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Summary: Integration of information technology with multi‐carrier energy systems has paved the way for smart energy hubs (SEHs). Such energy hubs require stochastic modeling of intermittent renewable energy resources (RERs) and fluctuating demands to realize their optimal operation. Many excellent works are available related to their optimization but none of the existing works presents a comprehensive model which not only incorporates the stochastic nature of RERs and demands but also taps demand response potential in the presence of system storages. To fill this gap, this paper proposes a comprehensive model for an SEH which incorporates the stochastic nature of electrical, heating, and cooling demands in the presence of RERs, batteries, and thermal storages. In addition, optimal shifting of electrical, heating, and cooling loads are performed to further reduce the operational cost of SEH considering a price‐based demand response program (DRP). The cost minimization objective is formulated as a mixed‐integer linear programming (MILP) optimization problem. Five different cases are analyzed considering the inclusion and exclusion of storage and RERs with different percentages of shiftable loads for DRP. The proposed complex model is solved using CPLEX in GAMS environment. With RERs, cost reductions of 5.25% and 18.96% are observed in the operational cost of SEH without tapping demand response (DR) potential. When 10% and 20% loads are deemed to be shiftable for DR, operational costs reduce to 20.15% and 21.43% respectively with RERs and energy storages. Results of the study can support energy managers in the optimal operation of multi‐carrier energy systems. [ABSTRACT FROM AUTHOR]

Summary: Ice thermal energy storage (ITES) is a significant option for shifting cooling load from peak hours to off‐peak hours in order to reduce the cooling cost and equipment capacity. Encapsulated ITES system is one of the most preferred types of ITES systems, because it is easier to apply and has lower initial cost than other types of ITES systems. Capsule geometries have great impact on the thermal performance of the encapsulated ITES system. Spherical capsules are widely used in the application because they provide better thermal performance due to the ratio of its volume to its surface area. Also, modified capsule geometries are used for increasing the thermal performance of the ITES system. This paper focuses on a numerical study in order to determine the effect of the geometrically modified spherical capsule on the thermal performance during the discharging period. Seven geometrically modified spherical capsules were investigated and compared with the ordinary spherical capsule. The FLUENT 17.1 code was used for numerical analyses. At the end of the study, it was found that geometrically modified capsules provided higher thermal performance than an ordinary spherical capsule in the equal capsule volume. Capsule D provided the longest discharging period of 2118 seconds, when VHTF, in = 0.001 m/s and THTF,in = 275.5 K. The lowest discharging time of 464 seconds was obtained with Capsule A, when VHTF, in = 0.01 m/s and THTF, in = 283 K. Among the studied modified capsules, Capsule F performed the worst thermal performance. Energy efficiency values were high, and they did not give comparable difference between the capsule models and working conditions. While all exergy values were 98.50% and higher, exergy efficiency values changed between 85.12% and 51.91%. Exergetically, Capsule D provided the best thermal performance during the discharging period. [ABSTRACT FROM AUTHOR]

Summary: This article studies a new architecture of a thermosyphon loop and its capacity to cool data center considering the climate of several cities in France. A parametric experimental study is carried out to show the effect of the refrigerant fill ratio, the input heat load, and the outside temperature. The optimal fill ratio is 16% and the maximum cooling capacity is 1900 W when the data center outside temperature is 20°C. A hydraulic and thermal analytical model is developed to simulate the thermosyphon loop, and it is validated with the experimental results. The cooling load of a typical data center with ten racks, each one dissipates 4.5 kW, is simulated by TRNSYS software for the eight chosen cities in France. The annual performance shows that the percentage of undissipated heat is 13.4% in Marseille that has the highest annual average outside temperature and 2.7% in Caen that has the lowest summer average outside temperature of the data center. The particularity of this work is that it gives the annual performance of a new architecture of a thermosyphon loop in several cities of France with different climates and without electricity consumption. [ABSTRACT FROM AUTHOR]

