Volume 211, April 2025, 115361

https://doi.org/10.1016/j.rser.2025.115361

Highlights

  • •SPHS using desalinated water can play a critical role in decarbonizing Saudi Arabia’s power sector.
  • •Ten potential SPHS sites presented with a total seasonal energy compensation capacity of 130.6 TWh per year.
  • •The ten proposed projects can store up to 14.7 km³ of desalinated water in the winter.
  • •The two SPHS sites with the best potential can meet all of Saudi Arabia’s need for inter-seasonal energy storage.
  • •SPHS has a levelized cost of seasonal compensation (LCOS) as low as 14 USD/MWh in Saudi Arabia.

Abstract

In line with the broader ambitions of Vision 2030, Saudi Arabia aims to achieve greenhouse gas net zero emissions by 2060. At the heart of this ambition is decarbonizing the power generation sector with a commitment to 50 % of power generation capacity from renewables by 2030. Despite the affordability of renewable power generation options, long-term renewable energy storage solutions are still expensive. This paper investigates the role that seasonal pumped hydro storage (SPHS) can play in renewable energy storage and, hence, decarbonizing power generation in Saudi Arabia. SPHS is a practical approach for storing energy seasonaly in Saudi Arabia because the country has a large demand for seawater desalination, and by storing desalinated water, we indirectly store the energy required to desalinate the seawater, which is substatial. Ten proposed SPHS locations have been analyzed across the Kingdom. The study identified two attractive SPHS locations requiring an investment of around 16.5 billion USD to store 6.2 km3/yr for 15 to 22 USD/MWh of electricity and with a total seasonal compensation (SC, defined as the energy saving in the summer as a result of storing desalinated water in the winter) of around 69 TWh/y. Further work is needed to evaluate the impact of the share of renewable capacity on the feasibility of SPHS. This paper shows that SPHS can potentially contribute to the decarbonization of the power sector in Saudi Arabia and the balancing of the electricity grid as part of a full suite of energy storage options.

Introduction

Decarbonizing the economy is essential for countries to address climate change, protect the environment, foster sustainable development, and provide better conditions for future generations [1]. Even though countries in the Gulf Cooperation Council (GCC) have abundant oil and gas reserves, and their economies heavily rely on fossil fuel exports, they have committed through their nationally determined contributions (NDCs) to reduce CO2 emissions [2]. For instance, Saudi Arabia is committed to reaching GHG net zero by 2060 [3,4]. In doing so, the Kingdom’s ambition is to reduce emissions by 278 Mt CO2e/yr by 2030 (which is equivalent to a 42 % reduction based on 2016 GHG emissions), plant billions of trees as part of the Saudi Green Initiative [5], and diversify its economy away from fossil fuels with its Vision 2030 [6]. The power sector contributed to approximately 27 % of CO2 emissions in Saudi Arabia in 2016 [7] and so is an important sector to tackle if net zero emissions are to be reached by 2060. Improving energy efficiency, switching to renewable power generation, nuclear energy, and the addition of carbon capture and storage (CCS) to existing fossil fuel power plants all have important roles to play in decarbonizing the power sector. In Saudi Arabia, significant emphasis is placed on renewable energy sources with the ambition to reach 50 % of power capacity from renewable energy by 2030.

A limitation of renewable power generation is the fact it is intermittent. This can be overcome by incorporating several types of flexibility in operation, including supply and demand side management and storage. Energy storage provides a means to ensure the reliability of the power grid and balance peak demand, thus potentially contributing to reducing power generation costs. Combining energy storage with renewables provides flexibility and helps the fast transition required to 50 % renewables in the power sector by 2030 [2]. Battery and pumped hydro storage are the two main mature energy storage technologies. Battery storage is applicable for short-term storage (e.g., hourly and daily), and pumped hydro storage (PHS) applicable for both short and long-term storage (e.g., hourly, daily, weekly, monthly and seasonal) [[8], [9], [10]]. Most pumped storage stations can generate electricity continuously for between 6 and 24 h (Fig. 1), i.e., their discharge duration is 6–24 h. However, in the future, more and more PHS plants will likely be built to store variable energy at the weekly, monthly, seasonal and pluriannual scale. Seasonal pumped hydro storage (SPHS) reservoirs can also be used for other storage needs, in particular: i) water storage for drought alleviation, ii) flood control, iii) energy and water security in a changing climate, and iv) cold water storage from the winter to the summer. Storage reservoirs are critical for managing water supplies. To store a substantial volume of water, storage reservoirs require adequate geological formations that enable the reservoir level to change over a wide range of height. Storage reservoirs in flat terrain can impose significant land requirements and evaporation to store small volumes of water and energy. On the other hand, reservoirs with high dams and high level variations can store large volumes of water with small land requirements and little evaporation [11]. For example, if a reservoir has an average depth of 80 m and an evaporation rate of 4 m per year, around 5 % of the water will be lost due to evaporation, which is an acceptable loss for seasonal storage. Solutions for further reduction of evaporation rates are reviewed in Ref. [12]. The idea of using desalinated water with pumped storage has been applied elsewhere. For example, a forthcoming pumped storage initiative scheduled for inauguration by 2027 in the Canary Islands will not only serve as a platform for storing electricity for a duration of 16 h but will also play a vital role in seasonal desalinated water storage. This strategic utilization occurs during periods of heightened winds, allowing the stored water to be used during periods characterized by elevated energy demand and subdued wind power availability [[13], [14], [15]]. This approach is similar to a corresponding concept outlined for Cape Verde, wherein pumped storage reservoirs serve a dual role by facilitating cost-effective storage of both desalinated water and electricity, thus achieving efficient synergy [[16], [17], [18], [19]]. Furthermore, Tafech et al. (2016) presents an analogous proposition in the context of King Island, Australia, where they advocate prioritizing water storage over energy storage for desalination endeavors powered by renewable energy sources [20]. In a study conducted by Ganora et al., in 2019, a comprehensive cost analysis was undertaken to juxtapose battery-based storage with water reservoir storage concerning reverse osmosis (RO) desalination facilitated by solar photovoltaic (PV) systems [21].

