{"id":6172,"date":"2016-07-15T13:36:04","date_gmt":"2016-07-15T04:06:04","guid":{"rendered":"http:\/\/www.solarquotes.com.au\/blog\/?p=6172"},"modified":"2021-04-06T23:25:41","modified_gmt":"2021-04-06T12:55:41","slug":"an-eastwest-spit-of-solar-panels-on-a-single-string-can-work-well","status":"publish","type":"post","link":"https:\/\/www.solarquotes.com.au\/blog\/an-eastwest-spit-of-solar-panels-on-a-single-string-can-work-well\/","title":{"rendered":"East West Facing Solar Panels On A Single Inverter Input Can Work Well"},"content":{"rendered":"
\"east

Is it OK to put East and West facing panels on a single input inverter?<\/p><\/div>\n

<\/p>\n

Most Australian solar installations use string inverters<\/a> where solar panels are connected in series with\u00a0an electrical cable. Each group of panels in series is called a string<\/a>. Each string is connected into a separate input on the inverter.<\/p>\n

\"diagram

1 string per inverter input<\/p><\/div>\n

In the\u00a0configuration above, each string can have a different numbers of panels and each string can face different directions. You could even have a different type\u00a0of panel for\u00a0each string. This is because each inverter input is connected to a separate\u00a0Maximum Power Point Tracker<\/a>\u00a0(MPPT). The MPPTs optimise each input separately.<\/p>\n

Sometimes\u00a0multiple strings are connected in parallel, into one inverter input. To do this each string must have the same number of panels and they must be identical brands and models.<\/p>\n

\"strings

Multiple strings can be connected into one inverter input. The strings must be identical in terms of numbers of panels and model type.<\/p><\/div>\n

Generally speaking all the panels in the configuration above\u00a0need to be facing the same direction, or the MPPT struggles to optimise the array efficiently.<\/p>\n

If an east\/west split of solar panels is desired, where some panels are facing east and some facing west<\/a>, then normally those panels would be placed on separate strings and a two-input inverter would be used.<\/p>\n

However, under the right circumstances, it is possible to have an east\/west split of solar panels on a single inverter\u00a0input, like the diagram above (imagine\u00a0the left-hand 3 panels facing west and the right-hand 3 panels facing east)\u00a0and still have almost the same performance as if they were on separate strings attached to two separate inverter inputs.<\/p>\n

Update:<\/strong> With careful design and a good inverter such as SMA\/Fronius it is also possible to have a North & East split or a North & West split on a single MPPT.<\/em><\/p>\n

Why would you want to do this? Well, a single string inverter may be cheaper than a two-input inverter, or you may want to save the second input for a north-facing array.<\/p>\n

As well as houses\u00a0with directly east and west-facing\u00a0roofs, this could also\u00a0be done on any building with a flat roof by using racking, including large commercial installations.<\/p>\n

I Didn’t Believe It Myself At First<\/h2>\n

When I was told it was possible to put both east and west-facing panels on the same inverter input\u00a0without a serious decline in performance, I was sceptical. I was all, \u201cNah! That’ll never work! When the sun isn’t directly overhead the two sets of panels will receive different amounts of light and, since they’re on the same input, the mismatch will cripple the MPPT’s optimisation and\u00a0pull down the performance of the others. It’s not a good combination. Putting east and west-facing panels on a single input\u00a0is like putting chalk and cheese together in a sandwich and hoping the contrast of flavours will result in a taste sensation.\u201d<\/p>\n

But I looked it up and it turned out to actually be correct, but only under the right circumstances.<\/p>\n

Dietmar Is The Dude With The Dirt On Single String\u00a0Shenanigans<\/h2>\n

When it comes to getting the low down on east\/west splitting on a single inverter input, Dietmar Staudacher is the man to turn to. Or at least I assume he is a man. Very few women are called Dietmar. But I’m sure those women who are called that are quite impressive.<\/p>\n

Dietmar wrote, Ost\/West-Ausgerichtete PV-Anlagen Mit Nur Einem MPP-Tracker<\/em>, and you can read a PDF of that paper in its original German here<\/a>.<\/p>\n

Fortunately, I am extremely talented at reading German… after it has been translated into English. And you can read a translated PDF by clicking on its English title, Efficient East-West Orientated PV Systems With One MPP Tracker<\/a>.<\/p>\n

Now note that Deitmar’s paper was published 7 years ago, which is like 7 years in solar years. There have been a lot of developments since then. But his basic conclusions are still sound.<\/p>\n

The Benefits Of An East\/West Split<\/h2>\n

Several years ago when high solar feed-in tariffs were still available, the best direction to face panels was north, so they’d generate the most electricity and allow the most feed-in tariff to be earned. But with high feed-in-tariffs, a thing of the past, except in the Northern Territory and parts of Western Australia, self-consumption of solar-generated electricity has become more important, and an east-west split of panels can help with this as it will produce a more steady supply of electricity through the day than installations where panels face a single direction.<\/p>\n

Basic String Theory \u2013 Why An East\/West Split On A Single Input\u00a0Seems Like A Bad Idea<\/h2>\n

Putting an east\/west split on a single inverter\u00a0input\u00a0sounds like crazy behaviour.\u00a0 Not quite as bad as installing solar panels upside down, but getting there.\u00a0 Apart from when the sun is directly overhead, one set of panels will always be receiving less light than the others and so will drag the performance of the whole system down. But it actually does work, because when done right, the differences between the levels of light the panels receive will not be very large and there are a couple of small advantages that help compensate for the mismatch. However, there are some conditions:<\/p>\n

1.<\/strong>\u00a0The two sets of panels must be identical in number.
\n2.<\/strong>\u00a0They must be on a gently sloping roof.
\n3.<\/strong> They must be very close to facing directly east and west.<\/del><\/p>\n

Update July 2020:<\/strong> Since this post was written many years ago, we have seen a number of examples of Australian solar systems working well with equal:<\/em><\/p>\n