Sun hours

[bcroe]

Running 2 to 1 DC/AC ratio those Fronius inverters will be screaming on a sunny day.

Part of the reason for easily adjusted tilt, is to better level out the power level over the day, an
ongoing experiment. The curves from a while back are some of the results. For the several
snow months, I expect to just put them vertical, possibly not the perfect angle but not a high
production time anyway. I expect them to them be nearly immune to snow, and ground snow
will do better with reflected sun. Bruce Roe

[bcroe]

Overnight we received some unwelcome ice followed by a couple inches of snow. But it did provide another
snow trial of the array, esp the latest design just put into service this month. At 6:45 am sun time the newest
array (facing east) was well irradiated, with no ice and barely any snow. One quick swipe and 6 KW were
operational. The next near vertical section wasn't entirely out of the shade yet, but took little effort to clear
the snow. What little ice was left, will soon be gone as the sun rises.

The less elevated section (facing south) had a solid layer of ice covered by a couple inches of snow. The
snow slots allowed efficient clearing of the snow, will have to wait for a somewhat more favorable sun
position (and the rising temp) to finish by melting the ice. But by 7am sun time, the system was producing
8KW, more than 50% of capacity. Sorry I didn't take a camera to record the event. Bruce Roe

[DanS26]

.......At 6:45 am sun time the newest
array (facing east) was well irradiated.........

Can the new array tilt to the west for afternoon summer production?

[bcroe]

Can the new array tilt to the west for afternoon summer production?

No, that would be efficient in an open field. But here it would just be looking straight at the west neighbors
trees. So the plan is, I have a big clearing, and all panels are at an edge looking across the clearing. To
cover the other direction (setting sun), panels need to be on the opposite side of the clearing facing west.
Give me another year. This is not actually wasteful (by my definition), because I needed this many panels
to keep production up under various levels of clouds, my starting point.

But it was a pretty sunny day, collected 145 KWH. The only time I made those numbers before, was
around June. But this is April, the new array is doing what those test panel curves said, getting power
going pretty early in the morning. If this continues to check out, I expect to move some of the south
facing panels around to face west. Not planning to add any more. Bruce Roe
PVm17Jn16.jpg

[bcroe]

145KWH yesterday was pretty good. But today did 149KWH, a match for my best day ever, and not in
June this time. With 150, looks like that elusive 10 sun hour day might happen this summer. Bruce Roe

[J.P.M.]

145KWH yesterday was pretty good. But today did 149KWH, a match for my best day ever, and not in
June this time. With 150, looks like that elusive 10 sun hour day might happen this summer. Bruce Roe

How do you define a 10 hour sun day ?

[bcroe]

This not officially recognized term, here is the AC production for the day, divided by the inverter capacity.
So 150KWH divided by 15KW plant would be 10 hours. Only 9.93 yesterday. Bruce Roe

[J.P.M.]

This not officially recognized term, here is the AC production for the day, divided by the inverter capacity.
So 150KWH divided by 15KW plant would be 10 hours. Only 9.93 yesterday. Bruce Roe

Since the more common and for several reasons unfortunate definition, IMO anyway, of 1 "sun-hour" = 1kWh/m^ per day of irradiance, usually but not always referenced to the horizontal plane, I'm just trying to avoid more confusion in my own mind over the term.

Looks like your definition has units of kWh of system production/day per kW if inverter capacity. Following the S.I. naming convention for many other derived units, maybe we should name such a unit a "Roe" to perhaps avoid more confusion over the term "sun-hours".

Respectfully,

[bcroe]

Since the more common and for several reasons unfortunate definition, IMO anyway, of 1 "sun-hour" = 1kWh/m^ per day of irradiance, usually but not always referenced to the horizontal plane, I'm just trying to avoid more confusion in my own mind over the term.

Looks like your definition has units of kWh of system production/day per kW if inverter capacity. Following the S.I. naming convention for many other derived units, maybe we should name such a unit a "Roe" to perhaps avoid more confusion over the term "sun-hours".

Respectfully,

Ha Ha, do not want to interfere with established convention, with the slang term. INETDOG suggested
Multiple Array Orientation Factor (MAOF), maybe it is time to start using it. Not really up to me to name it.

