Hybrid geothermal–PV–wind system for a village in Pakistan

Abstract

Combining diverse sources of renewable power into a hybrid renewable energy system (HRES) has gained more attractions with the fast evolution of the renewable energy market. Renewable resources as alternative energy for electricity generation are the only way to cater to the present environmental and social challenges. An on-grid hybrid geothermal–PV–wind system at Tattapani, Azad Jammu Kashmir, Pakistan, is considered, as enough geothermal energy is available from hot springs to cater for the perennial base load requirement of the small community. The paper presents HRES design with minimal net present cost (NPC), so that the PV and wind energy plants are used to complement the geothermal plant during high demand and to feed the grid during low-energy requirements. This results in reduced cost of electricity (COE) and the decrease in fossil fuel-reliant energy from the national grid, thus bringing prosperity for the poor people of the village and contributing to the reduction in global warming. Sensitivity analysis to the constraints such as solar irradiation, wind speed and interest rate is presented as well. The study showed that for Tattapani, an on-grid hybrid geothermal, PV and wind system with the capacity of 250 kw, 250 kw and 100 kw, respectively, is a feasible design with the NPC of 234.11 million rupees at the interest rate of 5%. The system can fulfill the average load demand 7350 kWh/day, while the surplus energy is sold to the grid. COE of the proposed system is 7.50 Rs/kWh, and the system will also evade 1.8 million kilograms of CO2 along with other flue gas emissions to pollute the atmosphere. Sensitivity analysis shows that if wind speed varies from 4.5 to 6 m/s while GHI remains constant, the cost of wind energy decreases from 20.08 to 12.5 Rs/kWh. Similarly, if average GHI increases from 4.5 to 6 kWh/m2/day and wind speed remains constant, the cost of solar energy decreases from 8.04 to 6.06 Rs/kWh. If wind speed and GHI changes at the same time from 5 to 6 m/s and 4.5 kWh/m2/day to 6 kWh/m2/day, respectively, NPC decreases from Rs245 million to Rs228 million keeping interest rate constant at 5%. Another important result showed that when interest rate changes from zero to 20%, overall NPC decreased from Rs294 million to Rs159 million and COE increased from 6.50 to 11.69 Rs/kwh.