Electronics > Power/Renewable Energy/EV's

Tilting (at) solar panels

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Someone:
Running the numbers for installing some solar systems in Melbourne (37.5 degrees south) comes up with some interesting optimisations for positioning. The "default" annualised daily generation factor suggests 32 degrees off level:

But this is simply to globally maximise energy generation for a fixed system. Peak power delivery can be shifted several hours into to the afternoon without measurable losses by rotating the panels mounting in the direction of the setting sun, but this has seasonal limitations and vertical tilt has seasonal variations. These for a north facing array and are normalised to the 25 years of historical average insolation data from the Australian Bureau of Meteorology to include climatic/seasonal/local variations and assume a perfect sky view with no shadowing:

Back from the "Direct" 100% fill in the case of a perfect 2 axis tracker, the fixed possibilities average around 70% of the perfect tracking. Sticking to an optimal fixed 30 degree install averages an annual load factor of 24% which is achievable and proven in installations.

But if the mounts were adjustable and you manually changed the tilt with the season you could get 5% more energy for a two angle schedule, or 7% more for a 3 angle schedule. Seems like its worth the couple of hours a year to shift the panels and keep them clean.

Seekonk:
Seldom can panels be idealized unless you live in the middle of nowhere.  My panels are fixed and lay almost flat, about 10 degrees.  Like to keep a low profile because all my panels are not even on my own land.  I am almost a batteryless system and prefer more even power throughout the day rather a higher daily total.

mtdoc:
I have 2 solar arrays. One is an 1800 watt array on a pole mounted 1 axis tracker.  I manually adjust the tilt twice a year (spring and fall) to eack out a bit more production - but honestly the gains are minimal.  My other array is 2700 watts on a fixed south facing 45 degree tilt on a shed (I live at 48 degrees North).

NREL has an excellent online tool.  Their PV Watts Calcuator lets you set your location, array size, etc and then adjust tilt to see how theoretical output (based on historical solar insolation data) changes.

Someone:

--- Quote from: 3roomlab on August 06, 2016, 04:03:54 pm ---Did you try to use some of those sun path tools? (btw, I think the Y scale is in error, should be 0.1kWh to 1.2kWh)

--- End quote ---
Its all using sun paths, otherwise you cant optimise the panel facings. The vertical axis is correct in its maximum of 12 kWh/m2/day or 12000 Wh/m2/day peak insolation.

--- Quote from: mtdoc on August 06, 2016, 05:55:50 pm ---I have 2 solar arrays. One is an 1800 watt array on a pole mounted 1 axis tracker.  I manually adjust the tilt twice a year (spring and fall) to eack out a bit more production - but honestly the gains are minimal.  My other array is 2700 watts on a fixed south facing 45 degree tilt on a shed (I live at 48 degrees North).
--- End quote ---
Like trackers there is this weird intermediate system size around 10-100kW where it makes sense to adjust the tilt seasonally. The amount needed to adjust the tilt between seasons is similar for most latitudes.

--- Quote from: mtdoc on August 06, 2016, 05:55:50 pm ---NREL has an excellent online tool.  Their PV Watts Calcuator lets you set your location, array size, etc and then adjust tilt to see how theoretical output (based on historical solar insolation data) changes.
--- End quote ---
I'm not sure where they pull their numbers from but they estimate a 10% load factor for Melbourne, which is much less than half the achievable performance, perhaps there is a large derating factor for shading to keep the public consumers happy? And it may not be doing full path tracking since it doesnt match the relative changes between 30 and 60 degree mountings in my fully worked example.

Red Squirrel:
I always thought it would be neat to setup an array like space stations, but it would have to be very strong if there is a wind gust.  Basically it would deploy upwards in the morning and face east, and slowly turn and track the sun. Then at night it would retract. This would also keep the snow off.  You'd only get one axis of tracking but you'd get exposure throughout the whole day.

I also wonder how well mirrors could work to boost solar output, you don't want to cook them, but maybe just one line of flat mirrors that reflects more sun to the panels.  I guess where you can put the mirrors you can just put more panels.  More expensive but more output.

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