Lessons and Tips I have Learnt on my Solar Installation
Some lessons I have learnt over the last year after having to replace one or two components are:
1. Save now, and you will replace later. Also you need to decide if you want a full system to power everything, or just want something to power the lights and some essential equipment.
2. Try go for 24V as it is more efficient, and cheaper cabling too. So buy batteries in pairs so that you can create a 24V system.
3. If you want remote management, make sure what system each device can report to. It won’t help buying one Victron inverter but using an Ellies solar charge controller as you will have to go to two or three places to look at what is happening.
4. The heart is the batteries:
a. You only get to use 50% of the stated capacity as you cannot run the batteries down to below 50% - so a 300Ah battery capacity is going to give you 150Ah of real use.
b. Work out what you want to power – the max load (peak) at any time, will determine what size inverter you need. The total amount of power used during the night for everything with some spare left, will determine what capacity of batteries you need.
c. Lead acid is fine for backup or UPS functionality, but if you intend to cycle the batteries down to 50% daily, you will need better batteries. It will be deep discharge batteries needed.
d. You can wire batteries in serial and parallel to get your 24V and enough capacity – but total capacity is is determined by the total number of batteries you buy.
e. You are not supposed to mix different capacities, brands, and old/new batteries, otherwise you stand to kill your newer batteries. So try buy the right number to start with.
f. Don’t connect the inverter and solar charge controller all to a single battery's terminals. Connect their negative to one battery, and connect their positive to a battery on the other end of a parallel setup – this spreads the load more evenly across a parallel setup.
5. Solar panels can also be wired in parallel to get more current, and with a 24V system you can even put them in serial to get 24V. You need to buy enough so that it can run your daytime usage (normal current used for a sunshine day, plus to charge your batteries. So four 120W panels are charging my 300Ah batteries and running other stuff in the day. But 600Ah batteries will likely require 8 panels. Obviously and extra panel or two is going to help for overcast days.
6. On the solar charge controller (this regulates the power from the solar panels to be safe for the system and the batteries):
a. Luckily they often are dual 12/24V output so you only have to consider their maximum Amps and Volts they will handle, and the type of controller.
b. Maximum Amps will determine how many solar panels you can add to it (look at maximum output of the panels eg. mine are about 6Amps per panel.
c. Maximum Voltage input is important because it also determines how many panels you can connect in serial (as the Voltage is higher, which is more efficient and cheaper cabling again).
d. The PWM controllers are cheaper, but are also slower to respond to partly cloudy weather so you lose efficiency. The MPPT controllers cost more but are much faster and more efficient (and recommended that you wire the panels in a 24V configuration for MPPT controllers, as they will start charging quicker in the mornings).
7. On the inverter (converts your battery voltage to 220V) they are often a set input voltage (12V or 24V) so your battery setup helps determine this choice and then you stick with it unless you want to replace the inverter later on. But consider also:
a. Continuous power rating (in Watts) – this is the constant load it will support. In my house the LED lighting, a pond pump, lounge TV, a computer, and the Internet modem and router all draw about 300 Watts at 220V. But kettles, geysers, etc are going to be at least 2kW each and remember they can run together. Someone did say that electricity is not the best way to cook and heat – and gas may actually be better for them, which lowers the cost of your solar system.
b. Their peak power rating (this handles short spikes like for a fridge motor switching on – if not high enough, a fridge will trip your system). So often you will see 600/1200 as a spec which implies 600Watts continuous power and short peaks of 1200 Watts can be handled.
c. You get standard inverters (just invert the power to 220V) and you get inverter/chargers (where the latter will also supply 220V to charge the batteries on say cloudy days, and they will often also act as automatic UPSs where they will switch to batteries if the grid power is off, or vice versa. It all depends on the battery type and how the inverter/charger can be setup and programmed so it is worth discussing these expectations to be sure of what is possible.
a. You do need a registered electrician for any 220V that connects to the house. And get an electrician who has experience with solar as from the above, you will appreciate their are nuances over and above what an electrician knows about 110/220V systems.
b. You do want a separate distribution board installed so that any circuits running from the inverter, are separate from any direct Eskom fed 200V circuits.
c. If you are mixing grid and Inverter power, you may find that some of your plugs and lights share common negative, and these will need to be separated by the electrician.
d. You do need to have fuse/isolator switches fitted to isolate power from the solar panels, from batteries, from inverter, and also for any power going into the sub-DB.
e. There is also usually a switch fitted to select between inverter and grid power supplying the new sub-DB so that if there is any fault on your solar setup, you can switch to just using normal grid power to those circuits.
9. Management: With systems like the Victron you also need something like a Color Control GX (CCGX), which is essentially small Linux computer with a status display – it pulls the data together and transmits the data to Victron’s cloud (where you can monitor it remotely or have alarms sent to you). Some of the individual devices will connect via Bluetooth devices but a single central monitor is better.
I hope these tips will help newbies before they start out, to ask the correct questions when planning a system. If anyone else has additional tips, or corrections, please add them in the comments.
Photo credit: https://en.wikipedia.org/wiki/Photovoltaic_system#/media/File:Fixed_Tilt_Solar_panel_at_Canterbury_Municipal_Building_Canterbury_New_Hampshire.jpg