From Denmark

New power controller for CHP production in remote areas

Many areas of the world are not electrified. For such places a new power controller developed by Carlsen Power Electronics might be a simple solution to obtain cheap electricity and heat from renewable energy sources. The system was awarded first prize in the Danish part of the European Better Environment Awards for Industry 1997. The power controller enables wind and hydro systems to operate in stand-alone or grid-connected mode, or both, in such a way that the electrical voltage is kept stable and independent of variation in loading. The available power is primarily dissipated as electricity and surplus energy as heat. Manufacturers of hydro and wind systems have long wished to standardise production using only one type of electrical machine for both grid-connected and stand-alone systems. The Carlsen system uses only asynchronous motors as generators. Another advantage is that they are simple, cheap and need practically no maintenance. Construction, materials, maintenance and reliability have been carefully considered down to the last detail. The power controller and the hot-water storage tank are made of reusable materials.

Superheater for efficient electricity generation from waste

Waste-fired CHP plants often have corrosion problems at steam temperatures above 400C due to alkali, chlorides and particles in the flue gas. This limits the electrical power output from traditional plants.

A potential solution has been found by the Danish firm COWI and a demonstration project has been established. A straw carboniser, from which pyrolysis gas is extracted and used as fuel in the burner of a separate steam superheater to boost the steam temperature. The straw is heated to a temperature of 600C without the presence of oxygen, a process which separates it into char and combustible gases with a very low alkali and chloride content. The gases are further cleaned for particles in a cyclone before being burned. The char residue is utilised in an ordinary boiler where the metal surface temperatures are lower and consequently the risk of corrosion is limited. The operational experience so far is positive and the output according to expectations.

For more information on these projects please contact the CADDET Danish National Team.

The CADDET Renewable Energy Newsletter is a quarterly magazine published by the CADDET Centre for Renewable Energy at ETSU, UK.

The articles published in the Newsletter reflect the opinions of the authors. They do not necessarily reflect the official view of CADDET.

Enquiries concerning the Newsletter should be addressed to
Pauline Toole, Editor, CADDET Centre for Renewable Energy, ETSU, Harwell, Oxfordshire OX11 0RA, United Kingdom. Tel: +44 1235 432968, Fax: +44 1235 433595.