IBM's "liquid metal" promises concentrated PV breakthrough

For years, the solar energy industry has debated the relative merits of concentrated solar thermal and photovoltaic cell technologies, but now IT giant IBM reckons it has found a highly efficient means of combining the two technologies, which it claims could slash the cost of solar farms.

The company will today demonstrate a new concentrator photovoltaic (CPV) system that uses a large lens to concentrate a record 230 watts of solar power onto a single centimetre square solar square. The highly concentrated energy is then converted into 70 watts of usable electric power, an output IBM claims represents about five times the electrical power density generated by current CPV systems.

CPV systems have been around in some form for decades, but the technology's potential as an energy source has been hampered by the fact that concentrating solar power to generate temperatures high enough to deliver significant power outputs can damage, and even melt the PV cells.

The company, however, claims to have overcome this problem by adapting some of the technology it uses to cool computer chips for use in the PV cells.

The IBM research team used a very thin layer of a liquid metal made of a gallium and indium compound that they applied between the chip and a copper cooling plate. The result was that the cell was cooled from temperatures of over 1,600 degrees Celsius to just 85 degrees Celsius.

IBM admitted that undisclosed "additional challenges" would still have to be overcome to move the project from a laboratory environment into production. However, it claimed that "provided the temperature of the cells can be kept low and cheap, and efficient optics can be developed for concentrating the light to very high levels" then the technology has the potential to "offer the lowest-cost solar electricity for large-scale power generation".

For example, the company calculates that while current CPV systems can concentrate the sun's power up to a level equivalent to the solar power of 200 suns at noon on a clear day, delivering approximately 20 watts per square centimetre, the new cells could cope with the concentrated power of 2,000 suns, resulting in 200 watts per square centimetre. IBM claims such performance would allow solar farm operators to cut the number of PV cells and other components by a factor of 10, slashing costs while still delivering the same power output.

Dr. Supratik Guha, the scientist leading PV activities at IBM Research, said the breakthrough underlined the company's commitment to adapting its expertise in semiconductor and nanotechnology systems to the solar energy sector.

"We believe IBM can bring unique skills from our vast experience and past lab projects to the important field of alternative energy research," he said "This is one of many exploratory research projects incubating in our labs where we can drive big change for an entire industry and the world, while advancing the basic underlying science of solar cells."