8/9/2019 DYN05 11 Bloem

1/16

1

STUDY OF A HYBRID PV INTEGRATED BUILDING

APPLICATION IN A WELL CONTROLLED TEST ENVIRONMENT

J.J. BLOEM

EC -JRC, Institute for Environment and Sustainability, Renewable Energies Unit,I - 21020 Ispra, Italy. E-mail hans.bloem@jrc.it

ABSTRACT

From the experience gained in several EU research projects, an improved design for a common TestReference Environment was made allowing the assessment of experimental data for electrical and thermalperformance evaluation of photovoltaic systems integrated as cladding components into the buildingenvelope, giving input to modelling work. The specific design of the PV module and test reference

environment makes it possible to study through electrical and thermal energy flow analysis, the effect ofusing different materials for PV modules and construction design of claddings. Beside a generalintroduction about building integrated photovoltaic applications an outdoor experiment and modelling

results of a glass-glass PV module with forced ventilation is presented.

1. INTRODUCTION

The aim of the work is to investigate the heat exchange of a PV device in a typical built environment. Fromthe experience gained in the PV Hybrid Pas [Ref 1,2] and IMPACT [Ref 3] research projects, an improved

design for a common test reference environment was made allowing the assessment of experimental datafor electrical and thermal performance evaluation of hybrid PV systems. Particular attention has been givento the specific built environmental conditions for photovoltaic (PV) that is at lower level of irradiation andhigher PV module operating temperature.

The Test Reference Environment (TRE) is constructed in such a way that the thermal energy obtained by

convection and radiation exchanges at the rear of the PV module can be measured accurately [Ref 4]. The

test environment box is designed to be placed in the south wall opening of the PASLINK test cell and iscomposed of an insulated cavity of 10 cm with an air in- and outlet placed at the back of the box.Considering the long wave energy exchange it was decided to have the cavity painted in defined colours.The box is equipped with a number of air and surface temperature sensors, providing detailed data formodelling work.

1.1 Introduction on BIPV

Before going into details of this study of a hybrid PV integrated building application a general introductionon Building Integrated PV (BIPV) will be given in order to understand certain developments in this area.Over the past 10 years (1995 2005) the interest in renewable energies in general has been increased.When the built environment is concerned in relation to renewable energies, the focus is mainly on solar

energy and in this paper in particular on photovoltaic technology.

The PASLINK EEIG network [http://www.paslink.org] has a long lasting experience in outdoor testing,analysis and modelling of building components under real test conditions. The interest in studying theoverall performances of photovoltaic devices that are integrated in the building envelop came forward fromthe testing and analysis of passive solar building components. The network started the PV Hybrid Pas

project, aiming to study electrical and thermal performance evaluation criteria. The success of this projectstarted several other European projects, such as Prescript [Ref 5], Impact, PV Cool Build [Ref 6], HyPRI.

At present true BIPV is not common yet, as can be concluded from a recent study [Ref 7]. About 1% of theinstalled PV capacity can be regarded as truly integrated in the building envelop. However, other reports[Ref 8, 9] show that the photovoltaic industry is preparing for a considerable increase in production. Someexpect 3 Giga Watt of installed PV systems by the year 2010. The outcome of the PV CITY GUIDE projectby DG RESEARCH indicates that more than 50% of PV installations will be in urban areas, mainly onroofs of buildings, but large facades are expected to become interesting objects as well once the PV and

construction industry develop innovative BIPV products. The recent Solar Generation report [Ref 10] givesexpectations of the PV market development until 2020. For the grid connected market in the residential

8/9/2019 DYN05 11 Bloem

2/16

2

built environment about 27 GWp cumulative is expected to be installed in Europe by 2020, with averagesize of 3kWp installations. For a good understanding it is important to distinguish between PV-integration

into the building envelop and the integration into the electrical network of the building only. The latter caseis supposed to have no impact on the thermal balance of the building and is often regarded as an addedinstallation to the buildings energy system. At present by far the most PV applications are rooftop systems.Building envelop integration of PV systems can be categorised in three BIPV groups: roof integrated,

facades (windows and curtain walling) and awning devices.

