One of the main impediments in large scale use of renewable energy sources is the non availability of inexpensive, reliable, simple, locally maintainable and efficient technologies for energy conversion. Many activities are in progress for developing acceptable technologies in the State. Some of them are listed below.

Biogas Plants:

Cowdung based gobar gas plants were introduced in 50's and their growth rate is very slow. Biogas plants have many advantages the Nitrogen content in the slurry of a biogas plant/kg of dung put in is three times the Nitrogen got per kg. of dung by normal composting practices; the 60-70% methane gas is a useful by product which can be used to meet the rural energy requirements for cooking, lighting, water lifting, transportation etc; because of a closed system, hygiene in the surrounding areas improves considerably - there will be lesser number of flies in the neighbourhood; the waste water is a good source to produce algae like azoles or BGA a good nutrient for paddy; installation of a decentralised source of Energy, might create infrastructure for local industrial development.

Because of these multiple advantages affecting directly the quality of rural life, popularisation of biogas plants has been identified as an important item in the development plans of Government. The reasons for slow growth rate of biogas plants in India as compared to that of China are many - costlier construction costs (capital costs); uneven distribution of cattle; total absence of institutional structures to build biogas plants and more important to maintain them (one of the important links in fast diffusion of cycles transistors technology is availability of repair shops in villages or neighbouring small towns; this is totally absent in the case of biogas plants); social reasons like unwillingness to accept gas from cowdung; poor designs and operating systems leading to poor or no gas yields and problems of restarting; minimal training/extention facilities, etc. In order to increase growth rate, action on many fronts - technology, training, financial and institutional assistance - are being taken up and coordinated by a biogas directorate in the State Government.

Karnataka is quite fortunate in many infrastructural aspects like;

i) Biogas plants have been accepted by people and plants, both household ones and bigger ones, have been in operation for a number of years;

ii) KVIB has employed technicians in each taluk to handle biogas projects;

iii) A number of new designs have been developed in Karnataka - like ASTRA optimised design, University of Agricultural Sciences Bhagyalaxmi design, private farmer's design Amar and Raithabandu plants;

iv) Many organisations have taken up propagation on a turnkey basis despite many odds.

The State Government's enthusiasm can be seen from the fact that whereas until 1980 the number of biogas plants was about 8024, it decided to build 10,000 plants in one year 1982-83. Out of this target, nearly 7413 plants have been built through proper coordination and use of multiple approaches. The District Rural Development Societies and the Agriculture Department of the State Government are playing an important role in the diffusion process.

Regarding the Research and Development work on plant designs, the following important activities are taking place;

i) Normally, the plant design used has been the conventional KVIC (Khadi and Village Industries Commission) design. This uses a steel movable gas holder; due to corrosion this may need replacement/repairs. The University of Agricultural Sciences, Bangalore has designed a fixed drive model masonry/ concrete construction. This is considered to cost less than a KVIC model of corresponding capacity. The UAS through its extension services did a commendable job of installing a large number of plants in many places. The feed back information obtained was used in removing bugs in the design. Currently, the UAS is actively involved in training and installing biogas plants in the State. This plant still has some bugs especially in the Malnad region. To overcome these problems, two new designs have been evolved by two private farmers in Sirsi and Sagar taluks. Details of these plants are given later.

ii) ASTRA, IISc realised early that biogas is a potential and important decentralised and environmentally sound energy source in rural areas. With this aspect, it started many research programmes. The first programme was to build an instrumented biogas plant of about 6.7 cum/day capacity (gas). A side pit was dug to facilitate instrumentation. Samples taken at different heights showed that the minimum height of digester needed for anaerobicity and optimal gas production is around 5'. Secondly temperature probes were also used to measure temperature at various points. The plant went into operation in 1979 and continues to be operative. Yield analysis, mass flow analysis, input/output/gas analysis were conducted to study ingradients and other aspects.

Based on the above experimentation, an optimal design has been proposed reducing retention time and optimising dimensions for minimising capital and running costs. This design was used in the construction of the next ASTRA plant.

Another study modelled the plant for thermal studies in order to study the temperature profile within the plant. It is known that for optimum yields of gas, the plant temperature should be around 35 C. Hence it is desirable to minimise heat losses from the plant and also try to improve the temperature inside the plant by other simpler means. A modification to the existing plant was proposed to include a solar water heating system on top of the gar holder and charge cowdung with the hot water obtained from the solar water heater. This improved the performance of the plant and yield of gas increased from 38.4 cm³/g of fresh dung to 42.8 cm³/g (10.9%).

In addition, the solar water heater system supplied distilled water also (1.7 litres/day). A separate collector inside was provided to collect distilled water.

Raitha Bandhu Biogas Plant

Some of the major complaints about biogas plants in Malnad areas have been;

i) the flooding of plants by the intense rains during monsoons and

ii) non availability of gas during winter months.

