Evaluation of a solar thermal system using building louvre shading devices

External louvres are increasingly used to provide solar protection for building glazed surfaces. The integration of collectors into the external louvres of buildings offers a means of reducing system cost as well as providing architects with more freedom to integrate the technology into their designs. This work concerns the modification of existing louvre designs to integrate a solar collector in the shading device. The evaluation of a thermal solar system for water heating is assessed in this paper. A numerical model for the integrated solar collector was developed for different configurations and the collector efficiency is quantified for each configuration. System thermal performance was obtained for the climatic conditions of Lisbon (Portugal) and Tenerife (Spain). Economic and environmental viability of the system is assessed.     

Periodic heat flux through a three layered slab

This communication presents a derivation of an explicit expression for the periodic variation of thermal flux through a composite slab (insulation-concrete-insulation or concrete-insulation-concrete), with one face exposed to solar radiation and atmospheric air and the other face in contact with room air at constant temperature. It is seen that for maximum or minimum load levelling of the periodic heat flux the thicknesses of the outer layers of the composite slab are equal.     

Analytical thermal modelling of multi-basin solar still

Based on energy balances for different components of a multi-basin solar still, namely, the basin-liner, the water mass and the glass cover, analytical expressions for water and glass temperatures have been derived in terms of climatic and design parameters of the system. It is inferred that the daily yield is a maximum for the least water depth in each basin     

聚焦太阳能建筑外观的能源论坛

第七届太阳能建筑外观能源论坛于2012年12月6～7日在意大利布列瑟农举行。本届论坛旨在为建筑师、工程师、科学家、能源管理者和光伏设备制造商创造对话机会,提供一个国际交流的平台,研究讨论出一种多学科的综合规划办法,在改善居住者舒适性和身心健康的同时减少能源消耗。能源论坛总经理Mr.Andreas Karweger在开幕式上致辞。     

Solar assisted heat pump on air collectors: A simulation tool

The heating system of the bioclimatic building of the Greek National Centre for Renewable Energy Sources (CRES) comprises two heating plants: the first one includes an air source heat pump, Solar Air Collectors (SACs) and a heat distribution system (comprising a fan coil unit network); the second one is, mainly, a geothermal heat pump unit to cover the ground floor thermal needs. The SAC configuration as well as the fraction of the building heating load covered by the heating plant are assessed in two operation modes; the direct (hot air from the collectors is supplied directly to the heated space) and the indirect mode (warm air from the SAC or its mixture with ambient air is not supplied directly to the heated space but indirectly into the evaporator of the air source heat pump). The technique of the indirect mode of heating aims at maximizing the efficiency of the SAC, saving electrical power consumed by the compressor of the heat pump, and therefore, at optimizing the coefficient of performance (COP) of the heat pump due to the increased intake of ambient thermal energy by means of the SAC. Results are given for three research objectives: assessment of the heat pump efficiency whether in direct or indirect heating mode; Assessment of the overall heating plant efficiency on a daily or hourly basis; Assessment of the credibility of the suggested simulation model TSAGAIR by comparing its results with the TRNSYS ones.     

Application and development of solar energy in building industry and its prospects in China

China is the second largest country in energy consumption. More and more energy demand pressures cause the Chinese government to review its economy and energy policies in order to support the sustainable development. In China, the building sector amounts to 27.8% total energy consumption, which is only behind the industry sector. China has abundant solar energy resource, which is extensively applied to buildings. Therefore, solar energy utilization in buildings has become one of the most important issues to help China optimize the energy proportion, increasing energy efficiency and protecting the environment. Solar energy resource and its district distribution in China are introduced in detail in this paper, and the representative solar energy application to the building sector is highlighted as well. The solar energy utilization obstacles, especially policy disadvantages in building sector in China, are reviewed. Moreover, the application prospects of solar energy in building sector are presented in combination with the China economic and household industry growth.     

