Power Controller for remote areas
by the CADDET Danish National Team
Despite easy access to wind or hydro power, about one third of the earth’s population has no electricity. Until recently, exploitation of these renewable energy
sources in areas with no electricity grid depended on relatively expensive synchronous generators. These need frequent maintenance, which in turn requires skilled labour. Now, a Danish engineer, Steen Carlsen, has
invented a simple Power Controller – an artificial electricity grid – which makes it possible to set up stand-alone power plants much more cheaply. These supply alternating current (ac) of a quality matching that
from large public grids and at a price that is only a fraction of that from traditional synchronous generators found in former stand-alone wind and hydro plant.
Pilot hydro power project with a Power Controller at an old water mill in Denmark.
In many rural areas of developing countries, electricity is generated by petrol or diesel
generators, which are expensive to run because of the cost of fuel. In addition, they emit carbon dioxide (CO2). Many villages have wind or water freely available, but
these resources are rarely used because most developing countries cannot afford technological investment in rural areas. In 1996, the first Power Controller was
donated to a village in the Peruvian Andes, where poor hygiene led to high infant mortality. The plant was rated at only 6 kW but today, four years later, the villagers have decided to upgrade it to 50 kW.
The Power Controller
The design of the Power Controller has been devised on the basis of the inventor’s
personal experiences when travelling in rural areas in the Himalayas and Africa. Some basic requirements for wind or micro-hydro power systems were identified.
The first was to provide a fixed voltage, thereby providing a better light source and
extending the lifetime of electric light bulbs. The Power Controller keeps the voltage stable and independent of variations either in the ac load or in the power supplied
from a turbine. Tests have shown voltage variations to be within a margin of 1%, which is crucial to the lifetime of a bulb. If a filament bulb receives 10% too high a
voltage, its lifetime will be reduced by about 70%. In developing countries, the installation of electric lamps instead of kerosene lamps has significant benefits, as
paraffin fumes in small rooms cause many health problems.
Another requirement was to use the surplus electricity to heat water and dwellings, reducing firewood consumption and improving hygiene. In many places, so much
firewood is chopped down that the resulting deforestation leaves the soil bare and vulnerable to erosion. Power to a village is supplied from a turbine-driven standard
asynchronous motor. The Power Controller maintains a fixed three-phase voltage for consumers by dissipating surplus power to a dump-load in the form of a heating cartridge in a hot water tank.
Of equal importance is power for small-scale industries and workshops, which can generate an income for the owners. A feature of the Power Controller is that it
deceives conventional electric motors into acting as if they were connected to a public grid. This allows cheap standard electric motors to be used as generators. Hence, it
enables ordinary wind and hydro systems to operate in stand-alone and/or grid-connected mode.
Construction, materials, maintenance and reliability of the system have been carefully
considered to the last detail. The electronic components are simple, cheap and need no maintenance. They have been selected carefully for their availability in small
electronic shops in developing countries. The Power Controller and the hot water storage tank (barrel) are made of re-usable materials.
In 1997, the system was awarded first prize in the Danish category of the European Better Environment Awards for Industry.
A typical village stand-alone system with a Power Controller.
After several years of development, the Power Controller has been demonstrated successfully in Peru and Denmark and is now ready for mass production.
Importantly, the Power Controller provides the opportunity to link up several systems
or villages. Apart from the technical and economic benefits, such partnerships provide valuable experience of running co-operatives.
Remote settlements in developed parts of the world represent another market. Such settlements frequently use diesel generators linked to expensive and
maintenance-demanding synchronous generators. In these areas, wind or hydro power may meet all or part of the energy requirement. Where, previously, special wind or
hydro turbines were required for such stand-alone sites, the Power Controller allows the use of standard grid-connected plant. This reduces construction costs and enables
consumers to save on the operational costs of maintenance and diesel.
For more information contact the CADDET Danish National Team in Tølløse.
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.