Journal: Journal of Energy Storage

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Elsevier

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ISSN

2352-152X

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2018 - 201952020 - 20245
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Publications 1 - 10 of 10
  • Calculating the heat loss coefficients for performance modelling of seasonal ice thermal storage
    Item type: Journal Article
    Allan, James; Croce, Luca; Dott, Ralf; et al. (2022)
    Journal of Energy Storage
    This paper details the use of piece-wise linear regression and non-linear optimisation to determine the heat transfer properties of two ice thermal stores of different volumes (85 m3 and 11 m3). The available energy of each ice storage was determined by the fraction of ice stored in the vessel. The heat loss coefficient was determined using an optimisation algorithm. Using this approach it was possible to determine the heat loss coefficients occurring at different layers of the storage. Validation of the approach yielded a relative mean error of 5.4% and 3.8% for the 85 m3 and 11 m3 storage respectively. This approach is dependent on the measurement of temperature at different segments and the quantity of ice in the storage. It is believed that this approach is scalable and could contribute to a performance database that could provide inputs to energy modelling studies.
  • Power flow in heterogeneous battery systems
    Item type: Journal Article
    Bauer, Michaela; Mühlbauer, Markus; Bohlen, Oliver; et al. (2019)
    Journal of Energy Storage
    Control methods are important for stationary energy systems, especially for those based on so called second life batteries, due to asymmetrical system design and a mix of batteries from different capacities and aging levels. This study provides a theoretical analysis and simulation results of power flow and control methods in stationary energy storage systems. The theoretical part of this work develops a hierarchical control scheme comprising several levels and methods for computing the target variables of the control strategy based on optimisation. The simulation study focuses on the implementation of a stationary energy storage system, comprising four BMW i3 battery units connected to four DC/DC converters, and three DC/AC inverters. For this system four control strategies are developed in detail and compared. Three algorithms are based on feedback through a finite state machine, while the fourth uses linear programming and model predictive control techniques developed in this work. All methods are tested on two application profiles (artificial rectangle profile, frequency regulation profile) and the control schemes are compared in terms of performance, efficiency, and service life. The results suggest that optimisation based methods provide the flexibility to design a control strategy that weighs the three control objectives.
  • Pilot-scale demonstration of advanced adiabatic compressed air energy storage, Part 2: Tests with combined sensible/latent thermal-energy storage
    Item type: Journal Article
    Becattini, Viola; Geissbühler, Lukas; Zanganeh, Giw; et al. (2018)
    Journal of Energy Storage
    Experimental and numerical results from the world’s first pilot-scale advanced adiabatic compressed air energy storage plant with combined sensible/latent thermal-energy storage are presented. The combined thermal-energy storage was composed of sensible and latent units with maximum capacities of 11.6 MWhth and 171.5 kWhth, respectively. The latent thermal-energy storage consisted of a steel tank with 296 stainless-steel tubes encapsulating an Al–Cu–Si alloy as phase-change material. The combined thermal-energy storage was investigated using four charging/discharging cycles with durations of about 3 h each and air inflow temperatures of up to 566 °C. The experimental results showed that the latent thermal-energy storage reduced the drop in the air outflow temperature during discharging. Minor leaks of the phase-change material were traced to the welding seams in the encapsulation as well as to holes required to insert resistance temperature detectors. Analysis of the leaked phase-change material revealed degradation and/or phase separation, which were attributed to the initial off-eutectic composition of and impurities in the phase-change material and resulted in a reduced heat of fusion. Simulations predicted the performance of the combined thermal-energy storage with good overall accuracy. Discrepancies were put down to changes in the thermophysical properties.
  • Considerations on the existing capacity and future potential for energy storage in the European Union's hydropower reservoirs and pumped-storage hydropower
    Item type: Journal Article
    Quaranta, Emanuele; Boes, Robert; Hunt, Julian David; et al. (2024)
    Journal of Energy Storage
    Water storage and water reservoirs are key to the Water-Energy-Food-Ecosystem (WEFE) nexus, especially when they store water for hydropower. However, there is not a uniform view on existing energy storage capacity and on the potential for future deployment of pumped-storage hydropower (PSH) and conventional reservoir storage hydropower (RSHP) across energy system models. Furthermore, knowledge of energy storage capacity in PSH and RSHP remains rather fragmented and expressed in different metrics that need to be interpreted and reconciled. This paper addresses such barriers by systematically reviewing the literature and datasets (which are commonly used for regional assessments and modelling) related to the energy storage capacity, hydropower and reservoirs, reconciling various metrics and providing an internally consistent dataset related to the current energy storage capacity and potential for capacity expansion, with focus on the European Union (EU). The estimated theoretical storage capacity in this paper (approximated by the product of storage volume and head) of the aggregated EU's RSHP and PSH is 62 TWh (6.3 TWh + 55.7 TWh from PSH and RSHP, respectively). The technical storage capacity (i.e., the theoretical with some reduction correction factors) is 2.3 TWh for PSH and 24.9 TWh for RSHP. The reported PSH one is 1.3 TWh by IHA, and 71 TWh by ENTSO-E for PSH + RSHP (the latter including cascade effects for Sweden), while the actually usable one for PSH may be in the range 500–600 GWh. According to the literature review, new PSH and RSHP developments are possible (the available theoretical potential is 35–230 TWh from closed-loop PSH, +50 TWh from open-loop PSH neglecting the cascade effect, and +2.6 TWh from new reservoirs in valleys with melting glaciers), but the most suitable sites have already been exploited in the EU, and the remaining ones may be less economic. Hence interconnecting existing reservoirs, exploiting abandoned mines (+141 GWh and +3 TWh, respectively, technical potential), modernisation and increasing storage capacity of existing PSH could be much more cost-effective.
