Solar Energy Systems Course Class 5
Class five focused on solar PV system components. We discussed charge controllers, mounting options, inverters, combiners and batteries.
Although the solar modules (or panels) are the most expensive and most visible piece of any solar system, they would be worthless without the various components they connect with and feed power to.
Charge controllers regulate the amount of energy distributed to batteries so that the batteries do not overcharge, which is critical to the long term health and operability of the batteries. There are, of course, various types of charge controllers available:
- Pulse with Modulation (PWM) controllers are the most simplistic controllers available. They are switch-based and send power to charge the battery when the switch closes the circuit.
- Diversion controllers are smarter than PWM. When the battery is charged, these controllers have the ability to send the power to another place.
- 3 Stage controllers are even better - they can switch into 3 modes. In bulk mode, the controller will send all available current to the battery (like PWM0. In absorption mode, the voltage being delivered remains constant while the current is decreased. In float mode, the battery can be trickle charged.
- Maximum Power Point Tracking controllers are the best option and what most people use today on battery-tied systems. These controllers track the module IR curve and send the right amount of voltage to the battery. These controllers make it easier to match a high voltage array with a lower voltage bank of batteries (which is typical).
After controllers, we discussed the different module mounting options. This boils down to roof mount, ground mount and pole mount. There are various pros and cons for each type of mount. For example, roof mount typically looks better, but the panels can get very hot in the summer time up there. Heat creates resistance in the circuit, so the hotter panels get, the fewer volts they produce. The ground mount will not be as hot, but it is more susceptible to damage or theft. A pole mount can offer easy access for repairs or maintenance, but it can also be an eye sore. Like most things in this world, there is no best single best option. The site and personal preference will play into the equation.
We wrapped up with info on inverters, combiners and batteries. My take-away from this (pretty boring) class was that the devil is in the details. You can see from the notes above that there are a lot of different options available, at different power points and at different price points. As a solar installer, if you don't nail down the system components and deliver the customer a solid quote, you won't be in business for too long. Obvious, yet a good dose of reality.