Category Archives: EuroSun2008-4

Cross ventilation

Cross ventilation consists of forcing air circulation through the entire structure of the building and not only in the different separate rooms. The air intake and its outflow should be placed at different levels of the building’s structure in order for the fresh air to be directed towards its internal space. There are many examples of how double fa9ades are integrated into the general strategy of cross ventilation of the building.

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One example is the GSW office building in Berlin (designed by Sauerbruch Hutton Architects), which has a narrow, oblong shape [1]. The double facade is applied to the long western wall. The space between the layers is not divided in any way and it acts like a powerful ventilation channel. The fresh air enters into the building through windows in the single-wall eastern facade. Subpressure in the western part of the double-glazed facade forces the air to move horizontally and sucks it outside (fig.3) with the additional support from a disc-shaped element suspended over the roof of the building.

Подпись: Fig.4 Scheme of air circulation inside the building Fig.3 Scheme of cross ventilation across the width of the building (left) and vertical cross-section though the upper part of the building with an aerodynamic element, which increases subpressure in the area inside the double facade.

Another example of using a double facade for the ventilation of buildings is a concept office building in London, which was elaborated as part of a research project „Green Building" (designed by J. Kaplicky,

A. Levete, Ove Arup&Partners) [1]. It has an unusual ‘egg-shaped" form, which is suspended over the ground on a tripod. The entire external surface consists of two layers.

Fresh air enters through intakes located at the bottom, rises to the top and enters office space, where it leaves the building through a

void space of the facade, which functions as an air evacuation duct (fig.4).

image053Подпись:One of the well-known examples of using double facades to take advantage of natural air flows within the structure of the building comes from the Commerzbank in

Frankfurt (designed by Foster&Partners) [3]. The inter-facade void together with the internal atrium and spiral-shaped winter gardens created a system of buffer zones in which air circulates, ventilating and regulating

temperature within the entire structure of the building (fig.5).

Renovation concepts for saving 75% on total domestic energy consumption

F. G. H. Koene 1* and B. Knoll 2

1 Energy research Centre of the Netherlands ECN, Department of Energy in the Built Environment,

P. O. Box 1, 1755 ZG Petten, The Netherlands

2 TNO Building Research, P. O. box 49, 2600 AA Delft, NL
Corresponding Author, koene@ecn. nl

Abstract

In the RIGOUREUS project, ECN, TNO, TU Delft end DHV cooperate to develop innovative and affordable renovation concepts for terrace dwellings in The Netherlands, aiming at reducing their total (primary) energy consumption by 75%. A key aspect in the realisation of this target is minimisation of heat losses and maximisation of using solar heat. The basis for the concepts to be developed therefore is the Passive House concept and a solar collector in combination with additional measures.

The potential of integral renovation concepts based on maximising the amount of passive and active solar energy is explored, addressing the reduction of space heating and DHW as well as the reduction of domestic electricity consumption. A number of additional measures are presented, in particular aimed at decreasing electricity consumption in order to achieve the energy target.

Keywords: Renovation, 75% reduction primary energy, integral concept.

1. Introduction

The energy consumption in the built environment accounts for approximately one third of the total energy consumption in The Netherlands. The introduction of the Energy Performance Coefficient EPC in The Netherlands in 1998 as a mandatory requirement for new buildings has contributed considerably to the reduction of the energy consumption of new dwellings. However, little effort has been undertaken so far for existing buildings in this respect.

In the RIGOUREUS project, ECN, TNO, TU Delft and DHV develop innovative renovation concepts aiming at a reduction of 75% of the total (primary) energy consumption for Dutch terrace dwellings. A key aspect in the realisation of this target is minimisation of heat losses and maximisation of the solar contribution, while reducing the building related and user related electricity demand. The basis for the concepts to be developed is the Passive House concept [1], minimising the energy demand for space heating, in combination with a solar thermal collector to reduce the energy demand for DHW. Even though these concepts are well known in German speaking countries, several factors have prevented widespread application in the Netherlands, such as: fear of the unfamiliar, the typical Dutch building practice and economical considerations. Nevertheless, it is regarded as a necessary starting point for energy ambitious renovation concepts.

