Sizing windows to achieve passive cooling, passive heating, and daylighting in hot arid regions

The study aims to demonstrate a process for sizing the windows of a passive solar house case study that involves a multi-decision problem. The initial design was created in an earlier stage, during which, decisions on broader issues such as building orientation, form design, and the appropriate spatial organization of the building were made. It applies a variety of methods to generate and evaluate design alternatives such as rules of thumb and LCR method for passive heating; earth cooling and cross ventilation rules of thumb for passive cooling; and dylighting factor for daylighting. At the end, the study makes preliminary performance estimates between two alternatives to choose a final solution.     

Simulation of façade and envelope design options for a new institutional building

This paper presents a simulation case study of façade and envelope preliminary design options for the new Engineering building of Concordia University in Montreal. A major principle of the analysis was to create a high quality building envelope in order to optimally control solar gains, reduce heating and cooling energy demand and reduce electricity consumption for lighting, while at the same time maintain a comfortable and pleasant indoor environment. The stated approach of the design team was to aim for an energy-efficient building, employing innovative technologies and integrating concepts such as daylighting and natural ventilation. Detailed energy simulations were therefore performed from the early design stage, in order to present recommendations on the choice of façade, glazings, shading devices, lighting control options, and natural ventilation. Integrated thermal studies, a daylighting analysis and the impact of the above on HVAC system sizing were considered. Simulation results showed that, using an optimum combination of glazings, shading devices and controllable electric lighting systems, the energy savings in perimeter spaces can be substantial. Perimeter heating could be eliminated if a high performance envelope is used. The building is currently being commissioned.     

Cost optimal analysis of heat pump technology adoption in residential reference buildings

In European Union (EU) buildings consume approximately the 40% of total primary energy. Heat pump (HP) systems have proven to be an efficient and economically viable alternative to conventional systems to provide heating and cooling services in buildings. An effective penetration of this technology in the built environment is critical to achieve the ambitious goals set by the recent EU Directives on energy efficiency and energy performance of buildings. Although this technology is very versatile, its optimal design and management are related to specific climate, operational and economic conditions. The research presented aims to evaluate the performance of technical solutions for heating and cooling in residential buildings, using a “reference building” methodology. The comparison involves performance indicators such as primary energy consumption, CO₂ emission and net present cost.The potential improvements with respect to conventional baseline solutions are assessed and the performance gap between air-source and water-source HP systems is shown referring to realistic operational and climate conditions within the Italian territory. The research suggests the possibility of reducing this performance gap by concentrating future research effort on design and control optimization.     

THE APPLICATIONS OF RENEWABLE ENERGY TECHNOLOGIES IN BUILDINGS

Considerable opportunities exist, most particularly (though by no means exclusively) in the design of new buildings, to integrate renewable energy technologies and thus reduce or even replace conventional energy sources. These technologies can include passive and active solar heating and cooling, and photovoltaic power. Such strategies to improve the energetic performance of buildings and to reduce their environmental impact will always be complemented by conservation and energy efficiency measures.

Passive heating, natural cooling and daylighting represent a spectrum of strategies whose applicability is modified by region and building type, and whose contribution varies from the modest fraction by which most buildings already benefit, to that in well-designed new buildings where the solar energy contribution may represent more than half (and in suitable cases, when combined with other solar techniques, all) of the energy conventionally required to provide comfortable thermal and visual environments. Active solar heating systems have achieved considerable maturity, and developed commercial markets already exist in a number of countries. And building-integrated photovoltaic systems promise to make significant impact within the coming decade.

This paper outlines R&D programmes undertaken within the European Communities to improve our understanding of the science and engineering of these technologies, and to advance the design and industrial adaptation necessary to bring about widespread implementation of renewable energy technologies in European buildings.     

