NASA has used thermoelectric energy, or the conversion of waste heat to electricity, for decades to power spacecraft and the Mars Science Laboratory Rover. However, thermoelectric energy has attracted minimal attention in the alternative-energy world due to its limited commercial viability, until recently. Last year, Michigan State University (MSU) with the support of the Lawrence Berkley National Lab developed a new class of thermoelectrics using a compound called tetrahedrite that is believed to be more cost-effective and has the potential for everyday use.
One start-up finding success building on the findings from MSU is Alphabet Energy. They have developed a stand-alone converter that converts hot-exhaust, often from a car’s tailpipe, into electricity, resulting in a more efficient vehicle. According to Alphabet Energy, these modules can deliver up to 850 watts of power and can also be stacked together to capture heat from a variety of larger sources, including a power plant chimney.
Questions remain, however, about the scalability of these technologies. According to Michigan State University, thermoelectricity has previously failed to be commercialized because of low efficiency, high costs, and the required use of rare elements. Despite billions in investment from companies such as KPCB, BP Alternative Energy, and Mitsui Ventures, there has been limited success to date. The Department of Energy’s Energy Efficiency and Renewable Energy (EERE) program’s investments in waste heat energy have the goal of making overall vehicle fuel economy at least 7.5 percent more efficient by 2020. However, EERE recognizes that research still needs to overcome numerous technical barriers, including scaling-up of technology and availability of materials.
By Bill Brandon Owner, IESP consultants
I think the first major deployment of these technologies would be in transportation. Ricardo, an automotive technology company, has advocated for years that fuel efficient design should be coupled with a ‘light hybrid’ design where everything is taken of the engine power system except the wheels. Even using waste heat through a turbo charger puts drag on the engine. Changing from a turbo charger to an electric driven supercharger will give more flexibility to how the ‘boost’ can be utilized. It would allow the designing of a true ‘flex’ vehicle that can be optimized for both petroleum fuels and high octane ethanol blend while still promoting aggressive down sizing. It could also potentially be used for fuel cell vehicles where there is significant waste heat. These technologies will change our views on battery powered vehicles that are weight encumbered.
By Dan Miller Managing Director, The Roda Group
Heat exchangers are included on most fossil fuel power plants so that waste heat is recycled back to the boilers and used to generate more electricity.
The fact that so much waste heat is available on an internal combustion engine (ICE) car is an indication that it is an inefficient method of powering a vehicle. Yes, thermoelectric energy generation can recapture some of the wasted energy, but a better way to go is to use batteries and electric motors to power personal transportation vehicles. They are inherently twice as efficient in converting energy to useful motion.
For some applications, such as long-distance trucks, batteries are not practical yet and thermoelectric generators may improve their efficiency somewhat. But rather than make a policy specific to thermoelectric generators, a policy that sets requirements for mileage (CAFE), emissions per km, or one that puts a price on carbon would be more appropriate. With a high-level requirement, engineers can figure out which technologies can most cost effectively meet the goal.