Earlier this month, at a joint conference of two solar technology industry groups, the topic of solar panel size came up. Dennis She, SVP of LONGi Solar, gave an interesting presentation on the ups and downs of larger solar panels, concluding that bigger sizes aren’t always better. The webpage describing his presentation was thin on details, but we were able to fill in the gaps with our cleantech and construction industry knowledge, and help explain it to readers. It also gives us some insight into possible industry benefits of Tesla’s Solar Roof.
“For large scale PV power stations, increasing the power of PV modules by increasing the wafer area is, to a certain extent, beneficial to the reduction of BOS costs and LCOE,” Mr. She said. “That said, the size of the module is not a question of bigger being better. It is necessary to consider in depth the boundary conditions of manufacturing costs, transportation, reliability and manual installation.”
In plain English, he was explaining that larger panels (which produce higher wattages) can have economic advantages in production, as the cost per watt would in theory go down. Steps that only need to happen once per panel would happen less often, and economies of scale would be beneficial. However, manufacturing in a factory does not exist in a vacuum.
There are several reasons elsewhere in the supply chain that that bigger panels can end up costing more per watt by the time all is said and done.
First, standard intermodal shipping containers just aren’t going to work well with bigger panels. The door height of a standard 40 foot high cube shipping container limits cell size to about 1.13 meters (about 3 foot 8 inches). Trying to make bigger panels would mean that shipping costs would go way up, and could potentially end up canceling out any savings from manufacturing bigger panels.
Second, glass production is an issue. According to She, glass factories don’t make panels of glass wide enough for the larger 600 watt panels some manufacturers would like to make. So, if you wanted to actually build them in any volume, you’d have to cover the costs of retooling whole glass manufacturing plants (along with anything else that may have to change in their supply chains), making for more expensive panels. Once again, that supply chain disadvantage could wipe out the savings of larger modules.
Installation is another concern. Solar installation companies are used to installing panels of the size that they already install today. Assuming the last two issues were somehow solved (a tall order), now you have to get the local installers to change what they’re doing. Not only do they need different bracketing setups, but presumably they’d lose flexibility in how many panels could fit on all the differently shaped roofs that exist out there. Also, transporting the cells to the installation site could also be more challenging, with some installers needing different trucks and/or trailers.
Finally, Mr. She shared that larger cells for the larger panels end up being less efficient at producing electricity, which compounds all of the above problems.
Nearly every one of these issues shows just how smart Tesla has been with its Solar Roof design. Smaller panels (the size of a shingle) give a lot more flexibility throughout the whole supply chain. They’re probably a lot easier to transport, don’t require large panes of glass, and can be installed for maximum output on any roof shape. Smaller panels may also be more electrically efficient, with lower resistance.
All of this may come together to keep the cost of solar going down into the future, something Tesla has already prove quite adept at, as Elon Musk explained to CleanTechnica in September.
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