In recent years, photovoltaic thermal (PVT) systems have emerged as an imperative research area due to the escalating demand for energy worldwide. Phase change materials (PCMs) considered as the most ...suitable materials to harvest thermal energy effectively from renewable energy sources. As such, this paper reviews and explains the various aspects of PCM and Nano-Enhanced PCM (NEPCM) integrated PVT systems. The novel and recent developments in PVT research focusing on cooling and thermal energy storage with PCM and NEPCM and their applications in the heating ventilation and air-conditioning (HVAC), building integrated photovoltaic thermal systems (BIPVT), building integrated concentrated photovoltaic thermal systems (BICPVT) are critically summarized. In addition, this review also accentuates the different methods of preparing NEPCM and their thermo-physical properties at different operating temperatures for targeted applications. The present paper also highlights the use of nanofluid, PCM, and NEPCM in extracting the thermal energy from the commercially available for PVT system. In conclusion, this review recapitulates the effort taken by researchers around the world in enhancing the thermal performance system. It is also expected this review will provide greater insight to the new researchers in recognizing the fundamental science behind the development of thermal performance system and the mechanism to enhance further the overall performance of the PVT system.
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•Preparation of nanocomposites and methods are discussed.•PCM and NEPCM integrated PVT systems are extensively reviewed.•Numerical simulation and prediction models are discussed and summarized.•Application of thermal energy storage in the PVT system is well organized.•Valuation of social, economic and technical feasibility of the PVT system are discussed.
Thermal energy storage (TES), also known as heat storage systems, is a technology that accumulates energy when production exceeds demand so that the stored energy can be used later. The stored energy ...can be used at the user’s request for heating and cooling applications or for power generation. TES systems are commonly seen in buildings and industrial processes. On the other hand, conversion and storage, such as solar and wind energy, help to further increase the share of renewables in the energy mix. TES is becoming crucial for electricity storage in combination with solar power, whereby solar heat can be stored for electricity production when sunlight is absent. This is a Special Issue dedicated to recent advances in thermal energy storage and energy conversion technologies. All types of research approaches are compiled in this Special Issue: experimental, theoretical, computational, and their mixtures; papers are both of fundamental and applied nature, including industrial case studies.
•A validated TRNSYS model of Drake Landing Solar Community is developed using publicly available data.•Installation in UK locations is investigated using the model.•Solar fraction close to 80% is ...reached in one of the UK locations.•Levelised Cost of Energy is almost triple the value of incumbent systems.
Heat demand in buildings is responsible for around 40% of all energy use in middle to high latitude countries. The combination of district heating systems with solar thermal energy and seasonal thermal energy storage has successfully reduced the carbon intensity of heating in different countries, such as Denmark, Germany and Canada. The potentials of such systems to decarbonise the heat demand in the UK has also been highlighted in different reports. Nevertheless, bottom-up quantitative studies to support or dismissive these potentials are very limited. The quantification can be provided by simulating a solar district heating system using UK-specific inputs, such as heat demand and weather profiles. In this study, a validated simulation model is used to study the performance of solar district heating systems with seasonal thermal storage deployed in the UK. The case study is based on the Drake Landing Solar Community in Okotoks, Canada, which has a relatively high solar fraction. The results show that the system is technically feasible to be implemented in the UK but that it has lower technical performance. A systematic analysis of the influence of the main components on the system performance shows that not only the solar supply and heat demand need to be balanced but also that the long-term storage needs to be appropriately sized. The relatively lower solar fraction could be offset by installing more long-term storage and implementing the system to supply new-built houses with better energy performance rather than the current building stock of older homes. Financially, the system still needs to be supported by encouraging policies to make it competitive with incumbent technologies. The results and the validated model open the possibility to design bespoke solar district heating systems for the UK and other countries in middle to high latitudes.
