Waste heat 55 Heat recovery 39 Waste-heat engines 30 Thermoelectricity 18 Heat 15 Transmission 15 Thermoelectric generators 14 Automobiles 10 Equipment and supplies 10 Fuel cells 10 Motors 10 Exhaust systems 6 Energy conservation 5 Humidity 4 Internal combustion engines 4 Maintenance and repair 4 Turbomachines 4 Cooling 3 Data processing service centers 3 Air conditioning 2 Energy consumption 2 Energy harvesting 2 Engines 2 Fluid dynamics 2 Gearing 2 Heat storage 2 Power resources 2 Product design 2 Shafting 2 Solar air conditioning 2