I previously wrote about Stirling engines and I thought I would write more about them.

Stirling engines have at least two cylinders – a ‘cold’ cylinder and a ‘hot’ cylinder. In each cylinder is a piston that can move from the bottom to the top of the cylinder. The pistons have con rods which drive a shaft. The shaft is cranked so that, when one piston is almost at the top of its stroke, the other is at the bottom.

The cylinders are linked with a pipe. When the hot cylinder is heated, the air in the cylinder expands and displaces the piston. A flywheel causes the piston to reverse-stroke and the hot gas moves to the cool cylinder, where the gas cools and returns by the cold piston back to the hot cylinder.

But, really, all you need to know is, if you make a fire at one end, you have an engine that produces rotary motion of a shaft that can be used to pump water, drive a generator, and so on (look it up on the Internet if you want to). Some people think that you could just put the hot part of the engine in the sun and it will produce power – it will, but it will not be much.

However, the Stirling engine, thus far not much more than a toy, has the potential to change the face of power generation in Africa. There is a widespread opinion that all the wood in Africa is nearly exhausted, but this, in my experience, is not the case. There is a long-exist- ing charcoal industry in Africa and it would be very simple to make charcoal-fired Stirling engines that burn charcoal. Charcoal has a calorific value of about 19 MJ/kg; so, a 2 kW Stirling engine could easily run for four hours at full load on 5 kg of charcoal. The beauty of the Stirling engine is that it really just runs on a heat source and nothing else. It is, thus, very robust (oh, I guess you would have to grease the system from time to time).

I have been travelling around Africa for about 40 years and the greatest single need that I see is for electricity – for lighting, to begin with, and then for TV and refrigeration, and so on. All over the continent, there are small diesel electricity generators and in some cases electricity grid connections.

All these require a financial model to operate – very frequently a model that is just not available in Africa. Nowhere is there a system like a Stirling engine system, which allows people to make electricity from wood they collect or charcoal they could make. Yet it seems obvious to me that this should happen.

African countries are very poor. Very, very poor. It seems to me that this is ignored or not understood by many organisations or governments. It would be so simple to manufacture some Stirling engine generators and distribute them to villages so that the inhabitants have some form of electricity.

This does not even happen with that most accessible, safe and reliable form of power, photovoltaic cells, so I guess one cannot expect further sophistication in this regard. But it does depress me. There are organisations such as the Rockefeller Foundation, the Gates Foundation, and so on, which could donate, as a one-off donation, some means of providing poor Africans with electricity, noting that African governments, with few exceptions, are doing nothing about this, owing to the massive self- interest and corruption that pervade them.

South African government departments give grants to organisations that are staffed with inexperienced students trying to develop technologies which are really not needed (but which allows them to get an MSc), when they could pay a reasonably competent manufacturer to make Stirling engines and similar items that could be used by rural people to provide power for themselves. (There is a good example of this – the solar jar light, which is very useful and widespread, was developed by Consul and Suntoy. Why did government not develop it?) But watch this space. Somebody may wake up yet.