How to convert low waste heat into electricity?

It's estimated that as much as20 to50 percent of energy consumed in the world is dispersed as heat. We've seen waste heat harnessing technologies before that convert that loss back into usable energy, but usually they only work with high temperatures.

Out of a laboratory at EPFL, a start-up has come up with a way to harness waste heat as low as30 degrees Celsius (86 degrees Fahrenheit) to be converted to electricity. This new technology could see waste heat from things like waste incinerators, refineries and even data processors being used to make clean energy for buildings.

The technology is based on osmosis, as Phys.org explains is a "natural phenomenon that occurs when the concentration between two solutions separated by a membrane differs, for example between saltwater and freshwater. A stream flows from the less concentrated to the more concentrated solution, which tends to balance the concentrations on each side of the membrane. The mechanical energy of this stream may be converted into electrical energy by a turbine and an alternator. Heat is again used to separate the fluid into two separate solutions, one of which is more concentrated than the other. It is, therefore, a closed circuit (see image) that does not consume water."

The start-up's OsmoBlue technology works with any heat source whether it be air, water, gas or steam. The system would be connected on one side to the heat source and then on the other to the power grid. The company sees modular systems being used within buildings, set up near the cooling system.

So far, the technology has only been tested in digital demonstrations, but the team's models predict that10 megawatts of heat could produce between100 and600 kilowatts of electricity, which is about the equivalent of the power demand of100 homes.

The team is working on a prototype at EPFL and plans to have a pilot installation in place at a waste incinerator in2014.