UPS/inverter system

keyturbocars

Re: UPS/inverter system

Sounds like your UPS might be better than some. I did some more testing on my UPS under full load using a DC clamp on ammeter to measure incoming current, and it came out real close to the (>93%) rating by APC. I actually calculated closer to 95%, so it fits their "greater than 93%" claim.

Have you ever tested yours to verify the efficiency?

I guess it doesn't matter. If it works for what you need and you are happy with it, then it probably doesn't matter.

Edward

techntrek

Re: UPS/inverter system

Its on my to-do list. Next time I get to Sears I'll be getting one of those $60 clamp-on meters that keeps getting mentioned around here. I'm very interested in what the no-load amp draw is - that will determine if I get an extra PV panel or get a new inverter when I "go PV".

BB.

Re: UPS/inverter system

I am the guy that keeps hawking the DC current clamp meters.

The sixty dollar meter is a good entry level meter and good enough for debugging.

I am not making any money off of them and would not use them to prove ninety eight or ninety nine percent type numbers. I don't want to over sell anyone on its capabilities (it does not do RMS readings for example).

-Bill

PS: So it would not be the "best meter" to use with MSW (modified square wave) type AC inverters (Square Waves will read different with a meter that assumes a "sine wave" AC current profile vs the true RMS/Root Mean Square reading by a more expensive meter).

techntrek

Re: UPS/inverter system

Its "good enough" and that's all I need. I've also considered just getting a shunt from Windsun and doing the calculations by hand.

thehardway

Re: UPS/inverter system

OK, I have had two contractors out to look at my site in the past two weeks. Based on their input, it looks like I will be going with a 3-3.5Kw grid-tied PV array which will be on a ground mount. No shading on the "pathfinder" with south facing array. There will also be a Solar thermal collector.

The third contractor never showed on Sat. and never called to explain why. Not a good sign.

Are there any specifics I should look for in their proposals?

The distance between the array and my mechanical building and distribution panel/meter base will be about 60'. I will bury a 3" sched 40 PVC condui tfrom the location to house the wiring.

Are there any DIY kits that I should consider in the comparison. What would the best output voltage for the panels be? How much benefit would a tracking system provide? What invertor would be best suited for this application? I may add more capacity in the future are any of the systems better than others for future expansion?

Cariboocoot

Re: UPS/inverter system

We seem to have wandered down a winding lane from using a UPS unit to installing a GT inverter system! As Douglas Adams called it: the fundamental interconnectedness of everything.

I'll take a stab at the latest batch of questions, but it's early so the answers may not be any good.

thehardway wrote: »

Are there any DIY kits that I should consider in the comparison?

In general, DIY solar kits are so much rubbish. This is partly because solar is highly site specific and needs to be tailored as such and partly because these kits are put together by people looking to make a big profit by selling cheap junk at high prices to the unsuspecting.

What would the best output voltage for the panels be?

Whatever range the particular inverter chosen calls for. Most run around 250-500 VDC. Microinverters run panel Voltage.

How much benefit would a tracking system provide?

Probably almost none. They are technically more efficient, but the extra cost usually doesn't justify the gain. The same money spent on more fixed mount panels will more often than not yield a greater over-all harvest. There are always exceptions.

What invertor would be best suited for this application?

The one that fits your capacity and budget requirements. SMA Sunnyboy inverters are usually a good choice. Which is not to detract from others. Look here: http://www.solar-electric.com/gridtiesolar.html

I may add more capacity in the future are any of the systems better than others for future expansion?

Future expansion of any solar electric system is a headache at best, and often a nightmare. With Grid tie you can add a complete separate unit, providing your service can take the extra capacity. So if you have your breaker box all okayed (meets back feed capacity requirements) for 6 kW to begin with you can install 3 kW now and 3 kW later - but you'll have to go through the permitting process again (unless someone out there has a utility that allows "up to" in advance).

johnl

Re: UPS/inverter system

Cariboocoot wrote: »

thehardway wrote: »

Are there any DIY kits that I should consider in the comparison?

In general, DIY solar kits are so much rubbish. This is partly because solar is highly site specific and needs to be tailored as such and partly because these kits are put together by people looking to make a big profit by selling cheap junk at high prices to the unsuspecting.

I'd agree with this about any crappy kit that involves trying to make your own panels. But for homeowners who have some DIY skills, I do think there is value in a DIY kit that includes name-brand UL/CSA approved panels well matched to an appropriate name-brand UL/CSA approved inverter and good-quality name-brand mounts, along with some of the other balance-of-system components like combiner boxes, MC cables, disconnect switches. (especially if this means the DIY'er doesn't have to worry too much about the finer details of string calculations and doesn't have to deal with multiple vendors that can point the finger at each other when something goes wrong).

