Page 194 - ELEMENTS EUROPA (EN)

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THE PHOTOVOLTAIC UMBRELLA
AN UMBRELLA SHELTERING THE EUROPA BUILDING
The new seat of the Council of the European Union just
has to have a sustainable footprint. Its whole architecture
and technical design reflects this requirement, in most cases
without it actually being visible. Nevertheless, as with the
patchwork facade of recycled wooden window frames, the
building’s photovoltaic umbrella constitutes a visible and
public manifestation of the Council’s positive position on the
environment. Airily surmounting the building’s old and new
parts, the umbrella symbolises the typically European tradition
of building the future without ignoring the past.
The umbrella consists of a platform of very transparent steel
grating panels supported by a slender structure well above the
roof and serving as a support for the parallel rows of sloping
photovoltaic panels.
The umbrella has a number of functions, over and above that
of producing electricity: it filters the light falling on the atrium’s theoretical optimum (37° inclination and facing south)
glass roof, allows maintenance of the photovoltaic panels,
affirms the building’s urban presence through giving it “wings”,
and brings order to the plethora of equipment installed on the
roof.
On account of its pure, regular and orthogonal design,
the structure exudes a serene lightness. It is made of simple,
very slender (100 x 100 mm) tubular profiles whose buckling
is prevented by cross bars of the same section, arranged in
line with the building’s modular design. All X-shaped braces
are grouped as an L, rising up between the various pieces of
equipment.
THE PHOTOVOLTAIC INSTALLATION
The photovoltaic installation consists of 636 panels. As each
of the 2,288 x 1,312 mm panels has 96 monocrystalline cells
measuring 156 x 156 mm, the total number of cells is 61,056
cells. They cover 1,485.86 m² of the net active surface area.
Offering a peak performance of 251.22 kWp, annual AC
production – averaged over 20 years to take account of aging
– is calculated at 235.6 MWh / year, i.e. the annual consumption
of 59 families of 4 people, or more than 4% of the building’s
annual electricity consumption (a pessimistic estimate based on
the consumption of the neighbouring Justus Lipsius building).
Specific AC performance – averaged over 20 years – is
calculated at 938 kWh/kWp, i.e. a performance ratio of 85.83%.
The panels are inclined 30° horizontally and face south-
south-east (205.4°), offering a yield of approx. 97% vis-à-vis the
The photovoltaic installation does not just involve rows of
standard “solar panels”, but is the overall result of a “BIPV”
(Building Integrated PhotoVoltaics) approach. While the
sole purpose of standard photovoltaic panels is to produce
a maximum amount of electricity – meaning that they are
made of juxtaposed cells determining the dimensions of the
panels and making them opaque –, the BIPV approach involves
considering the photovoltaic function as a property added to
a glass construction element which also fulfils other functions.
In this case, it is imperative for large amounts of sunlight to
filter through the panels to light up the atrium. It is similarly
imperative that the panels’ dimensions fit in with the umbrella’s
modular structure. This is why the cells in each panel are laid
out at a certain distance from each other, following a layout
that offers significant light transmission (22% of the surface in
extra-clear glazing) and that respects the 1.35 m module size,
yet without any loss of electrical power.
Moreover, as required for facades or roof lights, the panels
have to be subjected to a soft impact test to ensure the safety
of the installation in the event of a storm or hail, or during
maintenance. The extra-clear glazing is 10 mm thick and its
solidity is ensured by a transparent Tedlar® film glued to the
back of each panel.
The photovoltaic umbrella provides a good illustration
of the close link between technology and architecture. For
instance, the dramatic fall in the cost of photovoltaic cells over
the past few years suggests that a “BIPV” approach applied