Solar As Backup

souler · October 2010

I'm stuck with "the grid" for too many small business reasons to list. Yet having a solar backup seems immanently vital for the coming years, (too many reasons again). We have had piecemeal parts cobbled together in the past with recycled batteries. I hate battery chores but am now committed to pay what it takes, for solid but minimal, required gear. So, i would be grateful for some buyer guidance soon.

I can't change my lifestyle to fit the current conventional solar philosophies, but wish for just a few pv panels-- Yet i'm convinced of my need for maybe four brand new T-105-RE 6V batteries. In case of major grid troubles, storms, fires, CME, wars or whatnot. Maybe just a 100W @24V of pv, as minimal helper in the worst case grid losses. We went through 15 days without grid power in 1998 which was icy as an ice age beginning, (affecting hundreds of miles). Though had only short day outages before and since that time. We have several optional uses for using batteries where pv float-charges. To trim grid just a little, running inverter through temporary plug-ins. We live our life as if on a life raft already and we need to manually manage our thermal solar heating manually, (already). We can afford this minimal-pv scenario but can't afford a full system for our home business needs. Otherwise grid charging or generator provide backup. A grid tied system would risk dire business needs, in case of grid loss. So i call our needs "solar backup".

Particular advice wanted will follow. Although any challenging comments are welcome too.

1) Are any of the pv panel types better suited to cloudy regions? (Maine, here)

2) What gear is needed besides pv, inverter, AC charger and basic-builder tools of many types?

3) I already have general hardware, heavy cable stuff, good, central, indoor space with ventilation.

4) I'd like to minimize boiling messes from batteries: Are the new Trojan T105 caps good as can be? Enhancers??

5) Is the "Bogart Engineering TM-2020 TriMetric Meter Battery Monitor" the smartest buy for easy monitoring?

6) Can i use my 10 year old C-40 Trace charge controller? Anything better? Anything like a desulfurizer worthwhile?

7) Any particular solar panels to consider? Is undersize pv going to hurt batteries? Ages ago, i was taught that lead-acid batteries like a float charge. Where other chargers can handle optimized charging after a heavy battery use.

8 ) Is there a best float charge capacity to consider for a minimized pv system? To fit this particular scenario.

9) What is the easiest battery hydrometer and anything else needed?
We need to crawl/kneel into battery 'closet'.

Thanks for any thoughts or insights.

Cariboocoot · October 2010

Re: Solar As Backup

For emergency power, buy a generator. Way cheaper.

PV's of any kind don't put out much in bad weather - you know; the stormy conditions when the power goes off.

Those four Trojans you want will require 400-800 Watts of panel to recharge - that's the cost of the generator right there.

In short: off-grid "back-up system" will cost you $8,000 or so. You can buy a nice generator and a lot of fuel for that.

Solar for back-up is terribly impractical.

BB. · October 2010

Re: Solar As Backup

souler wrote: »

1) Are any of the pv panel types better suited to cloudy regions? (Maine, here)

Not really... Panel output power is pretty much limited to Watts of Sun on panel. Less sun, less power output.

Don't kid yourself on how much power cloudy weather will hurt you... Probably at least 1/2 the power in light overcast--Can be only 10% output or less in heavy/stormy weather.

For a useful system with that size battery bank, you should looking at 5% to 13% or so of the banks AH rating for solar panel / back up battery charger ratings. Say you are looking at 4x 6 volt * 220 AH batteries:

220 AH * 10% rate of charge = ~22 amp charging @ 24 volts
220 AH * 10% rate of charge * 29 volts charging * 1/0.77 system derating = 829 watts nominal array wattage

2) What gear is needed besides pv, inverter, AC charger and basic-builder tools of many types?

A good digital multi-meter and hydrometer at a minimum. A Battery Monitor and AC/DC clamp amp meter are nice.

3) I already have general hardware, heavy cable stuff, good, central, indoor space with ventilation.

If you have to mount the array farther from the charge controller/battery bank, Run the solar array voltage at Vmp = ~48-100 volts on a MPPT charge controller. That will keep the wire gauge and voltage drops reasonable.

4) I'd like to minimize boiling messes from batteries: Are the new Trojan T105 caps good as can be? Enhancers??

I don't know about the Trojan caps, but if you need "better caps" look at these Water Miser Battery Caps.

5) Is the "Bogart Engineering TM-2020 TriMetric Meter Battery Monitor" the smartest buy for easy monitoring?

