The Testing Of Gel Fuels, And Their Comparison To Alternative Cooking Fuels

A range of gel fuels was tested in a range of appliances designed for the fuels. The tests comprised the determination of the efficiency of the fuel/appliance combination when boiling water at full and, where possible, minimum power; and the measurement of CO, CO2 and unburned hydrocarbons collected in a hood at the burner level in normal operation. The tests were repeated with paraffin-fuelled appliances, LP gas appliances and an electric stove. In the majority of cases it was found that the gel fuels did not meet an emission standard of a CO:CO2 ratio of <0.02, and that they gave off excessive unburned hydrocarbons. It was suspected that this had to do with the mixing of the fuel vapour with air, because tests with pure ethanol in various appliances gave similar results. Tests in which appliances were modified to improve the air/fuel mixing showed that the hypothesis was valid. A subsidiary finding of the tests was that some gel fuels had excessive water, and that in these cases the condensation of the water vapour on the base of a cooking pot was so extensive that it could extinguish the flame. This leads to a recommendation that a standard for gel fuels be established. A comparison of the cost of cooking a standard meal suggests that gel fuels are unlikely to meet users needs even if improved appliances can be developed.

Gel fuels have excited a lot of interest as possible alternatives to paraffin or LP gas as fuels for cooking. This is largely because the most popular fuel, paraffin, has been shown to present considerable hazards when used in typical, readily available cookers. Our studies [1] have shown that, in use, the paraffin in the fuel tank of the wick-type of stove becomes heated to above its flash point. When that happens, the fuel can conflagrate at a rate sufficient to raise the temperature in a typical lowincome home to over 400 deg C within 30 seconds. About 100 000 homes are destroyed this way every year. The Department of Minerals & Energy convened a workshop in late 2004 into the use of gel fuels, and has since encouraged the introduction of these fuels [2]. The gel fuel does not spill readily, and can be made from renewable resources, so may well be an improvement over the widely used paraffin. However, there have been no rigorous comparisons of the various fuels. This paper aims to make good that lack.

EXPERIMENTAL
A wide range of fuels was acquired from retail sources. Most of those tested are shown in Figure 1.

Figure 1 Samples of most of the fuels tested.
The calorific values of several typical gel fuels was
determined by a certified analytical laboratory.

The calorific values of several typical gel fuels was determined by a certified analytical laboratory.

The market was scoured for examples of stoves designed to use either ethanol or ethanol gels. Few were branded, and many were designed to burn at a single heat level. Details of these appliances can be provided on request.

Tests comprised boiling about 1.5l water and determining the time to heat from 20 deg C to boiling; determining the rate of evaporating water and the rate of consumption of fuel while boiling at various heating levels to derive the efficiency of the fuel/stove combination; collecting the combustion products in a hood and analysing them with a combustion analyser to find the CO:CO2 ratio and level of unburned hydrocarbons. The cooking tests involved boiling 1l water, adding 600g of maize meal, boiling for 5 minutes and simmering for 30 minutes, to find the fuel used.

Click here to download PDF for more information

• No black pots
• No bad smells
• Safer for the environment
• Safer for your family
• Up to 8 hours of cooking p/litre

"For the best cooking experience"