT) system is unique in that it is highly efficient at harnessing the sun's radiation using affordable materials, like cement,” Christopher Sciacca, communications manager at IBM Research – Zurich, told eWEEK. “This will reduce the cost by 3 times when compared with similar systems. If we are successful we can change the conversation about the cost of fossil vs. solar because the levelized cost of energy will be less than 10 cents per kilowatt hour (KWh). For comparison, feed in tariffs for electrical energy in Germany are currently still larger than 25 cents per KWh and production cost at coal power stations are around 5-10 cents per KWh.”

The prototype HCPVT system uses a large parabolic dish, made from a multitude of mirror facets, which are attached to a sun-tracking system. The tracking system positions the dish at the best angle to capture the sun's rays, which then reflect off the mirrors onto several microchannel-liquid cooled receivers with triple junction photovoltaic chips--each 1x1 centimeter chip can convert 200-250 watts, on average, over a typical eight hour day in a sunny region.

The entire receiver combines hundreds of chips and provides 25 kilowatts of electrical power. The photovoltaic chips are mounted on micro-structured layers that pipe liquid coolants within a few tens of micrometers off the chip to absorb the heat and draw it away 10 times more effective than with passive air cooling.

The coolant maintains the chips almost at the same temperature for a solar concentration of 2,000 times and can keep them at safe temperatures up to a solar concentration of 5,000 times, IBM said.

The direct cooling solution with very small pumping power is inspired by the hierarchical branched blood supply system of the human body and has been already tested by IBM scientists in high performance computers, including Aquasar. An initial demonstrator of the multi-chip receiver was developed in a previous collaboration between IBM and the Egypt Nanotechnology Research Center.

“For the past several years scientists in Zurich have been focused on using hot water to cool supercomputers and we have successfully demonstrated this with Aquasar and SuperMUC, which was in June 2012 the fastest supercomputer in Europe,” Sciacca said. “In a collaboration with the Egypt Nanotechnology Research Center this same concept was developed to also cool chips used in a solar concentrator. This is a significant achievement in that we can harness the solar radiation of the sun 2000x. In fact, our calculations support it up to 5,000 times.”

"We plan to use triple-junction photovoltaic cells on a micro-channel cooled module which can directly convert more than 30 percent of collected solar radiation into electrical energy and allow for the efficient recovery of an additional 50 percent waste heat," said Bruno Michel, manager, advanced thermal packaging at IBM Research, in a statement. "We believe that we can achieve this with a very practical design that is made of lightweight and high-strength concrete, which is used in bridges, and primary optics composed of inexpensive pneumatic mirrors--it's frugal innovation, but builds on decades of experience in microtechnology.”

IBM Solar Tech Conjures Power of 2,000 Suns to Heat, Cool, Desalinate

"The design of the system is elegantly simple," said Andrea Pedretti, chief technology officer at Airlight Energy, in a statement. "We replace expensive steel and glass with low-cost concrete and simple pressurized metalized foils. The small high-tech components, in particular the microchannel coolers and the molds, can be manufactured in Switzerland with the remaining construction and assembly done in the region of the installation. This leads to a win-win situation where the system is cost-competitive and jobs are created in both regions."

The cement will be used for dish concentrator, Sciacca said. This is unique in that steel is typically used, he said. However, in using cement the team is able to dramatically reduce the cost and it enables the construction to take place where the HCPVT is needed, which creates local jobs, he said.

The solar concentrating optics will be developed by ETH Zurich. "Advanced ray-tracing numerical techniques will be applied to optimize the design of the optical configuration and reach uniform solar fluxes exceeding 2,000 suns at the surface of the photovoltaic cell," said Aldo Steinfeld, professor at ETH Zurich, in a statement.

With such a high concentration and a radically low-cost design, scientists believe they can achieve a cost-per-aperture area below $250 per square meter, which is three times lower than comparable systems, IBM said.

Current concentration photovoltaic systems only collect electrical energy and dissipate the thermal energy to the atmosphere. With the HCPVT packaging approach, scientists can both eliminate the overheating problems of solar chips while also repurposing the energy for thermal water desalination and adsorption cooling.

To capture the medium-grade heat, IBM scientists and engineers are utilizing an advanced technology they developed for water-cooled, high-performance computers, including Aquasar and SuperMUC. With both computers, water is used to absorb heat from the processor chips, which is then used to provide space heating for the facilities.

"Microtechnology as known from computer chip manufacturing is crucial to enable such an efficient thermal transfer from the photovoltaic chip over to the cooling liquid," said Andre Bernard, head of the MNT Institute at NTB Buchs, in a statement. "And by using innovative ways to fabricate these heat transfer devices, we aim at a cost-efficient production."

In the HCPVT system, instead of heating a building, the 90 degree Celsius water will be used to heat salty water that then passes through a porous-membrane distillation system where it is vaporized and desalinated. Such a system could provide 30 to 40 liters of drinkable water per square meter of receiver area per day, while still generating electricity with a more than 25 percent yield or two kilowatt hours per day--a little less than half the amount of water the average person needs per day, according to the United Nations, but a large installation could provide enough water for a town.

Moreover, the HCPVT system can also provide air-conditioning by means of a thermal-driven adsorption chiller. An adsorption chiller is a device that converts heat into cooling via a thermal cycle applied to an absorber made from silica gel, for example. Adsorption chillers, with water as working fluid, can replace compression chillers, which stress electrical grids in hot climates and contain working fluids that are harmful to the ozone layer.

Scientists envision the HCPVT system providing sustainable energy and potable water to locations around the world including southern Europe, Africa, Arabic peninsula, the southwestern part of the United States, South America and Australia. Remote tourism locations are also an interesting market, particularly resorts on small islands, such as the Maldives, Seychelles and Mauritius, since conventional systems require separate units, with consequent loss in efficiency and increased cost.

A prototype of the HCPVT system is currently being tested at IBM Research - Zurich. Additional prototypes will be built in Biasca and Rueschlikon, Switzerland, as part of the collaboration.

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