Green Tech

How's this for a tantalizing possibility: rather than install solar panels on your roof, the lost heat from your furnace could power your home.

That's not yet a product, but a growing number of scientists and clean-tech companies are trying to coax usable energy from smokestacks and other waste-heat sources.

A global push toward energy efficiency is prodding more industrial outfits to reuse heat from their operations that would otherwise be lost to the skies.

Meanwhile, improving thermoelectric technology that converts heat into electricity is being fitted onto everything from car exhaust pipes to furnace flues.

It's a sign that energy efficiency, which often takes a backseat to renewable energy or alternative fuels, is getting more attention from technology innovators.

One company, GMZ Energy which was formed earlier this year by researchers from Boston College and the Massachusetts Institute of Technology, is taking a high-tech path to waste-heat recovery.

It has developed a nanomaterial-manufacturing process that improves the efficiency of existing thermoelectric modules, which are usually made from bismuth telluride and look something like a computer chip.

Thermoelectric devices can work in two directions: passing an electrical current through a module creates heat on one side and cooling on the other. Working in the reverse, applying heat to a device will create electricity.

Initially, GMZ Energy plans to sell modules to the existing market for cooling in small refrigerators or server racks, CEO Mike Clary said. The bigger market--on the order of billions of dollars--is converting waste heat from smokestacks or industrial equipment to electricity, he said.

"Eventually, we're going to see a tremendous amount of waste heat recovery applications, but that's 5 to 10 years off," Clary said. "We have to get to that 10 percent efficiency threshold to start making it viable."

Clary said appliance maker Bosch has shown interest in making a home-heating unit with an attachment that makes electricity from exhaust heat. At 10 percent efficiency, a home could meet its power needs with the heat on.

GMZ's prototype modules now operate at about 7 percent efficiency, 30 percent or 40 percent better for cooling than existing devices, Clary said.

A thermoelectric module, which one company intends to use for harvesting waste heat to make electricity.

(Credit: Martin LaMonica/CNET News)

The company, which got its seed funding from venture capital firm Kleiner Perkins Caufield & Byers, is looking to raise a round of funding in September to set up assembly operations in China, Clary said.

It is also readying a technical paper to show that its manufacturing process, where material is milled and then repressed into an ingot, works with both bismuth antimony telluride and silicon germanium for high-temperature applications.

Make steam, make juice
Automakers, too, are investigating heat recovery through thermoelectric devices.

BMW and General Motors are reviving work in this area and plan to test attachments to exhaust pipes next year. So far, research indicates that mileage could be improved by about 5 percent, or 1 mile per gallon, on a Chevrolet Suburban.

GMZ Energy's Clary thinks that automakers' interest in thermoelectrics is one reason the market is likely to take shape. He also notes that many researchers are working in the area.

But even before any breakthroughs in advanced materials, many people consider waste heat recovery the proverbial low-hanging fruit in energy efficiency.

"The market is a lot of wasted energy, and that is, by definition, a zero-cost feedstock," said Roger Ballentine, president of Green Strategies and a clean-tech investor. "That's a pretty attractive proposition."

A traditional heat recovery system. Click to see larger image.

(Credit: Recycled Energy Development)

Ballentine has consulted for China Energy Recovery, a Shanghai-based company that says it can capture 90 percent of energy that would otherwise be lost.

Efficiency, in general, is less sexy than renewable-power generation, an area that attracts more entrepreneurs and investors. But the economics of efficiency are usually better, said Ballentine, who expects to see more growth in heat recovery.

"If energy prices keep going up, the economics keep getting better," he said.

Co-generation plants, where both heat and electricity are produced, have been around for many years. Yet even though it is a cleaner form of power generation than burning fossil fuels, combined heat and power has held steady, at 9 percent of energy production, for several years, according to the World Alliance for Decentralized Energy.

Wasting away
The granddaddy of the waste heat recovery business is Recycled Energy Development, whose chairman, Thomas Casten, has been involved in energy-recycling projects for 30 years.

In projects at power plants or factories, the company places coils around a smokestack or other equipment to heat water. That hot water is then pumped back into the facility for heating or industrial processes. Or the hot water is turned into pressurized steam to make electricity in a turbine.

The amount of heat in a typical power plant that goes up in smoke is a "problem and an embarrassment," said Dick Munson, senior vice president at Recycled Energy Development, who spoke at the Virtual Energy Forum in June.