Different faces of the sun

“The sun has two different faces. The kind face of the sun appears in cold times; and its unkind face appears in hot times. In according to the properties of each location, kind and unkind faces of the sun differ from place to place, these local faces of the sun more than whatever depend on two parameters: 1st, the intensity of direct and diffused solar radiation in each moment; 2nd, the amount of need to shade or shine in according to the difference between comfortable temperature and outdoor temperature in each moment. [1, 61-91] & [2,1]”

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Fig. 2. Defining kind and unkind faces of the sun (desirability/undesirability of direct radiation) in the city of Yazd[31.5N, 54.2E] using 21°C as the base: 0.01 * radiation received x (21°C — outdoor temperature)

*

However other parameters such as wind and humidity have important roles in comfort condition, we decide not to apply them here to see the major effect of parameters of position of the sun, its total radiation and the changes in temperature through the day and in each month.

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Fig. 3. Different faces of the sun in different cities of Iran

 

In Ramsar[36.9N, 50.7E] cloudy weather and low changes in temperature from the sunrise to the sunset and through the year is the reason why the level of kind and unkind faces of the sun is low. Hamedan[34.8N, 48.6,E] and Tabas[33.6N 56.9E] are almost on the same latitude but Hamedan has cold climate and Tabas is hot. Shiraz[29.7N 53E] has two hot and cold conditions so in this city the kind and unkind faces of the sun has high levels.

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Long-term measurements of transmittance

Подпись: 8
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Long-term measurements of the solar transmittance of the two glasses were carried out in the outdoor test facility mentioned in section 2. Measurements were carried out in the test period April 30, 2008 — August 8, 2008. Due to problems with the measuring equipment measurements were not carried out in the period May 23 — June 2, 2008. Measured daily values for the total and diffuse radiation on the glasses are shown in figure 5. The daily rain amounts are shown as well. Figures 6 and 7 show daily transmittances for the normal glass and for the glass with the antireflection treated surfaces. The daily transmittances are the ratios between the daily radiation transmitted through the glass and the daily radiation on the glass surface.

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Fig. 6. Measured daily transmittance for the normal glass.

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Fig. 7. Measured daily transmittance for the glass with the antireflection treated surfaces.

The measured daily transmittance for the normal glass is varied between 0.82 and 0.88, and the measured daily transmittance for the antireflection treated glass is varied between 0.89 and 0.93. For the whole test period the transmittances are 0.84 for the normal glass and 0.91 for the glass

with the antireflection treated surfaces. The transmittance is for the whole test period increased by 8%, corresponding to 7 % points, by the antireflection treatment. The daily transmittance for both glasses is relatively low in sunny days without rain. This might be caused by dirt attached to the glass surfaces. The daily transmittance for both glasses is relatively high in rainy days and in days after rainy days. This might be caused by the fact that the glasses are washed clean during rainy periods.

The measured transmittances are compared to calculated transmittances based on the measurements for the clean glasses, that are the indoor measurements of the transmittances for direct radiation and the outdoor measurements of the transmittances for diffuse radiation.

Подпись: (3) (4) The calculated hemispherical-hemispherical transmittances at a specific time are found by: Thh = ((Ey 0.85 )+((E-Ed) 0.904- (1 — tan43 jj-^j ))/E for the normal glass

Thh = ((Ey 0.93 )+((E-Ed) 0.960- (1 — tan5’1 j 1 ))/E for the glass with antireflection surfaces where E is the total irradiance on the glass, W/m2

Ed is the diffuse irradiance on the glass, W/m2 0 is the incidence angle, °

Measured and calculated daily transmittances for the two glasses are seen in figure 8. The measured daily transmittances are up to 4% lower than the calculated daily transmittances for both glasses. The difference between the measured and calculated daily transmittances is relatively large in sunny periods and relatively small in periods with and after rain. The reason is as mentioned, most likely that the glasses are washed clean during rain showers.

The ratio between the measured solar radiation transmitted through the glass and the calculated solar radiation transmitted through the glass for the whole test period is 0.98 for the normal glass and 0.97 for the glass with the antireflection treated surfaces. That is: The transmitted solar radiation is reduced by 2% for the normal glass and by 3% for the glass with the antireflection treated surfaces due to dirt and water on the glass surfaces.

Considering the measuring accuracy it is concluded that the antireflection treatment has no significant influence on how much dirt and water attached to the glass surfaces reduce the solar transmittance during a Danish summer period.

The weather might influence the conditions and therefore the measurements will be continued during the autumn 2008 and winter 2008-2009.

Fig. 8. Measured and calculated daily transmittances for the normal glass and for the glass with the

antireflection treated surfaces.

3. Conclusion

Long-term side-by-side measurements of the solar transmittance for a normal glass and a glass with antireflection treated surfaces show that the solar transmittance is increased by 8% by antireflection treatment in a Danish summer period.

