Designing car park shade structures – Rules and best practice
What are car park shade structures used for?
Photovoltaic shade structures are becoming increasingly popular for their dual function: providing shade for parked vehicles while producing renewable energy. However, the design of these structures requires compliance with certain rules and good practice. In this article, you’ll discover the key factors to consider when designing high-performance, sustainable photovoltaic car park shade structures.
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Rules and best practice
Geometry and adaptation to parking spaces
More than 90% of photovoltaic shade structures are built on existing car parks, which means that the width of the parking spaces already exists. This width can vary from 2.35m in town centres to 2.70m in supermarkets on the outskirts of urban centres. Suppliers of photovoltaic shading systems must therefore take this requirement into account.
The single-post geometry with a concrete foundation is the most commonly used, particularly for double-row car parks. This configuration allows the post to be positioned at the edge of the vehicle parking area, and is therefore adaptable to the variable width of the span spanning 2, 3 or even 4 parking spaces. The single-post is also the only technical solution for car parks arranged in a herringbone pattern.
Shade structure and height
In order to optimise the number of covered spaces with the least number of posts and foundations, a lateral offset of a complete parking space is generally provided on either side of the parking row.
The height of the roof ridge is determined by the position of the lower edge, which in turn depends on the type of vehicles using the car park (H1, H2, H3 or HGV) and the angle chosen for the roof, generally between 5 and 15 degrees.
The post, crossbeam and braces together form a portal frame. The portals are linked together by purlins, cold-formed Z or Omega type, thus forming the primary structure. The integration system that holds the photovoltaic modules is installed on the purlins and is made up of special W-shaped rafters (or omega rafters), providing both rainwater drainage and mechanical fastening of the modules.
Environmental integration
Rainwater management is an important aspect to consider when designing a photovoltaic shade. Soil desiltation is a major issue, and the creation of infiltration trenches at the end of the slopes created by the photovoltaic modules is a possible solution. In addition, the combination of a shrub layer on the north side of the slope will create cool spots, which are particularly useful in an urban environment.
Regulatory framework and applicable standards
It is essential to take into account the regulations in force when designing a photovoltaic shade structure. For example, it is possible to combine a photovoltaic shade structure project that complies with the French Renewable Energy Acceleration Act (EnR) with the installation of charging stations for electric vehicles (EVs), in accordance with the French Mobility Orientation Act (LOM). This combined approach offers synergies and the potential to cut costs at every stage of the project.
In France, two standards are particularly relevant to the design of photovoltaic car parks: NF P 91-100 for car parks accessible to the public and NF P 91-120 for private car parks. These standards define the requirements for the design, construction and maintenance of car parks, as well as their dimensional and functional characteristics.
Optimising performance
The choice of components is crucial to guaranteeing optimum yield from the photovoltaic shade. Opting for a bi-glass or bi-facial module offers significant optimisation (6% to 12% depending on the manufacturer), thanks in particular to the ventilation on the underside, which is ideal for a shade structure. To increase the albedo, the use of loose white gravel on honeycomb-type infiltrating pavements is also a solution worth considering.