Summary: The separation of carbon dioxide (CO2) from the flue gas is a challenging one in terms of the energy penalty. The development of a cryogenic or low‐temperature CO2 separation method helps to overcome the energy penalty associated with CO2 separation. In this study, a preliminary investigation is carried out in a theoretically modified Linde process which can be used for CO2 separation from a gas mixture containing CO2 and N2. A cryogenic cooling process is also studied for CO2 separation of the same quality of the gas mixture. The compression work and cooling loads in each case are analyzed using Aspen Plus software. The effect of CO2 volume in the mixture, compressor efficiency, and compressor discharge pressure on the energy consumption is studied for both the theoretically modified Linde and the cryogenic cooling processes, and the results are compared between them. The results indicated in the CO2 separation by the cooling process are better than the modified Linde process. The energy penalty shows for 20% CO2 composition of separation by the cooling process with the single‐stage compression is lower by around 123.9% and 128.8% in terms of compression work and compressor cooling load, respectively, than those of the modified Linde process working in a single‐stage compression. The separation by the cooling process refrigeration effect is 15.9% more than in the modified Linde process. [ABSTRACT FROM AUTHOR]

Summary: The usage of waste materials as building materials can be an important method to reduce energy consumption and decrease natural resource usage in the construction industry. In this work, phase change materials (PCMs) were incorporated with industrial by‐product materials as an aggregate to produce mortars, which can improve the energy efficiency and improve the environment of buildings. Bottom ash (BA), a by‐product from coal‐fired power plants, was directly impregnated into paraffin, a PCM, to produce a heat storage aggregate (HSA). The raw materials of the HSA production were characterized by X‐ray diffraction, scanning electron microscope, and differential scanning calorimeter. The mortar mixes had a water to cement ratio of 1:2 and a sand to cement ratio of 2.5:1. Six mixtures were prepared with different HSA amounts of 0%, 10%, 20%, 30%, 40%, and 50% by volume. The compressive strength, density, and thermal properties of the mortars were investigated. The results and analyses showed that the compressive strength and density of the mortars decreased with increasing HSA amounts. The thermal conductivity of HSA mortars slightly decreased for increasing levels of HSA. In addition, HSA mortars showed a significant increase in time lags when the HSA content increased, up to approximately 165% to 197% higher than that of the control mortars. HSA levels in mortars can play an important role in improving the heat conductance into buildings. [ABSTRACT FROM AUTHOR]

The performance optimization of an endoreversible air refrigerator with variable-temperature heat reservoirs is carried out by taking the cooling load density, i.e. the ratio of cooling load density to the maximum specific volume in the cycle, as the optimization objective in this paper. The analytical relations of cooling load, cooling load density and coefficient of performance are derived with the heat resistance losses in the hot- and cold-side heat exchangers. The maximum cooling load density optimization is performed by searching the optimum pressure ratio of the compressor, the optimum distribution of heat conductance of the hot- and cold-side heat exchangers for the fixed total heat exchanger inventory, and the heat capacity rate matching between the working fluid and the heat reservoirs. The influences of some design parameters, including the heat capacitance rate of the working fluid, the inlet temperature ratio of heat reservoirs and the total heat exchanger inventory on the maximum cooling load density, the optimum heat conductance distribution, the optimum pressure ratio and the heat capacity rate matching between the working fluid and the heat reservoirs are provided by numerical examples. The refrigeration plant design with optimization leads to a smaller size including the compressor, expander and the hot- and cold-side heat exchangers. Copyright © 2002 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Summary: Thermal energy storage systems in building cooling applications have been explored extensively as a peak load‐shifting technology. Thermal energy storage performance has been recognized and studied from an energy cost‐savings point of view because of peak‐valley price differences, but not many studies have been conducted from an energy savings viewpoint. This study experimentally investigates the performance of the energy storage‐retrofitted to a ceiling‐type radiant cooling system. To study the performance, a water‐based storage system was designed and developed for an academic office building equipped with a radiant cooling system. The water in the storage tank was cooled to a certain storage temperature in the nighttime, and the same water was used during the daytime for meeting the cooling load. Different combinations of charging and discharging schedules were analyzed. The key objective of the study was to achieve energy savings and energy‐cost savings simultaneously. This objective was accomplished by identifying the major factors contributing to the energy consumption of the storage‐retrofitted cooling system and devising novel operating strategies, leading to an enhanced energy savings potential. Two operating strategies comprising 24 operating scenarios were compared and the storage was used to dispatch the load for 3 hours of the day as a full storage unit. Results showed that in hot and dry climate conditions, using the storage with the radiant cooling system offered energy savings of 3% to 14%. The energy‐cost analysis was also performed using a time‐of‐day electricity tariff plan. The energy‐cost savings varied from 17.5% to 22.4% for these operating scenarios. [ABSTRACT FROM AUTHOR]

