Clean Power ORNL researchers harvest energy from machines

Published on May 17th, 2011 | by Tina Casey


More than Half of U.S. Energy Goes to Waste – But Not for Long

May 17th, 2011 by  

ORNL researchers harvest energy from machinesResearchers at the Oak Ridge National Laboratory estimate that the U.S. loses more than half the energy it generates. That doesn’t include heating and cooling loss from buildings,  just energy that vanishes into the atmosphere from machines, industrial processes and electronic equipment.  In order to reclaim and recycle some of this energy, the researchers are developing a highly efficient thermal waste heat energy converter. The new device would do double duty. It would cool down electronic equipment including photovoltaic cells in order to keep them functioning efficiently, while capturing the waste heat to generate electricity.

ORNLS’s New Thermal Energy Converter

The team is developing a device that is only about one millimeter square, and each one delivers only 10 milliwatts – at best. That sounds like a drop in the bucket but it’s nothing to sneeze at when you attach hundreds of these devices to, say, a tiny object such as a computer chip. The principle is based on pyroelectricity, which refers to the ability of some materials to produce a temporary charge when they are heated or cooled. The catch has been getting pyroelectric devices to operate at a high enough level of efficiency to make them cost-effective. The ORNL team came up with a relatively inexpensive cantilevered structure that promises to do just that (a cantilever, broadly speaking, is a structural beam supported only at one end).

Other Ways to Harvest Waste Energy from Machines

ORNL has gone the high tech road, which is years away from commercial development. However, more conventional means are already available. One example is an a new energy harvesting system up at Thule Air Force Base in the Arctic Circle, which captures exhaust heat from the facility’s generators. You can also harvest kinetic energy from a machine’s vibrations, or from the braking systems in vehicles, cranes, trains and other stop-and-go equipment.

Waste Heat as a Low Risk Energy Resource

Considering the amount of energy at stake, widespread use of thermal energy converters and other machine-based energy harvesting equipment is akin to discovering a new resource – one that can be safely harvested where humankind has already developed the natural environment, with virtually no additional disruption.  That’s a stunning contrast to high risk energy harvesting such as hydrofracking, deep sea oil drilling and mountaintop coal removal.

Harvesting Energy from Developed Lands

Machines and equipment are one area ripe for low-risk energy harvesting, and there are others. For example, the Nature Conservancy has pointed out that wind farms can disrupt habitats for endangered and at-risk species, but the solution is simple: there is ample space in the U.S. to exploit wind resources on developed lands, where habitat is not an issue. Similarly, the U.S. EPA has developed a program to build wind turbines and solar installations on brownfields and other classifiied sites that can’t be used for much else aside from further development.

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About the Author

specializes in military and corporate sustainability, advanced technology, emerging materials, biofuels, and water and wastewater issues. Tina’s articles are reposted frequently on Reuters, Scientific American, and many other sites. Views expressed are her own. Follow her on Twitter @TinaMCasey and Google+.

  • Rtastad

    I have driven by many oil refineries all over the US, and I see a huge pipe rising into the air, and a large flame coming from it, and I am curious as to why this energy is not harvested in some way?

  • Pingback: Update: Heat to Electricity Tech Happens at U Minn – CleanTechnica: Cleantech innovation news and views()

  • The Seebeck effect produces a small voltage at a junction of dissimilar metals (e.g. iron and aluminum wires), one connected to a heat source and the other connected to a heat sink.  That’s one option for waste heat power harvesting, at least on a tiny scale (voltages from the Seebeck effect are on the order of millivolts, but there is a lot of current, so there is considerable power). 

    Another is to use an organic Rankine cycle (ORC) so the heat source for power generation can be low temperature.  The working fluid is a high molecular weight refrigerant, instead of water.

    The worst waste of energy I know of is the heat rejection at thermal power plants.  Only about a third of the energy in coal becomes power, and the rest is rejected to the atmosphere through the cooling towers, along with a lot of fresh water.  Power plants consume more fresh water than any other activity, next to agriculture.  The turbine exhaust steam at power plants could be a resource for waste heat power harvesting with a little intelligent design.  Making that steam lose enthalpy doing useful work makes more sense than cooling by evaporating precious fresh water uselessly into the atmosphere. 

    And let’s not forget about the waste of 25TWh of curtailed wind last year.  Put that wind to work doing something useful, like grinding or pumping.  Wind’s highest and best use might well turn out to be something other than power generation. 

    • Anonymous

       I’d like to know more about that 25TW of curtailed wind.  The little bit of data that I’ve seen suggests that it might be very seasonal – in the spring when winds are high and we’re in between winter heating and summer air conditioning seasons.  And it might have been spread over a large geographic region.

      It might just not be practical to use some of the wind capacity that we have.  In order to have enough power when we need it we might need to overbuild for times when we don’t. 

      Or perhaps we need some very large CAES storage – fill up a few enormous caverns with seasonal wind that we could call on during peak-peak heat waves.  Wouldn’t cost anything to leave that compressed air sitting there.  Especially if we used the turbines for dispatchable backup in the meantime.

  • Spent nuclear fuel is another waste heat source much in the news as are unconventional oil formations, like Alberta’s oil sands, which require massive heat inputs to be produced.

    A logical solution to the problem of the former is to use it to overcome the problem of the latter.

  • The largest reservoirs of waste heat are the world’s oceans. They have accumulated close to 90 percent of the heat attributable to Climate Change and are expanding and melting the polar icecaps in the process. This damaging heat could provide all of the energy mankind will ever need by converting it to electrical energy with Ocean Thermal Energy conversion.

  • Anonymous

    Tina – you might want to add an energy use diagram to your article so that people can easily see where our energy comes from and how it’s used.    That puts the immense amount of waste into perspective.   Here’s one…

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