Pumped Hydro Energy Storage System Research Articles

An innovative approach for optimal selection of pumped hydro energy storage systems to foster sustainable energy integration

The use of macro storage technologies has been widely studied in the literature with pumped hydro energy storage (PHES) emerging as the main option for its high stability and low environmental impact. Additionally, in recent years researchers have focused on combining a micro storage system with a photovoltaic and/or wind system that serves to increase self-consumption thereby reducing the load on the power grid. However, the selection of optimal micro system remains an open issue. This study thus proposes a methodology for selecting the optimal PHES system based on energy and economic analyses. The methodology was validated through a case study involving university buildings (University of Sannio) in Benevento - Italy, in which a photovoltaic system with peak power of about 142 kW was considered. The results obtained through a sensitivity analysis varying the total volume of reservoirs, showed an effective reduction in energy purchased from and sold to the grid. Subsequently the use of PHES system was compared with battery-based storage, commonly installed in building application. The energy produced from renewable sources delivered to the building increased by 25 % and 13 % for battery energy storage system (BESS) and PHES system, respectively. The economic analysis demonstrated the BESS to be most cost effective with a minimum levelized cost of storage of about 158 €/MWh, while the pumped hydro energy system showed attractive economic results only when the investment costs exclude the reservoirs (levelized cost of storage was 136.5 €/MWh).

A global atlas of pumped hydro systems that repurpose existing mining sites

Large amounts of energy storage are required to support high levels of solar and wind power. Pumped hydro energy storage comprises the majority of global energy storage for the electricity industry. A previous study identified 616,000 potential “Greenfield” closed-loop (off-river) pumped hydro sites around the world with combined storage of 23,000 Terawatt-hours (TWh). In this study, we identify 904 sites in mining areas (“Brownfield”) with combined potential storage of 30 TWh. A high spatial resolution global atlas of Brownfield closed-loop pumped hydro energy storage systems is available online. It was developed through Geographic Information System (GIS) analysis of a digital terrain model. The GIS algorithm identified mining pits, pit lakes, and tailings ponds within mining sites and located nearby reservoirs that could form a suitable pair. All Brownfield pumped hydro sites were assigned a cost class of A to E to allow comparison between sites on the global atlas. There are far fewer Brownfield than Greenfield options, with 77 countries found to contain eligible locations. Despite the smaller number of eligible locations, Brownfield sites typically have other advantages including existing transmission infrastructure, water pumping infrastructure, road access, social licence and reduced environmental impact for development on disturbed land.

Role of Renewables in Energy Storage Economic Viability in the Western Balkans

Given the growing shares of renewable energy sources in the grids, the interest in energy storage systems has increased. The role of pumped hydro energy storage systems as flexible solutions for managing peak and off-peak prices from nuclear and fossil power plants in previous systems is now revitalized in the liberalized systems, with a volatile generation of wind and solar energy. Thus, understanding of the patterns behind the economics of energy storage is crucial for the further integration of energy storage in the grids. In this paper, the factors that impact the economic viability of energy storage in electricity markets are analyzed. The method of approach used in this study considers the electricity market price distribution, full load hours, the total costs of energy storage, and linear regression analysis. Using revenues from arbitraging a 10-megawatt (MW) pumped hydro storage system in the Western Balkans, resulting from the electricity market price distribution and the analysis of the total costs of storage, an econometric model is created. This model shows the impacting factors of energy storage development in the context of the rising renewables sector. Research shows that the previous hypothesis about the integration of energy storage systems in proportion to the increase in shares of renewables in the grids is incorrect. There is a significant correlation between energy storage revenues, the dependent variable, and the independent variables of hydro, wind, and solar generation. The conducted analysis indicates the future arbitraging opportunities of pumped hydro energy storage systems and provides useful insights for energy storage investors and policymakers. During the transitional period, until the deployment of renewables changes the effects of fossil power plants, energy storage price arbitrage is profitable and desirable for 500, 1000, and 2000 full load hours in the Western Balkan region. Despite the need for flexibility, with more renewables in the grids, large-scale energy storage systems will not be economically viable in the long run because of “revenue cannibalization”.

