So from the start of October our email inbox fills up with the same questions?
‘I’m not making as much power as last month, Why?’
‘My batteries are not lasting as long, Why?’
‘At night my battery voltage depletes quicker than before, Why?’
This is because making power from Solar from the end of February to the end of September is easy, this is because we have more daytime hours to charge the batteries and the panels are tilted closer to the sun. That is why the season is called ‘Winter’, we think of Winter as cold, snowy, long dark nights… This is because the Earth is tilted further away from the Sun if you live in the Northern Hemisphere.
Things which normally don’t bother you from March to September like the odd dark gloomy day, all of sudden becomes more noticable and as we get closer to the 22nd of December and the Solar Panel Generation plummets. So lets looks at answering some of the questions..
Question 1: Not Making As Much Power?
Solar Panels require photons of light to charge the panel, the less photons the less power is produced. Imagine this, when you stand in front of a fire it is hot, you feel the radiation on your face and body, each step you take back the cooler you feel because the concentration of the radiation is becoming more and more diluted, stand behind a chair and you can’t feel the direct heat at all, but you will still feel the heat in the room.
This is the same with your solar panel, the sun is still there but now it is further away from the Earth reducing the mount of electricity produced by the panel, not only that but now block the sun with clouds and you reduce the electric produced further, now reduce the amount of hours of sunlight and you reduce production even further.
A 400w Solar Panel in the winter will loose 75% on output making it around 100watts (in the sun). Now add some cloud reducing it by another 75% (or More) making it around 25watts and now lets drop the hours of daylight from 17 hours down to 6 hours.
Quick approximate maths:
Summer 400w panel: 400w x 17 hours = 7044watts of power.
Winter 400w panel: 400w / 4 = 100w / 4 = 25w x 6 = 150watts of power.
Can you see the problem? You will need 16 times more solar panels in the Winter than you would in the Summer.
Question 2: Batteries Not Lasting?
So by looking at the answer to question 1: you can see you are at a 93.75% disadvantage during the dark Winter months, this means there is less power to run equipment and charge the batteries.
Question 3: Battery voltage dropping so quickly?
So by looking at question 1 & 2: Because of the reduction in power produced from the solar panel the batteries take longer to charge, adding to this problem is the lack of daylight hours that means the need for lighting increases so the demand on the battery increases.
This is why it is so important to design your system so it can cope with the Winter months, or have some grid backup or generator available. Once you breakthrough February life is easy again until Winter comes back around, hopefully you have learnt from your mistakes the year before so you are more prepared.
Thanks for taking time to read this, for some people this is a big shock to them as they expect the Solar Panels to perform just as well in the Winter as they do in the Summer and I’m sorry to tell you that’s not happening, Winter is Winter for a reason.