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Electrical energy storage systems have a fundamental role in the energy transition process supporting the penetration of renewable energy sources into the energy mix. Compressed air energy storage (CAES) is a promising energy storage technology, mainly proposed for large-scale applications, that uses compressed air as an energy vector. Although the first document in literature on CAES appeared in 1976 and the first commercial plant was installed in 1978, this technology started to gain attention only in the decade 2000–2010, with remarkable scientific production output and the realization of other pre-commercial demonstrators and commercial plants. This study applies bibliometric techniques to draw a picture of the current status of the scientific progress and analyze the trend of the research on CAES and identify research gaps that can support researchers and manufacturers involved in this entering technology. Recent trends of research include aspects related to the off-design, the development of thermal energy storage for adiabatic CAES, and the integration of CAES with combined heating and cooling systems. [ABSTRACT FROM AUTHOR]

The increasing penetration of renewable energy has led electrical energy storage systems to have a key role in balancing and increasing the efficiency of the grid. Liquid air energy storage (LAES) is a promising technology, mainly proposed for large scale applications, which uses cryogen (liquid air) as energy vector. Compared to other similar large-scale technologies such as compressed air energy storage or pumped hydroelectric energy storage, the use of liquid air as a storage medium allows a high energy density to be reached and overcomes the problem related to geological constraints. Furthermore, when integrated with high-grade waste cold/waste heat resources such as the liquefied natural gas regasification process and hot combustion gases discharged to the atmosphere, LAES has the capacity to significantly increase the round-trip efficiency. Although the first document in the literature on the topic of LAES appeared in 1974, this technology has gained the attention of many researchers around the world only in recent years, leading to a rapid increase in a scientific production and the realization of two system prototype located in the United Kingdom (UK). This study aims to report the current status of the scientific progress through a bibliometric analysis, defining the hotspots and research trends of LAES technology. The results can be used by researchers and manufacturers involved in this entering technology to understand the state of art, the trend of scientific production, the current networks of worldwide institutions, and the authors connected through the LAES. Our conclusions report useful advice for the future research, highlighting the research trend and the current gaps. [ABSTRACT FROM AUTHOR]

• Comprehensive and systematic analysis of LAES is carried out. • Definition of LAES Performance maps for solving design (sizing) problem. • The combined effect of main operative parameters is included in each map. • High round trip efficiency could be achieved by internal re-use of waste cold flow. • Maps can serve as guidelines for LAES design under significant variation of the operative parameters. Liquid Air Energy Storage is one of the most promising novel energy storage concept that guarantees at the same time viable capital cost, high energy density and no geographical/geological constrains. Considering the complexity of the plant, composed by three different phases (charge, discharge and storage), thermodynamic modelling could be a challenging undertaking. Making use of the strong similitude with gas turbine technology, this paper aims to deliver new generalized performance maps for Liquid Air Energy Storage system. The performance maps, validated against the experimental results of Highview Power pilot plant, have been modelled by means of a comprehensive sensitivity analysis carried out considering three macro-scenarios imposing the storage pressures and the turbomachinery performance (design/off-design conditions). By means of the performance maps, the impact of the main LAES operative parameters, as well as the effect of the cold/warm thermal energy storage utilization factor, over the key performance indicators has been assessed and analysed. The analysis shows that at design condition the higher is the value of the high grade cold thermal energy storage utilization factor, the lower is the positive impact of charge pressure over the specific consumption. For off-design condition of the main turbomachinery, the negative effect of lower isentropic efficiency of the main turbomachinery on the round trip efficiency is amplified by the choice of the charge pressure. At high value of the warm energy storage utilization factor, this negative effect can be partially offset by the higher Turbine Inlet Temperature available for the expansion process of the discharge phase. [ABSTRACT FROM AUTHOR]