Improving Grid Reliability in Jordan: A Proposal for Integrated Demand Side Management and Energy Storage Solutions

<p align="left">Increased use of Renewable energy systems (RES) in Jordan has posed a major challenge in maintaining our grid stability. Jordan a country that relies on imported natural resources to power up its grid is using more and more RES with an aim to cut back on costs and CO<sub>2</sub> emissions. This paper investigates the usage of Demand Side Management (DSM) and Energy Storage Systems (ESS) to improve the grid’s reliability. A survey was conducted to analyze the opinion and acceptance of the Jordanian population on the implementation of DSM in Jordan. (ESS) mentioned in detail in this paper are: Compressed Air Energy Storage Systems (CAES), Superconducting Magnetic Energy Storage Systems(SMES), and Pumped Hydro Energy Storage Systems(PHES). The survey conducted showed a general scope of willingness of participation from people with 71.7% out of the 385 individuals who participated in the survey saying that they will participate in such a program if implemented in Jordan.</p>

The impact of pumped hydro energy storage configurations on investment planning of hybrid systems with renewables

The pumped hydro energy storage (PHES) systems can be installed in various configurations depending on the specific geographical and hydrological conditions. Closed-loop PHES systems are off-stream and have no natural inflow to the system. However, open-loop systems are on-stream and have natural inflows to the upper and/or lower reservoirs. In this study, we develop two-stage stochastic programming models for various PHES configurations to investigate how the choice of PHES configuration impacts the sizing decisions and costs of a hybrid system that includes a renewable power generator co-operated with PHES. Our numerical results show that using a PHES facility instead of a conventional hydropower system reduces the expected system cost and mismatched demand significantly. Open-loop PHES facilities perform better than closed-loop PHES and seawater-PHES facilities, dramatically lowering the need for fossil fuels in demand fulfillment. The most cost-efficient PHES configuration is when there is natural inflow to the upper reservoir. Using solar energy instead of wind as the renewable source significantly increases the requirement for larger upper reservoirs in on-stream open-loop PHES facilities, while reducing the expected system cost for all configurations.

Pumps as turbines for pumped hydro energy storage systems - A small-size case study

Pumped Hydro Energy Storage (PHES) technology has been used since early 1890s and is, nowadays, a consolidated and commercially mature technology. PHES systems allow energy to be stored by pumping water from a lower-to a higher-level reservoir. Subsequently, this energy can be released through a turbine placed in a penstock, which connects the two reservoirs, to produce energy. Although these plants have historically been employed at large power scales (in the order of hundreds of MW), in recent years, micro- and small-scale plants are becoming more interesting, due to their possibility of being integrated with renewable energy systems (RES) used in autonomous island grids. Capital costs associated with hydraulic machines used in PHES systems represent the most critical economic factor, which can be mitigated by using commercial centrifugal pumps in reverse mode (Pumps as Turbines, PATs) in place of small hydro turbines. These expected economic benefits must be weighed in each specific case study, with some drawbacks related to the use of PATs, mainly associated to a lower round-trip efficiency with respect to specifically designed pumps and turbines.In this work, a small-scale PHES plant has been studied coupled to an existent photovoltaic system for the integration in the electric grid of a small island in Southern Italy. Two different PHES outlines have been compared based on techno-economic considerations. The former is a typical PHES system composed of both pumps and a turbine, while the latter uses only an array of parallel pumps which work also in reverse mode. The analysis demonstrates the feasibility of integrating a photovoltaic and PHES plant, which results in a lower cost of electricity production, while PHES performance in the PAT-based outline results penalized by the lower efficiency of PATs with respect to the hydraulic turbine.

