• Energy Research

Abstract This paper considers two commercial and residential buildings for building energy resilience against natural disasters that cause a power outage. The buildings are modeled with a shared parking station for their electric vehicles. The peer-to-peer operation is modeled for the buildings. The electric vehicles inside the parking station have dissimilar patterns of availability and such dissimilarity helps the buildings to be benefited from the vehicles for extra hours. The power outage is modeled at different day hours and with various durations. The building is supported by energy management options to handle such disruptions. The options are a peer-to-peer operation of the building, electrical vehicle charging-discharging, partial charge ability, load curtailment, and load adjustment. The proposed model only utilizes available components of the buildings and it does not need to install further components. The purpose is to minimize energy cost and maximize energy resilience under natural disasters. The resilience is defined as critical load restoration and minimum energy loss under various power outages. The results demonstrate that the designated energy management options can practically minimize energy cost and improve energy resilience following blackouts. The electric vehicles can reduce energy cost by about 25% and supply the loads under 7-h power outage.

The depletion of fossil fuel reserves and growing energy demand have increased the need for renewable energy sources with suitable heat storage systems. Latent heat thermal energy storage (LHTES) using phase change materials (PCMs) provides high energy density and efficiency. However, heat transfer to the PCM core remains a challenge. This study investigates step, sinusoidal, and zigzag channel designs within a horizontal triple-tube LHTES system to enhance PCM charging rates. The step function geometry offered superior performance, increasing heat storage rate by 145 % and reducing melting time by 51 % versus straight channels. Detailed parametric analysis revealed that reducing step width from 15 mm to 5 mm improved heat storage rate by 18 % and shortened melting time by 14 %. Lengthening steps from 5 mm to 15 mm enhanced heat storage rate by 88 % and accelerated melting by 48 %. The novel step design improved temperature distrbution, drove recirculation enhancing convection, and increased surface area. These insights can guide engineering of efficient LHTES systems, advancing sustainable energy storage solutions.

The solidification process in a multi-tube latent heat energy system is affected by the natural convection and the arrangement of heat exchanger tubes, which changes the buoyancy effect as well. In the current work, the effect of the arrangement of the tubes in a multi-tube heat exchanger was examined during the solidification process with the focus on the natural convection effects inside the phase change material (PCM). The behavior of the system was numerically analyzed using liquid fraction and energy released, as well as temperature, velocity and streamline profiles for different studied cases. The arrangement of the tubes, considering seven pipes in the symmetrical condition, are assumed at different positions in the system, including uniform distribution of the tubes as well as non-uniform distribution, i.e., tubes concentrated at the bottom, middle and the top of the PCM shell. The model was first validated compared with previous experimental work from the literature. The results show that the heat rate removal from the PCM after 16 h was 52.89 W (max) and 14.85 W (min) for the cases of uniform tube distribution and tubes concentrated at the bottom, respectively, for the proposed dimensions of the heat exchanger. The heat rate removal of the system with uniform tube distribution increases when the distance between the tubes and top of the shell reduces, and increased equal to 68.75 W due to natural convection effect. The heat release rate also reduces by increasing the temperature the tubes. The heat removal rate increases by 7.5%, and 23.7% when the temperature increases from 10 °C to 15 °C and 20 °C, respectively. This paper reveals that specific consideration to the arrangement of the tubes should be made to enhance the heat recovery process attending natural convection effects in phase change heat storage systems.

