Modeling, design and thermal performance of a BIPV/T system thermally coupled with a ventilated concrete slab in a low energy solar house: Part 1, BIPV/T system and house energy concept

This paper is the first of two papers that describe the modeling, design, and performance assessment based on monitored data of a building-integrated photovoltaic-thermal (BIPV/T) system thermally coupled with a ventilated concrete slab (VCS) in a prefabricated, two-storey detached, low energy solar house. This house, with a design goal of near net-zero annual energy consumption, was constructed in 2007 in Eastman, Québec, Canada - a cold climate area. Several novel solar technologies are integrated into the house and with passive solar design to reach this goal. An air-based open-loop BIPV/T system produces electricity and collects heat simultaneously. Building-integrated thermal mass is utilized both in passive and active forms. Distributed thermal mass in the direct gain area and relatively large south facing triple-glazed windows (about 9% of floor area) are employed to collect and store passive solar gains. An active thermal energy storage system (TES) stores part of the collected thermal energy from the BIPV/T system, thus reducing the energy consumption of the house ground source heat pump heating system. This paper focuses on the BIPV/T system and the integrated energy concept of the house. Monitored data indicate that the BIPV/T system has a typical efficiency of about 20% for thermal energy collection, and the annual space heating energy consumption of the house is about 5% of the national average. A thermal model of the BIPV/T system suitable for preliminary design and control of the airflow is developed and verified with monitored data.     

Performance optimization of evacuated tube collector for solar cooling of a house in hot climate

Evacuating the space connecting cover and absorber significantly improves evacuated tube collector (ETC) performance. So, ETCs are progressively utilised all over the world. The main goal of current study is to explore ETC thermal efficiency in hot and severe climate like Kuwait weather conditions. A collector test facility was installed to record ETC thermal performance for one-year period. An extensively developed model for ETCs is presented, employing complete optical and thermal assessment. This study analyses separately optics and heat transfer in the evacuated tubes, allowing the analysis to be extended to different configurations. The predictions obtained are in agreement with experimental. The optimum collector parameters (collector tube length and diameter, mass flow rate and collector tilt angle) are determined. The present results indicate that the optimum tube length is 1.5 m, as at this length a significant improvement is achieved in efficiency for different tube diameters studied. Finally, the heat generated from ETCs is used for solar cooling of a house. Results of the simulation of cooling system indicate that an ETC of area 54 m², tilt angle of 25° and storage tank volume of 2.1 m³ provides 80% of air-conditioning demand in a house located in Kuwait.     

The Oxford Solar House

This paper presents preliminary results from the first nine months of monitoring the Oxford Solar House (OSH) which was built, in particular, to evaluate the potential for photovoltaics to contribute cost effectively to domestic energy supply in the UK. The house was built in a south facing site with good solar access. It has a 4kW PV system integrated into the roof structure and a 5m² solar thermal domestic hot water pre-heat. The house was designed to require a minimum of energy for heating, cooling and lighting, therefore optimizing the significance of the contribution of the solar electric supply. The performance of the PV system is presented, as well as an analysis of the whole design strategy to minimize energy loads.     

季节性蓄热太阳能地板供暖系统的性能研究

本文建立了季节性蓄热太阳能地板供暖系统的数学模型,以上海一栋别墅建筑为实例,给出了系统中蓄热水箱的平均水温变化。同时分析了太阳能集热器面积、蓄热水箱容积、建筑热损失系数及地板供暖系统每天运行时间对系统性能的影响,为该系统的优化设计提供参考。     

Sustainable energy generation processes in the deserts of solar-rich countries

A sustainable energy generation system in solar-rich countries can establish the process of desert community development in these areas. To test the validity of this hypothesis, potential assessment of deserts’ solar power is carried out. The results reveal that considerable amounts of electric power and potable water can be produced locally at these deserts sites. In this paper, the basic needs of a sizeable desert community are identified; their total energy requirements are estimated and then the capability of available solar potential to meet these energy needs is calculated. A sustainable energy generation model is devised to attain the objective of power generation and potable water production. The processes of solar power generation, desalination and storage systems are built in the proposed model. The sustainable development process is based on the utilization of renewable energy, self-contained nature of energy generation system and environment-friendly nature of power and water production.     

