PV system

Overview

In the following page you will find a simple explanation about how a PV system works and its main components. In this article  electricity is compared with water to have a pictorial understanding of the basics fundamental. Here we will go further with the same analogy to explain a complete PV system.

Introduction

ANALOGY

A solar PV system works similarly to a rainwater collection system.The amount of water collected changes with the weather: there are days with a lot of rain and days with none, therefore some days a lot of water can be collected and others not.

In the same way, the amount of electricity generated by a PV system changes according to the weather. The sunnier it is, the more electricity is produced by a PV system. When it is cloudy, little electricity is generated.

Not only do rainwater collection systems and solar PV systems act much the same, they have similar parts and each part of the rainwater system does a similar job to a part in the PV system.

Role	Rainwater System	PV system
Source	Rain	Sunlight
Collection	Roof	PV module
Control	Valves	Electronics
Storage	Tank	Battery
Transport	Pipes	Wires
Appliances	Shower, Sink, Toilets	Light, fans, mobile phones

Collector

The PV panel collects sunlight and converts it into electricity.

Sometimes it is mounted on a roof, but it can be placed anywhere there is sun.

In a rainwater system the part that does a similar job is the house roof. If you think of electricity as being like water, the solar panel collects sunlight like the roof collects rainwater.

The roof collects water that falls from the sky, so it can be stored for later use. The solar panel collects sunlight that comes from the sky, so it can be stored for later use as electricity.

The larger the surface of the roof, the more water is collected when it rains. The larger the surface of the solar panel, the more electricity will be collected when the sun shines.

If it rains hard, a lot of water is collected in a short time and if it rains lightly, only a small amount is collected in the same time. If the sun shines brightly, a lot of electricity is generated in a short time while if it is cloudy, only a small amount of energy is collected in the same time.

If it does not rain, no water will collected. At night, no solar energy is collected.

Storage

The battery stores energy and promotes electricity when is needed.

Water is needed when it is not raining, and electricity is needed when the sun is not shining. Both a rainwater collection system and a solar PV system must have a storage system. The battery in a PV system has a similar function to the storage tank of a water system.

The storage tank allows the use of water for some time after it stops raining. The battery allows the use of electricity for some time after the sun goes down.

If it rains a lot and no one uses much water, the storage tank fills up to capacity. If the sun shines a lot and there is little use of electricity, then the battery becomes full of electricity.

If water is consumed when there is little rain, the water level in the tank gradually falls and the tank soon empties. If people use electricity when there is little sun, the amount of electricity in the battery gradually falls and soon the battery has no more electricity.

Flow control

Some devices such as charge controller and switches control the electricity flow in a PV system.

Water storage tanks have valves on their inlet and outlet pipes to control the use of water. The taps and showers also use valves, so we can regulate the flow.PV systems have a charge controller, switches, inverters, etc. In this way this “valves” control how much energy, will come in and out of the battery and into the appliances.

Transport

Wires are responsible for making the transport of electric charges.

Both water and electricity must be moved from place to place.

To move water from one place to another, pipes are used.To move electricity from one place to another, wires are used.

Large pipes let water flow more easily than small pipes, so large pipes are needed when large amounts of water are to be moved quickly.Large wires let electricity flow more easily than small wires and are used when large amounts of electricity are to be moved quickly.

If pipes are not joined together correctly, they leak and all the water does not reach the appliance. If wires are not joined together correctly, all the electricity does not reach the appliance where it is needed.

Appliances

Appliances are devices that use electricity to perform a specific task, typically a domestic one.

Various appliances can use water from the rainwater system or electricity from the PV system.

In rainwater collection systems, there is often only one appliance attached to the system: a tap. Some water systems may include other appliances such as flush toilets and showers. Appliances that use a lot of water, such as flush toilets, only work well if connected to a water system that is designed for them. If a flush toilet is attached to a water system designed for a simple water tap, it will probably not work well, and the storage tank may run dry quickly

In PV systems, lights are the most common appliances. However it is also possible to connect other appliances such as radios, televisions, videos, pumps and even refrigerators if the PV system is designed for them.