Lighting

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Lighting

Postby Windy » Mon Aug 19, 2013 3:16 pm

What do people think about running dc power for LED lighting or Ac for lighting in a off grid system, which do people think is best.
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Re: Lighting

Postby FarmerJohn » Mon Aug 19, 2013 5:17 pm

Windy wrote:What do people think about running dc power for LED lighting or Ac for lighting in a off grid system, which do people think is best.


It depends on what you have already.

My place was wired for a/c already so retrofitting DC lighting would have been a pain for me because you need to change the switches to ones that are rated for DC loads, also SWMBO likes the dimmer switches, so I would have needed to rewire.

If I was starting out from scratch, I would be going down the DC route for lighting and even some DC sockets for things like computers, TV's, a hard wired outlets for DC fridge/freezer etc etc.

In the end, I just put the whole house on an inverter and sized in the solar to allow for the conversion inefficiencies. The extra panels are cheaper than rewiring.

All my halogen lights were removed and LED's put in thier place. Some of the powersupplies needed to change to make them work nicely, but they do, and they dim, and so I get fed ;)
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Re: Lighting

Postby davidg » Mon Aug 19, 2013 9:30 pm

FarmerJohn wrote:If I was starting out from scratch, I would be going down the DC route for lighting and even some DC sockets for things like computers, TV's, a hard wired outlets for DC fridge/freezer etc etc.

I seriously considered doing just that for our farm house, with the run lengths involved it drove up the cost so much any potential advantages were just not there, the minor losses involved in using a SP-Pro 240Vac inverter were not really an issue, it became much more advantageous to simply factor in the SP-pro and get the much greater flexibility and simply use 240Vac on much lower lines losses.

FarmerJohn wrote:So I just designed the whole house based around the inverter and sized in the solar to allow for the conversion inefficiencies. The extra panels are cheaper than rewiring.

:) I don't think you lost out anywhere doing it that way inverters are so much more efficient if using good ones now that the losses involved are minor with really good battery inverters that it does not really matter.
When I did my calculations and maximum demand it was less than 1% difference. I went with all AC as a result, saves a lot of money on wire sizes alone, basically 1 or 2 extra panels more than offsets the losses, minor cost.
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Re: Lighting

Postby Windy » Tue Aug 20, 2013 12:07 am

The house is still in planning and will be off Grid
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Re: Lighting

Postby Gordon-Loomberah » Tue Aug 20, 2013 9:52 am

Even if you are still in the planning stages, I'd suggest going with 230V everywhere. I thought about a separate 24V circuit for lighting here for a while, but decided against it for a few reasons, including the larger wire sizes required and the need for expensive DC rated switches and CBs. Also, the 24V supply is not regulated, whereas the 230V from the inverter is. A 24V LEad-acid battery can vary between~24V and 31V (12V battery from ~12V to 15.5V) under different conditions of charging and temperature, which could lead to LED failures unless additional regulation was included between battery and light circuitry.
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Re: Lighting

Postby FarmerJohn » Tue Aug 20, 2013 11:50 am

davidg wrote:I don't think you lost out anywhere doing it that way inverters are so much more efficient if using good ones now that the losses involved are minor with really good battery inverters that it does not really matter.


I have concluded that this applies in most full-time domestic situations. If you were building a cabin or something like that, there may be a case for DC.

My current inverter is a reasonably good one. It is a Victron Multiplus 5000va 24v, courtesy of Energy Matters/Apollo Energy. It has a 120A charger and a 50A transfer switch. This inverter has a "peak" efficiency (if I recall correctly of over 94%), but according to my testing you only ever see peak when its under substantial load ( 2-3 kw +) from large well charged batteries.

I don't run loads like that for hours on end - but one does have to provision for the peak loads.

What tends to happen is that I am running background loads most of the time of around 180-200w, with the odd start peaks from the fridge and freezer compressor. This is not so efficient, in fact, my measurements show the efficiency is less than 80%. In my scenario it is irrelevant because of decent battery size and 3.75kw of panels, but if you were trying to minimize the system size for budget reasons, it would matter.
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Re: Lighting

Postby Tracker » Wed Aug 21, 2013 9:28 am

...What tends to happen is that I am running background loads most of the time of around 180-200w, with the odd start peaks from the fridge and freezer compressor. This is not so efficient, in fact, my measurements show the efficiency is less than 80%....