Modeling, design and thermal performance of a BIPV/T system thermally coupled with a ventilated concrete slab in a low energy solar house: Part 2, ventilated concrete slab

This paper is the second of two papers that describe the modeling and design of a building-integrated photovoltaic-thermal (BIPV/T) system thermally coupled with a ventilated concrete slab (VCS) adopted in a prefabricated, two-storey detached, low energy solar house and their performance assessment based on monitored data. The VCS concept is based on an integrated thermal-structural design with active storage of solar thermal energy while serving as a structural component - the basement floor slab (∼33 m²). This paper describes the numerical modeling, design, and thermal performance assessment of the VCS. The thermal performance of the VCS during the commissioning of the unoccupied house is presented. Analysis of the monitored data shows that the VCS can store 9-12 kWh of heat from the total thermal energy collected by the BIPV/T system, on a typical clear sunny day with an outdoor temperature of about 0 °C. It can also accumulate thermal energy during a series of clear sunny days without overheating the slab surface or the living space. This research shows that coupling the VCS with the BIPV/T system is a viable method to enhance the utilization of collected solar thermal energy. A method is presented for creating a simplified three-dimensional, control volume finite difference, explicit thermal model of the VCS. The model is created and validated using monitored data. The modeling method is suitable for detailed parametric study of the thermal behavior of the VCS without excessive computational effort.     

Investigation of thermal performance of a ground coupled heat pump system with a cylindrical energy storage tank

An analytical and computational model for a solar assisted heat pump heating system with an underground seasonal cylindrical storage tank is developed. The heating system consists of flat plate solar collectors, an underground cylindrical storage tank, a heat pump and a house to be heated during winter season. Analytical solution of transient field problem outside the storage tank is obtained by the application of complex finite Fourier transform and finite integral transform techniques. Three expressions for the heat pump, space heat requirement during the winter season and available solar energy are coupled with the solution of the transient temperature field problem. The analytical solution presented can be utilized to determine the annual variation of water temperature in the cylindrical store, transient earth temperature field surrounding the store and annual periodic performance of the heating system. A computer simulation program is developed to evaluate the annual periodic water and earth temperatures and system performance parameters based on the analytical solution. Copyright © 2003 John Wiley & Sons, Ltd.     

Experimental and theoretical performance of a demonstration solar chimney model—Part I: mathematical model development

The solar chimney is a natural draft device which uses solar radiation to provide upward momentum to the in-flowing air, thereby converting the thermal energy into kinetic energy. A study was undertaken to evaluate the performance characteristics of solar chimneys both theoretically and experimentally. In this paper, a mathematical model which was developed to study the effect of various parameters on the air temperature, air velocity, and power output of the solar chimney, is presented. Tests were conducted on a demonstration model which was designed and built for that purpose. The mathematical model presented here, was verified against experimental test results and the overall results were encouraging. © 1998 John Wiley & Sons, Ltd.     

A novel renewable energy-based integrated system with thermoelectric generators for a net-zero energy house

A renewable energy based integrated system is developed to meet the total energy demands of a house located off-grid, and a thermodynamic analysis through energy and exergy methodologies is conducted for analysis, evaluation, and performance assessment. The present novel multigeneration system is mainly driven through the animal residues produced at the farm house. The proposed novel system is composed of nine main units namely, a biomass combustor, photovoltaic (PV) panels, parabolic solar trough collectors, thermoelectric generators, organic Rankine cycle, electrolyzer, homogeneous charged compression ignition (HCCI) engine, absorption chiller, and reverse osmosis (RO) unit. Biomass combustor runs an organic Rankine turbine for additional power during peak loads. The exhaust of gas turbine generates cooling to meet the cooling demand of the residential area of the farm house. PV panels are incorporated to generate hydrogen through electrolyzer. A HCCI engine generates power to compensate peak load as well as charging the farming vehicles of the farm house. The RO unit with energy recovery Pelton turbine produces fresh water for farming and residential use. The advanced integration of subsystems, thermoelectric generators and efficient utilization of waste, improves significant amount of energetic and exergetic efficiencies of overall multigenerational system. The energy and exergy efficiencies are enhanced in the order of 4.8% and 6.3%, respectively, after incorporating innovative cooling system to the PV modules. The overall energy and exergy efficiencies of the proposed multigeneration system with and without thermoelectric are found to be 67.6% and 57.1%, and 68.9% and 58.4%, respectively.     