Investigating the efficiency of a novel offshore pumped hydro energy storage system: Experimental study on a scale prototype

We introduce a novel offshore pumped hydro energy storage system, the Ocean Battery, which can be integrated with variable renewable energy sources to provide bulk energy storage. Its working principle is based on that of conventional pumped hydro storage with notable differences: the Ocean Battery is installed on the seabed, is powered by the hydrostatic pressure at the depth of deployment, and uses conditioned water as a working fluid within a closed hydraulic system to minimize the effects of corrosion and biofouling on the internal system. Herein we focus on the novel aspects of the Ocean Battery to investigate their effects on performance relative to that of conventional pumped hydro storage. Specifically, we present an analytical model that accounts for energy losses in the hydraulic system to predict pressures and flow velocities under different operating conditions and validate model predictions with measurements performed on an experimental small-scale prototype deployed in a relevant sea environment. Following validation, we use the model to estimate the round-trip efficiency of a scaled-up hydraulic system connected to pumps and turbines working at peak efficiencies, with the latter adopted from literature. The round-trip efficiency of such a scaled-up system is shown to be comparable to that of conventional pumped hydro storage.

Integrated Pumped Hydro Reverse Osmosis System optimization featuring surrogate model development in Reverse Osmosis modeling

The pressure head generated by the upper reservoir of a pumped hydro energy storage system can be sufficient for creating the pressure gradient required for a reverse osmosis desalination plant. Combined with the fact that many drought-stricken coastal areas have nearby mountains at the necessary elevation for these upper (mountaintop) reservoirs, a symbiotic relationship can be ascertained through the co-location of a pumped storage hydropower (PSH) system with a reverse osmosis (RO) desalination system. Merging PSH and RO into one Integrated Pumped Hydro Reverse Osmosis System (IPHROS) instead of implementing each individually could result in a number of benefits, including reduced capital investment, lower maintenance costs, and a natural mechanism for diluting the highly saline brine discharge generated from the RO process. This paper extends the work of Slocum et al. in 2016, who first introduced the concept of IPHROS, by optimizing the amount of seawater sent to and diverted from the upper reservoir for maximal energy recapture and freshwater production, respectively, while also seeking to maximize the RO system recovery ratio. For this multiobjective optimization, a new reverse osmosis model is created that utilizes a blend of empirical and fundamental equations based on the solution–diffusion model of membrane transport and boundary layer effects that naturally occur along reverse osmosis membranes. Additionally, surrogate models are developed to predict the permeate flowrate and fractional salt rejection rate for a Seamaxx™-440 RO element. Optimizing the presented IPHROS model reveals a 16% decrease in the break even time for IPHROS compared to PSH and RO being implemented individually, and that at the best design with regards to the energy, freshwater, and RO system recovery objectives, 79.5 million kWh of energy and 5.79 million cubic meters of fresh water can be delivered to a population, significant amounts for a population seeking to transition to a renewable energy-based grid and alleviate dire freshwater conditions. Enhanced modeling and optimization, as was initiated in this paper, will eventually aid in IPHROS’ large-scale adoption into energy and freshwater infrastructures.

Gravity-induced virtual clocking effect in large-capacity/low-head pumped hydro energy storage system with horizontal shaft

Significant gravity effects in a large-capacity/low-head pumped hydro energy storage system with horizontal shaft can destroy the axisymmetric inner flow structures in pump mode compared with its hydraulic model. For the stationary guide-vane region, this makes the inflow condition of each vane change with its circumferential installation position and thus causes a virtual clocking effect between the visible guide-vanes and the invisible gravity. The virtual clocking effect may change the hydraulic performance and induce instability risks, but its specific influence is still unclear. In this article, for a low-head pumped hydro energy storage prototype system with horizontal shaft, four virtual clocking schemes, namely the top guide-vane inlet edge and the gravity direction staggering 0/4, 1/4, 2/4 and 3/4 passage interval angle, were established, and a comparative investigation on hydraulic performance in the optimal pump mode was carried out. Firstly, the pressure polarization oscillation is observed in the impeller region under different schemes. The differences in the polarization degree do not exceed 1%, but the circumferential distributions of the peak-to-peak values of pressure fluctuations at the impeller outlet show a phase difference, which should be considered in the circumferential support structures. Secondly, the partial flow separation is observed in the guide-vane region under different schemes, and the flow deviation ratio between the left and right sides at the guide-vane outlet exhibits differences of up to 10%, which cannot be ignored for a huge system. The scheme with staggering 1/4 passage interval angle exhibits the least flow deviation ratio while the scheme with staggering 3/4 passage interval angle exhibits the greatest flow deviation ratio. Overall, to ensure the hydraulic stability of the large-capacity/low-head pumped hydro energy storage system with horizontal shaft, the virtual clocking scheme with staggering 1/4 passage interval angle is recommended for the energy engineering.

