By Falk Antony

The substructures play an important role in solar systems. Carefully selecting and installing the substructure in a solar system can pay off in the long term. In addition to durability, assembly systems must meet several criteria: fitters expect flexibility in mounting the system as well as quick installation--and this for all types of system. By contrast, system operators are particularly interested in warranty periods, certifications, long-term viability and short payback periods, with the result that there is now also an international price war in the market for assembly systems. But not every system which is affordable and can produce certificates is a good choice.

Fit for Eeverything from the Detached Home to the Solar Farm

When selecting assembly systems, solar specialists particularly look for flexibility, simple installation and efficient storage. All-purpose systems which enable installation on flat and pitch roofs as well as open areas and facades are held in high regard. The substructure should be suitable for all roof claddings, from tiled and slate to metal sheet roofings, as well as for corrugated eternit and plastic roofs. The systems in demand are those which can be used with all internationally common module and collector types. These fundamental requirements were the basis on which the German solar system company mp-tec GmbH & Co. KG developed its in-house Quick-Line system. The result is a versatile assembly system which, in contrast to traditional systems, can also form the basis for solar carports and tracking systems. Thanks to its modular structure, the assembly system can be used in everything from the detached home to the large-scale project.

Check Warranties, Consider Country-Specific Certifications

As a rule, German manufacturers offer ten year warranties. By contrast, some companies such as mp-tec provide a 15-year warranty on all assembly components. This doesn’t just mean that the components of the assembly system will survive 15 years but that simple replacement of the modules is guaranteed, even after many years.

In addition to inspection by TUV Rheinland, the DEKRA certification is internationally recognizsed. On the other hand, some countries, like France and the United Kingdom, require specific national certifications. Certification to the DIN EN ISO 9001:2008 quality management standard is also widespread.

The Choice of Material Determines Service Life and Recycling

The system made of premium, weather-resistant aluminium and stainless steel is designed to withstand the force of the elements for several years. Many manufacturers use aluminium, but the important thing here is the degree of hardness and the alloying. For example, Quick-Line profiles are made of seawater-resistant aerospace aluminium, meaning that corrosion can seldom occur, even on installations in coastal areas. The use of low-grade materials can result in corrosion and even to screwed connections coming away. This can make the entire system unstable and cause it to collapse. In the light of rising prices of raw materials for aluminium and stainless steels, some manufacturers are also using other materials, but these cannot compete with aluminium and stainless steel in terms of service life, stability and resistance to corrosion. A further advantage: systems consisting of aluminium and stainless steel can be entirely recycled, representing an investment of value when they have reached the end of their service lives. This applies for inverters as well, having a high copper content.

The Price as Contributing Factor to System Profitability

It is not just the amount of investment for solar modules and inverters which are of importance in payback calculations for solar systems. In times of sharply falling module prices and ever larger solar farms, the item ‘mounting support’ assumes a role which should not be neglected. Manufacturers of assembly systems are accordingly also being affected by downward pressure on prices as cost for raw materials simultaneously increase. There are now a multitude of assembly system manufacturers around the world, which at first glance may all appear similar. In addition to the material and the flexibility of the system, crucial elements for a long service life are often details such as the alloying of the metal or minor components like the rivet, which in fact requires extensive technical expertise in development. The rivet permanently separates the metals physically. It is, therefore, the key to a sealed roof.

Residential

The visual impression plays a particularly large role in roof systems for non-commercial purposes. The roofs, which are typically very small, should be covered symmetrically. This is often complicated by dormers, chimneys and windows, in addition to roofs which themselves are asymmetrical. An assembly system with which the profiles can be positioned with millimeter precision using a cross connection is of help here. This is possible with Quick-Line, and subsequent adjustments are easy to carry out as the cross connection can be screwed and unscrewed at will. Systems like this are, therefore, particularly fault-tolerant with regard to asymmetrical roofs and fitters with little real-world installation experience. Assembly systems of this type are suitable for both unadorned roofs and winding surfaces, on which they considerably simplify precise positioning of the substructure and the modules.

Industry

Other aspects take priority in the choice of assembly systems for large-scale industrial roofs. Here, achieving large span widths and minimized loads are the key objectives. After all, a solar system, including modules, cables, the support and inverters represent a huge structural load. At the same time, there are also wind and snow loads, which vary in force from region to region. Reputable manufacturers have structural analyses performed on all components of their assembly systems to determine the maximum possible imposed load. The structural analysis of the roof is usually carried out by the tradesman. The result of this inspection determines the use of traditional roof penetration systems which promise a quick and durable installation or the use of zero-roof penetration systems which always require structural assessment by the manufacturer. These systems must be additionally loaded.

Customers often request zero-penetration and low-ballast systems due to frequent unjustified fears that the roof could be damaged by penetration and ultimately leak. As of now, there are systems on the market which enable zero-roof penetration installation at all tilt angles for both flat roofs and facade systems with the use of a triangular column.

In addition, some zero-roof penetration systems can be installed without gaps, which enables higher performance on the same surface area. Nevertheless, it is not guaranteed that the modules will remain in their original positions when exposed to the elements in the long term in all zero-roof penetration systems available. There are known cases in which the zero-roof penetration systems slipped and even collapsed. This may be prevented by so-called aerodynamic systems which, with their special design, direct the wind in such a way that it pushes the module firmly to the roof?no matter from which direction the wind is blowing. These systems are first subject to intensive wind tunnel testing.

Open Spaces

In bringing solar farms online, every day counts for system operators and investors. Every day on which the grid connection is delayed is a frustration, as no feed-in remuneration is paid for this time. The single-base system enables faster installation than traditional systems and can be used with all module types. It is, therefore, possible, for example, to install two rows of framed modules vertically, with laminate modules up to five rows horizontally are possible. An example of the use of the system was in the construction of a five megawatt solar farm in Eberswalde, Germany, only a few kilometres away from Berlin. mp-tec, which has also been doing project business for many years and is, therefore, highly familiar with the requirements of installers on assembly systems, constructed the park together with partners in under three months. Thanks to the quickly installable single base system, the time between planning and grid connection could be considerably reduced.

Trends for Assembly Systems

Comparable with the module market, a market for assembly systems will develop in the near future with its own market dynamic and in a state close to consolidation. Manufacturers which focus on low prices at the expense of high-quality material and the further development of assembly options will have difficulty holding their own in the market. Nevertheless, the subject of economic efficiency and, therefore, cost reduction is increasing in significance as the attainment of grid parity comes within reach. Assembly systems are increasingly attracting the attention of system operators and investors, whose interest lies in minimizing the system price per kWp in order to achieve favorable returns. Germany is here benefitting from its pioneering position in the solar market, as in addition to cell and module producers, numerous component manufacturers are based here, including many specializing in assembly systems. With their establishment on the home market, which not only provides one of the toughest climate tests (extreme heat and cold with snow, rain and hail as well as proximity to seawater in coastal regions) around the world as well as a particularly critical clientele, the assembly systems ‘Made in Germany’ will also be able to hold their own on a global scale. German consumers are well-known for their high quality awareness and the complex requirements they place on products. At the same time, German manufacturers must comply with particularly tough standards such as DIN 1055 and EN DIN 1991 (Eurocode 1) in developing their products.

Falk Antony has been a training leader at the mp-tec academy since 2010 (www.mp-tec.de). After many years working as a senior engineer at Solarpraxis AG in Berlin, the qualified engineer champions the official recognition of the solar trade, presents the topic of ‘installing solar systems’ in workshops and seminars and leads advanced courses on related topics such as the planning and marketing of solar systems.

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