If you want to generate electricity from light using solar technology there are a number of factors to consider.
Solar panels explained
The term ‘solar panel’ is often used interchangeably to describe the panels that generate electricity and those that generate hot water.
- Solar panels that produce hot water are known as solar thermal collectors or solar hot water collectors.
- Solar panels that produce electricity are known as solar photovoltaic (PV) modules. These panels generate DC electricity when exposed to light.
This page focuses on those technologies that generate electricity from light.
Solar electricity technologies
There are two broad groups of technologies which generate electricity from light. Of these, solar PV technologies are best suited for use in Ireland.
Solar photovoltaics (solar PV)
These are the most common solar technologies worldwide. They are also the fastest growing in terms of installed capacity.
Concentrated Solar Power (CSP)
These technologies produce electricity by focussing sunlight to produce heat and drive an engine connected to an electrical generator. They are currently found in countries with year round sunshine.
How Solar PV works
Certain semiconductor materials generate electricity when exposed to visible light. These are called Photovoltaic (PV) materials.
Solar PV technologies use a wide variety of semiconductor materials. The most common to date are those using silicon as the photovoltaic material. However, technologies based on other semiconductor materials are growing their market share.
Solar PV products
Solar PV products exist for a range of different applications. These include:
- Solar panels or modules. These are the best known solar PV products. Now a familiar site on rooftops and in ‘solar farms’ they have been mass manufactured for over 25 years.
- Building Integrated Photovoltaics (BIPV). These are building material products such as roof tiles, glass or cladding with solar PV materials embedded within them.
- Consumer electronics. Some consumer products have been developed with solar PV materials integrated into them so that they can produce their own power.
A big share of your annual electricity needs
Conventional solar PV panels will help meet some of the electricity demands of a building.
- 1 sq. m of silicon solar panels will generate ~150W of power on a clear sunny day. That’s enough to power a laptop computer.
- A home solar PV system sized at 20 sq. m (~3kW) and well located would generate around 2,600kWh of electricity a year. That is over 40% of the average annual electricity demand of an Irish home.
- Solar PV systems will still function on overcast days in Ireland although not at their maximum rated capacity.
Factors that affect electricity production
The amount of electricity a solar panel will generate depends on a range of factors. These include:
- The hardware chosen
- The size of the system
- The geographical location
- The direction in which the panels are installed
Invest in a Solar PV System
There are some important things to consider before investing in a solar PV system for your community, home, or business.
Find the right installer
Finding a competent installer is important. There are currently no formal qualifications that installers must have. However do note the following:
- Connection of the solar system must be carried out by a Registered Electrical Contractor.
- The Renewable Installers Register identifies installers who have received accredited training.
Our advice would be to get a range of quotes from installers, including contractors listed on the Renewable Installers Register.
Choose the right equipment
Speak to your installer about the products they offer. Solar PV systems will usually include:
- Solar modules
- An inverter, which converts electricity from direct current (DC) to alternating current (AC)
- A mounting system for the roof or ground
- Some installers also offer battery systems or 'diverter switches' for storing excess energy
Check the Triple E Register for solar PV products that meet a minimum performance criteria, including energy efficiency.
Check planning permission
Solar PV systems installed in a domestic setting that are under 12 sq. m (and represent less than 50% of the total roof area) are exempt from planning. The same exemption applies to solar PV systems in a business or industrial setting that are under 50 sq. m.
Larger solar PV systems in homes and businesses will typically require planning permission. We recommend you speak with your local planning authority to understand the requirements.
The cost of purchasing and installing solar panels has reduced dramatically in the last decade. As a rough guide Solar PV systems for the home should range from around €1,500 - €2,000 per kW installed (ex-VAT). The cost will vary depending on the hardware, size of system, accessibility of the roof or site, and the installer used.
How can I maximise the amount of solar electricity generated that I use?
The simplest way to use a higher percentage of the electricity generated is to design the PV system to meet the average daily electricity demand of the house, although this may mean a very small PV system is installed if demand is low during the daytime.
Another simple measure is to install a ‘diverter switch’ which diverts any unused electricity to heat your hot water in your immersion tank. In this way some of the energy generated is stored as hot water, which you can use later.
Finally, a more complicated option is to install a PV system which does not face south, but faces west or east. This will provide more energy in the morning or the evening when you have a greater demand to use it. However, an east- or west-facing PV system will generate less energy over the year than a south-facing system
What about a battery storage system?
Adding a battery to your solar PV system means the battery will charge when the PV system is generating electricity which isn’t being used, and then discharge when you need it next (normally that evening/night). A battery can increase the percentage of solar PV electricity you use in your house. Adding a battery to the system will increase the cost of the PV system and some energy will be lost in the battery during the charge and discharge cycle.
Is there a ‘feed-in tariff’ payment for excess solar electricity fed into the grid by owners of solar PV systems?
Does a rooftop PV system require maintenance?
PV systems are low-maintenance, but not zero maintenance. The most important aspect is to monitor the performance of your system regularly. This could simply be a routine check of your inverter to see that the system is operational and that the energy meter is increasing each day.
You should get an idea from your installer about how much the PV system should generate each year, and see that your system is generating close to that amount. Some suppliers will provide you with access to this information via your smartphone. The most common point of failure is the inverter, which may need to be replaced at some point in the PV system’s lifetime.
The solar panels themselves are extremely robust, but consideration should be given to cleaning them every few years to maintain their performance. If you live near the sea or a main road more regular cleaning may be necessary.