to run 110V AC or 160V DC ?

westbranch

Background:I am trying to 'help' a friend get an OG PV system going at his cabin. I'll use his words , posted in italics...
there is a local Solar seller who he has also talked to.
My friend is a bit tight with his money and is looking for a 'cheap' system. He 'got into Solar' by running out and buying 1 PV and now what do I do?

I am trying to get him to see the folly of his ways, and to plan out the entire system he wants to end up with and then buy 'suitable equipment' not just whatever a Big local retailer has on the shelf.
I have made some headway here as he now realizes that his Blue Planet brand ~7A PWM CC is almost maxed out with 1 80W PV and is not charging his MARINE deep cycle battery completely... BUT he is greatly pleased with the fact that he now has 2 x 13W CFL's in the cabin.. 'so much light!'...

OK, so how is he getting power to the cabin? he has a small MSW inverter (75w? he doesn't know) making 110VAC that he sends down the hill to an electrical plug in, via 10Ga NMW10 for 100 feet (talked him into this due to line loss in NMW12 (You know, I have a whole roll of that!) then via 100 ft. 14 or 16 Ga extension cords (only has to go 15 feet...)

So today we had a chat and wrote down a list of all the possible lights he would like to have. Started with well just 4 in the main cabin room and ended with 18...

So he has one 80W panel, so I guess that is pretty much of little use? Nope, you can still use it s is to add to your charge capacity if you want... Oh, Good. See, tight wallet syndrome...

Then he shows me the ad in the local rag. 4 -240W/38V (?) GT PV panels (mismatched brands, but close specs) I'd have close to 1000W Yup but you will need an MPPT CC, Oh but he has 3 different Demo CC's for sale too, I could get one of them ARRGH!!!!!

First lets get the loads down... then figure out the batteries and then look at the PV and CC...

Well Ron told me it would be better to run the 4 GT's in series @ 160V than the 110VAC



So here is the question, I realize that there would be less line loss @ 160V DC vs 110V AC but what additional costs are there going to be in running a Hi DC voltage line vs a Hi V AC line?

I am thinking for simplicity and safety (I am not in favour of HI DC voltage, it scares the hell out of me).

Opinions and any data please..

Cariboocoot

Re: to run 110V AC or 160V DC ?

Wow. He's done almost absolutely nothing right. If I shake my head any more it will probably come off, so let's skip to the issue.

The higher the array Voltage is in relation to the system Voltage the lower the efficiency of the charge controller. It is not better to run 160 VDC array than 120 VAC across the 100 foot run. In fact if this is a 12 Volt system it is better to wire those 30 Vmp panels all in parallel to the MPPT controller (he'll probably balk at needing fuses) then to the battery then to the inverter and run the 120 VAC as per your inclination. Yes the AC is safer and easier to find switches/fuses/breakers for. Keep the DC low Voltage for Mr. Cheapskate.

14 AWG will handle 7 Amps on 120 VAC across 100'. 12 AWG will handle 11 Amps.

waynefromnscanada

Re: to run 110V AC or 160V DC ?

Re: "I am not in favour of HI DC voltage, it scares the hell out of me", I totally agree with you on that one.
As to dealing with tightwads who don't want to listen, well at this stage in my life Ive no more desire to spend time trying to get that class of people to see the light. I tend now to shut my mouth, walk away and let him hang himself so to speak.

Cariboocoot

Re: to run 110V AC or 160V DC ?

waynefromnscanada wrote: »

Re: "I am not in favour of HI DC voltage, it scares the hell out of me", I totally agree with you on that one.
As to dealing with tightwads who don't want to listen, well at this stage in my life Ive no more desire to spend time trying to get that class of people to see the light. I tend now to shut my mouth, walk away and let him hang himself so to speak.

Hmm. Must be a Canadian thing.

waynefromnscanada

Re: to run 110V AC or 160V DC ?

Cariboocoot wrote: »

Hmm. Must be a Canadian thing.

Hahahaha That and old age creeping up on us.

Cariboocoot

Re: to run 110V AC or 160V DC ?

Another thing which he probably won't grasp is that all four panels in series during one of our famous Winters will have a Voc so high you'd need a MidNite Classic 200 or 250. I'll just bet that isn't one of the "demo CC's" available. :roll:

ChrisOlson

Re: to run 110V AC or 160V DC ?

westbranch wrote: »

So here is the question, I realize that there would be less line loss @ 160V DC vs 110V AC but what additional costs are there going to be in running a Hi DC voltage line vs a Hi V AC line?

