Evaluation of an Active Building Envelope window-system

Active Building Envelope (ABE) systems are a new enclosure technology which integrate photovoltaic (PV) and thermoelectric (TE) technologies. In ABE systems, a PV-system transfers solar energy directly into electrical energy, which can be used to power a TE heat-pump system. ABE-technologies allow for the development of thermal enclosure systems that have the ability to regulate their temperature (cooling or heating) by interacting with the sun. Applications include various enclosures that require thermal control, including building enclosures. This study considers the performance of the overall prototype ABE window-systems, and also includes the PV systems. This paper reports experimental results to establish the efficiency of the ABE system prototype. Computational analysis based upon PV modeling theories are carried out to simulate the performance of the PV system directly connected to a series of TE modules. The number and type of electrical connections for the TE modules is discussed in order to pursue the maximum power point for PV operation.     

Design strategy for low-energy ventilation and cooling within an urban heat island

Natural ventilation is a proven strategy for maintaining thermal comfort in non-domestic buildings in the UK. The energy consumption and thus the carbon dioxide emissions that contribute to global warming are lower than in conventional air-conditioned buildings. However, the ambient temperatures in the UK have risen over the last decade and new climatic data for use in the design of naturally ventilated buildings has been published. Using these data and dynamic thermal modelling, it is shown that passive stack ventilation alone was unlikely to maintain summertime comfort in a proposed University College London building within an urban heat island. The stack ventilation strategy was evolved by the introduction of passive downdraught cooling. This low-energy technique enables cooled air to be distributed throughout the building without mechanical assistance. The underlying principles of the technique were explored using physical models and the anticipated performance predicted using thermal modelling. The architectural integration is illustrated and the control strategy described. The resulting building is believed to be the first large-scale application of the passive downdraught cooling technique; construction began in late 2003.     

Design strategy for low-energy ventilation and cooling within an urban heat island

Natural ventilation is a proven strategy for maintaining thermal comfort in non-domestic buildings in the UK. The energy consumption and thus the carbon dioxide emissions that contribute to global warming are lower than in conventional air-conditioned buildings. However, the ambient temperatures in the UK have risen over the last decade and new climatic data for use in the design of naturally ventilated buildings has been published. Using these data and dynamic thermal modelling, it is shown that passive stack ventilation alone was unlikely to maintain summertime comfort in a proposed University College London building within an urban heat island. The stack ventilation strategy was evolved by the introduction of passive downdraught cooling. This low-energy technique enables cooled air to be distributed throughout the building without mechanical assistance. The underlying principles of the technique were explored using physical models and the anticipated performance predicted using thermal modelling. The architectural integration is illustrated and the control strategy described. The resulting building is believed to be the first large-scale application of the passive downdraught cooling technique; construction began in late 2003.     

Theoretical performance assessment of an integrated photovoltaic and earth air heat exchanger greenhouse using energy and exergy analysis methods

In this paper, a simplified mathematical model develops to study round the year effectiveness of photovoltaic/thermal (PV/T) and earth air heat exchanger (EAHE) integrated with a greenhouse, located at IIT Delhi, India. The solar energy application through photovoltaic system and earth air heat exchanger (EAHE) for heating and cooling of a greenhouse is studied with the help of this simplified mathematical model. Calculations are done for four types of weather conditions (a, b, c and d types) in New Delhi, India. The paper compares greenhouse air temperatures when it is operated with photovoltaic/thermal (PV/T) during daytime coupled with earth air heat exchanger (EAHE) at night, with air temperatures when it is operated exclusively with photovoltaic/thermal system (PV/T) and earth air heat exchanger (EAHE), for 24 h. The results reveal that air temperature inside the greenhouse can be increased by around 7-8 °C during winter season, when the system is operated with photovoltaic (PV/T), coupled with earth air heat exchanger (EAHE) at night. From the results, it is seen that the hourly useful thermal energy generated, during daytime and night, when the system is operated with photovoltaic (PV/T) coupled with earth air heat exchanger (EAHE), is 33 MJ and 24.5 MJ, respectively. The yearly thermal energy generated by the system has been calculated to be 24728.8 kWh, while the net electrical energy savings for the year is 805.9 kWh and the annual thermal exergy energy generated is 1006.2 kWh.     

