It turns out that in Polish climatic conditions it could be the special problem with overheating of rooms located at west side of a building. In summer west vertical surfaces (see Fig.6) receive much more solar radiation than south vertical surfaces. Taking that into account and analyzing distribution of solar irradiance on surfaces with different inclination and orientation throughout the whole averaged year the decision was made according to the final shape of the building (see Fig.1 and Fig.7 -8) [3]. The main facade has partly flatted cylindrical shape and is directed from the south — east to the south — west direction. The back side of the main building (see Fig. 7) is directed to the north (from north — east to the north — west). The EDI building consists of segments with different orientation. For the main facade, starting from the east to the west, it is as following: — 420, — 310, — 190, — 80 (main hall in the centre of the EDI building), +30, +140, +260, +370 (small

segment between EDI building and the swimming pool), +420 (the swimming pool). The roof of the EDI building is inclined at angle equal to 30o (see Fig.8) and consists of the similar segments as the vertical part of the building.

The architectural concept of the 3 storey IEB building has been developed with regard to active and passive application of solar energy. The shape of the building assures maximum gains of solar energy per year for active and passive systems. Shading elements are also included. Apart from traditional devices as blinds and building envelope elements as overhangs, the PV modules are to be applied and natural green environment (building is to be surrounded by pergolas at the front glazing facade). PV modules are to be located on the roof with slope of 300 and constitute shading elements over balconies of hotel rooms and over the main entrance — reception hall (glazed roof) in the middle of the building.

All “south” rooms at the first floor are seminar and lecture rooms. The main open space is the central hall, that can be used as a conference hall, banquet hall and exhibition area. Hotel rooms are at the second and third floor, mainly at the “south” side. The “north” side is designed as not living room space. It will include technical rooms, stores, measurement — monitoring rooms and some office rooms.

Heat will be supplied to the building by ground heat pumps, solar collectors and auxiliary biomass boiler located at the boiler room at the east side of the building (the plantation of energetic willow will be located nearby.

The IEB building is connected at the west side with the swimming pool and fitness center. Shape of a roof of the swimming pool is shown in Fig. 1 and Fig.7. The slope of the roof is 350, and the orientation is +300. The roof has been especially designed in such form to improve solar energy utilization. Solar collectors will be located at the roof and will supply heat to the swimming pool and the IEB building. Laboratory buildings are connected with the IEB building via bypasses shaded by PV panels on passes roofs. Location of all buildings and active solar systems has been analyzed taking into account the shading of the surrounding elements: natural (trees) and artificial (building in the vicinity). At present, technical concept of the Center is under development.

References

[1] D. Chwieduk, Some Aspects of Modeling the Impact of Solar Energy on the Energy Balance of a Room, Solar Energy (in print).

[2] D. Chwieduk, B. Bogdanska, Some recommendations for inclinations and orientations of building elements under solar radiation in Polish conditions, Renewable Energy Journal, 29 (2004) 1569 — 1581.

[3] D. Chwieduk, E. Kossecka, P. Murza — Mucha, Opracowanie kompleksowej koncepcji Centrum i szczegolowych zalozen do jego budowy, Raport projektu Konwersja Energii i Zrodla Odnawialne — Centrum Badawcze w Jablonnej. Zadanie II.1.

[4] D. T. Reindl, J. A. Duffie, W. A. Beckman, Evaluation of Hourly Tilted Surface Radiation Models, Solar Energy, 45 (1999) 9 -14.

The above mentioned control system was installed and tested in an experimental test cell with a south facing glazed surface. The changeable geometry of the transparent part of the test cell was achieved with an externally fixed motorized PVC roller blind controlled by a programmable logic controller (PLC) connected to a PC and an operator panel. The algorithms for the fuzzy thermal and illumination controllers were developed in the IDR BLOCK environment and were loaded in the PLC [3, 4]. For supervision, visualization and setting up of experiments a remote personal computer was used, although the communication with the PLC could also be achieved by using the operation panel. All of the obtained values and process variables were collected and stored in the PC, with an application developed especially for this purpose in Factory Link environment. The basic framework and functioning of the system is presented in Fig. 1.