Active/passive heating of an office building

This paper presents a periodic analysis to predict the enclosed air temperature for an active and/or passively heated office building in a climate where the solar intensity is small and the ambient air temperature varies about the freezing temperature of water. It also suggests a way to control the enclosed air temperature by adjusting the size of the collector and air flow rate.     

Solar thermal utilization in China

With the rapid development of the Chinese economy, energy consumption has increased considerably, and this has increased pressure on energy production. On the other hand, this pressure has greatly assisted in the development of the renewable energy in the past two decades. This paper reports the latest developments in the solar thermal utilization in China. A great deal of successful examples of solar thermal utilization are presented. Issues of most concern and interest, which are resisting a further development of solar thermal utilization, have been identified and discussed. A prediction for the prospect of solar energy thermal utilization in China is also presented.     

Evaluation of solar cooker thermal performance using different insulating materials

This paper summarizes very briefly the thermal performance of solar cookers with four different insulations readily available in rural areas. A comparison of each one of these is made with the performance of glass wool. This experiment is performed to minimize the cost of the cooker with a view to enhance its widespread application in the rural Indian environment.     

Solar thermal storage systems using phase change materials

Using Fourier series expansion of the involving temperatures and the forcing parameters i.e. the solar radiation and the ambient temperature, an iterative procedure has been developed to solve the heat transfer problem with moving boundaries. Calculations specific to a typical summer and winter day in Delhi have been presented for a numerical appreciation of the developed analysis. Experiments have been performed to validate the developed theoretical analysis. A good agreement is seen between theoretical and experimental results with in the domain of the applicability of theory.     

太阳能热水-采暖联合系统

目前在欧洲流行的太阳能联合系统,是将太阳能热水技术和建筑采暖技术相结合,以提供充足的生活热水和舒适的采暖环境,文章介绍了太阳能联合系统的特点和典型系统的运行原理,以及该技术在欧盟的应用概况.     

A case study for influence of building thermal insulation on cooling load and air-conditioning system in the hot and humid regions

Ensuring the effective thermal insulation in regions, where the cooling requirement of building with respect to heating requirement is dominant, is very important from the aspect of energy economy. In this study, the influence of thermal insulation on the building cooling load and the cooling system in case of air-conditioning by an all-air central air-conditioning system was evaluated for a sample building located in Adana, based on the results of three different types of insulation (A, B and C-type buildings) according to the energy efficiency index defined in the Thermal Insulation Regulation used in Turkey. The operating costs of the air-conditioning system were calculated using cooling bin numbers. Life-cycle cost analysis was carried out utilizing the present-worth cost method. Results showed that both the initial and the operating costs of the air-conditioning system were reduced considerably for all three insulation thicknesses. However, the optimum results in view of economic measurements were obtained for a C-type building. The thickness of thermal insulation for the buildings in the southern Turkey should be determined according to the guidelines for a C-type building.     

Design and performance of a solar-powered air-conditioning system in a green building

A solar-powered adsorption air-conditioning system was designed and installed in the green building of Shanghai Research Institute of Building Science. The system contained 150 m² solar collectors and two adsorption chillers with nominal refrigeration capacity of 8.5 kW. Based on performance characteristics of the adsorption chiller, the operation mode of the solar-powered air-conditioning system was optimized by maintaining a phase shift of 540 s between the two adsorption chillers. Thereafter, the whole system realized stable operation by the balance of heat consumption and refrigeration output. From June to August of 2005, the solar-powered air-conditioning system continuously ran between 9:00 and 17:00. The operation performance of the system under representative working condition showed that the average refrigeration output of the solar-powered air-conditioning system was 15.3 kW during an 8 h operation and the maximum value exceeded 20 kW. Solar fraction for the system in summer was 71.7%, which corresponded to the designed cooling load (15 kW). Compared with the ambient temperature, it was deduced that solar radiant intensity had a more distinct influence on the performance of solar-powered air-conditioning system.     

