Measuring Cookstove Efficiency
Efficiency is a measure of how much fuel is used by a device to achieve a desired outcome. Efficiency is of interest to development organisations, technical developers, and the end-users because it is an indicator of the operation cost (for fuels that are purchased), and resource impact (deforestation from the use of wood). For an improved cookstove or an open fire, knowledge of a stove's efficiency can also give an indication of related benefits such as the time needed to collect fuel.
Three simple test methods are commonly used by development organisations. Since these methods depend on uncontrolled factors they do not give absolute results. Instead comparisons are made between the normal stove and the improved stove (for example). This eliminates the need for the measurement of precise thermodynamic parameters. The tests can be carried out with locally available equipment by lay people and can yield useful stove efficiency. The tests are:
- The Water Boiling Test - this is a 'laboratory' test, most commonly used during the design phase of a stove development programme to investigate the effect of design changes on stove performance while it is used to boil and simmer a pot of water. Since this test is carried out under controlled conditions it is least accurate in predicting how the stove will perform in the field.
- The Controlled Cooking Test- in the controlled cooking test the stove is used by a rural cook to prepare a simple meal (appropriate for where the stoves will be used), and the quantity of fuel used is measured. Since fuel consumption is measured while the stove is used to prepare a real meal, this test gives a better indication of fuel consumption when used in the household.
- The Field Trial - field trials are used to measure the impact of an improved stove in use. It depends on measuring the impact on household fuels over an extended period in a number of households (VITA, 1985, Testing the Efficiency of Wood-burning Cookstoves: International Standards, Volunteers in Technical Assistance, Virginia USA)
cookstove.net on fuel economy