Ideal small PV system

[davestreck]

I'm wondering if any of the more electrically savvy members would be willing to give me their thoughts on a small solar system. I've been doing a lot of reading, of both this forum and other sources, to try to better educate myself about how to get a system set up at our cabin in Nova Scotia, but I'm definitely no electrician, and the hard-won experience of actual users would be super helpful.

Basically I'd like a system that provides 300-500Wh AC per day, with a 4-5 day reserve, just enough for lights, cell phone charging and a laptop computer. An inverter with battery charging capability would allow me to charge the battery bank with my existing genny. I have good solar exposure on the south face of my cabin (it faces the open ocean) as well as quite a bit of wind energy available from the prevailing southwesterlies. I was given an Air-X marine wind turbine in perfect working order by a customer, but I'm not sure adding it just to add it would make sense. I could always just sell it on eBay.

I plan on fabricating a pole mount for the solar panels which can be bolted to the south side of the house, and building a battery enclosure against the west side, with system monitoring and AC panel on the inside wall. I'll then run standard wiring for a few outlets and fixtures. If I end up using the wind turbine, that will have to be placed about 80 feet from the cabin on a small (24' - 30') tilt up tower.

South wall (on the right in this photo):



What I'm looking for are specific product recommendations from folks who have actually used this stuff. I'd like to start getting the bits together so I can pre-build as much of the system here at home as possible, which will save time on my next trip north. Having to run to the hardware store every time you forget a nut or a bit of wire is time consuming when you're on an island!

Apologies if this question has been asked and answered a thousand times on this forum. I've been unable to find a system example that closely matches our requirements. Any help will be greatly appreciated. Thanks much.

[UK4X4]

Here are some cabin sized kits

you could look at and get some ideas

http://www.altestore.com/store/Packaged-Systems/Off-Grid-Cabin-Systems/c466/

[MountainDon]

Have you looked at and used the Off Grid Calculator available here at
http://countryplans.com/smf/index.php?topic=8192.0

I had a quick look using your value of 400 watt/hr a day, a 4 day reserve with max batt drain of 50% and came up with 4 6 volt golf cart batteries in series for 24 VDC system. You say good sun exposure but not how many useful hours. Have a look at that calc topic. There are links to sun maps if you do not already know the hours. Once that is known you can calc how many panels would be required to charge the batteries.

Being on the ocean I assume you also have winds that are better than most inlanders. If that is so, that AirX could be an ideal adjunct to the system. It will generate power when the skies are cloudy and the wind blowing. Wind and sun together make a good versatile system. I wish we had more useful winds. BTW, 30 feet minimum above obstructions gives best performance. If you run both solar and wind each will need it's own charge controller.

[Native_NM]

I'll add something based on family experience.  Make your system portable. My brother "lost" his panels at his place which is remarkably similar yours except his is way uglier. They ripped his panels clean off.   He finally went with a trailer mounted system on a cheap HF trailer ($300) and an enclosure for the batteries, inverter, etc.  The panels sit on the side on an aluminum mount.  The tongue weight is so low he can move the trailer to track the sun if needed.

There are a whole bunch of examples on YouTube. 

Solar panels are stolen all the time.  The systems the highway departments are using now get stolen at an alarming rate.

[davestreck]

I'll add something based on family experience.  Make your system portable. My brother "lost" his panels at his place which is remarkably similar yours except his is way uglier. They ripped his panels clean off.   He finally went with a trailer mounted system on a cheap HF trailer ($300) and an enclosure for the batteries, inverter, etc.  The panels sit on the side on an aluminum mount.  The tongue weight is so low he can move the trailer to track the sun if needed.

There are a whole bunch of examples on YouTube. 

Solar panels are stolen all the time.  The systems the highway departments are using now get stolen at an alarming rate.

Thats one of the concerns that I have as well, but this being an island cabin have no choice but to leave the stuff up there and hope for the best. We've experienced break-ins nearly every year since we built the shed. Mostly they just rummage around and leave, but on a few occasions stuff has gone missing (most notably the chainsaw...that hurt!)

Our policy since then has been to only leave gear up there that we can afford to lose. This PV system will be breaking that rule in a big way.

[davestreck]

Have you looked at and used the Off Grid Calculator available here at
http://countryplans.com/smf/index.php?topic=8192.0

I had a quick look using your value of 400 watt/hr a day, a 4 day reserve with max batt drain of 50% and came up with 4 6 volt golf cart batteries in series for 24 VDC system. You say good sun exposure but not how many useful hours. Have a look at that calc topic. There are links to sun maps if you do not already know the hours. Once that is known you can calc how many panels would be required to charge the batteries.

