New Process Could Finally Turn Waste Heat Into Cheap Electricity

An advanced process based on osmosis will soon make it possible to economically produce electricity from waste heat as low as 30 degrees celsius, as emitted by installations like waste incinerators, refineries, or data centers. The start-up Osmoblue, based in the Swiss Institute of Technology EPFL’s Laboratory of Microsystems, has confirmed the feasibility of this new concept and started to assemble a first prototyp that could be soon followed by an industrial pilot project.

A large proportion of all energy that is currently consumed – between 20% to 50%, according to some studies – is dispersed as waste heat. Although it is already possible to recycle heat at temperatures over 150 degrees to produce electricity or to heat homes, the rest is simply released into the environment. At a time when companies are forced to be concerned with their environmental impact, this deficiency must be remedied.

Osmosis 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 that does not consume water. Though this concept has attracted significant investment, it has struggled to become a reality due to low yields.

With a team of seven people, the young entrepreneur has completed a digital laboratory demonstrator and a digital model for evaluating the performance of the product. "For example, it allowed us to estimate that 10 megawatts of heat could produce between 100 and 600 kilowatts of electricity, the consumption of one hundred homes," Elodie Dahan said.

The OsmoBlue technology is advantageous because it can be implemented with any heat source: air, water, gas, etc. The efficiency of the machine is both dependent on temperature and the nature of the hot and cold sources (air, water, gas, or steam). 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.