Should you wash your solar panels?
Should you wash your solar panels?
你应该清洗太阳能电池板吗？
I have a small solar farm and the panels have got visibly dusty. Is cleaning them worthwhile? How much difference does it make? Let’s find out. I know that my panels have not been cleaned in the last year. I expect they also weren’t cleaned in the year prior to that (why would you clean them when you’re about to sell the house?). But beyond that I don’t know when they were last cleaned. 我有一个小型太阳能电站，电池板上已经明显积灰了。清洗它们值得吗？会有多大差别？让我们一探究竟。我知道我的电池板在过去一年里没有清洗过。我估计前一年也没洗过（毕竟都要卖房了，谁还会去洗呢？）。但除此之外，我也不知道它们最后一次清洗是什么时候。
Summary
总结
The short answer is that I think I got a 2%-5% increase in power output from my solar farm due to cleaning the panels, which will work out to about £60-£150/yr, decaying to 0 over the course of a few years. So, probably just about worthwhile. 简短的回答是，我认为清洗电池板后，我的太阳能电站发电量增加了 2%-5%，折合每年约 60-150 英镑，且这种增益会在几年内逐渐衰减至零。所以，这大概是值得的。
Methodology
方法论
There are 16 panels in total, connected up to the inverter as 2 banks of 8 panels each. The inverter reports the power output from each bank individually, so the plan is to take a bunch of readings before starting, then wash all of the panels in one bank, taking readings in between and at the end. Our hypothesis is that cleaning the panels will increase power output. We can test whether washing the panels has made any difference by looking at the ratio of power output from the 2 banks. If we just looked at raw power output then it would be confounded by changing cloud cover, sun angle, etc. There is still the fact that the 2 banks of panels are physically separate and plausibly one bank is better positioned for sun 45 minutes later than the other. Ideally I would have been measuring the ratio of power output for several days prior to see how it varies throughout the day. 总共有 16 块电池板，连接到逆变器上，分为两组，每组 8 块。逆变器会分别报告每组的功率输出，因此我的计划是在开始前记录多组读数，然后清洗其中一组的所有电池板，并在清洗过程中及结束后记录读数。我们的假设是清洗电池板会增加发电量。我们可以通过观察两组电池板的功率输出比率来测试清洗是否产生了影响。如果我们只看原始功率输出，就会受到云层变化、太阳角度等因素的干扰。此外，这两组电池板在物理位置上是分开的，其中一组可能比另一组在 45 分钟后的光照位置更好。理想情况下，我应该提前几天测量功率输出比率，以观察其全天的变化情况。
This is how the first row of panels looks after I’ve washed 3 of them, you can see the furthest one is noticeably grubbier: So they were “visibly dusty”, but not massively dirty. If your panels are dirtier than mine were, then your benefit from cleaning them will be greater than mine was. 这是我清洗了第一排中的 3 块电池板后的样子，你可以看到最远的那块明显更脏：所以它们只是“肉眼可见的积灰”，并没有非常脏。如果你的电池板比我的更脏，那么你清洗后获得的收益会比我更大。
Results
结果
My results for cleaning one bank of panels are shown in this chart: We see that the initial power ratio is very stable before the panels are washed. We then step up to having washed “half” a panel (I initially tried to wash them with window cleaner and a paper towel, but this was ineffective so I then walked away to get a bucket of soapy water and a cloth, and then took a reading which I labelled as 50% washed). For some reason the power ratio drops significantly when the first panel is washed, I’m unsure why. And then the power ratio increases as more panels are washed as we’d expect. But once all the panels are washed, the power ratio drops off again while nothing changes. I am unsure whether this is because as the surface water evaporates off the panels get slightly opaque again? Like the “frosted glass effect”, where you can see through frosted glass when it is wet but it gets opaque again when dry. Maybe beyond cleaning the panels I ought to be polishing them? Anyway it looks like cleaning the panels was about a 2%-5% improvement, depending on what you think is going on at the end. 