Abstract This paper aims to deliver new performance maps for "microgrid scale" Liquid Air Energy Storage system with a liquid air production of 1000 kg/h. By means of the performance maps, the impact of the main Liquid Air Energy Storage operative parameters, as well as the effect of the cold/warm thermal energy storage utilization factor, over the key performance indicators has been assessed and analyzed. The thermodynamics and sub-processes of the Liquid Air Energy Storage system are described in details and simulated by means of the software Aspen Hysys. Each performance map has been modelled by means of a sensitivity analysis carried out for the system operative parameters. Such a new methodology allows to select Liquid Air Energy Storage size and its related performance by means of a simple tool without the implementation of any complex numerical model. [ABSTRACT FROM AUTHOR]

Liquid air energy storage system (LAES) is a promising Carnot battery's configuration that includes thermal energy storage systems to thermally connect the charge and discharge phases. Among them, the high grade cold storage (HGCS) is of paramount importance due to the waste cold recovery of the liquid air regasification process. As of now, most of the literature studies on LAES designed to store the cryogenic energy using sensible heat material and only few works (including one recently carried out by the authors) proposed the implementation of phase change materials (PCMs) as alternative promising solution. This paper goes a step further numerically investigating a novel configuration of the HGCS system utilizing a cascade of multiple PCMs in place of the single PCM HGCS. By enhancing the thermal buffer effect typical of PCM media, the cascaded HGCS augments both the capacity ratio of the charge phase (0.87 vs 0.81) and the utilization factor of the discharge phase (0.87% vs 0.80%). As a result, the novel LAES system based on cascaded PCMs is capable to achieve a liquefaction specific consumption of 0.27 kWh e /kg LA , increasing thus the liquefaction performance of the single PCM HGCS by 6%. • A novel LAES configuration based on cascaded phase change materials is investigated. • The high grade cold storage is dynamically modelled to assess the LAES performance. • A novel double step approach to select the optimal PCMs combination is proposed. • A "thermal dead zone" criterion is identified for the selection of the cascaded PCMs. • The novel solution effectively improves the liquefaction specific consumption by 6%. [ABSTRACT FROM AUTHOR]

This work investigates the technical and economic feasibility of a Liquid Air Energy Storage (LAES) for building demand management applications. The thermodynamics and processes of the LAES configuration, as well as the description of the daily cooling energy demand profile, are described in details and the assumptions and constrains are pointed out. The quantitative analysis has been carried out for a daily cooling energy demand of an existing office building, located in Singapore, locality characterized by a typical hot climate. A thermodynamic analysis has been carried out for LAES configuration by means of the Aspen HYSYS® process simulation code. Under the technical assumptions formulated, LAES achieves an overall round trip efficiency of 45% with a specific consumption of 0.20 kWh/kgLA. The exergy analysis shows that LAES is characterized by an exergy efficiency of 84% and 67% for the liquefaction and the discharge processes, respectively; the compressor and the power turbines account for the highest exergy losses. Finally, the economic results show that under the actual condition of peak tariff and off-peak tariff in Singapore, the investment proposed is not convenient but in case of high values of LAES round trip efficiency and lower OPT the investment may be attractive. However, future works have to deal with the limitations introduced in the analysis, such as neglecting LAES operation costs, and the uncertainty related to capital costs figures. [ABSTRACT FROM AUTHOR]

Solar Hydrogen applications are getting more and more attention since competitiveness with conventional electric batteries is proven by several studies. Remote areas or weakly connected Islands are interesting context to apply such a comparison especially needing for seasonal storage due to the contemporary strong change of production due to solar radiation and consumption due to the tourism. Energy and economic analyses are needed tools for assessing the profitability of the solutions as well as sizing and operation of the energy system. Here a building complex of 5 buildings equipped with a total of 100 kWp of PV is investigated thanks to availability of recorded hourly datasets of loads and production. The storage facilities ranging from 500 to 2000 kWh were simulated over the year from an optimal dispatch perspective both for Hydrogen and Electric Battery options. Furthermore, the cost value for investment and operation of 2020, 2030 and 2040 were inserted as input to check the changes at increasing Technology Readiness Level of the mentioned storage medium. The analysis is carried out by means of the ©E-OPT platform based on a Mixed Integer Linear Programming solver. Finally, the yearly dispatch is compared at changes of the economic input for both Hydrogen and Battery solutions. • Hydrogen and battery solutions are compared in storing solar energy. • Solar Power To Gas and Electric Energy Storage applications to five buildings. • Seasonal change in production due to DNI and demand due to tourism. • CAPEX and OPEX of Hydrogen and Battery for 2020, 2030 and 2040. • Optimal dispatch of electricity leads to weekly or monthly storage, not seasonal. [ABSTRACT FROM AUTHOR]