  • Pilot-scale demonstration of advanced adiabatic compressed air energy storage, Part 1: Plant description and tests with sensible thermal-energy storage
    Item type: Journal Article
    Geissbühler, Lukas; Becattini, Viola; Zanganeh, Giw; et al. (2018)
    Journal of Energy Storage
    Experimental and numerical results from the world's first advanced adiabatic compressed air energy storage (AA-CAES) pilot-scale plant are presented. The plant was built in an unused tunnel with a diameter of 4.9 m in which two concrete plugs delimited a mostly unlined cavern of 120 m length. The sensible thermal-energy storage (TES) with a capacity of 12 MWhth was placed inside the cavern. The pilot plant was operated with charging/discharging cycles of various durations, air temperatures of up to 550 °C, and maximum cavern gauge pressures of 7 bar. Higher pressures could not be reached because of leaks that were traced mainly to the concrete plugs. Simulations using a coupled model of the TES and cavern showed good agreement with measurements. Cycle energy efficiencies of the TES were determined to lie between 76% and 90%. The estimated round-trip efficiency of the pilot plant was based on the measured TES performance and estimated performances of the other components, yielding values of 63–74%, which compares favorably with the usually quoted values of 60–75% for prospective AA-CAES plants.
  • Hybrid hydropeaking mitigation at storage hydropower plants combining compensation basins with battery energy storage systems (BESS)
    Item type: Journal Article
    Höfkes, Gereon F.; Evers, Frederic M.; Hohermuth, Benjamin; et al. (2024)
    Journal of Energy Storage
    Storage hydropower has the ability of flexibly generating electricity to match fluctuating power demand. However, rapid changes of water discharge in river reaches downstream of storage hydropower plants, referred to as hydropeaking, result from this intermittent production mode and may have potentially damaging effects on a river's ecosystem. The construction of compensation basins usually embedded along the waterway between the powerhouse and the receiving water represents the state-of-the-art for hydropeaking mitigation. In recent studies, the application of battery energy storage systems (BESS) as an alternative mitigation option has been proposed. Instead of buffering the turbine discharge in a basin, electrical energy is stored in and retrieved from a BESS to meet short-term demand requirements, while the hydraulic machinery is ramping up and down according to environmental discharge constraints. The technical and economic feasibility of BESS compared to compensation basins is evaluated based on a newly introduced first-order assessment approach. If environmental discharge constraints are to be strictly followed, the exclusive application of BESS is deemed not feasible, due to the limited operation range of Francis and – to a lesser extent – Pelton turbines, especially for low partial loads. Therefore, hybrid systems combining a BESS with a smaller compensation basin are investigated as existing research focused either on a basin- or a BESS-only approach. Based on production time series of three case study hydropower plants, the sizes of basins and BESS are estimated. Basin sizes can be reduced with a hybrid system by 51% to 96% compared to a basin-only approach, with BESS energy capacities ranging approximately from 10 to 100 MWh. The cost efficiency of hybrid systems is strongly influenced by two factors, namely the future battery costs as well as the overall unit costs for the compensating basin. While the former are subject to considerable uncertainty especially as BESS reach their end-of-life much earlier compared to hydraulic structures and therefore require regular replacements after 10 to 15 years, the latter are highly site-specific as they include land availability and acquisition costs. The case studies show that a hybrid system of basin and BESS may represent a cost-competitive alternative to a basin-only approach when the latter's investment costs are high or space is limited, even if additional revenue streams including ancillary services and energy arbitrage are not considered.
  • Analysing the regional potential and social acceptance of power-to-gas in the context of decentralized co-generation in Baden-Württemberg
    Item type: Journal Article
    König, Sebastian; Bchini, Quentin; McKenna, Russell; et al. (2018)
    Journal of Energy Storage
    Sustainable but fluctuating renewable energy sources require new storage technologies to ensure a stable energy supply. One long-term storage technology that exploits the existing gas infrastructure is Power-to-Gas (PtG). The techno-economic and social challenges of this technology have been addressed in a large, interdisciplinary research project in Baden-Württemberg (south west Germany), whose results are presented in this paper.
