Solar
Panels

The benefits of solar PV

There are several benefits of switching to solar PV:

• Solar is a renewable energy source which can be harnessed everywhere in the world, every day;
• Using solar energy means you will be reducing your electricity bills. The more solar energy you generate, the less you’ll be paying for electricity;
• Solar energy systems typically don’t require much maintenance, cleaning twice a year should suffice.

Solar panel efficiency

Solar panel efficiency is determined by testing panels at Standard Test Conditions (STC), using a temperature of 25°C and an irradiance of 1,000 W/m² – the equivalent of a sunny day with incident light hitting a sun-facing surface tilted to 37°. A solar panel efficiency of 15% with a 1m² surface area would produce 150 Watts under these test conditions.

How to calculate the performance

If you would like an estimation of how you can expect your solar system to perform over the years, your installer will be able to calculate this using the following method:

• Take into account the direction of the solar panels facing the sun;
• Take into account the angle of the solar panels;
• Take into account any obstacles surrounding the solar panels which are obstructing the line of sight towards the sun;
• Take into account degradation of the solar panels (i.e. panels performance reduce overtime).

The house direction

In the UK, solar panels are most effective when south facing, as this means they will be facing the sun for the majority of the day. Panels facing north will be far less efficient as they will be facing away from the sun.

Slope of roof

The optimal angle of tilt to position solar panels isn’t straightforward. In the UK, the sun is higher in the sky in the summer and lower in winter, meaning that if your panels are pointing at the position of the sun at midday in midsummer, they’ll maximise efficiency over summer but lose out in winter.

In the UK panels that are tilted at 15° or more have the benefit of being cleaned by rainfall to ensure optimal performance.

Shading

Shade is the nemesis of solar panels, capable of having a really adverse influence on their efficiency. It’s important to assess the area that you have earmarked for your panels in order to establish any nearby buildings or vegetation that could cause an issue. Also, due to changes in the angle of the sun, shadows will be in different positions at different times of the day and year. It would be prudent to gauge this over a six month period. 

Will solar panels work during the night?

This simple answer to this is no, as solar panels need sunlight in order to produce energy. However, homes can still be powered at night with the solar energy that has been captured during daylight hours, if the system is linked to a solar storage battery.

Performance during the cold winter

A common misconception is that winter weather will mean lower efficiency. The opposite is often true. Though solar panels are designed to withstand average temperatures, they’re more inclined to function better when they’re cooler. This is true with most electronic equipment. And since solar panels need light (not heat) from the sun, bright winter days can be highly productive. However, as the days are shorter in the winter months, production would be less than in the summer.

How well do solar panels work when dirty?

Significant amounts of dirt and dust can also reduce efficiency. For the most part, solar panels are self-cleaning. A rain shower can clear dirt and dust away, thereby helping your panel regain its efficiency in just a few minutes.

Type of solar inverters for solar panels

Solar inverters play a vital role in any solar installation. Their main function is to convert the captured energy from DC to required AC, but they are also used for monitoring and enabling installers and homeowners to keep an eye on how the system is performing. Inverters are also able to provide diagnostic information to make it easier to identify and fix any issues. There are several different kinds of solar inverters and your installer will be able to advise you which one would best be suited to your project.

• String inverters : Each row of solar panels is installed on a string, with multiple strings connected to one string inverter. Each one of these strings transports the DC power from the solar panel to be converted to AC power by the string inverter.
• Central inverters: While similar in function to string inverters, central inverters are much larger and are capable of a greater number of strings of panels. However, these strings are linked to a combiner box, rather than directly to the inverter. Central inverters are best suited for larger installations.
• Microinverters: These are installed on each individual solar panel and convert DC power to AC at the panel, removing the requirement for a string inverter. This allows each panel to be monitored for performance, and if some panels are in shade then it won’t affect the others.
• Power optimisers: These offer many of the same benefits as microinverters, but tend to be slightly less expensive. Power optimisers are often considered a compromise between more expensive microinverters and the standard string inverter.
• Battery based inverter/chargers: Requiring a battery to operate, these can be off-grid, standalone grid-tied or grid-interactive. Battery based inverter/chargers are capable of providing for continuous operation of critical loads, whatever the condition or presence of the grid.