A novel energy storage and demand side management for entire green smart grid system for NEOM city in Saudi Arabia

AbstractHybrid renewable energy systems (HRES) are gaining high interest in supplying electric energy for remote communities. Energy storage systems (ESS) are utilized by green autonomous HRESs to accommodate the variability of renewable resources such as wind and solar energy systems. The lack of any traditional energy source is adding a great reliability challenge which should be compensated using expensive ESS. This challenge can be avoided by using a pumped hydro energy storage system (PHES) in harmony with batteries. The PHES is an excellent option to be used in NEOM city due to the perfect topographical characteristic of this site. The minimum cost of energy and the highest reliability is used as an objective for sizing the proposed entire green HRES. Using smart grid principles (SGP) and demand‐side management (DSM) in the design and operation stages will minimize system size and cost, which can result in a significant reduction in consumer bills. As a result, this paper introduces an innovative DSM based on a dynamic tariff. The suggested DSM technique was developed utilizing a unique fuzzy logic that takes into account the present and day‐ahead ESS situations to intelligently determine the ideal tariff for the lowest cost and maximum reliability of the HRES. This paper introduces a modified grey wolf optimization (MGWO) technique to shorten convergence time while preserving the best accuracy. The suggested MGWO is assessed against 10 swarm optimization techniques. The payback period of the project is 7 years. The findings acquired from this unique program demonstrated its superiority, with conversion times reduced by 22% to 80% when compared to previous optimization procedures. Furthermore, as compared to the flat rate pricing tariff, the usage of the dynamic tariff lowered the LCOE by 53%.

Partial flow separation in guide-vane region of large-capacity/low-head pumped hydro energy storage system with horizontal shaft

The hydraulic performance of a large-capacity/low-head pumped hydro energy storage system is usually assumed to be consistent with that of its hydraulic model system, that is, the energy parameters and the inner flow fields conform to the conventional similarity law. However, this expected hydraulic consistency may not be realized in actual engineering projects. In a prototype system with horizontal shaft, head change and vibration enhancement have been observed, but the origin of this inconsistency is still unclear. This article investigates the inner flow characteristics in the guide-vane region of a prototype system with horizontal shaft in the optimal pump mode. A new phenomenon, partial flow separation, is discovered. The most intuitive feature of partial flow separation is that large-scale separation vortices in the guide-vane region are concentrated in the top passages of the antigravity part, while the bottom passages demonstrate good through-flow capacity. This is significantly different from the axisymmetric inner flow structures in the model system. Further in-depth analysis shows that this new phenomenon directly stems from the constant circumferential imbalance of inflow attack angles, and is further attributed to the blade loading polarization in the impeller region under pronounced gravity effects. More importantly, partial flow separation can adversely affect energy performance and operation stability, including the aggravation of energy loss in the guide-vane region and severe flow deviation in the outflow passage. Particular attention should be paid in the future to the design and operation of large-capacity/low-head pumped hydro energy storage systems with horizontal shaft.

Stability and efficiency performance of pumped hydro energy storage system for higher flexibility

