Panel angle
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velvetfoot
Minister of Fire
Would that depend on what time of year it is? I recall 45 deg. being optimum for our area in winter. Less so in summer. Don't have any numbers though.
Where2
Feeling the Heat
Please review the tables for New York based on the location nearest your town, and report your findings.
http://rredc.nrel.gov/solar/pubs/redbook/PDFs/NY.PDF
Look at the table marked "Flat Plate Collector facing south at fixed tilt", use the "year" column. Divide the 90° tilt yearly value by one of the common tilt values (like latitude-15).
http://rredc.nrel.gov/solar/pubs/redbook/PDFs/NY.PDF
Look at the table marked "Flat Plate Collector facing south at fixed tilt", use the "year" column. Divide the 90° tilt yearly value by one of the common tilt values (like latitude-15).
Most of the modeling software doesn't account for snow on the ground and on the panels so they overstate the loss of generation with a vertical panel. A panel with snow on it doesn't generate power and contrary to what solar salesman say, the snow doesn't rapidly slide off. (I spent 2 hours on an extension ladder cleaning snow off my roof mounted panels after 2 warm sunny days as the snow was on there solid). Had those panels been vertical I would have been generating for those two days. Vertical panels get sun reflected from the snow so even though the angle is not optimum the snow reflection compensates for some of the loss.
In deep snow areas on unattended installations the standard recommendation is to hang the panels vertical. I believe that the All Earth tracking arrays made in VT are setup to stow vertically at night to prevent snow accumulation during the night and dump any snow that collected on them during the day.
In deep snow areas on unattended installations the standard recommendation is to hang the panels vertical. I believe that the All Earth tracking arrays made in VT are setup to stow vertically at night to prevent snow accumulation during the night and dump any snow that collected on them during the day.
Circus
Feeling the Heat
Not too difficult to figure out. The first 10 degree off don't matter much but after that it does. Seeing that in the summer the sun is out much longer and is more intense any bias should be for maximum summer efficiency.
I have vertical solar hot air collectors and, by design, in the summer I get no heat. Works good in the winter. Electricity output would be similar.
I have vertical solar hot air collectors and, by design, in the summer I get no heat. Works good in the winter. Electricity output would be similar.
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jebatty
Minister of Fire
My ground mount panels are 220' from the house. The energy loss between the panels and the house is 1.2% as measured by energy reported by the microinverters at the array and energy reported by the kWh production meter at the house. Tilt is 35*. Winter production is excellent with snow reflection plus dry, clean and low humidity atmosphere. Peak February daily production runs at about 80% of peak summer daily production. Ground mount is important where I live due to need to clear snow. Brushing the snow off the 12.2kW array with a soft hair floor brush takes about 10 minutes.
Circus
Feeling the Heat
45 deg. is half way between summer optimal of 69 deg. and winter optimal of 23 deg. up from the southern horizon, guessing NY latitude. Of course, the bulk of the time the sun is in between. A vertical panel is 0 deg.
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I beat on my panels far more than jebatty. I use a plastic roof rake. Its pretty amazing how much abuse they will take. I don't go around testing them wiith a ball peen hammer but they are quite robust Most are rated for pretty good size piece of hail to hit them dead on.
Be aware that panel angle also is impacted by on grid versus off grid use. I see quite few steep panel installations on long term off grid installs I encounter on occasion. Off gridders dont have net metering or long term storage so they optimize their systems to maximize winter production and that means a steep angle.
On grid folks want to get maximum year round production at low cost and that typically means roughly the angle is the local latitude. Adding manually adjustable vertical angles are supposed to add about 10% annual production and dual axis trackers usually add 30%. Two of my arrays are adjustable for vertical angle and its noticeable the production jump I get when I move them 4 times a year. I should have moved them a few weeks ago but due to potential snow loading I usually hold off on cranking them up from 30 to 45 degrees until march. There is still snow on the ground so I don't loose than much production
Dual axis trackers used to be popular but they are quite expensive. Given the collapse in panel pricing I expect its far cheaper to just install more panels. I expect they still might be a fit for someone without a lot of space. They double as kinetic sculpture
Be aware that panel angle also is impacted by on grid versus off grid use. I see quite few steep panel installations on long term off grid installs I encounter on occasion. Off gridders dont have net metering or long term storage so they optimize their systems to maximize winter production and that means a steep angle.
On grid folks want to get maximum year round production at low cost and that typically means roughly the angle is the local latitude. Adding manually adjustable vertical angles are supposed to add about 10% annual production and dual axis trackers usually add 30%. Two of my arrays are adjustable for vertical angle and its noticeable the production jump I get when I move them 4 times a year. I should have moved them a few weeks ago but due to potential snow loading I usually hold off on cranking them up from 30 to 45 degrees until march. There is still snow on the ground so I don't loose than much production
Dual axis trackers used to be popular but they are quite expensive. Given the collapse in panel pricing I expect its far cheaper to just install more panels. I expect they still might be a fit for someone without a lot of space. They double as kinetic sculpture
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Conveniently, I'm at the top of the list in Albany, NY. It's showing a yearly average of 4.3 and a min/max of :3.7/4.7 at -15.
so 3.7/4.3 or 86% of the average amount of sunlight captured at this latitude?
Circus
Feeling the Heat
Circus
Feeling the Heat
Where2
Feeling the Heat
Yes, that's why I said divide the 90° (yearly average) value by the comparison (yearly average) tilt value of your choice. Tilt angles are vertical angles which are measured up from the horizon, with 90° being perpendicular to the horizon (i.e. hanging on a wall).
Using the Albany table values, I read 3.0/4.3 = 69.8% as a realistic value to compare a 90° installation to a latitude (or latitude-15°) tilt. If you were getting 15% efficiency from the panels, then a 90° installation would provide 10.5% efficiency. That's a considerable loss, and presumes either panel installation is facing exactly due south. When you start twisting off facing precisely due south, efficiency goes down more.
Twisting off of true south may be desirable based on local conditions and or by incentives. In some areas morning fog is pretty predicable and therefore twisting west of south will yield higher output. This is not something that most software will pick up. Far more likely is local shading. If there is a stand of trees on a neighbors property to the west twisting east of south yield more total output. I believe some areas in CA have incentives in place that encourage arrays pointing west of south to increase afternoon production.
We have two arrays. One facing south and the other facing southwest. That has extended our output bell curve notably in the summer. It also helps pickup afternoon sun when there are foggy mornings and the south facing array's output is low until mid-day.
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