paper

Integration of Solar Energy Systems
in Architecture

Ir. Tjerk Reijenga M.Sc. (BEAR Architecten)

SYNOPSIS: The use of solar energy in the built environment is one of the most challenging and promising possibilities to save fossil energy. Solar energy can be used by design (passive solar energy), by the use of thermal solar collectors for domestic hot water (SDHW) and by the use of building integrated photo-voltaic systems for electricity (BIPV). New technologies and materials are an invitation for the designer.
BEAR Architecten is involved in several low energy, bio-climatic building projects, amongst them, several solar projects:
· Row housing in Amersfoort-Nieuwland with solar panels in the roof.
· conservatories and solar collectors in 26 houses in Schiedam-Spaland.
· conservatories with roof integrated solar panels in 35 houses in Amsterdam-Banne Oost.
· Roof retrofit with 11.5 kWp PV modules in 5 houses in Leiden.
· Facade integration with 23 kWp PV shading devices in 22 houses in Dordrecht (Thermie).
· Roof integration with 4.2 kWp in a utility building in Geldermalsen.
· De Kleine Aarde in Boxtel (NL), an Environmental Education Centre with an unheated corridor with 7.8 kWp PV panels in the glass roof (Thermie).
Information about these projects is given. But also the possibilities and the problems will be discussed here. A general conclusion is that custom made solutions are often necessary to make well designed buildings.

Keywords: Building Integration - 1; Roofing Systems - 1.

To make solar-systems more accepted, attention has to be given to the architectural aspects of building integrated solar energy. These architectural aspects are also one of the issues within the European Thermie programme.
In several towns, like Amersfoort, Heerhugowaard, Schiedam, Gouda, Apeldoorn and many others, the local authorities have a policy of promoting solar energy in the build environment. The regional utilities have an environmental policy that supports this local policy.

Housing in Amersfoort-Nieuwland.

In the new town quarter Nieuwland in Amersfoort BEAR Architecten designed a plan with 126 houses. Solar collectors are used in about 60% of the houses. To place the approx. 2.6 m2 collector is a simple matter. The roofs have concrete tiles and the collector system can be placed like a roof window. In the design we had to choose a shape for the collectors. In general there are 3 possibilities: portrait, landscape or square. In this project we choose for portrait.
At the corners of the rows the houses have flat roofs. Here we used a frame for the collectors. To give this frames a less technical and more designed image, the frames are cladded with perforated metal sheets.

Beside the technical aspects, the implementation of solar panels in the developing and building process is interesting. The housing project is partly social housing owned and rented by a housing association. These houses has solar panels that are leased by the utility.
The other houses have been sold. The house owners had to decide, individually, if they wanted to buy or rent a solar hot water system. In practise only a few people (approx. 10%) were interested. This means that good publicity and information has to be given to consumers to convince them of the advantages of solar energy.

Figure 1 Solar collectors in Soest

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Conservatories in Schiedam.

The town of Schiedam has a policy since the early '80 on solar energy. all new build houses has to be designed with passive solar energy and solar collectors. The energy consumption of an average (300 m3 volume) house has to be 700 m3 natural gas (2,5 m3 gas/m3 volume) for heating.
In 1991 we made a plan for 26 houses with attached conservatories and solar collectors for hot water. The houses are insulated with a R-value of 3.0 and 3.5 s.i. Glazing has U-values of 1.9 s.i.

Figure 2 Conservatories in Schiedam

The plan of the houses is facing south. Living room and children's bedrooms are on the south facade. Entrance, kitchen, bathroom and parents-bedroom are on the north side. On the second floor is a studio with sun terrace.
The conservatories is almost two storeys high and is used as buffer zone and for pre-heating the ventilation air. The conservatory is not heated in winter.
On the terraces we planed the solar collectors. This place was chosen because it is the best, unshaded place in winter. Actually this collector is not integrated in the construction but well placed in the design of the house. The reason for this choice was just the money.
Because of the passive solar the roof faces north and the windows faces south. Our first design for a small south facing roof with solar collector was calculated and would raise the building cost with more than Dfl 1500.- . This is 50% of the cost for the solar collector.
To save energy we made two hot water groups. One for the kitchen and one for the bathroom. For safety reasons we used a thermal mixer valve. This valve brings the high temperatures back to a maximum of 60°C.