INTEGRATED PREDICTIVE ADAPTIVE CONTROL OF HEATING,COOLING, VENTILATION,DAYLIGHTING AND ELECTRICAL LIGHTING IN BUILDINGS

The present energy consumption of European Buildings is higher than necessary, given the developments in control engineering. Optimization and integration of smart control into building systems can save substantial quantities of energy on a European scale while improving the standards for indoor comfort. Many tools are available for the simulation of one or some of the following aspects: (a) heating, cooling and indoor thermal comfort, (b) ventilation and indoor air quality, (c) daylighting, electrical lighting and light quality, (d) installations, local control and fault detection, (e) Genetic optimized Neuro-Fuzzy control. The interaction between these aspects, however, is very relevant and cannot be neglected. Therefore, an integrated software tool is required. TNO together with the University of Delft develops such an integrated tool. This paper describes the first results of the utilization of this tool and the development of an integrated, predictive, adaptive building system for indoor climate control.     

Development of feasibility approaches for studying the behavior of passive cooling systems in buildings

This study is a contribution to European projects Pascool/Joule II and Altener/Sink that deals with feasibility of passive cooling systems in Europe. The first aim of this work was to define a design methodology to evaluate natural cooling potential according to the climatic quantification criteria of the site, the cooling system performance, and comfort criteria defined by the couple of temperature and relative humidity set points. A simplified approach, based on climatic potential criteria as theoretical cooling potential index, the available potential index, the cooling need index, and the natural cooling normalized capacity, was developed. It was applied to 105 European sites for different types of evaporative cooling systems (direct and indirect), and for various temperature and relative humidity set points. During the second stage, a refined approach taking into account building characteristics and the cooling system performance, was developed. This method is based on the integration of numerical models of passive cooling systems in a thermal building software in order to consider interaction phenomena between cooling system and building. Application of this approach to one building has been done in order to assess energy consumption gain achieved by using passive cooling systems. These two complementary approaches provide helpful information dealing with the feasibility of a passive cooling technique based on comfort and energy saving criteria. They could be used by architects and building designers as helpful decision making tools during the different stages of building design.     

DAYLIGHTING TECHNOLOGIES IN NON-DOMESTIC BUILDINGS

Natural daylight is an inexpensive and very efficient light source provided that the amount of daylight entering a building is controlled according to demand. In commercial buildings electricity for lighting can be cut by 50-75% using daylighting design techniques in combination with efficient artificial lighting. New lighting control technologies and advanced computer simulation tools lo optimize large buildings makes it possible to exploit these energy savings.

Daylight is a very efficient light source, providing more light for less input of thermal energy than any other artificial light source. Efficient shading systems are now emerging systems that can control the admission of daylight to the room according to requirement, and avoid overheating. Some of these systems, such as reflective light shelves, will also contribute to a better distribution of the daylight available by redistributing some daylight to the back of the room. However, more work is needed to develop and test such combined daylight and shading systems.

The use of daylight to reduce electric lighting must be seen as an integrated part of the overall energy optimization of the building. An efficient control of the use of daylight and artificial lighting will not only reduce electricity use for lighting. Additionally, the use of electricity for ventilation and cooling can be reduced also, because the internal heat gains provocating these electricity uses are reduced. This calls for an integrated design approach to the overall energy design of the building, involving the architect and the engineer from the very beginning of the design phase.

Visual comfort of office buildings receives increasing attention, partially because of the VDU's (Visual Display Units) of the computers, that are now almost standard equipment of every work place. The performance requirements for both daylighting systems and artificial lighting systems have been sharpened, and the attention to this fact is crucial in future development of lighting systems.     

Daylighting and its effects on peak load determination

Daylighting is an important issue in modern architecture that has been characterized by the use of curtain walls in commercial buildings. In Hong Kong, the overall thermal transfer value (OTTV) calculations are mandatory requirements in the submission of building plans to control the building energy use, but daylighting credits are not included in calculating the OTTV of building envelope designs. Natural daylight helps reduce the electricity use and the associated sensible cooling load due to artificial lighting. Hence, proper daylighting designs can contribute to smaller air-conditioning system and lower the peak power demand of buildings. We use the computer simulation tool, DOE-2, to demonstrate the energy performance of a generic commercial building with different OTTV designs in terms of peak cooling plant requirement and peak building power demand due to various daylighting systems. The peak loads are determined from the simulation results. Regression techniques are conducted to correlate the incremental peak electricity use and incremental peak cooling capacity with OTTV and daylighting aperture (DA) (window-to-wall ratio (WWR) times light transmittance (LT)). Contours of equal incremental peak electricity use and incremental peak cooling plant demand for different building envelope parameters are developed. Important features for daylighting schemes are highlighted and implications for OTTV designs discussed.     