Several European Directives [Ref 11 and 12] will stimulate the use of renwable energy technologies in thebuilt environment. Authorities of some European Member States are seeking the best regulations andincentive schemes to attract private people to invest in renewable energies. In residential urban areas this ismost visible by roof integrated PV installations, ranging from small 400Wp PV installations to full roofcovered installations that can be sized like 3kWp. In figure 1 is illustrated the complexity of a properintegration of PV technology in the built environment.

Figure 1.Complexity illustrated for Building Integrated PV applications.

When it concerns integration of photovoltaic technologies in the built environment three industries are

involved: the construction, the glass and the photovoltaic industries. The situation at present is that thecapacity of PV cell and PV modules production easily can fulfil the demand. Therefore PV industries do nothave to look for specific applications in the market. There is more than enough roof area available inEurope to install PV in the coming ten years without additional effort of integrating it in the buildingenvelope.

The project PV-Hybrid-Pas [Ref 1 and 2] studied the overall performance of hybrid PV systems, whereasthe project Prescript [Ref 5] was investigating the need for prestandardisation. The latter one concluded that

grey areas exist for building codes and PV standards and laboratory measurements can not fulfil the needfor BIPV system testing. The main objective of the project IMPACT [Ref 3] was to study the heat exchangeof a PV module to its direct surroundings and investigate possible improvements for BIPV components andsystems.

As a conclusion of this brief introduction when may say that initial interest in BIPV was focussed on hybridapplication of the incoming solar energy, e.g. electrical and thermal energy, the latter for the purpose of pre-heating ventilated air. It is expected that in the near future the integration of PV will attract more attention

for economical reasons [Ref 23], e.g. to bring overall costs down by integration of electricity generationelements in the existing construction and energy infrastructure of a building and not necessarily the use of

warm air in the building. Overheating in Mediterranean climates and the increased electricity consumptionfor air conditioning could be another BIPV application. Some examples are given in [Ref 24 and 25]. In[Ref 7] the future of PV in the built environment and in [Ref 13] the barriers for BIPV to overcome for a

8/9/2019 DYN05 11 Bloem

3/16

3

proper market introduction, are discussed.

2. PERFORMANCE EVALUATION OF HYBRID PV COMPONENTS

Hybrid PV components, integrated in a buildings skin, are interacting with the building in many respects.This is schematically shown in figure 2. A comprehensive assessment procedure should include the

following aspects:

2.1 Electrical performances of BIPV elements

The measurement of the electrical performances of PV elements has already been standardised to a largeextent. The electrical efficiency however is dependent on the temperature of the PV element. If the heatproduced is partly recovered for other purposes in a hybrid component, then this will affect the electricalefficiency. Therefore a combined thermal and electrical performance test in real outdoor conditions isnecessary. The project PV Hybrid Pas was using outdoor test cells for a caloric assessment of a hybrid PVsystem with a closed space, while the project Impact was using the TRE to assess the thermal exchange of

the PV module with its environment

Figure 2.Interaction of various phenomena for a hybrid PV component applied to a building.

2.2 Thermal processes at component level

Aspects to be investigated are :

Dynamic aspects of U-value in situation without air flow in the cavity

Overall energy performances for the test duration but also for standardised conditions. This

requires the combination of realistic measurements with simulations, through so-called scaling andreplication techniques.

Dependency of component dimensions. The thermal buoyancy effects (and therefore also theelectrical efficiencies) vary as function of the length (height) of the PV component.

8/9/2019 DYN05 11 Bloem

4/16

4

2.3 Thermal performances in winter and summer time

The heat gained through hybrid PV components can be used for heating purposes of the spaces adjacent tothese PV facades or roofs. The interaction with the space can be studied by outdoor testing of thecomponent in test cells, where the thermal comfort in the test room can be studied. Based on the results ofthe test cells experiments, the effect of such components on real buildings and in various climates can be

studied by simulation (scaling and replication) of the energy, ventilation and daylight performances. Thethermal comfort in the room can be evaluated as well. The pre-heating of the air in a hybrid PV component

is not always an advantage. In summer time, pre-heated air will have a negative influence on the indoorclimate. In practice, different strategies for summer and for winter time are therefore required. AmorphousSilicon type PV cells are transparent for long-wave radiation and also in the case of semi-transparent hybridPV elements, very high heat flows can pass through the inner surface of the component (partly direct solargains, partly by radiation due to the high surface temperature of the inner glazing). This is a very importantelement, which must be included in the evaluation.