Did an MAOF of 9.93 Friday, hoping during longer days to see 10. Bruce Roe

[SunEagle]

Ha Ha, do not want to interfere with established convention, with the slang term. INETDOG suggested
Multiple Array Orientation Factor (MAOF), maybe it is time to start using it. Not really up to me to name it.

Did an MAOF of 9.93 Friday, hoping during longer days to see 10. Bruce Roe

How would you define a solar array that" tracks" the sun from morning to night? That may fall into the "10 hour sun day" category.

[bcroe]

How would you define a solar array that" tracks" the sun from morning to night? That may fall into the
"10 hour sun day" category.

From what I have seen, a tracking array will come in second. First, it uses the same panels all day for
collection. There will still be a bell curve of less extreme variation.

You need MORE panels near sunrise or sunset, to keep inverters at the same level. The curves
measured here of actual sun take that into consideration, and the panels are set up accordingly to
try and approximate a flat energy curve.

And of course, a tracking array cannot do anything about clouds. Adding panels for cloudy operation
was the starting point of this project, getting the energy broadened when there are no clouds (almost
never here) is the second step.

We should hear what some trackers have actually done here at 42 deg Latitude. But I don't see them
as practical for homeowners. Perhaps the MAOF idea could be applied to them. Bruce Roe

[J.P.M.]

Ha Ha, do not want to interfere with established convention, with the slang term. INETDOG suggested
Multiple Array Orientation Factor (MAOF), maybe it is time to start using it. Not really up to me to name it.

Did an MAOF of 9.93 Friday, hoping during longer days to see 10. Bruce Roe

Well Bruce, seems to me the term "sun hour" causes enough unnecessary and easily avoidable confusion already among neophytes and newcomers as evidenced, for example, by those who think because the sun is above the horizon for, say 8 hrs., that means there was 8 sun-hours that day. Or, they are told that their location gets, say, 4 sun-hours/day on average, not knowing that the common units of a sun-hour are kWh/m^2 per hour insolation with no mention of that energy being on a horizontal surface or that a tilted surface may very well see more (or less) insolation over the course of a day simply by virtue of orientation. The way I see it, it's a B.S. term that invites errors and causes needless confusion, wastes time and so can easily cause errors, plain and simple. I see it here and elsewhere all the time.

The confusion is easily overcome by simply using the term "Global Horizontal Insolation per time period" instead of "sun-hours", with the time period being anywhere from a second to a year or longer as appropriate, with abbreviations such as "GHI/day", or GHI/hr., or GHI/year, etc. Units are Wh/m^2 per time period, etc., or, for example, kWh/m^2 per day instead of "sun-hours". As a matter of reality, that usage ("GHI/time period") is pretty much common in the rational and working solar community and has been accepted for longer than I've been around alternate energy. The term "sun-hours is an anachronism made so by the confusion it causes.

Now, you come along with a different and somewhat parochial definition of sun-hours that seems to be useful to you, and I don't doubt that it is (useful for you), but is so specialized and cryptic that not only does it do nothing to clarify an already confusing and less than helpful characterization of insolation by use of the term "sun-hours", but seems pretty much useless for system analysis as well.

[bcroe]

Now, you come along with a different and somewhat parochial definition of sun-hours that seems to be useful to you, and I don't doubt that it is (useful for you), but is so specialized and cryptic that not only does it do nothing to clarify an already confusing and less than helpful characterization of insolation by use of the term "sun-hours", but seems pretty much useless for system analysis as well.

Hey, I already said I would try not to use bad language any more. Bruce

[solar pete]

I for one welcome our new MAOF overlord cheers

[J.P.M.]

I for one welcome our new MAOF overlord cheers

As you wish. Not that anyone need care, but I regard Bruce as a valued resource around here. Hell (and with apologies for talking about you in the 3d person Bruce), he's probably the only one more eccentric about this stuff than I am, but in different ways.

Now help find a practical and useful application for the concept and the term MAOF.

Since the units of the parameter MAOF seem to be kWh/day - or just as well any time period - per kW of inverter size, regardless its seems, of array size, then perhaps some use could be made of the ratio MAOF/(array output per day/installed S.T.C. kW of panels). That would give array S.T.C. size /inverter capacity , so the ratio might be considered dimensionless, and that ratio may be useful as some parameter to use as some possible tool to help choosing and sizing single or multiple inverters for an installation.

Just trying to improve communication and maybe reduce confusion a bit along the way.

J.P.M.