The majority of world energy supply at present is covered by fossil fuels; coal, oil and natural gas. The world wide resources for each of these fuels differ strongly. Coal still has the largest resources. Clean and efficient conversion of these fuels can slow down the rate of depletion and evidently reduce pollution.

Promising technologies for improvement of the conversion efficiency in electricity production are gas turbines, fuel cells, integrated cycles with gas turbines, fuel cells and/or steam cycles and gasification of coal, waste, biomass or even oil. Electricity conversion efficiencies up to 60 70% may become possible. At the moment, however, world wide electricity conversion efficiency is about 33% and developed countries up to 40%.

Promising technologies for improvement of the conversion efficiencies for the production of steam and heat are combined heat and power production (cogeneration) and heat pumps. Heat pumps can upgrade low temperature heat and can be applied in buildings (for heating, hot water and cooling) and in industry. They strongly increase the efficiencies compared to normal boilers.

Cogeneration can be applied as district heating and in industry. By the combined generation of heat and power, energy is saved. The efficiencies in cogeneration can be improved, mostly as a result in improving the electric efficiency but also by improving efficiencies of heat exchangers. The result of these improvements will be that the so-called power to heat ratio will increase.

In the transport sector the conversion of fuel to mechanical power can be improved by applying other engine concepts like electric powered engines and various types of fuel cell engines. A promising technology seems to be the proton-exchange-membrane (PEM) fuel cell. This type of fuel cell could reach efficiencies that are 2-3 times higher compared to the present-day internal combustion engine.