How Does A Pv System Work?

A photovoltaic (PV) solar system converts sunlight into electricity. It consists of solar panels, inverters, racking, wiring, safety features, monitoring, and often batteries. PV systems range from small rooftop systems that power a home or business up to utility-scale systems that can produce hundreds of megawatts.

The first modern silicon PV cell was developed in 1954, ushering in the era of solar electricity. But PV systems did not become widely used until the 1990s and 2000s as costs came down. Today over 100 gigawatts of solar PV capacity is installed worldwide.

The main components of a PV system include:

Solar panels – Convert sunlight into DC electricity.
Inverters – Convert DC electricity from panels into AC electricity.
Racking – Holds solar panels and connects them to the building.

Wiring – Carries electricity through the system.
Safety features – Allow safe operation.
Monitoring – Tracks system performance.

Batteries – Stores electricity for use when the sun isn’t shining (for off-grid systems).

Table of Contents

Solar Panels

Solar panels, also known as photovoltaic (PV) panels, are made up of solar cells that convert sunlight into electricity. Solar cells are typically made from monocrystalline silicon or polycrystalline silicon, though thin-film solar cells made from cadmium telluride (CdTe) or copper indium gallium selenide (CIGS) are also used.

Solar cells are wired together and encapsulated between a glass cover and a weatherproof backing to create a complete solar panel. Solar panels come in different sizes and power outputs. Standard residential panels are usually around 65” x 39” in size with power ratings of 250-400 watts.

Solar panels can be configured as grid-tied systems that are connected to the utility grid or off-grid systems for remote locations. For grid-tied systems, multiple solar panels are wired together in series into “strings” to produce higher voltages. The strings are then connected in parallel to increase the amperage of the system. The solar array is connected via cables to an inverter and then interfaced with the electric grid.

The efficiency of a solar panel indicates what percentage of sunlight is converted to electricity. Mono- and polycrystalline silicon panels typically have 15-22% efficiency. CdTe thin film is around 16-21% efficient, while CIGS thin film is 12-19% efficient. More efficient panels will produce more electricity for a given surface area.

Inverters

The inverter is a critical component of any photovoltaic system. Its function is to convert the direct current (DC) electricity generated by the solar panels into alternating current (AC) electricity that can be used to power homes and businesses or fed back into the utility grid.

There are several types of inverters used in PV systems:

String inverters: These are the most common type of inverter used in residential solar arrays. Multiple solar panels are connected in series into “strings” and then connected to a single string inverter.
Microinverters: Instead of one central inverter, microinverters are small inverters attached to each individual solar panel. This allows for panel-level monitoring and optimization.

Power optimizers: These are DC/DC converters attached to each panel that “optimize” the output before sending power to a central inverter.
Central or utility-scale inverters: Large inverters designed to handle hundreds of thousands of watts of power from massive solar arrays.

Inverters play a critical role in ensuring PV system performance and safety. Their advanced digital monitoring and optimization capabilities are one of the key innovations that make solar energy viable today.

Racking

The racking in a PV system holds the solar panels in place and angles them towards the sun to maximize energy production. Racking needs to be strong and durable to withstand years of exposure to the elements.

For residential rooftop systems, racking is mounted directly onto the roof. The racking is usually made of aluminum and attaches securely using lag bolts into the roof’s rafters. Rooftop systems must be designed to handle strong winds and potential seismic activity.

Large scale solar farms use ground-mounted racking. The racking is either directly anchored into the ground or attached to concrete footings or ballasts. Ground-based racking allows the panels to be spaced further apart and tilted at an optimal angle.

Proper solar panel racking is a key component in any PV system installation. The racking provides the structural foundation to keep the panels positioned for maximum solar energy production over the system’s lifetime.

Wiring

The wiring in a PV system serves to connect all of the components and safely deliver the electricity generated by the solar panels. There are a few key considerations when selecting wiring for a PV system:

Wire Types/Ratings

PV systems typically use copper wire that can withstand outdoor environments. Common wire types include:

PV wire – Insulated copper wire specifically designed for PV systems. Rated for wet environments and UV resistance.
UF cable – Underground feeder cable. Useful for buried wire runs.
THHN and THWN-2 – Standard wire types suitable for conduit runs.

USE-2 and RHH wire – Rated for direct burial without conduit.

Wires are also rated by temperature (60°C, 75°C, 90°C) which determines the maximum ampacity. Higher temperature ratings allow for higher power capacity. The ratings must align with the connected devices.