大庆地区三种类型被动式太阳房的对比分析

本文为大庆地区设计了三种常见类型的被动式太阳房.通过太阳房采暖设计的SLR法进行热工设计计算得到直接受益式、集热蓄热墙式和附加阳光间式的节能率分别为0.66、0.59和0.71,节能效果均比较好.采用太阳房在寿命期内的资金节省SAV为经济评价指标,分析计算结果表明,直接受益式被动太阳房在寿命期内的资金节省SAV为35077.06元,回收年限仅为3.19年,阐明了直接受益式被动太阳房的优选性.     

Design and performance of a roof integrated solar air heater

This paper discusses the design and construction of a roof integrated solar air heater used in a space heating system for a well insulated house located in Melbourne, Australia. The design of the house and the heat storage system is not discussed and details may be obtained elswhere [1]. The space heating system consists of an array of solar air heaters coupled to a rockbed thermal store located under the floor of the house, such that the rooms are heated by radiation and convection from the floor.     

Experimental and theoretical performance of a demonstration solar chimney model—Part II: experimental and theoretical results and economic analysis

This paper describes details of the experimental program conducted to assess the viability of the solar chimney concept. A demonstration model was designed and built and its theoretical and experimental performance was examined. Two experimental modifications were tried on the collector: (1) extending the collector base and (2) introducing an intermediate absorber. The former modification helped in enhancing the air temperature, while the latter contributed to increasing the air temperature as well as the mass flow rate inside the chimney. Both enhancements helped to increase the overall chimney power output. Theoretical and experimental performance results of this demonstration model are presented in this paper, while the mathematical model developed in Part I was used to predict the performance of much larger systems. Mathematical model results were validated by comparing them to published data on the solar chimney system built in Manzanares, Spain. Also, an economic assessment of the system costs are presented. © 1998 John Wiley & Sons, Ltd.     

Performance assessment of a paraboloid dish collector field

This article deals with performance assessment of thermal energy collection and storage subsystem of a 100-kW solar power station in the desert area of Kuwait. An energy analysis of the solar energy collection system was made accounting for various thermal loss as in the collector field. Results have been compared with the respective design and expected values. Comparison shows a substantial reduction in mirror reflectivity and an increase in piping thermal losses. These results along with the analyses are presented and discussed here.     

农村太阳能供暖住宅

以农村住宅进行太阳能供暖模拟试验得出的结论为依据,提出农村太阳能供暖住宅的设计方案:①提高农村住宅的保温隔热性能.降低建筑能耗;②要创新太阳能供暖设备,提高供暖系统的热效率;③实施太阳能与建筑一体化,使住宅热负荷与太阳能集热器的有用热量相匹配,实现农村住宅的主房间室内温度常年保持在16℃～28℃之间波动,居住舒适.     

小型太阳能热泵地板供暖系统的优化研究

建立了太阳能热泵地板供暖系统的能量分析、可用能分析数学模型,模拟了上海供暖期的气候条件,给出了系统各部件的可用能损失情况。着重从太阳能集热器并联的组数出发对系统进行了优化研究,并给出了系统供暖性能系数和可用能效率,为该系统的设计及应用提供参考。     

Solar powered induction motor-driven water pump operating on a desert well, simulation and field tests