Very good price/performance value. You should be very happy with it.

There are higher end battery monitors that have a programmable output. For example, set it to alarm at 50% battery state of charge (more accurate than measuring battery bank voltage under load). Can turn off the inverter or tell you to start the backup genset.

6) Can i use my 10 year old C-40 Trace charge controller? Anything better? Anything like a desulfurizer worthwhile?

Yes, if the cable run from the Array to the C-40 is "short", it will work just fine (always keep the cable run heavy and short from charge controller to the battery bank).

Desulfators are probably of limited use. If you want to try one--go ahead. There are known issues for some people with causing their Outback MPPT charge controller to cause reduced charging output (because of electrical interference?).

7) Any particular solar panels to consider? Is undersize pv going to hurt batteries? Ages ago, i was taught that lead-acid batteries like a float charge. Where other chargers can handle optimized charging after a heavy battery use.

If purely float charging--You might get away with a 1% rated panel (~85 watt panel for above example). But the solar panel will not be able to keep with with any loads. As the batteries age (near end of life), they will probably exceed the power available from an 85 watt panel.

You will need a back-up charger (AC line, or genset) to equalize the battery bank at 5% rate of charge every 1-6 months or so.

Also, you would need a back up genset for power failures that last any length of time to recharge the battery bank.

8 ) Is there a best float charge capacity to consider for a minimized pv system? To fit this particular scenario.

Not really, the charge controller should hold the voltage at ~13.7 volts or so... If you use an Iota charger, its ultimate size depends on battery bank charging requirements for actual battery bank size (equalization) and keeping up with any connected loads (basically making your own UPS).

9) What is the easiest battery hydrometer and anything else needed?
We need to crawl/kneel into battery 'closet'.

You may want to look at AGM batteries instead. No hydrometer/refilling of cells are needed. AGM will be 2x or so more expensive, and may not last quite as long as flooded cell.

With AGM, you probably should get a remote battery temperature sensor for any charge controller you plan on using. AGM's do not like over charging.

Thanks for any thoughts or insights.

In the end, what are the loads you wish to support and how long do you want to support them with solar?

For what you are asking for--I would seriously consider a good genset and backup fuel supply instead. I am not sure that solar+battery bank really does anything for you from your starting panel size + plus possible loads.

You either need more to support more loads than your system (as defined) can reasonably support--Or you could use alternatives (AA batteries/D Cell batteries for backup radio and a few LED lights--Use lithium primary cells if you want 10 year storage life, use Costco Alkaline for 5+ year storage life) and skip the whole expense of an under paneled (not enough sun in winter) solar solution that would need a backup generator for outages over 10 hours anyway...

-Bill

mike95490 · October 2010

Re: Solar As Backup

for short half hour outages, mid-size computer UPS's are fine, portable, and a biz tax writeoff as office equipment

zeuspaul · October 2010

Re: Solar As Backup

In short: off-grid "back-up system" will cost you $8,000 or so.

I am also looking at an emergency Solar Back up system.

Using BB's numbers of 829 watts PV.

6 Kyocera 135's is about $2500 and 810 watts nominal.

4 Crown 6 volt golf Golf batteries $450 (local retailer) 225 amp hr capacity at 24 volts.

Morningstar MPPT 45 controller $450

Exeltech 2000 watt 24 volt inverter $1300

Soneil 2416SRF 8 amp battery charger (low inrush to protect the HF generator) $200

2 Harbor Freight 800 watt generators $200 (one backs up the other)

plus $400 miscellaneous for a total of about $5500 before possible rebates.

I can make use of the power when it is not being used for the rare emergency. If I can use 2 Kwh per day at an offset cost of 30 cents per Kwh that is a savings of 60 cents per day. That is $2190 in ten years less $450 for a battery change for a total of $1740 in ten years.

Initial cost of $5500 less $1740 energy savings is a net cost of $3760 not including any applicable rebates.

Loads

Emergency back up load- One 100 watt air purifier (smoke) in emergency fire shelter.

Secondary back up loads- Three 100 watt air (smoke) purifiers in the house. Our utility has informed us they WILL shut off the grid when the wind speed is 56 mph and the air is dry. We will have no power for essentials during an emergency fire situation unless we provide our own.

If the power is out for more than 12 hours and there is no smoke I want to be able to run my refrigerator and check the Internet and TV for info. High wind scenarios are likely to last one to three days.

