X-panel

contents:
(1) – basic principles
(2) – ground mount applications
(3) – sloped roof applications
(4) – prototypes
(5) – production systems

(1) – basic principles

Tilting solar panels in their own plane greatly improves their self-cleaning properties and enables completely new array designs.

The X-panel is a patent pending way to arrange standard solar panels on inclined surfaces like large industrial roofs or the sloped tables of today’s ground mounted systems. The X-panel geometrical concept is built by rotating each panel in the same specified angle on its own plane. After this ration, the panels are then installed against one another to once again form a closed structure that covers the entire surface. There are a lot of execution variations with different angles and different clamping styles that all share the same principle. Some of them don’t even look like “X-panel” at first view. It is given the name X-panel because the “X” is the most slanting character in our alphabet.

MAIN CHARACTERISTICS

If the panel slope is too low, dirt will  accumulate along the lower frame rails.

Most of today’s solar panels are embedded in aluminum frames in order to give them more stability,  ease fitting, and protect them. This frame, however, triggers a significant problem when panels are installed at low slope angles (e.g. less than 20 degrees). The lower frame rail of the panel builds a horizontal raised rib at the lower edge of the module. This rib causes a back-water effect. The filthy water is not correctly run off resulting in the accumulation of dirt on the glass alongside the lower frame rail. This layer of dirt casts a shadow on the underlying cells, which can result in significant loss in yield of 30 percent and more per year.

Much better self-cleaning at lowest slope angles

A solar module installed in accordance with the X-panel design overcomes this problem in a simple, yet extremely effective way: By rotating the panel on its own plane, the horizontal corrugation disappears. The lower frame rails now both show slopes ensuring proper runoff of rainwater. The panel will remain clean, even at low slope angles with virtually all the same components that were used before: same panels, same rails, same clamps, so for a lot of applications there are even no additional cost.

MAIN APPLICATIONS

The X-panel is a simple, yet very effective solution for low slope angle installations.

The X-panel shows its advantages when standard aluminum-framed solar panels have be installed at low slope angles. The main applications are ground mounted systems where high ground coverage ratios are required, as well as, systems for tilted industrial roofs where the low pitch of the roof does not allow an istallation parallel to the roofing.

(2) – ground mount applications

Better ground coverage

500+ KWP/ACRE WITH south facing panels

Today’s mix of fix cost and variable cost for large ground mounted solar installation calls for a maximum ground coverage in order to reduce the electricity generation cost (see also “Thoughts on future solar plants”). This is particularly true for densely populated regions, where labor cost are high and land is expensive. In order to line the panel rows up closely together, however, the slope angle of the solar panels must be reduced. Otherwise shading effects between the rows will kill too much energy yield. On the other hand, with a flat installation, you may face serious soiling problems due to dirt that accumulates alongside the lower panel frame rail. There’s no common sense yet about the minimum acceptable slope angle. However, leading project developers like ENERPARC and BayWa re see the geometrical limits at 20 degrees if the panels are installed the usual (e.g. landscape or portrait) way.

Given the same shadow limit angle (here 18.4°), the difference in ground coverage is significant between (top down) standard 32°, standard 20° and 8° X-panel rows.

The simple yet very effective X-panel module arrangement exceeds this limit. Latest designs show possible slope angles of 8 degrees or less without any additional soiling. This allows for ground coverage ratios of 0.8 and above which is good for more than 500 kWp per acre (1.3 MWp per hektar) with standard solar panels.  The modules are still south-facing which guarantees a good annual yield, while the high density of panels assures low system prices per kWp.

Tried and true components

Same components, same moves, same rapidity: Installing solar panels the X-panel way is business as usual.

A charming facet of the X-panel technology is the fact that you can use common components to mount solar modules the X-panel way – the same rails, same clamps, same screws. They are all the same parts that have been used before -they’re only bolted together in a slightly different way. This eliminates the need to develop new parts, and no need for the installer to adapt to new mounting technologies. In fact, the first couple of X-Panel rows that have been installed in the UK already showed that it’s business as usual. Installation is as quick and as easy as it was before.

(3) – sloped roof applications

slightly pitched roofs

Low slope angles will inevitably cause dirt accumulations and, therefore, production losses.