Circuit Configurations

PV circuits are typically wired in a series parallel configuration to deliver the proper voltage and current. Panels are connected in series strings to produce a higher voltage while the strings are then connected in parallel to increase the output amperage.

The final home run circuits from the panels and inverters are also sized based on the length of the run and the ampacity rating of the wires. This ensures power losses are minimized across the circuits.

Safety Features

Installing a PV system introduces electrical hazards, so safety features are critical. Two key safety components are disconnect switches and surge protection.

Disconnect Switches

Disconnect switches allow emergency responders and maintenance personnel to cut off electricity flow from solar panels. They are typically located near the main service panel. Most jurisdictions require a visible, lockable, labeled AC and DC disconnect switch.

Surge Protection

Surge protectors safeguard electronics from unexpected spikes in voltage. They are installed on both the DC and AC sides of the system. On the DC side, they protect components like inverters and optimizers. On the AC side, they prevent damage to appliances and electronics in the home.

Properly installed safety features reduce the risk of electric shocks, fires, and equipment damage. They are a critical part of a safe, reliable PV system.

Monitoring

Monitoring is an important part of any PV system installation. There are several key aspects of monitoring to consider:

Production monitoring – Most PV systems have production monitoring capabilities to track how much electricity the system is producing. This allows homeowners and installers to ensure the system is performing as expected. Data on solar production can be viewed through a web portal or phone app.

Remote access – With remote monitoring, homeowners can access real-time data on system production and status from anywhere. This allows issues to be identified quickly if production drops or a component fails.

Alerts – Many monitoring platforms have automated alerts that can notify homeowners and installers if an issue occurs. For example, if a component failure caused production to drop, an instant alert could be sent to initiate repairs.

Batteries

Batteries can be included in PV systems to provide backup power when the grid goes down. They also allow solar panel owners to store excess solar energy produced during the day for use at night. This increases self-consumption from the PV system and reduces reliance on the grid.

The most common batteries used in solar PV systems are lithium-ion batteries, which have become much more affordable in recent years. These batteries have high energy density, long lifespans, and maintain performance even after thousands of charge/discharge cycles. Other battery types like lead-acid may be used, but lithium-ion offers the best combination of performance, lifespan and cost.

Batteries connect to the PV system via a battery inverter or charge controller. These regulate the flow of energy between the solar panels, battery bank, and household loads. They prevent overcharging and also supply power from the batteries when solar production is insufficient.

Adding energy storage allows homeowners to take advantage of time-of-use electricity rates by storing solar energy during the day and using it in the evening when rates are highest. For off-grid solar owners, batteries are a necessary component to provide power 24/7. While batteries do add cost, they enable PV systems to provide backup power and maximize solar energy usage.

Grid-tied vs Off-grid Systems

The main difference between grid-tied versus off-grid PV systems is whether they connect to the utility grid. Grid-tied systems tie into the electrical grid and feed excess solar energy back into the grid. Off-grid systems operate independently of the utility grid and require batteries for energy storage.

Some of the key advantages of grid-tied PV:

Excess solar can be sold back to the utility
No need to buy batteries for storage
Simpler system and installation

Eligible for incentives like net metering

Some of the key advantages of off-grid PV:

Provides backup power during grid outages

Reduced reliance on utility company
May work in remote locations without grid access
Can be expanded for increased energy needs

In summary, grid-tied systems are simpler and good for net metering or selling back excess solar, while off-grid systems provide energy independence and backup power but require batteries.

Conclusion

In summary, a PV system is made up of several key components that work together to harness the sun’s energy and convert it into usable electricity. The main components are the solar panels, inverters, racking, wiring, safety features, monitoring, and batteries.

Solar panels contain photovoltaic cells that convert sunlight into DC electricity. Inverters then convert the DC output into AC electricity that can be used to power your home. Racking securely mounts the solar panels, while wiring connects the components. Safety features like surge protection and disconnect switches safeguard the system. Monitoring provides data on how much energy the system is producing.

For off-grid systems, batteries store excess electricity for use when the sun isn’t shining. Grid-tied systems don’t require batteries since they are connected to the utility grid. The many benefits of PV solar include reducing your environmental impact, lowering your electricity bills, and even earning money by selling excess electricity back to the grid.

Overall, PV solar harnesses the sun’s abundant renewable energy to generate clean electricity for homes and businesses in a sustainable manner. The components work together seamlessly to produce affordable and reliable power from the sun.