Figure 3 Detail of the conservatory

Roof retrofit in 5 houses in Leiden.
The Zonnewende project consists of ten houses, five of which have been equipped with PV systems during recent renovations. Originally, all ten houses had solar thermal systems installed on the roofs. Constructed in 1977, the houses were the first in The Netherlands utilising active solar systems for both hot water and heating.
Through the years, most of the systems have been deactivated due to malfunctioning. In addition, poor detailing of the roof-integration design of the collectors led to severe leakage problems, leading to the necessity of renovation.(continue)

Figure 4 Solar roofs in Leiden

In 1993 the original roofs were in poor condition. There was no moisture or damp barrier in the construction and leakage problems often occurred, either caused by roof problems, malfunctioning of the solar collectors or condensation inside the construction.
In the new construction, the PV modules are mounted in profiles originating from greenhouse technology. At the rear of the PV modules a cavity is required, both for ventilation as well as for the connector boxes on the back side of the modules.
The houses originally had two 60° tilted collector areas on the south side of the roof and a tilted roof on the north side. The collector areas are separated by a roof terrace.
Some occupants had specific wishes concerning the renovation, for instance, a dormer in the lower roof, or the replacement of the terrace by an additional bedroom. In order to meet these wishes, and to allow future construction of dormers or replacement of terraces, the following roof zoning was applied:
* Three zones for the solar panels (the 'PV-zones'): two in the lower roof and one in the upper roof. These zones are not affected by dormers or extensions of the building.
* A zone in the central part of the lower roof which may be needed to install a dormer. In the upper roof, a zone is defined which may be needed to build an additional bedroom. These two zones will not be used for PV systems.

Figure 5 Detail of dormer windows and PV modules

Based on the size of the entire roof, it is possible to mount 70 modules on each house. Because of the shading of the panels by the dormer, the panels next to it are omitted. By utilising only the PV zones, the number of PV modules is reduced to 48. The 2.3-kWp PV installations thus created, consist of 48 mono-crystalline R&S IRM modules with a 1.8-kW Sunmaster inverter which is under designed with respect to the peak power to an extent of 78%. The system is grid-connected.
PV nominal power/house 2,300 Wp
PV nominal power/total 11,500 Wp
PV-system operating hours 4,400 hours/year
The PV-system is manufactured and assembled by R&S (Helmond, The Netherlands). The project is financed by the NOVEM, EWR (utility) and the owners of the homes.(comtinue)

Solar integration at De Kleine Aarde.

The project De Kleine Aarde or The Small Earth is a visitors information centre for ecological building, gardening and biological nutrition.
Because of the increasing interest in the environment and in energy conscious building, the centre has to build a bigger visitors centre. This new centre will function as an education object itself. The whole building, the construction, the heating and other installations have to show how to build in an ecological and energy-conscious way. The starting-points for the design are: compact building mass, utilising passive and active solar energy, functional and thermal zones, optimising artificial lighting, the indoor air quality, solar ventilation, a flexible structure with columns, ecological building materials, etc. Within the column structure different walls, insulation materials and glazing are demonstrated. Walking through the sunny corridor with its PV-integrated roof is a happening for the senses and for the mind.

Figure 6 Corridor interior

The brief consists of a visitors centre, a book shop, a restaurant with kitchen, recreation- and coffee room, office space and bedrooms on the first floor for the participants of the course. For a clear understanding the program is split in a visitors part and an office and accommodation part.
Solar energy is used in three ways: passive solar through the windows, active solar for domestic hot water and a PV-system.

