Improved Cookstoves

The issue in brief

Since nearly three billion people in the world use traditional stoves to cook their meals, efforts to improve the efficiency of cookstoves have been increasingly popular in the developing world. But it is a hard task to offer improved stoves at an affordable price to households even if they are more fuel efficient.

To prevail over the Three Stone Fire, the Improved Cooking Stove aims to save cooking time (increasing efficiency), as well as, to create a smokeless environment in the kitchen and/or reduce the volume of smoke emission.
Some very interesting cases of improved stoves technology from the 1800 and early 1900 are found in various literature resources. Their relevance is not just historical! These documents bring to new life the experience and inventiveness of people from the recent past where energy was scarce; their solutions are indeed suitable for our present and even more for our future.
Since the 1940s, efforts have been made to increase the efficiency of biomass cookstoves by governments, international development organizations, and NGOs. But improved biomass cookstoves have not reached enough households in rural settings in developing countries where three quarters of the world's 1.2 billion extremely poor people reside. This leaves the rural poor without access to increased efficiency stoves, preventing a reduction in indoor air pollution, greater time spent collecting firewood, as well as the use of dung and crop residues.
In 1947 was reported the first Improved Cooking Stove at Magan Chulha, India (Maithel, 2005). According to FAO (1993), in the early 1950's in India the first phase of Improved Cooking Stove development started with technological attempts to improve the design of biomass-fired stoves. However, the scientific research and development of the Improved Cooking Stove began to proliferate in the 1970s and early 1980s. According to Kammen (1995), the first Improved Cooking Stoves were designed by aid groups such as United Nations Children's Fund (UNICEF) and the Humanitarian Organization Fighting Global Poverty (CARE) in Kenya. Due to lack of field-testing, the designers of those first Improved Cooking Stoves, mainly natives of the U.S. and Europe, obtained weak results. Sometimes, the stove's opening did not match the size of most pots utilized by the users. Even more fundamental problems plagued some of the early prototypes. Designers acted as if it would be an elementary exercise to improve the efficiency of the common metal stove, a deceptively simple can like enclosure into which charcoal or wood is fed and ignited. In fact, after much trial and error, it turned out that an extensive investigation of stove physics and engineering design was needed. This analysis revealed that the largest loss of heat from the fire, about 50 to 70 percent, occurs from radiation and conduction through the metal walls. Makers of some of the first stoves took measures to deliver more of the fire's energy directly to the pot (Kammen, 1995).
Since the late 1970's, attention has been focused on the design and dissemination of simple, low-cost improved cookstoves. Compared to open fires such stoves can save up to 40% of wood fuel and 25-35% of the fuel compared to traditional stoves. Better stove designs gradually came about during the mid-1980s. At that time, a number of academics began to publish serious analyses of optimal stove combustion temperatures and of the insulating properties of the ceramic liner materials. In such a way that the newest designs took into consideration the complex interaction between the different processes that take place in a cookstove, such as: combustion, heat transfer fluid flow and material science. A large number of Improved Cooking Stove models, based on different construction materials, fuel and end- use applications, have been developed during the last 10-15 years.
Improved cookstoves can be designed and built in various ways, depending on the local conditions. According to Foley and Moss, 1983, 'At their simplest, improved stoves rely on providing an enclosure for the fire to cut down on the loss of radiant heat and protect it against the wind. In addition, attention can be given to devising methods of controlling the upward flow of the combustion gases, so as to increase the transfer of heat to the cooking pot'. Many of these stoves are made of mud or sand since both are almost free and readily available.

Advantages Of Improved Stoves

  • Reduced concentrations of smoke and indoor air pollution;
  • Money and time saved in acquiring fuel;
  • Less pressure on forest and energy resources;
  • Reduced greenhouse gases; and
  • Skill development and job creation in the community (Barnes et al, 1993, RWEDP No:44)

