What Primary Components Do You Think Are Needed To Make This Work?

rss2q · January 2012

I have been given a project that involves a structure that will have 4 sides like a regular building, and solar panels will be placed on all 4 sides. Since only 2 of those sides will receive direct sunlight, the use of a series of mirrors will be used to bend the light to shine direct light on the other 2 sides. I know this is something unusual, different and maybe unpractical, but I have been given the task of getting this project completed regardless.

This system will not contain any batteries, so instead, the energy produced will be sent back to the grid.

So my primary question here is, if the structure will have 24 60Watt panels on 3 sides of the structure, and 16 60Watt panels on 1 side, what is the best method to hook these panels up? Meaning, would it be best to have each side have it's own separate MPPT charge controller, or would you recommend another method?
Second, other than the charge controller, what other primary components would one need other than a grid tie inverter (and getting someone who is certified to install the device) in order to send power back to the grid, and if wanted, use the power it is producing during the day to power a laptop for example?

Thanks :roll:

BB. · January 2012

Re: What Primary Components Do You Think Are Needed To Make This Work?

Is this a school project or something "real"?

Some issues that make the 4 sided building impractical as spec'ed:

60 watt panels are very expensive ($$$/Watt)
60 watt panels require more physical mounts and electrical wiring/connections
Panels mounted on vertical S/E/W walls will have very poor summer light collection
Panels on wall, if mounted low, may have issues with snow on ground/theft (easier to steal)
Mirrors would have to have active tracking (keep sun shining on panels)
Mirrors could not use simple sun following circuit as they need to focus the beam on a fixed location
Mirrors would have to be cleaned
Each "orientation" will need its own GT controller
You should probably use Enphase or equivalent micro GT inverters
In theory, I believe that Enphase are "Listed" with a defined set of panels (typically in the ~200 watt range). May have difficulties with getting ~4 60 watt panels approved. And you may have problems matching Vmp/Imp of 60 watt panels into Enphase compatible "micro" arrays
Mounting panels on walls--Generally, you will have to fence the structure to avoid "touch" hazards (normally, panels on roof are >8' off ground and don't need fencing).
If you can use Enphase (or similar) inverters and can get a 60 watt panel array to meet Enphase/Micro GT Vmp/Imp specs, then the local AHJ (authority having jurisdiction) will probably be OK.

Not sure of the Grid Tied vs Laptop connections difference... GT Inverter plugs into Grid to operate. Laptop plugs into Grid to operate. Unless you are after emergency power, not sure what the specific/special connection may be with a laptop.

I don't think it is practical as designed--But I don't have the justification for these requirements.

-Bill

rss2q · January 2012

Re: What Primary Components Do You Think Are Needed To Make This Work?

BB. wrote: »

Is this a school project or something "real"?

Some issues that make the 4 sided building impractical as spec'ed:
60 watt panels are very expensive ($$$/Watt)

60 watt panels require more physical mounts and electrical wiring/connections

Panels mounted on vertical S/E/W walls will have very poor summer light collection

Panels on wall, if mounted low, may have issues with snow on ground/theft (easier to steal)

Mirrors would have to have active tracking (keep sun shining on panels)

Mirrors could not use simple sun following circuit as they need to focus the beam on a fixed location

Mirrors would have to be cleaned

Each "orientation" will need its own GT controller

You should probably use Enphase or equivalent micro GT inverters

In theory, I believe that Enphase are "Listed" with a defined set of panels (typically in the ~200 watt range). May have difficulties with getting ~4 60 watt panels approved. And you may have problems matching Vmp/Imp of 60 watt panels into Enphase compatible "micro" arrays

Mounting panels on walls--Generally, you will have to fence the structure to avoid "touch" hazards (normally, panels on roof are >8' off ground and don't need fencing).

If you can use Enphase (or similar) inverters and can get a 60 watt panel array to meet Enphase/Micro GT Vmp/Imp specs, then the local AHJ (authority having jurisdiction) will probably be OK.

Not sure of the Grid Tied vs Laptop connections difference... GT Inverter plugs into Grid to operate. Laptop plugs into Grid to operate. Unless you are after emergency power, not sure what the specific/special connection may be with a laptop.

I don't think it is practical as designed--But I don't have the justification for these requirements.

-Bill

This will be a real project, and the structure would have the style of a pyramid, so there will be a slight angle on the 4 sides. I was not aware of the fencing and sun tracker for the mirrors so I will add that to the parts list.

