he Energy Arch - "De Energieboog"

General information
As a spin-off of IMEC, Photovoltech nv. became one of the most important European producer of multicrystal- line silicon solar cells. Photovoltech was founded in 2001 and has three major shareholders namely Total, GDF Suez and IMEC.

After the first years of investments in the solar cells development and an industrial expansion, the company decided in 2007 to install, on their own business estate, the first electrical production photovoltaic unit. The challenge that was given to the design team, was to create a construction for this photovoltaic production unit on the same innovative manner such as Photovoltech does with the production of their own solar cells.

The main target in the design was to anticipate carefully with the orientation and geography, the existing buildings and the planned developments of the company in the future. Taken into account these prior conditions the architectural construction should also to be considered as a landmark of new technology development of solar energy in the region of Tienen - Belgium.

Concept of the Arch
After a careful engineering of wind loads, soil characteristics and finally the possibility of shadow impact from surrounding buildings or from the panels itself. The choice was made to use a segment of an ellipse, to support the photovoltaic panels. The idea of "The Energy Arch" was born. -

The design of the arch and the fixation of the PV-panels
The external sphere from the ellipse segment is formed by 5 metallic columns, which are horizontally connected with 21 metallic beams. Every 100 cm a point is determinate on the ellipse segment, from this point a circle, with a diameter of 200 cm, is drawn. From each intersection point of the ellipse segment and the circles, a tangent is drawn and the bisector is calculated. These lines define the position of the horizontal metallic beam and the exact position of the PV-panels. The complete construction is supported by a concrete foundation anchored with 8 concrete piles into the ground. -

All panels are serial electrical interconnected in 9 loops and are producing a total capacity of 50.000 KWh/year. The front (skin) of the arch is chapped, joint less by 280 panels, each 1 m by 1.5 m with a peak power of 200 Wp. The choice of using a galvanised metallic ellipse construction create a perfect integration with the existing building and gives the impression to have an infinitude transitional skyline between the blue silicon cells and the blue sky.

Elliptical construction
Definition, characteristics and calculation of the ellipse
In mathematics an ellipse is the apparent shape of a circle viewed obliquely. An ellipse is a two-dimensional figure which can be defined as the locus of points in a plane such that the sum of the distances from the moving point (red line in the figure) to two fixed points, called foci (f1 and f2 in the figure), remains constant.

Design of the Arch of Energy and the orientation of the PV-panels
The tangent is the bisector of the angle formed by the focus-tangency point-focus. The 2 foci are imposed points with which the ellipse can be drawn.