Liquid air energy storage (LAES) represents one of the main alternatives to large-scale electrical energy storage solutions from medium to long-term period such as compressed air and pumped hydro energy storage. Indeed, characterized by one of the highest volumetric energy density (≈200 kWh/m3), LAES can overcome the geographical constraints from which the actual mature large-scale electrical energy storage technologies suffer from. LAES is based on the concept that air can be liquefied, stored, and used at a later time to produce electricity. Although the liquefaction of air has been studied for over a century, the first concept of using cryogenics as energy storage was proposed for the first time in 1977 and rediscovered only in recent times. Indeed, the need for alternative energy vectors in the energy system attracted many researchers to discover the potential of the use of cryogenic media. This has brought the realization of a first LAES pilot plant and a growing number of studies regarding LAES systems. The main drawback of this technology is the low round-trip efficiency that can be estimated around 50–60% for large-scale systems. However, due to its thermo-mechanical nature, LAES is a versatile energy storage concept that can be easily integrated with other thermal energy systems or energy sources in a wide range of applications. Most of the literature published is based on thermodynamic and economic analysis focusing on different LAES configurations. This paper provides a collection of the papers published on LAES and it classifies the various studies conducted in different categories. Future perspectives show that hybrid LAES solutions with efficient design of the waste energy recovery sections are the most promising configuration to enhance the techno-economic performance of the stand-alone system. • The state of the art of LAES is described. • A detailed review of the studies published is reported. • Future prospective can aim to develop LAES hybrid solutions with an efficient thermal energy recovery system. [ABSTRACT FROM AUTHOR]

Geographical Islands have been considered a challenge environment to test renewable energy integration strategies as well as cutting-edge technologies due to the alternation between actual grid-connected and island mode. This is due to the weak connection to the mainland and, subsequently, the Power Grid as well as the strong changes in seasonal energy demand leading to congestion and stability issues. Hydrogen technologies could be the pathway to mitigate the afore-mentioned issues providing bi-directional energy exchange as in the case of reversible solid oxide cells or interacting with other sectors such as transport by fuelling fuel cell vehicles by means of H2 produced by electrolysers. The scale of renewables locally installed plays a key role and this is why the amount of surface dedicated to solar energy exploitation as well as the number of buildings involved in the design are crucial. Therefore, in this paper a sensitivity analysis is carried out between 1 and 3 buildings, i.e. 20–100 kW of committed electrical power located in the Island as well as the surface dedicated to PV array for local production. The hydrogen energy system layouts of the simulated scenarios are optimized by the adoption of the ©E-OPT software platform based on a Mixed Integer Non Linear Programming solver. The scale affects the choice of the best hydrogen technology to integrate in order to increase the self-sufficiency of the compound and, consequently, the energy security of its supply. Furthermore, when coupled with CO2 emissions the performance vary with the final use of the stored hydrogen. • Geographical Islands are constrained environment for energy transition. • Solar Power To Gas is an interesting option for energy self-sufficiency. • Diversifying the building portfolio entails larger renewable integration. • Hydrogen offers the seasonal storage compared to batteries at same size. • Inefficiencies of Hydrogen are balanced by sector coupling opportunity. [ABSTRACT FROM AUTHOR]