  • Dynamic melting of encapsulated PCM in various geometries driven by natural convection of surrounding air: A modelling-based parametric study
    Item type: Journal Article
    Zhang, Yuxuan; Bozorg, Mehdi Vahabzadeh; Torres, Juan F.; et al. (2022)
    Journal of Energy Storage
    Encapsulated phase change material (PCM) has a great potential to reduce the fluctuation of indoor air temperature and subsequent building energy consumption through ceiling applications in air-conditioning systems. However, the effects of capsule geometry on the dynamic melting performance remain unknown when the melting is driven by natural convection. In this work, we modelled the melting behavior of PCM encapsulated in six different capsule shapes subject to natural convection of surrounding air, which was validated by our measurement results. The model considers the conjugate heat transfer through the surrounding air, capsule shell and PCM, enabling the prediction of a three-stage dynamic melting process. The melting process of the encapsulated PCM were further studied for varying inclination angles (with respect to the vertical axis), temperature differences (between the surrounding air and PCM), and capsule sizes. The results show that the capsule geometry plays a dramatic role in the time of phase change. At the ambient temperature of 22°C, the short cylindrical capsule with a horizontal axis takes the longest time to complete phase change (162 min), whilst the pyramidal capsule with a horizontal base takes the shortest time (120 min). We also quantified the heat transfer between capsules and surrounding air for varying temperature difference and capsule size, and found that the pyramidal and tetrahedral capsules with a horizontal base melt faster than capsules of other shapes due to the higher heat transfer rate caused by larger surface area. For cases with a medium capsule size and low temperature difference, early termination of melting at 80% liquid fraction is recommended since more than 30% of melting time can be saved with only 20% reduction in cold storage capacity. This work provides a validated model that is able to predict the dynamic melting process of PCM of different geometries, which will enable informed design of PCM panels for improving thermal management and comfort in buildings.
  • Simultaneous sizing and scheduling optimization for farmhouse PV-battery systems with a multi-structured power system model
    Item type: Journal Article
    Zhi, Yuan; Gao, Ding; Wei, Guanqiong; et al. (2024)
    Journal of Energy Storage
    Increasing the proportion of photovoltaic (PV) power in energy supplies is effective in decarbonizing energy use in buildings. Optimization model analysis is essential for the design and operation of PV-battery systems. The optimization models developed in previous studies are mainly suitable for one specific scenario, and there is a lack of research on the suitability of different types of PV-battery systems applying in various scenarios. This study proposes a multi-structured power system optimization model for various rural PV-battery systems, compares the optimal sizing and performance of three commonly used PV-battery systems, and quantifies the impacts of system capacity on system performance. The optimization model was constructed using the improved simulated annealing algorithm with the self-consumption rate and economy as the objective functions, while the system node power balance was the constraint. The sensitivity analysis shows that increasing the PV capacity will reduce the PV self-consumption rate and payback period of the system while increasing the battery capacity will increase the PV self-consumption rate and payback period of the system. For every 1 kW·h increase in battery capacity, the payback period of the system increases by 0.5 years. The spatial optimization model simulates the operation strategies of typical farm houses in different climate zones in China, and obtains payback periods for rural PV-battery systems in different regions of China. This study provides a theoretical basis for capacity sizing for rural PV-battery systems. The payback period of farmhouse PV systems in Gansu, Ningxia, Qinghai, Tibet, and Yunnan regions is <7 years, while the payback period of farmhouse PV systems in Guangdong, Guangxi, Jiangsu, Zhejiang, and Chongqing regions is higher than 10 years.
  • A comparison of system architectures for high-voltage electric vehicle batteries in stationary applications
    Item type: Journal Article
    Bauer, Michaela; Wiesmeier, Julian; Lygeros, John (2018)
    Journal of Energy Storage
    An increasing global interest in clean energy alternatives requires new concepts for local storage of electricity. This leads to new research demand regarding suitable system architectures based on high-voltage batteries from electric vehicles. In this study, a new method for evaluating stationary system architectures is described. The assessment focuses on the system efficiency of different architectures. A sensitivity analysis is included to show further distinctions in criteria such as volume, weight and cost. Three system topologies for the use of new and second-hand batteries extracted from electric vehicles in stationary applications are presented. All components need to be able to operate in a bidirectional mode — the ability to absorb and release electricity from and into the grid. The first two topologies include one battery connected to the grid either with a DC/DC converter and a DC/AC inverter or with a DC/AC inverter and a transformer. The third topology involves the connection of two batteries in series with a DC/AC inverter, providing better characteristics in terms of the required power electronic components. The results show differences between one to two percentage points in efficiency. Moreover, the influence of parallelisation and various power distributions delivers close to five percentage points higher efficiency for the first topology with a DC/DC converter. Combined with the outcome of the sensitivity analysis, the topology with the DC/DC converter connected to the DC/AC inverter exhibits the best performance in the overall evaluation criteria.
Publications 1 - 10 of 10