DESI Power

Fuel mix in rural India is characterised by the predominance of biofuels. Among these, fuel wood accounts for over 50% of our energy consumption (NCAER, 1985). Dung cakes constitute the other major source of rural energy - about 60% of dung collected in the country is burnt as fuel. Continued reliance on these sources is, one the one hand, depleting the natural resource base and, on the other, preventing growth of the rural productive sector, especially industries.

This national scenario repeats itself in much of the Bundelkhand region, including Jhansi district. The extent of deforestation in the district is reflected in the low forest cover of 6.5% (NWDB, 1993) - much of it caused by pressure of fuel wood. Agriculture, the main occupation in the district, relies on one crop and shows large scale seasonal unemployment. The productivity of land has been steadily declining due to loss of soil nutrients and this is reflected in the high proportion of wastelands in the district - 18% of the geographical area (NWDB, 1993) which is one of the highest in Uttar Pradesh. The loss of nutrients is being compounded by diversion of cow dung away from the fields. The current crisis of rural energy is affecting a number of user groups: domestic households, artisans like potters, industries and the urban informal sector. The several manifestations of the rural energy crisis in Jhansi are:

DESI Power has been launched as a major initiative in identifying the possible sources of renewable materials which can be effectively used in the decentralised production of electricity. The two major classes of raw materials identified are animal residues like cow dung and biomass materials such as lantana, ipomea, and mustard stalk. Further, it is proposed to integrally link energy technologies with livelihood-based enterprises. Fig. 1 demonstrates the linkages between energy technologies and livelihoods. The major technologies that have been selected are:

A biomass-based gasifier has a reactor which acts as a gas reactor and is coupled to a cooling and cleaning train. The reactor has two sections. The bottom portion consists of a mild steel shell lined with ceramic material 60mm thick. The top portion is a double wall with stainless steel shell. The bottom shell has air nozzles and is used for ignition and for monitoring the combustion zone. A water seal isolates the bottom portion of the reactor.

The gases released during pyrolysis combust in the combustion zone at about 1200-1400oC. The products of combustion move through the charged zone where they get reduced to carbon monoxide and hydrogen gas. This gas is used as feedstock for thermal applications and for mixed feed into diesel generating sets. The cleaning train is used to scrub the gas for removal of tar and dust particles. The first commercial biomass gasifier unit initiated by DESI Power has been commissioned at TARAgram, Orchha, Madhya Pradesh. The details are given in box 1.

In the absence of fuel wood, cow dung is used for cooking, burning of bricks and majority of thermal applications. The wastelands and water streams of Bundelkhand are inundated with growth of lantana and ipomea respectively. These biomass species are not hitherto used for domestic cooking or for burning as these are reported to emit toxic fumes during the initial combustion. Using simple means of pyrolysis, these materials can be very effectively converted to char. This process gives an effective yield of 20-25% based on dry biomass, i.e. 4-5 tonnes of biomass provides 1 tonne of char.

This char is powdered, blended with appropriate binders and extruded to manufacture briquettes. In the case of Jhansi, the additives are clay (upto 20%), cowdung (upto 5%), and cellulosic waste from handmade paper production (upto 10%). Different combinations of additives are added to control the speed of combination, heat content and sparking characteristics of the briquetted fuel.

For this purpose, a briquette machine has been designed with a productivity of 1 tonne of briquettes per day which is powered with a 5HP motor. The briquette has an outer diameter of 50mm, a central hole of 10mm and length to suit the application. The cost economics of briquettes manufactured is given as under:

Market survey has shown that good marketing potential exists for sale of the briquettes at a selling price of Rs.4,000/- to Rs.4,500/- per tonne. Besides charcoal briquettes, the machine can also be used for briquetting of powdery biomass materials such as mustard stalk, sunnhemp and groundnut shells. To ensure sustainability, it has been observed that every village having access to a water stream can collect upto 500 tons of biomass from a radius of 2.5 kms on a renewable basis. This material is converted to efficient fuel through livelihoods.

Within the regional context, DESI Power has examined the market potential for synergy systems which provide multiple uses for a given resource. The technologies identified are:

The Bundelkhand region has a cattle: human population ratio of 1.1:1. Milk production is a major livelihood but very little of the cow dung is used as manure. Biogas plants are not widely used in this area even though the technical feasibility and need appears to be very high.

Amongst large number of families surveyed on the Jhansi - Babina road, house owners with cattle holding in excess of six who also have land for agriculture are very keen to install biogas plants of 2cu.m capacity or even higher capacity. The biogas would be used for cooking and the slurry would be composted to be used as fertiliser.

The Bundelkhand region has land terrain which is very conducive for harvesting of water through check dams. In most cases, a head of three metres is possible. A local inventor has set up a prototype of water wheel with turbine system for direct pumping of water. This technology has a potential of being adapted for generation of electricity and efficient pumping for irrigation. The techno economic feasibility of this package is very favourable for establishing integrated energy and water services in the area and even extending this to fish cultivation. DESI Power plans to implement a prototype unit for determining a long term marketing strategy. q

First Commercial Biomass Gasifier Unit Commissioned
at TARAgram, Orchha, Madhya Pradesh

The first commercial biomass-based gasifier unit for production of electric power has been commissioned at TARAgram, Orchha. The unit is the prime venture of DESI Power, a joint venture of TARA, New Delhi and DASAG, India. The equipment has been supplied by NETPRO, Bangalore based on the design of Indian Institute of Sciences.

The rating of the gasifier is 100 kW which is coupled to two diesel generating sets of 62.5 KVA rating. The first DG set has been commissioned and linked to the gasifier which uses Ipomea as biomass feedstock. The breakthrough in technology development has been to produce gas of consistent quality with low tar content and dust levels. This has been achieved by a downdraught gasifier operating with open top configuration with air intake from the top as well as side air nozzles located at about one third of the reactor height.

The climatic conditions in Orchha have necessitated cooling of the recirculating water in order to keep the gas temperature within temperature of 40 °C. The cooling water after scrubbing, is passed through a charcoal filter which drains into a sump holding 6cu.m of water. Through a recirculating pump, this water is sprayed using specially designed nozzles on to a form work of wood which serves as a cooling tower giving cooling effect up to 15 °C during the peak of summer. It has been possible to maintain a gas temperature 35± 3°C during the first two months of operation.

In order to control the feedstock material, it is important to size the material uniformly. The biomass collection is done by households in nearby villages and cut approximately to size using conventional fodder cutting machines. A new biomass cutter using multi-start cam arrangement has been devised to size the material accurately and to increase productivity. It is now possible to size the material between 50-60 mm which is fed directly into the gasifier.

With these innovations, the performance of the gasifier cum diesel generating system has been monitored during first 500 hours of operation. Under dry conditions and for steady loads upto 46 kW from a single generator of 62.5 KVA rating, it has been possible to consistently obtain diesel replacement rate of 85% and higher. However, under normal conditions of fluctuating load and varying demand, the average diesel replacement rate over a variety of operating conditions has been consistently in excess of 80%. This performance has been obtained while keeping all other operating parameters under check. Higher diesel replacement is possible by improved load management practices.

The direct cost of production of electricity taking into account fuel cost and operating cost is expected to be approx. Rs.2.00 per kWh once full load conditions are established.

by Rajiv Gupta

Note: Industrial clients, community development agencies,
State and Central government departments and voluntary organisations can acquire these
technologies from General Manager, DESI Power, C/o Development Alternatives.