Sure, there's tons of junk/overpriced kits listed on fleaBay. But I've seen quite a few kits from some of the more established solar vendors on the net that look like they make some sense.

For example, I see that our forum host has some example kits quotes here:
(although they may be a few months out of date)
http://lib.store.yahoo.net/lib/wind-sun/10kw-gridtie.pdf
http://lib.store.yahoo.net/lib/wind-sun/5kw-gridtie.pdf
http://lib.store.yahoo.net/lib/wind-sun/2kw-gridtie.pdf

Of course for any kit like this to really be a good value, the components all have to be good quality items that will work in your particular install and be acceptable by your local inspection authorities, and the price should be less than or equal to the best available pricing for purchasing all the components separately.

Cariboocoot

Re: UPS/inverter system

Actually, those listed by NAWS are "sample system quotes" not kits like you find flogged elsewhere. They are there to give you and idea. NAWS will also give you a lot more help in selecting the right components for your particular application.

Peter_V

Re: UPS/inverter system

thehardway wrote: »

I will bury a 3" sched 40 PVC conduit from the location to house the wiring.

How much benefit would a tracking system provide? What invertor would be best suited for this application? I may add more capacity in the future are any of the systems better than others for future expansion?

Why 3" Seems a little on the large size. I only used 1" conduit on my system, though the electrician said I could use 3/4". But then my array only uses 10ga wire to the house.

I use Zomeworks trackers. They cost me about $2400 more than using fixed pole top mounts for my 3.45 kw array.
I don't have a full years worth of data yet, but I've been comparing the output of my array to a nearby 4kw fixed array.
From what I've seen so far the trackers improve wintertime performance by about 16% and summertime performance by about 30%
I'd probably see even more, but I have some morning shading issues from neighborhood trees and houses that delays the trackers "wake-up" by about an hour in the morning, and a nearby mountain rain cuts about an hour off my evening sunshine.
The thing I like best about the Zomeworks (besides being supper cheap trackers) is they have no electronics, no motors, etc. to wear out of fail.
They work by using heat from the sun to move a weight transfer fluid back and forth. With proper maintenance (lubricating the bearings and shocks twice a year) they should last the life of the array or longer.

There are a couple options for future expansion. You can start with an inverter that is larger than you need now (tends to run a bit less efficiently now though), however you have to worry about trying to match panels when you expand later.
You can get an inverter than matches your current needs, and then add a second inverter and panels later.

Or you can use micro-inverters (which is what I've done), that way panel matching (to your existing array) isn't an issue.
Micro-inverters cost more per watt, however you avoid all of the DC components needed by central inverters. No DC combiner panels, no DC fuses/breakers, no DC fuse box/ breaker panel, no DC wiring, etc. This brings them a bit closer to parity. They are also MUCH easier to install you you generally save on installation costs.
The micro inverters run MPPT and optimize on a per panel basis, independent testing indicates this can improve your energy harvest by 5% or more.
Plus if you have an inverter failure, you only lose one panels worth of power until you can get it replaced.
If you have to replace an Enphase inverter out of warranty, it's less than $200 compared to $2,000-$4,000 for central inverters.
Considering the Enphase micro-inverters come with a 15 year warranty, compared to 2 to 5 yr warranty for most of the central inverters, it seems likely that you'll have to buy at least one more central inverter before the micro inverter even come out of warranty.
Looking at the enphase MTBF figures there is a good chance that most of your inverters will last the lifetime of the PV panels.

Oh yeah, there are some central inverters that do MPPT on a per panel basis using DC-DC converters, etc. With one of these panel matching would not be an issue either. However, the other issues remain, and I think they are more complicated to install than ordinary central inverters. I have no idea how well they work, perhaps someone else can chime in on that.

BB.

Re: UPS/inverter system

Personally, if I am trenching for electrical, I like to use an over-sized plastic pipe in case I want to add/change something later... I also recommend running a second large(r) pipe (I use whatever is cheap) if additional control/communication wiring is needed now or in the future (and needs to be isolated from AC power).

The cost of the extra pipe is usually not very much compared to the cost of trenching and the rest of the job.

-Bill

Peter_V

Re: UPS/inverter system

Cariboocoot wrote: »

Future expansion of any solar electric system is a headache at best, and often a nightmare. With Grid tie you can add a complete separate unit, providing your service can take the extra capacity. So if you have your breaker box all okayed (meets back feed capacity requirements) for 6 kW to begin with you can install 3 kW now and 3 kW later - but you'll have to go through the permitting process again (unless someone out there has a utility that allows "up to" in advance).

