Design, Development and Optimisation of a Novel Hybrid Renewable Energy System integrating with Pumped Hydropower Energy Storage

Abstract

Worldwide, the overdependence on conventional power plants for electricity generation has been one of the most significant economic and environmental challenges as it exacerbates the depletion of valuable non-renewable resources, like oil and natural gas. Therefore, renewable energy sources represent the most viable option for overcoming this issue, triggering most governments internationally to prioritise these resources. Recently, a hybrid renewable energy system consisting of wind turbines and photovoltaics system combined with pumped hydroelectric energy storage has received considerable interest, and this research, therefore, focuses on such a hybrid system. However, there are essential technical, economic, and environmental factors to consider in designing and optimising such a hybrid system, and performing an accurate simulation of each sub-system increases the certainty of achieving desirable outcomes. Regarding pumped hydro power storage, neglecting crucial parameters, such as head losses and evaporation rates, might reduce the accuracy of the total simulation performance, resulting in an underestimation of the correct size of each component of the hybrid system. The first aim of this research is to investigate this issue by proposing a robust approach with a strategy to establish the ideal pipe design through an in-depth techno-economic assessment. A comparative analysis of two different scenarios – one considering head loss and other without considering it – is carried out. A wide range of proposed hybrid system configurations is thoroughly investigated. The essential performance indicators employed for designing the proposed system are the renewable energy fraction and loss of renewable energy, and the results reveal improvements in these two indicators by approximately 8.6% and 3%, respectively. The most significant annual variations between the two scenarios regarding the total demand satisfied by the proposed system and the amount of renewable energy loss are 218.23 GWh and 89.39 GWh, respectively. The pipe efficiency of the pumping and generating modes, determined through a sensitivity analysis, ranges from 91–99% and 76–95%, respectively. These findings could assist designers in making initial assumptions about such parameters with reasonable confidence. The second aim of this research is to accurately design each component of the hybrid system while considering the technical, economic, and environmental perspectives; conduct a comparative analysis; and increase the robustness of the model outcomes. Therefore, a multi-objective optimisation model is developed to accurately size each component of the proposed hybrid system. The developed model objectives include incorporating a head loss factor into the model (as proposed in the first aim of this research), considering the capacity factor as the main metric for designing energy storage, and conducting a techno-economic environmental assessment considering a greenhouse gas emissions credit. In addition, three different algorithms (non-dominated sorting, reference direction-based, and two-archive evolutionary) are developed. The proposed system, which includes a mix of solar and wind energy, can cover up to 93% of the total demand with a maximum capacity factor of 27%, which is much better than using solar or wind alone (i.e., 62% and 70%, respectively) at a capacity factor of 18%. The levelised cost of energy for the proposed system ranges from 0.07 to 0.22 $/kWh, largely influenced by government subsidies. Regarding conventional electrical power plants, peak load units require the technical specifications of high reliability and dispatchability owing to sudden increases in demand, and base load units should be qualified to generate constant, uninterrupted power. However, some renewable energy sources, such as photovoltaic systems and wind energy, are not considered reliable sources to cover such a demand for a specific period due to fluctuations in natural resources and variations in electricity demand. This critical issue is subject to a supply–demand mismatch, and the third aim of this research is to tackle such a problem by adding a dispatchable renewable energy resource (bioenergy) to the proposed hybrid system. This study also focuses on increasing the whole system’s reliability and dispatchability during peak periods and reducing losses of renewable energy. Moreover, a novel operational strategy and several design techniques are proposed, and some essential objectives are added to the developed optimisation model, such as the round-trip efficiency of pumped hydro storage. According to the results of a comparative analysis, all these design techniques seem effective and generate favourable results. In addition, the most competitive technique reveals that the reliability of the entire system increases by almost 6%, while the loss of renewable energy is reduced by 15%, and the levelised cost of energy reduces from 0.22 to 0.13 $/kWh. Significantly, considering renewable energy sources in terms of their technical specifications, such as the level of source dispatchability, could assist designers in deriving more economic benefits from designing such sources.