Designing an off grid solar sustem

bfath

Hello,

I am looking for some help designing a simple off grid solar system. My mother in law is building a small off grid house on an island in the Pacific Northwest (British Columbia, Canada). I am a red seal journeyman electrician with 15 years experience so the wiring and installation of the system is a no brainer for me, but as far as designing a system to meet her needs is where I am lost. Her budget is modest at best, so cost is definitely a factor though both her and I understand that purchasing a system that meets her needs is of the upmost importance. Here is a little background on her situation:



The house is 800 sq/ft

Location is the PNW so lots of cloud and rain, especially in the winter months

She will live there full time, by herself, and will be very power conscious at all times

Heat is by wood stove, as is her range/oven so no power usage there

She would like the fridge to be DC since it will be the only load to run all the time

All other major loads will be gas powered (hot water tank, etc)

System will include a small backup generator in case of emergency



So with this all being said, her power consumption should be quite low. All lights will be small wattage LED (eg. 6-12w each) and there will be 10-12 lights. Any other power usage will be intermittent (kitchen appliances such as a blender, etc.), as well as charging a cell phone and laptop and that would be about it. Here is where I have some questions.

Should lighting be AC or DC? I was leaning towards AC as to keep costs down with smaller gauge wire and cheaper light fixtures but does this reasoning make sense?

Should there even be DC anything inside the house? She was thinking she might like maybe a DC outlet or two, DC ceiling fan, DC composting toiler, and even the DC fridge. Pros and cons? Again with trying to keep costs down, having both AC and DC runs in the house would require 2 electrical panels (one AC, one DC) as well as the larger gauge wiring for all the DC runs (10 gauge stranded?)

Those are really the only questions I have in regards to the actual wiring of the house itself, its after this that I am a bit confused. Here are my questions to the solar side of the project.



How many solar panels required and what size to meet her needs? I know not all panels are created equal so since she is in a colder wet and cloudy climate what type is best to keep her going even during the dark winter months? What brands are best and most cost effective?

How many batteries and what size etc and wired for 12v, 24v, 48v?

Charge Controller size and type as well as Inverter sizing and type?

Any additional equipment needed or recommended?

I see online a bunch of “all in one” solar kits that include panels, controller, batteries, inverter, etc are these the way to go or is it better and cheaper to purchase specific brands separately? Can anyone recommend a specific site or wholesaler to deal with? (keep in mind we are in Canada so shipping to Canada is a must).



Basically I am asking for help designing the whole system she would need to be comfortable and worry free including electrical specifications and recommended brands and products. Thank you for your time reading through all this and I look forward to all of your replies and help moving forward with this project!



Brad

mike95490

The generator will be run a lot in the winter.  PV panels only produce useable power in direct, full sun.  On a cloudy day, my 5Kw PV produces less than 500w.  Further north, with even shorter days and you are looking at needing 2kw in panels to minimize generator time. The good news is the little EU 1000 really sips fuel and can run a small battery charger too. May not be able to start a fridge, may need the EU2000 to start fridge.
Fridge, I would say AC, buy a decent size, energy star fridge  for 1/3 the cost of a DC fridge and have frost free convenience. 
Adding a fridge to a system with any other loads, and you are looking at least a 24V system (4, 6v-200ah golf cart batteries in series)
Inverter, should be 1.2KW- 1.8W range, to start fridge and run other appliances.
Beware the compost toilet, most use a 800w+ heater to evaporate liquids, some manage with a 20w vent fan. The 20w fan can be replaced with a 5-10w fan, still move air, but less battery drain.
Where does water come from ?  Melted snow,  spring,  well pump - what's its power need ?

Dave Angelini

You really need to define what a modest budget is before you go much farther. 

bsolar

lights are nothing, you can get ultra low draw screw in led bulbs for regular ac fixtures .. im a diy'er so i go against the grain (disclaimer) .. but i would agree you need at least 4 200ah batts if a fridge is involved and probably (8) ~160w panels, 2 ~40w pwm chargers( i'd use poly panels myself and add 4 more panels and another charger for every pair of batteries you add) , and a 2500 watt sine inverter - i'd keep everything 12v 'myself' - proper setup and panel type works for me on that  - water is the wild card, mine runs on 12v but it took some 'engineering' to set it up which wasnt exactly cheap .. anyway yeah ..

mvas

Seattle Washington (PNW), kWh/m^2/day, panels facing south 
Jan   = 1.70  <<< !!!

Feb  =  2.81

Mar  =  3.54

Apr   = 4.17

May  = 4.57

Jun   = 4.78

Jul    = 5.23

Aug  = 4.71

Sep  = 5.21
Oct   = 3.15

Nov  = 1.97  <<< !!!

Dec  = 1.53  <<< !!!

westbranch

Do your shopping at ''home'' if possible or as close as you can get ...  there are a few good shops across the province, try WEGO solar on the Island, a couple of outlets last time I looked.  Import duties are a bug bear, and pump up the prices a good 30% plus... and Wholesale Solar in Kelowna.
Agree with needing > 1500W of PV for the fridge...  compare the costs of a DC fridge and heavy gauge wires to the cost of an off-the-shelf price in the big box stores for a new ~ 18 Cu ft fridge PLUS PSW inverter, I use a Cotek 1500W and it is a workhorse... there is a BC distributor, see their web page.
I would go with a good 30A min. Charge controller and Grid tie panels, they are selling < $1 per watt in Williams Lake...
good luck

Estragon

When I did my system a few years ago local Canadian pricing was roughly 2x what our sponsor sold for,,so I imported. No issues with duties, just sales taxes (which apply in any case) at the border. Local pricing seems more competitive now though.

The thing with coastal BC in the winter is there can literally be 40 days of dreary weather, a couple of sunny days, then weeks of more rain. The generator will have to be more than an emergency item. I'd suggest a decent stationary generator designed for continuous duty, plus something like a honda eu2000i, unless winters in Arizona is in the cards.

I would stay away from all-in-one kits. The key to getting a system that works for you is to really understand the trade-offs and design something that will meet your specific needs. If there happens to be a package that meets those needs after you've hone through the design process, that's great. If you buy one because it's easier than going through the design process, you're likely to be disappointed.

The design process starts with loads. It's easy to forget something like a water pump, which can radically change the design.

If grid is available, it would be a good idea to get a price for getting it.