Sun hours

[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

[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 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

[Naptown]

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

[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

[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?

[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.

[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

[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

[Naptown]

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

Don't know about any one else's warranty but that would void the Sunjpower warranty

[inetdog]

Don't know about any one else's warranty but that would void the Sunjpower warranty

Putting them on a horizontal axis tracker at all, or just turning them so far that the back of the panel is exposed to weather and snow load?

How about just turning them far enough (even partially inverted) to dump the snow after it has stopped snowing and then turning them right side up again?

[FUN4ME]

I guess I should have called my idea a horizontal tracker.
I have no idea what wire does when it is -20deg you would know better than me.
I don't think you would need to turn the panel upside down if you had 2 primary tilts
both of them say 20deg off of vertical one to the east and one to the west, how much snow could accumulate while chancing positions?
also i wasn't suggesting that you change your whole array, just the panels you were planning on adding.
good luck

[inetdog]

I guess I should have called my idea a horizontal tracker.
I have no idea what wire does when it is -20deg you would know better than me.
I don't think you would need to turn the panel upside down if you had 2 primary tilts
both of them say 20deg off of vertical one to the east and one to the west, how much snow could accumulate while chancing positions?
also i wasn't suggesting that you change your whole array, just the panels you were planning on adding.
good luck

A lot of wire insulation loses too much of its flexibility at -20F to be reliable. Finding an insulation with the right combination of sunlight resistance and flexibility could be interesting, but the bending radius would not be particularly small if you laid it out correctly. A long horizontal run properly supported would allow the wire to twist rather than bending, which should put far lower demands on its flexibility.

[bcroe]

Panel angle

I don't think you would need to turn the panel upside down if you
had 2 primary tilts both of them say 20deg off of vertical one to the east and one to the
west, how much snow could accumulate while chancing positions?
also i wasn't suggesting that you change your whole array, just the panels you were
planning on adding. good luck

Even my near vertical panels pick up some snow, though much easier to clear than the others. Thinking
that tilted a bit more to just past vertical ought to be enough to keep them clear. I suspect once the snow
is on, it won't slide off so easily. Running out of good unshaded places to put any more panels; would only
need them to boost overcast days. I am not above rearranging everything, if for a good enough reason.

Don't know about any one else's warranty but that would void the Sunjpower warranty

Is that for tracking, or for vertical angle, or for anything past vertical? Here nothing is under warrantee
for very long, interferes with activities. Bruce Roe

[russ]

Here nothing is under warrantee for very long, interferes with activities. Bruce Roe

I like that!