Overall and zonal energy end use in an energy conscious office building

An office building of unusual design has been monitored for more than three years. Numerous submeters allow tracking of energy end use. The building was designed to make significant use of daylighting, with some passive solar heating, and an emphasis on night ventilation cooling of thermal mass. The overall building end usages are compared to those of three zones of varying orientation, spatial character, size, and population. Insights about daylight-sensing controls of indirect electric lighting, “task heating,” and night ventilation of mass and air quality are presented.     

Characterizing uncertainty in groundwater-source heating and cooling projects in Manitoba,Canada

Uncertainty of performance is an obstacle for greater uptake of many renewable energy technologies that depend on local environmental conditions. The ability to successfully complete involving a groundwater-source heat pumps or other projects using groundwater for heating and cooling is highly dependent on local geological conditions. Use of geostatistical information on aquifer properties and analysis of previous projects in a region show some promise in assessing the risk in these projects. An example of a possible methodology is given here for open loop heat pump and other groundwater-source heating and cooling projects in Manitoba, Canada. Stochastic modeling of open loop heat pumps was able to explain the number of wells unable to produce or inject sufficient water from the aquifer, demonstrating the efficacy of this technique. This type of approach also provides insight into the viability of possible mitigation options to successfully finish projects where conditions would not have supported the original design of such systems.     

Daylight in buildings, collaborative research in the International Energy Agency (IEA Task 21)

A great number of daylighting research activities including investigations of innovative daylighting systems, lighting controls, and development of daylighting design tools are being conducted in Australia, North America, and Europe. There is a strong need for coordination and sharing of the experience from these activities, and for transformation of the achievements into practical building design guidance. International collaboration is necessary for the establishment of procedures for the characterization and evaluation of daylighting and lighting control system performance under the very diverse nature of sky conditions throughout the world, and it was on this basis that IEA Task 21 started in 1995. Task 21 is a comprehensive collaborative research effort, involving more than 40 institutions from 16 IEA countries, under the Solar Heating & Cooling Programme of the International Energy Agency. The paper reports on the work of this huge international daylighting Task, with only 12 months to go of its four-year duration, describing how the work hopefully will influence on future building design.     

On-site performance of electrochromic glazings coupled to an anidolic daylighting system

This work takes benefit from two advanced building technologies through the integration of an anidolic daylighting system and an electro-chromic glazing in a building facade for achieving an optimal control of the daylight flux entering in an office room. Computer simulations of different systems configurations, based on ray-tracing techniques, were used to identify the optimal anidolic system design. Once installed in an experimental building the visual and thermal performance of the anidolic system coupled to an electrochromic glazing was assessed by way of on-site monitoring. These performances were compared to those offered by a conventional double glazing unit installed in an identical neighbouring room. An evaluation of users comfort was achieved by way of a survey involving 30 different subjects. Their visual performance during specific tasks performed on a VDT screen and/or on a sheet of paper was used to compare the lighting conditions. The main results of this detailed experimental study, showing the capability of such a combined daylighting system to control the daylight flux entering a working space, are presented in this paper.     