The controller can be in general split into two control loops. These can function separately or, if desired, can be linked to work simultaneously. The first loop is the “illumination loop” comprising of elements or blocks, which make the roller blind alternations possible in such a way that the indoor set­point illumination is followed as closely as possible. The second is the “thermal loop” which is split in two separate controllers, one for the summer season (cooling mode) and the other for the winter season (heating mode). In the thermal loop there are also separate controllers for the functioning of electric heaters and a ventilator intended for passive cooling. Both control loops are designed as a cascade control system where fuzzy controller is used as the main controller and PID/V type controller as the auxiliary one [4]. In this way the main fuzzy controller defines roller blind position according to the external conditions and the set-point values. The PID/V controller then executes the appropriate change and position of the external roller blind.

1.1 Control loops

The thermal control loop used in the regulation system of the test chamber is the result of modelling and simulation approach. It derives from the thermal theoretical mathematical model [5, 6] executed in the MATLAB/SIMULINK environment. After numerical simulations conducted within the SIMULINK environment the controller fuzzy rules were fine-tuned through experimental work on the test chamber. The thermal loop is split into two separate fuzzy controllers dedicated to guide the position of the roller blind during summer (cooling) and winter (heating). During spring and autumn both controllers are used and act simultaneously in the determination of the position of the roller blind. The controllers are structured to closely follow the internal set point temperature parameters in correlation to the outside weather conditions. Each fuzzy controller contributes its part to the final decision on the positioning of the blind. The contributed part of the controller is determined on the basis of the difference between the internal and external air temperatures and the amount of exerted influence is derived by the evaluation function. The evaluation function is presented below:

Output_signl = (fuzzy_roll_summer/100* T_error* 0.5) + (fuzzy_roll_winter/100* (100- T_error* 0.5) — fuzzy_roll_summer (winter) is the output signal of the appropriate fuzzy controller, T_error is the temperature difference between the external measured and the internal set-point value of air temperature [7].

When the external air temperature is lower than the internal set-point temperature, only the winter controller directs the roller blind, while in the reversed case (external air temperature being higher than

the internal) both fuzzy controllers contribute to the positioning of the roller blind. Thermal control loop also regulates the actions of additional actuators (heater and ventilator) installed in the test chamber. If these are enabled, they can be used to help regulate internal temperature. Nonetheless, the position of the roller blind is always the priority action as the system strives to use more energy efficient ways of regulation.

When the internal environment of the test cell is regulated solely with the thermal loop, the illuminance control loop has no effect on the regulation process. On the other hand, if both loops were used in harmonized mode, the priority in guiding the roller blind was always given to the illuminance loop, because people are more susceptible to changes in illuminance than in temperature levels. Also the expected illumination oscillations were in the range of 1000-5000 lx and the dynamics of changes is far grater than in temperatures. All of the above reasons make illuminance a much harder quantity to regulate than temperature. When the desired levels of internal illumination are achieved, the thermal loop takes over and directs the roller blind to follow the thermal set-point profile as closely as possible within the admissible illumination set point tolerance. Because the internal ilumination is a very complex process, the control loop parameters and fuzzy rules were not developed in the same way as in the case of the thermal loop. Instead of mathematical model and numerical simulations an experimental approach with the application of expert knowledge and trial and error process was used.

2. Experiments

The tests designed to investigate the potential benefits of automated shading on the cooling load reduction in the spring and autumn time were carried out in several sets to cover a wide range of different weather conditions. Weather during mid-seasons is prone to rapid daily fluctuations in temperatures as well as in the levels of solar radiation. Because of this the key part in setting up the controller was the appropriate tuning between the summer and winter components of the thermal control loop.