2.4 Ventilation performances

The utilization of warm air for the purpose of pre-heating in particular for the colder season, needs to assessthe ventilation performance of the integrated PV-installation. With respect to the procedures for evaluating

the ventilation performances, a distinction must be made between two types of systems: naturally ventilated systems; The air flow rate varies over time as function of the outside climate,

the inner climate and the use of the building. Prediction of the performances is complex. mechanically driven systems; In this case, the air flow rate should be more or less constant and

known, the estimation of the thermal balance is therefore easier to be made.

2.5 Visual performances

In the case of partly transparent components, the visual performance of the components and their impact onthe visual comfort inside the space are important. Different aspects are involved, such as, daylight

availability and distribution inside the spaces, glare problems.

2.6 Maintenance related aspects and durability

Maintenance can be a critical aspect, especially given the fact that air is flowing through the component.The aspect of water tightness has to be considered as well. Also, condensation problems can occur whenusing certain strategies. It is necessary to evaluate whether the commonly used procedures can be used forsuch components and, if not, to propose alternative procedures.

2.7 Other Performance objectives

To understand the building integration issues it is useful to apply a methodology developed during IEAAnnex 32 related to the performance of the building envelope, including PV integrated systems [Ref 14].The design of the building envelope may need to fulfil a number of interrelated performance requirements,including the usual criteria of conventional building components and systems, in order to meet the

specification of the client, designer and legislation. Typically, the building will be required to meet thefollowing performance objectives:

Adaptability Safety

Good comfort

Health

Energy efficiency

Durability

Minimum environmental impact

Optimum total cost Image

A list of requirements (the design matrix as illustrated in figure 3) may be drawn up for the specific

component or system, based on the above Fitness for Purpose objectives chosen by IEA Annex 32 for theperformance assessment of advanced building envelopes. When adjusted for photovoltaic products intendedfor integration in the built environment this can be used as a simple design tool:

8/9/2019 DYN05 11 Bloem

5/16

5

1. To evaluate the possible impact of the advanced component on the overall building performancecompared to a traditional building envelope design.

2. To identify which knowledge domains are necessary to identify the relevant performance indicators.

3. To identify areas where existing tools, standards, codes, etc. are unsatisfactory or should bereviewed.

Figure 3. Design Matrix Initial assessment of advanced envelope component.

As an initial exercise, the impact of the system on each of the requirements list is assessed on a scale from 1having about the same impact as conventional envelope to 3 having a more significant impact (negative orpositive) or a special requirement. The impact of PV on the indoor climate day lighting, ventilation,

thermal comfort, etc. should be considered [Ref 15, 16, 17]. The integration of PV should not compromiseenergy efficiency in the building i.e. no additional heating, cooling, ventilation or artificial lighting shouldbe needed. Installation, safety and maintenance issues may differ for building integrated PV (BIPV)compared with traditional building envelopes.

3. TESTING

3.1 Laboratory, outdoor testing of PV modules and BIPV system testing

Building designers are interested in performance under operating conditions for a typical climate, seasonand specific location taking into account the energy use of their design. Integration of PV in the buildingenvelope implies that they have to take into account electrical energy production, but also thermal (avoidoverheating in summer) and comfort (daylight, ventilation and quality of air) aspects. A furtherconsideration is that building designers need performance indicators based on climatic variables: ambienttemperature, solar radiation, wind and site dependent data such as obstructions giving possible shadingproblems.

