How Does Solar Power Work?
Converting the energy from the sun into electricity you can use in your home is a beautifully simple concept with highly technical details. When we begin working with new customers, we are often reminded of just how many new terms and concepts are involved in the decision to go solar.
Here, we’ve explained some of the standard elements of a typical solar set up, describing why they are needed and how they work. Getting familiar with these components can be helpful as you navigate the proposal process, and also as you begin living with your new solar set up.
Don’t worry, there won’t be a quiz -- we’re here to keep you informed every step of the way.
Photovoltaic “PV” MODULES:
Each photovoltaic module (what most people call a solar panel) is a collection of what looks like little blue or black squares joined together within a metal frame covered in glass. These blue squares are called photovoltaic cells, and are what produce electricity in the modules. Photovoltaic cells consist of two layers of silicon, sandwiched together. Various elements are added to either layer, so that the top layer is positively charged, and the bottom layer is negatively charged. This creates an electrically charged field. When photons from the sun hit the photovoltaic cells, electrons are pushed free from atoms. The electrons are collected and aggregated in metal plates called busbars on the edges (and more recently in the center) of the modules, then flowing through copper wires as direct current (DC) to the inverter. DC system voltages are typically 300-400 Volts for residential systems and can be up to 1000 or more volts in industrial applications.
The modules are mounted on a racking system that is especially designed for either a rooftop or ground mount installation. (We will dive into racking 101 in another blog post).
INVERTERS:
To be compatible with the electrical grid, the electricity produced from the PV modules needs to be converted from a constant DC voltage into alternating current, or (AC) in residential applications that would typically be at 240 Volts, and 208 and 480 VAC three phase in commercial and industrial application. Inverters convert the steady electrical voltage of photovoltaic DC current into a “sinusoidal” waveform that can be modified efficiently to travel very long distances through the electrical utility “grid” system. The interconnection of a DC power source to a bi-directional utility meter that is part of the public electrical network is called “net-metering.”
Inverters allow for net-metering and they contain safety relay devices that monitor and regulate the frequency, voltage and stability of the electrical network connected to your homes “net-metered” system through the IEEE (Institute of Electrical and Electronic Engineers) 1547 standard, UL listings and by compliance with the NEC code.
Inverters are also now coupled with online monitoring applications that allow you to access historical and real-time data from your system about the production and the electrical characteristics of your system. Additionally, inverters are now being integrated with EV chargers, home energy storage batteries and whole home energy monitoring systems to give you and your electrical utility provider greater precision, safety and reliability than ever before.
STRING INVERTER VS. MICROINVERTERS:
Historically, net-metered solar electrical systems have been installed with multiple pv modules in series (like a flashlight with each battery connected from plus to minus of the previous battery) building voltage with each connection up to 600 Volts DC, coming down from your roof to one inverter, which then feeds into the house. The past ten years have seen a shift to micro-inverters and optimizers, with all rooftop solar now required to use them. With microinverters, each module has its own inverter attached to the back of the module itself. Multiple microinverters are then joined together using a listed, manufactured wiring harness, and that set of wires is brought into the home distribution panel using common and reliable electrical construction materials like metal conduit and copper wire.
An advantage of microinverters and optimizers is production loss is not as severe in partial shade conditions which are common in residential yards with trees. An additional benefit of these module level electronics is the ability to monitor each pv module individually, which can be invaluable for quantifying the impact of a growing tree or should there be a need for troubleshooting. With long warranties these products are built to last, but, if we cannot see the individual components it can be difficult to determine where issues might be affecting our returns.
SOLAR PRODUCTION METER AND PV DISCONNECT:
From the inverter or inverters wires feed into a solar production meter, installed by Green Mountain Power, or your local utility, to measure your solar production. From the production meter power flows to a disconnect switch, which will shut off the system completely in an emergency.
From the PV disconnect, our electrician will finally connect the solar to your home electrical system. The method of interconnection depends on several factors, such as the size and capacity of your electrical panel or if there is a generator connection. Our team will work with your existing wiring or with upgraded capacity in mind to connect your system in the safest way possible, and to give you the greatest flexibility and choice.
Solar installations in the northeast are not one-size fits all. Your system details may vary slightly depending on the most optimal installation for your home, your budget and your lifestyle.
We are skilled electrical experts that know how to make these pieces come together safely and efficiently for your unique project, and we look forward to making solar work the right way for you!
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