Boosting thermoelectric efficiency
Each year, approximately 15 TW of thermal power are dissipated and lost by industrial, transport and power generation activities. Thermoelectric generators (TEGs) that transform this waste heat into useful electricity could make an important contribution to renewable energy production. However, material performances hitherto have been blocking their industrial development. Scientists enhanced the performance of promising thermoelectric materials with EU funding of the project 'Nanoparticle embedded in alloy thermoelectrics' (NEAT). Recently, such materials with nano-scale structural characteristics were shown to have thermoelectric performances up to three times better than conventional materials. However, these results were obtained for thin films and were not reproducible in bulk materials. NEAT developed an innovative bulk alloy nanocomposite approach to increase the performance of eco-friendly silicon-based thermoelectric materials above the state of the art. These materials were capable of attaining very high thermoelectric performances at high and medium temperatures by considerably decreasing the lattice thermal conductivity. In particular, by incorporating well-controlled nanoparticles in silicon–germanium nanocomposites, NEAT demonstrated a 40 % decrease in the cost of this thermoelectric bulk alloy material. This was due to the lower content of the expensive and scarce germanium. This alloy could find application in autonomous systems and thermal sensors. With significantly lower thermal conductivity of the magnesium–silicon–tin alloy, scientists used smaller nanoparticle amounts to improve its thermoelectric performance. This host matrix material demonstrated the strongest thermoelectric effect ever reported for bulk materials at low temperatures (below 500 degrees Celsius). Being non-toxic, it could substitute the commonly used bismuth telluride in the automotive sector. NEAT demonstrated the scale-up feasibility of synthesising and sintering eco-compatible, cheap and abundant host matrix alloys at a pre-industrial scale. It thus made a first step toward building a strong supply chain in the embryonic TEG industry. For transport, industrial processes and power generation in Europe alone, NEAT estimates a recovery of 200 TWh by 2020.
Keywords
Bulk alloy nanocomposite, energy-harvesting, transport, power generation, thermoelectric generators