Photovoltaic system

A photovoltaic system, also called a PV system or solar power system, is an electric power system designed to supply usable solar power by means of photovoltaics. It uses several components to turn sunlight into electricity. The main parts include solar panels that absorb sunlight and convert it into electricity, a solar inverter that changes this electricity from direct to alternating current, and other parts like mounting, cabling, and electrical accessories to make the system work.

Photovoltaic systems are different from other solar technologies, such as concentrated solar power or solar thermal, which are used for heating and cooling. A solar array only refers to the solar panels themselves, not all the other hardware needed for the system, which is called the balance of system (BOS). These systems can be small, like those on rooftops or buildings, or very large, like utility-scale power stations.

PV systems work quietly and without moving parts or causing air pollution. They have grown from special uses to become a common way to make electricity. Because of this growth, the cost of PV systems has gone down a lot since they were first introduced, though prices still change depending on the market and size of the system. Today, the solar panels themselves are only a part of the total cost, with the rest going to other components and expenses like installation and permits.^: 14

Modern system

Overview

A photovoltaic system, also called a solar power system, turns sunlight into electricity. It includes solar panels that capture sunlight, a device called an inverter that changes the electricity into a form we can use in homes, and other parts that connect everything together.

These systems can be set up in different ways. Some connect to the electricity grid, while others work on their own. They can be placed on rooftops, in fields, or even on buildings as part of the design. Most solar panels are made from a material called crystalline silicon, which helps turn sunlight into power.

Solar grid-connection

Main article: Grid-connected photovoltaic power system

Schematics of an AC coupled residential PV system

When a solar system is connected to the electricity grid, it can send extra power back to the grid for others to use. This is called “feeding energy into the grid.” These systems can be small, like those on homes, or very large, like solar power stations that power many homes. To connect to the grid, the system uses a special device called an inverter to change the electricity from direct current (DC) to alternating current (AC), which is what our homes use.

Scale of system

Photovoltaic systems come in different sizes. Small ones fit on rooftops and can power a single home. Bigger ones, called utility-scale systems, are placed in fields and can power many homes. Even though small rooftop systems are common, there is a growing trend toward larger solar farms, especially in sunny areas where there is more space and less opposition to placing solar panels on the ground.

Utility-scale

Perovo Solar Park in Ukraine

Main article: Photovoltaic power station

Large solar farms are like power stations that use solar panels to create electricity for many people. These farms connect to the electricity grid and can cover big areas, sometimes hundreds of acres, and produce a lot of power—up to hundreds of megawatts. They are often built in places with lots of sunshine.

Rooftop, mobile, and portable

Rooftop system near Boston, US

Main article: Rooftop photovoltaic power station

Small solar systems can power a single home or even small devices like lights on a boat or a tent. They are used on things like satellites, street lights, and electric cars. Rooftop systems were once the most common, but now there is a shift toward larger solar farms, especially in sunny regions where people are more supportive of ground-mounted solar panels. Portable solar systems are also popular for things like recreational vehicles, where they can provide electricity without needing to plug into the grid.

Building-integrated

Main article: Building-integrated photovoltaics

In cities and towns, solar panels are often placed on rooftops to help power buildings. Sometimes, the extra electricity made by these panels can be sold back to the power company. Some companies even put solar panels on things like telephone poles or create “solar trees” that look like real trees but also provide light at night.

Components

A photovoltaic system, also called a PV system or solar power system, is designed to supply usable solar power. It includes solar panels that absorb and convert sunlight into electricity, a solar inverter that changes this electricity from direct current to alternating current, and other parts like wiring and supports to make the system work.

Solar panels are made of solar cells, which are the building blocks that turn sunlight into electricity. These cells are put together in modules, and many modules form a solar array. The array usually connects to an inverter to change the electricity into a form that can power homes and businesses. Sometimes, extra parts like trackers that follow the sun or batteries that store energy are added to make the system work better.

