Thinking about having your own solar PV system for your building? Here are some Frequently Asked Questions
Solar photovoltaic or PV is the term used for the technology that converts the energy from the sun (directly or indirectly) into usable electrical energy. From the Greek word phos meaning light and volt from the Italian physicist, the renowned inventor of the electrical battery, Alessandro Volta. Interesting, isn’t it?
The solar panels, which are made up of smaller modules called cells, are made from a special material, a semi-conductor that moves electrons (electricity) with a small encouragement from the light energy from the sun. This electricity is direct current (DC) and must be converted to alternating current (AC) to be used in appliances in your house.
Once properly installed, the solar PV panels on your roof can last up to 30 years. With no moving parts, there is very little maintenance on your part other than the occasional wiping of dust which can mostly be taken care of by the rain. Handy.
The daytime energy consumption in buildings such as offices is higher simply due to the fact that people spend their days working there, and make tea, coffee and sometimes lunch there. This is where a sizeable solar PV system is a big advantage. Most commercial buildings can use all if not most of their energy generated on demand instead of paying an electricity supplier for it.
Your solar PV system will keep converting away any energy it gets from the sun – even when it’s not shining directly on it. We call that daylight energy. The excess energy that is not used immediately is exported to the national grid from which you get your conventional electricity for about €0.19 per kWh. Currently in Ireland, unlike other countries, you’re not getting any money in exchange. This is called Feed-in tariff (FIT).
So, unless you are at home during the day, using appliances such as your kettle, the energy is only being used by your ‘always on’ appliances such as your fridge, etc. However you can store energy using a battery.
Since the electricity from the sun through the solar panels must be used as it’s generated, an electrical load (an appliance) must consume the electricity or it goes back to the grid. But you can keep more power for yourself if you have a battery. No, not the double A kind, a much larger battery to store the energy so that you can use that later on when you come home. Less export to the grid.
By today’s prices they are not as expensive as they used to be. In fact, the cost is reduced to the point that it makes economic sense to get one with your solar PV system. You can learn more about battery storage here.
As a matter of fact, yes you can. How about heating your immersion tank and keeping it hot during the day? Most houses have immersion heaters, why not use renewable energy to keep it topped up? Why is that a good idea? Well, to heat an immersion tank (120 litres) takes 2.5 hours from a cold start. Wouldn’t you like to have a bath or a shower when you get home without having to wait?
Ok, true but it’ll cost you €1.30 a day. Ah sure but that’s nothing. Really? That’s €475.00 per year. After 5 years, when your system has paid itself back, that can be handy holiday pocket money or pay for your kids’ books!
By using these nifty devices called solar diverters also known as PV optimisers. Instead of exporting your excess energy to the grid, from which you make no money, during the day you can keep your immersion heated.
A very good question to which there is a good answer. The appliances in your home do indeed have electrical power ratings in order to work as per their design. Too much or too little power and they simply will not work; it might even break them. Your immersion heater, however, is a heating element meaning it’s a resistive load. Whether your excess is 70W or 1kW, the electricity is there to convert it to heat energy. Some diverters are even smart enough not to call on grid power to supplement the electricity required to meet the 3kW immersion heater rating. Clever isn’t it? We can install these solar diverters with your new or existing solar PV system.
The economics is simple enough, the electricity you don’t buy from a supplier goes toward paying off your solar panels. Typically, this is 5 to 6 years, or if you’re smart about your usage, even less. Also, the Government offers SEAI grants to homeowners for installing solar PV panels on their roofs. So, that’s even less capital from you, quicker payback period and after that, savings!