Summary: The waste heat management of the data center cooling systems has a significant share in the energy‐efficient operations of the data centers. In this study, a new hybrid desalination‐data center cooling system is proposed to reduce the cost drawback of the waste heat in the data center cooling operations. A two‐phase liquid‐immersion cooling unit is selected as the data center cooling method with the cooling load range of 0.7 to 1.5 kW. It is a promising solution thanks to the high heat flux removal performance but there is still a lack of research about waste heat management. The waste heat of the immersion cooling system is used to heat up the feed side of the desalination module. A direct contact membrane distillation system as preferred as the desalination module with the membrane area range of 5 to 75 cm2. The proposed hybrid system is investigated according to the thermodynamic, economic, and thermoeconomic aspects. The thermoeconomic assessment is done concerning the unique exergy‐cost matrix of the original design. The maximum thermal and exergy efficiencies are found as 64.5% and 53.7%, respectively. The daily distilled water rate can reach 6.13 kg at the highest cooling load and membrane area. Compared to the stand‐alone data center cooling operation, the hybrid system has higher capital and operation costs. The payback period is found 3.72 years that means the proposed system is economically feasible for real applications. Also, the levelized product cost of the hybrid design is calculated in the range of 2.69 to 5.33 SGD/h. In the multiobjective optimization study, the best trade‐off point is decided at the cooling load of 1.1 kW whilst the membrane area varies between 5.12 and 5.19 cm2. [ABSTRACT FROM AUTHOR]

SUMMARY Integrated energy system is a very important way to improve energy efficiency. Based on the combined heating cooling and power system, combined with energy storage equipment, a cross‐regional integrated energy system scheduling optimization problem is studied. An integrated energy system scheduling optimization model is established that meets the requirements of electrical, heating, and cooling load under a variety of energy sources while both considering the interaction of electrical, heating, and cooling load between regions, and complementation of them within one region. Meanwhile, the value at risk (VaR) theory is introduced and the operating constraints of equipment in the integrated energy system fully considered, the integrated energy system scheduling model with VaR is established. The example shows that the model can realize multi‐type electrical, heating, and cooling load optimized by schedule across regions under the premise of satisfying the balance of energy supply and demand, which can reduce the system operation cost. The sensitivity analysis of the minimum expected cost and the influencing factors of conditional VaR is carried out to verify the validity and feasibility of the proposed model. An integrated energy system scheduling optimization model is established that meets the requirements of electrical, heating, and cooling load under a variety of energy sources while both considering the interaction of electrical, heating, and cooling load between regions, and complementation of them within one region.By using the conditional value at risk theory to consider various types of the integrated energy system complements and evaluates the operational risk of the system under optimal operating conditions of the system.The total cost of system scheduling operation is proportional to the storage capacity, which is inversely proportional to the heat storage capacity and inversely proportional to the pipeline capacity within a certain interval. [ABSTRACT FROM AUTHOR]

The ecological optimization and parametric study of an irreversible Ericsson cryogenic refrigerator cycle with finite heat capacities of external reservoirs is studied. The ecological function is defined as the cooling load minus the loss of the cooling load (the irreversibility) due to the entropy generation rate. The ecological function is optimized with respect to working fluid temperatures and the values of the cooling load, power input, the loss rate of the cooling load and COP are calculated for a typical set of operating parameters. The effects of different operating parameters on the ecological function, cooling load, the loss rate of the cooling load and COP are studied. The loss rate of the cooling load and the power input are found to be increasing functions of the cycle temperature ratio and decreasing functions of COP while the COP is found to be a decreasing function of the cycle temperature ratio. On the other hand, there exist the optimal values of the cycle temperature ratio and COP at which the ecological function and cooling load attain their maximum values. Also the ecological function and the cooling load are found to be increasing functions of the sink‐side heat capacitance rate and the effectiveness on the source‐, sink‐, and regenerative‐side heat exchangers while the decreasing functions of the source‐side heat capacitance rate. Copyright © 2005 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]