When you were a kid, perhaps you entertained yourself on a sunny day with a magnifying glass and the concentrated power of the sun: with the right angle and some patience, you could make your own miniature Death Beam.
IBM, a pair of Swiss universities, and a company called Airlight Energy have taken the concept and scaled it up in a big way, creating a solar concentrator that doubles as an electricity maker and a source of thermal energy. The High Concentration Photovoltaic Thermal system, which the consortium has given the nominally more pronouncable label HCPVT, uses mirrors to concentrate the power of the sun falling on earth by as much as 2,000 times its normal intensity.
If Dr. Evil had satellite television, the dish for picking up signals might look like the HCPVT. It’s a fairly large parabolic dish covered by “a multitude” of mirror facets. These mirrors reflect and concentrate solar energy onto photovoltaic (PV) chip-studded “receivers”; each 1×1 cm PV chip is capable of converting up to 250 watts during the course of a sunny 8-hour day. Altogether, the system can generate a steady 25 kilowatts of electricity.
“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.
But wait, there’s more.
Putting Waste Heat to Good Use
The heat generated by the concentrated sun rays is so intense it would melt the support beam holding up the receivers, were it not for some type of cooling system. Thus, the receivers are fitted with “microchannel” passages that direct coolant past the PV chips and keep the structure from disintegrating part of itself.
This design creates a side benefit. In addition to the electricity produced, the HCPVT also generates useful heat. The researchers intend this “waste” heat to be used for removing the salty impurities from water (a process called desalination or desalinization) so that it’s safe to drink. Imagine one of these next to a desert city by an ocean, or in an area where the water table is too salty to pump and drink from the ground, and its potential usefulness becomes apparent.
The heat could also be used to provide air conditioning – you read that right – by taking advantage of a process called the thermal cycle, using an adsorption chiller. An adsorption chiller removes heat and produces cold by means of an absorbing material such as silica gel. Unlike compression chillers (such as conventional AC units), an adsorption chiller uses benign water as a liquid for transporting heat and doesn’t place a strain on the power grid when operating.
In addition to IBM and Airlight Energy, participants in the project included Swiss universities ETH Zurich and Interstate University of Applied Sciences Buchs NTB. The Swiss Commission for Technology and Innovation bankrolled the effort, providing the equivalent of $2.4 million over three years.
Reflections on a Mirrored Solar Concentrator
For now, a prototype system is under testing at IBM Research’s facility in Zurich, Switzerland. Additional prototypes are scheduled for construction in Biasca and Rueschlikon, Switzerland, soon.
Cool as the technology is, don’t expect to install one in your backyard any time soon, even if you could afford it. While its makers say the HCPVT can get electricity costs down to a reasonable 10 cents a kilowatt-hour (comparable with coal production costs, on the high end), the unit has a lot of complexity that many home and small business solar energy buffs might just as soon do without. Motorized trackers, for instance, bring added expense and maintenance. Plus, the thing is huge – it doesn’t quite blend into the neighborhood the way rooftop solar panels can. If implemented, it would have to be in large numbers, likely isolated from the population center(s) such an installation would serve.
Nonetheless, it provides an interesting possible solution to particularly hot, high-sun areas where it could presumably be more cost effective – places like the southwestern United States, the Arabian Peninsula, Australia, for instance; as well as extremely remote locations such as island resorts.