Does solar panel generates glare?

[michellewcy]

Hi,

Can someone tells me whether solar panel generates glare when sun shine on it? I later found out from manufracturer that solar panel has a layer of anti-glare coating on it, may i know how effective is this anti-glare coating?

My neighbour claims that solar panels installed on top of my 2nd storey roof generates glare into his bedroom and study room which situated in his 2nd storey house. I live in Melbourne, and my solar panels are installed on the west side of the house, because we don't enough roof room on our north side of the house. After months of discussion with the licensed solar installer, we decided to install solar panels on the west side of the house.

Appreciate your help here.

[c*p]

The answer is "yes". The panels will no doubt, produce some glare at particular times of the day and year. As I am sure you know, the panels have a sheet of glass in front of the Si cells. Being large, flat and smooth, the glass will reflect some sunlight, in the same way as a car windscreen or a house window. An anti-glare coating helps reduce this: any sunlight reflected reduces the amount getting through the glass to be absorbed by the Si cells. Thus the manufacturer would like to minimise the glare. It will not be entirely eliminated though.

The reflection will get into your neighbour's rooms only when the Sun is in a particular area of the sky. The duration of this unfortunate alignment depends on how far their windows are from your panels. It requires the Sun to be located specifically both North-South (varies through the year) and East-West, which is a daily variation. You should be able to notice brighter patches of light reflecting from your panels onto the walls of your neighbour's house around the time of the glare because it is unlikely that the reflection will be precisely aimed at their window: some will hit the wall adjacent to the window.

My guess is that it may happen around mid morning (and the neighbour is on your West). Before this, the Sun will not be shining on the panels as they will be in the shadow of your roof ridge capping. By late morning to noon, the sunlight will be reflecting off the panels upwards and so not into their window unless the window is much higher than your panels.

Our panels are also on the West, in Melbourne. I have not noticed glare on next door's house, but then I do not go out there in the mid morning to look for it. c*p.

[michellewcy]

Thanks for your explaination.

My neighbour house and my house is only separated by a common driveway. Forgive me if I'm asking silly questions here,
1. why the distance is a factor in this?
2. how long will the sun typically stays in one position? if you said from late morning till non, i would have guessed your assumption is correct here.

[c*p]

Hi Michelle. I'll answer you shortly.
Bevan, I am not sure whether your post is genuine or essentially a promotion in disguise. I have seen similar posts (in other threads) with minimal info and a link to "solar panels xxx" where "xxx" appears to be a State of the USA.

Michelle, your questions are not silly, as most people will not have thought about the issues they address. An accurate answer to question 2 is complicated and requires knowledge of a lot of details about your panels, the neighbour's window and their relative positions and orientations.

1. The distance matters in 2 ways, rather like shining a torch onto a wall. Firstly, as you step backwards, the beam spreads out and gets dimmer. Similarly with the reflection from the panels, distance allows the reflections to spread and thus become less intense. The second effect is how long the reflection will be bothersome. This goes to answer 2. as well.

2. Without going into technical details, the Sun moves at approximately between 14 and 15 degrees per hour; slower at the solstices. Thus the reflection will move at about the same rate. With the torch analogy, if you rotate the torch at a given rate, then when you are further away from the wall, the beam spot will move faster than if you are close to the wall. Applying this to the reflection involves some trigonometry and rough approximations. The tangent of 15 degrees is about 0.27, but to simplify, I'll assume it is 1/4. This means that if the neighbour's wall is 4m from your panels (I suggest unrealistically close), then in one hour, the reflection will move by 1m. It may take about 2 hours or more for the reflection to move from just entering their window to just leaving it. This strongly depends on how many panels you have and how they are arranged as this determines the shape of the reflection "beam" and thus the angles over which it will enter their window. Of course, the size of their window is also an important contributor to the duration of "bothersome-reflection". If the neighbour's wall is 8m away, then the reflection moves by 2m in each hour, and will pass the "bothersome-reflection" range in half the time. You could estimate the distance if both of your houses are on Google Maps "Satellite View" and make a better estimate of the duration yourself. You might take 8 divided by the distance and add 1 hour as a really rough guide.

Without any knowledge of the situation, I'd guess that the reflection might bother your neighbour somewhere between about 8.30 and 10.301am, possibly earlier but probably no later. c*p

[Ga Rick Lee]

Hi,

I've deleted Bevan's post as it is the same type of spam that we've seen in this forum before.

Great answer c*p. I don't think I can really add much to that!

Best regards,