The measured transmittances in the summer period is 2-3% lower than the calculated transmittances based on measurements for the clean glasses. The antireflection treatment has, in the Danish summer no significant influence, negative or positive on the transmittance reduction caused by dirt and water attached to the glass surfaces.

Nomenclature

Tgh is the directional-hemispherical transmittance at the incidence angle 0, —

rhh is the hemispherical-hemispherical transmittance, —

E is the total irradiance on the glass, W/m2 Ed is the diffuse irradiance on the glass, W/m2 0 is the incidence angle, °

References

[1] S. Furbo & L. J. Shah (2003). Thermal advantages for solar heating systems with a glass cover with antireflection surfaces. Solar Energy 74, pp 513-523.

[2] J. Birck Laustsen & K. Johnsen (2008). Udvikling af vsrktojer til at fremme energieffektiv anvendelse af solafsksrmninger. Slutrapport for ELFORSK-projekt 337-094. Department of Civil Engineering, Technical University of Denmark, report no. R-187.

Sensitivity analysis

An extensive sensitivity study explores the various possible configurations described further up (5760 combinations), as well as some alternatives with non-efficient solar protections. They are

analyzed by way of classified illustrative tables (not presented here), in terms of overheating

duration and peak temperature (free-floating case) as well as in terms of auxiliary thermal cooling

energy and peak load (back up cooling at 26.5°C). Synthetic conclusions are as follows:

• It is shown once again that in terms of energy efficiency, good solar protections is the fundamental measure for reaching of acceptable summer comfort or for reducing of cooling energy. In comparison, all the other building parameters (thermal mass, insulation, orientation) are of secondary importance.

• That being, it is easier to obtain a good summer comfort with a well insulated building. In other words, and contrary to a hasty judgment, there is total compatibility between the winter and summer objectives. That is the case because for a comfortable administrative building, the internal temperature during occupation is lower than the outside temperature, the effect of insulation turning out to be positive. This can in principle be extended to residential buildings, insofar as when at night the differential is reversed, opening of the windows allows for adequate heat exchange.

• Internal loads also play a central role and have to be kept as low as possible. In this respect, the study on the other hand did not approach the effect of management by the occupants of opening, blinds, lighting and other apparatuses, management which was supposed to be correct.

• At climatic level, significantly different results are obtained for an urban or a rural site, or for a normal or an extreme summer (of type 2003).

• For a normal summer, a rural site, a building with efficient solar protection and modest internal loads (10 W/m2), a good comfort can be guaranteed by simple night ventilation, with an air flow equivalent to the minimal hygienic rate (1.3 ach). In all the other cases, guaranteeing of the comfort (less than 100 h above 26.5°C) without auxiliary cooling is only possible with passively cooled air and higher ventilation rates.

• In this respect, evaporative cooling not only brings about the highest potential, but also the best stability in respect to summer conditions of type 2003. The effective water consumption for evaporation (in most cases less than 50 liter/m2 per summer) remains sufficiently weak not to be a concern. Not tackled in this study, the question of hygiene and moisture however should be addressed carefully.

• As an upstream complement to evaporative cooling, but in some cases also as an alternative, day/night storage systems (buried pipes or phase-shifting) often make it possible to gain to gain 1-2 additional degrees on the peak summer temperature, respectively to harvest the few tens of hours of comfort that are missing, this even for an extreme summer. Such is particularly the case when these storage systems are set up in alternate mode with direct night ventilation.

• For an 8-18 h occupation, the storage system providing with the best result clearly is the 8 h phase-shifting device. That being, the choice between a buried pipe system or a phase-shifting device will also depend on other than thermal questions: available space, intervention possibilities, costs, maturity of technologies, electric consumption, etc.

• In all the cases, the question of increased airflow requires a detailed attention regarding charge losses and electric consumption, which was not tackled in this study. In this respect, air distribution in the building usually plays a more important role than the proper storage device.

• In the case of high internal gains (>30 W/m2), auxiliary cooling turns out necessary. Implementation of above strategies then allows for considerable reduction in cooling energy, and to a lesser extent to peak power. In several cases the cooling system (especially distribution and emission) could be simpler and of less expensive than with traditional stand-alone air­conditioning, possibly allowing for moderate temperature sources, available in the environment (lake, ground).