我清洗一组电池板的结果如图所示：我们可以看到在清洗前，初始功率比率非常稳定。随后我们进入清洗“一半”电池板的阶段（我最初尝试用玻璃清洁剂和纸巾清洗，但效果不佳，于是我拿了一桶肥皂水和抹布，并记录了一个我标记为“清洗 50%”的读数）。出于某种原因，当第一块电池板被清洗时，功率比率显著下降，我不确定原因。随后，随着更多电池板被清洗，功率比率如预期般上升。但当所有电池板都清洗完毕后，功率比率再次下降，尽管此时没有任何操作。我不确定这是不是因为表面水分蒸发后，电池板又变得稍微不透明了？就像“磨砂玻璃效应”，磨砂玻璃在湿的时候能看透，但干了之后又会变模糊。也许除了清洗，我还应该抛光它们？总之，清洗电池板大约带来了 2%-5% 的提升，具体取决于你如何解读最后阶段的变化。
Tingle
麻电感
I got a bit of a tingle when I was cleaning one of the panels. At first I thought I was getting an electric shock from the wet panel, but I inspected my finger and found a tiny thistle splinter in it. After I removed the splinter it seemed fine. But a bit later I got another tingle from another panel! There definitely wasn’t a splinter in my finger any more, but the tingle was in the same place. I think the tingle actually was coming from the electricity, but I was only able to feel it at the point where the thistle had already pierced the skin. ChatGPT convinced me that there could just be a tiny “capacitive leakage” from an “inverter with no transformer”, so I’m not going to worry about it. But if I clean the panels again I will wait until dark lol. 在清洗其中一块电池板时，我感到了一点麻电感。起初我以为是湿电池板漏电，但我检查手指后发现里面有一根细小的蓟刺。拔掉刺后感觉好多了。但过了一会儿，我在另一块电池板上又有了这种感觉！我的手指里肯定没有刺了，但麻电感还在同一个位置。我认为这种感觉确实来自电流，只是我只有在蓟刺刺破皮肤的地方才能感觉到。ChatGPT 说服了我，这可能只是“无变压器逆变器”产生的微小“电容性漏电”，所以我并不担心。但如果我再清洗电池板，我会等到天黑后再做，哈哈。
Upgrading
升级
The next question is should I be upgrading the solar farm? I think mine was installed about 15 years ago, and generates (at peak output) 3.7 kW from 16 panels. Correct me if I’m wrong on any of this: Replacing the panels with more modern ones would increase the power output by about 60%, at a cost of about £5000, which would pay for itself in about 3 years, which seems like a no-brainer. However, due to the fact that my solar farm was installed so long ago, it benefits from a feed-in tariff, which means that not only do I get paid an absurdly high rate, but it is paid also based on the electricity I generate rather than what I export. If I increase the power output of the system then the additional capacity will not be eligible for the feed-in tariff and will revert to present-day prevailing tariff which is about 4x worse before you even consider that I currently get to use electricity and still get paid for generating it. This is the yin and yang of market-distorting incentives. Today’s incentive to install solar becomes tomorrow’s disincentive to upgrading it. 下一个问题是，我应该升级我的太阳能电站吗？我想我的电站大约是 15 年前安装的，16 块电池板（峰值输出）可产生 3.7 kW 的电力。如果我说错了请指正：更换更现代的电池板将使发电量增加约 60%，成本约为 5000 英镑，大约 3 年就能回本，这看起来是个显而易见的选择。然而，由于我的太阳能电站安装时间太久，它享受“上网电价补贴”（feed-in tariff），这意味着我不仅能获得极高的费率，而且补贴是基于我产生的电量，而不是我出口的电量。如果我增加了系统的发电量，额外的容量将无法享受上网电价补贴，而会退回到当今的现行费率，这比现在的费率差了约 4 倍，更不用说我现在既能用电又能因发电而获得报酬了。这就是市场扭曲激励机制的阴阳两面。今天安装太阳能的激励措施，变成了明天升级它的阻碍。