The technical data provided by the PV industry is based on standardised measurements under laboratoryconditions described in IEC 61215 [Ref 18]. The most important test procedures are:

10.2 (Standard Test Conditions),

10.5 (Measurement of Nominal Operating Cell Temperature),

10.6 (Performance at NOCT) and

10.7 (Performance at low irradiance).

The outdoor tests described in IEC 61215 are concerned with open rack mounted PV modules for optimised

inclination. A number of different circumstances occur when PV modules are applied as integratedcomponents in a building, which is far from the Standard Reference Environment as described in the IEC61215:

The inclination for faade application is typically 90 degrees and for roof applications depending

on the roof construction but is seldom optimized. Free convection at the backside of the PV modules will not occur.

8/9/2019 DYN05 11 Bloem

6/16

6

As a consequence the most notable differences are in level of irradiation and operating cell temperature.Therefore conversion from PV module specifications at Standard Test Conditions (25 C, 1000 W/m2,

AirMass 1.5 Global) to BIPV applicable electric system design values is of highest priority when theintegration of PV in buildings continues to emerge.

The main differences are to be found in the convective and irradiative heat exchanges on the rear side of the

PV module. These different thermal exchanges cause the NOCT line to move upwards. Thus even if theNOCT - SRE is available the outdoor surroundings may cause a different equilibrium mean solar cell

junction temperature due to different irradiative (asphalt, grass, grit) and convective heat exchanges.

Irradiance [W/m2

]

Figure 4.Temperature difference versus Irradiance.

In the graph above, the standardized reference points are given, being the STC and NOCT conditions.

Looking more in detail to this graph, one may conclude that building integrated PV applications are situatedabove the NOCT line. Designers and architects therefore need to calculate with extrapolated data from PVindustry supplied specifications. The Prescript project aimed to study the necessarily procedures to facilitatethe PV industry the required construction norms. It therefore carried out a number of realistic tests undercontrolled climatic conditions.

Figure 5.The Prescript project: indoor testing of a complete PV roof system in the climatic chamberand simulator facility LS-1 at the EC DG-JRC, Ispra.

8/9/2019 DYN05 11 Bloem

7/16

7

More and more new PV products are entering the market bigger in size and more complex in operation.BIPV systems should be tested on overall energy (electrical and thermal) performance related to electrical

standards and building codes.

3.2 Test Reference Environment

The Test Reference Environment (TRE) is a thermally well insulated wooden box that provides a 10 cmwide air gap between the PV module and its rear facing surface (that would be usually a wall). Experience

from the previous PV Hybrid Pas project led to an improved experimental set-up with higher accuracy ontemperature measurements. Irradiative disturbances from the boundaries of the PV module are stronglyreduced. Furthermore the air in- and outlet are placed at the rear and shaded by the box itself. PV modulesup to 30 mm thick can be placed simply in the frame of the box.

Figure 6. Initial set-up designed for the South-

wall opening of the Paslink test cell.

Figure 7. Improved design as a stand-alone box

for more variety of boundary conditions.

Temperature sensors (thermo-couples are used) are positioned as is given in figures 7 and 9 and photo 10.

The external sizes are 203 * 203 * 46.5 cm. The used plywood is 15mm thick and the EPS insulation is100mm thick. The internal opening is a square of 120.6 cm allowing window and/or PV module

components with the maximum size of 120 * 120 * 30mm to be measured. The outlet air tube is 200mmdiameter.

8/9/2019 DYN05 11 Bloem

8/16

8

Photo 8. The BIPV-Test Reference Environment at the JRC, Ispra.

Air outlet

Figure 9. Horizontal cross-view at level of air-outlet tube and the position of the four temperature sensors.

A tube of the same size but with a slit of 25 mm over the length of the gap between the PV module and therear facing wall has been used to spread the flow as homogeneous as possible along the rear of the module.See photo 10 and 11. Special attention has been given to the temperature difference measurement betweenair in- and outlet. A thermo-couple pile consisting of 8 thermo-couples is put in place. The sensors are gluedon a copper plate of 1cm2and give some thermal mass to the sensor.

Photo 10.The air-gap inlet with four piled temperature sensors.

