Solar Systems

[Lightspeed]

(25 September 2013, 20:13)Skvez Wrote:

(25 September 2013, 16:58)Lightspeed Wrote: In mid winter, cloudy conditions what is the typical output you see from each of your 250W panels? I have to deal with quite cold conditions here and am trying to gauge expected power available taking account of reduced panel output and increased internal losses in the accumulators.

There are different technologies of PV and they vary quite a bit in terms of how much power they can create in winter but the short answer is expect in the region of 1% to 10% of full rating! (Yes it can be just a few percent)
Cold should actually improve the performance of the panels a few percent (of output, not of rated) but the batteries dislike cold more than the PV like it.
Increased losses in the system should be negligible.

Thanks Skvez.

Our new panels are moncrystaline, which I understand give best performance in cold and grey conditions. Hopefully we'll be seeing near to 10% of rated output and not just 1%. Time will tell.

[Nix]

Sorry Lightspeed, didn't see your post re query of winter usage!

As Skvez says, cold actually increases the efficiency of the solar panels but batteries don't like it so much...

During dark cloudy winter days, you're only going to be trickle charging at best. The lighter it is, the better it gets. If it's a sunny but cold winters day, you can actually do really well. I've recordered 1400W coming through my 1250W system!

[Lightspeed]

Thanks Nix

We're located at just under 2000" ASL and winters tend to be cold but quite sunny. The m=panel data sheets show a 0.48% temperature coefficient away from a standard data point at 25C. So in theory, at near to freezing point we will be seeing around 12% over generation. Of course the days are much shorter and the sun lower in the sky so we're not expecting miracles.

We also ordered the 125Ah Explorer batteries you recommended. They look awesome. My only experience with deep cycle discharge batteries is with a 60 AH unit that we liberated from some guys lamping illegally one nigh out on the field. That was 6 years ago. That battery is now being used by a friend for their emergency backup lighting, and its still going strong. We'll be mounting the batteries in the roof, immediately above a winter storage heater (gas vented to outside the house, assuming these batteries have an external vent tube?) The hope is that in this position they'll remain above freezing.

I'm looking forward to getting my hands on the new bits of kit, and am already thinking through requirements for a control panel to monitor status etc.

[Nix]

What's the power of your system going to be?

[Hex]

thanks for the post Nix ive been planning on a little solar system myself to run a few things in my greenhouse (and maybe the house if TSHTF) so this is a big help

question though, if i was going with a smallish setup would it be relatively simple and worth it to add in a second battery?

[Nix]

Hi Hex - in my view, the more batteries the better! You'll find that when the sun goes down, that's when you wish you had more in the way of battery back up power, but it's equally important to be able to charge a large battery bank. Balance is the key here plus how you're using it.

I've just added two more batteries to my existing set up and I still want more!

What size system are you planning? Plan correctly and it shouldn't be a problem adding batteries or PV panels as you.

[Hex]

good advice

i was looking at this panel and charge controler - http://www.amazon.co.uk/Photonic-Univers...J9GLO30OT6

and this inverter - http://www.amazon.co.uk/Ring-Automotive-...BYFZGLINIE

any good?

[Lightspeed]

(26 September 2013, 09:25)Nix Wrote: What's the power of your system going to be?

Much smaller than yours Nix. Its only 0.6Kw, and ahead of permanent or long term grid down failure we'll only have 150w of permanently installed generating capacity.

Why you are probably asking? Its because we had a big rethink about Opsec. We're located is in an isolated upland hamlet. I realised that on our comings and goings to the property I've been automatically scanning other houses in the area to assess their level of resilience and also to identify any features that would be useful to have in a post TU world....PV panels are fairly thin on the ground up here and big arrays stand out like sore thumbs. We realised that we are almost certainly not alone in sizing up other's property. This was brought home to us in the village pub a couple of weeks ago when general conversation focused on the new fangled alarm boxes that had been noticed on the house. So, although pleasantly surprised to hear that our activities were being noticed, we also decided it would be a good idea not to make too big an impression with a display of too much technology. Our original game plan has always been to keep the external appearance of the house kind of rustically dilapidated, while bringing its underlying structure and services up to an advanced level of preparedness. Our decision on PV is to have minimal discreet power generation permanently installed ( and in fact Location of the panel will no longer be on the roof but in an elevated position on a south facing wall out of sight from the lane, and protected a good deal from snow). with the remainder of the array on ground mount frames, stored out of sight ready for deployment as and when required.

Our intended use of PV electrical power will be for minimal emergency lighting, occasional work lighting, alarm/ perimeter monitoring, comms equipment, and occasional computer boot up for data and research, and in hot weather a small 12v refrigeration unit. The system will be standalone 12v with no grid tie. All connected emergency lighting will be low power LEDs.

[Nix]

Hex - ok, had a quick look at your two links. My own personal opinion is that you could do much better here. Easy spending someone else's money .For double the money, you can quadruple your pv intake (important!) and double the PWM controller ampage. The panel is MCS accredited too as a bonus. If you buy from Photonic Universe and I found they're a good supplier so no worries there.

Re inverter, you certainly don't want to go higher than 500 - 600W really cos then you're looking at some hefty cable, with 500W it's already needing 6mm cable. You are aware that this is a modified inverter, you can get much cheaper versions on ebay eg here

Lightspeed - top marks for having LED lighting, not many people appreciate how hungry incandescent bulbs are, or even these "low energy" bulbs! LED lighting is the way to go for any back up system, they're a God send. Can't comment on your comms power consumption but the alarm doesn't take much, usually much less than 5 - 8W without activation but keep in mind that it's on ALL the time and soon adds up over long winter nights. Computer consumption could catch you out, even a small laptop will use 50W or so. Fridge may also be power hungry depending on wattage so keep an eye on that one too as it's on 24/7.

[Lightspeed]

Cheers Nix,
I forgot you are an Alarm specialist.

Currently the whole thing is powered from 220v through a switch mode PSU down to 12v. The main control unit having its own internal backup nicads that will keep it live for 6 hours or so in event of mains power failure. Using an 5 in relay in the mains driven supply line, I'll be able to set it to fail-safe to the 12v PV system. So, while we have mains power the alarm runs from that. Only of we suffer a power cut will the PV derived backup power kick in. If we go grid down for an extended period, we'll wheel out additional generating capability to keep supply and demand balanced

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Oops that reads wrongly.

The relay will be powerd by 12v that comes from the PSU. If that voltage fails the relay drops out, connecting 12v from the PV storage batteries. When mains power is restored, the relay is reenergised and power to the alarm automatically switches back to the mains driven source