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• Thermal performance of the proposed hot water storage was evaluated experimentally. • Proposed solution shows a 19% less total thermal loss than the centralised system. • Circulating pump in this solution consumes 11 times lower energy than centralised one. • The LCC of proposed solution is 6.1% lower than that of the centralised system. • Centralised system requires higher operating costs but a lower control system cost. The retrofit solution for domestic hot water (DHW) system in existing buildings requires to ensure the long-term energy security and efficiency as well as to minimise occupants' disturbance, construction works and installation costs. In this regard, the present study performs a techno-economic evaluation on a novel retrofit solution for DHW production in a pilot building. The proposed solution appoints a substantial role to the thermal energy storage through a 2-pipe hot water network utilisable for both DHW and heating purposes. The first storage level is provided by a centralised buffer storage supplied by a PV-BESS-driven heat pump while the second level consists of decentralised modular tanks installed in each dwelling for the production and storage of hot water. Firstly, experimental thermal performance of the proposed decentralised storages is investigated. By developing a dynamic simulation code, the energy efficiency of the proposed solution is compared to that of the existing system in the pilot building as well to that of a typical centralised system as a benchmark solution. Finally, economic analysis of the retrofit solution is performed to address capital expenditures of the system, including purchasing and installation costs, as well as its life cycle cost (LCC). The obtained results indicate that the proposed system reduces the annual energy consumption for DHW production more than 7,200 kWh, with respect to the existing DHW system. Furthermore, it is shown that, in the proposed system, the fraction of thermal loss from piping network decreases by 31.5%, compared to a typical DHW centralised system. Economic assessment of the proposed solution implies that this system, in terms of both mechanical and electrical components, requires 13.7% lower initial investment than a typical centralised system. However, the cost of control systems in this system is higher since it is inherently a control-based system. [ABSTRACT FROM AUTHOR]

Highlights • Dynamic modelling of combined-cycle gas turbine power plant with thermal storage. • Cascaded latent heat storage integration strategies to plant operation processes. • Complete system dynamic simulations of the plant with cascaded latent heat storage. • Quantified analysis of stored and released thermal energy for different strategies. Abstract The combined-cycle gas turbine (CCGT) power plants are often required to provide the essential fast grid balance service between the load demand and power supply with the increase of the intermittent power generation from renewable energy sources. It is extremely challenging to ensure CCGT power plants operating flexibly and also maintaining its efficiency at the same time. This paper presents the feasibility study of a CCGT power plant combined with the cascaded latent heat storage (CLHS) for plant flexible operation. A 420 MW CCGT power plant and a CLHS dynamic models are developed in Aspen Plus based on a novel modelling approach. The plant start-up processes are studied, and large amount of thermal energy can be accumulated by CLHS during the start-up. For load-following operation, extensive dynamic simulation study is conducted and the simulation results show that the extracted exhaust gas can be used for thermal energy storage charging, and the stored heat can be discharged to produce high temperature and high pressure steam fed to the steam turbine. Besides, the stored heat can also be used to maintain the heat recovery steam generator (HRSG) under warm condition to reduce plant restart-up time. The simulation results demonstrate that the integration of CLHS with CCGT power plant is feasible during the start-up, load-following and standstill operations. [ABSTRACT FROM AUTHOR]

The heat transfer performances of evaporators and condensers significantly affect the efficiency of household refrigerators. For enhancing heat transfer of the condensers and evaporators, a novel dual energy storage (DES) refrigerator with both heat storage condenser (HSC) and cold storage evaporator (CSE) is proposed. The performance comparison of three kinds of energy storage refrigerators: HSC refrigerator, CSE refrigerator and DES refrigerator is analyzed by establishing dynamic simulation models. According to the simulation results, the DES refrigerator combines the advantage of HSC refrigerator and CSE refrigerator, it has more balanced operational cycle and higher evaporation pressure and temperature. The DES refrigerator shows a best energy saving performance among the three energy storage refrigerators with largest off-time to on-time ratio of 4.3 and the electrical consumption saving can reach 32%, which is greater than the sum (28%) of the other two kinds of energy storage refrigerators. [ABSTRACT FROM AUTHOR]

• A new energy system is developed and examined using dynamic modelling to meet the needs of a two-story structure. • To decrease the size of the plant, including the PVT size and fuel consumption, the PCM is incorporated into the building. • Fuel consumption and prices are reduced by 17.24% and 8.57%, respectively, using the suggested approach. • Exergy efficiency, unit product cost, and CO 2 emission of 64.3 %, 0.26 $/kWh, and 0.21 kg/kWh are obtained respectively at optimum point. The buildings energy sector is expected to account for 40% of total world energy consumption and 40% participation on total carbon dioxide emissions, according to the International Energy Agency reports. The present study proposes a novel integrated system to meet all loads of the house's energy requirements. The system employs a heat storage tank rather than pricey batteries, which helps to keep the total cost of the system as low as feasible. Also, the system is developed for an on-grid operation, being capable to sell surplus energy to the grid helping to reduce the payback time. Dynamic modeling is conducted to analyze the system performance to provide heating, cooling and power demands of a case study building, for which two scenarios of with and without Phase Change Material (PCM) incorporation is considered. The influence of critical design factors is investigated, after which a tri-objective optimization is carried out. It was found that, the integration of PCM energy storage would reduce the annual heating and cooling demands of the building by 25.6%. As a result, the exergy efficiency of the proposed system increases by 13 % and the product cost is reduced by 8.57%. Based on the obtained yearly average results, the proposed building energy system yields exergy efficiency, unit product cost, and CO 2 emission of 64.3 %, 0.26 $/kWh, and 0.21 kg/kWh, respectively. [ABSTRACT FROM AUTHOR]

