About 20% to 50% of the energy consumed is dispersed as heat. With current technologies minimum of 150 degree is needed to harness the waste heat for electricity production or home heating, the rest is simply released into the environment. Start-up OsmoBlue, Switzerland, has developed a process based on the principle of osmosis to convert heat over 30 degree Celsius into electricity.
Osmosis is a natural phenomenon that occurs when the concentration between two solutions separated by a membrane differs. 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 that does not consume water.
The OsmoBlue technology is advantageous because it can be implemented with any heat source: air, water, gas, etc. Connected on one side to the heat source and the other to the power grid, modular systems could eventually be installed in existing structures, near the company’s cooling system.
So far the concept has only been tested in the digital laboratory demonstrator, but OsmoBlue estimates that 10 MW of heat could produce between 100 kW and 600 kW of electricity, which is enough to power 100 homes.
A first prototype is currently being manufactured at EPFL. A pilot unit on a larger scale could then be installed in a regional waste incineration company in 2014.