A typical petroleum powered generator is about 30% efficient, which means that more than two-thirds of the chemical energy in the fuel is wasted as heat, while only 30% is turned into usable electricity. To reduce the waste, Alphabet Energy recently released the E1, a solid state thermoelectric generator that takes waste heat from diesel-powered generators and converts it to electricity, increasing the efficiency of the generators by about 2.5%. That may not seem like a lot, but per unit, that slight improvement in efficiency can save about $50,000 in fuel cost and 156 tons of CO2 emissions every year. Put one of these on every generator and the impact becomes pretty significant.
Thermoelectric generators (TEGs) aren’t new; in fact, the Seebeck Effect - the property where a difference in temperature results in a voltage - was discovered by Thomas Johann Seebeck when Abraham Lincoln was reading books by candlelight at the age of twelve. (I’ll save you the trip to Google - that was 1821.) TEGs have two problems: they’re inefficient and costly. Alphabet Energy has developed a line of highly efficient silicon-based TEGs that cost significantly less than their counterparts that are made from more exotic materials, making the E1 an affordable option with a short payback period. Alphabet claims that the E1 is the world’s most powerful thermoelectric generator.
Hot exhaust is piped from the diesel generator into the E1 and passed through thirty-two TEG modules. The TEGs convert the heat to DC electricity, which is fed to an inverter that’s similar to a grid-tied inverter used in photovoltaic (PV) systems. The inverter converts the DC into AC that matches the voltage, frequency, and phase as the electricity coming out of the diesel generator. In effect, it’s as if the diesel generator was producing 2.5% more electrical power with the same amount of fuel.
What I really like about this is that the modules can be easily swapped out when they need replacement or when upgrades become available. And the lack of moving parts makes it highly reliable and nearly maintenance-free.
If you’re wondering how long one of these may last, Alphabet claims at least a ten-year life. I’m guessing that that’s the expected life of the associated electronics, since PV inverters typically last about ten years also. Thermoelectric devices have incredibly long lifespans. The Voyager spacecraft uses TEGs and it’s been travelling for nearly forty years, continually transmitting information back to its home planet.
Images and video courtesy of Alphabet Energy
I recently attended the Northern Illinois Renewable Energy Summit and Expo. A number of manufacturers described ways in which they’re reducing energy consumption. Although the E1 is designed to run off of the exhaust from a diesel generator, I’m sure the basic design can be applied to waste heat caused by many industrial processes.
Click here to learn more about thermoelectric devices.