Energy analysis of the personalized ventilation system in hot and humid climates

Personalized ventilation (PV) is an individually controlled air distribution system aimed at improving the quality of inhaled air and the thermal comfort of each occupant. Numerous studies have shown that PV in comparison with traditional mechanical ventilation systems may improve occupants’ health, inhaled air quality, thermal comfort, and self-estimated productivity. Little is known about its energy performance.In this study, the energy consumption of a personalized ventilation system introduced in an office building located in a hot and humid climate (Singapore) has been investigated by means of simulations with the empirically tested IDA-ICE software. The results reveal that the use of PV may reduce the energy consumption substantially (up to 51%) compared to mixing ventilation when the following control strategies are applied: (a) reducing the airflow rate due to the higher ventilation effectiveness of PV; (b) increasing the maximum allowed room air temperature due to PV capacity to control the microclimate; (c) supplying the outdoor air only when the occupant is at the desk. The strategy to control the supply air temperature does not affect the energy consumption in a hot and humid climate.     

Elaboration of global quality standards for natural and low energy cooling in French tropical island buildings

Electric load profiles of tropical islands in developed countries are characterized by morning, midday and evening peaks arising from an all year round high power demand in the commercial and residential sectors, due mostly to air-conditioning appliances and bad thermal conception of the building.To face this problem, the work presented in this paper has led to the realization of a global quality standard for energy saving and thermal comfort. This quality standard is obtained through optimized bioclimatic urban planning and architectural design, the use of passive cooling architectural components, natural ventilation and energy efficient systems. The methodology consisted of the study of typical dwellings with the use of a thermal and airflow software (CODYRUN). The simulations were carried out on the constituent components (roof, walls, windows) and on natural ventilation, in such a way as to estimate the influence of some technical solutions (insulation, horizontal shading, window dimension etc . . .) on each component in terms of thermal comfort and energetic performances.Throughout 1996, these technical solutions have been implemented in 280 new pilot dwelling projects.     

空冷型自动追光百叶帘式光伏窗的应用研究

简述了国内外光伏技术在建筑窗体上的研究及应用现状,设计了一种自动追光百叶帘式光伏窗,将薄膜太阳能光伏片取代传统百叶帘中的百叶并内置于中空双层窗中,调节室内采光量的同时还能获得电能收益。通过光敏元件的控制使其具有追踪太阳光的能力,光伏百叶倾角的调节过程将形成扰流,加速空冷散热,进而提高光电转换效率。此外,利用不同的工作模式将散热量与室内外进行热量交换,进一步提升了光伏的发电效率,极大降低了室内建筑能耗,在建筑环境与能源应用领域拥有着广大的市场前景。     

Radiant floors integrated with PCM for indoor temperature control

The control of indoor thermal comfort in buildings through thermal inertia during the summer season plays a fundamental role in the design of energy efficient buildings, especially in the Mediterranean climate. In fact, lightweight, highly insulated buildings cannot provide the necessary mass to buffer thermal gains. Phase change materials (PCM) have been used to provide lightweight building components with the required thermal inertia without increasing their overall mass. So far the integration of PCM into lightweight piped radiant floors for the control of thermal comfort during summer cooling regimes has not been investigated. This paper reports the development of a lightweight piped radiant floor prototype with an integrated PCM layer aimed at buffering internal gains at constant temperature during summer cooling regimes without affecting its winter warming capacity. Both the construction of the laboratory specimens and the development of the optimized finite element models are detailed and the assessment of the floor performance in a simulated room is discussed.     

