My Solar Project

DavidOH · February 2011

This is what it looks like now. :cool:
Am I leaving something out?
Is this connected correctly?
What do you think?

icarus · February 2011

Re: My Solar Project

Fuses between the battery and the inverter/charger. Fuses between the Wind genny and the combiner box, fuses between the PV and the combiner box. I am no expert but can you run the wind charger and the Pv into the same combiner box and controller?

Why the 300 Amp fuse? How big a wind/Pv system are you going to build?

Cariboocoot · February 2011

Re: My Solar Project

Solar panels and wind turbines need separate controllers. The wind controller must have a dump load. Controllers connect to batteries, not inverter.

"300 Amp fuse" between disconnect and charge controller is misplaced. That sounds like a size for the inverter. Charge controllers will have fuses or breakers on their output to batteries. Since charge controllers are under 100 Amps it isn't likely to be that big. If there's more than 2 panels in parallel, then each needs to have its own fuse.

DavidOH · February 2011

Re: My Solar Project

The combiner box will contain breakers for each input.
1 per solar panel circuit, and another for the wind charger.
The wind charger I do understand won't go to the controller.

The 300 amp fuse was a "master fuse" or "system disaster"
You are correct this it a Trace "T" fuse and should go between the inverter and the battery.

I'll redraw and add a few more details. Thanks for you quick input!

DavidOH · February 2011

Re: My Solar Project

after a redraw it looks more like this:

Now I'll have to get a shut off for the wind charger.
The battery will have a disconnect. :roll:

Cariboocoot · February 2011

Re: My Solar Project

You're getting closer.

But again I must point out the charge controllers for the wind and PV's go to the battery, not the inverter. You don't want the charging current going to the inverter and then through its cables to the batteries.

It helps if you break the whole system in to separate circuits:

PV -> fuses/combiner -> disconnect -> charge controller -> fuse or breaker -> battery bank.

Wind turbine -> charge controller -> fuse or breaker -> battery bank.
..........................^ dump load

Battery bank -> inverter fuse -> inverter -> AC distribution.

Battery bank -> DC fuse block -> DC loads.

Generator -> inverter AC IN -> battery bank.

mike95490 · February 2011

Re: My Solar Project

Agreed, you have to have a controller /dump load/shutdown for the wind. or just forget the wind, unless you have to tie your hat on when you go outdoors.

DavidOH · February 2011

Re: My Solar Project

Yes, the wind charger is "optional" right now.
I thought I'd leave room to tie it in later.

Ok, so all DC input goes to the battery. Wind Charger, Battery Charger, Solar Panels
I'll fix that.

Keep the inverter on the "output" side.

DavidOH · February 2011

Re: My Solar Project

Here is the third edit:

This puts the battery in the middle, separating the AC to the left,
and keeping all DC on the right.

AC input may be a generator, or from the grid.

BB. · February 2011

Re: My Solar Project

The wind "disconnect" for many turbines may actually double throw switch... One way connects the turbine to the battery bank (charging). The other position shorts out the wind turbine to stop if from spinning (or to keep the speed down very low by shorting out the windings and stalling the blades).

The turbine mfg. should tell you what kind of shutdown circuit (and internal or battery shunt charge controller) they recommend using.

-Bill

samuel · February 2011

Re: My Solar Project

I'm not quite sure how to contribute to your diagram. Most of the information that I used to build a system relied on downloading and reading wiring diagrams from manufacturers. Xantrex had quite a few installation downloads available at the time. If you are still in the early phases of designing and/or researching I invite you take a look at a blog I've been working on :: offgridcabin It's mostly a collection of notes and photos from my experiences building an 810 W solar off the grid system.

Also, here is a post that has two links in it: one is a wiring diagram, the other is a complete part list

Cheers, Sam

Cariboocoot · February 2011

Re: My Solar Project

Samuel;

Welcome to the forum.

Nice documentation! Beautiful cabin!

Can you take some critique from an old guy with a 60-year-old ex-hunting lodge whose electrical system gets redesigned about every five minutes?

You've got a lot of battery for a 12 Volt system. I read your reasons for going 12 instead of 24, but in the end this may still be a mistake. Simply using larger wires doesn't eliminate the loss problem, it just reduces it. In the mean time the current use per Watt for AC is still high, and that is problematic.

I think you might want to use PVC or other plastic for venting your battery enclosure. Copper is not a good choice as it is conductive.

