3.5.Computation models

The energy planning endeavour for a particular region involves the finding of a set of sources and conversion devices, so as to meet the energy requirements/demand of all the tasks in

1. Regional energy system: Resources form inputs and consumptions by different tasks via varied technologies of conversion form outputs in the regional energy system.The energy sources are both renewable and non-renewable. Renewable resources presently in wide use in Uttara Kannada district are firewood, agro residues and animal wastes. Out of these resources, firewood is fast dwindling because of its uncontrolled and inefficient usage and increasing demand due to increase in population, affecting adversely the quality of life and environment. This is evident from barren hilltops in the densely populated coastal taluks of Karwar, Kumta, Honnavar, Ankola and Bhatkal. There is thus, an urgent need to tap new and technically feasible resources, such as, solar, wind,potential energy of water and biogas, in a decentralised way [23]. The renewable energy resources readily available in the region are
1. Bioresources: firewood, agricultural and horticultural residues, animal wastes—either used directly or converted into biogas [28,30].
2. Potential energy of water: used to drive mechanical devices, and converted to electricity [35,36].
3. Wind energy: converted to rotary mechanical energy using turbines, and converted to electricity [37-39].
4. Solar radiation: can be used directly through thermal device-flat plate collectors or concentration, and converted to electricity using PV (photovoltaic) or thermal devices [40^13].

Resources such as tidal wave energies are still in experimental stage and are not estimated/included in the regional energy plan.

2. Tasks: The tasks can be categorised based on their thermodynamic characteristics, such as, type and quality of energy needs [23,24]. These are
1. Low grade thermal energy (less than 100 °C): needs, such as, domestic water heating, space heating, grain drying, and process heat for small-scale industries.
2. Medium grade thermal energy (100-300 °C):

• cooking in households,
• village industries, such as, jaggery making, areca boiling, parboiling, etc., and
• small-scale industries, such as, cashew processing, brick kilns, tile industries, etc.

• pumping water for domestic purposes, irrigation, etc., and
• small-scale industries like rice mills, etc.

Integration of sources: System integration involves mixing of all sources via a number of devices to meet the demand of various tasks. An optimised regional energy system involves proper mix of energy systems, which involves proper mix of energy sources that supply energy required for various tasks through appropriate devices based on the second law of thermodynamics. The sources may be primary and local in nature (firewood, solar, wind, etc.) or intermediate, which are produced within a region, such as, electricity from solar, wind and bioresources, producer gas from wood, biogas from organic wastes (such as animal dung, green leaves, etc.) or non-local resources trans¬mitted/transported from outside the region, such as, grid electricity, kerosene, diesel, petrol and LPG.
There are various approaches in integration, such as

1. Combining: In combining sources approach, two or more energy sources act in conjunction to perform a single task. For example, biogas and diesel are both used to run an engine which could be coupled to centrifugal pump to pump water, or to a generator to generate electricity for lighting, pumping, industrial applications, etc.
2. Cascading: Principle of cascading involves usage of heat or waste energy (low grade energy) that is produced while performing a task. This low grade energy could be used for low grade thermal energy tasks. For example, waste heat from an engine may be used to carry out a heating task.
3. Time sharing: Devices make use of same resources for different tasks at different intervals of time.

        In an integrated energy system, integration occurs at three levels. Firstly, several energy sources are integrated into a single energy system. Secondly, traditional components are integrated into introduced technologies. Thirdly, energy system is integrated into the fabric of the local society. Such integrated systems change continuously as they are adjusted to new situations of energy availability and utilisation. Hence, the regional energy systems must be dynamic and interactive to be effective. But, Uttara Kannada region is basically rural and economy is sluggish, hence the first two levels of integration suggested are more valid. Integration of various resources and devices to perform various tasks in a region is listed in Fig. 2.