Tetrabutylammonium bromide (TBAB) semi-clathrate hydrate possesses a unique clathrate structure for capturing and sequestering small-molecule gases, such as CH 4 , H 2 and, CO 2 and the advantage of phase change energy storage. Elucidating the diversified reactions and determining the optimal phase change characteristics of TBAB hydrate is crucial to discovering and overcoming specific limitations hindering the large-scale applications. In this study, in situ macroscopic visualization, three-dimensional reconstruction via X-ray Computed Tomography, and differential scanning calorimeter measurements were performed to discover, verify, and analyze the distinct characteristics of TBAB hydrate phase change, including phase separation, three-dimensional structure, and thermal effects. The optimal concentration of TBAB hydrate energy storage was found and verified experimentally for the first time. A peculiar liquid layer (liquid-liquid phase separation) caused by hydrate-solution phase separation was observed after multiple formation-dissociation cycles. The liquid layer separated a region that optimized the hydrate phase change. The solutions with different initial concentrations could evolve an optimized phase-change region of the same concentration (37 wt%) via multiple cycles. The region of the same concentration was shown to be the result of optimal aggregation of molecules. In proving the particularity of the concentration in the optimized region, TBAB hydrate dissociation exhibit thermal effects that can be easily ignored (TBAB molecules ionization and ionic bond synthesis), which affected the TBAB hydrate latent heat measurement. Finally, the optimal concentration of TBAB hydrate phase change was determined as 37 ± 1 wt%, and the characteristics of the concentration, including the volume fraction, complete conversion of water molecules and TBAB molecules, and latent heat, were confirmed by the liquid layer. The experimental results obtained for the first time in this study are important guidance for TBAB hydrate in the field of gas capture and energy storage. [Display omitted] • Solid-liquid phase separation leads to liquid-liquid phase separation. • Guest molecule optimum aggregation hypothesis of memory effect was proposed. • Changes in ionic bonds play an important role in TBAB hydrate phase change. • Hydrate volume fraction could be up 99% by XCT 3D reconstruction. • 37 wt% was considered to be the optimal concentration. [ABSTRACT FROM AUTHOR]

Highlights • LAES discharges as heat almost 70% of the total heat from the compression phase. • Waste heat is re-used in ORC and/or absorption chillers (ABS). • ORC integration improves the round trip efficiency by 20%. • ABS slightly reduces the specific consumption with almost no effect on round trip efficiency. • In trigenerative mode, LAES + ORC + ABS improves the round trip efficiency by 30%. Abstract In this paper, the potential of improving the round trip efficiency of Liquid Air Energy Storage was investigated through modelling and simulations using the numerical software EES-Engineering Equation Solver. Liquid Air Energy Storage is a novel energy storage concept whose performance is actually limited both by the inefficiencies of the charging (liquefaction cycle) and discharging (regasification and expansion) leading to a low value of round trip efficiency when compared to other energy storage solutions. In order to further improve the round trip efficiency, the opportunity to recover the waste heat released during the compression has been considered in this paper. Different integrated energy systems consisting Organic Rankine Cycle and/or Absorption Chiller were compared against a stand-alone Liquid Air Energy Storage used as a baseline. The integrated systems are compared in terms of different performance indices such as electric power output , ORC efficiency , round trip and overall efficiency of the stand-alone and integrated systems and utilization factor of the waste heat recovery systems. The results show that a tight integration between Liquid Air Energy Storage and Organic Rankine Cycle allows to significantly improve the round trip efficiency (up to 20%). Although the introduction of the absorption chiller decreases the specific consumption, the round trip efficiency is not improved due to the lower quality of waste heat available at the LAES discharge phase. The most remarkable results are achieved when the LAES is operated in trigenerative configuration: the introduction of both Organic Rankine Cycle and Absorption Chiller in combination with Liquid Air Energy Storage was found to improve the round trip efficiency by 30% due to a better utilization of the available waste heat. [ABSTRACT FROM AUTHOR]

This paper addresses the role of energy storage in cooling applications. Cold energy storage technologies addressed are: Li-Ion batteries (Li-Ion EES), sensible heat thermal energy storage (SHTES); phase change material (PCM TES), compressed air energy storage (CAES) and liquid air energy storage (LAES). Batteries and CAES are electrical storage systems which run the cooling systems; SHTES and PCM TES are thermal storage systems which directly store cold energy; LAES is assessed as a hybrid storage system which provides both electricity (for cooling) and cold energy. A hybrid quantitative-qualitative comparison is presented. Quantitative comparison was investigated for different sizes of daily cooling energy demand and three different tariff scenarios. A techno-economic analysis was performed to show the suitability of the different storage systems at different scales. Three parameters were used (Pay-back period, Savings-per-energy-unit and levelized-cost-of-energy) to analyze and compare the different scenarios. The qualitative analysis was based on five comparison criteria (Complexity, Technology Readiness Level, Sustainability, Flexibility and Safety). Results showed the importance of weighing the pros and cons of each technology to select a suitable cold energy storage system. Techno-economic analysis highlighted the fundamental role of tariff scenario: a greater difference between peak and off-peak electricity tariff leads to a shorter payback period of each technology. [ABSTRACT FROM AUTHOR]

