What are photovoltaic systems?

Photovoltaic technology works by converting the sun’s energy into electricity. A photovoltaic cell, also referred to as a solar cell, uses semiconducting materials such as silicon to convert light into electricity – this is what’s known as the photovoltaic effect. 

In our jargon-free guide to photovoltaic systems, our experts delve into how the technology works and the system’s components and compare different types of solar panels and their benefits.

A photovoltaic system is a system that generates renewable energy via photovoltaic cells and then converts it into usable electricity. Photovoltaic systems consist of one or more solar PV panel along with an inverter.

Step-by-step guide to how photovoltaic systems work: 

1. Solar cells use a semiconductor material – usually silicon – to collect solar energy from the sun’s rays. 
2. The collected energy produces an electrical charge, which releases an electric current known as direct current (DC). 
3. DC electricity is converted into alternating current (AC) via the photovoltaic system’s inverter. 
4. AC electricity can be used to power home appliances or stored in a solar battery for later use.  

Two forms of energy can be generated via solar panels – electricity and heat. Solar PV systems work as described above. Solar thermal systems, meanwhile, convert sunlight into heat, and hybrid systems use PV materials, with electricity routed to a hybrid inverter and solar battery. 

What is the difference between solar panels and photovoltaic systems?

This is where solar panel terminology can become confusing. Solar panel is a general term that often refers to photovoltaic systems and solar panels – but you should know that while all PV systems are solar panels, not all solar panels use PV technology. Here’s the difference: 

Solar PV panels: use the photovoltaic effect. Electricity is generated when a photon makes contact with its semiconductor surface to release an electrical charge known as direct current (DC).  

Solar thermal panels: also known as solar thermal collectors, these are roof-mounted just like solar PV panels. This type of panel turns solar energy into heat instead of power. They collect sunlight to heat a liquid running through the panels – usually a mixture of water and antifreeze. The heated water is sent to the heat exchanger inside your water tank, and the exchanger then heats the water. The heat is then released for space and water heating. The water flows back to the thermal collectors for reheating.

Photovoltaic systems typically consist of several components, some of which are crucial to the inner workings of the system, while others are optional. 

Solar array

A photovoltaic system consists of multiple solar panels, which are connected to form a solar array. PV systems are typically mounted to your roof using brackets that are secured via bolts. Your solar array must be mounted at an optimal angle to maximise sunlight exposure – 30 to 35 degrees is the desired angle. 

Your solar panel’s photovoltaic cells collect sunlight, which is then converted into DC electricity.   

Inverter

An inverter is a crucial component within a photovoltaic system. As previously mentioned, solar panels collect sunlight and convert this into DC. An inverter’s role is to convert electricity from DC to AC, which is needed to power your home’s electrical appliances.    

Battery bank

A battery bank stores unused energy generated from your solar panels. This optional component allows homeowners to save more money on their energy bills. Also known as solar batteries, a battery bank can store excess electricity to power your home during the evening or on cloudy days when your panels are generating less or no electricity. Though its money-saving capabilities are desirable, battery banks are costly. 

Charge controller

This component is only necessary if you have installed a solar battery. For those who have, it’s what controls the DC from your solar panels, ensuring your batteries don’t overcharge – which can cause permanent damage – by stopping the flow of current. Charge controllers can regulate and monitor energy. .  

Utility meter

All households have a utility meter. Its purpose is to measure your energy consumption. Your utility meter will be connected to your photovoltaic system at the point of installation and measure your energy consumption as well as your system’s energy generation – if you have not installed a battery, the surplus is fed back to the electric grid, and you’re usually paid for this through the Smart Export Guarantee (SEG) scheme. 

Electric grid 

Most UK homes are connected to the electric grid. Living off-grid means you’ll rely solely on the renewable energy generated by your solar panels – which isn’t a reality for most. To do this, you’d need to store enough electricity in your solar batteries to power your home 24/7. 

For those not off-grid, your surplus electricity is fed back to the grid. Similarly, if your battery is full, the excess electricity will also feed back to the electric grid.

Installing a solar panel array can reduce your carbon footprint and lower your energy bills. While these are both desired outcomes, the benefits you receive will depend on the type of solar panels you choose. 

Solar panels vs solar tiles

Both solar panels and solar tiles work in the same way – collecting the sun’s energy via photovoltaic cells for it to be converted into usable electricity. The differences between the two are mostly to do with panel efficiency, which can drastically affect the overall performance of your solar array. 

Solar panels vs thermal collectors 

Solar PV panels work by collecting the sun’s rays and converting them into electricity to power your home. Thermal collectors are used to generate heat, rather than power, that can be used to heat homes and water.  

Types of solar systems compared

Photovoltaic systems generate electricity to power homes and commercial buildings. With technological advancements, some solar panels now have an efficiency surpassing 20 per cent. This means the solar panel can convert 20 per cent of the sun’s energy into usable electricity. 

However, regardless of efficiency, roof pitch, orientation and cell type will also affect your solar array’s performance. 

Roof pitch 

For your solar panels to maximise sunlight hours, they should be pitched between 30 and 40 degrees. Research suggests this is the optimal angle to maximise sunlight exposure. As a general rule of thumb, the more sunlight your panels receive, the more electricity they can generate. 

Orientation

Though there is little you can do to change this, the orientation of your roof directly affects system performance. It has been proven that solar panels in the UK that are south facing collect the most sunlight. 

Solar panel type 

There are three main types of solar panels – monocrystalline, polycrystalline and thin-film solar panels.

• Monocrystalline: cells are made from a single silicon crystal – the highest grade – and the most efficient type of the three panels at around 20 per cent or more    
• Polycrystalline: cells are formed from multiple silicon fragments melted together. While not as efficient as monocrystalline, with just a 13 per cent efficiency rating, they are cheaper to make and therefore cheaper to purchase 
• Thin-film:  made from a thin film of silicon transferred onto glass – their efficiency is around 7 per cent. They’re the cheapest of the three types of panels. They’re not recommended for homes where space is limited due to their low efficiency 

Although generally speaking the best angle for solar panels is between 30 and 40 degrees, there is a slight variation between seasons and locations within the UK. According to Solarific’s data, these are the most efficient angles for different UK locations, whether you can change your solar panels’ tilt each season or have to choose a fixed position.