You've got the over-all analysis of wind correct. Especially the part about manufacturer's "optimism".

The biggest problem I see is the usual one: you are way under-paneled. Six 135 Watt panels is only 810 total: enough for about 430 Amp hours of battery. You've got 1540 Amp hours (far more than any 12 Volt system should have and more than should be made up out of 6V units in my opinion). What this means is early death for those batteries They are going to sulphate.

I might be reading this wrong; it's a very long and involved documentation! But I'd suggest you consider either reducing the bank size or upgrading to 24 Volt for "heavy" loads and retaining a small, separate 12 Volt system for you 12VDC. Do you really need 9 kW hours of battery capacity? That is huge for off-grid applications.

Maybe we can help you "slim down" your system and make it more efficient. There's some pretty smart guys (and gals) on this forum. Occasionally I'm one of them.

samuel · February 2011

Re: My Solar Project

Cariboocoot,

Very insightful. Unfortunately the only action I can take regarding a 12V system is to rationalize its existence. We're stuck with 12V because of our inverter. Time will tell how well the batteries hold - I'll consider myself forewarned in case they go early. So far, at 18 months, the batteries are all within manufacturer spec (water levels and specific gravity readings).

Our reasoning for a higher than normal battery to solar ratio is how we use the cabin. A typical stay is 2-5 days. We can run to 50% on the batteries in 3 days (particularly useful for winter sun). The purpose of the solar is to recharge the system in our absence and allow us to squeeze out an extra day or two in winter before having to fire up the generator. The cabin was occupied almost 150 days last year.

Heavy loads - that was my mistake. We should have used a 2000W inverter. Very rarely do we go over 2000 W - maybe once in every 40 days of occupancy. For those loads we could have simply used the 3000W generator on site. In fact, if there were a way to add a secondary, smaller, more efficient under small loads, inverter -- I'd be very willing to go that route.

Cariboocoot · February 2011

Re: My Solar Project

samuel wrote: »

Cariboocoot,

Very insightful. Unfortunately the only action I can take regarding a 12V system is to rationalize its existence. We're stuck with 12V because of our inverter. Time will tell how well the batteries hold - I'll consider myself forewarned in case they go early. So far, at 18 months, the batteries are all within manufacturer spec (water levels and specific gravity readings).

You're never stuck: all it takes is more money!

I bet you've tumbled to that already! The nice thing about going up in Voltage is that the current drops, so any wiring sized properly for the lower Voltage system can stay.

Our reasoning for a higher than normal battery to solar ratio is how we use the cabin. A typical stay is 2-5 days. We can run to 50% on the batteries in 3 days (particularly useful for winter sun). The purpose of the solar is to recharge the system in our absence and allow us to squeeze out an extra day or two in winter before having to fire up the generator. The cabin was occupied almost 150 days last year.

This is an "old school" way of thinking; that the very large bank will recharge over time from a small array. It does not work. We've had dozens of cases of it on this forum alone; suddenly you've got batteries with 1/10th the capacity they should have and the lights don't stay on for an hour.
In the old days when panels were really expensive and batteries were cheap it was okay to deficit charge and replace the batteries every 3 years instead of 9. These days the costs are reversed so it makes sense to give the batteries what they need and keep them going as long as possible.

Heavy loads - that was my mistake. We should have used a 2000W inverter. Very rarely do we go over 2000 W - maybe once in every 40 days of occupancy. For those loads we could have simply used the 3000W generator on site. In fact, if there were a way to add a secondary, smaller, more efficient under small loads, inverter -- I'd be very willing to go that route.

Yes indeed. Around here we don't recommend using 12 Volts for any system that will have to regularly supply 2kW. You just don't want to have 200 Amps DC running through the wires. Heat, you know. Causes problems.

I'd still recommend your blog as a good read for anyone contemplating an off-grid system. Mistakes and compromises are all part of the process, and you've done an excellent job of documenting it all.

One other thing. I don't notice a battery monitor on your parts list. That might be a really good idea, given your panel/battery ratio. Very good for keeping an eye on things. Monitors: http://www.solar-electric.com/metersmonitors.html

samuel · February 2011

Re: My Solar Project

Cariboocoot,

I'm taking notes. I'm glad to glean any tips - I was pointed in the right direction on building a battery box in another forum. A battery monitor has been contemplated. It may coincide with a future project to run a small 12V line from the garage to the cabin. This line would tie together a 12V motion sensor from the garage (which scans the drive way) to a LED light in the cabin -- when tripped, the lights on the garage and one in the cabin would turn on. Because this project would require an additional trench to the cabin I've been waiting to look into battery monitors.

