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Solar energy systems come in a variety of configurations. Whether your panels are mounted on your roof, ground-mounted on your property, or you are drawing from a nearby solar array (community solar), the basic science and the core components are the same.
In a nutshell: Renewable, clean energy from the sun is converted into electricity for your home or business.
When you have your own solar energy generating system, you will most likely connect to your utility company’s energy grid – this is the least expensive and most prevalent residential solar system in the U.S. You also have the option to own battery storage, where you can store the energy your solar system produces so you can draw from the batteries when your system is not generating the energy you need. The battery bank can ensure a constant supply of self-sustainable energy; however, batteries are expensive and new technology is being developed every day to help lower the cost. There is also a third option, which is a hybrid combination of the grid-tied and solar battery backup.
A grid-connected home solar power system is made up of several basic components:
- Photovoltaic (PV) solar panels, assembled to create a solar array
- Solar inverter
- Net energy meter that ties to the grid
There are also mounting systems, cables, connectors, and safety features including an on/off switch for your solar system and AC/DC disconnects.
Solar panels absorb sunlight (photons). When the photons interact with PV cells in the panel, electrons become active and convert the energy into direct current (DC) electricity. This process is called the photovoltaic effect. Wiring then feeds the DC electricity to your solar inverter.
A solar inverter converts the DC energy produced by your solar panel system to alternating current (AC) electricity – the type of electricity that powers your home (and pretty much the developed world).
The AC electricity from your inverter then flows to your home electrical panel to power your lights, HVAC, appliances and electronic devices.
A meter device. If you generate more solar energy than you use, the electricity goes to your utility company’s energy grid. Conversely, when your solar array is not delivering enough energy to meet your home use (at night or when it’s cloudy), you draw electricity from your utility company’s grid. The meter (or a combination of meters) tracks your energy production, measures and reports the electricity going to and from your energy company. Enter net metering, aka net energy metering (NEM), which is a billing agreement you have with your energy company based on: (1) the power your system produces and (2) the electricity you use in your home. When your system sends excess power to the grid, your energy company will credit your energy bill.
Net metering practices vary by state (some states do not offer net metering) and energy company, with varying payments or credits for the excess solar power you export to the grid.
A bit more about those components
There are various features and options among the key components of a solar renewable energy system. As solar technology continues to advance and prices drop, a wider variety of options are becoming more available to homeowners.
Photovoltaic (PV) solar panels. Solar panels contain PV solar cells made of silicon. There are several types of solar cells, with monocrystalline (a single silicon crystal) and polycrystalline (fragments of silicon) used for most residential solar panel installations. The types vary by grade of silicon used, manufacturing technology, production efficiency, cost, space-efficiency, appearance, temperature tolerance, susceptibility to dirt and shade, performance in low light settings, carbon offset and lifespan. For example, the mono system offers higher solar panel efficiency that performs well with lower light, but it comes at a higher price. The polycrystalline system may meet your needs and costs less. Another technology used more often in commercial applications, the thin-film solar cell is lightweight and flexible, but comes with greater space requirements and lower efficiency.
Back to the panel (also referred to as a module). The solar cells are grouped on a backsheet that protects the panel from moisture, UV light and debris. Protective glass above the cells also provides protection from the elements. Anti-reflective coating on the glass increases sunlight absorption and allows the silicon cells to receive maximum sunlight exposure. A layer of insulation under the glass helps control temperature and humidity inside the panel. The panels are set in a metal frame and assembled into a solar panel system (array) that is mounted on your roof or ground-mounted.
In choosing solar panels for your home, where you live and the features of your property will come into play. The quality of the manufactured components and product warranty are equally important considerations. You’ll want to check if the panels contain materials that have been tested by labs and certification organizations. OSHA publishes a list of Nationally Recognized Testing Laboratories (NRTL). Warranties should be at least 10 years, and you can aim to double that figure. Some of the best solar panels on the market offer efficiencies upwards of 22%, competitive pricing durability and a 25-year warranty.
Solar inverters. There are three types:
- String inverters (also called central inverters) are the most cost-effective option and the most widely used technology. The inverter is usually located on an exterior wall, your garage or basement and the DC electricity travels from the PV array to the inverter for conversion to AC. String inverters represent the entire solar array, so if one panel is not at optimum production (from things like shade or dirt), performance of the whole solar array is impacted.
- Microinverters are attached directly to each solar panel and convert the DC electricity to AC electricity at the source. Your system is able to draw the maximum benefit from each panel for optimal system performance. You don’t need a central inverter. This is the most expensive option.
- Power optimizers (also called DC optimizers) do not make the DC-AC conversion, but maximize the DC power before sending to the central inverter. Power optimizers may be attached to specific modules (for example, those affected by shading) to maintain optimal power output along the string.
Microinverters and power optimizers are also called Module-Level Power Electronics (MLPEs).
Inverters also provide safety features such as rapid shutdown capability and ground fault protection. Your inverter will enable you to monitor your solar array’s energy production with real-time and other usage statistics, check voltage and current on DC and AC circuits, and see individual panel output to diagnose problems. The information is readable off your inverter panel, or you may be able to view the information online or through an app.
Meters. There are various types of meters and configurations, with the meter type (and metering fees) generally depending on your energy company.
- A bi-directional utility meter indicates energy used in your home that is drawn from the energy grid and excess energy produced by your PV solar system that is distributed onto the grid.
- Or you may have a dual metering system with two unidirectional meters – one measuring energy you draw from the grid (this could be your existing meter) and an added meter for measuring solar energy pushed to the grid.
- A net meter will show your net consumption of power, indicating the difference between solar energy out and grid electricity drawn in – and it will actually run backward when you are producing more solar energy than you are using.
Smart meters are digital devices that will record your home energy use and communicate with your energy company using a wireless network or powerline technology. Your provider will then use the data to calculate your energy use and monthly electric bill.