Towards global benchmarking for sustainable homes: an international comparison of the energy performance of housing

Over the past 15 years, house building standards across the western world have begun to address ecologically sustainable development (ESD) principles. Amongst the range of environmental sustainability issues arising from housing construction and occupation, the energy demand for heating and/or cooling to maintain thermal comfort has the longest history and is most widespread in policy and regulation. Since energy in our homes is mainly fossil-derived, a key issue is global climate change impacts. Since greenhouse gas emissions can be emitted in various locations across the globe with similar results, it follows that a given greenhouse gas emission arising from residential space heating and cooling has approximately equal impact, irrespective of the location of the building. These emissions are therefore an appropriate candidate for benchmarking internationally, yet there have been few attempts to undertake this activity. This paper reports on a study undertaken in Australia which compares the thermal energy performance of housing in the United States, Canada, UK and Australia. The comparison is based on energy ratings of over 50 house designs from the comparison countries. Each design was assessed as being current and verified as complying with rather than significantly exceeding local regulatory requirements. Issues in design of both the buildings and the modelling tool used are highlighted, and the results are presented. Conclusions are drawn on the reasons for wide variations in thermal energy performance, the implications for benchmarking, and the case for globally consistent housing environmental performance policies and regulation.     

Energy and comfort performance of thermally activated building systems including occupant behavior

In building simulations it is common practice to use standardized occupant behavior and internal gains. Although this is a valid approach for designing systems, the probabilistic nature of these boundary conditions influences the energy demand and achieved thermal comfort of real systems. This paper analyzes the influence of occupant behavior on the energy performance and thermal comfort of a typical office floor equipped with a thermally activated building system (TABS). A multi-zone TRNSYS model with 10 adjacent zones per orientation for a typical moderate Belgian climate is set up. First, the energy performance and thermal comfort of thermally activated building systems (TABS) are compared with the performance of idealized cooling with standardized user behavior. TABS are able to deliver good thermal comfort but show to have a higher energy demand. Secondly, probabilistic occupant behavior was implemented in the TABS simulations. The influence of the occupancy rate, the shading device use and switching of the lights are analyzed by defining user profiles. It is shown that occupant behavior may have an important influence on the cooling demand and thermal comfort. However, as long as good solar protection is foreseen and operated in a correct way, TABS are able to cope with different user behavior modeled in this paper. In this case, normal daily stochastic processes do not considerably affect the cooling demand and thermal comfort during summer.     

太阳能聚光光伏光热(CPV/T)系统研究

聚光光伏光热(CPV/T)系统将太阳电池与集热器相结合,通过聚光和跟踪太阳提高太阳辐照强度,增加太阳电池的单位面积发电量,集热器在冷却太阳电池的同时回收多余热能,获得电能和热能双重收益。本文研究聚光比、太阳电池效率、组件中电池片的有效覆盖率、热传导率等因素对系统性能的影响。     

1st Environmental conference of Thessaly region, 8–10 September 2012, Hotel Skiathos Palace,Koukounaries, Skiathos Island,Greece

This study was conducted with the aim to assess the potential performance of a photovoltaic thermal mechanical ventilation heat recovery (PV/T MVHR) system. The device is currently considered for the application to the Z-en house project undertaken by Scottish homebuilder. The house’s whole energy demand was calibrated based on the UK Government’s standard assessment procedure for energy rating of dwellings, while the PV/T performance was estimated using an ‘EESLISM’ energy and environmental design simulation tool developed by Kogakuin University. This study concluded that PV generates heat, which makes the fresh air running under the PV roof 10–15?°C warmer than the outside temperature even during the Scottish winter and this warm air extracted from roof-integrated PV modules can be used to help reduce the domestic space-heating demand. Thus, the building-integrated PV/T MVHR system was considered as one of the effective means to assist the net zero energy operation of housing in cool and cold climates, whose dominant domestic energy comsumption derives from space heating.     

