Appraisal of Centralised and Decentralised Energy System

Distributed generation (DG) based on locally available renewable sources of energy would play pivotal role in meeting the energy demand throughout the country. Distributed generation refers to the electric energy generation near load centres using locally available resources. Installed capacity of decentralised plants ranges from few kilowatts to megawatts. DG include various renewable energy based generating technologies such as rooftop solar PV installation, micro/pico hydro power generation, small scale wind plants, biomass gasifier, combined heat and power (CHP) plants etc. [1]. These DG systems have very minimal environmental impact and are easier to install and operate. Since the generated energy will be supplied to the local community load, transmission and distribution losses will be greatly reduced. The other benefits of DG include improvement in power quality, avoiding or reduced transmission line extension costs due to generation at load centres, reduced power loss and reduction in energy price at local level while contributing to rural electrification [2]. The centralised power systems have posed many technical challenges such as higher T & D losses, frequent voltage variation, frequency variation and reliability concerns with massive environmental pollution. There are more than 24,000 villages not electrified even today and many of them are in very remote places where the grid extension is economically non-feasible [3]. The grid extension to remote location costs about INR 1/kWh/km which is economically not viable with the present higher T & D losses [4]. T & D losses have increased from 17.5% (in 1970-71) to 24.1% (in 2011-12), over 4 decades in spite of development in technology and use of efficient transmission conductors. Figure 1 shows the T & D losses in the country over the years [5]. Increased T & D losses stress the transmission line, necessitates higher generation of electricity.

Grid expansions for rural electrification in remote areas are expensive and inefficient necessitating distribution generation system [6-8]. Even already electrified villages are facing the problem of unreliable power supply coupled with frequent severe voltage fluctuations. However DG’s based on locally available renewable energy sources with the lower T & D losses have proved to be economically viable and technically feasible

Figure 1: T & D losses in the country from 1970-11 to 2011-12

Figure 2: Comparison of PV, diesel generator and grid electricity for rural electrification [9]

Figure 2 illustrates (Kamalapur et al. 2010) the cost appreciation as the distance of the load centre and grid increases. Beyond 6 km, grid expansions are economically non-viable. This necessitates onsite generation (DG) and distribution to households in remote areas to minimise the investment on infrastructure apart from transmission and distribution (T&D) loss of electricity. Line loss reduction with DG integration has been computed for various levels of penetration. Estimates indicate annual loss to the tune of 264 billion units (26400 GWh) or which costs minimum of INR 55 billion per year due to transmission and distribution inefficiency (Table 1). Current assessment reveals that T&D loss in India is about 24% resulting in the loss of 220 kWh/capita (per capita consumption is 917.18 kWh) of energy. Cost per capita of energy loss ranges from INR. 462 (@ INR. 2.10/kWh) to INR. 3220 (@ INR. 7/kWh) depending upon the tariff (in the respective state).

Table 1: Expenditure due to T & D losses in India

Per capita electricity consumption	917 kWh
T & D losses	24%
Per capita energy loss	220 kWh
Cost of per capita energy loss	INR 462 to INR 3220
Annual energy loss	264GWh
Total annual expenditure	INR 55,440 crores (@ INR. 2.10/kWh)

This necessitates deployment of DG using locally available resources to improve the efficiency of electricity transmission and distribution. India is targeting 22000 MW of Solar installed capacity by 2022 in which distributed generation hold the promise. India is one of the frontiers of wind generation with installed capacity of over 21 GW after China, US, Germany and Spain. Taluk level energy assessment gives insights to explore the feasibility of distributed generation opportunities and connect un-electrified villages in the region. This also helps in integrating renewable energy resources to the existing grid which will improve the power quality [10].