I've been wondering about that when it comes to micro-inverters. I only have 15 inverters now, but my wiring and breakers are setup for 18 or 19.

Since all I need to do to expand my system is plug in the new inverters (no stripping wires and messing around with bare conductors, etc.) I wonder if I'll need a new permit to add a couple more inverters.
I asked my power company and they don't care, but they wanted to be sure I understood I can't get any more incentives for the extra panels/inverters.
I haven't checked with the county yet to see if they'll require a new permit.
I'll guess 'll try calling them today and see what they have to say.

Peter_V

Re: UPS/inverter system

BB. wrote: »

Personally, if I am trenching for electrical, I like to use an over-sized plastic pipe in case I want to add/change something later... I also recommend running a second large(r) pipe (I use whatever is cheap) if additional control/communication wiring is needed now or in the future (and needs to be isolated from AC power).

The cost of the extra pipe is usually not very much compared to the cost of trenching and the rest of the job.

-Bill

I agree that's why I wen tone size up, it's just that 3" seems overkill even for future expansion.
Heck it's overkill even if he's running 00 cables, which I doubt with only a 60' run.

thehardway

Re: UPS/inverter system

I have some extra 3" pvc left over from my construction so the cost is of no concern. I also have some 1.25" roll pipe I will put in for control wiring etc. since you mentioned it needs to be separate.

Seems to be 2 separate camps on trackers vs. no tracker. I guess this is the way I see it right now. If I don't mind covering the whole yard with panels and want to make a big statement to the neighbors that I'm solar powered then add more panels and forget the tracker. On the other hand, if I am space limited or concerned with efficient use of space and lowest possible number of panels then put in a tracker.


When I mentioned a kit I was referring to a package system deals I see on the internet like this:


12 strings of 6 modules in series
$ 1.81 PER WATT
Qty DESCRIPTION UNIT PRICE
72 Solar Panel - EPV-42 Thin Film Solar Panel 42 Watts $0.97 / Watt $40.74
12 Solar Panel Cable - MC3 Male To Female 30FT $33.03
12 Fuse Holder - MNTS $5.40
12 MNFUSE4 $8.00
1 Lightning Arrestor - LA602DC Delta 3 Wire 300V 36 Inch Leads $40.00
1 SMA Sunny Boy Grid Tie Inverter 3000 Watt SB3000US $1,588.00
1 Lightning Arrestor - LA302R Xantrex 600VAC $40.00
1 Combiner Box - Midnight Solar MNPV16 $319.20


Or like the 2.5K system pointed out on this site by Johnl.




I was not referring to the assemble yourself b stock cells and homemade panel kit type stuff. Whatever I do has to be certifiable so that I can get my rebate from the state.
Looks like I need to do some research on central vs. micro-invertors....

Peter_V

Re: UPS/inverter system

thehardway wrote: »

If I don't mind covering the whole yard with panels and want to make a big statement to the neighbors that I'm solar powered then add more panels and forget the tracker...

Well, I don't know... I think trackers make a pretty big statement:D At least it's kinda interesting to glance over at them throughout the day and notice that they are always pointing at a different piece of sky.

Mine seem to draw a lot more attention than roof mounted arrays.

For me the biggest concern was cost.

My house faces South West so the picture window in the living room can have a good view of the nearby mountains (about 2 miles away)

Because of this I would have needed a 5kw roof mounter array to produce the same power as my 3.45kw tracker mounted array. The extra 1.5 kw worth of panels, etc. would have cost WAY more than the trackers.
Besides I don't like punching holes in my roof, sooner or later it seems like they always leak.

I didn't want the array mounted in the front yard were it would be susceptible to vandals and my backyard has a 6 foot block wall so a low ground mounted array wouldn't have produced well either.

When I compared the cost of available pole top mounted to the trackers I bought, well it was easy to justify the small increase in price for the large increase in performance.

FWIW I used PVwatts to model the different systems, I'm not sure if you familiar with it, but you can plug in most of the system variables as well as location data and get a pretty accurate estimate of how your system will perform, down to an hourly basis.

http://www.nrel.gov/rredc/pvwatts/

thehardway

Re: UPS/inverter system

Peter_V wrote: »

it's kinda interesting to glance over at them throughout the day and notice that they are always pointing at a different piece of sky.

Seems like you could almost make some kind of neat clock/sundial from this and turn it into a work of art!

Your point is well taken. I don't like the idea of punching holes in my roof either.

Thanks for the website link on trackers. will look it over.