Utilizing modulating-temperature setpoints to save energy and maintain alliesthesia-based comfort

ABSTRACT

One area with the greatest potential for energy savings in buildings is heating and cooling. However, it is often argued that any energy-saving techniques should not have a negative impact on comfort for inhabitants. This is where the concept of alliesthesia comes into play. This paper examines the impact of utilizing modulating temperature setpoints to take advantage of the pleasure experienced through change. Simulations were conducted using EnergyPlus to explore the potential for energy savings. It was found that savings of up to 5–15% could be achieved by modulating indoor temperatures in cooling applications. However, modulating temperature setpoints resulted in larger energy usage than constant setpoints in heating applications. Results from human comfort experiments show that modulating temperatures could lead to greater thermal pleasure than a constant temperature environment for cooling situations due to a resetting of the thermal comfort achieved when the indoor temperature is decreased. However, the same comfort benefits are not shown for heating situations. Nonetheless, the simulations and the comfort experiments together show potential for both energy savings and increased human comfort levels in cooling applications.     

Thermal comfort and energy saving of a personalized PFCU air-conditioning system

This paper evaluates the performance of a personalized air-conditioning system, namely an innovative partition-type fan-coil unit (PFCU), against that of a central air-conditioning system, in terms of their thermal comfort provided and cooling energy consumed. For a cooling load given, it is found that the thermal comfort index (PMV) resulted from the personalized system is always lower than that from a central system. Also, the PMV-curve of the personalized system responds to the loads faster. The experimental results indicate that the personalized system, as compared to the central system, can shorten the operation time for the same level of thermal comfort required and save up to 45% of the energy consumed by the central system. As regards thermal comfort, the experiment with a thermal manikin substrates the PFCU design for its considerable reduction of the cold draft.     

Evaluation of a PV-integrated building application in a well-controlled outdoor test environment

This paper presents the assessment of experimental data for electrical and thermal performance evaluation of photovoltaic (PV) systems integrated as cladding components into the building envelope, giving input to modelling and analysis work. From the experience gained in several EU research projects, an improved design for a common Test Reference Environment (TRE) has been developed. This specific design of the PV module and TRE makes it possible to study, through electrical and thermal energy flow analysis, the effect on electrical performance of using different materials for PV modules and the construction design of claddings. The results for a glass–glass PV module with forced ventilation are presented.     

Implementation and experimental survey of passive design specifications used in new low-cost housing under tropical climates

This paper deals with a global approach in the thermal and airflow design of new dwellings and specially low-cost housing built in the French tropical overseas islands. The sizing of passive cooling techniques has been evaluated thanks to a simulation code. The solutions have been edited in a reference document that serves as work-base for the design of dwellings developments in the French tropical territories. An experimental and sociological survey has been carried out over two years (from 1998 to 1999) in order to validate the impact of these passive cooling specifications on the comfort of tenants and to have an immediate feedback and correct the solutions if necessary. The paper presents the implementation, the experimental survey and the results for the two first housing projects built according to the passive design specifications. This step is important because the aim of the public utilities is to expand the ECODOM specifications on a much broader scale and to prepare to future housing thermal regulations. The results indicated that the solar protection of the roof remains one of the main points in the thermal design of buildings in a tropical climate as well as the natural ventilation. The sociological study showed that the tenants were globally satisfied with their flat as far as the thermal aspects are concerned. However, dissatisfaction resulted from the bad acoustic design of the flats.     

