PV and shadows on your roof? SENS casts light on the situation!
Maximum photovoltaic yield despite shading on industrial roofs and branches
The sun is shining, not a cloud clouds clouds the sky, the roof is optimally aligned - the best conditions for your photovoltaic system. But how profitably does the electricity from the power of the sun flow when trees or tall buildings cast their shadows on solar modules? How does partial shading of antennas, chimneys and ventilators on the roof influence the economic efficiency of a PV system? SENS raises the potential of shaded rooftop PV systems for industry, trade and commerce - with shading analyses, yield simulations and precise planning. So that you benefit from the maximum energy yield of your solar system.
Only very few roofs are completely shadow-free.
Unobstructed roof surfaces without shadows in combination with strong solar radiation guarantee high yields and highly efficient photovoltaic systems. “However, as our many years of experience of performing shadow analyses and working on industrial roofs with rooftop features have shown us: very few roofs are completely shadow-free,” says SENS planning engineer Sascha Link.
Shadows can be caused by:
- Rooflights/smoke and heat extraction equipment (SHE)
- Ventilation fans
- Air-conditioning equipment
- Roof-access anchor points
- Parapet walls or edge railings
- Nearby trees
- High buildings/masts
- External lightning protection with tall lightning conductors
Clever simulation – PV yield over a year despite shading
To ensure you obtain the maximum energy yield, SENS experts carry out a professional survey as the first step in a shadow analysis: they record roof dimensions, the positions and sizes of interfering objects and produce a photographic record – in certain cases augmented by an automated 3D drone building survey.
Using the powerful simulation software PVsyst, a detailed yield simulation based on the knowledge gained from the survey then shows the effects of shadows on yield over the course of a year. Different shadows are cast depending on the seasonal position of the sun: the winter sun sits low in the sky – at this time of year, even small hills or buildings in the neighbourhood can cast shadows that might well go unnoticed in summer.
Keep proximity shading objects at a distance – avoid hot spots and overheating
The further away the shading object is from the module surface, the lower the resulting losses. Therefore, it is particularly important to avoid proximity shading caused by thin, nearby objects, or ensure such objects are at a suitable distance. They cast sharp shadows with “hard” dark cores in direct sunlight.
If solar cells in a photovoltaic module are in shade, this affects all the other solar modules in the string connected in series to it: the electricity produced by the upstream modules cannot go any further. If a module in a string is in shadow, the total output of the string is reduced.
In addition, local overheating – known as hotspots – can occur. This is because the affected cells can accept only limited current and become very hot due to the current produced by the other solar cells. Hotspots cause long-term damage to solar modules and may start fires, but they can be identified using a thermal imaging camera.
Bypass diodes, inverters, power optimisers: yield loss reduced, performance maximised
Three bypass diodes are built into each module to reduce the effect of partial shade, which might otherwise affect the whole string of modules. These bypasses divert the current around the shaded cells, thus avoiding reverse currents at the affected areas of a module.
Using highly efficient PV inverters, partially or fully shaded modules can achieve their optimum performance, while power optimisers in such a system can raise the efficiency of the PV installation: individual module optimisers have built-in buck-boost converters with a 750 V fixed voltage control. They optimise the solar yield, particularly if the solar modules are affected by proximity shading, dirt or ageing effects. If they are installed on every solar module, then only the performance of the affected module drops and not that of the complete inverter. “By adopting these measures and planning the project properly, we minimise yield losses and obtain the maximum performance from the modules,” says Sascha Link.
Cheap electricity – secured for 20 years or longer
For many years, SENS has designed and built successful PV rooftop systems, for example, on store roofs of large retail food chains all over Europe. Once your system is in place, you have a low-cost electricity supply, secured for 20 years or longer at predictable fixed costs. In many cases, a PV system can cover the whole of your premises’ own consumption. You can temporarily store any surplus electricity produced in a supplementary energy storage solution. This means you always have energy available, are sheltered from rising electricity prices and independent of your energy supplier.
What can I do if shading is unavoidable?
Some objects that cast shadows, such as roof-top features or nearby trees, cannot always be avoided on every roof. Our SENS experts calculate what effect the shade has on the total solar yield of the PV system and advise the customer of possible solutions (e.g. adjusting the distance to the shading object or the configuration of the inverters). If the shading is only caused by the low sun in winter or in the early morning or late evening, then this will have very little effect on the total solar yield of the PV system. Simulations can model and assess this type of scenario. Do you have objects on your roof that cast shadows? Are you unsure whether your roof is suitable for a PV rooftop system?
We maximise your potential!
We maximise the potential of solar power and set your roof in the most favourable light – and can do so in your region. We complete the planning and installation of your PV rooftop system to suit your individual requirements.