We finally had a photovoltaic array on our roof. The solar cells on each module produce direct current (DC). Yet the electricity we use in our buildings is alternating current (AC). To convert the direct current into usable alternating current, we need an inverter.
The direct current from the solar array flows to the inverter, where it is changed to alternating current. The inverter is feeding the electricity into our electrical panel (or load center), from where the alternating current can power electrical loads in our home, such as the heat pump, fridge, dishwasher, vacuum, lights, the TV and radio, our PC’s and laptops, etc. It also feeds electricity back into the electrical grid, which is a process I described in the blog post “How to connect a solar system”.
In other words, our photovoltaic array is not functional, unless it is connected to an inverter.
I had saved some wall space for the inverter in the basement next to our load center. I also had installed a conduit run from the basement up to the roof during construction when we had all the walls open so the big stretch in the middle was already in place. That came very handy, because the electrician just had to install a little bit of extra conduit in the basement and on the roof.
The inverter got wired up from the roof side and connected to the main load center. It also got connected to the internet via our router. That way I can monitor our solar production in real time by logging into the online interface of our inverter.
This sexy little white box has some additional safety functions built into it, such as an automatic safety disconnect, which is an important feature if you have a grid tied system like ours.
The inverter can tell in an instant if there is a power outage. If so, it automatically turns off (or disconnects) and no longer feeds any electricity from the photovoltaic array into the load center and into the electrical grid. This is important because we don’t want to electrocute any line workers fixing the grid during an outage because we are still feeding power into it.
The same safety consideration applies to any maintenance or repair work on the photovoltaic array. By turning off the inverter, we can draw down the power in the roof array and won’t run the risk of getting shocked by a jolt of DC current.
This covers the practical aspects of the inverter installation, which is only half the story. The other half is about connecting to the grid or not and the administrative and contractual implications. These are described in detail in the blog post “How to connect a solar system”.
If you find any of the solar terminology confusing, you find answers in the previous blog post “Solar lingo”.