The two experiments presented in this paper were conducted with the thermal loop governing the actions of the roller blind. This means that illuminance fuzzy loop was switched off at all times and thus had no effect on the results of the experiments. The input fuzzy variables to the thermal controller were global solar radiation and the temperature difference between the set-point temperature and the measured indoor temperature. The output of the controller was movements of the roller blind and switching the ventilator and the heater on or off. Simultaneous functioning of the heater and the regulator was not allowed at any time. In the diagrams a completely exposed window is equivalent to 100 %, which correlates to a completely retracted roller blind. On the other hand, a fully shaded window is represented by 0 % (e. g. fully extended roller blind). Similar in the case of the heater and the ventilator their functioning is represented in the fraction of operational output (e. g. 0 %=off, 100 %=full output).

Katarzyna Zielonko-Jung1* and Janusz Marchwinski[4]

1 Warsaw University of Technology, Faculty of Architecture, Department of Ecological Industrial
Architecture, Koszykowa 55, Warsaw, Poland.

2 High School of Ecology and Management, Wawelska 14, Warsaw, Poland.

* Corresponding author, kasiziel@wp. pl 1

Abstract

The quality of indoor environment depends on many factors. One of the most important is the external wall’s permeability to natural climatic conditions. The interactive wall should act as a filter, which protects from the undesirable factors and allows to pass and control the favourable ones. It has to react to changing weather conditions and requirements of indoor environment.

There are many different solutions based on this idea. One of them is double-skin facade with openable windows, which provide natural room ventilation. This kind of facade became quite a popular and common solution for high-class office buildings in Western and Central Europe during the last ten years. It was classified as a convenient (from the perspective of indoor environment and energy savings) high technology solution. Now, after some years of exploitation experience, comes the right moment to verify this thesis.

The paper concentrates of advantages and most important drawbacks related to the implementation of double-skin facades. This approach allows to assess whether this kind of a wall can be a successful implementation of the interactive wall model and what is the future for this kind of development.

Keywords: glass, facade, double-skin facade, interactive wall.

Many different concepts relate to the idea of an interactive wall. They represent two different technology approaches, named by authors as macro-scope and micro-scope solutions (fig.1) [11]. “Macro” refers to the scope of the external wall equipment with additional elements, such as solar shelves, shading systems, acoustic panes, double-glazed layers, ventilation ducts and others. “Micro” refers to the scope of the glazed pane, which consists of nanomillimeter layers responsible for the environmental processes (control sensors, thermal insulation, light transmittance and others). Best example of this idea is the model (still only theoretical) of polyvalent wall of M. Davies [2]. New high-technology solutions like low-e layers, temperature-dependent layers or electro-optic layers allow to put to practice some of its principles. Solutions like transparent insulation materials (TIM) or louvers integrated in the glass modules (between two panes) were classified as belonging to the intermediate group.

INTERMEDIATE-scope

■ transparent insulation materials (TIM)

■ louvres integrated in glass module

■ integrated in glass module

Fig.1 Classification of solutions based on interactive wall model.

The most interesting and promising solution in the macro­scale group is a double-skin (double-glazed) facade with openable internal window (fig.2). The void between two layers acts as a thermal buffer zone and a ventilation duct.

This kind of external wall became quite a popular and common solution for high-class office buildings in Western and Central Europe during the last ten years. It was presented as an opportunity to use more natural ventilation and less air conditioning in such buildings (including high-rise ones). In consequence, it was expected to minimize energy consumption and increase the comfort of indoor environment. Many authors labelled these walls as energy-saving, ecological, high-tech solutions. 2

The exchange of air mediated by double facades is superior to that of single-wall facades. It is possible to open the windows even during winds, which could cause excessive ventilation or could not be normally opened in buildings with single-wall facades. In turn, in the case of external walls placed in wind-free locations, the exchange of air through windows placed in double-fa9ade walls may be too small.

These properties are particularly important in the case of high-rise buildings. The external layer of the fa9ade is subject to being struck by winds, which at higher levels may cause significant changes in air pressure acting on the wall of the building. In the inter-fa9ade space the amplitude of wind pressure changes is much smaller, which makes it possible to open windows located in the internal layer [8].