By placing different materials at the rear facing surface, the boundary conditions for different experimental

conditions, the set-up of the PV module can be changed easily. An aluminium sheet with several fins of 5cm length was used in one of the experiments, in order to change the radiative and convective heat

exchange.

8/9/2019 DYN05 11 Bloem

9/16

9

Photo 11. The air inlet opening and the air outlet tube. The air flow rate is measured at the bottom end ofthe tube.

The air flow is measured in the outlet tube by means of a hot-wire anemometer, following a standardisedmethod for tubes. In principal the method is simple: measure mean air velocity in the tubular duct with ananemometer and get the flow by multiplying by the duct area.

Figure 12. Dynamic behaviour of the heat exchange coefficient.

However, the fact that the ventilation profile in the duct is not uniform complicates the matter somewhat.Following the instructions the method will limit the error to around 4%.

The optimum working point for the highest accuracy on the thermal energy that is contained in the air-gapis derived from an extensive error analysis study. It was concluded that for the TRE an air flow of 25 +-3 l/s

is within the limits of accuracy.

In [Ref 19, 20 and 26] the need for this improvement is discussed in further detail. In figure 12 however the

8/9/2019 DYN05 11 Bloem

10/16

10

impact of the airflow on the heat transfer coefficient is made visible by simulation output from FLUENT.

Recently a further improvement has been madeto the TRE-box. The air-inlet has beensubstituted by 0.1 m

2 rectangular opening, over

the full width of the air-gap, allowing the flow of

air enter the sensitive area behind the PV modulewithout disturbance, creating Air outlet, a more

homogenous heat exchange.

Airflow measurement point The ambient airtemperature near the inlet is measured andcompared with the temperature at the entrance ofthe air-gap behind the PV module to check forpre-heating.

Temperature In front of the TRE are mountedtwo white sensors painted shading devices inorder to avoid heating up of the TRE from solar

radiation and therewith disturbing the airtemperature measurements. See figure 13 forclarification. Note that not all sensors arepresented in this figure.

Figure 13.A cross-view of the new TRE.

4. EXPERIMENTAL RESULTS

For the here reported case-study a PV module with glass-glass poly-crystalline Si technology was selected.

It can be found regular in faade applications.

Four equally sized p-Si PV-modules, 120*120 cm, have been used on the TRE. Each module differs fromthe others for its composition and packing factor. In photo 14 can be seen the experimental set-up for anelectrical and thermal performance assessment as was carried out under the Impact project.

A 121 cells glass-glass PV-module; bottom right in the photo

A 64 cells glass-glass PV-module; bottom left in the photo

A 121 cells glass-tedlar PV-module ; top right in the photo A 121 cells transparent tedlar-glass module; top left in the photo

Photo 14. Thermal image from the four p-Si PV-modules that were used in the experiments

The thermal image in photo 14, has been taken 1stof October 2002; the 8-color scale ranges from 31 to 51

8/9/2019 DYN05 11 Bloem

11/16

11

C and illustrates nicely the impact of the PV-module composition.

The modules are designed specifically for this research project and include specific incorporated cells forthe measurement of the short circuit current, the open voltage. See Ref [4, 20] for further information. ThePV-module consists of 3 different strings of PV cells allowing the assessment of the required input foranalysis. In principle a signal for solar radiation is obtained from the current of one PV-cell connected to a

shunt. In the laboratories of the JRC the calibration data for these specific cells, are measured. Oneparticular string of 36 cells was used for open voltage measurement and gives a signal for the temperature

of the cell under operating conditions. In addition a temperature sensor has been laminated in the module.Outdoor measurements are made to obtain specific data from environmental conditions, including wind andthermal measurements. Two strings of 36 cells are connected in series (72 cells are similar to a 100 Wpmodule) and connected to a Maximum Power Point inverter.

The experiments have been performed with forced airflow at four different levels of air flow rate. Theventilator speed settings correspond to measured air velocity in the outlet tube and air flow mass (requiredas input to MainType83 as follow:

Ventilator speed settings air velocity[m/s]

Air flow mass[m3/h m]

6 1.37 129.9

7 1.75 164.7

10 2.49 234.9

13 3.43 323.1

In figure 15 are graphically presented the thermal efficiencies for the glass-glass PV-module for the fourdifferent forced ventilation settings.

