Green conversion of heat to electricity

May 21, 2013 by Cécilia Carron
Green conversion of heat to electricity
Credit: 2013 Alain Herzog

Soon, it will be possible to produce electricity from heat over 30 degrees emitted from a waste incinerator, refinery, or data processor. The start-up Osmoblue has just confirmed the feasibility of this new concept.

A large proportion of the energy consumed – between 20% to 50%, according to some studies – is dispersed as 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 , this deficiency must be remedied. The start-up OsmoBlue, based in EPFL's Laboratory of Microsystems, developed a process based on the principle of osmosis to convert heat over 30 degrees into electricity.

Osmosis is a 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 of this stream may be converted into 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. Though this concept has attracted significant investment, it has struggled to become a reality due to low yields.

The OsmoBlue technology is advantageous because it can be implemented with any : 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 , modular systems could eventually be installed in existing structures, near the company's .

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."

It was during a postdoctoral fellowship at Harvard University in the United States that Elodie Dahan had the idea to revisit the method of osmosis. Components have been revised in light of recent advances in materials engineering and microtechnology. 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.

Explore further: Going nuts? Turkey looks to pistachios to heat new eco-city

More information:

Related Stories

Innovative self-cooling, thermoelectric system developed

Apr 11, 2013

Spanish researchers at the UPNA/NUP-Public University of Navarre have produced a prototype of a self-cooling thermoelectric device that achieves "free" cooling of over 30ºC in devices that give off heat. It is a piece of ...

Energy-efficient water purification

Jan 14, 2009

Water and energy are two resources on which modern society depends. As demands for these increase, researchers look to alternative technologies that promise both sustainability and reduced environmental impact. Engineered ...

Drinking water from the sea using solar energy

Jul 31, 2012

One of the main ways to obtain drinking water in hot, dry countries surrounded by sea or ocean is through desalination. European researchers developed a high-efficiency and low-cost desalination technology ...

'Waste heat' may economize CO2 capture

Mar 28, 2013

In some of the first results from a federally funded initiative to find new ways of capturing carbon dioxide (CO2) from coal-fired power plants, Rice University scientists have found that CO2 can be removed ...

Energy harvesters transform waste into electricity

May 16, 2011

Billions of dollars lost each year as waste heat from industrial processes can be converted into electricity with a technology being developed at the Department of Energy's Oak Ridge National Laboratory.

Recommended for you

Obama launches measures to support solar energy in US

Apr 17, 2014

The White House Thursday announced a series of measures aimed at increasing solar energy production in the United States, particularly by encouraging the installation of solar panels in public spaces.

Tailored approach key to cookstove uptake

Apr 17, 2014

Worldwide, programs aiming to give safe, efficient cooking stoves to people in developing countries haven't had complete success—and local research has looked into why.

User comments : 8

Adjust slider to filter visible comments by rank

Display comments: newest first

1 / 5 (3) May 21, 2013
Imagine how this could increase efficiency in an electric vehicle- recharging batteries from heat generated from its motor, transmission, axles, and the overweight driver's seat.
2 / 5 (5) May 21, 2013
100 kw out of 10mw....1% increase....keep trying.
2.8 / 5 (5) May 21, 2013
Imagine how this could increase efficiency in an electric vehicle- recharging batteries from heat generated from its motor

Not much, since these motors are already very efficient. EVs use the on-board stored energy to about 80%. And most of the losses comes from the batteries and not the motor.

This is more useful for largeish powerplants where a percent (or even a tenth of a percent) in gains quickly translates into big bucks which merits the added installation cost/complexity/maintenance of such systems.
2.3 / 5 (3) May 21, 2013
What about the high temperatures from the vehicle's batteries? Wouldn't it be wise to convert that waste heat while cooling them- critical to their lifespan?
3 / 5 (3) May 21, 2013
Since you have to get to a temperature differential of 30 degrees above ambient temperature for this to work...I really doubt it makes much sense in an EV.
While one could say that in winter that would work it's rather advantageous to keep the batteries at temperature during cold days (as too low temperatures reduce battery efficiency even more)

Especially taken into consideration the added weight and complexity of the system - which translates into added purchasing and mainenance costs.

I'm sure they will do a calculation for that, but my gut feeling is that it isn't worth it. Even if it delivers 1% more current EV ranges that'd be 1-2 extra kilometers.

I'm think the avenue Ford is taking with the more efficient AC has a lot more potential in that regard.
3 / 5 (2) May 21, 2013
There wouldn't be any cumbersome equipment adding weight or complexity considering that thermoelectric materials today are remarkably simple and efficient :

1 / 5 (1) May 22, 2013
30 degree differential to produce a current? Sounds like it could become ubiquitous.
1 / 5 (1) May 22, 2013
There wouldn't be any cumbersome equipment adding weight

Their setup require a closed liquid system. The amount of weight you can add before killing a 1% increase in range is around 25 pounds (and you only get a 1% increase with optimal conditions for this system. Real life conditions aren't optimal most of the time).

Until I see a prototype in a car under real conditions this doesn't sound very promising for such small scale applications. For powerplants it's all good, though (maybe even for home solar thermal setups, where excess warm water can be usd to make some electricity. But there the power output is likely too low to merit the installation cost).

More news stories

Finnish inventor rethinks design of the axe

( —Finnish inventor Heikki Kärnä is the man behind the Vipukirves Leveraxe, which is a precision tool for splitting firewood. He designed the tool to make the job easier and more efficient, with ...

Making graphene in your kitchen

Graphene has been touted as a wonder material—the world's thinnest substance, but super-strong. Now scientists say it is so easy to make you could produce some in your kitchen.

Poll: Big Bang a big question for most Americans

Few Americans question that smoking causes cancer. But they have more skepticism than confidence in global warming, the age of the Earth and evolution and have the most trouble believing a Big Bang created the universe 13.8 ...