[Display omitted] • A cryogenic thermal energy storage is investigated for a LAES system. • Phase change material as a novel cold storage medium is discussed. • Phase change material packed bed trough experimental facility constructed. • Thermal buffer phenomena in PCM thermal energy storage is highlighted as a key issue. • PCM integration decreases LAES specific consumption by 17% with a pay-back period inferior to 3 years. Electrical energy storage represents a necessary link between sustainability goals and the enhancement of intermittent renewable energy sources penetration in electricity grids. Liquid air energy storage (LAES) is a promising large scale thermo-mechanical energy storage system whose round trip efficiency is largely affected by the performance of the sub-thermal energy storages. The high grade cold storage (HGCS) is by far the most important due to the crucial thermodynamic recovery of the waste cold stream released by the liquid air regasification process. LAES pilot plant and pre-commercial demonstrator, as well as the vast majority of the theoretical and experimental analysis found in literature studies, currently design to store that exergetically valuable cold source in sensible heat (SH) thermal energy storage, economically efficient but low energy density solution. Conversely, phase change material (PCM) has the potential to store a larger amount of energy using the same amount of storage volume. The objective of the present work is to numerically and experimentally investigate the thermal behaviour of a novel cryogenic HGCS packed bed filled by PCM and determine how the novelty introduced affects the LAES thermodynamic and economic performance compared to the SH configuration. To this end, a simplified transient one-dimensional numerical model to simulate the charging and discharging phase of the HGCS system has been developed and successfully validated against experimental results provided by literature for SH medium and an experimental campaign carried out on a novel lab scale HGCS at TESLAB@NTU for PCM, representing a unicum in literature for both PCM and LAES applications. The numerical results have shown that the introduction of a PCM in the HGCS mitigates the thermocline effect shown in SH configuration ensuring: a) longer discharge phase by means of the thermal buffer phenomena triggered by the phase change process and b) lower specific consumption compared to SH configuration (0.272 vs 0.330 kWhe/kgLA) due to a lower time average outlet temperature of the heat transfer fluid during the HGCS discharge, corresponding to LAES charge phase. From an economic perspective, the decrease of the time average specific consumptions results in a notable payback period inferior to 3 years, making the economic investment considerably attractive. [ABSTRACT FROM AUTHOR]

• A MILP model to compute an energy hub's energy systems design is used. • The impacts of carbon pricing and natural gas prices fluctuations are analyzed. • High carbon pricing and TES can foster the deployment of distributed CCHP systems. • Drops in natural gas supply prices can compromise the effectiveness of carbon pricing. • CO 2 emissions are found to be related to the convenience of CCHP systems usage. Carbon pricing is being implemented by several governments to curb CO 2 emissions. This work studies its impact on distributed energy systems design which are powered by both renewable and fossil fuels. In particular, the analyses investigate a real case study situated in Singapore, characterized by cooling and electricity demands. The goal of the analyses is to determine whether carbon pricing does impact design choices in meeting the energy demands of a user located in a cooling dominated region, and secondly in assessing the effectiveness of carbon pricing as a CO 2 emissions mitigation policy. This is achieved by investigating the optimal design of the energy systems meeting the demands of the test case under different carbon pricing and primary energy supply costs assumptions. The results indicate that the optimal design under current conditions heavily relies on PV with more than 10 MWp worth of capacity and that an increasing carbon pricing would lead to a lower environmental footprint. But if the supply costs for natural gas were to lower, the optimal design would switch to relying on a combined cooling heat and power-based electricity generation system up to 3 MWe, increasing the primary energy consumptions regardless of the carbon pricing scheme in place. This would also happen even at significantly higher prices than the scheme under evaluation. [ABSTRACT FROM AUTHOR]