When it comes to choosing a pv system for slightly pitched industrial roofs, the first approach is always to install the solar panels parallel to the roof. This keeps the price of the racking system low and the installation fast and easy. Moreover, since the panels are all on the same plane, there are no shadow effects allowing for a dense panel arrangement and thus a high energy yield per square feet. An useful roof pitch would be 20 degrees or more. However, the majority of today’s industrial roofs show much lower slopes causing serious production problems resulting from soiling.

With X-panel, the cleaning effect is visible after only a couple of days.

For these roofs there are alternatives on the market, each of which have their own shortcomings. There are, for example, racking systems that raise the module slopes to ensure proper self-cleaning. At the same time, however, they imply self-shading effects that reduce annual yield. They create higher wind loads, as well as, higher costs. Switching to frameless panels, particularly to thin film modules, reduces the overall efficiency of the system and again raises installation cost. There are even solar panels on the market, in which the lower frame rails are notched or grooved to aid in water run-off. Each of these approaches entail higher costs and provide a limited solution to the soiling problem.

X-panel: ALL THE PROS WITHOUT THE CONS

There are a couple of different X-panel module arrangements that ensure the self-cleaning effect.

Installing the solar panels the X-panel way, rotated in their own plane, is a solution involving striking simplicity. It assures that the panels stay clean because the water is effectively drained at the lowest corner of the panel. No more soiling at low slope angles. This makes it possible to install the panels parallel to the rooftop, assuring solid, dense, and streamlined solar systems. Installation is fast and easy, while racking cost are kept low. Furthermore, just as in ground mount installations, sloped roof systems of the X-panel use all common components only bolted together in a slightly different way. In fact, there are a lot of different X-panel arrangements that produce this self-cleaning effect. Some of them are obvious, others are not. Also, there are a number of clamping variations, each of which has it’s own advantages (our patent application contains a total of 18 drawings). More an d more experts believe that this new mounting technique might actually change the appearance of solar farms and rooftop systems over the long term.

(4) – prototypes

Off-the-shelf hardware

The look underneath an X-panel installation shows the same mounting structure that is used for standard ground mount installations

When we developed the idea of rotating the solar panels on their own plane we quickly realized that there was no need to develop additional mounting parts. Although this sounded too good to be true, our first ground mounted prototypes quickly proved the correctness of this assumption. This allowed us to build the first two prototypes within a couple of days using only off-the-shelf components. These prototypes were built together with a leading European racking manufacturer who now holds a license for ground mounted X-panel mounting systems.

fast and easy installation

Field tests proved that X-panel installation is as easy and fast for standard panel arrangements.

A few weeks after the construction of the first prototypes, several project developers started field tests by installing X-panel rows within projects they were constructing at that time. The main goal here was to verify the practical usability of the X-panel technology, while focusing on installation time. The feedback we received was unanimous: The installation is very similar to  standard procedures. There is, therefore, no need for a particular training nor for any special installation guides, and the mounting times were the same as they are in landscape oriented panel rows. In fact, they were so enthusiastic that they changed several projects they had been working on from standard orientation to X-panel arrangement. Consequently, the first megawatt-scale X-panel fields was built within the first quarter of 2016, followed by a second one by the end of the year.

less dirt, less snow

Pleasant side effect: The X-panel help the snow coat to slip faster off the panels thus providing an earlier restart of energy production.

From the beginning, there was little doubt that the rotation of framed solar panels will be very useful in reducing soiling effects. Another prototype was built directly next to a mounting structure with the same slope angle and portrait oriented modules. The effectiveness of the X-panel became evident after only a couple of days. The standard panels showed visible dirt accumulations alongside the lower frame rails while the X-panels did not. After the first snowfall, another very pleasant side effect became obvious: The X-panels not only assist water runoff, they also seem to aid the snow coat in sliding off the panels faster. The difference was clearly visible and, indeed, the X-panels became free of snow well before the standard modules.

(5) – production systems

A first utility-scale solar project has been constructed in Southern Germany. The “Hüttberg” plant is located directly at the Autobahn A3, exit Parsberg, and has a total size of seven Megawatt peak. The panels are mounted in X45-style. The second large X-panel project has been built-up in Yorkshire, UK. It features five Megawatt peak and X10-style panel arrangement. Other projects are under development.

“Hüttberg” is the first utility-scale installation using the X-panel technology for maximum ground coverage. Picture: ENERPARC AG.

For the X-panel solar plant in Sandhutton, Yorkshire, UK, project developer BayWa re opted for a slightly lower rotation angle of the solar modules.