Photovoltaic system

A photovoltaic system, also called a PV system or solar power system, is an electric power system that uses sunlight to make electricity. It has several parts that work together.

The main parts are solar panels that catch sunlight and turn it into electricity. A solar inverter changes this electricity from direct to alternating current. Other parts, like mounting, cabling, and electrical pieces, help the system work.

Photovoltaic systems are different from other solar technologies, such as concentrated solar power or solar thermal. A solar array means just the solar panels, not all the other parts needed for the system. These other parts are called the balance of system (BOS). PV systems can be small, like on rooftops, or very large, like utility-scale power stations.

PV systems work quietly and do not need moving parts or cause air pollution. They have become a common way to make electricity. Because of this, the cost of PV systems has gone down a lot since they were first made. Today, solar panels are just one part of the total cost. Other costs include things like installation and permits.^: 14

Modern system

Overview

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

These systems can be set up in different ways. Some connect to the electricity grid, while others work alone. They can be placed on rooftops, in fields, or built into buildings. 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 made to give us solar power. It has solar panels that catch sunlight and turn it into electricity. It also has a solar inverter that changes this electricity from direct current to alternating current. Other parts like wires and supports help the system work.

Solar panels are built from solar cells. These cells are the tiny parts that change sunlight into electricity. The cells are grouped together in modules, and many modules make a solar array. The array links to an inverter to change the electricity into a form that can run homes and businesses. Sometimes, extra parts like trackers that move with the sun or batteries that save energy are added to help 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 common 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 use sunlight to make electricity. They need rules to stay safe and work well. Groups like the International Electrotechnical Commission make rules for how to build and use these systems.

In the United Kingdom, most solar panels do not need special permission, but some places do. All setups must follow building rules to keep everyone safe.

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

Spain used to have special taxes on solar energy, but these were removed in 2018. Now people can use solar power without extra taxes.

Limitations

As more homes use solar panels, the way electricity works changes. Sometimes, homes make more electricity than they need and send it back to the power lines. But old power systems were not made for this, which can cause problems like too much power on the lines. Places like Queensland, Australia and California have seen this happen often.

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 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 links to the electricity grid to supply power. It uses solar panels to catch sunlight and one or more inverters to change the power into a form the grid can use. These systems can be small, like those on homes, or very large solar power stations. When there is enough sunlight, they 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 changes 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 is placed between the solar panels and the grid. It can be one large unit or many small ones attached to each panel.

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

Advantages

Special programs like Net Metering and Feed-in Tariff can help people save money on electricity bills by using solar power. These programs work with the electricity grid, so people can 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 pollution 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 is when solar panels keep giving power even if the main electricity grid stops working. This can be dangerous for workers who might not know there is still power. To keep everyone safe, these small power systems are made 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 turns off safely. Sometimes, these systems can be set to work on their own to give backup power to buildings. There are different ways to make sure these systems stop safely by using changes in voltage or frequency.