The additional cost would be in breakers/fuses and the proper service panels for it. DC power transmission is more efficient, even at the same voltage, than AC is, especially on really long runs where line capacitance becomes an issue. However, if you do use 160 VDC without the proper equipment, all I can ask for is please have a video camera handy when you get an arc going someplace, and be sure to post the video on YouTube so we can all enjoy it. :cool:
--
Chris

westbranch

Re: to run 110V AC or 160V DC ?

good one, maybe i should ask the proponent to throw the switch...;);) he does this (system design) for a living...

BB.

Re: to run 110V AC or 160V DC ?

A 160 Vmp-array with a Midnite ~250 Vmax input controller (depending on minimum temperatures) would not be a "bad thing". Just expensive.

If it is a "small system", put the panels and battery bank at the top of the hill--Get a MorningStar 300 WATT TSW inverter 12 VDC, program it for "search mode" and any time he has more than 6 watts down the hill, it will turn on (or he can try using a remote switch to turn on/off the 12 volt inhibit line).

If he stays with "12 volt battery bank" (to use the MorningStar 300 watt inverter), he will still need a ~50 amp minimum capable MPPT charge controller (MorningStar TS MPPT 45 or 60 amp controller; or one of the Outback/Midnite family).

The old question of 12/24/48 volt battery bank, inverter selection (and power options, or lack of them for smaller inverters in general) and the max current limit for MPPT charge controllers (limiting array size for "12 volt" battery bank support without having to buy a second controller as things expand).

-Bill

niel

Re: to run 110V AC or 160V DC ?

actually, if he's concerned about his money then he better start listening to viable solutions to his power needs or he will be spending far more with less than desirable results.

sit him down and make him go through the whole process starting with the loads and so on. start planning on paper what is needed/wanted and then throw it out to us to evaluate from what the daily loads are to what he wants/needs for the rest of the setup. wire run distances along with pv and battery bank size are just a few other things of many to kick around.

some things may be 6 of one and a half dozen of the other and in such a case he can be the deciding factor, but ultimately it will be his money whether to do this in a smart fashion or haphazardly.

Cariboocoot

Re: to run 110V AC or 160V DC ?

Hey! Who let the Americans in to the Canadian thread? Tourists!

But really, as you look at all the issues someone who doesn't want to spend the money had better go for the long run on AC not DC.

westbranch

Re: to run 110V AC or 160V DC ?

Ya right, probably headed North to get some sun....

We started the plan by establishing a wishlist of 20 - 13W CFL's that he wants, 11 of which are in phase 2 of the total system... he is currently adding on to his cabin.

I am plugging them into my spreadsheet and just have to determine the time-of-day and amount of use for each one.
He will be using 2 6V GC's (Trojan T145) for the bank to start ~250Ahr /C20

I am going to use 20W for each of the CFL's, though they are listed as 13 w my K-a-W meter gives them a PF of .55 and VA = 19 Comments re PFC??

based on the initial run of the final system he would use 806 Wh (~ 165%) of his available 500 Wh / day(3 days to 50% DoD) battery capacity, so we need to go over the estimated use to reduce consumption per day.

more to come, I seem to have explained him out of the 160V idea...

BB.

Re: to run 110V AC or 160V DC ?

More or less, use the Watts to calculate Battery Capacity and Solar Array sizing.

For VA (Watts/PF=VA), use that to size the Inverter, Generator, and wiring awg (generally, most inverters and smaller gensets are rated at Watts=VA (which ever is larger).

You may find larger gensets (and I have seen some UPS inverters) rated at, for example, 1kW or 1.5kVA (VA rating larger than Watt Rating).

-Bill

Cariboocoot

Re: to run 110V AC or 160V DC ?

Always go with the 'real' numbers from the K-A-W. Better to have "too much" power capacity than too little. Some CFL's have better PF than others.

(Ignore the Americans; as soon as they realize how expensive everything is up here they'll go back home. )

westbranch

Re: to run 110V AC or 160V DC ?

BB. wrote: »

use the Watts to calculate Battery Capacity and Solar Array sizing.

use that (VA) to size the Inverter, Generator, and wiring
-Bill

thanks for the confirmation :cool:Bill, that is what did here, consumption is in VA where available.

westbranch

Re: to run 110V AC or 160V DC ?

Cariboocoot wrote: »

Some CFL's have better PF than others.

Ya, I got some 19W/'100W' CFLs, full size from Calgary last year because they are PFC = .99. $16 each, delivered, still looking for similar cfl's.