Proper tilt, many differing opinions.

bbbuddy

We plan to do a pipe mount, tiltable, for our panels.

Each of 8 solar stores in our area gave us wildly differing angles to use, from 0-15 to 0-80!

Online, I find these:
A solar panel's angle should be set to the equivalent of your your latitude plus 15 degrees during winter, or minus 15 degrees in summer.

and:
30-35° add 10° to local latitude
35-40° add 15° to local latitude

and:
http://www.macslab.com/optsolar.html
winter angle - multiply latitude x.9, add 29 (gives us 60)

SOOOO, this can be VERY confusing, no one seems to agree.

The last one (macslab.com) at least seems to have done some actual research...and from what I gather, while their tilts may not be the best at highest sun hours, overall they yeild more energy by getting more during earlier am and later pm angles...

Any feedback on here from people who have tried the angles from macslab.com, or know of reasons to do otherwise?

Thanks!

BB.

Re: Proper tilt, many differing opinions.

You can play with the PV Watts website and set different angles and see how they compare. It is very easy to do.

Also, there are a couple caveats too...

1. Panels should be mounted with at least 5 degree tilt as this will help them self clean (rain washing off dust and leaves).
2. Panels in regions with significant snow can be mounted near vertical to have better snow shedding, and significant solar reflection from snow/ice fields in front of the array... Remember to mount high enough to be clear of drifts and have a room for snow to slid of the panel.

-Bill

Cariboocoot

Re: Proper tilt, many differing opinions.

I trust the macslab angles. I find they work.
Be sure and read the explanations for choosing the different potential angles.

mike95490

Re: Proper tilt, many differing opinions.

BB. wrote: »

You can play with the PV Watts website and set different angles and see how they compare. It is very easy to do.

I used the PV watts site to plan my array, and set the tilt for Nov/Jan angle. This gives me the best harvest for the shortest days. My summer, (at the winter angle) so far, has been fine, and I expect my big water pump loads will diminish in winter when I'm not irrigating fields

Mike

bbbuddy

Re: Proper tilt, many differing opinions.

BB. wrote: »

You can play with the PV Watts website and set different angles and see how they compare. It is very easy to do.

Also, there are a couple caveats too...

1. Panels should be mounted with at least 5 degree tilt as this will help them self clean (rain washing off dust and leaves).
2. Panels in regions with significant snow can be mounted near vertical to have better snow shedding, and significant solar reflection from snow/ice fields in front of the array... Remember to mount high enough to be clear of drifts and have a room for snow to slid of the panel.

-Bill

I must be dumb, I don't see how to use it. I got a map that wouldn't do anything I asked it to do, not even go to the right zip code. Maybe it's my computer. Zip is 85924

BB.

Re: Proper tilt, many differing opinions.

Did you use the PV Watts V. 1 or the PV Watts V.2?

I know that quite a few people use the PVW V2--But I could not figure it out when I tried it once or twice years ago. (also PVW V2 only works in the US--the PVW V1 has a few international data sets too).

PV Watts V.1 there are no Zip Codes--You just click on the states (or pull downs on the right side if not in the US) and go from there.

-Bill

rplarry

Re: Proper tilt, many differing opinions.

bbbuddy
If I understand your original post correctly, you are building a pole mount array that is tiltable. If that is correct then just tilt your panels until they are perpendicular to the sun. As the seasons progress that angle will change and you can adjust as necessary. Obviously I am missing something. My panels are pole mounted and that is how I do mine.
Larry

bbbuddy

Re: Proper tilt, many differing opinions.

rplarry wrote: »

bbbuddy
If I understand your original post correctly, you are building a pole mount array that is tiltable. If that is correct then just tilt your panels until they are perpendicular to the sun. As the seasons progress that angle will change and you can adjust as necessary. Obviously I am missing something. My panels are pole mounted and that is how I do mine.
Larry

Larry, I thought that seemed right too, until I started "double checking" and getting so many differing opinions.
The websight: http://www.macslab.com/optsolar.html

has a formula for the angles for spring/fall, summer and winter.

I "think" it has to do with getting more power before and after the noon tilt angle, and less at the hours closest to noon will actually yield higher watt output for the whole day.

Cariboocoot

Re: Proper tilt, many differing opinions.

It's a question of fixed angle or changing angle. The macslab site gives you data for different angles all year 'round if you care to adjust them 2 or 4 times per annum. It also explains what the advantages/disadvantages are for picking any one and sticking with it. The closer you are to the equator, the less difference between Winter and Summer of course. Up here, it's more than 50 degrees of tilt!

Or you can use the parallel stick shadow method: mount a stick parallel to the surface of the panel and then adjust the panel's angle at midday so that the shadow is the same length as the stick.

Or buy a tracker, if you've got money to burn.

Mangas

Re: Proper tilt, many differing opinions.

I've always wondered how much charging I would pick up in winter if I changed the ground mounted array tilt. So far, I've just left them in the summer position.

Get my lazy out there and try it this year.

jcgee88

Re: Proper tilt, many differing opinions.

bbbuddy wrote: »

I must be dumb, I don't see how to use it. I got a map that wouldn't do anything I asked it to do, not even go to the right zip code.

I use PV-Watts V2, and it's not very easy to get the data
entry screen to fire up. The directions using zip code get
you to a certain point, but when I would click on the
resultant map for my location, I would get a missing link
error. I finally figured out how to run it, using lat/long:

1. Access PV-Watts V2 by clicking here:

http://mapserve2.nrel.gov/website/L48NEWPVWatts/viewer.htm

2. PV-Watts' US Solar Atlas screen will come up; now turn off your
browser's pop up blocker (remember to turn it back on later);

3. Enter your lat/long in the field at the bottom of the screen

For example, St Louis' Gateway Arch is: 38.37/-90.11

[Notice the minus sign for longitude!]

Your contractor can provide your lat/long, or you can get it by
running Google Earth for your specific address.

4. Click on Go next to the lat/long field box. The map will zoom
to the entered lat/long address.

5. Click on the PV-Watts icon in the center, near the top;
it will highlight with a red box around itself; you don't need to
click on the "launch PV-Watts" button on the right;

6. Move your cursor onto the map itself (the little red triangle inside
the map will work), left click, and then the data entry screen will
pop up.

7. Fill out the data entry screen, including the most important
parameters:

a. Tilt angle...the angle the panels are tilted towards the sun,
zero is flat, 90 is vertical.
b. Azimuth...the angle the panels face relative to the earth,
zero is straight north, 180 is straight south.
c. Derate factor...default is 77%, set lower if you have shading
issues. Nominal perfect is 80%; typical "unperfect" is 72%.

8. Once you've filled out the data entry screen, click on the
"Calculate" button near the bottom left of the screen. A report
will come up, which you can print or save.

--

One last thing, if you have multiple strings, with different angles
for each, you will need to run PV-Watts separately for each string,
and then add up the results to get the estimate for the entire site.

John

bbbuddy

Re: Proper tilt, many differing opinions.

Mangas wrote: »

I've always wondered how much charging I would pick up in winter if I changed the ground mounted array tilt. So far, I've just left them in the summer position.

Get my lazy out there and try it this year.

Whoa, Mangas! Go take a look-see at the macslab webite http://www.macslab.com/optsolar.html There is a graph about 1/2 way down the page showing the effects of tilting, tracking, and just leaving in place. You will be kicking yourself for losing that much extra power 6 months of the year....

Mangas

Re: Proper tilt, many differing opinions.

I figure about 10-12% with a winter adjustment.

We may try after the equinox.