Sorry, I forgot to address using copper pipe around the battery bank. I discussed it briefly on the diagram on my blog. Copper ventilation pipes utilize a principle used in heating and cooling. By opening to the outside air (which could be 80°F) and the inside of a building (say 60°F) a draft is created - like standing in the doorway between a hot and cold room. By using a conductive vent this draft can be stabilized. Drafts concern me because they can create swirling air, which could become a sort of pocket for hydrogen. The pipe is not grounded, so accidental contacts by battery cables would not cause damage unless two cables contacted the pipe at the same time.

Thanks for info - I'll be revising my criticisms section in the near future.

DavidOH · February 2011

Re: My Solar Project

That's a great build Sam. Very similar to what I am working on.
I agree on the 24v for a larger system.
I recommend that you start your own thread here. Others will notice and comment.

Mine is limited to about 500 watts. It's for the cabin in the picture. Hardly a full sized home, but it's for 24/7/365 living.

NA W&S recommended that I run the panels separately rather than use the connectors as you did. So it's four cables into a breaker box instead of one.
I'll have a parts list soon. Much of the Trace components I got off of eBay years ago. They were display models and/or slightly used and all look new.

I am getting as many items as possible to use 12v so I may not need the inverter.
I'll just go with a much smaller one for the refrigerator and a few items.

The Kill-A-Watt meter was great for checking what I use. That helps plan out what I can change to keep everything sized to fit.
See my other thread on the Low Power PC. You might consider power use before buying any future items.

DavidOH · January 2013

Re: My Solar Project

Looking at my diagram again I think I should make a slight change.
I think that ALL of the Dc should go through the 300 amp disconnect.
All DC loads should connect in the same place including the inverter.

Attachment not found.

BB. · January 2013

Re: My Solar Project

It sort of depends... You want to protect wiring--So a 300 amp breaker on the battery main may make sense.

On the other hand, look at your failures. There are multiple charging sources, and if one of them fails, you probably would not want it to take out all charging sources (I have seen a 120 watt flood lamp fail with a quick short, the 15 amp breaker did not trip, but the 120 amp main did).

Also, there is an issue with charging sources that have "uncontrolled" voltage output. A solar panel may run at ~17.5 volts, but fail "open" at ~21 volts. High for a 12 volt load, but not an end of the world event.

A wind turbine, on the other hand, could generate > 90 volts and take out any DC load that was attached.

So--I would suggest that if you want a master power off switch--That you gang several breakers/disconnects together (Wind turbine on one, Solar charger on another, DC Loads on a third). Or, just have three disconnects in the same box, and no matter how anyone turns them off, the "high voltage" sources cannot drive into your sensitive DC loads (i.e., if somebody turns off the turbine first or last, it does not matter--The battery is still there to accept the any generated spikes).

If you have the main bus, then battery breaker, then battery... If somebody turns off the "battery master", you still have the charging sources+sensitive loads all on one bus, and no battery to buffer any surge voltages.

Of course, there still is the possibility of a wind turbine over-speed if there is not battery load--Typically turbine outputs are shorted if there is no load. Use a second shunt switch up stream of a blocking diode, or a Double Throw switch that disconnects from battery and shunts the turbine output in one click.

-Bill

newl · January 2013

Re: My Solar Project

I just burned an hour and a half reading that blog from start to finish (all while waiting for other background things to finish here at work) and I have to say that it was a fantastic read and one hell of a detailed effort Sam. Well done!

DavidOH · January 2013

Re: My Solar Project

Yup newl, I liked Sam's project too! That's why I suggested that he start his own thread, which he did. Might have to dig for it now. Didn't want his project getting lost in this one, or people confusing his with mine.

DavidOH · January 2013

Re: My Solar Project

I was thinking that only the inverter/charger goes through the 300 amp fuse. Then thought the DC load should be attached there also. Maybe not.
Would there be a possibility that the battery charger would be feeding the DC load? that's not a bad thing right? I am thinking that would not make any difference.

The Wind charge is an add on and may not be used at all. Just thought I'd leave a place for it. It would have a shut off that helps stop it from spinning. (The double throw switch)

All of the disconnects will be within arms reach of each other. Only the 300 amp fuse would be in the battery box.

Thanks BB for the input. :cool:

My Solar Project

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