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• A new structural design method for earth-to-air heat exchangers in greenhouses is described. • The structural design method incorporates greenhouse heat balance model to better match greenhouse characteristics. • The system is more energy-efficient and stable in intermittent operation mode. • Application of an earth-air heat exchanger is a green technology for greenhouse sustainability. An earth-air heat exchanger (EAHE) is a type of environmental regulation equipment that is suitable for greenhouses. In the future, it could be a green technique for greenhouse energy supplementation. However, EAHEs lack structural design methods for application in greenhouses. Consequently, this paper presents a structural design method for an EAHE based on the architectural characteristics of greenhouses. Firstly, the EAHE design heat exchange amount was calculated according to the greenhouse heat and cold load, then the pipe length, diameter, air velocity, and burial depth were determined by combining the heat transfer efficiency and number of transfer units (NTU), and finally the final parameters were optimized and selected according to the energy loss and construction cost. The design method was validated in a greenhouse in northern China, and the heat transfer performance was analyzed in both intermittent and continuous operation modes. The results showed that the novel structural design method could guide the application of EAHE in a greenhouse and satisfy the energy demand of greenhouses. The measured average greenhouse temperature at night increased by 1.57 °C and 1.11 °C, respectively, under intermittent operation and continuous operation and decreased by 1.19 °C and 1.32 °C, respectively, during the day. The EAHE performance coefficients for heating and cooling conditions under intermittent operation were 21.49 and 18.15, respectively, significantly higher than those for continuous operation. [ABSTRACT FROM AUTHOR]

Abstract: This paper develops an overall methodology for investigating the thermal and power behaviors of semi-transparent single-glazed photovoltaic window for office buildings in Hong Kong. In order to estimate its overall energy performance, this study is conducted in terms of total heat gain, output power and daylight illuminance. Three simulation models are established, including one-dimensional transient heat transfer model, power generation model and indoor daylight illuminance model. A typical office room reference is chosen as case study, and the weather data from 2003 to 2007 from the Hong Kong Observatory are used as the simulation inputs. By incorporating the simulation results, the overall energy performance can be evaluated in terms of electricity benefits corresponding to five orientations of the studied typical office. The priority of office orientation considering overall energy performance is: south-east, south, east, south-west and west. The findings show that thermal performance is the primary consideration of energy saving in the entire system whereas electricity consumption of artificial lighting is the secondary one. The overall annual electricity benefits are about 900 kWh and 1300 kWh for water-cooled and air-cooled air-conditioning systems respectively. The application of semi-transparent PV glazed window can not only produce clean energy, but also reduce building energy use by reducing the cooling load and electrical lighting requirements, which definitely benefits our environmental and economic aspects. [Copyright &y& Elsevier]

Recently, the structural insulated panels (SIPs) with the wood-based surfacing materials are developed in housing industry to increase the thermal efficiency of the wall system. In order to integrate the waterproof feature into SIPs, a newly designed GFRP reinforced squared tube sandwich panel (GSTPs) is introduced, where the Glass fibre reinforced polymers (GFRP) is utilized as surface material and the core is reinforced by the GFRP square tube. This paper focused on the thermal insulation performance of GSTPs. Both experimental, theoretical and numerical methods are employed to study their thermal insulation performance as roof panels. More specifically, the thermal conductivity of GFPR with three different core materials, including glass wool, Extruded polystyrene (XPS) and Polyurethane (PU) in the SIP, was first measured by hot plate apparatus (HPA) in the steady-state heat transfer tests. Then, the heat transfer coefficients of three type of GSTPs with above mentioned core materials are measured by guarding heat box (GHB) test. The theoretical and finite element (FE) method based numerical studies applied to conduct the heat transfer analyses on those SIPs. The accuracies of the theoretical and numerical studies are verified by comparing the obtained heat transfer coefficients with those from the experimental tests. The results from the present study could provide a good reference to the selection of the suitable panel thickness and core materials for different thermal regions in China. [ABSTRACT FROM AUTHOR]