RenewSolar has been hands on solar testing for almost 20 years, but many people are confused when it comes to solar and how it works or can work. Solar panels are just one part of a solar installation which makes a solar system for your home, so lets look at solar and what you may need to have.
Zero Solar panels.
You can have no solar panels at all. yes that may seem odd but you can store power either from a renewable supplier (wind and solar) or from low rate power providers which you can use with storage and an inverter.
This ( above image) is a 40kwh solar installation without solar panels and a 8kw inverter. You can charge the battery at rates between £0.04 and £0.08 giving you a bill of just £1.60 per day if you use 40kwh of power per day. That’s a saving of £8.00 per day! and a ROI of around just 2.2 years.
Solar Charge vs Solar power.
Depending on what system you have, your solar requirements can be very different. If you have a grid tied system, which has no battery, you would want a smaller solar system, unless you intended to have export payments. These are typically not worth the cost of export payment administration and the money you are paid unless you have a very large solar installation.
For the most part you would need to plan your solar to charge the battery and provide power to the loads while doing so.
The difference with a battery system and a plain grid tied system is that is that the battery system needs to support the charging where as the grid tied only needs to support the load during sun hours
Power.
We are aware that you use kWh ( killo watt hours) of power over the day, however this is a unit of measure and does not relate to power use. lets say we just have a kettle, we will use 0.333kWh of power units but you will use the power at 2.2kw(h). In the next part we will see how this relates to your inverter selection.
Inverter power.
The inverter within a solar installation is what converts the power from solar or a battery into AC power that runs in the wires of your home and the grid. They come in various power out puts measured in kW (killowatts) for most of the time, homes were installed with 3.6kW inverters, which for the most part will cover hovers, kettles, lights and cookers power demands. however certain combinations would exceed what power the inverter can provide, thus some of the power has to come from the grid.
It is fairly common to see 5-6kW inverters in homes these days, and the next level is 8-16kW.
The larger installed inverters mean that most of the power comes from the inverter more of the time rather than the grid, which can be costly over time. The best time to see what your peak load power is, is around tea time, showers, heating, cooking and tv along with some lights and the phone charger will add up to give you a peak load, which you can meet with your solar inverter to how much you would want that to be “green energy” you made with your solar panels.
Solar charging.
England is a feast and famine solar country, with 10 hours in summer and 1 in winter. it will be a matter of grid charging battery’s in winter or around 29 days of the year if you want to run from the battery and off set power. This is key time to look into cheap rate power.
The solar array needs to be sized to charge the battery in 6 hours or more so 4 hours.
I will use 5 hours as its in the middle here. So 10kwh/5 = 2kw. This will only charge the battery, but you will also be using power, and you also need to add 5% because there are system losses converting the power. Lets add 250wh of load, so you would need to have 2.362kw of solar as a peak, however when we do the installations math we reduce the solar array by 35% to give a more average rating.
For example a 8 solar panel array, with 425w solar panels STC rating would be accounted as providing 2.21kw. This means that your power range will be around 17.68Kwh per day to 2.26kwh over the year.
Annual power.
The array of 8 panels would provide annual power of 4,862kwh of power, while the average home uses (apparently) 2700kwh per year. so if you are “average” then the system provides more than enough power? No.
As I mention solar is feast and famine, therefore in summer you will make too much power and in winter you will not make enough. Therefore you would grid charge or add a second array to reduce paying the grid for power. Typically these are called Winter arrays as you would not need to use them in summer, unless your paid for export.
Most people tend to use the power when they have split arrays. AC and Hot tubs can be ran from the excess power providing that your inverter can provide for all the loads you demand from it.
As you can see solar installations are tied together and work as part of a whole system. it is key to ensure that the inverter meets most of your needs or all of them. the solar needs to provide power to the load and also charge the battery to keep the system up and running, and in winter you could have a second array or you will grid charge to make up for the short coming. You would also benefit from cheap rate power to do the grid charging.
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Read more about solar kits in our articles
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