Economic Comparison off Grid System

Q1 : Sizing of Solar Panel System Let us consider that one house needs following loads; 10W, 2 lamps for 3 hours 8W, 4 lamps for 3 hours 12” Black and White Television for 3 hours per day Consider the Insolation Level of the area 5.5k Wh/m2/day and system voltage of 12V. Battery and Regulator Efficiencey is 0.8 and 0.9 respectively. Calculate the capacity of Solar PV panel and battery size to meet this requirement

Characteristic Curves of a Solar Photovoltaic Module

Answer : Energy requirement = (10 x 2 x 3) + (8 x 4 x 3) + 20x 3 = 216 Wh/day Array Load = 216 ( battery and regulator efficiency) = 216 / (0.8 x 0.9) = 300 Wh Array Size = Array Load / (Insulation x mismatch factor ) = 300 / (5.5 x 0.85) = Wp

Say we use 2 x 32 Wp solar panel Battery size ( Assume that the max. Battery discharge is 20%) Daily consumption / max. discharge x nominal voltage =216 / (0.2 x 12) =90 Ah

Calculation of unit cost of Electricity Say, cost of 32W Solar Panel Rs. 8000/- Cost of 90 Ah. Battery Rs. 3000/- Cost of other accessories Rs. 1000/- Total Cost (2* ) = 20,000/- Useful Energy = 216 Wh./day Assuming 20 yr. life, 10% discount rate cost of energy = 20000/216*365*8.51/1000 = Rs./k Wh.

Q2 : Electrification with Solar Photovoltaic Systems In isolated installation is to be provided with three phase 400 V a.c. supply to power its entire energy needs. The connected laod of the installation is 20kW with a load factor of 0.3 and the load is assumed to be balanced. i)Give the number if 54W solar panels required to meet the entire load. The solar insolation is 5.5 kWh/m2/day, the mismatch factor is 0.85 and other down stream efficiencies are cumulatively 0.9. ii)Calculate the Cost of Unit of energy of Solar PV installation.

Answer : (i) The energy required per day = 20 x 24 x 0.3 = 144 kWh/day Number of Solar panels required = 144 x 1000 / ( Insolation x mismatch factor x efficiency x capacity of each panel ) = / (5.5 x 0.85 x 0.9 x54) = Say 634 panels.

(II)Calculation of Unit Energy Cost Let us consider cost of a panel is Rs. 25,000 Total cost of 634 of PV panels = 634 X 25,000 = Rs. 15,850,000 Total cost (including installation cost) = 1.5 x panel cost = 1.5 x 15,850,000 = Rs. 23,775,000 Total annual Energy = 144 x 365kWh/annum = 52,560 kWh/annum

Let us consider 20 years of lifetime and 10% discount rate the present value factor 8.51 Unit Energy Cost =23,775, x 52,560 =53.15 Rs / kWh

Q3 : Supply of Grid Electricity for Isolated Village 100 houses each require 45 kWh/month, and the village is situated 5 km away from the nearest 33kV line It is rquired to construct 5km pf 33kV pole line, install a 100kVA transformer and 2kn LT distribution line around the village. Cost associated only with this infrastructure development is calculated as follows ;

Construction of 5km 33kV line = 5 x 600,000 = 3,000,000 Rs. 2km of LT distribution line = 2 x 400,000 = 800,000 Rs. 100 kVA transformer = 500,000 Rs Total Cost = 4,300,000 Rs Annual Energy consumption = 45 x 100 x 12 = 54,000 kWh / annum Assume present value factor 8.51 for 20 year lifetime and 10% discount rate The Unit Energy Cost = 4,300, x 54,000 = 9.36 Rs. / kWh

Note : If No. of Houses are 10 (i.e. village is poorly populated); Unite Energy Cost = 4,300, x 5,400 = Rs If the is village is too far from the grid (about 10km) Unit Energy Cost =7,300, x 54,000 =Rs

Q4 : Electrification with a small Hydropower Unit Let us consider that the village consist of 100 households and limit their consumption up to 100W. for 3hrs./day Energy per household per month= 100 x 3 x 30 = 9000 Wh/month = 9kWh/month Total power requirement = 100 x 100 = 10,000 W = 10kW Assume overall efficiency of the electrical system as 0.75 Then required capacity of the plant – 10/0.75 = 13.33kW

Say 15kW unit is installed. Total Cost (i.e. including all civil, mechanical and electrical components) = 1,800,000 Rs. Let us consider 20 years of lifetime and 10% discount rate then the present value factor = 8.51 Unit Energy Cost = 1,800, x 9 x 100 x 12 = 19.58