Impact of adaptive thermal comfort criteria on building energy use and cooling equipment size using a multi-objective optimization scheme

Recently adaptive thermal-comfort criteria have been introduced in the international indoor-climate standards to reduce the heating/cooling energy requirements. In 2008, the Finnish Society of Indoor Air Quality (FiSIAQ) developed the national adaptive thermal-comfort criteria of Finland. The current study evaluates the impact of the Finnish Criteria on energy performance in an office building. Two fully mechanically air-conditioned single offices are taken as representative zones. A simulation-based optimization scheme (a combination of IDA-ICE 4.0 and a multi-objective genetic-algorithm from MATLAB-2008a) is employed to determine the minimum primary energy use and the minimum room cooling-equipment size required for different thermal comfort levels. The applicability of implementing energy-saving measures such as night ventilation, night set-back temperature, day lighting as well as optimal building envelope and optimal HVAC settings are addressed by investigating 24 design variables. The results show that, on average, an additional 10 kWh/(m² a) primary energy demand and a larger 10 W/m² room cooling-equipment size are required to improve the thermal comfort from medium (S2) to high-quality (S1) class; higher thermal comfort levels limit the use of night ventilation and water radiator night-set back options. Compared with the ISO EN 7730-2005 standard, the Finnish criterion could slightly decrease the heating/cooling equipment size. However, it significantly increases both the heating and cooling energy demand; the results show 32.8% increase in the primary energy demand. It is concluded that the Finnish criterion-2008 is strict and does not allow for energy-efficient solutions in standard office buildings.     

Impact of adaptive comfort criteria and heat waves on optimal building thermal mass control

This article investigates building thermal mass control of commercial buildings to reduce utility costs with a particular emphasis on the individual impacts of both adaptive comfort criteria and of heat waves. Recent changes in international standards on thermal comfort for indoor environments allow for adaptation to the weather development as manifested in comfort criteria prEN 15251.2005 and NPR-CR 1752.2005 relative to the non-adaptive comfort criterion ISO 7730.2003. Furthermore, since extreme weather patterns tend to occur more frequently, even in moderate climate zones, it is of interest how a building's passive thermal storage inventory responds to prolonged heat waves. The individual and compounded effects of adaptive comfort criteria and heat waves on the conventional and optimal operation of a prototypical office building are investigated for the particularly hot month of August 2003 in Freiburg, Germany. It is found that operating commercial buildings using adaptive comfort criteria strongly reduces total cooling loads and associated building systems energy consumption under conventional and building thermal mass control. In the case of conventional control, total operating cost reductions follow the cooling loads reductions closely. Conversely, the use of adaptive comfort criteria under optimal building thermal mass control leads to both lower and slightly higher absolute operating costs compared to the optimal costs for the non-adaptive ISO 7730. While heat waves strongly affect the peak cooling loads under both conventional and optimal building thermal mass control, total cooling loads, building energy consumption and costs are only weakly affected for both control modes. Passive cooling under cost-optimal control, while achieving significant total cost reductions of up to 13%, is associated with total energy penalties on the order of 1–3% relative to conventional nighttime setup control. Thus, building thermal mass control defends its cost saving potential under optimal control in the presence of adaptive comfort criteria and heat waves.     

Condenser heat recovery with a PV/T air heating collector to regenerate desiccant for reducing energy use of an air conditioning room

This paper presents an experimental test along with procedures to investigate the validity of a developed simulation model in predicting the dynamic performance of a condenser heat recovery with a photovoltaic/thermal (PV/T) air heating collector to regenerate desiccant for reducing energy use of an air conditioning room under the prevailing meteorological conditions in tropical climates. The system consists of five main parts; namely, living space, desiccant dehumidification and regeneration unit, air conditioning system, PV/T collector, and air mixing unit. The comparisons between the experimental results and the simulated results using the same meteorological data of the experiment show that the prediction results simulated by the model agree satisfactorily with those observed from the experiments. The thermal energy generated by the system can produce warm dry air as high as 53 °C and 23% relative humidity. Additionally, electricity of about 6% of the daily total solar radiation can be obtained from the PV/T collector in the system. Moreover, the use of a hybrid PV/T air heater, incorporated with the heat recovered from the condenser to regenerate the desiccant for dehumidification, can save the energy use of the air conditioning system by approximately 18%.