Will Waste Heat Be Our Next Power Source?0

Michael Kanellos | Wed Mar 30 2011 |


It’s one of the world’s most ubiquitous sources of energy and it’s barely been tapped.

And there’s probably a source of it a few feet away.

I speak of waste heat, the warmth that comes off of industrial equipment, household appliances and notebook power bricks. Waste heat is essentially electricity or petroleum that you paid for but likely didn’t get to use in a productive manner. Whenever AC current gets converted to DC, or the engine in your car kicks into action, the result is waste heat.

While a little heat from a notebook or a cell phone doesn’t seem like a maelstrom, the cumulative effect of waste heat is staggering. Back in 2008, researchers at UC Berkeley estimated that the U.S. consumes 100 quadrillion BTUs, or quads, of energy a year and that 55 to 60 of those quads get dissipated as waste heat. The Wartsila-Sulzer two-stroke diesel engine for ships is considered one of the most efficient in the world: half of the energy gets converted to waste heat.

Half, and in many cases more, of the energy in quite a large number of data centers gets consumed by air conditioners to get rid of waste heat. Think of it: half of the power bill goes to getting rid of another form of energy that cost you money but you couldn’t use.

Sean Casten, CEO of Recycled Energy Development (RED) puts it another way. Approximately 42 percent of carbon dioxide emissions come from power plants and power plants in general hover around a 33 percent efficiency when you add in all of the losses. That means that 28 percent of the carbon dioxide output in the U.S. goes to waste heat. We could cut more than a quarter of our greenhouse gases without crimping the national lifestyle if a silver waste heat recovery bullet existed.

Luckily, help is on the way. Companies like RED and China’s Recycling Energy Corporation are landing contracts to retrofit factories in a way that captures ambient heat, compresses it, and converts it to industrial grade heat or electricity. West Virginia Alloys, a silicon manufacturer, has retained RED to recover 45 megawatts of waste heat from its 120 megawatt footprint. In the past, the company opened the factory doors to cool off.

Echogen says it can exploit a fluid called supercritical carbon dioxide (ScCO2) to convert heat into power for less than four cents per kilowatt-hour. The average retail price of electricity in the U.S. hovers above 9.5 cents.

On the total opposite end of the spectrum, companies such as Komatsu, Alphabet Energy and Phononic Devices are devising chips that can convert heat to power directly. No mechanical compression needed. Wrapping these around components in a car or truck could provide power to run the air conditioner, which in turn would boost mileage. Cogeneration like this could be a cheap, quick way to meet CAFE standards.

Like in many green fields, the challenge lay in the details. Heat from servers and computer equipment is “low grade,” i.e. not enough of it exists to make a recovery system worthwhile. Factories are complex environments too: the ambitious West Virginia Alloys project is taking longer than expected. And the chips from companies like Phononic are just coming out of the lab: earlier waste heat processors didn’t have the efficiency required.

It’s also locked in a perverse battle with efficiency. As motors and AC converters become better, the less heat they will generate.

Will it go mainstream or stay on the fringes? If anything, you have to admit that once you think about waste heat, you start to see it everywhere.