References

[1] Ineichen P. (2006) M-ete-O, donnees climatiques estivales dans la region genevoise, valeurs moyennes et extremes. Geneve, CUEPE, Universite de Geneve (Rapports de recherche du CUEPE n° 7).

http://www. unige. ch/cuepe/html/biblio/detail. php? id=387

[2] Hollmuller P. (2002) Utilisation des echangeurs air/sol pour le chauffage et le rafraichissement des batiments : mesures in situ, modelisation analytique, simulation numerique et analyse systemique.

Geneve, Universite de Geneve, Faculte des Sciences (These, Section de physique et Centre universitaire d’etude des problemes de l’energie).

http://www. unige. ch/cuepe/html/biblio/detail. php? id=$179

[3] Hollmuller P., Lachal B. (2008) Air-soil heat exchangers for heating and cooling : dimensioning guidelines, in: Eurosun 2008, 1st Internationla Conference on Solar Heating, Cooling and Buildings, Lisbon, 7-10 October 2008. Publication prochaine.

[4] Hollmuller P. (2003) Analytical characterisation of amplitude-dampening and phase-shifting in air/soil heat-exchangers. International Journal of Heat and Mass Transfer, vol. 46, p. 4303-4317.

[5] Hollmuller P., Lachal B., Zgraggen J. M. (2006) A new ventilation and thermal storage technique for passive cooling of buildings: thermal phase-shifting, in : PLEA 2006, 23rd Conference on Passive and Low Energy Architecture, 6-8 September 2006, Geneva, Switzerland, Universite de Geneve, Vol. 1, p. 541-546.

http://www. unige. ch/cuepe/html/biblio/detail. php? id=397

[6] SIA (2007) Norme SIA 382/1 — Installations de ventilation et de climatisation — Bases generales et performances requises, Zurich, Societe suisse des ingenieurs et des architectes.

2004 2003

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Rural, dry

♦ Rural, wet-bulb

Urban, dry

—•— Urban, wet-bulb

Fig. 1: Dry and wet bulb temperature, dynamic over a hot summer weak.

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Buried pipe Thermal phase-shifting

Fig. 2: Thermal storage, dynamic over a summer week (top) and dimensioning data (bottom).

Without evaporative cooling

 

With evaporative cooling

 

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Подпись: Shift12h - Sgl Pipes20m - Sgl Direct Base

Fig. 3: Ventilation strategies and building response over a summer week (2004, urban situation).

 

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Grain size measurements

Grain size can be measured using any of the methods outlined in (a) to (e) above. The first two methods (a) and (b) are comparism methods and give results that are within plus or minus a whole grain size and so are not very accurate. The last two methods (d) and (e) are direct measurements but they also give inaccurate result. This is because their parametric reference is just a straight line which when drawn and juxtaposed against a micrograph may lead to much error in counting the number of grains intercepted by the line. At best, therefore, they can only give single parametric description of the grains. This leaves us with that of the planetric Jeffries method (i. e method (c) for the grain size measurement.

This method provides a single number estimate of all the parametric description of grain size mentioned in the introduction. Hence it provides a full description of grain size, which can be used for any structure — property correlation [2]. Before describing the method, it is necessary to present some definitions of grain sizes, which will help us to understand the Jeffries method [1, 2, 2].

Effectiveness of active solar space heating system in the dense housing area

Y. HIGUCHI1* and M. UDAGAWA2

1Visiting researchers of Kogakuin University. 1-24-2 Nishi-Shinjuku, Shinjuku-ku, Tokyo, 163-8677

higuchi. yoshiki@kurashi-desgin. jp
2Dept. Architecture, Faculty of Engineering, Kogakuin Univ.

1-24-2 Nishi-Shinjuku, Shinjuku-ku, Tokyo, 163-8677
udagawa@cc. kogakuin. ac. jp.

Abstract

The effect of the passive solar heating of a single family house built in the dense housing area was examined using the simulation program EESLISMver6. The EESLISMver6 is extended version of a generalized building energy and environment simulation tool EESLISM which has been developed by the authors. EESLISMver6 can take into consideration the shadow effects of trees and adjacent buildings. Daily total incident solar radiation for the house in city areas was decreased by 90% or more compared with the house without adjacent buildings, so that, heating load increased by 1.5 times against the base case. Therefore, the active solar heating system is expected for the low-rise house in the dense housing to compensate the decreased passive solar effect.

In this study, the total effect of solar space heating with active and passive ways are examined using the detailed system simulation. The simulation results show that active solar space heating system is especially effective in the dense housing area as expected in this study.

