Reducing CO2 emission by
Renewable energy

Renewable energy resources have a vast potential world wide, but are a diffuse source of energy. Nowadays they are only partially developed to a commercial status. Only traditional biomass use and large scale hydropower contribute significantly (17%) to the world wide energy supply. There is a variety of 'new' renewable energy resources such as solar, wind, modern biomass and organic waste, geothermal and several ocean resources. Besides this variety in resources there is also a wide variety in conversion technologies to convert these resources in energy carriers like electricity, fuels or hot water.

Some promising renewable energy technologies are briefly described.

  • The costs of electricity produced by solar photovoltaic systems (PV) are nowadays some factors higher than electricity from the grid. However, there are several applications and market niches in which PV systems are economic attractive. The sales of PV has increased considerably the last years and now have a rate of about 60 MWp. Expectations are that PV systems can become competitive with electricity from the grid within several decades, especially in regions with a hight irradiation. Several PV technologies are under development; a promising technology for the future seems to be the thin-film solar cells.

  • Biomass is already playing an important role in global energy supply, but especially in less developed countries. Although the use of biomass, mostly as fuel wood and charcoal, in many cases can not be seen as sustainable. The use of biomass in a more advanced way is to convert biomass and/or organic waste streams in an energy carrier such as electricity, methanol, hydrogen or bio-diesel. There is a whole range of techniques under development for these conversion processes. A promising technology for conversion of biomass into electricity is biomass gasification integrated with the use of gas turbine and/or fuel cell technology. In the long term electric conversion efficiencies of 55% seem to be technologically possible.

  • During the last decade the costs of producing electricity with wind turbines has decreased considerably to about 0.05-0.10 $/kWh. Technology improvements by advanced blade design, improved control, application of new materials and better siting are still possible and will reduce costs to about 0.03-0.05 $/kWh. At the end of 1994 about 4000 MWe wind power has been installed and various countries have reasonably large programs for the further introduction of wind turbines such as the U.S., Denmark, U.K. Germany, India, China and the Netherlands.

  • Low temperature hot water from geothermal sources can be used directly for heating green houses, buildings and as a source for heat pumps. Dry steam and high temperature water from geothermal sources can be used for electricity production.