Figure 15. Thermal efficiency of the 121 cell glass-glass module

Some conclusions can be made from the analysis of the experimental data collected. For increasing valuesof air flow in the TRE air-gap it is possible to observe an:

increase of the thermal efficiency of the system;

increase of the electric efficiency of the system;

decrease of the values of Tair,outlet-Tair,inlet.

It is also possible to observe that: the glass-glass 64 cells PV-module presents the highest values of thermal efficiency in respect to

other modules;

8/9/2019 DYN05 11 Bloem

12/16

12

the glass-glass 121 cells PV-module presents the worst electric behaviour in operating condition inrespect to the electric efficiency obtained in laboratory;

the electric efficiency of the glass-tedlar PV-module is better than tedlar-glass one.

5. MODEL DEVELOPMENT

The development of a calculation model, able to predict the performances of a ventilated PV facade is basedon the definition of equations describing the energy flows, both thermal and electrical, that take place in the

PV hybrid system.

Figure 16. Thermal energy exchanges in a PV hybrid system.

Some hypothesis has been made before beginning this treatment:

1. the thermal capacity effects have not been considered (hypothesis of quite- stationary state);

2. heat transfer within the system has can be considered as a one-dimensional heat flow;

3. the convective heat exchange between the surfaces of the gap an the air flowing in is considered in

the integral shape;

4. the air flow is assumed known.

Under this hypothesis the air-gap system could be represented by an electrical resistances model.

Figure 17.Electrical resistances model for a PV transparent double skin facade.

8/9/2019 DYN05 11 Bloem

13/16

13

5.1 Energy Balance

The analysis of the electrical scheme leads to the following equations of energy balance:

1. energy balance for the air gap

m

cp

(out

f

) = Ahcv1

(se

int

) + Ahcv2

(si

int

)

2. energy balance for the external surface of the air gap

3. energy balance for the internal surface of the air gap

where is the solar absorbance of different materials (glass, PV layer ), is the PV efficiency (functionof cell temperature and solar irradiance), N are distribution factors for theradiation diffusely absorbed byPV module. intis the temperature of air in the channel calculated as integral average:

The solution of the previous equations brings to the definition of se, si and int. It is also possible tocalculate out, the air temperature at the top of the air-gap, having in this way a valuation of the generatedthermal energy; the electrical power is calculated from the product of (Tpv,G) and the incident irradiationon the PV-cell surface.

The mathematical equations have been translated into a calculation code [Ref 27] using FORTRAN in order

to generate an executable program that could be inserted in the library of the TRNSYS simulation software.Using TRNSYSs definition it has been called Type83. A MainType 83 program has been generated also

that allows the use of Type83 in stand alone mode, thus without the TRNSYS environment.

Parameters requested by MainType83 are:geographic parameters (location);geometric parameters;thermal properties;

optical properties;parameter describing properties of PV elements inserted in the wall;

parameter describing the kind of double skin wall studied.

Input parameters required are:air temperature;

operating temperature of internal environment of the building;air flow;

solar irradiation on Horizontal surface;external relative humidity.

The main output given by the code are:surfaces temperatures;PV cell temperature;temperature of heated air leaving the gap;electric power generated by the PV system;thermal power generated;energy flows crossing the wall.

5.2 Validation and calibration of the model

The MainType has been applied to a configuration describing the TRE physical structure, in order to havean evaluation of the validity of results produced by the code. The input given to MainType 83 are the

8/9/2019 DYN05 11 Bloem

14/16

14

climatic data collected in Ispra and the air flow measured in the TRE air-gap. The output signals are Tse theexternal surface temperature of the gap, Tsi the internal surface temperature, Tcell the PV-cell temperature,

Tout the air temperature at the outlet of the TRE air-gap, Wel electric power generated by the inverter. Toassess an error of the calculation model a comparison between collected data and calculated results has beendone for each of the four PV-modules applied and for each of the four levels of air flow rate. A first resultfor MainType83 shows that:

