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Report 3 of 4: Plug and Play
- South Africa
Introduction
In many parts of the developing world there is no electricity grid and diesel fuel may be expensive, of poor quality, or simply not available. Solar energy is a free and natural source of energy that will never run out. Solar photovoltaic systems convert sunlight directly into electricity. The photovoltaic cells are manufactured from silicon and assembled into modules that can be installed in a variety of ways to capture the sun’s power and meet energy needs.
Solar power is an attractive energy technology because photovoltaic modules produce no pollution, have an expected life of twenty years and require little maintenance. Furthermore, they are now technically proven, commercially available and economically viable. Small off grid photovoltaic systems of less than a few kilowatts are ideally suited to the conditions that prevail in the rural areas of many parts of the world.
The Power HouseTM
Shell International Renewables Limited and Eskom, South Africa’s national electricity supplier, have embarked upon a joint venture which supplies homes in the remote and rural communities of South Africa, with a unique solar home system. This project is the largest commercial solar rural electrification venture ever undertaken. The aim is to bring light to 50,000 rural homes in South Africa.
The Power HouseTM system has been designed by Shell Solar and Conlog (Pty) Limited. It has four main components: a solar panel, a charge controlled battery, a security system and a metering unit. All of these are prewired and already fitted with special plugs which is why the system is called "plug and play".
Security
The Power HouseTM has a SmartSwitchTM that protects the system from tampering and theft. The SmartSwitchTM prevents the major components, such as the solar panel or battery, from working unless they are connected to their associated control systems.
The Power HouseTM system is secure because it cannot be activated without a compatible token or magnetic card. The solar panel and/or battery cannot be used with any other device. The solar panel cannot be connected directly to the battery. The battery is housed in a single enclosure with the security system, charge/credit controller, token reader, termination panel and a prepayment device. This sealed housing unit ensures that only authorised persons have access to the battery and the controller electronics.
© Shell Renewables – The Power HouseTM is a totally integrated solar control system
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Location
The solar panel has to be positioned in the centre of a wooden pole, outside the home or other buildings, in a place where nothing can block the sun from reaching the panel. For example, it should be situated a good distance from the shadow cast by trees or other developments nearby.
Consideration also needs to be given to the direction that the panel is going to face which depends on the latitude of the country where it is being erected. In order to achieve the longest length of time of direct sunlight on the solar panel, the panel must be facing true north.
Electricity generation
Once the solar panel has been positioned correctly, the photovoltaic cells convert the daylight directly into electricity which is automatically stored in the charge controlled battery. The electricity being generated can be used straight away or it can be stored in the battery for use when the sun is not shining. On a cloudy day, electricity is still generated but not as efficiently. Heavy cloud and rain will prevent electricity from being generated at all. In these conditions, the household should use the electricity stored in the battery very sparingly. There is an indicator which shows the amount of electricity available in the battery.
The battery can only store a limited amount of energy. Appliances that generate heat such as irons, stoves, kettles and hot plates, use a large amount of electricity to function whereas lights, televisions and radios are ideally suited for solar energy because they only require a small supply of electricity to operate.
Cost and maintenance
The system is compact and easy to install. It is activated by a magnetic card which is paid for in advance and credited with 30 days power supply. This method guarantees revenue collection. If a payment is not made, then the system becomes disabled. The monthly payment also covers free maintenance, repair and replacement of the equipment and free exchange of light bulbs.
The Power HouseTM costs the equivalent of US$30 to install and the magnetic cards cost US$8 each month. Once the initial installation cost has been met, customers have found that the magnetic card are no more expensive than candles and paraffin but provide greater energy efficiency and are more sustainable. The prepayment system gives people an opportunity to install solar power without having to make a large capital investment in equipment that they might not have been able to afford previously.
User friendly
The Power HouseTM has been designed to be a customer friendly system. There is a simple electronic display that indicates the number of days of usage remaining before the load is disconnected and the charge remaining in the battery.
For further information, please contact:
NB: Power HouseTM is a registered trademark of Shell International. SmartSwitchTM is a registered trademark of Conlog (Pty) Ltd.
Intermediate Technology Development Group would like to acknowledge and thank Shell Renewables and Conlog (Pty) Limited for providing the original material on the Solar Power HouseTM system.
Further reading available from ITDG Development Bookshop
Solar Electric Systems for Africa
Mark Hankins
Describes how anyone, with help from an electrician, can adapt a small solar electric system to their own needs. Includes details on estimating local resources, choosing appliances and technology, wiring principles, and planning and maintenance.
Commonwealth Secretariat £14.00 1992 ISBN 0850924537
Solar Electricity: A practical guide to designing and installing small photovoltaic systems
Simon Roberts
Prentice Hall £29.99 1991 ISBN 0138250685
Solar-Powered Electricity: A survey of solar photovoltaic power in developing countries
Bernard McNelis with Anthony Derrick and Michael Starr
A state of the art survey of the use of photovoltaics in developing countries, in pumping, refrigerators, lighting, rural electrification and agriculture, from an UNESCO report.
ITP £14.95 1988 ISBN 0946688397
Who Owns the Sun? Preparing for the New Solar Economy
Berman & O'Connor
Green Books £12.95 1996 ISBN 189013208X
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This document is an output from a project funded by the UK Department for International Development (DFID) for the benefit of developing countries. The views expressed are not necessarily those of the DFID.
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