I have always been fascinated by solar power. There’s something quite intriguing about the idea of simple sunlight hitting a solar panel and instantly producing electricity.
Home solar systems can take a few different forms. There are power backup systems that require the use of battery storage, as well as systems that allow people the luxury of electricity that live completely off-grid. Today, the most popular form of solar by far is known as grid-tie or Net Metering.
Grid-tie Net Metering
With grid-tie net metering solar power systems, no batteries are used. Grid-tied solar panels feed power back directly into the public electrical grid and can actually make the power meter run backwards. The more solar panels integrated into the system, the more potential power can be fed back into the connected electric grid. Power bills can either be reduced, or in some cases, completely zeroed out, depending on local electric power company policies.
Solar panels produce DC or direct current. The power grid is AC or alternating current. Therefore, to sell power back to the electric utility, it is necessary to convert the DC power coming from solar panels into AC so it can be fed into the power grid. This is accomplished with DC to AC power inverters.
I recently visited a home solar system installation where the home owner has been slowly expanding his net metering system over the past seven years. He initially began seven years ago with forty-three 100 watt 12 volt solar panels, placed on top of his workshop.
With this first system, it was necessary for him to run wires down the length of the interior roof to a bank of mounted micro-inverters that needed to be protected from the weather. One of the lessons he learned from this initial installation was that lengthy wires carrying 12 volt DC results in power loss. The longer the lines, the more the efficiency drops. Higher voltages don’t experience as much line loss.
The best way around this problem is to mount weatherproof micro-inverters directly to the backs of the solar panels. Once the power is converted to 120 volts AC, the length of the wires to the grid connection point are somewhat less critical because the voltage is higher.
With the second phase of his foray into solar, he built a rack on a metal pole complete with a sun tracking mechanism that he built and wrote control software for himself. The rack contains nine higher efficiency 280 watt 24 volt panels with weather proof micro-inverters attached to the backs of the panels.
The weatherproof micro-inverters are of a modular design that can allow additional inverters to be plugged in to the to the system. The rack-mounted system produces as much power as the workshop roof-mounted panels, even though they have less surface area, primarily because they are higher-efficiency panels.
He is currently working on phase three of his system, which consists of panels that form a sort of porch canopy over the garage door entrance to his workshop.These are also 280 watt panels, each with its own micro-inverter. He is in the process of slowly adding additional panels to continue expanding his overall system capacity.
At the moment when I took this picture of the system output meter, the total output was about 5.4 kilowatts.
A great way to learn more about solar panels, inverters and net metering is YouTube. Good search terms include solar power, grid-tie, and inverter.
Many recreational vehicle enthusiasts have developed a strong interest in attaching solar panels and power inverters to their RV’s, which can allow them to have a measure of generator-free and thus noise-free AC power and engage in extended off-grid camping.