A solar power system is composed of many interacting components. Photovoltaic panels are responsible for converting sunlight into electricity, but you need additional devices to achieve a reliable voltage supply. Here we will discuss the main parts of a home solar system, and how they work together to provide electric power.
Main Parts of a Home Solar System: Understanding How They Work Together
Solar panels are the largest and most visible part of a photovoltaic system. However, you also need an inverter to convert their electricity into a form that can be used by your home devices, and a racking system that will keep them firmly attached to your roof. Being an electrical installation, a home solar system must also be protected by circuit breakers.
1. Solar Panels
Solar panels are becoming very popular in the US, and the country’s installed capacity surpassed 100 gigawatts early in 2021, according to the Solar Energy Industries Association. To put this number into perspective, this is enough generation capacity for 18.9 million homes. According to optimistic growth projections, the US could surpass 300 GW of solar power as early as 2026.
In simple words, a solar panel can be described as a device that provides electric power when absorbing sunlight. This is achieved by using high-purity semiconductor materials, which have the ability to energize electrons by absorbing light. The resulting electron movement creates a voltage difference across the terminals of the solar panel, and current flows if you connect an electrical load.
- There are three main types of solar panels: monocrystalline panels have the highest efficiency, polycrystalline panels have intermediate efficiency, and thin-film panels have the lowest efficiency.
- There is a common misconception that less efficiency means lower product quality, but this is just a technical specification.
- You can find quality solar panels of all three types, but mono panels give you the most watts per square foot covered, thanks to their higher efficiency.
Solar panels are unable to power your home devices on their own. They generate direct current (DC) just like a battery, which means the positive and negative voltage terminals remain constant.
On the other hand, your home appliances need alternating current (AC) like that from the grid, where the voltage is switching polarity 60 times per second. You need to convert the power output of solar panels from DC to AC, and here is where the inverter comes in.
2. Solar Inverter
The inverter is a device that converts the power output of solar panels into a form that can be used by your home appliances. In fact, the voltage that comes out of the inverter is identical to the grid voltage, and this means the solar inverter can synchronize with the grid. This means you can wire both power sources together, and there is no need to switch manually between solar panels and the grid.
- Thanks to this synchronized connection, your home can use electricity from the grid and from your solar panels at the same time.
- If there is a time of the day when you have surplus electricity from solar panels, it can be exported to the grid. This amount is measured by your power company, and subtracted from your next bill. This concept is called net metering, but keep in mind that not all power companies offer the benefit.
- Modern solar inverters come with built-in power metering, and they often include a mobile application to keep track of your electricity production.
Solar inverters can be classified into three main types: string inverters, microinverters, and string inverters with power optimizers. As you might guess, each type has advantages and disadvantages.
String inverters are often referred to as traditional inverters, and they are the most common type. Your solar panels are wired together into a series circuit or string, which is then connected to the inverter. Residential string inverters can normally manage two or more circuits, and the exact number depends on the specific product you’re using.
- String inverters are the least expensive, but solar panels must be grouped and wired carefully to achieve high productivity.
- If the installer is careless and one panel is placed under the shade, all others in the same string circuit become less productive.
Microinverters are installed directly on solar panels, which means they all operate independently. If one solar panel is shaded or malfunctioning, the rest are not affected because each has its own inverter. With this system configuration, the main disadvantage is having to install one microinverter per panel, and this makes the system more expensive.
- Microinverters are normally recommended for complex roofs with uneven shading, where solar panels cannot be grouped effectively into string circuits.
- Otherwise, a traditional string inverter is the most cost-effective option.
String inverters with power optimizers can be considered a combination of the two types above. Solar panels are grouped in circuits, and their output is converted from DC to AC by a single inverter.
However, each panel is equipped with a power optimizer, which is an electronic device that adjusts voltage and current to increase productivity. Just like microinverters, these systems are normally recommended when roof geometry and shading don’t allow an effective distribution of solar panels into strings.
3. Racking System
Solar panels are very durable, but they can cause severe accidents if they are not attached firmly to your roof. Poorly installed solar panels can be sent flying by a strong wind, and each of them weighs 40-50 pounds (depending on the brand and model). To prevent accidents, you need to use an adequate solar panel racking system.
Solar panels are compatible with most types of residential roofs. This includes asphalt shingles, standing seam metal roofs, cedar shingles and shakes, clay tiles, concrete tiles, synthetic tiles, EPDM rubber, PVC and TPO.
- Solar racking systems normally use a standard penetrating mount, but they can be clamped in place without drilling if you have a standing seam metal roof.
- Ballasted mounts are also an option if you have a flat roof with enough structural capacity. This type of racking system is simply held in place with concrete weights, and no drilling is required.
- Getting a professional installation is very important, or otherwise your roof may be damaged during the installation.
Installing solar panels is not recommended if you have an asbestos roof, since the fibers released when manipulating or drilling the material are extremely hazardous. In fact, many solar companies will decline all work on asbestos roofs as part of their policy, to protect the health of their installers.
4. Electrical Protection Devices: AC and DC Circuit Breakers
Solar panels are environmentally friendly, but we must not forget they are electrical devices. An array of solar panels can produce high current when operating at full capacity, and you must have adequate protections in place.
- If there is a dangerous condition like a ground fault or a short circuit, the electrical protections will immediately disconnect your system.
- Without them, there is a much higher risk of equipment damage, electric shock and fire.
Since a solar power system has both DC and AC components, you need the right type of electrical protection in each case.
All components behind the solar inverter are protected with DC breakers, and AC breakers like those in your fuse box are used at the inverter output. These protections ensure that your solar power system will be disconnected if there is a fault, minimizing damage and giving you the opportunity to get technical support.
5. Optional Component: Home Battery System
Home battery systems like the Tesla Powerwall are becoming very popular, since they can store solar electricity for the night. Many batteries are also capable of providing backup power during blackouts, which means you don’t need a diesel generator.
Unlike the components described above, having an energy storage system is optional. However, if you don’t have one, you only have solar power during the day and are fully dependent on the grid at night. On the other hand, a battery system makes it possible to use solar energy 24/7, leaving the grid only as backup.
Being a DC device, a home battery needs an inverter just like solar panels, and you have two main options:
- Installing a dedicated battery inverter, which operates independently from the inverter connected to the solar panels.
- Using a hybrid inverter, which can manage solar panels and batteries simultaneously.
A battery inverter is normally recommended when you want to add energy storage to an existing home solar system, and the inverter is not compatible with batteries. In this case, the battery inverter lets you add energy storage without modifying the system.
On the other hand, if you plan to install solar panels and batteries together, a hybrid inverter is the recommended option. There is no need to install two separate inverters, and batteries can charge and discharge more efficiently.
A hybrid inverter is also recommended if you want to install solar panels now and are considering energy storage in the near future. Hybrid inverters are normally designed to operate as traditional string inverters when no batteries are connected.
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