Solar Array Mounting

ggunn · October 2013

Re: Solar Array Mounting

Dave Sparks wrote: »

I see that you have changed you opinion on pointing an array up in diffuse light.

I don't see where you got that. In direct sunlight it is always better to point a module right at the sun than anywhere else. In diffuse light I have no data; you could be right or wrong; I dunno. My gut feeling is that it doesn't make a whole lot of difference whether it is straight up or a few degrees off vertical. You are talking about varying degrees of not so great, anyway.

zoneblue · October 2013

Re: Solar Array Mounting

Dave, correct me if im wrong but you seem to be promoting the use of this east west tracker. Heres your chance to put some curves up to demonstrate the strength of it. I for one am interested. Does it make up in am and pm for the midday loss? Your point about extending the length of the charging day is well made, but only useful for certain applications, like grid tie FIT.

Ggunns point that optimising for the optimum sun is better strategy for overall harvest numbers, also featured in my own decision making.

PS. How hard would it be to tilt the north south axis to latitude? I suppose if you are high latitudes its going to make the thing a huge sail. Break it into small sections and tilt them seperately, like this:

Attachment not found.

But if obviously if you google image search solar pv farm, 99% of the images are fixed tilt. Better number crunchers than i have made their own minds

https://www.google.co.nz/search?hl=en&site=imghp&tbm=isch&source=hp&biw=1024&bih=501&q=solar+pv+farm&oq=solar+pv+farm

BB. · October 2013

Re: Solar Array Mounting

Dave's customers are (usually?) off grid systems and Dave really likes the longer day for recharging batteries (more hours at lower average current give him longer battery life--If I remember earlier discussions).

And pumping grease in the Zerk fittings once or twice a year is the usual tracker maintenance.

-Bill

SandyP · October 2013

Re: Solar Array Mounting

BB. wrote: »

Dave's customers are (usually?) off grid systems and Dave really likes the longer day for recharging batteries (more hours at lower average current give him longer battery life--If I remember earlier discussions).
-Bill

Maybe the option of a "virtual tracker" would be of benefit. Extra panels required however no maintenance and more charging hours, see a discussion at :
http://forums.energymatters.com.au/solar-wind-gear/topic5505.html
The second page has some plots showing power outputs.

regards,
SandyP

Dave Angelini · October 2013

Re: Solar Array Mounting

BB. wrote: »

Dave's customers are (usually?) off grid systems and Dave really likes the longer day for recharging batteries (more hours at lower average current give him longer battery life--If I remember earlier discussions).

And pumping grease in the Zerk fittings once or twice a year is the usual tracker maintenance.

-Bill

yes four pumps a year on a single axis and some spray LPS on the motor shaft of the linear axis shaft of a dual axis or HZLA. Your memory is perfect, nice long days of power and the ability to complete charge on lousy days when the sun pokes thru the cloud cover for an hour or so in a winter storm you send me Bill. Then you throw in running a heat pump at full power (1500 watts +) summer cooling a home at 7pm without draining the battery and you get the picture.

Dave Angelini · October 2013

Re: Solar Array Mounting

zoneblue wrote: »

Dave, correct me if im wrong but you seem to be promoting the use of this east west tracker. Heres your chance to put some curves up to demonstrate the strength of it. I for one am interested. Does it make up in am and pm for the midday loss? Your point about extending the length of the charging day is well made, but only useful for certain applications, like grid tie FIT.

Ggunns point that optimising for the optimum sun is better strategy for overall harvest numbers, also featured in my own decision making.

PS. How hard would it be to tilt the north south axis to latitude? I suppose if you are high latitudes its going to make the thing a huge sail. Break it into small sections and tilt them seperately, like this:

Attachment not found.

But if obviously if you google image search solar pv farm, 99% of the images are fixed tilt. Better number crunchers than i have made their own minds

https://www.google.co.nz/search?hl=en&site=imghp&tbm=isch&source=hp&biw=1024&bih=501&q=solar+pv+farm&oq=solar+pv+farm

I am not just promoting it, I believe it and eat my own cooking! The picture you have would be ridiculous offgrid. An expensive way to mount panels that any increase in power would not be really noticed offgrid. At that point you should just consider dual axis as it would peak the power all year long. Dual axis offgrid is a waste of money and has the usual problem of maintenance in moving that array in the second axis. The modified single horizontal (Array Tek HZLA) solves the maintenance, improves the cost issue as well as gives very good power output all day/all year long. The picture you have shows the array tilt that is probably optimized for summer only. At that point you could just buy a conventional single axis pole mount and manually set the tilt (elevation) as often as you wanted. I will tell you something, I really design in 1500 watt increments for my folks. I do not care about peaking the performance. Most big loads are near 1500 watts and as long as I can get that most of the time the sun is out, I am happy. It sounds like you are grid based and most of what I am saying may not apply. Install on the roof and be happy!

zoneblue · October 2013

Re: Solar Array Mounting

The thing with airmass, is that when the sun is low on the horizon, the insolation falls off dramatically, regardless of angle of incidence. Any kind of tracker primarily enhances mid morning, mid afternoon performance.