This map: http://www.renewable-energy-concepts.com/solarenergy/solar-resources/canada-solar-map.html gives our location's "Photovoltaic potential (kWh/kW) South-facing, tilt=latitude, Annual" as 1000-1100

This map (the second one on the page): http://www.survivalunlimited.com/solar_misc/solarmap.htm gives me an "insolation value" of about 2.4 kWh/m2/day, which (if my math is correct) works out to 1.55 wH/sq in/day (1 square meter being 1550 square inches) This sounds weird, and doesn't seem to gybe with the first map, which gives coastal Maine (which is close to Nova Scotia) a value of 3,400 Wh/sq in/day. My head is starting to hurt. I need to do more reading.

[davestreck]

Have you looked at and used the Off Grid Calculator available here at
http://countryplans.com/smf/index.php?topic=8192.0

I had a quick look using your value of 400 watt/hr a day, a 4 day reserve with max batt drain of 50% and came up with 4 6 volt golf cart batteries in series for 24 VDC system. You say good sun exposure but not how many useful hours. Have a look at that calc topic. There are links to sun maps if you do not already know the hours. Once that is known you can calc how many panels would be required to charge the batteries.

Oops. After more reading I realized that I completely miffed my previous response. Based on the solar maps I'm checking, and considering the cabin is intended for summer-only use, I'm going with 4 hours usable sunlight per day.

Have you looked at and used the Off Grid Calculator available here at
http://countryplans.com/smf/index.php?topic=8192.0
30 feet minimum above obstructions gives best performance. If you run both solar and wind each will need it's own charge controller.

According to the Air owners manual, my 12V turbine needs no external regulator. It uses internal braking to slow the blades and is set from the factory to deliver 14.1 Volts. However, the regulator is user adjustable, and can be set "wide-open" to deliver 17.8 volts, in which case an external regulator is required. The owners manual says that this option is provided to make the electricity "look like its coming from a solar panel"

Also, I'm assuming that a "regulator" and a "charge controller" are the same thing in this instance.

As far as turbine height, 80 feet from the cabin puts the tower here, already 50 or so feet above sea level and facing the prevailing winds:




I'm thinking the tower only needs to be tall enough to keep the spinning blades from decapitating anyone walking by.

[Windpower]

I had an AirX operating for several years with good results

I did loose one blade to a bird strike but otherwise trouble free

If you have a good wind site (average 10 mph or better), the AirX can supply about 20 to 30 KW-Hr per month

mine basically kept a full sized fridge running  

I plan to put a "Danger high voltage 480 Volts" sign up with  an electric fence to reinforce the warning

[davestreck]

If you have a good wind site (average 10 mph or better), the AirX can supply about 20 to 30 KW-Hr per month

mine basically kept a full sized fridge running

Just based on my experiences there over the past 6 years (no scientific data), I'd guess we have a good to better-than-good wind site.

AC or DC fridge? I had planned to go for a propane fridge when time and money allows. Maybe I can rethink that.

[Windpower]

it was a standard full size AC fridge run from an inverter

[Windpower]

here is another on line calculator for PV

http://www.wholesalesolar.com/StartHere/OFFGRID/OFFGRIDCalculator.html

beautiful place you have !

[davestreck]

here is another on line calculator for PV

http://www.wholesalesolar.com/StartHere/OFFGRID/OFFGRIDCalculator.html

beautiful place you have !

Thanks.

I finally installed OpenOffice so I could play around with MountainDon's PV sizing spreadsheet. Great resource! I still need to do more research as far as system components, but it looks like for 400Wh per day with 5 days of backup power I need 2 Sharp 123V panels and 4 Trojan CB6V-AGM-GC2 batteries (200Ah) That alone brings me up to $2400. Still gotta add all the rest of the bits: inverter, charge controller, etc, etc. Gonna get pricey!

[Windpower]

good prices on panels here


http://www.sunelec.com/solar-panels-c-5.html

[Native_NM]

These are cool:

http://www.grainger.com/Grainger/XTREME-POWER-Remote-Power-System-2KGT3?Pid=search

[davestreck]

good prices on panels here


http://www.sunelec.com/solar-panels-c-5.html

Good link.

I love tinkering with that spreadsheet. If I can keep my power requirements to about 300 Wh/day, I can get by with a single 190W panel ($254.60 from sunelec.com) and 2 210 Amp Hr batteries ($232.00 each from wholesalesolar.com), giving me 3 days of reserve power.

Anyone have any inverter recommendations? I'd like one with a battery charging feature so I can use my genny as a backup.

Off to do more internet scrounging...

