Solar Panel Installation On The Roof Of My Home
The idea of having solar panels generating my electricity has always interested me. There is just something about generating your own power that is satisfying. Recently, I was in a position to be able to start looking into the possibility of installing solar panels on my roof, however I had some questions. Mainly should I go off-grid, or have a grid-tie solar system. I also wanted a system that I could easily add on to in the future.
Grid-Tie or Off-Grid
When people think of Solar panels, they typically think of what is called an off-grid system. That is, one where the Solar panels, and the electricity generated from them are separate from the traditional power grid. However with improved technology of micro-inverters, it has become much more cost effective to go with a grid-tie system as opposed to an off- grid, if you already have conventional power in your house.
By choosing a grid-tie system over an off-grid one you are cutting the overall cost by over half. You also eliminate the need for having batteries, which is where most of the cost savings are. Not to mention having to replace the batteries every 5 to 10 years. Additionally, there are serious power losses in charging batteries for solar. One source puts that loss as much as 40%.
Having decided on a grid-tie system, a question that is asked often is “how does that work?” Especially since solar panels generate DC voltage, and conventional house current is AC voltage. Recent developments in solar energy includes a device called an inverter. An inverter does a couple of things. First it tracks the instantaneous voltage of the 60 Hz sine wave that powers our houses. Then it takes the DC power generated by the solar panel and converts it to precisely match the 60 Hz voltage of your house. This is done in such a way that the power generated by the solar panels is what your house uses for its power. Any extra power that is generated by the solar system is pushed back on to the grid. Yes, the electric meter actually runs backwards when this happens.
Micro-Inverters or String-Inverters
There are two main types of inverters. There is the string inverter, and the micro-inverter. The string inverter is usually quite large, and mounted near the service entrance inside your house. The solar panels are connected in series (as in a string..), which often generates as much as 600 volts DC. The string inverter then converts this high DC voltage into 240 VAC.
The micro-inverter does basically the same thing, just on a much smaller scale. Each solar panel has its own micro-inverter that converts the solar panels DC voltage into 240 vac right behind the panel.
I chose to go the micro-inverter route even though the initial cost is a bit higher. Here are my reasons. With a string inverter there is a single point of failure. That is if it fails, your whole system is down. With microinverters, if one fails, it only shuts down one solar panel instead of your whole system. Another advantage is if you solar installation is partially shaded, like mine is, with a string inverter having just one panel shaded will greatly reduce the output of your system if not completely shut it down. With micro-inverters on the other hand, any solar panel in your system has full sun, it will provide full output irrespective of the other panels. Using micro-inverters instead of string inverters also makes your solar system more easily scalable for future expansion.