Sun hours

[bcroe]

Horizontal axis

When you look at it that way, the tradeoff becomes the hassle in changing the settings of the time clock a few times during the year and the reliability of the time source versus the complexity and accompanying risk of failure of a true tracker.

In some areas (sub tropical in particular) the horizontal axis tracker is worth looking into also.

Potentially far lower stresses on the support and tracking mechanism.

A horizontal axis tracker might be the most likely for the future, simple, and able to
dump snow. How about, the panels look somewhat at the ground while its snowing,
then come around clean later? Guess there would need to be some cameras out there,
so I could see what is going on. Bruce Roe

[bcroe]

Tracking, panels, & snow

Bruce,
You seem to be a DIY type of guy from the posts from you that I have read.
Why not do a solar tracker? I have seen some on ebay for $155. for a 4 panel array.

My thought instead of a "tracker" why not just have the panels move to a predetermined position?
Something like 30 deg to the East till 10am flat or horizontal from 10am till 2pm then 30 deg
west after 2pm. (you would probably have to adjust angles and times for your location)

It could be made a little more robust than a tracker, and you might be able to tip fully vertical to drop
the snow off of your array. Just a thought, how crazy do you think my idea is?

Plan it, simulate it, build it & see what happens. If a tracker holds 4 panels, I would need dozens of
them. I believe you need more space for trackers, so that they don't shadow each other? Can I trust
the tracker when its -20F, there is a half foot of snow on the array, and 2' on the ground? How many
times can you move it before the wires break; is the grounding safe?

The snow issue (and clearing it) might be the best reason to consider moveable arrays. Perhaps you
can pick up 25% energy with tracking. But at day extremes sunlight is weaker; add more panels and
get it close to mid day much faster. I was running equivalent to 7 2/3 sun hours Sat (clipping), don't
think a tracker could do that.

Overcast, the light is dispersed, the tracker can't find a perfect direction. But extra panels work well
bringing up extra power on those (frequent in ILL) days, orientation isn't critical. That is my best
reason, the panels will be pointed to avoid a strong peak at any one time of day, when the sun is out.

So that is the situation here for now; but draw up your ideas and see if they compute. Bruce

[inetdog]

Bruce,
You seem to be a DIY type of guy from the posts from you that I have read.
Why not do a solar tracker? I have seen some on ebay for $155. for a 4 panel array.

My thought instead of a "tracker" why not just have the panels move to a predetermined position?
Something like 30 deg to the East till 10am flat or horizontal from 10am till 2pm then 30 deg west after 2pm. (you would probably have to adjust angles and times for your location)

It could be made a little more robust than a tracker, and you might be able to tip fully vertical to drop the snow off of your array.

Just a thought, how crazy do you think my idea is?

When you look at it that way, the tradeoff becomes the hassle in changing the settings of the time clock a few times during the year and the reliability of the time source versus the complexity and accompanying risk of failure of a true tracker.

In some areas (sub tropical in particular) the horizontal axis tracker is worth looking into also.

Potentially far lower stresses on the support and tracking mechanism.

[FUN4ME]

Bruce,
You seem to be a DIY type of guy from the posts from you that I have read.
Why not do a solar tracker? I have seen some on ebay for $155. for a 4 panel array.

My thought instead of a "tracker" why not just have the panels move to a predetermined position?
Something like 30 deg to the East till 10am flat or horizontal from 10am till 2pm then 30 deg west after 2pm. (you would probably have to adjust angles and times for your location)

It could be made a little more robust than a tracker, and you might be able to tip fully vertical to drop the snow off of your array.

Just a thought, how crazy do you think my idea is?

[bcroe]

Don't forget about September there will be a difference from march due to higher temps

Ok, need to consider temperature to get panel output; more output in March than Sept.
But perhaps it won't affect MAOF, which I see as a pure ratio. Bruce

[Naptown]

Don't forget about September there will be a difference from march due to higher temps

[bcroe]

I suppose that you could coin a term like Multiple Array Orientation Factor (MAOF) to describe this.
But for any particular installation, the value of that factor will depend on the exact orientation of the two sub arrays, the morning and afternoon weather at the site, etc.

You can get a useful approximation of this factor by looking up the PVwatts values for the two arrays separately and comparing it to the PVwatts value for a single south facing array of the same size as one of the sub-arrays.
As long as there is not an overlap between the producing hours of the two sub-arrays which would exceed the input wattage of the GTI or CC and cause clipping, this should give you the number you want.
But in the real world, you may also need to factor in Time Of Use rate structures, etc., and PVwatts will not do that for you.

OK, its MAOF for now. Multiply your SUN HOURS by your MAOF to predict a days output. Not
considering the Time Of Use, since it doesn't apply here. This idea can't be pushed too far before
some clipping happens, so I think an hour by hour simulation of each orientation must then be
added up, and limited on any hour to the maximum. It will also vary by season; I thought running
it for 20 Dec, 20 Mar, and 20 June would give a good picture. Bruce Roe

[inetdog]

I was just thinking about the definition of SUN HOURS. Like, with my sun rise to sunset being
10:50 hours now, the total energy hitting a given panel might be equivalent to 5 hours of perfect
sun noon. So then its 5 SUN HOURS that day, location, and alignment.

Working this backwards, harvesting 110 KWH divided by 15 KW inverter maximum (clipping)
level, gives 7.33 equivalent SUN HOURS. The idea of course is to stretch the sun day by adding
panels directly facing the rising & setting sun. Comparing this to the basic sun hours could be
a multiplying factor for the panel arrangement. Probably the factor doesn't have a name? I'm
still looking for a tool to use, to predict this factor. Bruce Roe

I suppose that you could coin a term like Multiple Array Orientation Factor (MAOF) to describe this.
But for any particular installation, the value of that factor will depend on the exact orientation of the two sub arrays, the morning and afternoon weather at the site, etc.

You can get a useful approximation of this factor by looking up the PVwatts values for the two arrays separately and comparing it to the PVwatts value for a single south facing array of the same size as one of the sub-arrays.
As long as there is not an overlap between the producing hours of the two sub-arrays which would exceed the input wattage of the GTI or CC and cause clipping, this should give you the number you want.
But in the real world, you may also need to factor in Time Of Use rate structures, etc., and PVwatts will not do that for you.

[bcroe]

I was just thinking about the definition of SUN HOURS. Like, with my sun rise to sunset being
10:50 hours now, the total energy hitting a given panel might be equivalent to 5 hours of perfect
sun noon. So then its 5 SUN HOURS that day, location, and alignment.

Working this backwards, harvesting 110 KWH divided by 15 KW inverter maximum (clipping)
level, gives 7.33 equivalent SUN HOURS. The idea of course is to stretch the sun day by adding
panels directly facing the rising & setting sun. Comparing this to the basic sun hours could be
a multiplying factor for the panel arrangement. Probably the factor doesn't have a name? I'm
still looking for a tool to use, to predict this factor. Bruce Roe