Steel structure PV
Steel structures in PV projects.
Interview with Damian Ołdziejewski,
Member of the Management Board, Head of Consulting at P&Q
What is the essence of designing photovoltaic farms?
The essence of the design process is finding a compromise between the economic and technical aspects of the investment. Finding a balance between investor expectations, budget, availability of equipment and the requirements of O&M services. Although the design stage is only one of the elements in the life cycle of the RES facility, in which all participants of the construction process take part, the general designer of the project has a very responsible task, which must align with the interests of all parties.
What are steel structures used for on PV farms? What types are there? What are they made of?
Steel structures are used for the installation of photovoltaic panels, subject to the need to maintain their trouble-free operation, which is achieved by ensuring the stability of PV panel assembly and meeting all load bearing limits.
Steel structures can be divided into fixed and variable-position structures, commonly called “fixed” and “tracker” systems, respectively. Fixed structures are the most commonly used in Poland on large-scale farms, as well as on 1 MWp farms, which had dominated the industry for many years. However, more and more investors decide to use tracker systems, which increase the efficiency of the photovoltaic farm. No matter if the structure is fixed or variable-position, its going to be made of thousands of kilograms of steel, in many types and forms, protected by the so-called Magnelis coating or zinc coating . The choice of coating depends on the investor’s requirements, the expected lifetime of the photovoltaic farm and, of course soil conditions.
What is the absolute thing to bear in mind when designing the structures?
When designing steel structures, it is essential to pay close attention to the terrain conditions, the location of the facility in the appropriate wind and snow zone and the requirements of the manufacturer of photovoltaic panels as to the method of installation, support or even earthing.
One of the first stages of the project is the right choice of support leg length, which must be verified by pull out tests, confirming correct selection of the depth of piling, by physically verifying the forces necessary to pull, buckling or crushing the leg of the photovoltaic structure. However, the most important element is the calculation of the load limits of steel structures, which can be based on a methodology directly from Eurocode or by conducting tests of wind pressure distribution and wind lift-up affecting steel structures, commonly referred to as “windtunnel”. The above tests are costly, but allow for accurate mapping of the real-life conditions of contact and wind pick-up for a given type of steel structure, which significantly increases the safety of the installation.
What materials are most commonly used?
As I said before, basically it is anti-corrosion protected steel. In recent years, alternative technologies have appeared (e.g. concrete structure legs), but so far they have not won the market by storm.
Is there a broad market of structure suppliers? Are there any major suppliers in Poland?
In Poland, the market of suppliers is constantly growing. Today, it is mainly made up of local companies, but more and more foreign companies tempted by large-scale projects decide to introduce their product to our market. In my opinion, so far, Polish companies are defending successfully and offer products that can compete economically and technically with foreign producers.
Are panel suppliers supportive or rather bothersome?
Panel supplier, like any participant in the design stage, provides its contribution to the whole project. Since the panels are, for the time being, actually 100% imported from China, with no denying that there are frequent issues with communication.
It is very important for the designer of the structure to adapt to the installation instructions provided by the manufacturer of the panels. There is no problem as long as the instructions are detailed and clear, but it is often the case that provided guidelines are either very imprecise or even undergo significant changes during the design process (and sometimes even after the start of construction process). In some cases, we need additional explanations, tests or confirmation of the compatibility of the applied solutions of a dedicated steel structure with the module used and this can be seen as the most difficult part of cooperation with the module manufacturer, because the exchange of information usually takes weeks.
Do all panel suppliers work the same way or are there “better” and “worse” ones?
It is much easier to cooperate with suppliers of photovoltaic modules who are not members of a larger capital group that also produces steel structures.
What are the most common mistakes?
The most common mistake is not to adjust the design to the shape and elevation of the terrain, which makes it necessary to use additional components or adapt already made elements of the structure. More widely, we can also notice incorrect distances from forests or technical infrastructure; such errors, however, are usually made at the development stage and during the implementation phase it is difficult to fix it.
What is the biggest error you ever made?
To me, an error in a project is something that cannot be fixed without incurring significant costs. This has not happened to me yet.
How much time is spent on solution optimization? Is it always safe for the project?
Optimization is the most important element of the design process and requires 90% of the necessary time to complete the project. Without optimizing solutions, the photovoltaic industry would not develop, which would lead to stagnation. The optimizations we make are always safe for the project, otherwise they would be a threat and then we would have to call it by name: malpractice.
How many RES projects did you participate in and in what capacity?
It would take a lot of space to list all my projects, but if expressed in MW, I managed to design about 0.5GWp of photovoltaic farms and supervised the execution of about 200MW as a member of the executive team.
What is the most important success factor in the photovoltaic industry?
Quality, innovation and experience. Three conditions necessary for success.