The Zmart Ztove and the Zip Stove

Here's the place you can post your favorite wood burning stove and also information on how to build and where to get supplies.
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The Zmart Ztove and the Zip Stove

Post by zelph » Sun Oct 24, 2010 2:54 pm

The Zmart Ztove came first and then the Zip stove.


F W Hottenroth

High efficiency low cost, quick start, little smoke, long life
The ZMART ZTOVE is a stove with a very high efficiency rating. The School of Energy of Bharathidasan University in India has carefully tested it in accordance with the percent heat utilised procedure outlined by VITA. The efficiency in bringing 10 kg of water from ambient temperature to boiling measured better than 55% on the average of four tests run on consecutive days. The DNES in India requires an efficiency of only 20% for a stove to be deemed acceptable as an "Improved Stove".

The high efficiency of the ZMART ZTOVE has been achieved by combining high combustion efficiency with careful focusing of most of the generated heat on the surface of the cooking vessel.

High combustion efficiency and a hot fire generally go hand in hand. To assure a hot fire, the ZMART ZTOVE contains the burning fuel within a well insulated cylinder. Air for combustion is preheated so it will not chill the fire and slow down combustion. When the stove is lit, brisk tongues of flame are seen moving almost vertically across the normal upward path of the fire. The high combustion efficiency of the ZMART ZTOVE is evident by the small amount of smoke generated in normal usage.

Focusing of generated heat on the cooking vessel by the ZMART ZTOVE is far from perfect but it is reasonably effective. The fire is contained within a cylinder of good insulating material such as vermiculite of diatomaceous silica, materials which have five times the insulation value of sand. This cylinder effectively limits the amount of heat moving radially out from the fire.

A radiant reflector under the grate stops downward heat loss. Open fires and most stoves waste a considerable amount of their heat energy in heating the ground. The ground under the ZMART ZTOVE remains cool.

Most of the generated heat energy from the wood is directed upward against the bottom of the cooking vessel. According to the tests of Bharathudasan University it took less that 0.5 Kg of wood to boil 10 Kg of water and there was more than 0.1 Kg of charcoal remaining from the initial 0.5 Kg of wood.

Zmart Ztove

The high efficiency of the ZMART ZTOVE has been achieved with a low cost product. It is composed of a few simple parts which can be readily produced using elementary sheet metal equipment. It should be produced under proper supervision to assure good quality. Factory type production is mandatory to provide the quantities needed so every wood- burning family will be equipped with an efficient stove by the turn of the century.

It has been estimated that it can be built in India to sell in India at a retail price which can be paid back out of savings in fuel wood expenditures in six weeks. Similar figures may be anticipated for other countries.

Women who have tried the ZMART ZTOVE like it because it starts so quickly and has such little smoke. It cooks fast and requires little attention. It has been designed to upgrade their status from cooking over a three stone open fire to cooking on a modern stove in a comfortable posture. Most women will want to advance quickly from a single stove to a two burner or three burner stove. The ZMART ZTOVE lends itself to this programme. Additional burners can be added as desired.

The ZMART ZTOVE is designed for long, trouble free life. The housing, legs and pot supports will last indefinitely. The burner bowl should give many months of service in spite of the extremely hot fire within. Life tests indicate that burners operating at maximum output for six month equivalent usage show no serious deterioration. If a burner bowl does burn out after hard usage, it can be simply lifted out and a new, low cost burner bowl put in to take its place.

Z Z Corp is now seeking licensees to make and market ZMART ZTOVES in other countries where wood shortages are causing problems. Z Z can furnish detailed drawings and technical help to licensees plus continuing engineering assistance.

LOS ALAMlTOS, C. A., USA 90720
The above description gives no indications of what type of fuel may be used with the stove - it must clearly be in the form of small pieces. This would not be difficult with fuels such as small charcoal, broken up dung cakes or briquettes but is not likely to be acceptable to people accustomed to using sticks of wood. In the authors description of his original stove design (Zip Stove) he recommended the use of "wood pellets" in the following terms:

"... there is general agreement among the authorities on the subject that small pieces of wood must be used to achieve high efficiency ... From a long term viewpoint it seems to me that in addition to providing efficient stoves, equipment must be provided either at the source or in the home for making the fuel the right size to fit the stove. Also, the fuel must be dried or we immediately waste half its energy. Ideally, wood pellets which are pre- dried may be the long term answer. A wood pelletizer has been set up in India for this purpose. Another possible answer is wood chips. Chippers are low cost and readily transportable. Wood chips dry out quickly ... Even in an open fire, small pieces are more efficient than split logs."

Loose materials such as twigs and stalks may need frequent feeding because of the relatively small combustion chamber. The description does not show a fuel door, so presumably refuelling is done from the top and will cause a temporary reduction in heat output, particularly of radiant heat. Heat transfer to the pan will be limited by the small area of the stove top opening and when used outdoors, the hot gases will not be retained around the stove walls as they are when the pot is sunk into the stove. The stove suffers from the disadvantage of most fuel efficient stoves - they do not give out light like an open fire.

The stove has several good points and if the price is acceptable, it may meet the needs of middle class families who can no longer afford to cook on kerosine or gas. A reliable comparison with a stove such as the improved Kenya Jiko would help to show whether improved efficiency would justify the increase in initial price.

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