[AllanG]

Last year we had here in Portugal a harsh winter with several consecutive days without clear sun.

Okay, I've decided I'm moving to Portugal!

Alan's right, here in my part of the UK about 400 miles south of Northern Scotland, although it is not always "bad" weather we can have several consecutive *weeks* without good sunshine in a *normal* winter...

In December last year I began operating my Weatherduino. The pcb is housed in a small watertight enclosure at the top of a ~4 metre pole next to the garden shed. A power wire comes from the pcb into the shed. I do not have electrical power in the shed so have been using 2 SLA batteries for power, charging one in the house while the other is in use. A 7Ah battery fully charged lasts 6 days before it falls to 11v and a 2.3Ah lasts 2 days. (I don't have a fan attached to the WD)

Last week I bought a (PWM) Controller and a 50W 12V solar panel which is mounted horizontally on the shed roof. Right now it is charging the 7Ah battery but I am going to buy a "leisure battery", the type used in caravans and mobile homes, with a capacity of around 70 to 100Ah. As well as powering the weather station of course, I hope to power 12v lighting in the shed and occasionally also some 12v garden lights. I'm sure this will work well during the summer months but it will be interesting to see how well it will work in the winter. If necessary though, as Alan has pointed out it will be relatively easy to "top up" the battery using an external source. As the solar panel on the shed roof is very accessible, I will try elevating it to an angle of around 45 degrees during the "darkest" winter months, probably around late November to February. (It is interesting that almost all the solar panels I've seen which operate illuminated roadside signs are inclined by something like 25 - 45 degrees.)

Regards,
Allan (another one!)

[hornychz]

Hi,

And let me even some notes for discussion:

On the training taught me that we in our country (CZ) should start with an inclination of 30° and later try a different slant, because the ideal slope is really difficult to determine:



But what is important: advised us instead of one large panel to use of more small (in the same way and crumbled eg. supply house). But most importantly - these panels not to route directly to the south, but half to the southeast and another half to the southwest. (Of course, you can conveniently use another configuration in multiple directions.) The reason is a higher energy gain in the morning and afternoon (evening) hours, when is less sunshine. Energy gain curve is much flatter, and then when there is "smart" installation, the integral of the gain curve is the same (or maybe higher) as with the "normal" routing of the panels to the south. Energy supply is also a "smoother". (And unlike photovoltaic power plants are for to produce as much energy at noon (for sale), these instalalation can better charge our batteries and power our devices.):



(I apologize for my terrible English.)

Regards

[hvalentim]

Some software tools you may find useful, reposted from elsewhere. These will allow you to use data sets specific to the equipment (solar panels, regulators, battery etc...) and location (reliable weather data) you are planning to use to test performance over the year and evaluate your needs.

PvSyst
http://www.pvsyst.com/en/software/download
Fully function evaluation mode, limited to 1 month.
If the locations included by default are not suficient (unlikely), you can grab Meteonorm to get data for a location closer to you.

Meteonorm
Dataset of weather conditions over the years for specific locations around the globe (airports, official weather stations etc). These can be interpolated and averaged so you can have an idea of a "typical year" and "best case" - "worst case" scenarios.
http://meteonorm.com/en/downloads
Works in a demo mode for an unlimited period. Saving is restricted to five sites.

Instructions on how to import data from Meteonorm to PvSyst:
http://files.pvsyst.com/help/meteo_import_meteonorm.htm

PV*SOL
Of course, the sherry on the top of the cake would be using PV*SOL, which allows you to draw a 3D simulation of your installation (including the surroundings, buildings, shadowing - say the effect of that chimney which will be casting a shadow on late afternoon...).
http://www.valentin-software.com/en/prod...ol-premium
Offers a featured restricted demo.

Lately, it seems they moved the design of stand-alone systems to a separate app:
http://www.valentin-software.com/en/down...standalone

Overall, cost wise, for a stationary photo-voltaic system old fashioned lead acid flooded batteries are likely still the best option. Just don't design the system to take more than 50% out of them (valid as well for all but lithium models).

[AllanG]

Zdenek, thank you for the very interesting information, there is obviously a LOT to consider when planning even a small solar installation! I guess one option for a small single panel that has not been mentioned is to mount it on a moveable frame and constantly track the sun / brightest light, although it would then need more electronics and mechanical components like motors and gears which would use some power itself and increase the possibility of something failing, especially during very harsh winter weather.

I will certainly experiment with different angles once I have properly set up my panel and larger battery. If I do need more than one panel in the future I will also consider setting them at "south west / south east" instead of both facing south. As I am quite a lot further north than you are though, it may not be quite as useful in the winter as the sun here will be a little lower in the sky?? Very interesting though and worth some experimenting!

Please do not apologise for your "terrible" English, it is not terrible at all and most importantly I understood perfectly all you said. I am ashamed to say that if we had to communicate in Czech, all I could say to you would be ahoj, prosím and Děkuji - oh yes, na zdraví too - it is worrying how many languages I can use to raise a beer. Thankfully most people we've met on our visits to Prague speak English but learning to say "please" and "thank you" in your language seemed polite and the right thing do.

Na zdraví,
Allan.