• Phase Change Materials as cold energy storage media to replace ice and water. • Thermal energy storage adequate technology for district cooling arrangements. • Master-planning and economic dispatch optimized on energy, cost and emissions. • District cooling equipped with phase change material storage technology. • Mixed Integer Quadratic Programming for master-planning and economic dispatch. The adoption of high-density phase change materials as cold thermal energy storage media have been considered as potential alternatives to water and ice. In this paper, the implementation of these media has been investigated in the context of district cooling in mixed-used building micro-grids whereby the cold thermal energy storage is retrofitted into an existing eco-building cluster. The techno-economic feasibility of implementing phase change materials, which includes eutectic salt, polyethylene glycol and paraffin as cold thermal energy storage media for district cooling, have been evaluated by computing the economic dispatch of a cooling bus network using mixed-integer quadratic programming. Furthermore, the impact of high-density storage media with a reduced footprint on the integration and design of cold thermal energy storage systems in district cooling has been included in the analysis. The capital expenditure of cold thermal energy storage systems, the land rental price for required occupancy and operating expenditure are used to determine the net present value after 20 years. Through peak shaving, optimally sized cold thermal energy storage has shown a better alternative substituting one of the two chillers. The smaller chiller (1200 kWc) is no longer required in the plant, giving significant savings in capital expenditure. The cost-benefit analysis also showed that only eutectic salt phase change materials are competitive with ice, with a net present value approaching 200,000 $ after 20 years. When phase change materials are adopted, especially if compared with water, the building operations and related costs are significantly less affected by large fluctuations in land rental price given its smaller footprint, thus posing significantly lower financial risks. [ABSTRACT FROM AUTHOR]

• Packed bed consisting of macro-encapsulated storage materials has large voids. • Using granular materials to fill the voids allows to increase storage efficiency. • Alumina particles are among the best for void reduction and storage efficiency. • Using micro-encapsulated n-decane yields the highest cyclic efficiency. • Parametric analysis is conducted to optimize design parameters of packed bed. In the paper, various granular materials as potential fillers for the void space in between macro-encapsulated phase change materials of packed bed thermal energy storage are studied. Once filled with suitable granular materials, void space of the packed bed storage, which is the main drawback of this type of storage can be significantly reduced while providing improved storage capacity per designed volume. Thus, four different materials, namely, quartzite pebbles, aluminum particles, alumina particles and micro-encapsulated n-decane are considered as potential granular fillers for packed beds. Their effect on the charge and discharge time, storage efficiency and overall storage capacity are evaluated using four parametric analyses: different macro-encapsulated phase change materials, encapsulation sizes, types of granular materials and heat transfer fluid flow rates. Among the granular materials, alumina particles ensured the highest overall increment on the amount of stored thermal energy due to their high density and heat capacity, while micro-encapsulated n-decane particles provided the highest overall enhancement on the cyclic efficiency of the packed bed storage. It was noticed that the granular materials operate at their highest capacity when combined with in-house-developed phase change materials with ultra-low phase change temperature. When coupled with other phase change materials with higher phase change temperature or latent heat capacity, the advantages of filling the void space with the granular materials diminished. Moreover, void space reduction with the granular materials helps maintain the storage efficiency while allowing increase in phase change material encapsulation size to reduce its overall cost. [ABSTRACT FROM AUTHOR]