Types of Improved Stoves

According to FAO (1993) the Improved Cooking Stoves can be classified into various categories:
  1. Function - Mono-function stoves. An Improved Cooking Stove which performs primarily one function, such as cooking or any other single special function such as fish smoking, baking, roasting, milk simmering, etc. Multi-function stoves. In many areas, apart from cooking, an Improved Cooking Stove can also be used for other purposes or in combination, such as for water heating, room heating, fish/meat smoking, grain/flour roasting, simmering of milk, even to electricity generation.
  2. Construction material - Improved Cooking Stoves are mainly made of single materials: metal, clay, fired-clay or ceramics and bricks or are hybrids in which more than one material is used for different important components. Classification based on the material helps in selecting an appropriate design on the basis of locally available raw materials, skills for fabrication and necessary production facilities (e.g. centralized/decentralized) in the target area. The cost of an Improved Cooking Stove and its expected service life can also be reflected in this classification, including its portability.
  3. Portability - On this basis, an Improved Cooking Stove can be classified as fixed or portable. Metal and ceramic Improved Cooking Stoves are normally portable in nature and can be moved indoors or outdoors while clay/brick, clay/stone Improved Cooking Stoves are generally high mass and thus are fixed. Stoves in this category can be further sub-divided into different categories depending on the number of pot holes, e.g., single, double and triple.
  4. Fuel type - The performance of different Improved Cooking Stoves, having the same function and constructed with the same materials, will ultimately depend on the type of fuel used. In some cases, an Improved Cooking Stove may be rendered practically inoperable when switching over to fuel types for which it was not constructed. For example, an Improved Cooking Stove primarily designed for fuelwood would not perform at all with rice husks or sawdust. Similarly, an efficient charcoal Improved Cooking Stove may perform very poorly with fuelwood or agri-residues. Four major types of Improved Cooking Stoves, based on fuel classification, normally encountered are: charcoal Improved Cooking Stoves, fuelwood Improved Cooking Stoves, granular/loose agri-residue Improved Cooking Stoves, stick-form agri-residue Improved Cooking Stoves, cow dung cake Improved Cooking Stoves, and briquetted biomass-fuel Improved Cooking Stoves.

Characteristics Of ImprovedCookstove

  1. A well proportioned combustion chamber: . If the combustion chamber has a grate, its size determines the fuel burning rate and hence power of the stove. If it is a stove without grate – as in the case of a rocket stove, the diameter of the chamber is important. The height of the combustion chamber may be related to the flame height.
  2. A High thermal efficiency
  3. A High Fuel efficiency
  4. May use processed fuels
  5. High heat transfer ratio
  6. High combustion efficiency- Solid fuel combustion is however much more complex than liquid or gaseous fuel combustion. Due to processes of pyrolysis, the solid fuel combustion takes place in two stages : flaming combustion of volatiles and glowing combustion of char. The variation in this can be very large. Char combustion also depends heavily on the surface area exposed which in turn will depend on the way the bed is laid out, the rate of pyrolysis and the fluid flow through the bed
  7. Low emissions of smoke and other pollutants from the stoves
  8. May or may not have chimney to remove the stove emissions from the kitchen
  9. May have provision for primary and secondary air inlets for combustion
  10. May have provision for forced draft of air
  11. Stove body made of durable material like well baked clay, ceramic or metal- Materials are an extremely important part of any stove. The high temperature environment to which the combustion chamber is exposed is highly corrosive and hence can severely affect the life of the combustion chamber lining. The desirable features of material for improved stove are:
  • Durability in high temperature environment
  • Low cost
  • Local availability
  • Easy manufacturability
  1. Desirable thermo-physical properties for improved stoves like low density, low specific heat and low conductivity to reduce transient as well as steady state energy losses from the combustion chamber.
  2. Safe to handle and use.
Table 1: Types of ImprovedStoves
''NameFunctionConstruction materialPortabilityFuel type
Image Improved three stone or mud-stoveMono-functionClay, straw, dung, cement, stoneFixedWood
Image Multi-fuelMono-functionMetalPortableWood, charcoal, dung, agriculture residues
Image Multi-cookerMono-functionMetalPortableWood
Image Mono-cookerMono-functionMetalPortableCharcoal
Image Mono-cookerMono-functionMetal and ceramicPortableCharcoal

A mud stove is usually a stable device that can have one or more pot hole. Generally a fixed improved cook stove requires adequate pre-and post installation education and training for the user on auto-building, proper use and maintenance. Local clay, straw, dung, cement and stone are the main materials used in the construction of a stable device cooking. The mud-stove can be sized to fit the family’s own pot(s).

Portable stoves are characterized by one pot hole and are more widely used than fixed stoves.
A multi-fuel improved stove is usually characterized by a mobile grate which allows the use of a variety of available fuel (wood, charcoal, dung, agriculture residues).
A multi-cooker improved stove matches a range of user’s pot size.

Current Best Practice

The thermo electric generator stoves can be used to - cook food, heat the room and generate electricity. These stoves, named as UJELI stoves (meaning light in Nepali language, were developed in Engines and Energy Conversion Laboratory of Colorado State University and the project was implemented in Nepal through STARIC/N (Sustainable Technology Adaptive Research and Implementation Center/Nepal ). Ujeli Chulo is now being field tested in Gatlang Village in Nepal. This wood-burning stove consumes wood in a far less quantity than the traditional open fires.
The Philips wood stove developed by Philips runs on a thermoelectric generator using the heat from the burning wood to generate electricity for the fan. The fan forces the air through the stove, leading to higher temperatures and a better fuel to air ratio. This results in cleaner burning and more efficient use of fuel.
The rocket combustion chamber is designed so as to achieve almost complete combustion of wood thus increasing the efficiency and decreasing indoor air pollution particularly the particulates and carbon monoxide. The stove also has a chimney stack that removes the exhaust outside the room thus making the room free of any smoke. The most novel feature of this stove is that it also generates electricity that powers the bright CCFL lights. 3-4 hours of cooking everyday provides light for 2-3 hours at night or daytime. Furthermore, the stove also radiates heat which warms the room (Shrestha, HEDON).