Figure 7 The solar roof

The solar collectors are integrated in the roof of the engine room. It is well integrated in combination with glass. For the construction we used greenhouse profiles.
The PV system has, besides the energy production function, also the function of covering a street and protecting it against cold, wind and rain.
For a building contractor there is no essential difference between a glass pane and an unframed solar module. This means that the costs for integrated unframed solar modules in a glass construction will be lower.
The 33 meter long and 5 meter wide corridor functions as an inner street. It is the circular room between all other rooms. In winter the corridor is only heated by the solar gain through the glass roof. No auxiliary heating is provided. There even is a possibility of frost in wintertime. It also means that we could use single glazing and a minimum quality in aluminium profiles. Condensation at the inside of the glazing is drained away by the profiles into a gutter.
The walls between corridor and office space are well insulated. Because of the solar gain and the gain of energy losses from the adjacent building parts the temperature in the corridor will be more than 7°K higher than the outside temperature. For Dutch climatic conditions it means an average heating season temperature of 12°C. Ventilation air from the corridor will be used for visitors centre and office space. This means a reduction of energy losses by ventilation.
In summer the sun will heat up the corridor. To prevent overheating, normally an outer shading device is needed. By using the glass roof integrated PV system, the solar transmittance of the glass can be lowered and overheating can be prevented.

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Figure 8 Cross section over the corridor

In summer more ventilation of the corridor is needed. The vertical glass between green roof and glass roof can be opened for about 25 meters. At the highest point of the glass roof there are also 25 meter of ventilation windows. By building up heat under the roof, the chimney-effect will push the warm air to the outside at the highest point and cooler air (crossing the evaporating green roof) will enter the corridor.
Besides the floormass, a water basin is used to accumulate heat. On hot days the accumulation, together with evaporation from the plants and the water basin, give a more comfortable indoor climate.
No cooling is needed for the offices. Because the heat is ventilated away in the corridor, the rooms behind the corridor will stay cool (there is good experience from an earlier project). A second ventilation possibility at the north side of the rooms gives fresh outside air in summer.
According to calculations made, the transparent PV modules are a good choice in relation to aspects as passive solar, day-lighting, diffusion of light, transmission, condensation, overheating and energy production.

Support for the project is given by the European Community and Novem because of the architectural integration of PV in the building. (EC project Thermie SE 104/93/NL)
PV nominal power/total 7,956 Wp
PV-system operating hours 4,400 hours/year
The PV-system is manufactured by GSS (Gera, Germany) and assembled by BST/Stroomwerk (Terheijden, The Netherlands).

Conclusions.

1. For optimal building integration of solar energy the architect needs a lot of information.

2. The dimensions of solar components are not based on (measurement) agreements in the building industry. A more spread range of dimensions is recommended. Custom-made panels are also needed.

3. More choices in the colour of panels and profiles is needed to make good looking combinations. Architects are in common very enthusiastic with the use of the blue or black poly-crystalline colour in a building design but less enthusiastic for the black boxed solar collectors.

4. Guarantees on building constructions with solar components are needed. To enlarge the scale of SDHW and BIPV, the component must be applied in the same way as other building materials.

5. Information for the consumers is needed to make them enthusiastic.

Literature

·Drs. W.O.J. Böttger, drs. L.E. de Graaf, drs. M. van Schalkwijk, ir. A.J.N. Schoen, ir. T.H. Reijenga, ir. P. Blesgraaf, Voorstudie integratie PV-modules in vliesgevels, grote glasoverkapte ruimten en zonweringen (Preliminary study PV-modules in glassroofs and -facades), Ecofys E 263 - NOVEM, Utrecht, 1996.
· Ir. T.H. Reijenga, 'Leiden, renovatie van daken met PV-modulen', Met de zon de markt op, Vijfde Nederlandse Zonne-energie conferentie, Veldhoven 1995.