• Validation and calibration of 1-D model were carried out for ice. • Thermal characterisations were completed for different phase change materials. • A good agreement between numerical and experimental results was achieved. • A valid and simple method to approximate behaviour of different PCMs. Latent heat thermal energy storage systems are gaining increasing attention due to their high energy density and ability to discharge at near isothermal temperatures. A good understanding of the thermal behaviour of phase change materials (PCMs) used in these systems and therefore, a methodology for the characterisation of the phase change behaviour of storage media during charge and discharge phases is important for an optimised storage design. In this work, an experimental rig in a cylindrical shape container was designed to obtain the thermal profiles of different category of sub-zero PCMs. The experimental measurement of deionised water (ice) was first used to calibrate and validate a numerical 1-D model. Three types of sub-zero PCMs were further tested including aqueous sodium chloride, aqueous ethylene glycol and decane. The numerical results showed that aqueous alcohol had the best agreement with the experiments. In the case of paraffin and aqueous sodium chloride, a discrepancy between numerical and experimental results was found. In particular, during the melting phase, the discrepancy was due to the effect of natural convection while, during the solidification phase, it was due to the effect of supercooling. This highlights the importance of correct estimation of those effects for an accurate prediction. However, due to its simplicity, the 1-D model can be considered a valid method to approximate behavior of the different PCM and to compare the thermal profiles of different materials. [ABSTRACT FROM AUTHOR]

Liquid Air Energy Storage (LAES) is a unique decoupled grid-scale energy storage system that stores energy through air liquefaction process. In order to further increase the utilization ratio of the available waste heat discharged by the air compression and not effectively recovered during the discharge phase, the authors have previously investigated the thermodynamic feasibility of different integrated LAES systems and promising results have been shown for the LAES coupled with Organic Rankine Cycle (integrated system LAORC). In order to assess the economic feasibility of the integrated system, this paper presents a techno-economic comparative analysis of the stand-alone LAES and the integrated system LAORC. The LAES systems have been designed by means of the quasi non-dimensional maps developed by the authors and the Levelised Cost of Storage (LCOS) has been employed to evaluate the economic viability of the investment by also comparing the LAES with Li-ion batteries. The results show that the stand-alone LAES system is generally cost-competitive with Li-ion batteries and even more in LAORC integrated system with the advantage of additional power output from the ORC. When LAES is operated in cogenerative configuration, the LAORC integrated system produces the most significant results decreasing the LCOS by 10%. • Levelised Cost of Storage is used to evaluate LAES with ORC. • The number of cycles and electricity price significantly affect economic feasibility. • ORC integration decreases LCOS by 10%. • LCOS for LAES with ORC is more competitive than Li-ion batteries. [ABSTRACT FROM AUTHOR]

• Local energy community modeled as a network of multi energy systems. • Primary Energy Saving as a metric for designing low carbon energy communities. • Investigation of low carbon scenarios with 10% and 20% of primary energy savings. • Thermal storage & district cooling allow to shave the cooling peak power installed. • Trigeneration and district cooling are key technologies to achieve low carbon goals. Design and planning of low carbon cities and districts must consider the synergies between all the energy networks available. Energy systems optimal design thus assumes a critical importance in determining both costs and environmental impact of operating such districts. This is particularly true following the concept of Local Energy Community, with a single entity representing both the demand and the manager of the energy generation assets. This paper proposes an innovative model for the optimal design of an energy community aiming at lowering its carbon footprint. The community is modeled as a network of spatially dislocated energy hubs, each with its own demand of electricity, heating and cooling energy. The model aims at defining the optimal mix of energy systems, thermal and electric energy storages and energy network infrastructures needed to satisfy the district's users energy demands. The model is validated using energy demand data from the Nanyang Technological University campus in Singapore by analyzing three scenarios. In the first one, the optimization goal is purely economic and it aims at minimizing the overall cost of operating the district. The second and third scenarios focus on reducing the carbon footprint of the district by imposing an additional constraint, which limits the overall primary energy consumption. In all the scenarios the algorithm chooses to partially or totally connect the five sites with a district cooling network and take advantage of cold thermal storage, proving their potential in hot climates. In the first scenario, the advantages of the district cooling solution are mainly related to the savings in the capital cost of electric chillers that partially offset the cost of the district cooling network; indeed, district cooling network allows the sites to share cooling power thus achieving a reduction in chillers total installed size of 33%. In the second scenario, in order to meet the target of 10% reduction of the overall primary energy, the optimal solution also requires the installation of a photovoltaic system. In the third scenario, imposing a 20% reduction of the overall primary energy, also a natural gas fed trigeneration plant comes into play. [ABSTRACT FROM AUTHOR]