I actually did this work earlier in the summer but never got around to posting it. We decided to install another 4kw of solar pv, principally to allow us to run immersion heaters in both cottages over the summer and thus almost completely remove the need for lighting a fire, but also to help us get through the middle of winter, which has tended to be when we get a bit close to the wire, power wise.
The new solar array is all made up of 300W panels, which we ground mounted on plastic buckets, which are weighted with hardcore to stop them moving around. The panels are simply connected in series, meaning their voltages are added together. THis puts out around 500V DC, which is fed to a Platinum grid tie inverter. It’s certainly the heaviest thing I’ve had to attach to a wall and must be aroung the 40kg mark. It was an older one going cheap but it works great, and its happy with the AC profile that the Victron Multiplus inverters (24/3000 units, 3 of them) are putting out.
So in deciding to add this to the setup, we also needed to put in a third MultiPlus to cope with potential peak loads from the solar and wind. The knock on effect of that was not having enough room to put everything on the wall as it stood, so I decided to rip it all out and start again. This was overdue anyway, as the old arrangement had grown over the years and definitely wasn’t the tidiest.
All the MPPT solar charge controllers were moved and mounted the right way up this time to allow for proper cooling, and the isolation switches all grouped together so that they can actually be reached easily. Below those is a duct with all the MPPT and switch cabling, and now all the output from the MPPT controllers goes to a proper heavy busbar, and on to the inverters. This makes it a) safer and b) easier to add more MPPT’s as the solar grows. The multis also have individual direct cabling to the battery pack now, which is the correct way to run them given the potential currents being generated.
We also put the CCGX color control and BMV 700 units in a proper victron housing for tidyness sake.
On the AC side, we added two Victron energy meters, one each for the wind and grid tie solar, as the old current sensor was very clunky. All the AC was moved into a proper unit, cabling resized and disconnects and MCB’s for the houses and generators added. This has hugely simplified the AC wiring.
The other addition is a Solar iBoost Plus unit, which is essentially a load diversion unit that takes AC output from the WInd turbine and grid tie solar, and sends it first to one immersion heater, then another. The first 300W of power comes into the batteries at all times, and once each immersion reaches top temperature, the full power of the array goes to the battery, and we control voltage with the multiplus relays and our dump loads in the form of space heaters.
The next step is to rearrange some of the solar panels. We’ve a collection of 100w, 175w and 80w panels that would perform a lot better if they were all on an unshaded bit of roof, so its looking likely that I’ll shift them all to the hay shed roof soon and make better use of the available MPPT controllers.
