As mitigating climate change becomes an increasing worldwide focus, it is vital to explore a diverse range of technologies for reducing emissions. Heating and cooling make up a significant proportion ...of energy demand, both domestically and in industry. An effective method of reducing this energy demand is the storage and use of waste heat through the application of seasonal thermal energy storage, used to address the mismatch between supply and demand and greatly increasing the efficiency of renewable resources. Four methods of sensible heat storage; Tank, pit, borehole, and aquifer thermal energy storage are at the time of writing at a more advanced stage of development when compared with other methods of thermal storage and are already being implemented within energy systems. This review aims to identify some of the barriers to development currently facing these methods of seasonal thermal energy storage, and subsequently some of the work being undertaken to address these barriers in order to facilitate wider levels of adoption throughout energy systems.
•Review of aquifer, borehole, tank, and pit seasonal thermal energy storage.•Identifies barriers to the development of each technology.•Advantages and disadvantages of each type of STES.•Waste heat for seasonal thermal storage.•Storage temperatures, recovery efficiencies, and uses for each technology.
Heating and cooling both make up a large part of the total energy demand in the UK; long-term seasonal thermal energy storage (STES) can address temporal imbalances between varying supply and demand ...of heat to buildings and processes. Underground thermal energy storage (UTES) can play a role in energy decarbonisation by storing waste heat from space cooling, refrigeration, data processing, industrial processes, harvested summer solar thermal energy or even heat generated by surplus renewable (solar or wind) electricity with fluctuating supply. This paper evaluates a range of UTES technologies in a UK context and addresses geological suitability, storage capacity, low-carbon heat sources, surface heat sources and demand. This review concludes that there is a significant potential for UTES in the UK for both aquifer thermal energy storage (ATES) and borehole thermal energy storage (BTES) systems, coinciding with surface heat sources and demand. Therefore, uptake in UTES technology will help achieve net-zero carbon neutral targets by 2050.
There is also scope to utilise UTES technologies within existing subsurface infrastructure. There are 464 oil and gas wells which could be repurposed upon end of life using different UTES technologies. However, the potential for repurposing needs further evaluation; deep single well BTES systems will have a high surface area to volume ratio for storage, reducing the efficiency of such systems and the potential for ATES is limited by issues associated with contaminants. 23,000 abandoned mines underlay ∼25 % of the UKs population and could be utilised for minewater thermal energy storage (MTES).
•Review of UTES technology suitability for the UK.•First reporting of details of the Bodyheat BTES system.•Storage capacities for a typical UK BTES system have been calculated.•UTES has a high potential in decarbonising heat in the UK.
For solving the global problems of environmental pollution and energy shortages, thermal energy storage system that can improve the efficiency and utilization ratio of energy and solve the gap ...between energy demand and supply, has received more attention in recent years. More specifically, the latent thermal storage systems that use phase change materials (PCMs) as storage media, possessing high latent heat storage density and almost constant phase change temperature are the focus area in thermal energy storage. Previously, most of the researches on PCMs were organic, however in recent years, inorganic PCMs with large phase change temperature range have been paid more and more attention. In common inorganic PCMs, hydrated salts possess lower phase change temperature, applying in buildings, solar water heating systems, textiles, etc., and molten salts and metals have higher phase change temperature, applying in concentrated solar power (CSP) generation and industrial waste heat recovery etc. Each has its own outstanding merits, for example, inorganic salts possess a large latent heat storage capacity and metals possess an extremely high thermal conductivity. Therefore, this review focuses on the researches of inorganic PCMs in recent years and summaries their thermal properties, and introduces the integration of inorganic PCMs into heat exchangers and some applications of inorganic PCMs in main systems, seeking to give readers a relatively comprehensive awareness on them.
•Thermal properties of inorganic PCMs for thermal energy storage are analyzed.•Performances of heat exchangers integrated into inorganic PCMs are summarized.•Applications of inorganic PCMs in thermal energy storage systems are discussed.