Self-built or Factory-built?

Initially there was a tradition of owner-building of stoves but experienced observers are concluded that the small industry production of stoves is one of the most promising routes to take.

The advantages of this approach include:
  • Better quality control and therefore
  • Higher efficiency and
  • Longer stove life than can be achieved with owner-building.
Costing $1-5 each, the stoves can often pay for themselves in fuel savings within 1-2 months if the fuel is purchased. In rural areas where most fuel is gathered, very low-cost stoves can still be sold to some people.

Areas of Research

  1. Economics of fuel, stove types and access conditions to fuels,
  2. Technical characteristics of cookstoves and cooking practices;
  3. Indoor air pollution effects;
  4. How cultural preferences and practices can obstruct activities;
  5. Capacity building in customized methodologies;
  6. How to respect the local knowledge;
  7. Social studies in willingness to accept changes especially when cost is involved;
  8. How to document adaptation to Improved Cooking Stove;
  9. How to show vividly the improvements reached using Improved Cooking Stove;
  10. Utilization of Improved Cookstove

Effects on Fuel Conservation

Fuel conservation through improved cookstoves appears to be the cheapest way for a nation to invest in new sources of energy. The typical artisan-produced cookstove conserving 35% of fuelwood costs less than $5.
The secondary effects of existing cooking systems must be understood before acceptable improvements can be made. In many places, smoke from indoor cooking fires is a significant contributor to lung and eye disease. Yet this smoke also serves to dry crops hung over the cooking area and to protect thatched roofs from insect damage. In highland regions and other colder areas, the space heating function of the indoor cooking fire may need to be included in cookstove design. Successful stove promotion efforts may depend on the availability of effective alterations for these secondary functions of the cooking fire.
A 35% savings in fuel is considered a realistic figure for the better stove designs. Similarly, most agree that the distribution of improved stoves alone is not going to greatly affect the rate of deforestation in most places.

Nevertheless, improved cookstoves are now considered to be a cost-effective component in reforestation programmes in some countries, and clearly they have a role to play in improving the quality of life by conserving family resources of cash and time, and reducing smoke in the cooking area.

Improved stoves attain high efficiency by:
  • complete combustion of fuel
  • maximum transfer of heat of combustion from the flame to the cooking pots.
  • minimum loss of heat to the surroundings.
This is achieved by incorporating all or some of the following components mentioned below.

The improved chulha used in India has
  • Sliding firebox door
  • Inlet
  • Grate
  • Baffles
  • Dampers
  • Chimney dampers to control air supply
  • Cowl - a metal cap attached to the chimney
The increasing acceptance of the improved stove shows that stove programmes have positive impacts on users,
  • Saving cooking time and fuel, and providing hot water cheaply.
  • Saving cooking time means more free time and less fatigue, both of which have a direct impact on the time available for childcare and for improving the quality of kitchen environment.
  • The demand from other households in the villages indicates that the technology has been well received.

In some parts of the world, notably China, and to some extent India, significant progress has been made in the dissemination of improved cookstoves, with numbers of improved stoves in use numbering in the millions. In Africa, only Kenya claims a stove dissemination level that exceeds a million. The difficulty of disseminating improved stoves in Africa is the subject of a separate article.

Barriers to Improved Cookstove Adoption

Despite the efforts to disseminate improved cookstoves in the developing world, such programs have struggled to make an impact. The new cookstove entrepreneurs in recent years have developed innovative strategies to scale-up cookstove adoption. Probably, if new cookstove business models (whether purely for-profit or not) are to be successful, they must take into account a critical and often-overlooked fact: not all “bottom of the pyramid products” are created equal. Some are very readily adopted by the poor—examples include Coca-Cola, TVs, and malaria nets. Other products, like cookstoves, present many more obstacles that must be overcome for successful dissemination.
Xander Slaski and Mark Thurber from the Program on Energy and Sustainable Development, Stanford University in the GTZ publication 'Cookstoves and Markets:Experiences, Successes and opportunities' suggest that there are three principal dimensions affecting adoption of any radically new product or service by the poor: motivation, affordability, and the level of engagement required.


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Last edited by Karabi Dutta .
Page last modified on Tuesday December 28, 2010 10:25:20 GMT.
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