How Solar PV works and the components of Solar PV Systems
Ireland is one of the newest countries to see a major uptake on the installation of Solar PV panels, with grant aid being launched in November 2018 for Solar PV Panels for houses built before 2011. They are following in the footsteps of countries like Australia, Germany and the UK where they are trying to lower the countries carbon footprint by enticing people with grants to generate their own electricity.
The process of converting sunlight into electricity using PV systems produces zero greenhouse gas emissions.
Excess electricity can be directed into the grid, with feed-in payments due to be finalised during 2021, or it can be stored in a rechargeable battery for later use. Batteries can also provide back-up power in the event of blackouts.
A solar PV and battery system offer the potential of off-grid energy self-sufficiency. It’s also a major step in the transition away from fossil fuels, in Ireland the main off grid solution would be a combination of wind and Solar energy.
The cost of a home solar PV system starts from around €3500 for a basic installation, with SEAI grant aid started from €900 up to €3000 subject to the year your home was built and your energy rating once work is completed. Prices have steadily come down over the past 10 years, as demand and mass-production increase.
Solar PV is intended to be an investment that, once paid for, will save its owner money by generating free electricity during daylight hours.
A PV system for a commercial property would typically have a return on investment between 4-6 years and for a residential property 6-10 years, this is dependent on your usage and the size of the system that is installed. With feed in payments due this year this will make your return on Investment even quicker.
To get a good idea of the potential benefit, use your electricity bills to estimate the amount of electricity you are using annually and from this calculate how much energy your PV Panels will produce and potentially offset.
Plan before buying
A solar PV system is a major long-term investment. The market and technology are rapidly evolving. It is important to consider your habits in the household. If it is possible for you to use your heavy electrical consumption items like washing machine, dishwasher, tumble dryer, oven during the daylight hours. This will help to decide weather battery storage is essential for your home or not.
A range of components and options need to be considered.
A solar PV system powers electrical appliance’s only, so where gas/oil or a stove or fireplace with a back boiler is used for cooking or heating hot water it is worth considering replacing them with electrical alternatives.
For hot water and heating, an electric heat pump system is the most energy efficient way to run your home currently, as long your house is correctly insulated, and the heat pump is set up correctly. If your home is run by a heat pump, by having PV panels they can contribute towards your general electrical consumption as well as the electrical consumption for heating your home and your hot water cylinder.
Find out if the system can be upgraded as technology improves, you may be able to add batteries or more panels over time.
Be aware that there are low-quality solar panels around, as well as ‘deals’ that may not be what they seem.
Feed-in tariff is the rate you are paid by your energy retailer for electricity that you export to the grid.
Feed-in tariffs differ among retailers and are subject to change, these are due in Ireland 2021, it has not been announced yet how much this feed-in tariff will be, but a smart meter will be installed in your home, this will calculate how much excess electricity you have exported to the grid and a credit will put on your bill on the end of each billing period.
SEAI Grants for Residential Properties
SEAI Grants are available on Solar PV Systems retrofitted on houses built prior to 2011. In order to qualify for the grant your home must reach a C3 energy rating after the panels are installed. Typically this would be any house built since the 1970’s that has upgraded there windows to double glazing, upgraded there cavity wall insulation, upgraded there attic insulation and have a relatively efficient heating system. If you are unsure if your house would reach the C3 energy rating it is recommended that you get a pre BER done also to ensure that it will.
Choosing the right panel
Solar panels capture the energy of sunlight which is converted into electricity. This is known as a photovoltaic system, usually called solar PV.
Panels come in a range of different wattages and power levels.
Numerous brands are available, with new technologies and efficiencies frequently emerging. Although solar panels look similar, levels of power, quality and reliability vary greatly.
A fully exposed rooftop with no shading is ideal for solar. Where that’s not available, make sure the panels are installed where they will attract most daylight. PV panels can also be installed ground mounted or on sheds/ garages in close proximity to the home that are ideally connected to the power supply in the home.
There is a standard 12 year product warranty for solar panels in Ireland, as well as a 25 year performance warranty. Be aware that some manufacturers may no longer be in business in 10 or 20 years should you need to make a claim, so be insure you are going with a reputable company using reputable panels.
Solar inverters are an essential component of a solar PV system. They convert the direct current (DC) output of solar panels into alternating current (AC) electricity for use in the home.
Inverters can be monitored via a computer program or device app to check energy generation, consumption and correct operation of the system.
Several types of inverter are suitable for home systems.
The most common type for households, generally ranging from 1.5 to 5kW. They are a single unit connected to a ‘string’ of solar panels. More than one string inverter will be required for larger panel set-ups.
The main shortcoming is if one or more of the connected panels is in shade (even partially) it reduces the output of the entire system. This means the system will always operate at the capacity of the worst performing panel.
For this reason, a fully sun-exposed panel array is ideal for a string inverter set-up.
String inverter warranties are generally 5 to 10 years. Some manufacturers offer extended warranties at additional cost.
These are smaller individual units that are installed on a rack or attached to each panel. They are ideal where regular intermittent shading of panels is unavoidable due to trees or other buildings.
A micro inverter system makes it possible to monitor the performance of each individual panel.
Another advantage is that reduced output from a single panel doesn’t overly affect the output from the entire array. Because there’s no single point of failure, if one inverter or panel fails the rest of the system will continue to generate electricity.
A micro inverter system is significantly more expensive than a string inverter set-up.
Warranties for micro inverters tend to be 10 to 25 years; 10 years when they are racked and 25 years when attached to the panel directly.
Solar Photovoltaic Optimizers help with the performance of your system if you have partial shading, or panels installed on roofs facing different orientations, installing optimizers helps each panel to run at its optimal voltage and current, so the shading on one panel does not affect the entire array as much.
An Immersion Diverters sends your excess electricity via your immersion circuit to heat the water in your hot water cylinder.
Hybrids inverters allow you to add a battery to the system with relative ease. A hybrid inverter can be installed and used before batteries are in place, making it a good option for an expandable system.
Hybrid inverters rather than sending the excess electricity to a water diverter or to the grid, they can read how much is required in the home and send the excess electricity to batteries to be used at a later stage when needed.
Be sure to discuss the options, including future upgrades or expansion possibilities, with your retailer and installer.
Rechargeable solar batteries store the ‘excess’ electricity generated from your solar PV system, boosting your energy capacity and making power available for use at night time, on cloudy days, or when there is a higher demand in the house than the PV panels are generating.
If you have battery storage installed, you can also charge your battery from the grid if you have a night rate meter and then use it during the day when required. This is greatly beneficial during the winter months with shorter days and poorer solar radiance.
Recent design improvements and price drops in lithium-ion batteries have made solar storage more viable than ever before.
Assess your energy needs before investing in a battery or batteries. There is no point buying more capacity than you can use also you may be in a position where you will consume most of the power directly into the home so there will not be enough constant excess electricity to feed the battery.
If all the appliances in your home are electrical, they can be powered by solar.
Cleaning and maintenance
To maintain efficiency, panels will need to be cleaned from time to time. If any components are damaged, always contact a trained professional to inspect your system.