As far as hooking up the panels, if we treated each side seperately, and for 1 side we connected two sets of 12 panels in parallel, and then wired both of those sets in series for a total of 24v 37.2A (I think my math is right), then would this charge controller work: http://www.solar-electric.com/motr60ampmps.html ?

Regarding this project, a small business owner is working to receive a solar grant from the government and came up with this idea and is wanting me to take lead, so now we have to put a parts list together, so my plan is to buy most of the solar electronics from Wind-Sun. So I really appreciate any help, as this is a really unusual project for me to try to get completed (as far as figuring out the best way to implement it) if the grant gets approved for the second phase.

niel · January 2012

Re: What Primary Components Do You Think Are Needed To Make This Work?

mirrors are a no no on standard pvs as it would void their warranties.
it is impractical to place pvs where the sun doesn't shine.
paying $2.50/w is a bit high and you can do better. see here- http://www.solar-electric.com/hiposopa.html
if you find a place that has wall mounts for pvs, please let me know as i have been looking for some myself.

a pyramid? is this in vegas?

rss2q · January 2012

Re: What Primary Components Do You Think Are Needed To Make This Work?

niel wrote: »

mirrors are a no no on standard pvs as it would void their warranties.

Well if they void the warranty, that would squash this entire project. Is it possible for you to direct me to where this is officially stated so I can let the owner know? As there is no reason for me to look more into this impractical project he wants completed if the warranty will be void and this system will not even meet the main standards/codes to be considered something that could be placed on the marketplace after this prototype.

BB. · January 2012

Re: What Primary Components Do You Think Are Needed To Make This Work?

Are you after grid tied, off grid, or Hybrid type inverter?

One thing I forgot to add--You may have problems sourcing UL 60 Watt panels that are rated for 600 VAC (used for Grid Tied).

Will be less of an issue for Off-Grid/Battery system--But many of the smaller wattage panels are only rated for 70-75 VDC (series connections). Not great for higher Vmp Arrays or 48 VDC battery banks. If inspected, the inspector may not even notice these issues.

Regarding the use of tracking mirrors... Would be much easier, cheaper, and more practical to remove the mirrors and put solar panels on the trackers instead. Or not even bother to connect the North Facing panels (the amount of power they will generate, without computer driven mirrors, may be minimal (perhaps around 50% +/- of the south facing array for summer; and 10% or so during winter). Obviously, the exact numbers depend on actual tilt of arrays and where this will be installed.

And, when all is said and done, you probably will need about 2x the square area of mirrors vs solar panels to account for losses (reflection, refraction, dirt on mirrors). Would be be looking a flat or curved mirrors to focus the light? Glass or Mylar? Wash every few weeks to keep clean? Need a computer driven XY tracker programed with geometry of installation and the position of sun over the year/time of day.

Is this intended to be a practical or artistic installation?

-Bill

rss2q · January 2012

Re: What Primary Components Do You Think Are Needed To Make This Work?

BB. wrote: »

Is this intended to be a practical or artistic installation?
-Bill

He wanted to see if it would be practical, to see if using this method would increase your power consumption by placing panels on all 4 sides, so my orginal task was just to see if it was even doable, which a few have claimed it is, however, all agree that it is just too impractical. The more I look into, and I'm glad I open this thread here, the more evidence I'm receiving that this project is just not worth the time or effort.

So I just found 2 warranty forms online from two different companies that state, "Do not use mirrors or other hardware to artificially concentrate sunlight on the module.". So now I am somewhat switching gears and just trying to compile a list of reasons why he should reconsider this approach.

niel · January 2012

Re: What Primary Components Do You Think Are Needed To Make This Work?

mirrors can concentrate the sun and none of these pvs are rated for concentrated sun. as bb pointed out the mirrors would need to track the sun anyway so this project may not look pretty anyway with mirrors all over the place. if you have that kind of room for mirrors then put the pvs there where the mirrors would be instead and on poles and trackers if you like.

rss2q · January 2012

Re: What Primary Components Do You Think Are Needed To Make This Work?

niel wrote: »

if you have that kind of room for mirrors then put the pvs there where the mirrors would be instead and on poles and trackers if you like.

Yep makes perfect sense to me. So I am not sure if he has to have something out of the ordainary implemented in order to receive a solar grant from the government or not, but I will pass this info along. Thanks for your help niel and Bill!

