Performance of an integrated solar absorption cooling system in a sub-tropical region

Evaluation of an integrated solar absorption cooling system located in a sub-tropical region has been carried out. Analysis of the results revealed an operational efficiency of 61% for the solar collectors at a mean differential temperature forumla of 51°C when compared with the manufacturer's rating of 70% at 60°C. The absorption chiller did, however, perform quite satisfactorily and achieved a coefficient of performance of 0.69 when compared with the manufacturer's rating of 0.7. There is however the need for the hot water supply system to be optimized as well as provision for supplementary heat source in order to maintain the appropriate operating temperature during low solar radiation levels

A simulation-based framework for a mapping tool that assesses the energy performance of green roofs

This paper presents a framework for the development of a GIS open source mapping tool that aims to disseminate a database with results of detailed simulations in order to assess in a quick and easy way the energy performance of green roof designs across a range of Chinese climates. Detailed simulation results for heating and cooling loads are obtained from the EnergyPlus simulation tool. The study covers 12264 configurations by varying model parameters such as climate, glazing type, roof insulation, soil and plant characteristics, etc. It was found that green roofs can offer significant energy savings if they are applied on roofs without insulation but only limited energy savings where heavy insulation on the roof is also applied. Quick comparisons across a large range of roof characteristics could be easily made with the implementation of the GIS map tool and the design of green roof that fits the specific climate could be optimised without the knowledge of a detailed building energy simulation tool. The critical parameters that affect the green roof’s performance are also highlighted

Evaluation of thermal energy dynamics in a compacted high-conductivity phase-change material

This study evaluates the concept of developing a nondeform phase-change energy storage material possessing higher thermal conductivity and energy storage density through a pressure compaction process. The theoretical and experimental investigations have shown that the technique is able to reduce porosity and increase conductivity and energy storage density of a composite material. Even though there was some measure of plastoelasticity due to decompression, the average porosity was reduced from 62 to 23.8% at a relatively low compaction pressure of 2.8 MPa without any structural damage to the tested sample. The mean energy storage density increased by 97%, and the effective thermal conductivity also increased by 25 times, despite a 10% reduction in its latent heat capacity. There is, however, the need for further development toward minimizing the effect of decompression and achieving stronger energy storage tablets at a relatively low compaction force

Thermal evaluation of laminated composite phase change material gypsum board under dynamic conditions

Thermal evaluation of non-deform laminated composite phase change material (PCM) gypsum board has been carried out. The theoretical studies covered the analysis of different thicknesses of PCM layers and their corresponding heat transfer rates during energy storage and discharge processes. A simply approach was also provided for determining the appropriate thicknesses of PCM layer under various conditions. For the purpose of experimental study and validation, a laminated gypsum board consisting of a 4 mm PCM layer was evaluated in a naturally ventilated condition. It achieved a maximum heat exchange of 15.6 W/m2 and a maximum energy storage of 363.7 kJ/m2. A model room built with the laminated PCM gypsum boards was also evaluated and achieved a maximum temperature reduction of 5 °C as compared with 1.8 °C for the one with ordinary gypsum board. Even though about 25% of the energy stored could not be released within the targeted period, the overall thermal performance of the PCM gypsum board was quite remarkable. Further heat transfer enhancement mechanism may therefore be necessary for the energy discharge process

Heat transfer analysis of an integrated double skin façade and phase change material blind system

In this study, the heat transfer in an integrated double skin facade (DSF) and phase change material (PCM) blind system has been theoretically analysed. Both heat transfer and airflow models with CFD methods have been developed for the integrated DSF and PCM blind system. Data from an existing typical DSF building have been obtained in order to define input parameters for the simulation exercise and validate the numerical models. The temperature and velocity fields in DSF with the PCM blind system has been predicted under overheating scenario using the ANSYS Workbench FLUENT software and been compared with case of conventional aluminium blind system. This study has shown that the integrated PCM blind system was able to reduce the average air temperature and outlet temperature of the DSF while improving the convective heat transfer between the cavity air and the blades. Compared with the aluminium blind, the PCM blind can absorb large amount of excessive heat in the cavity. Overall the integrated PCM blind system has the potential to be used as an effective thermal management device for minimising the overheating effect in DSFs

Development of high melting temperature microencapsulated phase change material for compacted thermal energy storage bed

