Improved Cookstoves and Energy Saving Cooking Equipment
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What is a stove?
Commonly the term ‘stove’ refers to a device that generates heat from an energy carrier and makes that heat available for the intended use in a specific application. Cook stoves are made to transfer the generated heat into food, with the purpose to get it cooked and edible for the human consumption. Thus ‘a stove’ always features the combination of heat generation and heat transfer into a cooking pot if the food is cooked in a liquid, or agriddle, plancha etc. if the food is baked on a hot surface or roasted without liquid.
What is an efficient stove?
Cook stoves are commonly called “improved” if they are more “efficient” as the traditional cook stoves. But what does “efficient” mean in this case?
The actual energy efficiency describes the heat transferred into the pot in relation to the overall energy generated in the stove within a defined task (e.g. water boiling test). For more details on stove testing see here.
But in most cases, this is not what is meant when the efficiency of stoves is discussed. From the perspective of a stove user, the core question concerning the efficiency of two alternative stoves is:
“With which of the two stoves do I use less fuel to prepare my meal?”
To answer this question, the perspective of energy efficiency is too narrow as a number of factors beyond the stove design take influence:
- the quality and characteristics of the fuel,
- the handling of the fuel,
- the handling of the stove,
- the management of the cooking process
- the environment of cooking…
In this broader sense it is a cooking system that has to be analysed to determine which stove has a higher “user efficiency”.
When we talk about the efficiency of stoves, we usually mean the comparison of the specific fuel consumption of a specific energy use in comparison to either (a) a benchmark or (b) the specific consumption of another stove.
Examples:
- (a) Stove A consumes less fuel (for a specific standardised task) as indicated in the benchmark (e.g. 80g of charcoal per kg food prepared in a controlled cooking test);
- (b) Stove A consumes 40% less fuel than stove B per litre boiled water (in a 5l Water boiling test);
With focus on relative performances of stoves, the assessment of stove efficiency is circumstantial. A clay stove is perceived as an efficient stove in households with open fire places and as an inefficient stove in households which are using a rocket stove.
International standards on stove quality have been discussed for many years. While they are desirable to enable a global comparison of stove performances, there is a danger that cheap solutions for the very poor households are abandoned due to their low performance in relation to the global standards, when in fact they could still be a relevant improvement in comparison to the baseline situation of the poorest of the poor. That’s why a stratification of quality standards has been developed in the Lima consensus.
Global stove diversity
There are many different types of stoves on this planet. This is natural, as a stove needs to accommodate the site-specific constellation determined by the available fuels, climatic conditions and preferences of users in the local culture. Thus stove designs reflect global diversity. Please keep in mind: ‘One size fits some, but rarely all’.
The resulting diversity of stoves can be described in different categories like
- Fuel types (solid, liquid or gaseous fuels from renewable biomass or fossil sources)
- Pot sizes (from small to big individual households sizes, medium to large pots for restaurants, enterprises or social institutions)
- Pot shapes and materials (round bottom/flat bottom pots, clay or metal, pots with or without handles and/or legs, frying pans, etc.)
- Numbers of pots to be used at a time (pot holes for one or several saucepans)
- Numbers of fires (one fire-box or several fires)
- Batch-feeding or continuous feed of fuel
- Natural draft or forced convection with a ventilator
- With or without a built-in chimney to remove emissions from a kitchen
- Transportability (from built-in models that have to be constructed on site to portable stoves built elsewhere)
- Affordability (to suit the range of economic means of users from low-cost to more expensive)
- Place of manufacture (national production or imported)
- Cost (mainly determined by the type of building material and the level of sophistication of a stove)
- Other uses of a stove e.g. space heating, lighting
Stove designs also depend on the cooking habits. For instance, in many Latin American countries tortillas are a traditional staple food baked on a hot metal plate ('plancha'). In Ethiopia the staple food is a pancake baked on a large ceramic plate. Any stove needs to incorporate those features that are essential for people to prepare their staple foods. Otherwise the stove will not be acceptable in that area.
Beatrix Westhoff and Dorsi German compiled a comprehensive overview on global stove diversity in 1995 in the publication 'Stove Images - a Documentation of Improved and Traditional Stoves in Africa, Asia and Latin America'. It is available in English, French and Spanish on
Not all stove types comply with criteria required to qualify as 'improved stoves'.
Promising stove types that are performing well within the GIZ-supported project areas are presented in the Stove Fact Sheets published by GIZ HERA.
The following chapters present stove types for different fuels and cooking practices according to the following structure:
Household cooking energy diversity
Commonly household cooking energy is discussed as a “one fuel - one stove” system. The archetype of this idea is the rural household using firewood in a 3-stone fireplace. On a second look, this picture is often a drastic simplification of the reality. Many households, particularly in (peri-) urban environments, are actually using several fuels and/or several stoves for a variety of reasons:
- Different traditional meals require different types of heat (e.g. Ethiopia: the large pancake-style injera, sauce, and coffee ceremony);
- Seasonal variation of availability or affordability of fuels (e.g. biomass as back-up if fossil fuels or electricity is not available, increasing prices or money shortages at the end of the month);
- Variation of convenience needs (e.g. fast cooking in the morning, slow cooking in the evening);
- Different abilities of cooks (e.g. expensive fuels and stoves shall not be used by the young daughter, so she is using firewood);
- Different cooking needs (e.g. preparation of meals for the family on a different stove as the preparation of animal feed or processed food for the market);
- Different types, shapes and sizes of cooking utensils (cooking pots, pans etc.) require different stove shapes or sizes.
Cooking energy interventions should be based on a clear understanding of the household cooking energy diversity of their target groups before activities are planned. It must be clear which part of the “traditional” (= baseline) cooking system shall be addressed.
Fuel switching and the “energy ladder”
A favoured development model for household energy is described with the term “energy ladder”. The basic idea is that with increasing wealth, households are ‘progressing’ from stickwood to charcoal, kerosene, LPG and finally to electricity. Each step on the ladder is linked to a fuel switch which implies in this model the permanent and complete change from the use of “traditional” fuels to more “modern” fuels.
As indicated above, the introduction of “modern” alternatives often rather contributes to an enlargement of the complexity of parallel utilised cooking systems (the “cooking energy mix”) rather than a complete fuel switch in the sense of climbing a ladder.
In recent years, more and more observations have been made that users of “modern energy” like electricity or LPG are “going down the ladder” if a removal of subsidies increases the cost of cooking and/or the availability of the fuel. Hence the picture of “switching the fuel” is in many cases rather a matter of “increasing the diversity of options” than a permanent change of behaviour.
Generally it is easier to convince households to increase the efficiency of use of their traditional fuel(s) rather than to learn how to use a new fuel. It is also easier only to deal with the establishment of a supply-demand system for a stove rather than establishing a new fuel supply system as well. Fuel is needed on a daily basis; a stove needs to be replaced only once in a while. It sounds plausible that urban and better educated households are more open to innovations as compared to rural households with less education.
However, this is a decision by the target group which can be surprisingly different than our assumptions. In a field test of a plant oil stove in Tanzania, even rural firewood using households have managed to operate a plant oil stove successfully.
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