Integrated renewable energy systems utilise several manifestations of solar energy such as solar heat, solar radiation, wind, biomass and falling water to satisfy various needs in tandeum. Such a system will
(a) Satisfy basic needs: provide continuous energy supply of the type which will be most inappropriate and cost effective in relation to specific application.
(b) Renewable, sustainable and available in the immediate environment
(c) require minimum handling, transport and transmission
(d) protect and improve the environment and shift the emphasis from the much abused standard of living to the quality of life.
(e) transfer benefits including employment in the immediate environment rather than in the faraway places as in the case of centralised systems.
(f) establish a symbiotic relationship among man, environment, resources and technologies.
The organisation of such independent, self contained, integrated energy systems will depend upon accessibility to potential technological intervention possible in a given socio-economic situations at the micro level. The extent to which energy transformation and quality upgradation should be attempted to satisfy energy needs within the framework of socio-economic, ecological parameters must be established. Depending upon the economic method of performing various tasks, the needs of the community for thermal, mechanical and electrical energy are assessed. For most applications there are two or more possibilities of energy supply - solar, fuelwood and biogas for cooking; biogas and electricity for lighting; mechanical power for irrigation and wind mills or biogas engine for other needs. Subramanian and Chetty, (1983) have adopted linear programming approach by restricting themselves to the cooking and lighting needs of a village in the arid zone of Karnataka. The implementation of the cost minimization linear programming model shows that the cost of some of the alternative options for meeting the cooking and lighting needs can be as low as one-sixth of the present expenditures. Some of the important findings are:
(1) the biogas route is an optimal route for lighting and cooking,
(2) the cost minimisation model allocates grid electricity lag behind the biogas- engine - generator electricity route.
(3) firewood stoves become part of the cooking solution only when the cost of firewood is reduced and stove efficiency is increases at low stove efficiencies firewood cook stoves do not find the solution.
Obviously the design result depend on the technologies and their effectiveness and on the cost of devices, all of which are in the state of dynamic change.
The important goals of an energy planning activity for a region is summarised as follows:
(i) Instead of generating more energy, we should start with conserving energy. Today the cost of conservation of energy equivalent to one KVA is less than the cost of generation of similar quanta. Some examples are: (a) industries can easily save up to 10% of their consumption with good house keeping practices. (b) use of energy efficient bulbs for lighting instead of incandescent bulbs will reduce power requirement in Karnataka by 200 MW or more. (c) use of efficient irrigation pumpsets will reduce power and energy requirements by 20%.
(ii) We should match the quality of resource with the quality of end use. Electricity need not be used for low quality activities like water heating. Industries consume about 40% of their electrical energy for heating requirement. This can be met by coal, firewood or oil over all coal, oil consumption.
(iii)It is desirable to use renewable energy sources. Solar energy should be used both in direct and indirect forms. Solar water heaters, dryers etc should be encouraged. Photosynthesis route should be used to improve biomass yields. Biomass and agrowastes can become a major source of energy for many years.
(iv) Seasonal hydroelectric projects should be preferred to annual and carryover schemes. Local people will also support such approaches. We can get the potential energy through a proper generation mix and local generation balance.
(v) People should be encouraged to set up microhydel plants on canals, rivers, streams and waste water flows. In a city like Bangalore, waste water to the tune of 300 million litres / day is flowing into valleys like Vrishabhavadhy valley, K and C valley and Hebbal valley. We should be able to use the head and generate power.
(vi) Industrial wastes are normally organic wastes. Industrial waste water especially from distilleries contain a large amount of organic matter reflected by their B.O.D. Gas generation units can be set up on them. They will reduce pollution and generate energy as a by-product. Health of the city will improve.
(vii) Biogas plants should be set up by trained people, operated properly with a maintenance team and organized in a scientific manner. Biogas plants can meet a substantial part of the states requirement. In addition they produce more nitrogen.
(viii) Industrial wastes especially lignin should be separated and briquetted as a fuel.
(ix) Recycling of wastes should be encouraged. This also reduces energy requirements in many cases.
While following the above, it is necessary to remember that there is no unlimited supply of energy (other than the solar energy) available for all time to come for our exponentially increasing usage.