In this paper a novel high temperature microencapsulated phase change material (MEPCM) based on paraffin as the core material and MF resin as the shell material has been developed with the in-situ polymerization method for solar hot water storage application. The results showed that the type of emulsifier could influence core material content, the encapsulation efficiency as well as the latent heat capacity. Based on the results and analysis the study has shown that energy storage density could be increased by as much as 59% if 60wt% of MEPCM 1 was to be used in the proposed compacted MEPCM-water bed system

The Effects of Future Climate Change on Energy Consumption in Residential Buildings in China and Retrofitting Measures to Counteract

At present, China is going through a rapid rate of mass urbanisation, and this poses a number of challenges for the building sector. On one hand, under new directives from the government, new buildings will have stricter energy requirements and existing buildings will also need to lower their rate of energy consumption, on another hand, the lifetime of buildings are now intended to last longer, meaning that building designers will also need to account for effects of future climate change when assessing the performance of building schemes. This paper investigates the effect of future climate change on energy consumption in typical residential buildings in different climate regions of China. These include the “Cold” region in the north, which includes Beijing; the “Hot Summer Mild Winter” region in the south, which includes Guangzhou, and two regions from the “Hot Summer Cold Winter”, one along the coast in the east, which includes cities such as Shanghai and Ningbo; the inland region, which includes cities such as Wuhan and Chengdu. Using data from the climate model, HadCM3, Test Reference Years are generated for the 2020s, 2050s and 2080s, for various IPCC future scenarios for these cities. These are then used to assess the energy performance of typical existing residential buildings, and also the effects of retrofitting them to the standard of the current building codes. It was found that although there are reductions in energy consumption for heating and cooling with retrofitting existing residential buildings to the current standard, the actual effects are small compared with the extra energy consumption that comes as a result of future climate change. This is especially true for Guangzhou, which currently have very little heating load, so there is little benefit of the reduction in heating demand from climate change. The overall effects of retro-fitting in other selected cities depend largely on the specification of current existing buildings. In general, more improvements in building standards in all four regions are required to significantly reduce the effects of future climate change

Thermal performance of a novel helically coiled oscillating heat pipe (HCOHP) for isothermal adsorption: an experimental study

Helically Coiled Oscillating Heat Pipes (HCOHPs) have been designed and tested under laboratory conditions to investigate their potential to achieve isothermal adsorption when integrated with a cylindrical solid desiccant packed bed system. The HCOHPs fabricated out of copper, are essentially single turn closed loop oscillating heat pipes with their evaporator and condenser sections helically coiled. They were charged with ethanol, methanol and deionized water respectively at approximately 60% volume fill ratio and tested by slotting through their helically coiled evaporators an empty cylindrical copper vessel which allowed hot air to be blown through at various heat loads to ascertain their thermal performances. The results showed there were critical heat fluxes which varied with heat input amount at the evaporator, beyond which dry-out commenced and thermal resistance increased. These heat fluxes were ≤70W≤70W for the ethanol HCOHP and ≤105W≤105W for both the methanol and deionized water HCOHPs. Performance instabilities owing to liquid phase of the working fluid transitioning in the drying-out stage was observed for the methanol HCOHP beyond 234W. The variation of the effective thermal conductivities at the evaporators were found to influence the thermal contact resistance experienced at the contact interface of integration and the maximum heat input amount at the evaporators. Optimum performance between the HCOHPs was observed with the deionized water type. Overall, the HCOHPs were capable of managing relatively large amounts of heat input due to their helically coiled sections creating comparatively larger evaporator sections holding relatively more working fluid than the conventional serpentine single turn closed loop OHP system of the same volume and fill ratio. Investigations involving the visualization of the internal flow dynamics is recommended for future studies

Effect of design parameters on thermal performance of integrated phase change material blind system for double skin façade buildings

Double skin facades (DSFs) have overheating problems in warm seasons which may increase the cooling loads in buildings. A previous study has developed an integrated phase change material (PCM) blind system and proved its capacity of mitigating the overheating phenomenon in DSFs. This paper focuses on the effect of design parameters on the thermal performance of such systems by conducting a simulation study of a DSF integrated with a PCM blind with different material properties, positions in cavity, and tilt angles of blades. The results indicate that the performance of the integrated PCM blind system can be optimised with careful geometric design and proper thermophysical properties of the PCM