SandyP, i have seen those virtual tracker curves, and thats why im keen to see curves for Daves east west single axis tracker.

Dave Angelini · October 2013

Re: Solar Array Mounting

zoneblue wrote: »

The thing with airmass, is that when the sun is low on the horizon, the insolation falls off dramatically, regardless of angle of incidence. Any kind of tracker primarily enhances mid morning, mid afternoon performance.

SandyP, i have seen those virtual tracker curves, and thats why im keen to see curves for Daves east west single axis tracker.

It all depends on what you mean by primarily enhances! If you mean there is more in mid morning and mid afternoon with a tracker then I would agree. If you mean that there is not that much more (and not usable amounts) at early morning and late afternoon compared to fixed, I would strongly disagree. I am looking at the output of a 1,920 watt nominal dual axis at 8:45 am and it is outputting 1,000 watts or so. The other array that is a single axis and not elevated correctly for this time of day is about 800 watts. The linear axis tracker is up the hill at my neighbors house and I do not have the data but I may go look at it tomorrow at this time. I may... I would guess that it is a small percentage less than the single axis at this early hour of the solar day.

BB. · October 2013

Re: Solar Array Mounting

I believe this is the product Dave Sparks is referring to:

http://arraytechinc.com/commercial/duratrack-hzla-comm/
http://arraytechinc.com/wp-content/uploads/NEW-DuraTrack-HZLA-Datasheet.pdf

Claims an improvement of 25% over fixed arrays.

But again, Dave is not saying this is more cost effective vs fixed arrays--It allows him more hours per day of significant current flow to charge the battery bank (and support day time loads).

From what little I have learned here about lead acid batteries, having more hours of current to complete the charging of the battery bank (and delay using batteries in evening/morning times)--Is not a bad thing.

The above will track +/- 45 degrees from "flat". For folks in higher latitudes--It may not be the best option for winter use where the sun stays closer to the horizon.

It does look like a simple/rugged system with fewer parts that can be mounted close to the ground for servicing (one actuator can move an relatively large string of panels).

As I always say, a paper design check before spending money. I would like to see a planning tool that would report on the East/West tracking ability (version of PV watts or similar--probably something out there).

Hmm... Looks like single axis tracking with Azimuth set to Zero Degrees should do it with PV Watts. For San Francisco, 4kW array, 0.52 eff:

"Station Identification"
"City:","San_Francisco"
"State:","California"
"Lat (deg N):", 37.62
"Long (deg W):", 122.38
"Elev (m): ", 5
"PV System Specifications"
"DC Rating:"," 4.0 kW"
"DC to AC Derate Factor:"," 0.520"
"AC Rating:"," 2.1 kW"
"Array Type: Fixed Tilt"
"Array Tilt:"," 37.6"
"Array Azimuth:","180.0"

"Energy Specifications"
"Cost of Electricity:","12.5 cents/kWh"

"Results"
"Month", "Solar Radiation (kWh/m^2/day)", "AC Energy (kWh)", "Energy Value ($)"
1, 3.62, 216, 27.00
2, 4.59, 250, 31.25
3, 5.22, 318, 39.75
4, 6.11, 356, 44.50
5, 6.36, 382, 47.75
6, 6.47, 374, 46.75
7, 7.01, 418, 52.25
8, 6.67, 397, 49.62
9, 6.62, 379, 47.38
10, 5.41, 321, 40.12
11, 3.87, 222, 27.75
12, 3.35, 201, 25.12
"Year", 5.45, 3833, 479.12

"Station Identification"
"City:","San_Francisco"
"State:","California"
"Lat (deg N):", 37.62
"Long (deg W):", 122.38
"Elev (m): ", 5
"PV System Specifications"
"DC Rating:"," 4.0 kW"
"DC to AC Derate Factor:"," 0.520"
"AC Rating:"," 2.1 kW"
"Array Type: 1-Axis Tracking"
"Array Tilt:"," 0.0"
"Array Azimuth:","180.0"

"Energy Specifications"
"Cost of Electricity:","12.5 cents/kWh"

