Power Chips are thermionic vacuums that produce electricity from waste heat. Thermionic vacuums are similar to thermoelectric devices, but they overcome some of the cost and performance inefficiencies that are typical of these devices. These devices can be used to recover waste heat in commercial and industrial applications, turning that heat into electricity.
Traditional thermoelectric devices work by the Seebeck effect, an electromotive effect that creates current by the heat-induced movement of electrons from a “hot” cathode to a “cold” anode. Essentially, the heat creates excited electrons in the conductive cathode material, which then flow to the anode. This forces the lower energy electrons from the cathode to the anode, completing a circuit. The downside to the thermoelectric effect is that the heat flows from the cathode to the anode as well, reducing the change in temperature and thus creating low conversion efficiencies of about 8-10% of theoretical maximums.
The makers of Power Chips claim to overcome this low conversion efficiency by creating a five nanometer gap between the cathode and anode in a vacuum. The surfaces of the conductors are composed of thin layers of gold, silicon oxides and titanium oxides etched at the nanoscale to allow for maximum electron flow and minimum gap spacing. This allows the chip to improve Carnot efficiency to around 50% of theoretical maximums. A one square centimeter Power Chip can produce 10 watts of power, and since the chips are modular, they can be scaled to large, megawatt size applications. These chips have the potential for commercial, industrial and utility scale waste heat and geothermal harvesting at a projected installed cost of $500-$1000 per kW.
- . Harnessing of Low Temperature Geothermal and Waste Heat Using Power Chips™ in Varmaraf Heat Exchangers. [Internet]. 2003 . Available from: http://www.powerchips.gi/press/IGC_Paper_15Sept03.pdf
Power chips have the potential to increase the recovery of waste and low-grade heat from industrial processes and low temperature geothermal as a cost-effective, modular retrofit.
The product is made using nanofabrication techniques rather than using nanomaterials so risk for release into the human or natural environment is likely low. Nanometer thin layers of silicon, titanium and gold are grown on silicon wafer substrate through chemical processes, negating the need for nanoparticles that can pose adverse effects. Risks are likely comparable to those associated with semiconductor manufacturing.