Before revision: More exotic technologies have also been proposed: thermoelectric (including graphene-based thermal power conversionTechnology Review, March 5, 2012: Graphene Battery Turns Ambient Heat Into Electric CurrentScientific Reports, Aug. 22, 2012: Graphene-based photovoltaic cells for near-field thermal energy conversionMIT News, Oct. 7, 2011: Graphene shows unusual thermoelectric response to light), pyroelectric, thermophotovoltaic, thermionic and magnetohydrodynamic type thermoelectric materials.
After revision: More exotic technologies have also been proposed: thermoelectric (including graphene-based thermal power conversionTechnology Review, March 5, 2012: Graphene Battery Turns Ambient Heat Into Electric Current Scientific Reports, Aug. 22, 2012: Graphene-based photovoltaic cells for near-field thermal energy conversionMIT News, Oct. 7, 2011: Graphene shows unusual thermoelectric response to light), pyroelectric, thermophotovoltaic, thermionic and magnetohydrodynamic type thermoelectric materials.