[Tickhill]

Dave, I have bought panels, and an Outback FM-60 from sunelec.com with no damage in shipping. That was my biggest concern was damage of the panels but all was well. I had bought some used panels on eBay and the first one arrived shattered. Love the cabin and the location. Good luck, Tickhill

[Squirl]

Ok. I may be the odd man out here, but I recommend two Harbor Freight systems. They are not the best, but they should suite your needs.  I have one for my 8x12.  http://www.harborfreight.com/45-watt-solar-panel-kit-90599.html

First they are low cost.  They are less likely to walk away and if they do, it doesn't hurt as bad.   Second, you might be able purchase locally to save on shipping or they can be shipped standard mail, not freight like most solar panels.  Freight shipping can add $250 to your single solar panel.  I'm not sure how this is affected by international shipping. Third, I would go with 12v for such a small system.  It is much easier and cheaper to find DC equipment for 12v because that is the standard for RVs, boats, and cars.  Since you aren't talking about a lot of watts you should have to worry as much about wire sizing.  

The handiest thing I found about the kit is the control box.  With a chart I can know what my battery voltage is and how much power I have.  With the 12v plug, I can plug my small inverter or any of my car equipment right in and not have to have double the equipment or have conversion losses from DC to AC and back to DC.  The two 5w DC lights are the lights for the 12x8.  I was surprised at how little power I used.  I don't use the laptop much because I only have internet on my phone.  I only use the lights when I am inside and awake when it is dark.  Which, in the summer is rare, because I am early to bed and early to rise.  I spend most of my time out and about.  I actually only go through about 150 watts a day.

So for your original post (laptop, cell phone, lights), I think this system would more than meet your needs.  They are almost always "on sale" from HF.  You can also find coupons for an additional 20% off or the kit for $150 in the back of magazines like Field and Stream.  So for around $300 you could get 360 watt hours a day (4 hours X 90 watts) and everything you need except the inverter and batteries.  If you are planning for a refrigerator or expanding usage, the systems posted by others would be better.

[davestreck]

Ok. I may be the odd man out here, but I recommend two Harbor Freight systems. They are not the best, but they should suite your needs.  I have one for my 8x12.  http://www.harborfreight.com/45-watt-solar-panel-kit-90599.html

First they are low cost.  They are less likely to walk away and if they do, it doesn't hurt as bad.   Second, you might be able purchase locally to save on shipping or they can be shipped standard mail, not freight like most solar panels.  Freight shipping can add $250 to your single solar panel.  I'm not sure how this is affected by international shipping. Third, I would go with 12v for such a small system.  It is much easier and cheaper to find DC equipment for 12v because that is the standard for RVs, boats, and cars.  Since you aren't talking about a lot of watts you should have to worry as much about wire sizing.  

The handiest thing I found about the kit is the control box.  With a chart I can know what my battery voltage is and how much power I have.  With the 12v plug, I can plug my small inverter or any of my car equipment right in and not have to have double the equipment or have conversion losses from DC to AC and back to DC.  The two 5w DC lights are the lights for the 12x8.  I was surprised at how little power I used.  I don't use the laptop much because I only have internet on my phone.  I only use the lights when I am inside and awake when it is dark.  Which, in the summer is rare, because I am early to bed and early to rise.  I spend most of my time out and about.  I actually only go through about 150 watts a day.

So for your original post (laptop, cell phone, lights), I think this system would more than meet your needs.  They are almost always "on sale" from HF.  You can also find coupons for an additional 20% off or the kit for $150 in the back of magazines like Field and Stream.  So for around $300 you could get 360 watt hours a day (4 hours X 90 watts) and everything you need except the inverter and batteries.  If you are planning for a refrigerator or expanding usage, the systems posted by others would be better.

Thanks for the reply.

I've been back and forth on the "quick-n-dirty" vs "top shelf and pricey" debate. Part of me just wants to pick up one of those HF kits and give it a try. My problem is that I hate having to re-do things down the road. Having a system that will only give me a couple of years of reliable operation (if that...those HF components look pretty crappy) means that in a couple of years I'll have to take it all down and haul it back off the island, then go through another complete install. Buying quality gear minimizes (I hope) the chance of having to do that. Carrying stuff to the site (it all comes on our backs) is hard enough the first time! My wife is constantly on me not to spend too much on the cabin bits. The problem is, when she buys something, its the absolute cheapest version available and invariably ends up in the trash (back on the mainland!) the following year.

Regardless of the route I decide, I'm definitely including an inverter, since I plan on wiring the cabin for 120V AC.

Down the road I would like to be able to expand the system (more PV, more storage) depending on how our usage plays out.

The possibility of the system "growing legs" does concern me, and a stolen $500 system is a lot easier to swallow than a stolen $3000 system.

I still haven't decided. Since I think my 2011 trips are done, I have the better part of a year to make up my mind. Meanwhile I just keep monkeying around with the MountainDon's PV Calculator. Good fun!