A user-friendly procedure to visualize the hourly quantitative performance of daylighting systems

The paper reports on the academic experience of teaching daylighting to undergraduate architectural students. The case of teaching daylighting in the architectural professional program at Oklahoma State University is used as a case study. The paper provides a brief survey of the existing design-assisting tools and methods often used, in architectural education, to design and evaluate daylighting systems. These tools are the ones normally found in textbooks that are used to teach regular and/or advanced environmental control courses. As a result of the experimentation with the use of such handy methods in the architectural design studio, a limited benefit was observed. Although these tools can provide a good understanding of the issues and variables that may affect the performance of daylighting systems, students seldom use them in a design studio setting. In contrast, the suggested simplified procedure proved to be user-friendly. It was also found to be capable of visualizing the hourly performance of daylighting systems, and consequently building a comprehensive understanding of the performance of daylighting systems. This hands-on procedure provides quick and meaningful evaluation that can help students to further develop their daylighting designs to meet the predefined goals.The paper does not intend to present a new method of daylighting systems design and/or evaluation. However, it will present a procedure that helped architectural students to visualize, further develop, and comprehensively understand the performance of their daylighting designs.     

Measurements of solar radiation and illuminance on vertical surfaces and daylighting implications

There is a growing concern about the rapid development of infrastructure and building projects and their likely impacts on the environment. Particular concerns have been raised about office building developments and energy consumption issues. In recent years, there has been increasing interest in using daylight to save energy in buildings. Lighting control integrated with daylighting is recognised as an important and useful strategy in terms of energy-efficient building design. It is believed that proper daylighting schemes can help reduce the electrical demand and contribute to achieving environmentally sustainable building developments. This paper presents a simple method for estimating the likely energy savings in electric lighting due to daylighting and the possible cooling penalty. Vertical solar radiation and illuminance data measurements are described. Cumulative frequency distributions of daylight availability are reported. The likely energy savings in office buildings are determined based on on–off and top-up controls, and the energy and environmental implications are discussed.     

Energy and cost analysis of semi-transparent photovoltaic in office buildings

Solar energy conversion systems and daylighting schemes are important building energy strategies to produce clean energy, reduce the peak electrical and cooling demands and save the building electricity expenditures. A semi-transparent photovoltaic (PV) is a building component generating electricity via PV modules and allowing daylight entering into the interior spaces to facilitate daylighting designs. This paper studies the thermal and visual properties, energy performance and financial issue of such solar facades. Data measurements including solar irradiance, daylight illuminance and output power for a semi-transparent PV panel were undertaken. Using the recorded results, essential parameters pertaining to the power generation, thermal and optical characteristics of the PV system were determined. Case studies based on a generic reference office building were conducted to elaborate the energy and cooling requirements, and the cost implications when the PV facades together with the daylight-linked lighting controls were being used. The findings showed that such an integrated system could produce electricity and cut down electric lighting and cooling energy requirements to benefit the environmental, energy and economic aspects.     

A review for absorbtion and adsorbtion solar cooling systems in China

In the past decades, solar water collectors were installed for the main purpose of preheating domestic hot water or to cover a fraction of the space heating demand in China. However, solar cooling systems were constructed just for demonstration purposes. Since the building of the first solar-powered absorption cooling system in Shenzhen in 1987, there have been over 10 additional solar cooling demonstration projects constructed. In this paper, the most representative five projects including both absorption and adsorption cooling systems are introduced and summarized. From the demonstrations, solar absorption cooling systems have been shown to be more suitable for large building air-conditioning systems. Comparatively, solar adsorption cooling systems are more promising for small size air-conditioning systems. In order to attain high utilization ratio, it is highly recommended to design solar-powered integrated energy systems in public buildings. In addition, highly efficient heat pumps are considered as the most appropriate auxiliary heat sources for solar cooling systems, for the purpose of all-weather operation. In the 11th Five year research project (duration 2006–2010), solar cooling technologies will be further investigated to achieve a breaking through in the integration of solar cooling systems with buildings.     

天然采光对建筑能耗影响的研究

在定性分析天然采光对建筑能耗影响的基础上,以一天窗建筑为研究对象,利用eQUEST能耗模拟软件为工具,分析了结合照明控制的天窗采光对夏季供冷峰值负荷及建筑各用能项如照明、供冷、供热的能耗影响,探讨了天窗透光率、照明密度、照明控制方式对建筑能耗的影响,并针对不同气候地区的典型城市探讨了昼光照明的气候差异性。     

