Solar panels that directly capture energy from the sun and convert it into electrical energy are well known and recognized as a major source of alternative energy. Solar panels that make hot water are popular in some parts of the world (China, Europe, Brazil, India) and the technology is well known. Solar panels that use the sun’s energy to create heat and then turn it into electricity and hot water are not so well known. That’s because as a practical matter, the approach is new. Most electricity generated by solar heat is produced at installations with specially focused mirrors that track the movement of the sun – which is obviously expensive. The new approach, developed by a team from the Massachusetts Institute of Technology (USA), Boston College (USA) and GMZ Energy (an MIT, BC spinoff company) and published in the journal Nature Materials [1 May 2011, paywalled, High-performance flat-panel solar thermoelectric generators with high thermal concentration] uses a flat panel system looking very much like traditional solar panels. Traditional, however, it is not.
The key, which the research leader Gang Chen calls “very radical,” involves a thermoelectric generator (creates electricity from heat) placed inside a vacuum chamber made of glass, which is covered by a black copper plate that readily absorbs sunlight. The device relies on what is called the Seebeck effect, where the temperature difference between two layers of metallic semiconductor material creates an electric current. The MIT device works with a temperature difference of about 200 degrees Celsius (392 degrees Fahrenheit). The prototype versions produce electricity at an efficiency rate of 4.6%, which is about 6-8 times better than other flat panel approaches, though still well behind the 15-18% efficiency of newer solar panels.
The advantage for this flat panel approach is its relatively simple design, low cost materials, and that it can also be used to heat water at the same time. The systems involved for heat exchange with water heating are very similar to those now in use around the world.
Now comes the hard part: The flat-panel solar thermoelectric system needs to become more efficient if it hopes to compete against standard solar panels (much less the conventional sources of electricity); it needs to find a way into mass production so that costs go down; it needs to find a market if it hopes to become a commercial success. None of these requirements are trivial, which is why so many good ideas and good prototypes disappear quietly. It is an optimistic sign of progress toward solar powered energy, but it is not (yet) a sign of success.