Photovoltaics on a difficult roof - Lerta

Photovoltaics on a difficult roof

Photovoltaics. A bird's eye view of the installation on the roof of an office building


A 50 kWp photovoltaic installation that no one wanted to undertake due to the very difficult installation conditions.


The owner of a building with office and service premises located in the Lesser Poland Province, asked us to design and install a photovoltaic installation which would supply a strictly defined amount of energy. Other contractors were unwilling to undertake the project due to the complexity of the roof area on which the installation was to be mounted and a number of other difficulties, which we outline below.


Difficulties arising from the challenge

What have we done?

We started with an energy needs audit to determine how large the installation should be to produce the amount of energy the customer needs under these difficult conditions, while ensuring that the installation is no larger than 49.97 kWp, which allows gaining the prosumer status. The production simulation determined the selection of the top performing Longi Solar Hi-MO4 modules. These had to be high power modules, as there was not enough space on the roof for a large number of inferior cells.

The installation proved to be a real challenge. The load-bearing capacity and also the amount of space on the roof surface did not allow for the use of ballast structures, so we decided to use a system glued to the roofing felt, which required the work of a roofer, not just an electrical fitter. Fortunately, we have a specialist with such qualifications and experience in the installation team, which made the installation much easier. The height of the building required the use of a crane, so prior to the installation work we had to obtain permission to drive onto an internal road with a maximum load of 3.5 tonnes.

To minimise the drop in production caused by shading, the system works using Solar Edge power optimisers, where one optimiser is connected to two modules.

What are the effects?

Project Details

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