The pumped hydro energy storage station flexibility is perceived as a promising way for integrating more intermittent wind and solar energy into the power grid. However, this flexible operation mode challenges the stable and highly-efficient operation of the pump-turbine units. Therefore, this paper focuses on stability and efficiency performance of pumped hydro energy storage system (PHESS) under the various flexibility scenarios. First, a nonlinear model of PHESS coupling the hydraulic loss, mechanical loss and electrical loss of pump-turbine is established to study its stability and efficiency characteristics. Second, six flexibility scenarios including four transient processes and two steady processes are extracted based on the historical power output of a pump-turbine unit. Parameter responses indicate that the stability performance of PHESS got worse when the range of load-variation increased. Parameters response in the first 10s is steeper than that in the later 30s. Rotation speed and water head in part-load fluctuates periodically in a range of from −0.0024 to 0.01. In other words, 10 times more compared to the range response under the rated-load. Efficiency analysis suggests that the friction loss in scroll case is the dominated loss type in the transient processes, except for the FL condition. The responses of friction loss in straight pipe, impact loss in scroll case and volume loss are characterized by the corresponding discharge laws. The response curve of winding loss is similar with the response feature of rotation speed. This paper provides the stability and efficiency perspective when the operator exploits the flexibility potential of pumped hydro energy storage station.

Operational benefit of transforming cascade hydropower stations into pumped hydro energy storage systems

This study evaluates the potential benefit of retrofitting existing conventional cascade hydropower stations (CCHSs) with reversible turbines so as to operate them as pumped hydro energy storage (PHES) systems. We examine the energy generation and storage problem for a CCHS with two connected reservoirs that can be transformed into a PHES system in a market setting where the electricity price can be negative. We formulate this problem as a stochastic dynamic program (SDP) under uncertainty in the streamflow rate and electricity price. We analytically derive an upper bound on the profit improvement that can be obtained from the PHES transformation. We conduct numerical experiments with data-calibrated time series models and observe that the PHES system provides a greater benefit under more limited streamflow conditions or more frequently observed negative prices.

Load frequency control of a m ulti‐source multi‐area thermal system including biogas–solar thermal along with pumped hydro energy storage system using MBA ‐optimized 3DOF‐TIDN controller

In this article, load frequency control has been studied in an unequal three-area system under a deregulated environment. The area 1 comprises thermal and biodiesel units, area 2 has thermal and solar thermal power plant (STPP), and area 3 has thermal with biogas, wind turbine system (WTS) along with pumped hydro energy storage (PHES) units. A new secondary controller called three degree-of-freedom tilt-integral-derivative with filter (3DOF-TIDN) controller has been proposed, and its performance is compared with integral, tilt-integral-derivative with filter, and two degree-of-freedom-TIDN controllers. The investigation reveals 3DOF-TIDN controller provides better dynamic performance in terms of settling time, peak deviation, and magnitude of oscillations in both generating and motoring mode of PHES. The stability analysis has been performed for the proposed system using different secondary controller. The controller parameters are optimized using novel optimization technique called Mine Blasting Algorithm. In this study, real-time OPAL-RT digital simulator has been used to effectually execute the considered power system under various scenarios, and the obtained results are compared with MATLAB/Simulink results. Further, a comparative study of dynamic responses of the system has been carried out considering different mechanical energy storage devices like PHES, flywheel energy storage device, and compressed air energy storage, and the analysis shows that PHES gives superior performances than others. Robustness analysis of proposed controller gains is also conducted, considering different uncertainties.

Comparison of underwater with conventional pumped hydro-energy storage systems

The laws of fluid mechanics imply that modular offshore pumped hydro-energy storage systems like StEnSEA have no advantage over similar but much cheaper modular onshore systems.

Stability and Efficiency Performance of Pumped Hydro Energy Storage System for Higher Flexibility

Stability and Efficiency Performance of Pumped Hydro Energy Storage System for Higher Flexibility

Development and assessment of geothermal‐based underground pumped hydroenergy storage system integrated with organic Rankine cycle and district heating

This study develops a geothermal-based underground pumped hydroenergy storage system (UPHES) integrated with an organic Rankine cycle (ORC) and district heating. The ORC has been integrated into the system for contributing the power demand of the pump used during the charging period to pump the water from the underground to the upper reservoir. District heating has been performed by geothermal. Heat recovered from the ORC has been used for the preheating of water used in district heating before entering the upper reservoir. With this proposed integrated system, both the peak energy demand has been shifted to off-peak hours and district heating has been performed. An ORC has also been included in the system to contribute to the energy demand of the UPHES pump. In order to evaluate the system's performance, thermodynamic analysis has been performed base on energetic and exergetic efficiencies. In the base case study, 60 MWh of electricity has stored by the UPHES. Also, a 2.8 MW of heating demand of 100 houses has been met and a 1.7 MW of power has been generated by the ORC. The power of the UPHES pump has been calculated as 6.81 MW. The efficiency of the UPHES system is 73.34%. Overall energy and exergy efficiencies of the proposed integrated system have been calculated as 93.09% and 78.37%, respectively.