The electricity generated by the PV cells must be expressed as:

q’’e ={Tcc)nIAMPvGtpvpv (W/m2) (10)

where: t]pV is the PV efficiency. The PV efficiency is depending on the PV cells temperature and on the incident radiation. To consider these two factors, a linear variation model has been adopted.

2. Prototypes and monitoring strategy

A distinction should be made between the determination of the energy efficiency at component/fa? ade level and at building level. For this reason, the experimental activity will be divided in two stages and two different prototypes will be constructed. The first stage consists in the construction of a small system, very similar to TRE [8], formed by a single PV module tested under forced convection situations. The 8 new modules of ISOFOTON will be tested to obtain specific data about heat exchange and electricity performance. The second stage will be the construction of a more sophisticated system to test the best configuration of PV module under real conditions. This phase will start using the test cells of the Politecnico of Torino and later, the construction of similar cells in Lleida will be carried out. During August and September 2008 the monitoring task will start and it will be extended until the end of 2009. In the figure 3 the schemes for the first prototype are shown.

3.

Conclusions

A strong thermodynamic coupling exists between the air flow through the naturally ventilated double­skin fa? ade and the air temperature difference between the cavity and the outside. This interaction can only be predicted by sophisticated building energy modelling and simulation techniques as was done in the current study. Three new TRNSYS types have been developed and validated through numerical experiments. One first prototype has been constructed at the University of Lleida and the monitoring
period has just started. Experimental results to validate the TRNSYS types and to get some conclusions about the 8 new PV modules are expected to be available by the middle of 2009.

Concerning to the convective heat transfer and the mass flow rate within the air gap, this research has showed that there is still a lot of work to be done to clearly define the performance under transient turbulent free convection.

The first standardized typologies defined within this research will be further refined and included in the second prototype. Once they are validated under real conditions, the manufacturing process as well as the commercial strategy will be defined.

References

[1] Bar-Cohen A. and Rohsenow W. M. 1984. ‘Thermally optimum spacing of vertical, natural convection cooled, parallel plates’. Journal of Heat Transfer. 106.

[2] Bejan A. and Kraus D. 2003. ‘Heat Transfer Handbook. John Wiley & Sons Ltd.

[3] Brinkworth B. J. 2000. ‘A procedure for the routine calculation of laminar free and mixed convection in inclined ducts’. International Journal of Heat and Fluid Flow. 21.

[4] Brinkworth B. J. and Sandberg M. 2006. ‘Design procedure for cooling ducts to minimise efficiency loss due to temperature rise in PV arrays’. Solar Energy. 80.

[5] Churchill S. W and Ozoe H. 1973. ‘Correlations for forced convection with uniform heating in flow over a plate and in developing and fully developed flow in a tube’. Journal of Heat Transfer. 95.

[6] Filonenko G. K. 1954. ‘Hydraulic resistance in pipes. Heat Exchanger Design Handbook. Teploenergetica Vol 1. Hemispher Publisher Corporation.

[7] Fux V. 2006. ‘Thermal Simulation of ventilated PV Fagades’. Loughborough University.

[8] Gandini, A. 2003. ‘Analisi numerica delle facciate fotovoltaiche a doppia pelle’. Politec. di Milano.

[9] Kakag S., R. Shah and W. Aung. 1987. ‘Handbook of single-phase convective heat transfer’. Wiley.

[10] Kays W., Crawford M. and Weigand B. 2004. ‘Convective Heat and Mass Transfer. McGraw Hill.

[11] Mei L., Infield D., Eicker U., and Volker F. 2003. ‘Thermal modelling of a building with an integrated ventilated PV facade’. Energy and Buildings. 35.

[12] Parretta A., Sarno A., and Yakubu H. 1999. ‘Non-destructive optical characterization of PV modules by an integrating sphere.: Part I: Mono-Si modules’. Optics Communications.161.

[13] Ramanathan S. and Kumar R. 1991. ‘Correlations for natural convection between heated vertical plates’. Journal of Heat Transfer. 113.

