Power Controller for remote areas
by the CADDET Danish National Team

Introduction

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.

Background

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.

Lighting

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.

Heating

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.

Local industry

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.

Available components

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.

Future potential

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.