Yes, I've been to that 'sunroof' web site, but it doesn't give me any details, so I haven't the slightest idea what calculations it is actually performing. Furthermore, it doesn't know the pitch of my roof, unless it is doing some clever image-matching from different satellite angles. At 08:16 AM 6/29/2020, Thomas Colthurst wrote:
I did this! Well, I and a small team. google.com/sunroof
It even does the integral over every pixel of your roof, so as to take into account shading from nearby trees and houses (as well as non-flat roofs, horizon effects, chimneys and other roof obstructions, ...).
You might also like NREL's PVWatts calculator <https://pvwatts.nrel.gov/>, which is less accurate (because it doesn't do the full ray-tracing over the roof thing) but provides more intermediate information.
-Thomas C
On Mon, Jun 29, 2020 at 10:52 AM Henry Baker <hbaker1@pipeline.com> wrote:
I'm considering putting a solar PV system on my roof, and I thought that I should be able to calculate most of the numbers myself from first principles. I have searched for so-called online 'calculators', but found that most of them are aimed at idiots.
Here's what I expected to find:
A formula giving the exact sun position throughout the year, given latitude and longitude, as well as a factor which handles the distance from the sun w.r.t. time.
Now this only provides the *input* energy.
I now need to overlay this with average *weather* data on a per-hour basis to get the expected net energy.
Finally, I need to *integrate* these data over an entire year to get the values for my own house.
There may be such an online calculator, but I haven't been able to find it yet.
It may be possible to factor the weather info out of the integration, so that I could 'correct' my location sunlight & weather data with my own lat/lon azimuth (angle of my house) and roof angle, but I'd need to see the equations to find out if this factoring is possible.
I presume that someone on this list has already done these calculations for their own home?