How do I know what angle to use if my roof is facing the wrong direction?

[Jerfmon]

I am putting a solar powered attic fan on my roof. If I had a flat roof, I would have my panel facing south at a 17 degree angle. However, my roof faces east-west at a 30 degree pitch. I'll put my panel on the west roof with the panel facing south, but how do I adjust the angle of the panel given that it's facing west and 'downhill?' Or should I just leave it at 17 degrees and call it a day?

 

[MisterSandals]

Depends whether you are in Canada or near the equator. That is the key bit of info to formulate an answer.
If you can make it adjustable for summer and winter it would be more efficient. Otherwise pick whatever tht best sun angle for the time of year you need more power (heat or air conditioning).

 

[lowrads]

I'm not a fan of attic fans versus improving ceiling insulation, at least in a house that doesn't rely on combustion heating, but it seems like you'd have the most demand on such a system from mid-day onward. Ergo, capture the afternoon sun.

 

[time2roll]

Or should I just leave it at 17 degrees and call it a day?

That is it. Don't over think it.

 

[Jerfmon]

Depends whether you are in Canada or near the equator. That is the key bit of info to formulate an answer.
If you can make it adjustable for summer and winter it would be more efficient. Otherwise pick whatever tht best sun angle for the time of year you need more power (heat or air conditioning).

I'm 45 degrees latitude, zip code 98604

 

[rin67630]

the very best would probably be a panel east and another one west in //.
That would give you the longest fan run daily.

 

[MichaelK]

What has worked well for me is to draw a scale drawing of where I want to position my panels, and place the sun in the drawing depending on where I expect it to be for whatever time of day, and length of the season. I usually use a scale of 1mm=1inch. It has worked well for me.

 

[daviddakers]

Solar Angle Calculator

The solar angle calculator tells you by location the optimum angle to get the best out of your system.

www.solarelectricityhandbook.com

 

[rin67630]

Solar Angle Calculator

The solar angle calculator tells you by location the optimum angle to get the best out of your system.

www.solarelectricityhandbook.com

There is no universal optimum for a given location as the above mentioned angle calculator suggests.
It depends on a lot of factors, the fist of them being: what will you do with the energy?
If you just sell the energy to the grid, it comes to get the maximum when you get full sun and then the angle calculator is the right thing.
If you are off grid and have a back-up generator then you might just want to get a flat curve when it is sunny enough.
If you are fully dependent on the panel for a 24/24/365 solar operation under every possible weather, then you should orient your panel at 45% slope to get the potential snow away and get the most of an overclouded sky. The position of the sun gets more or less irrelevant, when it is sunny you will get power in excess anyhow.

 

[Atomic Ed]

Solar Angle Calculator

The solar angle calculator tells you by location the optimum angle to get the best out of your system.

www.solarelectricityhandbook.com

Thanks for posting that link its a handy tool

 

[daviddakers]

There is no universal optimum for a given location as the above mentioned angle calculator suggests.
It depends on a lot of factors, the fist of them being: what will you do with the energy?
If you just sell the energy to the grid, it comes to get the maximum when you get full sun and then the angle calculator is the right thing.
If you are off grid and have a back-up generator then you might just want to get a flat curve when it is sunny enough.
If you are fully dependent on the panel for a 24/24/365 solar operation under every possible weather, then you should orient your panel at 45% slope to get the potential snow away and get the most of an overclouded sky. The position of the sun gets more or less irrelevant, when it is sunny you will get power in excess anyhow.

Yes, there are lots of factors, but it's a good starting point.