[14] Rohsenow W., Hartnett J. and Cho Y. 1998. ‘Hanbook of Heat Transfer. McGraw Hill.

[15] Saelens D. 2002. ‘Energy Performance Assessment of single storey multiple-skin facades’. Katholieke Universiteit Leuven — Faculteit Toegepaste Wetenschappen.

[16] Sharples S. and Charlesworth P. 1998. ‘Full-scale measurements of wind-induced convective heat transfer from a roof-mounted flat plate solar collector’. Solar Energy. 62 -2.

[17] Siegel R. 2002. ‘Thermal Radiation Heat Transfer’.Taylor and Francis.

[18] Wouters P. and Vandaele L. 1994. ‘The PASSYS services: summary report’. European Commission Publication No. EUR 15113 EN

Mojtaba Samimi1*, Laya Parvizsedghy2 and Morteza Adib1

1 Faculty of Architecture and Urban Planning, Shahid Beheshti University, Tehran, Iran
2 Faculty of Art, Tarbiat Modares University, Tehran, Iran
* Corresponding Author, mojtaba_samimi@yahoo. com

Abstract

It is strongly recommended to apply local properties of each location especially the effect of the sun to answer questions about the form and orientation of buildings, the shape and amount of openings in each direction, and the layout of building masses beside each other.

Considering that qualitative methods of climatic site analysis may not include exact properties of each location and also as the other existing quantitative methods are almost complex and time-consuming which are not easy to use especially in the first steps of design; in this article, by describing the method which defines local kind and unkind faces of the sun, after collecting positive and negative gain of each direction trough the year, generating score of each direction is resulted for different cities of Iran.

Finally “Solarch.-VisiorT the computer program based on this method is presented, which brings a brand new vision to the architects, urban designers and landscape architects to discover the advantage/disadvantage of decisions about kind/unkind faces of the sun in each location through the design process.

Keywords: Solarch.-Vision, solar analysis, architecture, eco-design

Measurements have been carried out on two low iron 4 mm “Eurowhite” glasses from Euroglas GmbH. One of the glasses is equipped with the commercial antireflection surfaces prepared by means of a liquid-phase etching by Sunarc Technology A/S.

The transmittances of the two clean glasses were first measured in an indoor goniospectrometer test facility [2]. A ray of light from a tungsten halogen lamp is reaching the surface of the glass, which is installed in the test facility in such a way that the transmitted radiation through the glass is measured in a half sphere with a diameter of 2 m for different wavelengths. Measurements of the irradiance in the sphere are carried out with and without the glass installed in the test facility. In this way the transmittance, that is the ratio between the transmitted radiation and the total radiation from the lamp, is determined. Since the wavelength distribution of the lamp is not identical to the wavelength distribution of solar radiation, a correction based on the wavelength distributions of the lamp and the sunlight (ISO 9050) is done in order to determine the solar transmittance.

The glass in the test facility can be rotated through a vertical axis. In this way the incidence angle can be changed. The transmittance is determined for five different incidence angles: 0°, 30°, 45°, 60° and 75°. The measured transmittances as functions of the wavelength and the incidence angle for the two glasses are shown in figures 1 and 2. The transmittance is reduced for increasing incidence angle. The maximum value for the transmittance is for increasing incidence angles moving towards small wavelengths, especially for the antireflection treated glass.

1.0

0.9

0.8

0.7

Fig. 1. Transmittance for the normal glass as functions of the wavelength and the incidence angle.

The measured solar transmittances for the two glasses are shown in table 1. The solar transmittance is increased by about 6-10 % point by the antireflection treatment. The increase is dependent on the incidence angle.

1.0

0.9

0.8

0.7

T1

0.6

0.5

Є

0.4

H

0.3

0.2

0.1

0.0

2200

Fig. 2. Transmittance for the antireflection treated glass as functions of the wavelength and the incidence

angle.

