Heattoelectricity

Heat-to-electricity is the process of converting thermal energy into electrical energy. It underpins many power-generation systems, from large-scale plants to small waste-heat recovery devices, and also supports remote sensing and space applications. Conversion can occur directly through electrical generators that exploit temperature differences, or indirectly through cycles that first transform heat into mechanical work and then drive a generator.

The most common approaches fall into a few broad categories. Heat engines convert heat into mechanical work, which is then converted to electricity by a generator. Examples include steam turbines in Rankine-cycle plants, gas turbines in Brayton-cycle systems, and Stirling engines. The efficiency of heat engines is constrained by thermodynamics, notably the Carnot limit, and real systems achieve lower efficiencies due to irreversibilities and practical design limitations.

Thermoelectric generators use the Seebeck effect to produce electricity directly from a temperature gradient, with no moving parts. They are well suited for waste-heat recovery, space missions, and portable power where reliability and maintenance-free operation matter, though their efficiency remains modest and depends on material properties such as the dimensionless figure of merit zT.

Thermophotovoltaics convert thermal radiation from a hot source into electricity using photovoltaic cells tailored to the emitted spectrum. They offer potential for compact, high-temperature energy conversion, but require advances in materials and device design to reach high efficiencies.

Other concepts, such as thermionic generators, involve electron emission from heated electrodes and are mainly explored in niche applications.

Key considerations in heat-to-electricity systems include thermodynamic efficiency limits, material performance under high temperatures, cost, and integration with heat sources and electrical loads.