Numerical Analysis of Novel Savonius type Hydrokinetic Turbine

Abstract

Small-scale renewable power systems have gained attention in the past few years because of climate change, increased urbanization, global warming, excessive use of fossil fuels and high transmission costs. The push for a greater share of renewable energy in the overall energy mix is of more significance to Pakistan due to the chronic power shortfall and huge oil import bill. Some of the renewable energy resources often use these days are biomass, wind, hydro, solar and geothermal. Hydropower is the most abundant (water covering 71% of the planet) and economical source of renewable energy. Generally, there are two ways to harness energy from water, one is the hydrostatic approach which uses the potential head of flow and the other is a hydrokinetic approach that uses the kinetic energy of incoming flow to rotate the turbine. The conventional hydrostatic method requires the development of grandiose structure and construction of dams or reservoirs for power generation, storage and transfer. In contrast, hydrokinetic turbines require less or no civil work. Among hydrokinetic turbines, savonius type hydrokinetic turbine is environment friendly, simple and low cost power generation device for low speed flows. On the other hand, savonius hydrokinetic turbines have less power coefficient and torque than other hydrokinetic turbines. In this study, a novel Savonius type low speed hydrokinetic turbine has been proposed after careful analysis of torque and power coefficient at Tip Speed Ratio (TSR) range from 0 to 1.2. The proposed design comprises of S1048 section profile of diameter 0.33m having 14% more power coefficient than conventional savonius rotor. The S1048 section profile is utilized first time to design the blades of savonius hydrokinetic turbine using novel airfoil sectioning procedure. Transient CFD analysis has been carried out to obtain performance and torque coefficients. The numerical study has been carried out using finite volume method and RANS code with an inlet water velocity of 0.38m/s. K-ω SST turbulence model has been used to resolve turbulence effects. In addition to that, an existing augmentation system comprising of curtain arrangement has been used with S1048 section rotor to further increase the turbine efficiency. The maximum power coefficient has been found equal to 0.43 at TSR of 1 using curtain plate augmentation system. The proposed turbine is in good agreement with validation model and is feasible for experimental testing and can harness power from low speed and low head water flows.