The solar transmittances for the two glasses as functions of the incidence angle are shown in figure

2. Best fits for the solar transmittance of the direct radiation are found to be:

t—— / 0.904 = 1 — tan4 31 — I for the normal glass

t—— / 0.960 = 1 — tan511 — I for the glass with antireflection surfaces where 0 is the incidence angle, °

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

The diffuse-hemispherical transmittance xdlf h was measured in an outdoor laboratory test facility under weather conditions without direct solar radiation for the two clean glasses. The test facility is placed at the Technical University of Denmark, Kgs. Lyngby, Denmark. Tdif-h is the ratio between

The measurements were carried out in the test facility with four calibrated pyranometers, type CM 5 and CM11 from Kipp and Zonen. Before the tests started all 4 pyranometers were tested against each other after they have been put into position, but before the shadow ring and the glasses were installed to be sure they all gives the same output signal for the same solar irradiance. During the tests the pyranometers are measuring the total irradiance on the glasses, the diffuse irradiance on the glasses and the irradiances transmitted through the two glasses. The accuracies of the measured irradiances are estimated to be within 2%. The glasses are placed side-by-side on a 45° tilted surface facing 10° towards west from south, see figure 4.

Typical operation of some of the ventilation strategies is depicted here for a building with heavy thermal mass and high insulation, subject to 20 W/m2 internal gains, in urban situation and for a normal summer of type 2004 (fig. 3). Analysis is given in terms of overheating duration (number of hours of occupation above 26.5°C), which should not exceed 100 h according to Swiss comfort regulation [6]:

• Limited to diurnal occupation, mere base ventilation (Base) yields a building response way above ambient. Overheating extends over more than 1000 h, of which 500 h above 30°C.

• With a twice more important airflow, limited to the fresh hours, direct night cooling (Direct) considerably reduces the diurnal building temperature. Overheating now reduces to 240 h, with a summer peak slightly below 30°C.

• By dampening of he day/night oscillation, buried pipes of 20 m length used in single-mode (Pipe20m-Sgl) allow for continuous over-ventilation of the building, whereas the 12 h phase — shifting device (Shift12h-Sgl) moves night ventilation onto the day period. Overheating now extends over 200 h, respectively 180 h, with a summer peak slightly below 29°C.

• Not depicted here, setup of these systems with alternative direct night cooling allows to reduce overheating below the 100 h limit.

• The strongest cooling potential however goes for evaporative cooling. Except for base ventilation, all the configurations with increased flow (direct ventilation, buried pipes, phase — shifting, in single or alternate mode) allow to remain below the 26.5°C threshold, hence largely respecting the Swiss comfort regulation.

In the first experience (Rebibbia jail, Rome, 2002) 30 prisoners attended the training course while 18 of them ended it. That has to be considered a good result compared to the average level of participation in professional training courses, that is around 10%.

The new ongoing trainings in Rome, Turin, and Laureana di Borrello (Reggio Calabria) are based on smaller classes with a higher commitment: around 80% of attendants partecipation recorded in the first theoretical phase.

A specific training module has been developed to underline the social value of the programme, and a technical and psychological commission selected the people to be involved in the courses, evaluating their attitude to technologies and new jobs.

The course is preceded by motivational interviews while the motivation degree is monitored during the training through moments of group evaluation.

The assessment is made through the submission of questionnaires (self empowerment, technical skills) before, in the middle and at the end of the training.

The main aims for social supporting are:

1. To contribute to the successful installation of the solar plant by an internal awareness and "ownership" integrating technical training with a motivational and psycho-social path.

2. To promote the acquisition of new abilities in order to look at the educational training as an experience of growth and self awareness towards environment and new opportunities regarding the external society.

3. To acquire the ability to work in team and, consequently, to promote social skills on job training and team building.

The most challenging difficulty to be overcame in the practical job was the integration among different approaches and cultures. On the other hand, the positive interdependence among different abilities, and the introduction and consolidation of a pluralistic culture and competencies in practical activities, developed a proper use of the group as an instrument of empowerment.