"Results"
"Month", "Solar Radiation (kWh/m^2/day)", "AC Energy (kWh)", "Energy Value ($)"
1, 2.99, 177, 22.12
2, 4.30, 238, 29.75
3, 5.63, 351, 43.88
4, 7.51, 451, 56.38
5, 8.69, 541, 67.62
6, 9.09, 542, 67.75
7, 9.81, 602, 75.25
8, 8.60, 526, 65.75
9, 7.45, 438, 54.75
10, 5.29, 320, 40.00
11, 3.31, 191, 23.88
12, 2.70, 159, 19.88
"Year", 6.29, 4535, 566.88

Looks very nice for summer--During winter, if I did this correctly, I would get less power from the one axis East/West tracking array...

Fixed Array tilted to Latitude for San Francisco, Sunny day (I think) for 12/23/1974

1974
12
23
07:00
0

1974
12
23
08:00
9

1974
12
23
09:00
710

1974
12
23
10:00
1270

1974
12
23
11:00
1504

1974
12
23
12:00
1747

1974
12
23
13:00
1599

1974

12
23
14:00
1262

1974
12
23
15:00
1423

1974
12
23
16:00
881

1974
12
23
17:00
180

1974
12
23
18:00
0

Total WH
10585

One Axis Array flat for San Francisco, Sunny day (I think) for 12/23/1974

1974
12
23
07:00
0

1974
12
23
08:00
76

1974
12
23
09:00
893

1974
12
23
10:00
1149

1974
12
23
11:00
1048

1974
12
23
12:00
962

1974
12
23
13:00
889

1974
12
23
14:00
821

1974
12
23
15:00
1193

1974
12
23
16:00
1000

1974
12
23
17:00
410

1974
12
23
18:00
0

Total WH
8441

If I could tilt the axis to Latitude--It appears it would generate 10-20% more power in winter...

-Bill

ggunn · October 2013

Re: Solar Array Mounting

BB. wrote: »

If I could tilt the axis to Latitude--It appears it would generate 10-20% more power in winter...

-Bill

I had a customer in the Dallas area who had me looking at single axis trackers. With the axis tilted at latitude it would have been worth it if we could have used the cheapest tracker, but that one was horizontal only. The ones with a tilted axis were much more expensive.

westbranch · October 2013

Re: Solar Array Mounting

phoned the Co. and can add :

Smallest array design (domestic) is for 4Kw Array
Uses 1/15 hp motor, unable to tell me surge load
Daily 20Whr per day
Cost > $3000, shipping to Canada $500+

smallest member of axis is ~27 feet long.

SandyP · October 2013

Re: Solar Array Mounting

westbranch wrote: »

phoned the Co. and can add :

Cost > $3000, shipping to Canada $500+

smallest member of axis is ~27 feet long.

The "virtual tracker" option may be better/cheaper and may fit on a suitable roof.

Dave Angelini · October 2013

Re: Solar Array Mounting

westbranch wrote: »

phoned the Co. and can add :

Smallest array design (domestic) is for 4Kw Array
Uses 1/15 hp motor, unable to tell me surge load
Daily 20Whr per day
Cost > $3000, shipping to Canada $500+

smallest member of axis is ~27 feet long.

Keep in mind that the price is full retail. There are many dealers who will negotiate price as everything is drop shipped FOB. Typically a 35% mark-up. The surge on the motor is less than 5 amps at 24vdc nominal. In other words, there is not a noticeable surge. Energy used per day is about 20 watt hours. I believe they can build a smaller version of the 50 foot long 4,320 watt Panasonic/Sanyo I use if you ask. Probably between 20 and 25 feet.

Bill, I sent your data (thanks BTW) to my contact in Engineering and will see if they have time to comment. I liked your SF comment on the sunny days, "I think".

solorone · October 2013

Re: Solar Array Mounting

Cariboocoot wrote: »

That would depend on exactly what the compound is and its resulting electrolytic characteristics.

As it is you'll find the industry does have standards for connectors used with various types of PT lumber. Any place that sells it should be able to advise you on what's right for use with #1, #2, #3 (most common), #4, and #5 (marine grade). Note I said "should", not "absolutely will". :roll:

Before the change in PT lumber there was a standard, listed in the specifications of any job I had to use it on. It was stainless or hot dipped galvanized, hot dipped worked very well. The new stuff is of course different, but the engineers surely, somewhere have an opinion on the fasteners. I would by all means only use ground contact lumber, in air and ground, and any good rubber type compound ( truck/tractor inner tube??) between the aluminum and wood should solve some problems.

Solar Array Mounting

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