Equilibrium thermal characteristics of a building integrated photovoltaic tiled roof

Photovoltaic (PV) modules attain high temperatures when exposed to a combination of high radiation levels and elevated ambient temperatures. The temperature rise can be particularly problematic for fully building integrated PV (BIPV) roof tile systems if back ventilation is restricted. PV laminates could suffer yield degradation and accelerated aging in these conditions. This paper presents a laboratory based experimental investigation undertaken to determine the potential for high temperature operation in such a BIPV installation. This is achieved by ascertaining the dependence of the PV roof tile temperature on incident radiation and ambient temperature. A theory based correction was developed to account for the unrealistic sky temperature of the solar simulator used in the experiments. The particular PV roof tiles used are warranted up to an operational temperature of 85 °C, anything above this temperature will void the warranty because of potential damage to the integrity of the encapsulation. As a guide for installers, a map of southern Europe has been generated indicating locations where excessive module temperatures might be expected and thus where installation is inadvisable.     

First and second law analysis of a solar assisted heat pump based heating system

We propose a model for the heating system of an ecological building whose main energy source is solar radiation. The most important component of the heating system is a vapour compression heat pump. Both the first law and the second law were used to analyse the heat pump operation. The state parameters and the process quantities were evaluated by using, as input, the building thermal load. The second law analysis emphasised that most of the exergy losses occur during compression and condensation. Preliminary results show that the photovoltaic array can provide all the energy required to drive the heat pump compressor, if an appropriate electrical energy storage system is provided.     

China building energy consumption: Situation,challenges and corresponding measures

As one of the biggest parts of total national energy consumption (TNEC), building energy consumption (BEC) catches public eyes and has been regarded as a crucial problem of the current society. For the past 20 years, BEC in china has been increasing at a high speed. To curb the rapid growing of BEC, china has enforced and implemented a series of policies. These include enforcing BEC constraints on new building projects, promoting more environment friendly building designs, establishing a more sophisticated legislation for building energy conservation, and increasing the total budget in the area of BEC control. This article analyzed china BEC situation and the challenges. As the main point, the measures required by China government to improve building energy efficiency were introduced as well.     

Utilizing wind and solar energy as power sources for a hybrid building ventilation device

Wind and solar energy are currently used to power many building ventilation devices. Such devices rely exclusively on either solar or wind energy, which limits their usefulness. A low-cost hybrid ventilation device that utilizes both wind and solar energy as power sources was designed to overcome some of the shortcomings of these devices. Wind tunnel testing conducted at the aerodynamics laboratory of the University of New South Wales revealed that the hybrid device had improved operational and performance benefits compared with conventional commercial roof top ventilators, particularly at zero to low wind speeds. This represents a significant step forward and will have an immediate impact in promoting the use of clean energy for the purposes of building ventilation.     

Calculation procedure of the shading factor under complex boundary conditions

Together with the evolution of buildings and systems, energy assessment models have become more and more detailed, requiring a precise evaluation of the building loads and gains.For an accurate analysis of solar heat gains, technical standards introduce an external shading reduction coefficient of the incident solar radiation, called shading factor. Its value is provided for simple geometries, which are usually not suitable to properly describe a real environment. In addition, the relations adopted to evaluate the shading factor are based on simplified hypotheses, which cause non-negligible errors when compared to more complex algorithms.The objective of this study is the development of a calculation procedure of the shading factor under complex boundary conditions. The algorithms have been implemented in a software tool written in Matlab language. It can provide for the value of the shading factor on a generically oriented and tilted surface. After setting the site and the time for the simulation, generic-shaped windows can be modelled. The external environment, which can be imported from DXF files, can include a horizon profile, generic-shaped obstructions and vegetation. The calculation can be performed for every sky condition: clear, average or generic. In addition, the simulation can be run to obtain instantaneous, daily average or monthly average shading factor values.     

Transient performance of closed loop solar water heating system with heat exchanger

The present paper deals with an analysis of a forced circulation closed loop solar water heating system; withdrawal of hot water of constant flow rate from a storage tank through a heat exchanger is considered. The effect of flow rate and heat exchanger length on the performance has also been discussed for a typical set of parameters and for a typical cold day in Delhi (26 January 1980).