The average U.S. power plant uses three units of fuel to do one unit of power, meaning that two-thirds of the energy content is vented as waste, he said.

The efficiency of power plants in the United States has not improved in 50 years, while industry in Denmark has managed to increase efficiency 60 percent in the last three years, he said.

One customer is taking wasted energy from a steel smelter to make 220 megawatts of electricity. That's on the order of a single large solar-power plant. Through waste heat recovery, the U.S. could generate the equivalent of 400 coal-fired power plants, Munson said.

Polices need to be updated to better favor efficiency, Munson argued. Another barrier to industrial-scale heat-recycling projects is high capital costs, Ballentine added.

But one of the biggest impediments to heat recovery is changing the mind-set of building operators and product designers.

That's even truer of thermoelectric technology, which still needs to improve before more people look at it seriously, said GMZ Energy's Clary. A hybrid car or diesel truck, for example, could improve efficiency, as could a solar-thermal power generator.

"New ways of thinking like that just don't happen overnight in complex systems that have complex product cycles," he said. "As people get dialed into it, and the performance goes up, it will take off."

Researchers are trying to find a useful outlet for cars' waste heat--namely their electrical load.

General Motors and BMW plan to test devices that will convert excess heat from a car's motor into electricity next year, according to an Associated Press report Sunday.

GM has built a prototype, a metal-plated device that will fit around an exhaust pipe. Researchers told AP that they expect that it could improve fuel efficiency in a Chevrolet Suburban by about 5 percent, or 1 mile per gallon. The improvements would be greater in smaller, more fuel-efficient vehicles.

Auto companies are working with thermoelectrics researchers at Ohio State University to improve the efficiency of existing materials by producing an electric current from differences in temperature.

Researchers estimate that 30 percent to 40 percent of the heat generated from a car's engine is used. The rest is lost through exhaust or engine cooling.

Thermoelectric devices are already used in space exploration and in more commonplace applications, such as like cooling car seats. But research in the area, some of which was abandoned decades ago, is perking up as businesses explore new energy efficiency technologies.

Researchers at Pennsylvania State University on Friday said they have developed a polymer material they hope can be used to cool computers or refrigerators. These specially designed plastics would go into solid-state refrigerators that eliminate the use ozone-damaging freon in traditional power-hungry refrigerators.

A commercially available thermoelectric module connected to a solar panel. When current goes through the device, one side heats up, while the other cools. Researchers are developing more efficient materials.

(Credit: Martin LaMonica/CNET News)

Besides automakers, a couple of other companies are trying to commercialize thermoelectric technology.

Promethean Power is developing a solar-powered refrigerator that will use a thermoelectric module for cooling.

Another company, GMZ Energy, earlier this year received seed funding from Kleiner Perkins Caufield & Byers to develop thermoelectric materials using nanotechnology for refrigeration, air conditioning, waste heat recovery, and solar thermoelectrics.

Promethean Power Systems is an MIT spin-off that's swinging for the fences: using cutting-edge thermoelectronic technology, it wants to build a solar-powered refrigerator with no moving parts.

It plans to show off a prototype unit, designed specifically for rural areas in India, at the Emerging Technologies conference at the Massachusetts Institute of Technology next month.

If successful, the company's end product will be a small building to store milk, medicines, or other perishable goods in India and other places that don't have reliable electricity.

An artist's rendering of solar-powered cold storage unit.

(Credit: Promethean Power)

On the roof will be a small array of solar panels. Inside will be electronic components which use thermooelectric modules--essentially a semiconductor material sandwiched between ceramic tiles. These devices will convert electricity from the solar panels into cold air.

Thermoelectric modules, typically made out of bismuth telluride, are already used in low-energy applications like cooling car seats or computer chips. Promethean Power and a handful of other companies are trying to marry the technology to renewable energy and apply it far more broadly.

Because current thermoelectric cooling isn't very efficient, the key technical challenge is designing a system that's energy-efficient enough to be commercially viable.

On the business side, selling high-tech gear to poor countries sounds like a difficult proposition. Some people have suggested that Promethean Power adapt the technology to high-end products like picnic bags that can cool drinks with mini-solar panels.