This biogas plant called Raitha Bandhu has been developed by a farmer in Sagar Taluk (Shimoga District) based on practical experiences and experimentations in the field. The basic features of the plant are;

i) The digester is constructed with stone slabs;

ii) The gas holder consists of a number of mudpots kept on stone rails and covered by mud and a small percent of cement;

iii) All round trench has been provided to drain rain water;

iv) The outlet is provided at a level higher than normal so as to increase pressure inside slightly;

v) The sludge mixture on the output side has lower temperature, because of lesser reactions taking place at that end; an innovative and simple feedback mechanism has been introduced to increase the temperature. A small part of fresh dung is directly loaded into this part also by means of a separate, small pipe connected to this section. The main dung comes from the inlet pipe at the other section;

vi) Normally both inlet and outlet pipes get clogged due to various reasons; in order to clean the pipes, a plastic rope has been permanently connected through in a circular fashion; by pulling the rope, particles that clog the inlet can be pushed in thereby allowing free flow of dung.

These innovative, simple and useful features have made this biogas plant an attractive model. Its other advantages are;

i) Reduced consumption of cement (a necessity due to scarcity of cement);

ii) Low cost of construction;

iii) Ease of repair by local people (steel drum gas holder in conventional KVIC design has to be transported to an urban area even for minor repairs entailing expense and inconvenience.

Since this model was not approved by Government of India, the State Department of Science and Technology agreed to support this plant after being convinced of the feasibility and technical soundness of the design. The Department approved subsidies for construction of about 50 plants. It is now more than a year since these plants have been put up. The farmers have taken to this plant enthusiastically. It is also reported that the plants are working successfully.

Amara Gobbara Anila Yantra

In order to reduce consumption of cement by using local materials and thereby reduce the cost of construction, a farmer in Sirsi taluk has designed and constructed a stone slab based biogas plant called Amara Gobbara biogas plant. The construction of the digester and dome is by stone slabs. A thick stone rail support is given at joints between slabs so as to reduce gas leakage. This plant can be constructed above ground level to avoid flooding during rains. A registered

Society was founded in Sirsi to take up popularisation of this plant. It put up a few plants in

Sirsi. Currently, the group is trying to improve the construction to avoid leakage.

Community Biogas Plants:

Since cattle distribution amongst rural population is highly uneven (80% of cattle owned by 20% of the people), biogas can reach a large number of people by means of community systems. Many experiments on community biogas plants have not succeeded because of social problems. A successful system has been put up by ASTRA at Pura village in Kunigal taluk under a project funded by KSCST.

The project has two 750 cft/day biogas plants connected by a 1500m long network of PVC pipes to specially fabricated low cost burners in all the houses. The system is in operation from June 1, 1982. Cooperation from villagers is very good.

The village is a small and homogenous one with good social stability. Hence the biogas plants were accepted easily by local people. In addition to proving the success of a community based system, the project also had a few interesting findings;

i) Average yield of cowdung/cattle/day is around 1.86 kgs and not 7.35 as assumed;

ii) Gas consumption also is higher 0.212 m³/person/day as against 0.072 assumed;

iii) Population increased by 35% during the period of experimentation;

iv) Diluted slurry output is not accepted by local people and so it is being filtered by a sand filteration system.

Wind Mills:

Wind energy investigations are going on at Central Power Research Institute, National Aeronautical Laboratory and Indian Institute of Science; various types of wind mills like inexpensive, local materials based savonius rotor ORP - Tool etc. have been designed, fabricated and field tested by these organisations. The IISc design, a novel one, uses local materials. The water pump is designed with the help of a scooter tyre. A wind mill based on this design costs around Rs. 3000/- and has been working for more than three years in the extension centre of ASTRA at Ungra village.

The NAL - WPZ design is a horizontal axis American metal vane type wind mill with a plunger pump. It has a 4.9m rotor carrying 12 cambered steel vanes. A practical version delivered 0.61 lts of water against a total lift of 7.6m at a wind speed of 2.8 m/s. The initial cost is about Rs. 16,000/- (Rs. 850/m²) efficiency being 18%. NAL has also developed another multipurpose wind mill for wind speeds of 3-5 m/s at a cost of around Rs. 350/m². Currently they are working on large power wind mills.

The IISc - ASTRA savonius wind mill is a vertical axis sail type one with the rotor supported on two frames. One of the interesting design features is the provision of a twisted wire joint which automatically allows sails to open up a higher wind velocities. The efficiency is around 11% with a discharge of 0.22 l/s for a lift of 5.4m when wind speed is 2.5 m/s. This design is optimised for cost (Rs. 375/m²) and low wind speed operation.

Wind potential estimates are being collected by IISc, NAL and KSCST (through its wind stations in Engineering Colleges) so that reliable data on wind energy will be available for every spatial location and every day.

Solar Devices:

Solar devices like cookers, water heaters etc. have reached the stage of commercial manufacture. Many industries have taken up manufacture of solar devices for more than three years and the State and Central Governments encourage use of such devices through subsides, tax rebates and loans.