Keywords: solar space heating, adjacent building, heat load, simulation

1. Introduction

When considering the energy saving of residential houses, it is effective to use the solar radiation from windows for passive heating in winter. When a site for single family house is narrow, the enough incident solar radiation from the windows can not be expected due to the shadow by adjacent buildings, trees, etc. Moreover, curtain is generally closed in the daytime for privacy. Therefore, in order to realize energy saving and a comfortable life, use of active solar space heating is especially important for a house built in the dense housing area. It is because the interior of a room can be heated if there is even an incident solar radiation to a roof even when there is little incident solar radiation on windows.

In this study, the total effect of solar space heating with active and passive ways are examined using the detailed system simulation with a generalized simulation tool EESLISM ver6 [1] which can take into consideration the shadow effects of trees and adjacent buildings developed by the authors[2-4].

Solar Hot Water Systems in Architecture

As it is known, the aesthetical evaluation of the building depends on integrity and completeness of the appearance of the buildings that is constructed by properties of like mass, facade elements form, color and pattern features. So solar hot water systems effects the appearance and form, consequently the aesthetic of the building because of the efficiency needs of slope and orientation and the surface properties of collectors like color, texture and dimension. [1] Therefore, the evaluation of systems as an architectural component and consideration of aesthetic with efficiency and economy as a fact in system design have great importance for a healthy system-building relationship.

Подпись:
Today, in the context of sustainable construction the applications, that evaluates systems, as a part of the building as an aesthetical component beyond their benefit rises, on the other hand the existing solar hot water systems are still effecting the building and the city negatively with their ugly appearances in many countries.

This problem is composed of natural convention — open circulated annex systems, which users apply individually at the top of flat roofs for their specific needs, without consideration of integrity, completeness and harmony with the building. As these systems, don’t need major modifications on buildings, have simple constructions and low costs they have wide spread usage and mostly they are being manufactured and applied without any control which causes to

• Ugly appearance of the buildings,

• Low efficiencies,

• Unhygienic conditions,

• Visual pollutions and corruption of the aesthetic view in cities.

These complications, makes solar hot water systems a problem that has to be solved in concern of architecture and urban beyond their benefits and advantages. [2]

Introduction to optimal ADS handling for LESO occupants

Last but not least, some problems occurring within the examined ADS-equipped offices could be avoided by giving a short introduction on optimal ADS handling to some office occupants. Some of the problems revealed during this study (e. g. occupants feeling that their office is too dim or that they cannot find an appropriate lighting configuration) are indeed often the result of inadequate ADS handling.

2. Conclusion

Подпись: <u "я <u о Я я о Я я я я я <и Подпись: Office seems Glare Too much Too much Office seems Glare too bright. problems. light on daylight in too dim. problems workplane. office. difficult to handle.

This study clearly shows that the ADS installed within most offices of the LESO-SEB are in general very well accepted by the building’s occupants. There are, however, some issues that should be taken into consideration when installing ADS in other buildings. Our study has revealed that most of these problems are caused by temporary daylight overprovision within the offices. Figure 5 gives an overview of the main problems and quantifies how annoying these problems are to the occupants.

Figure 5: Overview of the main lighting related problems within the examined ADS-equipped office rooms. Annoyance values are in general quite low, and most problems are due to temporary daylight-overprovision, resulting from inappropriate blind configuration and blind control as well as problems with ADS handling.

It can be concluded that the annoyance of most problems revealed during our study could be drastically reduced by optimizing the blind configuration and the blind control as well as by giving introductions on how to properly handle the ADS to the building’s occupants. These findings can be of great interest to architects and engineers who plan similar systems for other buildings in the future.

References

[1] Wittkopf, S. K., Yuniarti, E. and Soon, L. K.: Prediction of energy savings with anidolic integrated ceiling across different daylight climates. Energy and Buildings 38, pp. 1120-1129, 2006.

[2] Scartezzini, J.-L. and Courret, G.: Anidolic daylighting systems. Solar Energy 73, pp. 123-135, 2002.

[3] Welford, W. T. and Wilson, R.: Non-Imaging Optics. Academic Press, New York, 1989.

[4] Courret, G., Scartezzini, Jean-Louis, David Francioli, D. and Meyer J.-J.: Design and assessment of an anidolic light-duct. Energy and Buildings 28, pp. 79-99, 1998.

[5] Courret, G., Scartezzini, J.-L.: Systemes anidoliques d’eclairage naturel. PhD thesis, Ecole Polytechnique Federale de Lausanne (Switzerland), 1999.