A photovoltaic-powered water pumping system, employing an induction motor pump, capable of supplying a daily average of 50 m³ at 37-m head has been developed. The system was installed on a desert well in Jordan, where: the average solar radiation amount to 5.5 kW h/m³/day, to provide the Bedouins living in the well area with drinking water.A mathematical model to enable testing the system performance by computer simulation was developed. This model allows the representation of motor torque in function of speed (and slip) at different supply frequencies, as well as the flow rate and efficiency of the system in function of supply frequency and pumping head.Prior to its installation on the desert well, the system performance, in accordance with frequency and head, was thoroughly tested in the laboratory. As illustrated in this paper, simulation and laboratory testing results are well matched. At constant pumping head, the flow rate is proportional to the supply frequency of the motor. At constant flow rate, the pumping head is proportional to the supply frequency squared only in the range below the peak efficiency of the pump. For higher flow rate values, a special algorithm based on the experimental results could be developed.Higher system efficiency is achievable at higher frequency. It is advisable to operate the motor pump at the nominal frequency, flow rate and head corresponding to maximum efficiency.Long-term field testing of the system shows that it is reliable and has an overall efficiency exceeding 3%, which is comparable to the highest efficiencies reported elsewhere for solar powered pumps.     

一种新型单轴太阳跟踪方式

针对单轴跟踪精度较低的问题,提出一种新型单轴跟踪方式,采用"斜面+楔形体+转轴"的几何构造,只用一个转轴即可最大程度接近双轴跟踪的效果。通过几何关系推导出新型单轴跟踪方式的数学表达式,结合晴天太阳辐射模型进行仿真分析,与传统单轴跟踪方式进行对比。以北京地区为例,新型单轴跟踪方式接收的年辐射量相比传统单轴跟踪方式有一定程度的提高,比水平单轴跟踪方式提高22.7%。最后还证明,在其他纬度新型单轴跟踪方式仍优于传统单轴跟踪方式,其接收年辐射量可达到双轴跟踪的97%～99%。     

Design and performance of energy-efficient solar residential house in Andorra

This paper describes the design and building technology details of a three-storey single family house located in the Pyrenees, in Andorra. The house is owned by the first author, and has been occupied since 2004. A combination of active and passive solar energy systems and night-time electricity are used to supply the heating and cooling demands. The main goal of this paper is to provide detailed design information and an evaluation of performance. Data provided includes site information and climate, basic design options and decisions, energy saving strategies and energy end use data. The house has been in use since 2003. This allows adequate performance data to be presented and evaluated. Some general results and initial design problems are discussed.     

A novel approach to improve the performance of solar-driven Stirling engine using solar-driven ejector cooling cycle

In this paper, a novel system to enhance the performance of a solar-driven finite speed alpha-type Stirling engine is proposed and evaluated. Part of the concentrated solar energy is used to drive an ejector refrigeration system. The cooling produced in the ejector cooling cycle is used to cool the Stirling engine to enhance its efficiency. Model equations to describe the systems are proposed and solved numerically. The results indicate that the new system produces averagely 3.3 times electrical power more than the conventional one. Moreover, the proposed system improves the Stirling engine efficiency by up to 46% in comparison with 19.15% for the conventional Stirling engine under solar radiation intensity of (1 kW/m²). Also, the results showed that the solar radiation intensity and wind speed are the most influential parameters that affect the proposed system efficiency. The new system is recommended to use in desert climates where high average daily solar radiation intensity, low wind speeds, and water shortage exist. Economic analysis is carried out to determine the feasibility of the proposed system under different economic parameters. It is found that, for instance, the simple payback period is 4.64 years for the new system when the selling price of electricity is 0.35 $/kWh.     

On the study of applications of solar thermal energy for mobile homes

A great deal of work has been done in the study of applications of solar thermal energy for conventional site-built houses; however, little effort has been directed to the study of these applications for mobile homes although they account virtually for a large portion of low cost single family homes. Mobile homes are different from the conventional home and building in configuration, structure, arrangement and cost. The concept and criteria of designing a solar space heating/cooling system for mobile homes differs somewhat from that of a conventional site-built house or building. The mobile home is a low-cost housing. The solar system developed for mobile homes should be really low in cost before it can appeal to the mobile home community. This paper presents the unique characteristics of mobile homes and their impacts on the design/selection of its solar space heating/cooling system and system for supplying domestic hot water. A typical model mobile home is selected for investigation of the solar system design for four representative climatic regions (cool, temperate, hot-humid and hot-arid) of this country. Economical feasibility study is also discussed. A low-cost solar collector is suggested and its estimated performance is presented.