Although solar energy is a clean and abundant resource, it has an unstable nature. It is demonstrated that latent thermal energy storage (LTES) systems have been an excellent way to utilize solar ...energy fully and widely. However, LTES has the problem of insufficient thermal conductivity. For this reason, it is inevitable to consider effective methods to intensify the thermal conductivity of LTES system. In the current study, experiment and numerical simulation are used to study the influence of non-uniform metal foams on heat transfer during phase transition. In this study, a horizontal shell-and-tube LTES test system is established. Moreover, the phase change melting rate of radially filled metal foams with different porosity gradients is compared. According to the numerical simulation results of phase interface, velocity field and temperature field, natural convection can accelerate the melting of PCM. However, there is no distinct effect on the solidification process. When the equivalent porosity is 0.94, the optimal combination (melting process is 0.84-0.92-0.99 and solidification process is 0.87-0.94-0.97), compared with the uniform structure, can shorten the total consumption time by 9.7% and 6.2%, respectively.
•The radial positive gradient structure accelerates the melting, but it has little effect on the solidification.•In the current study, the optimal melting/solidification combinations are 0.84-0.92-0.99 and 0.87–0.94-0.97, respectively.•The optimized design of metal foam gradient can reduce the cost of mobile thermal storage system.
Phase change materials (PCMs) based thermal energy storage (TES) has proved to have great potential in various energy-related applications. The high energy storage density enables TES to eliminate ...the imbalance between energy supply and demand. With the fast-rising demand for cold energy, cold thermal energy storage is becoming very appealing. In this paper, a review of TES for cold energy storage consisting of various liquid-solid low-temperature PCMs has been carried out. The classification of the PCMs is briefly introduced. Recent approaches to optimizing the properties of PCMs, particularly to remedy the poor thermal conductivity, leakage of liquid PCMs and the high degree of super-cooling, which limits the cold applications of TES, have also been reviewed. Methods for increasing the thermal performance including using composite PCMs and solid mesh are compared. Both modelling and experimental research on cold energy storage devices have been examined. The current cold energy storage applications including air conditioning, free cooling, etc. have been summarised. Compared with previous reviews, this work emphasises the cold energy storage applications instead of the materials aspects. The main challenges and approaches to cold thermal energy storage from the perspective of the engineering applications have been identified. Recommendations for future low charging rates and device design methodology are proposed.
•Recent approaches to optimizing PCMs properties have been reviewed.•Both modelling and experimental researches on cold energy storage devices have been examined.•Main challenges and approaches on cold thermal energy storage engineering applications have been identified.•Recommendations on low charging rate issue and device design methodology have been proposed.
A large community such as NEOM City which is supposed to be powered only by wind and solar renewable energy requires a significant amount of energy storage. Given the limitations of the current ...energy storage technologies, from the total storable energy to the time this energy is stored, from the cost to the technology readiness level, it is important to provide assessments of continuing evolving alternative technologies. The cases of electric (external) thermal energy storage (eTES), and hydrogen thermal energy storage (hTES), are here considered. eTES is based on warming up a molten salt by using an electric resistance. The molten salt is then used to warm up a power cycle fluid for dispatchable energy production running a thermal power cycle. eTES suffers from round trip efficiency below 50 % but may handle a larger amount of energy at a lower cost compared to lithium-ion battery energy storage. eTES may benefit from integration with concentrated solar power with (internal) thermal energy storage. hTES is then based on green hydrogen production by electrolyzers, storage of the hydrogen in tanks, and combustion of the hydrogen to warm up a power cycle fluid for dispatchable energy production running a thermal power cycle. Of cost more difficult to estimate, also depending on the deployment of electrolyzers and round trip efficiencies below 50 %, hTES has the benefit to permit the storage of any amount of energy even over long time scales such as those needed to compensate for seasonal variability. Before electrolyzers provide the due amount of green hydrogen, the combustion power plant can be run with natural gas, delivering if not zero CO2 emission, certainly the lowest life cycle CO2 emission for dispatchable electricity at present. Finally, eTES and hTES can be coupled with each other, and also integrated with waste-to-energy (WTE) systems, for a more comprehensive and sustainable approach based on common thermal power cycles.
