PV-INTEGRATION IN SOLAR SHADING (RENOVATION) AND PV-INTEGRATION IN ATRIUM GLAZING(NEW BUILDING), ECN 31 AND 42 - PETTEN (NL)

ir. Tjerk ReijengaBEAR Architecten

P.O. Box 349, NL-2800 AH Gouda, The Netherlandstel.: +31 182 529899,fax: +31 182 582599,e-mail: tjerk@bear.nl,internet: www.bear.nl

The renovation of laboratory building 31 and the new office- and laboratory building 42 of the NetherlandsEnergy Research Foundation ECN in Petten are a good examples of the building integration of photovoltaicenergy. Besides, the buildings demonstrate and increase the know-how and experience of the company on thesustainable use of energy in the built environment.The laboratory (building 31) was built in 1963 and is (during the renovation) equipped with a PV integratedsun shading system for the south facade and a PV roof. The capacity of the system is about 72 kWp. Thebuilding lay-out of the new building 42 is designed to lower the energy use by maximising solar gain and theuse of daylight. The glass-covered corridor on the first floor, with its entrances to the laboratory and office-modules, is the connecting element between the existing laboratory building 31 and the new building 42. Theuse of photo voltaic laminates in the curved glass roof prevents overheating in summer and provides diffuselighting. The capacity of this PV system is about 43 kWp. More information can be found on the website:www.bear.nl.Keywords: Building integration - 1: Photovoltaic - 2: Shading – 3: Sustainable

Figure 1: ECN buildings 42 (left) and 31 (right).

1. INTRODUCTION

1.1 Aim of the projectThe aim of the project is to construct energy-

efficient and sustainable buildings and demonstrate theuse of renewables in the built environment. Both, theretrofit of building 31 and the new office- andlaboratory building 42 of the Netherlands EnergyResearch Foundation ECN in Petten are a demonstrationof these aims.

The projects are supported by EU Thermie, NOVEMand the utility NUON.

In order to make PV more economical, PVintegration in buildings is an option that may savemoney on supporting systems, savings in roofingmaterials, and savings in floor space.

2. APPROACH

2.1 ECN PettenThe buildings are located at the site of he

Netherlands Energy Research Foundation ECN in Petten,the Netherlands. ECN is attractively situated in thedunes in the Northern part of Holland, close to thevillage of Petten.

2.2 Building 31In 1997 the ECN unit for ‘Renewable Energy in the

Built Environment’ made a study to evaluate thebuilding condition of laboratory building 31 as well asfacts of energy consumption. The survey showed thatthe existing building (constructed in 1963) has severalmajor technical and thermal shortcomings, which willbe taken care of in the renovation process.

Building 31 had several technical and thermalproblems:

• bad insulation of the envelope and thermal bridges;• overheating in mid summer; inefficient lighting

system;• high rate ventilation system for the laboratories

with low efficiency and comfort;• high heating and electricity demand;• facade in bad condition led to draught due to

thermal bridges;• draught, due to ventilation system and badly

distributed heat.Table 1: Problems of laboratory 31.

For the laboratory 31 a PV-integrated shadingsystem have been designed. The project is a co-operation between ECN, BEAR Architecten, utilityNUON, Shell Solar Energy and the Italian architectCinzia Abbate (Rome). The Danish manufacturerDasolas/Alco is involved in producing the combinedPV support / sun shading system.

Figure 2: Integration of PV in solar shading(building 31)

To prevent overheating during summertime, thesouth façade has been provided with sunshades. PVmodules have been integrated in this shading system.To optimise solar gain there needs to be a certaindistance between the lamellas of the system. For finetuning the shading system, a simple second system i splaced on the inside. Furthermore, the shading systemdiffuses the daylight and the structure allows easy

access to the façade for building maintenance andwindow cleaning.

A PV roofing system has been designed andinstalled in co-operation with BP Solar. The installedcapacity of the system is approx. 35 kWp.

When the building renovation is completed, theprimary energy demand will be reduced with 75%. Theamount of PV that will be applied is about 72 kWp :50% integrated in the façade and 50% at the roof. Alltogether the PV system will produce about 56,440 kWhper year.

The renovation project is part of the EC Thermieprogram (SE 0115/97/NL/DK) and financially supportedby the EC. The project is constructed in the years 2000-2001.

2.3 Building 42The office building 42 consists of three building

units. The construction of the first unit is finished inMarch 2001. The other unit’s wil be built in the nextyears.

Figure 3: The corridor between the buildings.

The building has been designed to maximise the useof daylight and to minimise the use of artificial light.To accomplish this the structure of the building i scompact and the building has several atriums allowing amaximum use of daylight. All working places aresituated in the daylight zone near the facade. The glass-covered corridor on the first floor, with its entrances tothe office-units, will be the connecting element betweenthe building. The use of photovoltaic cells in the curvedglass roof and a lot of natural ventilation preventoverheating in the summer. The 43 kWp PV system i sinstalled by BP Solar.

Realized options for building 42:• compact building form;• high insulation values for floor, roof, windows and

facades;• unheated corridor (conservatory) space as a climatic

buffer;• reduction of cooling load by the ventilated corridor

with PV glazing (parasol idea);• daylight controlled artificial lighting system;• ventilation concept with heat recovery system;• natural summer night ventilation by automatic

opening windows;• optimized daylight through the corridor and atrium;• air-heating system to cover the low demand.