Mitigating Curtailment and Carbon Emissions through Load Migration between Data Centers

Summary As the share of variable renewable energy (VRE) grows in the electric grid, so does the risk of curtailment. While energy storage and hydrogen production have been proposed as solutions to the curtailment problem, they often pose technological and economic challenges. Here, we analyze the potential of data center load migration for mitigating curtailment and greenhouse gas (GHG) emissions. Using historical hourly electricity generation, curtailment, and typical data center server utilization data, we simulate the effect of migrating data center workloads from the fossil-fuel-heavy PJM to the renewable-heavy CAISO. The results show that load migration within the existing data center capacity during the curtailment hours in CAISO has the potential to reduce 113–239 KtCO2e per year of GHG emissions and absorb up to 62% of the total curtailment with negative abatement costs in 2019. Our study demonstrates the overlooked role that data centers can play for VRE integration and GHG emissions mitigation.

Modeling and Optimal Dimensioning of a Pumped Hydro Energy Storage System for the Exploitation of the Rejected Wind Energy in the Non-Interconnected Electrical Power System of the Crete Island, Greece

The aim of the present paper is to investigate the use of the site “Potamon” Dam in the Prefecture of Rethymnon, Crete island, Greece, as a “virtual” renewable electricity supply of a pumped storage plant (PSP) in order to save and exploit the maximum possible part of the rejected wind energy of the autonomous power system of the Crete island. Taking into account the annual time series of the rejected power of the Crete power grid, the present research work targets the optimal configuration of the proposed PSP power station, including the sizing of its individual components as well as the determination of the capacity it could guarantee in order to be economically viable. The rejected electric energy from the actually operating wind farm production, which is not possible to be absorbed by the grid of Crete due to its stable operation limitations, could be absorbed by the here proposed pump storage plant (PSP) and converted to hydraulic energy. This can be achieved by pumping the water from the lower reservoir, which is the existing reservoir of the site “Potamon” Dam, with a storage capacity of about 22.5 million m3, up to the upper reservoir, which must be constructed accordingly. For the proposed PSP’s optimal size determination, established financial indices are used as an evaluation criterion for an investment life cycle of 25 years. The proposed PSP optimization is based on the dynamic mathematical model of the simulation results of the PSP’s hourly operation when incorporated in the Crete power grid for a whole year, performed in the Matlab 2016b computational environment (The MathWorks, Inc., Natick, MA, USA). The results of this research demonstrate the PSP’s technical feasibility and determine the PSP’s optimal CAPEX and the PSP’s whole life-time financial indicators in order that the whole investment be viable. Furthermore, the appropriate selling prices of the electricity produced from the proposed PSP were determined to achieve the PSP’s financial viability. The results comprise the key elements to prove the necessity for the establishment a.s.a.p. of the appropriate legal framework in order to have authorization to exploit the rejected RES (renewable energy sources) electric energy or the major part of it through PSPs, in priority in both the non-interconnected, as well as the interconnected power systems.

Use of pumped hydro energy storage to complement wind energy: A case study

The dependency of RES on the weather and climate increased the interest on bulk energy storage methods to supply firm power. Pumped-hydro energy storage systems are a step ahead among other bulk energy storage methods because these are more efficient and they have higher storage capacities. The present study focuses on the use of grid connected wind-pumped hydro power station supply energy. A hybrid wind-pumped hydro storage system was designed and simulated using real data, and economic analysis was performed by calculating the basic pay-back period, the net present value and the internal rate of return. According to the results, it is found that the hybrid system is actively used and a part of the electricity is supplied from the wind-pumped hydro system. In addition, it was obtained that the pumped hydro storage systems are very suitable to be used together with wind power plants.