OPTIMALLY LOCATING THE SMALL HYDRO UNITS TO MAXIMIZE POWER PRODUCTION UNDER UNCERTAINTY FLOW

Abstract

The scientific studies and various researches have indicated that global climate change trend is resulting in changes in precipitation and temperature. Variations in precipitation and temperature are threatening global fresh water resources. The glaciers are melting and overall quantum of precipitation is decreasing due to which, availability of fresh water is going to decline in future. In addition to this, due to changes in precipitation patterns and increase in winter temperatures, the flow patterns in rivers and streams are also altering. The variation in river flows is also a point of concern for locating, sizing, designing, planning and operations of hydropower plants. Small hydropower is a promising source of clean energy that is sustainable, affordable, economically viable and environmental friendly. Optimal performance of the small hydropower plant and maximum possible utilization of flow to generate electricity is dependent upon quantum of available flow throughout the year. Global climate changes and their impacts, particularly on river and stream flows are making it too difficult to ascertain the available flow. This is affecting decision-making process for site selection for small hydropower plants, locate appropriate Probability of Exceedance (pe) for design flow, size small hydropower plants based on design flow and estimate power generation throughout the plant life. Due to this, it is becoming difficult to optimally size small hydropower plants and predict their performance during operations. In this research work, future river flow of Chitral River was predicted under climate change scenarios, mechanism was established to improve decision making in site selection for small hydropower generation, locate appropriate pe for plant sizing, work out optimal size of the small hydropower plants and estimate power production capacity. Chitral River in Upper Indus Region, Pakistan is selected as study area for the research work. Initially, it was intended to extend the scope of the research work to upper Indus Basin, however, due to time constraint, data constraint and limitation of funds, the focus was limited to Chitral River. OPTIMALLY LOCATING THE SMALL HYDRO UNITS TO MAXIMIZE POWER PRODUCTION UNDER UNCERTAINTY FLOW xv | P a g e Irfan Yousuf 2K11-UET/PhD-CE-48 In order to undertake this research work, historical data including climatic data of Chitral for the period 1984-2013 was obtained from Pakistan Meteorological Department and water flows data of Chitral River in Chitral for the period 1989-2013 was obtained from Water and Power Development Authority. This research work has used LARS WG 5 Model to downscale future temperature and precipitation data from MPEH5 Global Circulation Model (GCM) for a period up to 2099 under Special Report of Emission Scenarios (SRES) A1B and A2 as that were used by the Intergovernmental Panel for Climate Change (IPCC) under its fourth assessment report of climate change published in 2007 i.e. AR4. For analysis, future projections made under A1B scenario was used deeming that in future, efficient technologies will be introduced, reliance upon fossil fuel based power generation will be reduced and other supply options and end-use technologies including clean technologies will be developed. HEC-HMS model was used to determine future river flows in Chitral River. The historic and future river flows were used to size small hydropower plant using RETScreen 4.1 model. Multiple Objective Decision Making Methodology (MODM) was used to decide upon the optimum site and size of the small hydropower plants. The results of climate modeling under A1B scenario indicated that the precipitation in Chitral is going to decline during the period 2011-30, 2046-65, and 2080-99, however, during the period 2080-99 a slight improvement was seen as compared to other two periods. The predictions for temperature under A1B scenario indicated continuous rise during the period 2011-30, 2046-65, and 2080-99. Results of HEC-HMS indicated a declining trend in the future average annual water flows of Chitral River during the periods 2014-30, 2046-2065 and 2080-2099.However, during 2080-99 a slight improvement in river flows as compared to 2014-30 and 2046-65 was seen. This research determined that there would be 16.8% reduction in river flows simulated for 2011-30, 25.0% for 2046-65 and 22.0% for 2080-99 as compared to historical flows during 1989-2013. This trend was matching with the trend of precipitation in the region. The MODM was used in improving decision-making process for site selection for small hydropower plants. For that purpose, four alternate small hydropower sites in Chitral River, Chitral were analyzed taking into consideration climate, hydrology, OPTIMALLY LOCATING THE SMALL HYDRO UNITS TO MAXIMIZE POWER PRODUCTION UNDER UNCERTAINTY FLOW xvi | P a g e Irfan Yousuf 2K11-UET/PhD-CE-48 technological, environment and safety factors. Based on outcomes, the Chitral Small Hydropower Site was selected as optimal site among the four selected alternatives at Chitral River. The historical and future predicted available flow data was used to determine impact of variation of flows on power generation capacity of the small hydropower plant. The analysis indicated that the declining trend of the flow in Chitral River will result in reduction of power generation capacities i.e. there will be 0.36% impact on yearly power generation due to river flow changes simulated for 2014-30, 6.25% for 2046-65 and 4.08% for 2080-99. It was inferred from the research that in order to optimally utilize future available flow in rivers like Chitral River for power generation, the pe of design flow on Flow Duration Curve (FD Curve) should be between 32-40%. RETScreen 4.1 software was used to determine appropriate sizes of small hydropower plants based on historical and future predicted flows. The outcomes were analyzed using MODM for improved decision making in selecting optimal size of the small hydropower plants. The results concluded that 49.60 MW would be the most optimal size of the small hydropower plant that will produce maximum electricity under future projected flows at the area under study. This research work has presented a new dimension before the planners, designers and decision makers and has recommended that while designing, locating and sizing small hydropower plants the future predicted climate conditions and river flows should be taken into account in addition to the historical records at a time when the decision-making is done for locating and sizing small hydropower plants to ensure better performance. With this, impacts of climate changes on water resources and climate can be largely taken care of.