Wind power generation has increased in Pakistan over the last decade as newer renewable resources were explored to curb the electricity shortfall in the country. The Gharo-Jhimpir wind corridor, in the province of Sindh, was identified as the most lucrative site for establishing wind power plants in the country. As of now, the Jhimpir wind site alone provides over 70% of the total wind power generation in Pakistan with over 20 operational wind farms and more in the development phase.
Due to the limitations in terms of a reliable wind resource, available land, project economics, and proximity of electrical grid and communication systems, a wind site can reach a high occupancy due to lesser than ideal intra- and inter-farm distances between wind turbine generators. As a result, energy generation from the downstream located wind farms can be reduced substantially due to the complex wake topographies emerging from the upstream wind farms. Such wake structures are characterized by a wind speed deficit and an increase in the turbulence for downstream wind turbines. In this context, quantification of intra- and inter-farm wake interference is essential to devise an effective re-powering strategy for wind farms. re-powering would enable an increase in the generation capacity of wind farms either by refurbishment of deteriorated wind turbines or by replacement of the wind turbines with new and more efficient units.
In a recent study conducted by the future power research group of USPCAS-E NUST, two of the upstream wind farms operated by Zorlu Energy Ltd (Zorlu) and Three Gorges First Windfarm (TGF) have been found to have a substantial impact on the wind and power deficit of the downstream wind farm operated by FFC Energy Ltd (FFCEL).
The wind farms under consideration are identified as three of the oldest wind farms operating in the Jhimpir wind corridor. The wake analysis has been made with mesoscale simulations run by the Weather Research and Forecasting (WRF) model coupled with the wind farm parameterization scheme. The simulations have been conducted for ten days in Summer 2018, when the high-speed sea breeze approaches Jhimpir from the South-West direction (also the most dominant wind direction). Wakes induced by upstream wind farms have been observed to reduce wind speed and power output by up to 15% and 35%, respectively. The observed data obtained from FFCEL for their 33 x 1.5 MW Nordex S77 type wind turbine generators operating in Jhimpir validated the simulations. Due to an expansive wake flow topography, vertical relocation of 15 most deteriorated wind turbine generators from current 80m hub height to 100m hub height was recommended in the study. As a result, an increase in the power output of about 13.6% is obtained in the 15 re-powered wind turbine generators along with an average power output increase of 7.5% from the wind farm under evaluation. A unique contribution of this work was to demonstrate, in a specific case study with upstream wind farms, how the relative importance of lateral vs. vertical relocation of wind turbine generators can be evaluated from a re-powering perspective.
This advanced study is a result of a dynamic collaboration between academia and the wind power industry to achieve sustainability in high-quality research capacity in Pakistan. The USPCAS-E’s future power research group is striving to provide technical and policy guidelines to expand the wind energy sector in Pakistan. The novel research will also have socioeconomic effects on the energy outlook of Pakistan by supporting the Government of Pakistan’s aim to inject 30% renewable energy in the national energy mix by 2030, adherence to the United Nations’s Sustainable Development Goals (SDGs) SDG No. 7 ‘Affordable and Clean Energy’ and SDG No. 13 ‘Climate Action’, and provision of key guidelines to regulatory bodies such as the Alternative Energy Development Board (AEDB) when developing new wind farms in Pakistan. The energy center is looking forward to expanding the research via LiDAR based wind shear profile and turbulence measurements in Jhimpir region to gain further insight into the complex intra- and inter-farm interaction between wind turbine generators.
Reference:
H. Syed, A. Javed, R. A. Feroz, R. Calhoun, “Partial Repowering Analysis of a Wind Farm by Turbine Hub Height Variation to Mitigate Neighboring Wind Farm Wake Interference using Mesoscale Simulations”, Applied Energy, vol. 268, pp. 1-15, 2020. DOI: https://doi.org/10.1016/j.apenergy.2020.115050. (IF-8.426)
The author is an Assistant Professor and the Head of the Thermal Energy Engineering (TEE) department at USPCAS-E NUST and can be reached at hod.tee@uspcase.nust.edu.pk 