Tsurfaces,calculated> Tsurfaces,measured

Tout,calculated< Tout,measured

The conclusion was made that the developed model under estimates the convective heat exchange betweensurfaces and air flow in the air-gap because of not correct correlations describing the convective heatexchange coefficient hcv. In order to investigate and to solve this problem a three-dimensional model of theTRE air-gap has been developed using FLUENT 6.0.2 software. The input data given to this model are themeasured data from the TRE (Tse, Tsi, Tout, and the air flow). The three-dimensional model allows studying

the fluid dynamic behaviour inside the TRE air-gap and it provided useful information to estimate correctvalues for the heat exchange coefficient hcv.

Figures 18, 19.Three-dimensional model of TRE duct and description of air velocity vectors.

It has been concluded that in particular the geometric configuration of the connection between the air inlettube and the TRE air-gap (elbow connection and sections expansion) creates strong local turbulences thatforces a sensible local increase of hcv. See also figures 18 and 19. From literature study and simulation with

FLUID an adjusted heat exchange coefficient hcv for this set-up has been defined. As a result the modeloutput improved.

The model shows a good agreement with the measured values for Tse and Tpv. A disagreement can be

found on Tsi; nevertheless this could not be considered a real error in fact it could be observed that thisbehaviour is generated by a time advance of Tsi, calculated on Tsi,measured. This depends from the fact

that (small) thermal capacity effects have not been taken into account.

This approach can be considered correct for a double skin facade (composed of a light frame). But theTRE has an internal opaque surface whose thermal capacity couldnt fully be neglected. This effect is very

weak on the PV-module, as by hypothesis for light frame. The behaviour observed on Tsi influences alsoTout, where it is possible to observe a similar time translation between measured data a model results.

8/9/2019 DYN05 11 Bloem

15/16

15

Figure 20. Calculated and measured electrical output during a specific sunny day.

When it concerns the electricity generated by the system, the energy output predicted by the model is ingood accordance with the measured one. An error less than 5% for the daily energy production isachievable.

6. CONCLUSION

The work carried out by a number of research organisation, most of them Paslink members, over the last tenyears in several European projects have improved the understanding of the complex interaction of PVtechnology with the building boundary conditions. It is expected that this expertise will be needed in the

near future when PV and construction industry will focus on true integration of the PV technology in thebuilt environment. Meanwhile the established research organisations should continue in developing andimproving performance assessment procedures including experimental set-ups, calculation methods,

modelling and design tools. Further developments for both the experimental and modelling work should bemade in relation to solar energy technology as required by the Energy Performance Directive for Buildings.The definition of an improved and standard Test Reference Environment for BIPV applications has to bemade in the near future. This new structure will have to be based on the results from this study. Theexperimental work will produce data for the validation of calculation models for BIPV applications that areexpected to become more frequent in the coming years.

REFERENCES

[1] Wouters P., Vandaele L., Bloem H. Hybrid Photovoltaic Building Facades: The Challenges for anintegrated overall Performance Evaluation. In the Proceedings of the Conference on Solar Energy inArchitecture and Urban Planning, Berlin 26-29 March (1996).

[2] L. Vandaele, P Wouters, J. J. Bloem, W.J. Zaaiman, Combined heat and power from hybridphotovoltaic building integrated components: results from overall performance assessment., Proc. 2ndWorld Conference and Exhibition on Photovoltaic Solar Energy Conversion, Vienna (1998).

[3] J. R. Bates, U. Blieske, J.J. Bloem, J Campbell, F. Ferrazza, R. J. Hacker, P. Strachan,

Y.Tripanagnostopoulos, Building Implementation of Photovoltaics with Active Control ofTemperature, Building IMPACT Final Results Proceedings of the 17thPV Conference, Muenchen

(Oct 2001).

