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When you work with your laptop on your lap, you can feel it. When you touch the hood of an idling car, it’s clearly there. What is it? Waste heat — a byproduct of processes that use, store, produce and transfer energy — and in recent years a growing amount of companies have been using innovations in nanotechnology to produce next-generation materials that can capture that waste heat and turn it into usable electricity.

These types of materials are called thermoelectrics and they employ the Seebeck effect to use the temperature difference between two semiconductors to produce a voltage. German physicist Thomas Seebeck discovered the phenomenon all the way back in the 1820s.

Fast forward almost two hundred years from the first discovery, and nanotechnology has started to break open this well-known effect, helping to deliver some novel products that can use energy more efficiently. Because semiconductors have different length scales for heat and electron transport, they can particularly benefit from nano-structured surfaces when being used for thermoelectric materials.

But one big problem with traditional thermoelectric materials is that they have often been created using expensive and rare materials, meaning they’ve been generally too expensive to produce at large volumes. And since the Seebeck effect tends to create a pretty small amount of electricity, the materials used have to be made relatively cheaply to justify their use.

Stealthy startup Silicium Energy has been developing a silicon-based thermoelectric device that uses a nanostructured material (sounds like nanowires specifically) to deliver more power at low costs. We first wrote about Silicium in 2011, and it uses research led by co-founder and CEO, Akram Boukai, at University of Michigan and Caltech. Venture capital firm Khosla Ventures invested in the company.

Silicium Energy is tackling a somewhat unusual market for thermoelectrics: wearable computing. While the startup has been shying away from the spotlight, it says on its website that its silicon thermoelectrics will help substantially increase the battery life for wearable computing.

A startup called Phononic has also been interested in using their thermoelectrics for consumer-focused devices. It has developed a solid-state heat pump out of its materials and it is using it in compressor-free refrigeration units, like super-quiet fridges and home wine chillers. The company says it intends for its technology to be used in refrigeration consumer products that are “quiet, energy efficient, toxin-free and require no moving parts.” Sheetak is another startup that’s focused on using thermoelectrics to make a cooling engine for fridges and coolers for consumers.

Phononic counts investors like Beijing-based Tsing Capital, as well as Valley investors Venrock and Oak Investment Partners. The company is currently building out 20,000 square feet of manufacturing in Durham, North Carolina, and is looking at Asia as a big market for its goods.

Other startups are tackling more traditional markets but with new nanotech products. GMZ Energy is focused on thermoelectrics in ultra-rugged and hot environments, like on the battlefield, on underwater oil and gas sites, or in vehicle exhaust systems. The company has developed a nano-engineered material that it says can be used at temperatures of 600C or more, is ultra strong, and costs less than previously used materials.

GMZ Energy says it has recently been selling test samples of this thermoelectric device to automotive companies to be used in their exhaust system to capture the waste heat and use it to power a vehicle’s electrical needs like lights, engine ignition, fans, instruments. Taking the electrical load off of the alternator can increase the efficiency of the engine by a couple percent, and cut fuel use slightly.

According to GMZ Energy, automotive companies are planning to start field testing these types of waste heat recycle systems around 2017 in preparation for a wider roll-out in 2020. GMZ is backed by Mitsui Ventures, I2BF Global Ventures, Energy Technology Ventures (the JV from GE, NRG Energy and ConocoPhillips), Kleiner Perkins Caufield & Byers and BP Alternative Energy.



Solar technology could benefit from thermoelectrics as well, if they’re cheap and durable enough. GMZ Energy had originally planned to launch its thermoelectrics in solar water heaters, but backed out of that market when solar prices crashed.

One of the first places that thermoelectrics might be widely used is in industrial and power plant applications, like flues or exhaust systems. Alphabet Energy is focusing on this market, and the startup already has one of its devices installed in an industrial facility in California that converts exhaust-gas waste heat into electricity. It also has received funding from Canadian natural gas giant Encana and Oakland VC Claremont Creek Ventures.

Alphabet Energy CEO Matt Scullin said thermoelectric materials are hitting a tipping point and have reached an important juncture:

Between huge technical advances over the past 10 years due to nanotechnology and government funding and the learning that cleantech has experienced, thermoelectrics are about to disrupt the energy industry.

All of this thermoelectric innovation from startups will be great for adding extra energy efficiency to devices, systems and vehicles, and it will be an important way to reduce carbon emissions. However, the road to commercialization is long and rocky for startups in this space. Large companies like the autogiants — BMW, Ford, Volkswagen — and GE are eyeing these technologies, too. Finally, legislation seems to be going the way of thermoelectrics, with the U.S. and Europe increasing vehicle efficiency standards.

That means companies and organizations, like never before, will want to find ways to recycle heat and reduce energy use using these next-gen materials.