Green roofs: combining photovoltaics and horticulture

At first glance, the combination of green roofs and photovoltaic systems may seem a bit crazy to many. However, a closer look reveals that this connection is quite rational for several reasons.

Introduction to Green Roofs and Photovoltaics

The reasons for both photovoltaic systems and green roofs independently serve the same goal: making life more comfortable and livable for the residents of a building in different ways and with various impacts.

First, regarding the photovoltaic system. The development and fluctuations in electricity prices over the past years, including those caused by unforeseen events, have been financially challenging for many. To become more independent from the public power grid, a photovoltaic system is a viable option for both tenants and property owners. The tenant is explicitly mentioned because the legislature has created frameworks that particularly highlight tenants. Until recently, tenants were very dependent on the landlord's decision on whether a solar system could be operated or not. However, tenants can now decide for themselves on a smaller scale, such as with a balcony power station or a micro solar system. While the landlord still has a say in how the installation is done, they generally can no longer refuse such an installation. This measure is also undoubtedly influenced by the ambitious goals of the federal government regarding the energy transition. Operating a PV system reduces public grid electricity consumption and makes the operator more robust against price fluctuations and increases.

Green roofing is part of a measure to combat climate change. On the one hand, the greenery helps capture CO2, and on the other hand, it lowers the ambient temperature and provides insulation to buildings. As peak temperatures will continue to rise in the coming years and decades, this will improve the microclimate in cities and rural areas alike. Green roofs also provide better insulation in winter, thus reducing energy costs.

Benefits of Combining Photovoltaics with Horticulture

The combination of horticulture or green roofs and solar technology has the advantage that the solar panels are less dusty, thus reducing maintenance efforts. As previously described, greenery reduces the temperature, which benefits a solar system in a particular way. While it is true that solar systems need sunlight to generate electricity, their efficiency decreases at high temperatures. For this reason, green roof photovoltaics are particularly efficient, and the roof greening ensures higher energy yields, thus increasing the profitability of the solar system and accordingly shortening the payback period.

Planning and Design of Green Roofs with Solar Modules

There are several considerations when planning green solar roofs. First and foremost, ensure that the solar system is oriented as efficiently as possible. When planning the green roofing, the selection of plants is significant, as not all plants are suitable in combination with a PV system. Extensive information on this is provided by the German Green Roof Association. Here one can learn all about the basics and get specific planning recommendations. Meanwhile, experts such as architects, landscape planners, or solar experts can also support in the planning process.

Maintenance and Care of Combined Green Solar Roofs

It is advisable to carry out maintenance work on the solar system simultaneously while caring for the green area. The effort is minimal and ensures that everything functions flawlessly. The care of green solar roofs is oriented towards the care needs of the different plants and the environmental influences to which the solar system is exposed. Regular inspections of the condition of the panels and cables, as well as the connectors, are usually sufficient. If there are uncertainties, it is wise to call in experts to ensure that the system is functioning correctly.

Case Studies: Successful Examples of Green Solar Roofs

The city of Freiburg has developed a comprehensive concept for the dissemination of solar energy and solar systems in conjunction with greenery. Numerous successful examples from the city show that the combination makes sense. This is made possible by the funding program "Building Green High3" and "Your Roof Can Do More". Besides this example, there are countless others across the Republic showing that green solar roofs are not only sensible but also function in everyday life and that theoretical approaches have already proven themselves in practice.