[6] Linhart, F. and Scartezzini, J.-L.: Efficient lighting strategies for office rooms in tropical climates. In PLEA 2007, pp. 360-367, Singapore, 2007.

[7] Altherr, R. and Gay, J.-B.: A low impact anidolic facade. Building and Environment 37, pp. 1409-1419, 2002.

[8] Eklund, N. H. and Boyce, P. R.: The development of a reliable, valid and simple office lighting survey. Journal of the Illuminating Engineering Society, v 25 n 2, pp. 25-40, 1996.

[9] Akashi, Y. and Boyce, P. R.: A field study of illuminance reduction. Energy and Buildings 38, pp. 588­599, 2006.

[10] Ramasoot, T. and Fotios, S.: Lighting for the classrooms of the future. In Lux junior 2007, Dornfeld, 2007.

[11] Gavin, G. and Deschamps, L.: Domotique — Configuration et installation d’un micro-serveur KNX « MyHomeBox ». Diploma project, EPFL, 2008.

Thermal Performance and Modelling

During the construction of the house, more than 120 thermocouples and other sensors (e. g. electricity meters, etc.) were installed for thermal performance and energy-efficiency assessment. “T” type constantan copper-nickel thermocouples with accuracy of 0.5 °C are used.

1.1. Space heating energy consumption

The envelope of the house is well insulated. Windows are triple glazed with two low-e (emissivity 0.35) coatings and 13 mm Argon-filled gaps. They have an effective thermal resistance of RSI 0.8. The solar transmittance of the windows is 36% and the visible transmittance 71% at normal incidence. The total south facing window area of the ground floor is about 13 m2, which is approximately 15% of the ground floor area. The average effective RSI values for the walls above grade and roof are RSI 6 and RSI 8, respectively. The basement walls have a thermal resistance of

RSI 4, while that of the basement floor is RSI 1.5. The wall thermal resistance values were selected following a sensitivity analysis with the building simulation software HOT2000 [9].

Currently, the house is reserved for monitoring, and sometimes public visiting, so it is not occupied. The space heating consumption recorded will be over-estimated due to the absence of internal heat gains (e. g. appliance and human body). However, with the comparison of the data between cold sunny days and cold overcast days, we can see the contributions to the reduction of space heating energy consumption from passive solar heating. For three continuous days (Fig. 2), during which BIPV/T and ventilated slab did not operate, the heating requirement was 78 kWh for Jan.12th, 60 kWh for Jan. 13th, and 96 kWh for Jan 14th. The average outdoor temperature of Jan. 12th is 5 °C higher than that of Jan. 13th, which was sunny. Another graph (Fig. 3) for Feb. 24th, a perfect sunny day, shows that passive solar space heating and small contribution from BIPV/T heating is able to bring the room temperature 4 °C higher (from 21 °C heating setpoint to almost 25 °C) during the day time even though average outdoor temperature was around 0 °C. The thermal energy stored was adequate to keep the room air temperature above setpoint until 3:00 am of the next day when night-time outdoor temperature was around -5 °C.

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Fig. 2. Temperature and solar radiation profiles for three mild cold winter days.

 

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Fig. 3. Temperature and solar radiation profiles for two cold winter days.

 

1.2. BIPV/T system

The system was designed to cover one continuous south-facing roof surface for aesthetic and improved roof hygrothermal performance. A 3 kW PV system was installed in the house. It consists of 22 Unisolar PVL-136 laminates attached to the metal roofing (each panel is rated at 136

Подпись: Building Подпись: Back Подпись: Top

W for a total of 22×136 W = 2992 W). The electricity generated by the BIPV system as determined by RETScreen [10] is 3420 kWh/yr for a 30° slope. A gap is created between the metal roofing and the sub-layer behind them as shown in Fig. 4. Outdoor air is used as the heat transfer fluid in an open loop system so as to keep the temperature of the PV panels as low as possible, thus increasing their electricity production. Solar-heated BIPV/T air is used for domestic hot water heating, clothes drying, or VCS thermal mass heating in order of priority.

Fig. 4. Thermocouples measuring back surface, air, and top surface temperatures at different sections.

Air temperatures are measured at all the 6 locations indicated in Fig. 4. Top surface temperatures are measured at all locations except location 1. Back surface temperatures are measured only at location 2, 3, 4, and 5. The thermocouple for top surface temperature is fastened on the nearby wood framing surface. When the top surface (metal sheet) is installed on the roof, the thermocouples firmly touch the top surface.