Globally there are several viable sources of renewable, low-temperature heat (below 130 °C), particularly solar energy, geothermal energy, and energy generated from industrial wastes. Increased exploitation of these low-temperature options has the definite potential of reducing fossil fuel consumption with its attendant very harmful greenhouse gas emissions. Researchers have universally identified the organic Rankine cycle (ORC) as a practicable and suitable system to generate electrical power from renewable sources based on its beneficial usage of volatile organic fluids as working fluids (WFs). In recent times, researchers have also shown a preference towards deployment of zeotropic mixtures as ORC WFs because of their capacity to improve thermodynamic performance of ORC systems, a feat enabled through the greater matching of the temperature profiles of the WF and the heat source/sink. This paper demonstrates the thermodynamic, economic and sustainability feasibility, and the notable advantages of using zeotropic mixtures as WFs through a simulation study of an ORC system. The study examines first the thermodynamic performance of ORC systems using zeotropic mixtures to generate electricity powered by a low-temperature solar heat source for building applications. A thermodynamic model is developed with a solar-driven ORC system both with and excluding a regenerator. Twelve zeotropic mixtures with varying compositions are evaluated and compared to identify the best combinations of mixtures that can yield high performance and high efficiency in their system cycles. The study also examines the effects of the volume flow ratio, and evaporation and condensation temperature glides on the ORC’s thermodynamic performance. Following a detailed analysis of each mixture, R245fa/propane and butane/propane are selected for parametric study to investigate the influence of operating parameters on the system’s efficiency and sustainability index. For zeotropic mixtures, results disclosed that there is an optimal composition range within which binary mixtures are inclined to perform more efficiently than the component pure fluids. In addition, a substantial enhancement in cycle efficiency can be obtained by a regenerative ORC, with cycle efficiency ranging between 3.1–9.8% and 8.6–17.4% for ORC both without and with regeneration, respectively. Results also revealed that exploiting zeotropic mixtures could enlarge the limitation experienced in selecting WFs for low-temperature solar ORCs. Moreover, a detailed economic with a sensitivity analysis of the solar ORC system was performed to evaluate the cost of the electricity and other economic criteria. The outcome of this investigation should be useful in the thermo-economic feasibility assessments of solar-driven ORC systems using working fluid mixtures to find the optimum operating range for maximum performance and minimum cost.

Abstract In this paper, to provide the cold water required in a factory, a refrigeration system with a storage tank is designed with two different storage modes i.e. full and partial in comparison with the non-storage system. Two different storage scenarios including cold water and ice are examined. The thermo-economic analysis is performed to study the performance of the system comprehensively. It is shown that, the volume of the storage tank in ice storage-full mode, cold water storage-partial mode and cold water storage-full mode cases are 410%, 510% and 2300% respectively, higher than volume of the storage tank in ice storage-partial mode. For full cold water storage, the current energy consumption is reduced by 72% compared to the direct cooling mode without the storage tank. The results show that a system with the partial storage of cold water has a lower initial cost than a non-storage system. Furthermore, less energy and current costs will be achieved by the partial cold water storage system. Full storage of cold water can be considered as an option, with the 14-year payback.

A twisted-fin array as an innovative structure for intensifying the charging response of a phase-change material (PCM) within a shell-and-tube storage system is introduced in this work. A three-dimensional model describing the thermal management with charging phase change process in PCM was developed and numerically analyzed by the enthalpy-porosity method using commercial CFD software. Efficacy of the proposed structure of fins for performing better heat communication between the active heating surface and the adjacent layers of PCM was verified via comparing with conventional longitudinal fins within the same design limitations of fin material and volume usage. Optimization of the fin geometric parameters including the pitch, number, thickness, and the height of the twisted fins for superior performance of the proposed fin structure, was also introduced via the Taguchi method. The results show that a faster charging rate, higher storage rate, and better uniformity in temperature distribution could be achieved in the PCMs with Twisted fins. Based on the design of twisted fins, it was found that the energy charging time could be reduced by up to 42%, and the energy storage rate could be enhanced up to 63% compared to the reference case of straight longitudinal fins within the same PCM mass limitations.

This study investigated the laminar convective heat transfer and fluid flow of Al2O3 nanofluid in a counter flow double-pipe heat exchanger equipped with overlapped twisted tape inserts in both inner and outer tubes. Two models of the same (co-swirling twisted tapes) and opposite (counter-swirling twisted tapes) angular directions for the stationary twisted tapes were considered. The computational fluid dynamic simulations were conducted through varying the design parameters, including the angular direction of twisted tape inserts, nanofluid volume concentration, and Reynolds number. It was found that inserting the overlapped twisted tapes in the heat exchanger significantly increases the thermal performance as well as the friction factor compared with the plain heat exchanger. The results indicate that models of co-swirling twisted tapes and counter-swirling twisted tapes increase the average Nusselt number by almost 35.2–66.2% and 42.1–68.7% over the Reynolds number ranging 250–1000, respectively. To assess the interplay between heat transfer enhancement and pressure loss penalty, the dimensionless number of performance evaluation criterion was calculated for all the captured configurations. Ultimately, the highest value of performance evaluation criterion is equal to 1.40 and 1.26 at inner and outer tubes at the Reynolds number of 1000 and the volume fraction of 3% in the case of counter-swirling twisted tapes model.