Cariboocoot · January 2012

Re: What Primary Components Do You Think Are Needed To Make This Work?

Unless you're buying the mirrors from the University of Rochester's Laser Energetic labs (don't ask how I know, I'm not allowed to tell) the panels fed reflected light will be far lower in production than their rating. Likely less than 50% at best. It is highly unlikely that correct angle of incidence will be maintained even with trackers.

Just my opinion, but this sounds like a "wouldn't this be cool?" project that's as practical as a bicycle for fish.

LandKurt · January 2012

Re: What Primary Components Do You Think Are Needed To Make This Work?

There is a spot where a four sided setup might make a little sense: near the poles during the summer. With 24 hour sun circling near the horizon it might actually make sense to cover all four sides with solar panels and have no batteries. The remote location rules out grid tie though.

Anywhere else the idea is a complete non-starter. Analyze each of the sides of the building with PVWATTS and compare the output of each. I did so and was surprised to find that a vertical north facing array at my location gathers 26% the power of an ideally angled south facing fixed array. I thought it would be less than that but I suppose even a north side gets some sun. Maybe some day solar will be cheap enough that covering north facing walls with PV will be worth it even at a four to one disadvantage in light gathering.

LandKurt · January 2012

Re: What Primary Components Do You Think Are Needed To Make This Work?

I took a second look at PVWatts since the figures didn't feel right.

It says yearly solar radiation figure for a north facing vertical panel is 26% that of an ideally angled south facing panel. But the yearly AC energy produced figure is only 18.6% for that same north facing panel. I don't understand why those figures vary.

Note that in June the north facing panel generates 29% of optimum but in December it only makes 7%.

Of course, a vertical north facing panel is worst case. If you tilted the panel to 45% like a proper pyramid your yearly power would increase to 40% of optimum. Though the December power is still only 13% that of a south facing panel. It's offset by producing 79% of optimum in June. I'm surprised to find that a north facing 45 degree angled panel produces 80% the power of a south facing panel in June. At least according to PVWatts for my location at 39 N.

Out of curiosity I ran the figures for a diagonally oriented pyramid with 45 degree sides facing NW, SW, SE, NE. The figures aren't that bad; the NW and NE sides produce about 50% optimum yearly and the southern sides run about 91%. The northern sides are pretty useless in winter but do decently during the summer. The whole system produces about 71% the annual power that it would if it all faced south at a fixed angle. It would have the advantage of taking up less space. So maybe a pyramid covered with PV on all four sides isn't ridiculous.

There is the possibility that PVWatts doesn't produce very good figures for north facing arrays as that's not what it was designed to do. Anyone know from experience whether a NE or NW facing roof does as well during summer as PVWatts says?

BB. · January 2012

Re: What Primary Components Do You Think Are Needed To Make This Work?

It should be pretty accurate... I haven seen a couple homes here with north facing arrays on shallow sloped roofs around here (located in the summer fog capital of the San Francisco area coastline).

PV Watts also takes local weather into account... If you have cloudy winters/sunny summers it will affect the numbers too.

Solar Guppy found that in his region (Florida), that aiming his array south east gave him more power than facing south. Between the cooler morning temperatures and the summer thunder showers, it averaged better production.

-Bill

Cariboocoot · January 2012

Re: What Primary Components Do You Think Are Needed To Make This Work?

Keep in mind that the proposal is to use mirrors to direct light to the North-facing panels. The mirrors could reflect roughly 80% of the sun. The biggest problem would be trying to maintain an efficient alignment between the sun moving on two axis (so to speak) with panels at fixed angle by trying to move the mirrors. A nightmare of geometry and trigonometry.

niel · January 2012

Re: What Primary Components Do You Think Are Needed To Make This Work?

the tracking with the mirrors isn't the big problem. if one were to use 1 mirror of the same dimensions as the pv then it would be good to assume that it could illuminate that pv by a tad under what it would've been in direct sunlight. most will put more mirror area than that and each of those mirrors will also put near full intensity sun onto the pv. it will concentrate whether intended or not and the pvs simply aren't made to have high artificially enhanced exposures.

like i said in the first place, if you have room for mirrors that are in the sun then you have room to put the pvs there in the sun instead of the mirrors. how much simpler can this get?

What Primary Components Do You Think Are Needed To Make This Work?

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