Some UK universities are working on an ingenious project. When a gas is heated unevenly it produces pressure waves - basically sound waves. These pressure waves can be converted to electricity by the reverse process in which electricity is used to make sound from a loudspeaker. The group are designing a stove that burns wood or other biomass fuels that heats one end of a tube containing gas. This forms pressure waves which are then converted to electricity. A heat exchanger is powered by this electricity to drive a fridge. The stove can also be cooked on in the normal way. The stove will be most suited to developing countries as it will provide cooking, electricty and refridgeration all in one and with no need for a power supply (other than biomass fuel).
Read the full article at Nature.com Burning wood to power fridges.