Display omitted
•There is a growing demand for energy storage systems to manage non-dispatchable renewable energy.•Market-ready technologies are however still limited and not fully satisfactory.•Batteries, thermal energy storage, pumped hydro, and hydrogen are the best avenues.•Hydrogen thermal and electric thermal energy storage have benefits.•NEOM City will have to incorporate a mix of them to succeed in making a grid renewable energy-only.
•Addition of nanoparticles, with specific volume concentration, enhanced the thermal conductivity of base PCM.•Application of NePCMs in buildings reduced the energy consumption.•Use of NePCMs ...enhanced the thermal management of modern electronics.•The use of NePCMs in smart textiles improved the thermal stability and durability.
Phase change materials (PCMs) play a prime role in the development of sustainable energy and engineering systems for viable future, with their remarkable phase change properties. The heat energy absorbed and released by PCMs, over a specific temperature range, has become a prominent contender in many engineering applications that encompass thermal, solar, electronic, battery thermal management, textiles, heat pipes and food packaging. Apart from having high latent heat storage capacity, PCMs possess low thermal conductivity, which requires nanoparticles to be incorporated. Effectiveness of thermal conductivity of PCM can be increased by adding nanoparticles and resulting material is known as Nanoparticle-enhanced PCM (NePCM). This paper presents the comprehensive review on the preparation techniques as well as the applications of NePCMs in various fields. It is expected that this review will intend readers to provide some insight to explore the further applications and essential properties of NePCMs.
•Solar energy can be utilized in many industrial processes.•TES methods offer flexible solutions that render solar energy systems sustainable.•Integrating TES into industrial processes shall produce ...significant savings.•Using cost-effective and sustainable TES systems in SHIP is essential.
Industry is one of the leading energy consumers with a global share of 37%. Fossil fuels are used to meet more then 80% of this demand. The sun’s heat can be exploited in most industrial processes to replace fossil fuels. Integration of a thermal energy storage system is a requisite for sustainability in solar heat for industries. Currently there are only 741 solar heat industrial plants operating with an overall collector area of 662,648 m2 (567 MWth) that cover very small share of total global capacity. This is only the tip of the iceberg- there is a huge potential that is eager to be exploited. The challenges of increasing cost-effective solar heat applications are development of thermal energy storage systems and materials that can deliver this energy at feasible economic value. Sensible thermal energy storage, which is the oldest and most developed, has recently gained interest due to demand for increased sustainability in energy use.
This paper attempts to review these latest trends in sensible thermal energy storage systems and materials that are used in solar industrial applications with a special focus on sustainability. The aim is to provide information for further research and development that shall make solar heat a cost-effective method to meet the increasing energy demand of the industrial sector.
Medium and high-temperature latent heat thermal energy storage (LHTES) systems with high energy density can manage the intermittency of renewable energy sources. However, some significant challenges ...remain to be addressed. Hence, in this article, a pilot-scale medium-temperature cylindrical LHTES system loaded with 4130 kg phase change material (PCM) and equipped with heat exchanger tubes featuring spiral and H-shaped fins was constructed. The temperature evolution of PCM and various parameters containing charging/discharging time, instantaneous power, accumulated energy, and efficiency under the constant temperature and the step temperatures methods were investigated. The experimental results revealed that the melting of the upper PCM was accelerated by natural convection, whereas the melting of the bottom PCM was slower due to heat conduction. The heat exchange tubes with spiral fins demonstrated better performance during the charging process, whereas those with H-shaped fins performed better during the discharging process. In addition, the LHTES system achieved accumulative energy storage of 993.64 MJ and release of 659.58 MJ with a cycle efficiency of 66.38% under the constant temperature method. However, the accumulative energy storage and release under the step temperatures method were 966.2 and 664.86 MJ, respectively, with a cycle efficiency of 68.81%.