The storage of heat in aquifers, also referred to as Aquifer Thermal Energy Storage (ATES), bears a high potential to bridge the seasonal gap between periods of highest thermal energy demand and ...supply. With storage temperatures higher than 50 °C, High-Temperature (HT) ATES is capable to facilitate the integration of (non-)renewable heat sources into complex energy systems. While the complexity of ATES technology is positively correlated to the required storage temperature, HT-ATES faces multidisciplinary challenges and risks impeding a rapid market uptake worldwide. Therefore, the aim of this study is to provide an overview and analysis of these risks of HT-ATES to facilitate global technology adoption. Risk are identified considering experiences of past HT-ATES projects and analyzed by ATES and geothermal energy experts. An online survey among 38 international experts revealed that technical risks are expected to be less critical than legal, social and organizational risks. This is confirmed by the lessons learned from past HT-ATES projects, where high heat recovery values were achieved, and technical feasibility was demonstrated. Although HT-ATES is less flexible than competing technologies such as pits or buffer tanks, the main problems encountered are attributed to a loss of the heat source and fluctuating or decreasing heating demands. Considering that a HT-ATES system has a lifetime of more than 30 years, it is crucial to develop energy concepts which take into account the conditions both for heat sources and heat sinks. Finally, a site-specific risk analysis for HT-ATES in the city of Hamburg revealed that some risks strongly depend on local boundary conditions. A project-specific risk management is therefore indispensable and should be addressed in future research and project developments.
Concentrated solar thermal power generation is becoming a very attractive renewable energy production system among all the different renewable options, as it has have a better potential for ...dispatchability. This dispatchability is inevitably linked with an efficient and cost-effective thermal storage system. Thus, of all components, thermal storage is a key one. However, it is also one of the less developed. Only a few plants in the world have tested high temperature thermal energy storage systems. In this paper, the different storage concepts are reviewed and classified. All materials considered in literature or plants are listed. And finally, modellization of such systems is reviewed.
In recent years the use of thermal energy storage with phase change materials has become a topic with a lot of interest within the research community, but also within architects and engineers. Many ...publications have appeared, and several books, but the information is disseminated and not very much organised. This paper shows a review of the latest publications on the use of phase change materials (PCM) in buildings. The paper compiles information about the requirements of the use of this technology, classification of materials, materials available and problems and possible solutions on the application of such materials in buildings.
The transition to intermittent renewable energies will necessitate the integration of storage. An interesting technology is the Carnot battery (CB), a novel power-to-heat-to-power system, capable of ...harnessing waste energy streams. While initial studies have indicated that, under ideal conditions, CB can be competitive with conventional technologies such as chemical batteries, their economic viability in real-world applications remains uncertain. To fill this gap, this work explores the techno-economic potential of electric booster-assisted CB integrated within data centres. Motivation for this case study is the recovery of waste heat, leading to an improved electrical storage efficiency. To maximise the energy self-sufficiency and the internal rate of return, we have applied multi-criteria optimisation to the system design, under three different thermal integration scenarios and for two sets of climatic conditions, using a thermodynamic model and time series from a real data centre. Our analyses suggest that current projections for electricity prices and CB costs yield payback periods exceeding a decade, but that these could fall below ten years if the CB capital costs were halved. Furthermore, it turns out that the choice of optimum charging system (i.e. right balance between heat pump and electrical heater) is contingent on the heat source temperature and availability. For higher temperatures (e.g. 60 °C), heat pumps emerge as the financially most attractive option, thanks to their superior coefficient of performance, whereas for lower temperatures (< 25 °C), resistive heaters are preferable. Results also show that when the aim is to increase the energy self-sufficiency, there exist an efficiency/charging capacity trade-off, which causes a dilemma for the system design. On the one hand, heat pumps are vital to increase the efficiency of the CB, but on the other hand, as the amount of thermal energy available at its source is limited by the data centre operations, electrical boosters are indispensable to increase the charging capacity. To soften this dilemma and enhance the techno-economic performance of thermally integrated CB, future research should explore more efficient booster configurations, such as dual heat source heat pumps.
