Diesel
Practical Action
Uses and power requirements
As mentioned earlier there is an almost limitless range of applications for the diesel or petrol
engine. Some typical rural applications and their power requirements are shown below:
Application
Small scale irrigation pumps
Small scale electricity generation
Battery charging
Grain milling or threshing
Typical power requirement
2 - 15 kW
2 - 50 kW
500 W
5 - 15 kW
Diesel generator sets
Due to their widespread use throughout the world, diesel generator sets deserve a further
mention. Diesel generating sets come in a wide range of commercially available sizes, from about
5 kW up to 30 MW (30,000 kW).
They are long lasting and will usually have a useful lifespan of 7 -10 years (30,000 hours
running time), but this can be drastically reduced if maintenance is poor.
They are used by individuals, electricity utilities and businesses and are often used to supply a
small electrical grid in remote areas where the national grid has not yet reached. They are usually
fitted with a governor which automatically controls the speed of the machine as the load varies,
maintaining constant voltage and frequency. Efficiency depends on the loading of the machine
and where the load pattern (pattern of electricity consumption throughout the day) requires, two
or more smaller machines are used to achieve higher fuel efficiency. Diesel generator sets, being
somewhat noisy, are usually sited in a separate power house away from the premises or outside
the town (depending upon their application).
Petrol generator sets come in smaller sizes - from 500W up to several kW - and tend to have a
much shorter lifespan (5000 hours running time) than their diesel counterparts. They are more
suited to mobile, very small scale electricity needs.
Alternative fuels
Diesel is often too expensive for households to buy. Diesel engines adapted to burn vegetable oil
are being tested in demonstration units in isolated villages.
There are several types of vegetable oils that can be used to
generate electricity in adapted diesel engines.
Ethanol and methanol (also known as alcohols)
substitute directly for petrol (gasoline), and vegetable
oils can substitute directly for diesel fuels.
Ethanol is already used commercially as an engine fuel
in Brazil and, when blended with petrol to form the
blend known as gasohol, in a number of other countries.
There is a lot of work in Brazil developing their bio-diesel
capacity in which they are attempting to include poorer small
scale farmers in the North of the country rather than aiming for
large scale commercial operations that, often exclude smaller
farmers.
In another project in South Africa they are testing the impact of
the hydrology of growing Jatropha trees for oil production.
Figure 3: Making biodiesel in Peru.
Photo: Soluciones Prácticas.
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