Assessment of the potential of hydro storage in Saudi Arabia has been considered over the past decade by several authors. A paper by Kotiuga et al. (2013) identified three 1 GW locations for pumped hydro storage in Saudi Arabia [23]. The study considered new sites (utilizing seawater pumped to adjacent high grounds) and the redevelopment of existing freshwater storage dams. One of the options identified was desalinated water storage as a technically and economically viable option for developing coastal pumped storage. The study estimated capital costs of 1400 USD/kW. It was concluded that coastal development with desalination is the most attractive option economically, with payback periods of 11–12 years, and would be a viable hydro storage solution to consider in Saudi Arabia to reduce future thermal electricity generation. That pre-feasibility study considered three locations, including one desalination plant. It was emphasized that the sites identified still need to be ranked using Multi-Criteria Analysis (MCA) to include geological conditions, environmental and social impacts, capital cost and economic viability.

This paper focuses on the potential for seasonal hydro storage of desalinated water and investigates the role that this can play in meeting the high summer electricity and water demand in Saudi Arabia. In reality, despite the increasing capacity of renewables, the fuel mix in the power sector in the future will need to be flexible and will consist of renewables and gas with CCS as well as other low emissions generation technologies. A simple calculation for estimating the amount of energy savings in the summer as a result of desalinated water storage in the winter is presented. This paper provides the first step in assessing the potential that SPHS can play in decarbonizing the power sector toward achieving net zero targets. The paper is divided into five sections. Section 2 presents the methodologies applied in this paper. Section 3 presents the paper’s results. Section 4 discusses the role that seasonal pumped storage could play in decarbonizing the electricity sector. Finally, Section 5 presents key conclusions and recommendations.

Section snippets

Methodology

The methodological framework applied in the paper is presented in Fig. 2. Stage 1 consists of technological validation of the application of SPHS in decarbonizing countries with high summer demand for water and electricity. It presents the challenges related to energy and water demand in arid countries and investigates the impact of seawater temperature on reverse osmosis (RO) desalination. Possible arrangements for SPHS and the possibility of using reservoirs to store water from the winter to

Description of proposed SPHS plants

Table 1(in Appendix) summarizes the proposed SPHS plants in Saudi Arabia and their characteristics. The dam height and length, reservoir flooded area and volume are calculated using MERIT topographic data [25]. The methodology used to calculate the area and volume of the reservoirs is the same as the one presented in Ref. [32]. This selection looked for reservoirs that require short and high dams to result in cost-effective water storage with low evaporation rates. It also considered the

Discussion

As mentioned in the Methodology section, the cost of increasing the capacity of the desalination plants was not included in the CAPEX of the SPHS plants. This is because we assume a fixed seawater desalination cost of 1.1 USD/m3. To achieve this, the desalination plant capacity factor and the electricity cost used for seawater desalination must vary according to Fig. 10a. As the desalination plant will only operate during the winter, the capacity factor is assumed to be 45 %, while the

Conclusions

This paper explored the role of seasonal pumped hydro storage of desalinated water as one option for decarbonizing the power sector in Saudi Arabia. The paper considered 10 SPHS plants around the country with a total potential desalinated water storage capacity of 14.7 km3. The estimated seasonal energy compensation of the 10 proposed plants is around 130.6 TWh, and the total investment needed is 109 Bn USD. The lowest seasonal compensation CAPEX is 0.17 USD/kWh (882 times cheaper than

CRediT authorship contribution statement

Julian David Hunt: Conceptualization, Methodology, Visualization, Writing – original draft. Naser Odeh: Formal analysis, Methodology, Validation, Writing – original draft. Mohamed Hejazi: Formal analysis, Investigation, Project administration, Writing – review & editing. Puneet Kamboj:Data curation, Software. Sergey Osipov: Validation, Writing – review & editing. Yoshihide Wada: funding acquisition, Project administration, Resources, Supervision.

Declaration of competing interest

All authors have participated in conception and design, or analysis and interpretation of the data, or drafting the article, or revising it critically for important intellectual content, and approved of the final version.

This manuscript has not been submitted to, nor is under review at, another journal or other publishing venue.

The authors have no affiliation with any organization with a direct or indirect financial interest in the subject matter discussed in the manuscript.

The following

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  • https://www.sciencedirect.com/science/article/abs/pii/S1364032125000346