It is well documented that the introduction of electricity supply improves the standard of living in off grid, typically rural, areas. Some of the benefits include education and entertainment via television, security from street lighting, small business development including welding, wood working, cooking, drying and milling of cereals, freezing of produce such as fish, etc. Light also allows children to study later than daylight hours while adults can read, watch television or gather socially. The list of benefits goes on. Clearly it is desirable to bring power to areas not connected to the grid.

Unfortunately, providing power to off grid communities is not simply the delivery and installation of power generation equipment. There are documented pitfalls where charitable organisations have supplied power generation equipment only to have the equipment fall into disrepair and disuse within months of installation. So what are some of the pitfalls of sustainable rural electrification?

Pitfalls

The first pitfall is what energy source is available. If it is a fuel, what type of fuel is it? What power generation technology is suitable for using this fuel? Is the fuel supply sustainable?

Having found an appropriate fuel, are there sufficient technical skills available in the community to operate and maintain the power generation equipment? If the equipment involves rotating parts, what is the availability and cost of spares? Can the community afford the capital cost? What about cable theft or vandalism? Finally, is the community willing and able to pay for the power? These latter pitfalls in particular require “buy in” from the community.

How can gasification meet these challenges?

While gasification is a relatively sophisticated technology, it is both robust and easy to operate. It can also be “dumbed down” to meet the challenges mentioned above by careful selection of the process and the equipment to be used. Below are some technical ideas that can make gasification a suitable and cost effective technology for rural electrification:

Second hand petrol engines: a Ford or Toyota 3 litre motor sells for $1200 and it can generate 20kVA with wood gas. These motors are found all over Africa meaning that spares are available and more to the point, can be overhauled locally. Overhaul costs are low and in the region of $400 for new pistons and rings. Heavy duty cast iron ST generators: a 20kVA generator with AVR sells for <$1500. ST drives have brushes and springs as consumables that are easy to replace even with very basic skills.

12V drives: windscreen wiper motors can turn feeders, radiator fans can be used for cooling, bilge pumps can be used for pumping. Wiper motors and radiator fans have the benefit of being able to be swopped out for another available unit with minor modification of the mountings. Bilge pumps simply get dropped into the vessel to be pumped from.

Integration of drying with gasification: frequently the fuel available is too wet for proper gasification to take place. As such, a biomass dryer/pre-heater should be integrated into the design of the gasifier. This can be done by using heat recovered from the engine exhaust.

Power distribution: Finally, the easiest method of power distribution is to use the “telephone line” system using galvanised wire. Ceramic isolators or isolators used for electric fences are readily available. If none are available, soda bottles work just as well.

Heat utilisation: one use of the heat given off by the engine is to use it to heat stoves on which food can be cooked. The best way to do this is to duct the exhaust gas into steel stove chambers before being vented the gas to atmosphere. The stove top is fitted with fins to aid heat transfer from the gas to the metal top. As the gas travels through the chamber, it will cool down. Therefore the stove top will be hotter closer to the engine and cooler further away. Pots can be moved up or down the stove top to obtain the right cooking temperature.

Fuel

Fuel can take on many forms: wood chunks, corn cobs, coconut shell, other nut shells, etc. Ideally it should be a waste source making it easy to acquire. If the fuel is cut or wet processed, it should be allowed to air dry. Harvested biomass should be replanted to ensure sustainability. If the biomass is wet, then an integrated biomass dryer will pre-condition the feed before it gets into the gasifier. Using a stratified downdraft gasifier allows the gasifier to be loaded by hand into a hopper mounted above the gasifier.

Community Commitment

Finally, “buy in” by the community is crucial to sustainability. There are many, many projects that have died due to the lack of support or even downright defiance of the community where it is introduced. If however, the community consistently pay for the power and do not vandalise the infrastructure, it will sustain the operator who will make sure that it will run for years. Experience proves that it is essential that the community pay toward the equipment and that they understand that the equipment will be removed in the event that it is not looked after.

There are proven methods available that have had a high degree of success at explaining the principles of sustainability and why it is for everyone's benefit. These involve workshops with the communities to guide them through the process. Members of other communities already enjoying the benefits of power are also included in the process to relate their own experiences. It is important to note that only if the community buys into the process should a unit be supplied. Thereafter, maintenance teams must visit regularly to ensure that the operators are operating the equipment correctly and to maintain and fix broken items and provide spares.

Editor's note: Any questions or queries can be sent to rex@whitfieldfarm.co.za. "Wish us luck," says Rex, who's consultancy firm is due to install its first 12kVA system in Mozambique soon.

[Photo inset: Courtesy of Incog Man]