Inverter/Converter market in 2019
Type	Power	Efficiency^(a)	Market Share^(b)	Remarks
String inverter	up to 150 kW_p^(c)	98%	61.6%	Cost^(b) €0.05-0.17 per watt-peak. Easy to replace.
Central inverter	above 80 kW_p	98.5%	36.7%	€0.04 per watt-peak. High reliability. Often sold along with a service contract.
Micro-inverter	module power range	90–97%	1.7%	€0.29 per watt-peak. Ease-of-replacement concerns.
DC/DC converter (Power optimizer)	module power range	99.5%	5.1%	€0.08 per watt-peak. Ease-of-replacement concerns. Inverter is still needed.
Source: data by IHS Markit 2020, remarks by Fraunhofer ISE 2020, from: Photovoltaics Report 2020, p. 39, PDF Notes: ^(a)best efficiencies displayed, ^(b)market-share and cost per watt are estimated, ^(c)kW_p = kilowatt-peak, ^(d) Total Market Share is greater than 100% because DC/DC converters are required to be paired with string inverters

Other systems

This section talks about special and new types of solar power systems. Standalone or off-grid systems were very common in the past when solar technology was expensive. They are used where there is no electricity grid, like in some parts of Australia, South Korea, and many developing countries. Today, they make up a small part of all solar systems.

CPV

Main article: Concentrator photovoltaics

Concentrator photovoltaics (CPV) uses special lenses or mirrors to focus sunlight onto small, efficient solar cells. These systems can sometimes use trackers to follow the sun and may need cooling. They work best in places with lots of sunlight, where they can focus the sun's energy up to 400 times. While some designs exist, they are not very common yet, but researchers are still working on improving them.

Hybrid

A hybrid system mixes solar power with other energy sources, like diesel generators or biogas. These systems can adjust their power output based on demand and are often found on islands. For example, islands like Pellworm in Germany and Kythnos in Greece use a mix of solar and wind power, which has helped reduce the need for diesel fuel. Studies show that combining solar with other energy sources can lower costs, especially for certain types of power plants.

Standalone

Main article: Applications of photovoltaics

A standalone solar system is not connected to the main electricity grid. These systems can power anything from small devices like wristwatches to large buildings or even spacecraft. To store energy for times when the sun isn’t shining, batteries are used. In buildings, lead acid batteries are common because they are affordable and can handle some rough treatment. Some systems use a device called a charge controller to protect the batteries and get the most power from the solar panels. In very small devices, only direct current (DC) is needed, but larger systems usually need alternating current (AC), which requires an inverter to change the power from DC to AC. In places without a grid, like remote islands or mountains, standalone solar systems can be the only source of electricity.

Costs and economy

Learning curve

When we build more solar farms, the cost to make electricity goes down. For every time we double the amount of solar power we have, the cost drops by about one-third. This is called the learning curve.

Cost of generated kilowatt-hour by a PV system (US¢/kWh)
depending on solar radiation and installation cost during 20 years of operation

Installation
cost in
$ per watt

Insolation annually generated kilowatt-hours per installed kW-capacity (kWh/(kWp•y))

2,400

2,200

2,000

1,800

1,600

1,400

1,200

1,000

800

$0.20

0.8

0.9

1.0

1.1

1.3

1.4

1.7

2.0

2.5

$0.60

2.5

2.7

3.0

3.3

3.8

4.3

5.0

6.0

7.5

$1.00

4.2

4.5

5.0

5.6

6.3

7.1

8.3

10.0

12.5

$1.40

5.8

6.4

7.0

7.8

8.8

10.0

11.7

14.0

17.5

$1.80

7.5

8.2

9.0

10.0

11.3

12.9

15.0

18.0

22.5

$2.20

9.2

10.0

11.0

12.2

13.8

15.7

18.3

22.0

27.5

$2.60

10.8

11.8

13.0

14.4

16.3

18.6

21.7

26.0

32.5

$3.00

12.5

13.6

15.0

16.7

18.8

21.4

25.0

30.0

37.5

$3.40

14.2

15.5

17.0

18.9

21.3

24.3

28.3

34.0

42.5

$3.80

15.8

17.3

19.0

21.1

23.8

27.1

31.7

38.0

47.5

$4.20

17.5

19.1

21.0

23.3

26.3

30.0

35.0

42.0

52.5

$4.60

19.2

20.9

23.0

25.6

28.8

32.9

38.3

46.0

57.5

$5.00

20.8

22.7

25.0

27.8

31.3

35.7

41.7

50.0

62.5

USA

Japan

Germany

Small rooftop system cost and average insolation applied to data table in 2013

Notes:

Cost per watt for rooftop system in 2013: Japan $4.64, United States $4.92, and Germany $2.05

Generated kilowatt-hour per installed watt-peak, based on average insolation for Japan (1500 kWh/m²/year), United States (5.0 to 5.5 kWh/m²/day), and Germany (1000 to 1200 kWh/m²/year).

