Solar panel angles

Arkansasoffgrid

Longitude -93.2406049
Latitude 34.37799
Porch roof is 3/12 pitch, house roof is 12/12 pitch. Will either of these angles work for solar panel installation, or will I have to build an adjustable setup?

Cariboocoot

Re: Solar panel angles

Well the ideal angle would be about 29 degrees for fixed, year-round at 34 Lat.

3/12 pitch is about 14 degrees, rather flat.
12/12 pitch is about 45 degrees, rather steep.

We're it me I'd put it on the flatter roof and add some 'leg' to the back to get it up around 30 degrees.

Mac's Lab explanation on panel angles: http://www.macslab.com/optsolar.html

NorthGuy

Re: Solar panel angles

If you're off grid, you probably have much worse conditions in winter. The array built for winter will be too big fo summer. Nothing you can do about that. If you build something that works in winter, it will work in summer too, even though the angle is not optimal. Therefore, I would suggest optimizing everything for winter, which means steeper angle for the panels.

BB.

Re: Solar panel angles

Use PV Watts to estimate the amount of energy you can collect per month... And decide if you want more power in the summer (on grid system, best savings on power costs, and/or A/C costs).

Vs off grid system where winter has very low production and you need every kWH you can generate.

Weather can also play a factor too... if you have cloudy winters (on average), then array angle will not help or hurt you much. PV Watts is based on actual ~20 year average solar irradiation and will account for average weather/cloud conditions.

Some folks have made tilting arrays (tilt for summer/winter)--But most people seem to leave them at one angle unless they have significant snows--Then near vertical will really help keep panels clear in winter and may have have an advantage if there is a open snow covered field to the south (reflections).

PV Watts Little Rock Ark, fixed array, 1 kWatt, 0.52 off grid efficiency:

"Optimum" angle = 34.8 degrees:

"Station Identification"
"City:","Little_Rock"
"State:","Arkansas"
"Lat (deg N):", 34.73
"Long (deg W):", 92.23
"Elev (m): ", 81
"PV System Specifications"
"DC Rating:"," 1.0 kW"
"DC to AC Derate Factor:"," 0.520"
"AC Rating:"," 0.5 kW"
"Array Type: Fixed Tilt"
"Array Tilt:"," 34.8"
"Array Azimuth:","180.0"

"Energy Specifications"
"Cost of Electricity:"," 7.4 cents/kWh"

"Results"
"Month", "Solar Radiation (kWh/m^2/day)", "AC Energy (kWh) per month", "Energy Value ($)"
1, 3.78, 59, 4.37
2, 4.38, 61, 4.51
3, 5.19, 78, 5.77
4, 5.67, 79, 5.85
5, 5.89, 83, 6.14
6, 5.81, 77, 5.70
7, 5.93, 80, 5.92
8, 6.08, 83, 6.14
9, 5.41, 73, 5.40
10, 5.16, 75, 5.55
11, 3.69, 53, 3.92
12, 3.56, 55, 4.07
"Year", 5.05, 856, 63.34

Tan-invers 3/12 = 14 degrees:

"Station Identification"
"City:","Little_Rock"
"State:","Arkansas"
"Lat (deg N):", 34.73
"Long (deg W):", 92.23
"Elev (m): ", 81
"PV System Specifications"
"DC Rating:"," 1.0 kW"
"DC to AC Derate Factor:"," 0.520"
"AC Rating:"," 0.5 kW"
"Array Type: Fixed Tilt"
"Array Tilt:"," 14.0"
"Array Azimuth:","180.0"

"Energy Specifications"
"Cost of Electricity:"," 7.4 cents/kWh"

"Results"
"Month", "Solar Radiation (kWh/m^2/day)", "AC Energy (kWh)", "Energy Value ($)"
1, 3.10, 48, 3.55
2, 3.85, 53, 3.92
3, 4.90, 73, 5.40
4, 5.77, 81, 5.99
5, 6.32, 90, 6.66
6, 6.42, 86, 6.36
7, 6.45, 88, 6.51
8, 6.28, 86, 6.36
9, 5.23, 70, 5.18
10, 4.59, 66, 4.88
11, 3.11, 44, 3.26
12, 2.86, 43, 3.18
"Year", 4.91, 829, 61.35

Tan-ivers 12/12 = 45 degrees:

"Station Identification"
"City:","Little_Rock"
"State:","Arkansas"
"Lat (deg N):", 34.73
"Long (deg W):", 92.23
"Elev (m): ", 81
"PV System Specifications"
"DC Rating:"," 1.0 kW"
"DC to AC Derate Factor:"," 0.520"
"AC Rating:"," 0.5 kW"
"Array Type: Fixed Tilt"
"Array Tilt:"," 45.0"
"Array Azimuth:","180.0"

"Energy Specifications"
"Cost of Electricity:"," 7.4 cents/kWh"

"Results"
"Month", "Solar Radiation (kWh/m^2/day)", "AC Energy (kWh)", "Energy Value ($)"
1, 3.97, 62, 4.59
2, 4.48, 62, 4.59
3, 5.14, 77, 5.70
4, 5.41, 76, 5.62
5, 5.46, 76, 5.62
6, 5.30, 70, 5.18
7, 5.45, 73, 5.40
8, 5.75, 78, 5.77
9, 5.30, 71, 5.25
10, 5.24, 76, 5.62
11, 3.84, 55, 4.07
12, 3.76, 58, 4.29
"Year", 4.93, 835, 61.79

You decide when the power does you the most good (winter/summer) and if manual tilt is "worth it" for you -- Or just add 10-20% more panels and call it "fixed tracking" array.

-Bill

niel

Re: Solar panel angles

for off grid geared more for winter raise the angles higher by at least lat +15 degrees. 29=15=44 degrees.