•Thermal integration is not always beneficial due to limited waste heat availability.•The optimum booster configuration is contingent on the waste heat temperature.•Carnot batteries need better techno-economic performance to reach the market.•Higher efficiency, lower costs and new revenue streams are key to increase it.•Improved dual heat source heat pumps should be considered for efficiency gains.
Continuous use of fluctuating renewable energy resources is facilitated only by temporal storage solutions. For long-term and seasonal heat storage, many large-scale closed seasonal thermal energy ...storages (TES) have been built in the recent decades. Still there is no consistent picture available that contrasts the different technologies and summarises the major findings from the implemented storage facilities. This review reports the state-of-the art of these TES and offers future perspectives based on 31 locations in Europe with a total available storage volume of nearly 800,000 m³, corresponding to a capacity of 56,600 MWh in the case of optimised storage utilisation. Three construction types prove to be the most promising concepts: tank thermal energy storages, pit thermal energy storages, and water-gravel thermal energy storages. The characteristic technological elements such as filling, waterproofing, and thermal insulation are discussed in detail to highlight successes and failures, as well as to display the latest innovations and research trends. Novel materials substitute conventional, less efficient alternatives while innovative methodologies are shown to reduce the risk of failure and significantly improve storage performance. The main challenges on the way to global market maturity include avoidance of primarily defective waterproofing, mitigation of energy and exergy losses caused by long-term material fatigues, and reduction of the often substantial construction costs.
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•Review of variants for water-based closed seasonal thermal energy storage (TES).•Analysis of all construction elements of seasonal TES based on 31 systems in Europe.•Definition of barriers to overcome for market maturity of the selected technologies.•Revelation of innovative attempts to utilise overlooked potentials of presented TES.
•We demonstrate a general theoretical framework to design optimal cylindrical thermal storage systems.•Figures of merit developed in this study can be used to evaluate performance and design future ...thermal storage systems while accounting for the thermal load.•We identify optimums for the figures of merit and validate using experiment.
Phase change materials store thermal energy in the form of latent heat, and are often integrated with high thermal conductivity metals to make composites that have both high power density and large energy storage capacity. In this study, we provide a theoretical framework to design and optimize cylindrical composites with three figures of merit – minimization of temperature rise, maximization of the effective volumetric heat capacity and maximization of the effective heat capacity based on mass. We validate the figures of merit experimentally by 3D printing AlSi12 alloy and using octadecane as phase change material for a heat flux of 13.3 Wcm−2 and heating time of 10 s. The metal component volume fractions in the printed structures vary from 15% to 70% for straight fin structures, 10% to 70% for the SC lattice structures, and 20% to 70% for branching fin structures. When minimizing temperature rise, the optimum volume fraction of thermally conductive material is 0.5–0.7. When maximizing the effective volumetric heat capacity, the optimum volume fraction for the high conductivity material is 0.3–0.5. Finally, when maximizing the effective heat capacity by mass in cylindrical composites, the optimum volume fraction for the high conductivity material is 0.2–0.3. Importantly, the optimum values depend on the applied thermal load, which is not captured in existing figures of merit for thermal storage systems. The volumetric and mass based heat capacity values of the optimized composites identified in this study are at least 10x higher when compared to single component PCMs that are widely used for volumetric and mass based thermal storage systems. The figures of merit developed here can assess the performance of most composite PCM systems and help to design future cylindrical composites while accounting for the thermal loads specific to the thermal storage application.
The present paper is the first comprehensive review of the integration of phase change materials in building walls. Many considerations are discussed in this paper including physical considerations ...about building envelope and phase change material, phase change material integration and thermophysical property measurements and various experimental and numerical studies concerning the integration. Even if the integrated phase change material have a good potential for reducing energy demand, further investigations are needed to really assess their use.
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