Solar Electricity and Heat to Remote Locations

Airlight Energy, a Swiss-based supplier of solar electricity technology has partnered with IBM Research to bring affordable solar technology to the market by 2017. The system can concentrate the sun’s radiation 2,000 times and convert 80 percent of it into useful energy to generate 12 kilowatts of electrical power and 20 kilowatts of heat on a sunny day—enough to power several average homes.

The High Concentration PhotoVoltaic Thermal (HCPVT) system, which resembles a 10-meter-high sunflower, uses a 40-square-meter parabolic dish made of patented fiber-based concrete, which can be molded into nearly any shape in less than four hours and has mechanical characteristics similar to those of aluminum at one-fifth the cost.

The inside of the parabolic dish is covered with 36 elliptic mirrors made of 0.2-millimeter-thin recyclable plastic foil with a silver coating, slightly thicker than the wrapper chocolate bars are packaged in, which are then curved using a slight vacuum. The mirrored surface area concentrates the sun’s radiation by reflecting it onto several microchannel liquid-cooled receivers, each of which is populated with a dense array of multi-junction photovoltaic chips—each 1×1-cm² chip produces an electrical power of up to 57 watts on a typical sunny day. The mirrors and the receiver are encased with a large inflated transparent plastic enclosure to protect them from rain or dust. The enclosure also prevents birds and other animals from getting in harm’s way.

The photovoltaic chips, similar to those used on orbiting satellites, are mounted on micro-structured layers that pipe treated water within fractions of millimeters of the chip to absorb the heat and draw it away 10 times more effectively than with passive air cooling. The 85-90 Celsius (°C) (183-194 Fahrenheit (°F)) hot water maintains the chips at safe operating temperatures of 105 °C (221 °F), which otherwise would reach over 1,500 °C (2,732 °F). The entire system sits on an advanced sun tracking system, which positions the dish at the best angle throughout the day to capture the sun’s rays.

The direct hot-water cooling design with very small pumping power has already been made commercially available by IBM in its high-performance computers, including SuperMUC, Europe’s fastest supercomputer in 2012.

“The direct cooling technology with very small pumping power used to cool the photovoltaic chips with water is inspired by the hierarchical branched blood supply system of the human body,” said Dr. Bruno Michel, manager, advanced thermal packaging at IBM Research.

An initial demonstrator of the multi-chip solar receiver was developed in a previous collaboration between IBM and the Egypt Nanotechnology Research Center.

With such a high concentration and based on its radical design, researchers believe that with high-volume production they can achieve a cost of two to three times lower than comparable systems.

Airlight Energy has spun off a new company called Dsolar (dish solar) to market, license and sell the HCPVT system globally. Dsolar has licensed several patents from IBM in the area of hot-water chip cooling.

“With the HCPVT we are ushering in a new generation of solar energy technology,” said Dr. Gianluca Ambrosetti, Head of Research, Airlight Energy with responsibilities for building the new spinoff. “Not only is the system affordable, but it will create jobs where it is installed because many of the materials will be sourced locally. We expect to partner with firms around the world to bring a commercial version to market by 2017.”

Based on its current design, scientists estimate that the operating lifetime for the HCPVT structure is up to 60 years with proper maintenance. The protective foil and the plastic elliptic mirrors will need to be replaced every 10–15 years depending on the environment, and the photovoltaic cells need replacing every 25 years. Throughout its lifetime the system will benefit from design and manufacturing improvements, allowing for an even greater system efficiency.

The HCPVT system can also be customized with further equipment to provide drinkable water and air conditioning from its hot water output. For example, salt water can pass through a porous membrane distillation system, where it is vaporized and desalinated. Such a system could provide 30–40 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, whereas a large multi-dish installation could provide enough water for a town.

By means of a thermally driven sorption chiller, cool air can also be produced. A sorption chiller is a device that converts heat into cooling via a thermal cycle applied to a liquid or solid sorption material. Adsorption chillers, with solid silica gel adsorbers and with water as a working fluid, can replace compression chillers, which place a burden on electrical grids in hot climates and contain working fluids that are harmful to the ozone layer. Although absorption (liquid sorption) systems are already available for combination with the HCPVT system, they provide less cooling output compared to low-temperature driving heat for the adsorption (solid sorption) systems under development at IBM. The systems can also be customized with a transparent back for urban installations.

Initial HCPVT systems will be made available with non-optimized predecessor distillation and sorption cooling systems. Systems with optimized desalination and sorption cooling technologies require an additional two to three years of development with additional partner companies.

Airlight Energy and the IBM Corporate Service Corps (CSC) will team up to donate a High Concentration PhotoVoltaic Thermal (HCPVT) system to two deserving communities. Each winning community will receive a prototype HCPVT system from Airlight Energy, and be eligible for pro bono enablement and transformation support from IBM Corporate Service Corps.Applications from communities will be open in 2015 and the winners will be announced in December 2015, with installations beginning in late 2016.

Scientists at Airlight and IBM envision the HCPVT system providing sustainable energy to locations around the world including southern Europe, Africa, the Arabian peninsula, the southwestern part of North America, South America, Japan and Australia. In addition to residences, additional applications include remote hospitals, medical facilities, hotels and resorts, shopping centers and locations where available land is at a premium.

Some of the initial funding for the development of the HCPVT system was provided to IBM Research, Airlight Energy, ETH Zurich and the Interstate University of Applied Sciences Buchs NTB in a three-year grant from the Swiss Commission for Technology and Innovation.