[4] J.J. Bloem, W. Zaaiman, C. Bucci, V.R. Nacci. "Proposal for a PV Reference Module and a TestReference Environment for BIPV Applications". Proceedings of the 16thPV Conference, Glasgow

(2000).[5] M. van Schalkwijk et al. "PRESCRIPT - Towards a European standardisation of PV building

8/9/2019 DYN05 11 Bloem

16/16

16

components". Proc. 2nd

World Conference and Exhibition on Photovoltaic Solar Energy Conversion,Vienna (1998).

[6] PV Cool Build A design guide; EC FP5 project NNE5/2000/115. www.pvcoolbuild.com

[7] Nordmann T. Built-in Future. Renewable Energies Vol 8, no 4, 236-247 (2005).

[8] Jger-Waldau A. (ed.). (2004) Status Report 2004; Energy End-use Efficiency and Electricity from

Biomass, Wind and Photovoltaics in the European Union. EUR 21297 EN (2004).[9] IEA PVPS Task 7; Photovoltaics in the Built Environment. Extract published in Renewable Energies

Vol 8, no 3, 140-149 (2005).

[10] EPIA and Greenpeace (2004). The Solar Generation report.

[11] DIRECTIVE 2001/77/EC Promotion of electricity produced from Renewable Energy Sources in theinternal electricity market.

[12] DIRECTIVE 2002/91/EC on the Energy Performance of Buildings.

[13] Bloem J.J. Overcome barriers for private investment into photovoltaic in the residential builtenvironment. 20thPV Conference, 6-11 June 2005, Barcelona.

[14] Bloem J.J., Baker P.H. Building Integration Issues for Photovoltaics ". In the Proceedings of BIAT -Technical Innovation in Design and Contruction - Dublin Castle, 23-24 November 2000.

[15] Bloem J.J., Baker P.H. Strachan P.A. Energy Performance of Buildings and the Integration ofPhotovoltaics. EECB Conference, Frankfurt (2004).

[16] Bloem J.J., Baker P.H. Strachan P.A. (2000). PV Solar Systems in the Built Environment; Specificrequirements for Integration, Energy Monitoring, Analysis and Control. 6th European Conference :Solar Energy in Architecture and Urban Planning, Bonn (2000).

[17] Bloem J.J., Baker P.H., Stirling C. PV Systems and specific requirements for Building Integration.Proceedings of the 16thPV Conference, Glasgow (2000).

[18] IEC 1215 (1993), Crystalline silicon terrestrial photovoltaic (PV) modules Design qualification andtype approval.

[19] A. Gandini. Analisi numerica delle facciate fotovoltaiche a doppia pell, Politecnico di Milano(2003).

[20] J.J. Bloem, BIPV Case Study for modelling and analysis. Proceedings of the DAME Conference,

13-14 November, Ispra (2003).[21] J.J. Bloem, R. van Dijk. The PV module considered from an energy flow perspective. To be

presented at the 16thPV Conference, Glasgow (2000).

[22] D. van Dijk, R. Versluis, PV-HYBRID-PAS: Results of Thermal Performance Assessment,Proceedings 2

ndWorld Conference on Photovoltaic Solar Energy Conversion, Vienna, (1998).

[23] Bloem J.J., Jger-Waldau A., Colli A.(2005) Economic Analysis Of Photovoltaic Shading Devices InThe Mediterranean Built Environment. 20thPV Conference, 6-11 June 2005, Barcelona.

[24] L. Vandaele, A Deneyer, N. Heijmans, F.Dobbels. (May 2005). Innovative low energy renovation of asingle family dwelling for summer comfort. PALENC Conference, Santorini, Greece (19-21 May,2005).

[25] Bloem J.J., Colli A., Strachan P.A. Evaluation of PV implementation in the Building Sector. PALENCConference, Santorini, Greece (19-21 May, 2005).

[26] Numerical analysis of PV double skin facades. Proceedings of the DAME Conference, 13-14November, Ispra (2003).

[27] Bloem J.J., Gandini A., Mazzarella L., A TRNSYS Type Calculation Model for Double SkinPhotovoltaic Facades. Workshop on Dynamic Analysis Methods applied to Energy PerformanceAssessment of Buildings, Warsaw, Poland (13-14 May 2004).