  Industrial processes release substantial quantities of waste heat, which can
be harvested to generate electricity. At present, the conversion of low grade
waste heat to electricity relies solely on thermoelectric materials, but such
materials are expensive and have low thermodynamic efficiencies. Although
thermomagnetic materials may offer a promising alternative, their performance
remains to be evaluated, thereby hindering their real-world application. Here
we evaluate the efficiency and cost effectiveness of thermomagnetic materials
that can be used in motors, oscillators and generators for converting waste
heat to electricity. Our analysis reveals that up to temperature differences of
several 10 K the best thermomagnetic materials outperform thermoelectric
materials. Importantly, we find that the price per watt for some thermomagnetic
materials are much lower compared to present-day thermoelectrics and can become
competitive with conventional power plants. The materials library that we
present here enables the selection of the best available thermomagnetic
materials for harvesting waste heat and gives guidelines for their future
development.
