Heating-cum-cooking stoves of the FECT Project, Peshawar, Pakistan

Tanveer Ahmad and Sohail Nazir Women Educational and Environmental Network (WEEN) PO Box 25 Abbottabad NWFP Pakistan

Heating-cum-cooking devices have been widely in use in the colder regions of the North West Frontier Province (NWFP) of Pakistan for the past decade. These devices were introduced mainly by the metal workers of an area called Gujar Gari. The main reason for their wide acceptability was that they conformed to the way of life of the people and soon became a basic component of the household.

Development of heating devices was started in Kalam in collaboration with the Pak-Swiss project called KIDP in the beginning of 1990. During this phase a number of devices were designed and tested extensively. The research and development in this phase started with the modification of traditional heating devices by improving combustion chambers along with other minor changes. A number of new designs were developed and tested at the Kacha Gari research and development centre in Peshawar. Emphasis was placed on reduction of both fuel consumption and smoke emission and the design of a product which was user friendly at an acceptable price.

Figure 1: Rounded heating stove for communities living in less cold mountain regions.

Based on the basic needs of the targeted population, work on two different heating stove models was initiated; a smaller rounded heating stove for the target group living in relatively low and less cold mountain areas (Figure 1), and a bigger rectangular stove which was aimed at the population living in high mountain areas, who experience harsh winter conditions with temperatures below freezing point for most of the winter. Both these models were field-tested and modified where this was needed.

The latest stove models

The main shortcomings in the improved models included:

· The cleaning of the improved model was reported to be difficult due to its complicated shape
· The stove was seen as too expensive compared to the traditional stoves in the local market

During the field testing, one point became very clear i.e. there was a need to develop different sues and shapes in the heating stoves for different altitudes and ethnic groups within the Swat and Kalam Valleys.

Testing Procedure used at FECT

Different methods were applied to get detailed information about the most important aspects of heating stoves. These aspects included:

· Cooking capacity
· Heating capacity
· Fuel consumption
· Maintenance of fire
· Smoke leakage

Three different approaches were applied to the improved stove models as well as their traditional counterparts. All the tests were carried out in a well-insulated test room, especially designed for the purpose, so that simulation of reality could be combined with standardized test conditions. The fuel wood used in the tests was brought from the area for which the stove was to be developed.

The three different test methods used during tests were:

One hour test

In this method, the stove is operated at very high power rate for twenty minutes. For the remaining forty minutes, operation continues at low power under such conditions that the temperature reached during high power phase does not drop. Temperature and composition of the gases in chimney was measured every fifteen minutes. The amount of wood used during the test is recorded and the whole process is carefully observed.

Five kilogramme test

This test method was used to obtain additional information about the relation between fuel consumption, heating capacity and time. The test was carried out to find out the time taken by each stove to consume 5Kg wood. The test method was same as the 1 Kg test except that the 5Kg test was continued until all the wood was finished

Eight hour test

In this test, after 20 minutes of a high power phase, the operation was continued at low power, maintaining the temperature reached during high power phase throughout the test period of eight hours.

After four hours operation, the carbon monoxide content of the air was measured where the person cooking would be located. This was done for one hour using carbon monoxide measuring tubes.

Every 15 minutes, temperatures at four different points of the stove body were measured. These points were:

· Top of stove (over the pothole lid)
· At the side of the wall
· Under the combustion chamber
· Outside of the chimney pipe

The eight hour test, according to our experience, gives a lot of useful information concerning fuel consumption, ease of operation, maintenance of fire, heating capacity and smoke emission etc.

Comments on results

The main conclusions reached using laboratory tests were as follows:

Heating capacity of stoves

It can be clearly seen from the test results that the heating capacity of the improved stoves was far greater than their traditional counterparts

Wood saving

The baffle in the improved stove models is one of the major factors reducing wood consumption. With the baffle, the speed of flue gases leaving the chimney is slowed down and it makes the size of the combustion chamber smaller so that the operator can only feed a small amount of wood. Another factor is the sliding mechanism of the door which helps to retain the heat, whereas the door of the traditional heating stove is left open when the fire is burning. The door of the improved heating stove comes down to just the size of wood fed into the stove. This factor also helps in saving wood (see result of eight hours with open and closed door)

Comparing the results of eight hours test, the wood saving in both the box-shape improved and the round-shape improved stove is around 25 per cent as compared to their traditional models.

Cooking efficiency

The heat is concentrated directly under the pot due to the baffle, so the cooking time of the improved heating stove is shorter and efficiency (PHU) is higher. The improved box shape models give a big difference in PHI,. In traditional stoves, the big pots sit on the pot supports, so there remains a 2cm gap between the pot and the stove which causes the decrease in its cooking efficiency.

Compared to traditional models, the efficiency of the improved box shape heating stove, using big pots is raised by 77 per cent while cooking time is reduced by 52 per cent. For the smaller round stove models, the differences are greater. With small pot sizes, the flames are more concentrated under the pot and the pot hole is completely covered by the pot.

Smoke/carbon monoxide

Laboratory test results show that with the improved models, smoke is very much reduced compared to the traditional models.

Durability of the stove

The improved heating stove models being of thick metal sheet (22 gauge) are more durable than the traditional models (28 gauge). Also the chances of the pot hole becoming distorted are reduced as a metal rod is rolled in its rim.

Operation of stoves

One advantage noted whilst testing the stoves was their operating characteristics at low power. With traditional stoves it is really hard to operate them at low power; the stoves need constant attention and very careful feeding of wood pieces whereas with improved stoves, the operation at low power is very easy.

In improved stoves. the speed of the hot gases is reduced by the baffle, so maximum heat by the exhaust gases is given out to the stove body before they leave through the chimney. In the improved models, a large amount of charcoal is accumulated in the combustion chamber, which keeps the stove body hot, thus reducing the wood feeding and attention of the operator.