1.1 Analysis of photomicrograhs

Transmission electron microscope (TEM) or photomicroscope (PM) can be used to produce the optical photomicrographs of thin films. These micrographs can then be used to study the surface microstructure of the thin films. For example, the grain shape and grain boundaries can be seen directly on the micrograph. The other parameters such as the grain size, grain size distribution, orientation and volume can either be measured or computed from the micrographs. These grain size and grain size parameters are very important in understanding the optical and spectral properties of materials that we are concerned with in selective applications. [2]

Several procedures can be used to measure or estimate the grain size. These are [2, 4-5]

Comparism chart estimates Fracture grain size estimates

Planetric (Jeffries) measurements Intercept (Heyn) measurements Snyder-Graff Intercept methods

Possibilities of application of facade solar collectors in the urban environment can be shown for typical cases. To imagine how the urban environment can influence annual solar irradiation on facades of buildings three different types of urban structure in Prague have been chosen. Considered estates differ in time of construction and density of buildings.

The oldest case is housing estate in quarter Vinohrady typical for central part of Prague (see Fig. 4, left). Housing estate is formed by five floor tenement houses with central courts each placed very close to others (distances between houses is 15 to 20 m). Although the application of solar facade collectors at houses with certain historical value is problematic, the case has been chosen as an example of dense structure and its influence on solar gains.

Housing estate Chodov from 70’s of 20 century has very heterogeneous structure (different heights and orientation of buildings, see Fig. 4, right) with free areas among prevailing row buildings with 8 to 12 floors. Ground plan of the building site is very irregular.

Housing estate case Barrandov is a quite young structure in Prague built in 1988. Case with sparse building structure is formed by tower fabric buildings with 4 to 8 floors (see Fig. 5). South orientation of building gables with large available areas is advantageous for facade integration of solar collectors.

Shading analysis for given three cases has been performed using ESP-r simulation tool. Annual solar irradiation level for south building fagades in the individual cases obtained from simulations are shown in Fig. 6 to 8. Designation of buildings in the ground plans is identical with model views. Each building is described with its height and annual solar irradiation value in kWh/m2.

While shading by surrounding urban environment in the central part of Prague (case Vinohrady) leads to reduction of incident solar irradiation by 10 to 20 %, housing estates in suburban areas show the reduction significantly lower about 1 % (case Barrandov) with maximum 5 % (case Chodov).

2. Conclusion

Sensitivity of south building fagade to shading by surrounding objects has been investigated with respect to basic geometry parameters (height of considered shaded building, distance from shading object and height of shading object) for two principally different building types (row building, tower building). The simulation analysis resulted in parametric curves for solar irradiation reduction factor. Practical use of such graphs is in easy and fast outlook on required geometry parameters and relationships to maintain sufficient annual solar irradiation values on fagades or for prediction of possible fagade shading problems for given urban environment geometry.

Influence of fagade shading has been further analysed in three case studies with different urban environment structure. While old urban structure in the city centre shows considerable reduction of solar irradiation up to 20 %, for the newer housing estates the reduction ranges within several percents and offer the application potential for solar systems with fagade-integrated collectors without excessive shading problems.

References

[1] G. Rockendorf, S. Janssen, Facade integrated solar collectors, Proceedings of the ISES Solar World Congress 1999, Jerusalem, Israel.

[2] I. Bergmann, W. Weiss, Fassadenintegration von thermischen Sonnenkollektoren ohne Hinterluftung, AEE Intec, Final report, Gleisdorf 2002.

[3] W. Weiss et al., Solar Heating Systems for Houses: A Design Handbook for Solar Combisystems. Earthscan Publications Ltd. (June 2004), ISBN 978-1902916460

[4] T. Matuska, B. Sourek, Facade Solar Collectors, Solar Energy, vol. 80, pp. 1443-1452, 2006.

[5] T. Matuska, B. Sourek, Solar systems with fagade-integrated collectors. Proceedings of ISES 2005 Solar World Congress. Orlando (Florida, USA) 2005.

[6] T. Matuska, B. Sourek, Aspects of solar collector integration into building fagade. Proceedings of ISES Eurosun 2006. Glasgow 2006.