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Same old reliability lessons from amazing new (solar cell) technologies

There are plenty of reasons for renewable energy to become increasingly important. These reasons start with climate change and end with our unmistakably finite amount of fossil fuels buried in our fragile planet. One of the early criticisms of renewable energy was that it wasn’t cheap. Sure - the energy sources such as sunlight, wind and flowing water are inherently renewable, but the costs to manufacture and maintain all the equipment that extracts energy from these resources can be very high.

Not any more. The cost to generate a single megawatt-hour of electricity using solar or ‘photovoltaic (PV)’ cells was $ USD 359 in 2009. This was easily the most expensive electricity generating resource. In 2019, that cost dropped to $ 40 per megawatt-hour. Which is now the least expensive electricity generating resource (edging out onshore wind at $41 and combined cycle gas at $ 56).

So why is the cost reducing so much? Well, part of it is because the price of solar modules has declined by more than 99 % since the late 1970s. This is largely due to the wonderful benefits of mass production. The more we produce, the more we learn from mistakes. The more is invested in cool manufacturing technologies. The more we can streamline processes. The more … et cetera. But even this impressive reduction in costs can’t explain the drop in electricity generation costs. At least not by itself.

What about efficiency? And by efficiency we mean how much electricity our solar cells generate for a specific amount of energy provided by the sun. Well, efficiency has been steadily improving over the years too. Efficiency has more than doubled from around 12 % in the mid-1970s to around 28 % as of today. Of course there are lots of different technologies that are used to make lots of different types of solar cells (with the highest efficiency being around 47 %). But even this improvement in efficiency can’t explain the reduction in overall electricity costs.

So here comes reliability.

The main cost driver that is left revolves around how much it costs to maintain and manage our solar cells. And that has a lot to do with reliability. The crystalline structures that make up the solar cells degrade over time. They slowly delaminate, or the glass anti-reflective coating wears away. And finally, the corrosion of the cell and its interconnect spells the ultimate doom of solar cells.

Reliability has a lot to do with this. So … what is the same old lesson we need to learn? Well, it comes from a fairly recent realization about why solar cells are likely to fail.

Perhaps the most significant cause of solar cell failures across all solar cell manufacturers and products is … junction box failure!

PV Evolution Labs releases annual scorecards based on extensive testing it conducts on all manners of solar cell technologies from all manners of manufacturers. And it looks like junction box failures are on the increase. Junction boxes are (supposed to be) weatherproof containers that house the important bits where electric cables connect to other cables or important components. They aren’t even on the main solar panels. And things like junction box moisture ingress are key drivers of failure.

This really shouldn’t happen. Junction boxes are used in lots of applications in lots of industries. We know how to do them.

Think of all the wonderful technology and manufacturing care that goes into creating wonderfully efficient and increasingly cost-effective solar cells, only for one of the ‘simplest’ elements of the system to be its weak point. And beyond the basic costs incurred for repair, replacement and lost electricity, there has been lawsuit after recall after bankruptcy … all because of something as simple as a junction box.

So what is the same old reliability lesson?

The VITAL FEW things that drive the performance of your system are not the sexiest, your favorite, the most complex or the easiest things.

Even in emerging technologies, the bits that haven’t changed for decades might be the weak points. Which is an awesome thing! Because instead of investing money in improving the reliability of an expensive new technology … all you might have to do is get your junction boxes right.


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