But co-founder Sorin Grama says the company's market research has identified a business customer with money to spend, namely food distributors and processors in India looking for an alternative to costly diesel generators.

"That's where the money is. That's the kind of billion-dollar market that can sustain this kind of business," Grama said. "Anything else is just a niche."

With a storage unit that runs in part on solar power, these food or dairy companies can rely less on costly--and heavily polluting--backup diesel generators. Also, they will be able to collect produce or milk from farmers once, rather than many times, a day and save on transportation costs.

If the technology is cost-effective, it can be adapted to many uses, he said.

Plotting a new technology path
Solar panels or another renewable energy resource could already power a traditional compressor-based cooling unit. But the energy needs are very high and would require a lot of expensive solar panels.

Promethean Power itself started out trying to commercialize a process developed by MIT students that uses the sun's heat and an organic Rankine cycle to make electricity for cooling. Another approach is adapting an evaporative cooler for refrigeration.

A thermoelectric module connected to a small solar panel. With electricity, one side gets hot and the other cools.

(Credit: Martin LaMonica/CNET News)

But after they couldn't get an exclusive license for the original technology approach, Grama and co-founder Sam White chose to take a new path to the same market. The solar-thermelectronics combination gives the company a shot at breaking new ground technically, using solid state electronics.

"The old technology doesn't have as much room to improve," Grama said. "We're riding the wave of cheaper PV (photovoltaics) and thermoelectronics getting better."

In a phenomenon known as the Peltier effect, when current passes through a thermoelectric material, one side gets hot and the other cools. So the cold storage unit will also have to wick away a substantial amount of heat and isolate the cooling.

The plan is to make ice during the day using the solar panels. That stored ice will provide cooling at night or when the sun isn't shining.

It's an arrangement that won't eliminate the need for a diesel generator but a distributor or food processing company can use a smaller portable generator and save on fuel, said White.

Disruptive?
Right now, Grama and a handful of collaborators are writing the software for the embedded electronic controllers to make the cooling mechanism energy-efficient enough to work with a small number of solar panels.

Other companies and researchers are trying to find ways of tapping the thermoelectric effect in different ways, such as taking waste heat from car exhaust systems and turning it into electricity.

Promethean Power Systems co-founders Sorin Grama (left) and Sam White across the street from their Harvard Square, Cambridge office.

(Credit: Martin LaMonica/CNET News)

GMZ Energy earlier this year received seed funding from Kleiner, Perkins, Caufield & Byers to develop and commercialize thermoelectrics using nanotechnology.

The Boston area company, which is building off of research from Boston College and MIT, intends to make low-cost materials for use in refrigeration, air conditioning, waste heat recovery, and solar thermoelectrics.

After finishing its prototype, Promethean Power intends to look for outside funding. After deciding to take a very different tack to solar-powered refrigeration, it decided to keep thing small and low-budget.

It has been funded by angel investors, the founders, and received some money from an MIT business idea grant. It's building its prototype with equipment donated from suppliers, including National Instruments.

"It's amazing what not having a lot of money will do. You can't afford to make a lot of mistakes," said White.

Update: The headline on this story was corrected to indicate that the research stems from nanotechnology.

Boston College and the Massachusetts Institute of Technology said Thursday they have developed a more efficient way to generate electricity from heat, a technology that could let product designers harness "waste" heat.

Researchers said the implications of efficient thermoelectric materials could be wide: car electronics could be partly powered by the heat captured from exhaust pipes, for example, and solar electric panels could become more productive.

The thermoelectric effect, known since the early 19th century, is when certain materials convert heat into electricity and vice versa. The problem has been that those materials often lose heat quickly as well.

Boston College and MIT researchers have been experimenting with using nanotechnology to increase the efficiency of thermoelectricity.

They broke down bismuth antimony telluride, a commonly used semiconductor alloy, and reconstituted it in a way that slowed the passage of phonons, caused by vibration, through it.

The result is far more efficient process, the researchers said.

"By using nanotechnology, we have found a way to improve an old material by breaking it up and then rebuilding it in a composite of nanostructures in bulk form," said Boston College physicist Zhifeng Ren, one of the leaders of the project, said in a statement.

The advantage of using bismuth antimony telluride as a material is that it's relatively inexpensive, environmentally friendly, and can be used in a wide range of products, including embedded chips in electronics, according to the researchers.