---

Overall, cost wise, for a stationary photo-voltaic system old fashioned lead acid flooded batteries are likely still the best option. Just don't design the system to take more than 50% out of them (valid as well for all but lithium models).

Yes, good quality ~75Ah "leisure" batteries I mentioned are available here in the UK for about GBP 65 / USD 100 and seem to last for quite a long time. I too have seen the importance of not draining below 50% - I have just noticed this on a website a few minutes ago, note the "70 cycles at 50% depth of discharge" :

A premium quality sealed leisure battery that gives you reliable high performance under continuous cycling.
•NCC Class 2
•Suitable for 2 – 4 berth leisure vehicles
•General auxiliary use
•Sealed
•Suitable for Motormovers*
•On Grid / Weekend Vacations
•Up to 40% extra power
•70 cycles at 50% depth of discharge
The Platinum Leisure Plus Battery S6110L has been specifically designed to cope with continuous cycling, whilst giving the highest performance and durable, reliable long life for all caravan/motorhome applications.

Regards,
Allan.

[hornychz]

Overall, cost wise, for a stationary photo-voltaic system old fashioned lead acid flooded batteries are likely still the best option.

Strongly agree

[hornychz]

I am ashamed to say that if we had to communicate in Czech, all I could say to you would be ahoj, prosím and Děkuji - oh yes, na zdraví too - it is worrying how many languages I can use to raise a beer. Thankfully most people we've met on our visits to Prague speak English but learning to say "please" and "thank you" in your language seemed polite and the right thing do.

This is finally the right topic!



Regards

[cjthomson]

Hey everyone

Thanks for the input!

There is definitely a lot to consider and I suspect my plans will change with a bit more research. I live in Forres which is only a wee bit further North than (and west of) Aberdeen.

This is the first time I've every done something like this so I'm learning as I go along.

I do agree with Alan in that I should probably be looking at a simpler setup. From a cost point of view and their general availability I am leaning towards a lead acid battery.

My shed faces South Southwest (or there about) and my intention is to have the panel mounted on the roof of my shed at an angle rather than horizontally, based on what I'd read elsewhere it seemed sensible have the panel at an angle - the best angle is still to be determined but 35 degrees may be a good starting point.

I am going to use a step down module to help reduce power consumption as per the suggestion here http://www.meteocercal.info/forum/Thread...gnal-range and will definitely not be using a fan in the radiation shield.

But what is important: advised us instead of one large panel to use of more small (in the same way and crumbled eg. supply house). But most importantly - these panels not to route directly to the south, but half to the southeast and another half to the southwest. (Of course, you can conveniently use another configuration in multiple directions.) The reason is a higher energy gain in the morning and afternoon (evening) hours, when is less sunshine.

I had not considered this but it makes sense however as Alan said it may not be as useful in winter this far North because the sun is so low in the sky in the first place. I will look in to this more as it may be worth experimenting with this setup.

Chris

[hvalentim]

For a permanent 1w consumption with an optimal winter tilt of 66% (facing South) and assuming an unobstructed horizon with a 5% chance of Loss of Load (the system failing) using weather data from Aberdeen (SOC under 50% will stress/wear the battery in Dec.-Jan. Also there is a 1/3 likelihood of system failure in Dec. - see table in third pic.):

   
   
   

---

For a permanent 2w consumption with an optimal winter tilt of 66% (facing South) and assuming an unobstructed horizon with a 0% chance of Loss of Load (the system failing) using weather data from Aberdeen:

   
   
   

Personally, I would go for nothing less than the second option. At least a ~50W panel and a ~20Ah battery.

PS: Disregard the "cost" estimate. It includes an absurd amount for installation and maintenance costs.

[cjthomson]

For a permanent 1w consumption with an optimal winter tilt of 66% (facing South) and assuming an unobstructed horizon with a 5% chance of Loss of Load (the system failing) using weather data from Aberdeen (SOC under 50% will stress/wear the battery in Dec.-Jan. Also there is a 1/3 likelihood of system failure in Dec. - see table in third pic.):

---

For a permanent 2w consumption with an optimal winter tilt of 66% (facing South) and assuming an unobstructed horizon with a 0% chance of Loss of Load (the system failing) using weather data from Aberdeen:





Personally, I would go for nothing less than the second option. At least a ~50W panel and a ~20Ah battery.

PS: Disregard the "cost" estimate. It includes an absurd amount for installation and maintenance costs.

Hi Hvalentim

Thanks for providing that information, I think I'll aim for at least what you've suggested. December and January were the months I was most concerned about. I may even opt for a larger battery than 20ah.

I was looking on eBay at Solar Panels and found this,

50W 12v Solar Panel Kit

I'll keep looking around but I quite like the sound of this.

Chris

[hvalentim]

"Photonic Universe Ltd is a company based in London, United Kingdom."
"FREE UK DELIVERY"
Seems cheaper purchased from "source" (Inc. VAT £99.99).
50W 12V SOLAR CHARGING KIT WITH 10A CONTROLLER AND CABLE (GERMAN BOSCH SOLAR CELLS) FOR CAMPER / CARAVAN / BOAT
http://www.photonicuniverse.com/en/catal...-boat.html