In an adiabatic compressed air energy storage process (A-CAES), heat storage tank operation is a key factor that determines the overall energy performance of the process. To highlight energy issues linked to a correct tank design in the specific case of an A-CAES system, a two-dimensional thermal numerical model was developed. Thermal efficiencies of the tank are presented with abacus defined from the four dimensionless numbers defining the thermal behavior of the reservoir. Cycling effects are explored with a realistic case study corresponding to an A-CAES system design to deliver an electrical power of 250 MWel for 4 h, the daily peak demand. Extended beyond the thermal reservoir, A-CAES thermodynamic analysis combined with the dynamic simulation makes it possible to generate a direct quantitative link between reservoir sizing and A-CAES global efficiency. [ABSTRACT FROM AUTHOR]

Highlights: [•] A novel dynamic model for thermocline thermal energy storage systems is presented. [•] Adaptive grid technique used. [•] Accuracy is improved while using an order of magnitude fewer states and equations. [•] Effects of numerical diffusion are minimized. [•] Model more accurate under temperature (and density) inversion. [ABSTRACT FROM AUTHOR]

[Display omitted] • Biomass power plant model integrated with thermochemical heat storage was created. • Fluidized bed using Ca(OH) 2 /CaO stores surplus electricity from renewable energy. • Overall energy efficiency was 9.79% for the base case (output: 1 MW el). • Steam flow rate is most important parameter for flexible power generation. • Energy storage efficiency is dramatically improved by recycling steam. In this study, a biomass power plant integrated with thermochemical heat storage (TCS) using Ca(OH) 2 /CaO particles reacted in a fluidized bed reactor was proposed. In the strategy of power generation, organic Rankine cycle (ORC) was worked by the heat from biomass combustion in normal operation. In charging time, the electricity from the power grid was stored by dehydration reaction in the daytime although the turbine output was not changed, and the amount of biomass combustion decreased compared to normal operation time. In discharging time, the heat from hydration reaction was converted to electricity through the ORC in the evening and the turbine output increased to respond to the increase of the electricity demand. The designed process was evaluated from energy efficiencies and the flexibility of the power generation by dynamic simulation. Results show energy storage efficiency and overall energy efficiency equaled 58.5% and 9.79% (only ORC: 11.4%) for base case, respectively. The energy storage efficiency increased by increasing the heat recovery from steam after a reactor, and it led to the decrease of the biomass combustion in charging time. It was found that the inlet gas flow rate into the reactor had the largest influence on energy efficiencies by changing the parameters such as fluidized bed volume, inlet gas conditions into the reactor, and heat supply into the reactor. In addition, the increase of the turbine output and discharging time were flexibly changed in discharging time by changing operational parameters. Therefore, it is possible to add flexibility to biomass power plants by integrating TCS. [ABSTRACT FROM AUTHOR]

• Optimization of dynamic poly-generation system is conducted for building application. • A hybrid simulation model is newly developed to improve conventional methods. • Capacity optimization based on a meta-model is carried out with a genetic algorithm. • A multi-criteria evaluation has been performed with sensitivity and feasibility analysis. A decentralized small-scale poly-generation system has attracted lots of attention nowadays. In this study, the poly-generation system is optimized and evaluated for the building application. To reduce the high computational cost of dynamic simulation and multi-objective global optimization process, a hybrid simulation model has been newly proposed. The new hybrid model is developed with the validation and verification of each system component. Based on the developed model, the meta-model is optimized for improving the multi-criteria indices (energy, environment, and economy). For the optimization, the critical design variables are selected as the rated electrical power of the prime mover, the volume of thermal storage system, the cooling/heating capacity ratio supplied by electrically driven systems, and maximum heat power from the storage system. As a result of optimization and decision making, the most effective point from Pareto frontier is determined. In addition, sensitivity analysis and feasibility evaluation are conducted to investigate the effectiveness of the poly-generation system when integrated with the building in South Korea. The results show that primary energy consumption is reduced by 22.9%, CO 2 emissions by 14.2%, and annualized total cost by 6.0%, respectively. Through the specific economic investigation, the payback year is calculated as 6.2. Finally, the performance that greatly affects multi-criteria indices is further discussed in terms of utilization rate, load coverage, and self-sufficiency ratio. [ABSTRACT FROM AUTHOR]