This is a problem that I noticed, some time ago..
We select inverters, based on maximum power...
I had thought that a good plan would be to use a SMALL inverter, running at capacity, for lighting, thus giving peak efficiency.
The dream is to have an AC coupled system, where there is a series of inverters, small, medium, large...
That are switched in, thus each working at peak efficiency ..

Yes - all a bit naive...

So, for lighting, would it be more economical, just wiring for 240v and use a dedicated inverter..operating near peak efficiency..
Our problem is time and change.. technology changes SOoo much and so fast.. but, a 240v light will always be around, no matter what technology it employs...

I suppose that when planning a total house system.. it becomes a battle of keeping total efficiency up..

Removing lighting to a separate inverter, means you have reduced the BIG Inverter load, even more.
At least, you know that that power consumption is efficient ..
..
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..
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Re: Lighting

Postby FarmerJohn » Wed Aug 21, 2013 10:59 am

Tracker wrote:So, for lighting, would it be more economical, just wiring for 240v and use a dedicated inverter..operating near peak efficiency..


Yes! Good point.

Were it not for the fact I overlooked that possibility when trenching in the cable from the inverter shed to the house, this is what I would have done - (also I never looked at the rules to see if that was possible in AUS, in the UK there were special rules for the insulation you must use for cabling if you have more than one phase in the same house and if those cables were going to be closer than 1m of each-other (this is from memory and could be wrong), I don't know about here - maybe all the cables are sufficiently well insulated)

Not only that, but for lighting you could be more confident in using the energy saving modes of the inverter, where they stay shutdown until there is a demand.
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Re: Lighting

Postby davidg » Wed Aug 21, 2013 3:33 pm

Tracker wrote:This is a problem that I noticed, some time ago.. We select inverters, based on maximum power...

Well hows this then?

SP-Pro - SPMC 482AU (7.5kw continous)
Peak efficiency @
20% load 95%
30% load 97%
50% load 96%
100% load 94%

EU efficiency (average 5, 10, 20, 30, 50 &100%) much more conservative than peak = 93%

Still miles ahead of nearly all brands over the load spectrum or range. 8-). Even "small inverters" and certainly cheap ones don't match this level of performance. SPMC Spec sheet

Tracker wrote:I had thought that a good plan would be to use a SMALL inverter, running at capacity, for lighting, thus giving peak efficiency.

Good thought, but the efficiencies above are pretty easy to acheive in real life testing. Is it really worth all the mucking around? Am I biased ......... hell yes I'm biased. :lol: mind you SMA are close to this sort of performance as well, can't comment for any others, but this is what you are paying for when you get such products.


Tracker wrote:The dream is to have an AC coupled system, where there is a series of inverters, small, medium, large...That are switched in, thus each working at peak efficiency

Just spend the coin get the right product to start off with. It saves a bunch of money, time, wiring and complexity. It simplifies the installation reduces maintenance, makes it easier to fine tune an installation and get it to "now it's set and I can forget" , well amost you still have to look occasionally, even if for no other reason than to see it just humming along. It also make it much easier to get support for if it's really needed.

Of course if you do things like I do and delibrately make it do things to see what happens well then it must go into shutdown sometimes when you do nasty things to it in the name of testing :lol: :roll:

BTW Australian STD AS3000:2012 Clause 3.11.5 under Table 3.7 it reads

Exceptions:
1. Two or more underground wiring systems may be grouped together
where they are associated with the same electrical installation.


Hows that! :)
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An OTT Genset for a house.
PVOutput Stats

Sparkys light up your life :)
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Re: Lighting

Postby FarmerJohn » Wed Aug 21, 2013 3:49 pm

davidg wrote:
Tracker wrote:This is a problem that I noticed, some time ago.. We select inverters, based on maximum power...

Well hows this then?

SP-Pro - SPMC 482AU (7.5kw continous)
Peak efficiency @
20% load 95%
30% load 97%
50% load 96%
100% load 94%



Well, yes those are great figures. I can see why you like that product. You certainly get what you pay for.
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