A 2013 study by the Fraunhofer ISE concludes LCOE cost for a small PV system to be $0.16 (€0.12) rather than $0.22 per kilowatt-hour as shown in table (Germany).

Regulation

Photovoltaic systems, which use sunlight to make electricity, need rules to make sure they are safe and work well. Groups like the International Electrotechnical Commission make standards for how these systems should be built and used.

In the United Kingdom, most solar panel setups do not need special permission, but there are some places where permission is needed. All setups must follow building rules to keep everyone safe.

In the United States, local laws decide how solar panels can be set up. Usually, a permit is needed, and the work must be done by a licensed electrician. The local authority checks the plans before work starts to make sure everything is safe.

Spain once had special taxes on solar energy, but these were removed in 2018, allowing people to use solar power without extra taxes.

Limitations

As more homes install solar panels, the way electricity flows changes. Sometimes, homes make more electricity than they use and send it back to the power lines. But old power systems weren’t built for this, which can cause problems like too much power on the lines. Places like Queensland, Australia, and California have seen this happen a lot.

People who use solar power have different needs and face different electricity prices. Solar power can help save money when electricity prices are high, but it might not help as much if the biggest use of power happens later in the day. Deciding whether to invest in solar power depends on many factors, including saving money and using energy better.

Grid-connected photovoltaic system

A grid-connected photovoltaic system, or grid-connected PV system, is a solar power system that connects to the electricity grid to provide power. It includes solar panels that capture sunlight, one or more inverters that change the power into a form the grid can use, and other equipment to link to the grid. These systems can be small, like those on homes or businesses, or very large solar power stations. When there is enough sunlight, these systems can send extra power to the grid for others to use.

Operation

Residential rooftop systems that are bigger than 10 kilowatts can provide enough power for most homes. Any extra power made can be sent to the grid for others to use. A meter keeps track of how much power is shared.

If the solar panels make more power than a home needs, the extra can be sold to the grid for money. This depends on the agreement with the local grid company. The home owner only pays for the electricity they use, minus what the solar panels make. If the panels make more than is used, the bill might even be negative. Connecting a solar power system requires an agreement with the utility company to make sure everything is safe.

Features

A photovoltaic system turns sunlight into electricity using special panels. To use this electricity in homes or on the power grid, it needs to be changed from direct current to alternating current by a device called a power inverter. The inverter sits between the solar panels and the grid. It can be one big unit or many small ones attached to each panel.

The inverter watches the power grid’s voltage, shape, and frequency to make sure everything works safely. If the grid stops working, the inverter stops sending power to it. This keeps the system safe and makes sure the electricity flows correctly into the grid.

Advantages

Some special programs like Net Metering and Feed-in Tariff can help people save money on their electricity bills by using solar power. These programs work with the electricity grid to make it easier to use solar energy without needing extra batteries.

Solar power systems help reduce the use of fuels that hurt the environment. Even when the sun isn’t shining, these systems still cut down on the amount of pollution made from regular power sources.

Disadvantages

Grid-connected solar power systems can sometimes cause problems with electricity flow. When too much solar power is added to the regular electricity grid, it can raise the voltage to levels that are not safe or comfortable for normal use.

Solar power also changes quickly as the sun moves or clouds pass, which can make the electricity quality less steady. This quick changing can strain the equipment that keeps voltage at the right level and can cause flickering lights.

Islanding

Main article: Islanding

Islanding happens when a small power source, like solar panels, keeps supplying power even when the main electricity grid stops working. This can be risky for workers who might not know the area still has power. To keep everyone safe, these small power systems are designed to stop working right away when the grid goes down. This safety step is called anti-islanding.

When the grid stops working, solar panels can still make power if the sun is shining. Special devices called solar inverters help make sure this power doesn’t stay on safely. Sometimes, these systems can be set to work on their own as a backup power source for buildings. There are different ways to make sure these systems stop safely, using changes in voltage or frequency to ensure they turn off when needed.