Modelling Complex Fenestration Systems using physical and virtual models

Physical or virtual models are commonly used to visualize the conceptual ideas of architects, lighting designers and researchers; they are also employed to assess the daylighting performance of buildings, particularly in cases where Complex Fenestration Systems (CFS) are considered. Recent studies have however revealed a general tendency of physical models to over-estimate this performance, compared to those of real buildings; these discrepancies can be attributed to several reasons. In order to identify the main error sources, a series of comparisons in-between a real building (a single office room within a test module) and the corresponding physical and virtual models was undertaken. The physical model was placed in outdoor conditions, which were strictly identical to those of the real building, as well as underneath a scanning sky simulator. The virtual model simulations were carried out by way of the Radiance program using the GenSky function; an alternative evaluation method, named Partial Daylight Factor method (PDF method), was also employed with the physical model together with sky luminance distributions acquired by a digital sky scanner during the monitoring of the real building. The overall daylighting performance of physical and virtual models were assessed and compared. The causes of discrepancies between the daylighting performance of the real building and the models were analysed. The main identified sources of errors are the reproduction of building details, the CFS modelling and the mocking-up of the geometrical and photometrical properties. To study the impact of these errors on daylighting performance assessment, computer simulation models created using the Radiance program were also used to carry out a sensitivity analysis of modelling errors.The study of the models showed that large discrepancies can occur in daylighting performance assessment. In case of improper mocking-up of the glazing for instance, relative divergences of 25-40% can be found in different room locations, suggesting that more light is entering than actually monitored in the real building. All these discrepancies can however be reduced by making an effort to carefully mock up the geometry and photometry of the real building. A synthesis is presented in this article which can be used as guidelines for daylighting designers to avoid or estimate errors during CFS daylighting performance assessment.     

Design of a solar collector for year-round climatization

Solar heating systems in buildings have increasingly been studied in the past two decades. In several applications the primary energy demand is now for both heating and cooling, and modern solar collectors should be designed to provide climatization during the whole year. Solar systems are seldom applied in Europe, and large buildings, such as office buildings and schools, continue to be built with mechanical ventilation systems.The study presented in this paper is part of a European XVII Thermie project entitled “Pilot project for photovoltaic, energetic and biohousing retrieval in a school”, whose aim was to install a photovoltaic plant and solar air collectors coupled with a sun breaker structure at a scientific high school in Umbertide, in central Italy.This paper describes the research and development activities concerning a solar air collector suited for winter heating and summer ventilation, which was installed at the high school. The collector physical and numerical modelling of heat transfer and fluid flow in winter operation is presented. The system performance has been estimated as a function of different parameters in order to provide a tool for the design process. Furthermore, the climate in the area has been simulated through the available experimental data, and the system behavior under these conditions is presented.The collectors were installed at the scientific high school in Umbertide in spring 2001. Summer ventilation cooling is under testing and an experimental test period is foreseen next winter to validate the design of the collectors and their performance.     

Performance of a coupled cooling system with earth-to-air heat exchanger and solar chimney

Buildings represent nearly 40 percent of total energy use in the U.S. and about 50 percent of this energy is used for heating, ventilating, and cooling the space. Conventional heating and cooling systems are having a great impact on security of energy supply and greenhouse gas emissions. Unlike conventional approach, this paper investigates an innovative passive air conditioning system coupling earth-to-air heat exchangers (EAHEs) with solar collector enhanced solar chimneys. By simultaneously utilizing geothermal and solar energy, the system can achieve great energy savings within the building sector and reduce the peak electrical demand in the summer. Experiments were conducted in a test facility in summer to evaluate the performance of such a system. During the test period, the solar chimney drove up to 0.28 m³/s (1000 m³/h) outdoor air into the space. The EAHE provided a maximum 3308 W total cooling capacity during the day time. As a 100 percent outdoor air system, the coupled system maximum cooling capacity was 2582 W that almost covered the building design cooling load. The cooling capacities reached their peak during the day time when the solar radiation intensity was strong. The results show that the coupled system can maintain the indoor thermal environmental comfort conditions at a favorable range that complies with ASHRAE standard for thermal comfort. The findings in this research provide the foundation for design and application of the coupled system.