A solar power system is composed of many electrical and mechanical components, beyond the solar panels themselves. A racking system is used to keep the panels firmly anchored to your roof, and they are connected in circuits with special weatherproof wiring.
The strings of solar panels are then connected to an inverter, which converts their electricity output from direct current (DC) to alternating current (AC). Also, most solar installations now include a monitoring system, which can be used to track productivity and detect performance issues.
There are also optional components such as batteries, which convert your solar panels into a 24/7 power supply. Depending on how your system is designed, a battery may be wired in different ways.
You can use a hybrid inverter designed for both solar panels and batteries, or you could install a separate battery inverter, if the unit connected to your solar panels is not compatible with them.
Here we will review the installation process of solar panels. Note that this blog post is informative and is not intended as a DIY guide.
A professional installation is strongly recommended if you want to use traditional solar panels, due to their weight and the risks of working at height with electrical components.
If you’re interested in a simpler DIY project, there are specially designed solar panels you can purchase online. These PV modules are smaller and lighter, and the voltage and current involved are much lower, making them safer to handle. These DIY solar kits also have built-in supports, so you can deploy them outdoors or on a balcony (no roof work involved).
Mechanical Support: The Solar Racking System
From ground level, it may seem like solar panels are attached directly to your roof. However, they are actually installed on a racking system that is anchored to the roof structure. The racking system provides higher mechanical strength and a safer installation, and there are two main installation options:
- If your roof has shingles or tiles, some of them will be removed to access the roof structure directly. The racking system is then attached with penetrating mounts, and flashing is used to keep water and moisture out.
- If you have a standing seam metal roof, there is no need for penetrating mounts. The racking system can be attached directly to the roof structure with special clamps.
Solar panels attach to the racking system with clamps and bolts, regardless of how the racking rails are attached to the roof structure. Solar panels are normally supported by two rails, and there are two main types of clamps.
Middle clamps are installed between solar panels in the same row, while end clamps are used to hold the first and last solar panels in a row, as you might guess from their name.
Most solar panel sizes can be installed with two racking rails, but these must be properly spaced to provide adequate support. For example, a 72-cell module will need more spacing between rails, compared with a 60-cell module. This also means that larger modules save on racking, since they have the same width.
In other words, when installing 20 solar panels, you will use roughly the same amount of racking regardless of their size (60-cell or 72-cell).
Having a reliable racking system is just as important as having high-quality solar panels and adequate wiring. Keep in mind that solar panels can last for more than 25 years, and you need a structure that can hold them in place for that time.
The last thing you would want is having to replace a defective racking system when the solar panels are still in perfect condition. The solar racking system must also be capable of withstanding the highest winds that can be expected in your location.
Solar panels are easier to install if you have a standing seam metal roof, since there is no drilling involved and hence, the risk of inadvertent water leakage is almost zero. When using penetrating mounts on a shingle or tile roof, extra care is necessary to prevent water leaks.
However, there should be no issues if the installation is carried out by professionals and flashing is used properly. Make sure you ask for the warranty conditions of the racking system before accepting a solar quote.
Importance of Solar Panel Positioning
Other than having a reliable racking system, solar panels should be positioned for maximum productivity. When solar panels are installed on the roof areas that get the most sunshine, they generate more electricity, and your power bill savings are higher. This also means you get a higher return on investment: each dollar spent upfront yields more dollars in long-term savings.
Unfortunately, the opposite is also true: if solar panels are installed on roof areas that are constantly shaded, their productivity is drastically reduced. Power bill savings are lower, the payback period becomes longer, and the return on investment is decreased.
A qualified solar installation company can assess your roof before starting the project, to determine which areas are optimal and which areas should be avoided.
Assuming that shadows are not an issue, south-facing roof sections normally get the most sunshine in northern hemisphere countries like the US. As you might guess, north-facing roof sections get the least sunshine, especially if they have a high pitch.
Solar panels installed on east-facing roof sections are more productive during the morning, since the sun rises in that direction, but this also means they are less productive in the afternoon. Solar panels on west-facing roofs have the opposite behavior: high productivity in the afternoon, and lower productivity in the morning.
Solar modules should be firmly anchored to your roof, but the array should also have a layout that maximizes generation. If you want the highest possible kilowatt-hour output, south-facing roof sections that are not shaded should be prioritized.
However, an east-facing array can make financial sense for a building that has most of its consumption in the morning, and the same applies for west-facing arrays on buildings with high consumption in the afternoon.
Solar Panel Electrical Requirements: Wiring and Inverters
You can install a single solar panel on your roof, and it will generate electricity, but you will probably save only a few dollars per month. To reach significant electricity production, you will need several solar panels. For example, if your home needs an 8-kilowatt solar system and you choose a PV module with a capacity of 370 watts, you will need 22 panels to reach 8 kW.
Solar panels generate direct current, but your home appliances need alternating current. The DC power produced by solar panels in converted into AC with the following steps:
- Solar panels are wired together in series circuits, which are also called string circuits in the solar industry. When the panels are connected in series, the same DC current flows through them, and their DC voltages are added up.
- String circuits are connected to a solar inverter, which converts the combined output of all the solar panels in the circuit into AC power.
- Since solar panels are exposed to the outdoor environment, their wiring and connections must also be weatherproof. This is achieved with MC4 connectors.
Keep in mind that the system also needs electrical protection. DC breakers are used for the direct-current circuits behind the inverter, and AC breakers like those on your fuse box are used for all alternating-current components in front of the inverter.
Solar inverters are capable of synchronizing with the AC voltage and frequency provided by the local electric company. This means you can use both electricity sources at once, without having to switch between the PV system and the grid. A manual disconnect switch may be required by local codes as a safety measure, but there is no need to switch between both power sources.
- When your solar panels are generating less electricity than what your home is consuming, the difference comes from the grid.
- When your solar panels are generating more electricity than what your home needs, the difference goes to the grid, and you get a power bill credit in return.
Most solar inverters now include a monitoring system, which is available as a standard feature. This means there are no additional installation steps involved, other than a simple initial configuration.
Solar monitoring systems can normally be accessed via WiFi and other common communication protocols. Most of them have a web dashboard you can open on a computer, and a mobile app where you can check solar generation on your phone.
Adding a Solar Battery System
Energy storage is an optional feature when installing a solar power system, but it offers additional benefits. For example, you can use charged batteries at night, or on cloudy days where solar panels have a much lower productivity.
Depending on the battery specifications, it may be possible to use it as a backup power system during blackouts.
There are many types of solar batteries, but they can be classified into two broad categories based on their installation requirements.
DC-coupled batteries are connected to the same inverter as your solar panels, but you must plan ahead by purchasing a compatible hybrid inverter. On the other hand, AC-coupled batteries have their own inverter, instead of sharing one with your solar panels.
DC-coupled batteries normally offer a higher efficiency since there is only one inverter and there is no need for additional conversions between DC and AC power. However, AC-coupled batteries are easier to install if you already have solar panels with a traditional inverter that is not compatible with batteries.
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