Table 2: Options realized in building 42

3. THE PV SYSTEM

3.1 Building 31, the façadeThe building had a problem of overheating in

summer. An outer sunshading system was necessary. Itwas clear that the PV modules should be integrated inthe sunshading system. Such a solution may:• give good shading of the building in summer;• optimize solar gain;• diffuses daylight;• give easy access for maintenance of the building and

cleaning of the windows (maintenance walkway).Besides there is more than one reason that justifies

the use of integrated PV modules in the shading device:construction costs will be optimized by the eliminationof costs of a conventional PV module support system;interior light and temperature will be improved andenergy is produced directly where needed.

The choice should be made whether the shadingdevice should be mounted close to the facade or at acertain distance. Furthermore, the size of the lamellashad to be discussed: should a few, wide lamellas bechosen or a larger number of slim ones? What should bethe length of the lamellas?

From the point of view of maintenance, accessibilityand window cleaning it was decided to have theshading/PV device constructed as a separate facade,about 80 cm from the building, connected to the mainstructure of the building. The length of the lamellasfollowed from the building structure grid.

In order to make a choice for the width of thelamellas various solutions for an integrated system wereexamined:• two large lamellas with modules, at a vertical

distance of 1.5 m in a fixed position;• idem with moveable tracking system;• seven small lamellas with modules, at a vertical

distance of 0.5 m in a fixed position;• idem with moveable tracking system.

The study was carried out with a model of alaboratory room scale 1:10 in a daylight chamber andon a solar table. It focused on the solar gain, the heatload of the building, shading of the building, shadingof the modules, outside view from the interior anddaylight conditions. This study showed, that the bestresults for solar gain, shading and daylight wereobtained with a model using 4 fixed lamellas per floor.Considering the solar ratio between a fixed verticalsystem and a moveable vertical system, the solar gain i sonly approximately 10% higher with a moveable one.

Considering the high costs of a moveable systemcompared to a fixed structure, and the small differenceof solar gain it was decided to select a system that i sfixed in the optimal position (in the Netherlands 37°with the horizon). However, the occupant of the roomsbehind can move one lamella, at eye level, in ahorizontal position, in order to have a good outsideview. After a defined space of time, for instance 20minutes or so, the lamella will automatically take itsposition of 37° again. Thus, a continuously varyingarchitectural view is created.

Each lamella will be about 840 mm wide, 3000 mmlong and will be covered by three standard multi-crystalline PV modules on the front part. Because of thedimensions of the lamellas the building is shaded

during the summer period. The efficiency of the shadingsystem is about 85%. For fine-tuning the glare,especially in winter, a second, very simple interiorshading system is provided.

Because of the new exterior PV/shading systemoverheating of the south facade will be avoided and anexpensive, energy consuming, air-conditioning systemis not necessary.

As far as can be predicted from the study, thespecific position of the lamellas might improve thedistribution of the daylight in the rooms compared tothe existing situation. The daylight situation throughthe rooms might be more equal. However, to be sureabout the effect of the integrated PV/sunshading systemon the delighting of the rooms behind, a separate studyis carried out. This study, consists of advanced daylightcomputer simulations. After evaluation of the results amock-up has been built, followed by measurements. Butnot only daylight aspects are examined by means of themock-up. Also constructive implications, deteriorationof moveable construction parts, questions ofmanufacturing, color and acceptance by the users of thebuilding are examined in the prototype stage. Byspending time and money for the prototype, mistakesare avoided in the construction phase.

3.2 Building 31, the roofing systemThe PV roofing system was originally meant as a

kind of a parasol, a passive-cooling device for the roof.The roof construction underneath should provide watertightness. As the design of the interior of the buildinggot more and more shape, it became clear that the spacebetween the parasol and the existing roof should beused for technical installations. So it was decided toconstruct the parasol as a watertight part of thebuilding.

Figure 4: The roof of building 31

3.3 Building 42Special emphasis has been given to architectural

and constructional aspects of integrating the PVmodules in the building.

The glass-covered corridor on the first floor, with itsentrances to the office-modules, is the connectingelement between building 31 and building 42. In theroof of this unheated and strongly ventilatedconservatory, PV modules are integrated. Thetransparent modules have a 2 centimeters free spacebetween the cells. Thus providing daylight in theconservatory. In this way the use of photovoltaic in the

curved glass roof prevents overheating in summer andprovides diffuse daylight. The glass roof is like aparasol for the building under it.

4. SCIENTIFIC INNOVATION AND RELEVANCE

The scientific innovation and relevance of theproject are high. The PV system is architecturallyintegrated in the buildings. The use of solar energy hadan important role in the design process. The projectshows how new sustainable concepts enriches thearchitectural value of buildings.

The interest in the project, both from national andinternational sides, is large. Thus the project mayencourage the application of PV systems. Theinnovative constructions for PV integration in the roofsand in the facade contributes highly to the reduction ofheat load of these buildings. Thus, energy consumingair-condition equipment is avoided.

The project is regarded as innovative because of itscontribution to new developments in the sun shadingindustry, the architectural solution, the integration ofPV, shading, passive cooling and daylight, the goodoutside view by moveable lamellas and the good insideview by diffuse lighting. Integration of PV systems inshading devices or in atriums can result in considerablecost reduction.

5. RESULTS / CONCLUSIONS

By integrating PV systems in buildings, a betterquality/cost ratio will be attained. The architecturalintegration has a high relevance. These buildings are agood example of building integration of photovoltaic.The concept of the new building has good potentialitiesto fit all kind of alternating organisations in the future.