Evaluation of Pumped Storage Hydropower and its integration with Variable Renewable Energy Generation in National Grid of Pakistan

Abstract

The transition from fossil fuels to clean energy is crucial for limiting climate change. Pakistan needs adequate energy storage capacity to ensure grid reliability, support 6.5% variable renewable energy share in installed capacity and 4.2% annual energy and adopt a 30% renewable energy share by 2030.

Pumped storage hydropower is an affordable, grid-scale energy storage technology that can be combined with other technologies to reduce variable renewable energy curtailments. It offers reliable operation, reduces curtailments, and utilizes renewable energy, reducing emissions and conventional fuel requirements. The development of new pumped storage hydropower projects is challenging due to uncertainties such as market structure, long-term natural gas prices, renewable energy penetration, government incentives, and regulatory policy. Retrofitting pumped storage hydropower to existing conventional hydropower is the most convenient, economical, and sustainable way to achieve this goal. This research aims to evaluate the techno-economic feasibility of pumped storage hydropower project by implementing two strategies: Reducing capital costs by retrofitting pumped storage hydropower to utilize the existing infrastructure of conventional hydropower. Secondly, by decreasing pumping/charging costs by utilizing a water stream reaching directly to the upper reservoir to maintain an equilibrium between energy consumption and energy generation. Furthermore, the model is extended to integrate floating solar photovoltaics technology with pumped storage hydropower and conventional hydropower to address the water supply issue in arid regions, improving the water, energy, food, and ecosystem nexus for a comprehensive, cost-effective solution.

The site screening indicates that the upper reservoir in the Sharan Forest area, near Balakot conventional hydropower, is the most favorable site for retrofitting pumped storage hydropower. Balakot conventional hydropower is a 300 MW run-of-river hydropower facility on the Kunhar river in Pakistan's Khyber Pakhtunkhwa province. An extensive power & energy model for the simultaneous operation of pumped storage hydropower with interconnected conventional hydropower was developed, focusing on daily water balance for the whole year. The main concern is to maintain/increase conventional hydropower energy generation by optimizing design discharge, comparing capacity optimization with and without water streams, considering environmental flow, maintaining the balance between pumped storage hydropower and conventional hydropower operation, and regulating pumped storage hydropower operation to adapt discharge variation throughout the year. The major milestones include identifying sites, marking structures, analyzing hydrological data, and optimizing power and energy. Next step was to include performance evaluation of fixed and variable speed reversible pump turbines. The model is extended to integrate floating solar photovoltaics technology with pumped storage hydropower and conventional hydropower. Techno-economic evaluation is conducted including development of various scenarios, cost estimation, energy assessment, certified emission reductions assessment and calculation of levelized cost of energy storage for all the Scenarios.

The study reveals that a hybrid configuration of 200 MW Paras pumped storage hydropower and 24-hour energy storage can reduce installed costs from 3.46 to 2.57 US$ Million/MW (-26%) and reduce energy usage by up to 95 GWh/year (-14%). This is due to utilizing existing conventional hydropower resources, considering water stream, environmental flow, and reducing evaporation through floating solar photovoltaic installations. The levelized cost of energy storage can also be reduced from 13.7 to 11.5 US$ cents/kWh (-16%) compared to greenfield closed-loop pumped storage hydropower. The hybrid configuration provides a competitive grid-scale energy storage solution with a levelized cost of 10.0 US$ cents/kWh for 1000 MW pumped storage hydropower with 24- hour energy storage. This configuration increases clean energy output by 7,440 GWh (+24%) and generates $187 million in revenue over 60 years.