When the sun is shining and there is no emergency the power will be used to run a pump for a water feature.

Zeuspaul

niel · October 2010

Re: Solar As Backup

unless the outage goes for long periods of time like in days then a back ups type arrangement without solar will work quite well when you can't use the generator. you could also use a battery backed gt system and add pv in smaller groupings.

Cariboocoot · October 2010

Re: Solar As Backup

Zeuspaul;

That is a good, well-thought-out system at a good price too! You may regret the HF generators in the long-term. I've had cheap generators before, and they always turn out to be a false economy. But then off-gridders tend to use gens more than most people. Just can't keep the sun shining all the time!

And for those who want "quiet power" there's always the old formula of generator for daytime power/battery charging and inverter at night. Saves the $$$$ spent on panels and controller.

Kamala · October 2010

Re: Solar As Backup

These statements lure me.

souler wrote: »

I'm stuck with "the grid" for too many small business reasons to list.

souler wrote: »

A grid tied system would risk dire business needs, in case of grid loss.

What is the business? What is its location? Why is grid failure so detrimental to said business? How common is a lenghty loss of grid power?

In my 57 years of life, I cannot recall an outage of more than a day or two. Maybe there were some longer but I just don't recall them.

Living near the geographical center of the North American Continent, I see all types of weather (except hurricanes and monsoons.) Earthquakes could still happen but not likely. However, severe thunderstorms, and the tornadoes that they spawn, are common in the summer and the cause of most grid power loss. Snow and ice can do it in the winter as well, but I'll probably not have to run to the NE corner of my basement to get out with my life.

So, how do I plan for GRID DOWN? I keep a 100AH battery (I like AGM) duct taped a 500W MSW inverter in the garage and held in float on a grid connected 3 stage charger. When the power goes out I bring the bat/inv in from the garage and plug in the TV and a light. Why? So I can watch the local TV weather and track the possible tornado!

But for long term outages or larger loads, I agree with previous posters. Generator.

K

zeuspaul · October 2010

Re: Solar As Backup

unless the outage goes for long periods of time like in days then a back ups type arrangement without solar will work quite well when you can't use the generator.

But that's a lot less fun to install:roll:

I have to plan for 24 to 72 hours. The utility claims they can't turn the power back on after a wind event until all of the lines have been inspected. Santa Ana winds can easily last two days. The utility had to come up with about a half billion dollars after the last fire storm because their grid caused some of the fires. They are determined to shut it off when winds exceed their design threshold.

In my example I would save $3000 on the solar panels and the charge controller but would lose about $1500 in rebates and $1760 in power for a net savings of about zero.

The comperable UPS system would be the four batteries $450, the Exeltech inverter $1300, battery charger $200 and the two generators $200. That's a total of $2150.

The net cost in my post is $3760. Federal rebate is about 30 percent of $5000 (generators probably don't qualify) so the net after rebate is about $2260.

However I wouldn't feel comfortable with a cheapo generator in a backup system without the solar panels. I don't want to rely on a small engine generator for an emergency. My neighbor pulled his $1000 generator off the shelf when he needed it and it didn't start. Also I would have to run grid power 200 ft underground through rocky terrain to the battery charger just to keep the ups battery charged. This would have to be 18 inches underground and permitted with significant additional cost. Also I prefer to not have the emergency back up power system connected to house wiring in any way.

you could also use a battery backed gt system and add pv in smaller groupings

I am not as versed on grid tie because I haven't spent as much time looking into it because I don't think it fits my needs. My understanding is grid tie with battery back up is more complicated than just grid tie. I would need the inverter and transfer switches. The batteries are 200 ft from the meter so the inverter would have to be 200 ft from the meter. I would have to hire an electrician and pay multiple permit fees and pay the utility $5 per month just for the privilege of hooking my tiny array to their grid. Also I believe my electric bill would go up because I may have to go to TOU billing which has higher rates for the times I use the most power.

Zeuspaul

KeithWHare · October 2010

Re: Solar As Backup

Kamala wrote: »

In my 57 years of life, I cannot recall an outage of more than a day or two. Maybe there were some longer but I just don't recall them.

You must live in the right (or wrong) place. We live in a rural (wooded) area of Ohio, on the end of a power line so when there is an outage, we are just about the last to regain power. Two years ago, in September, we had a windstorm that took out power for about a week. In the last 10 years, we've had half a dozen multi-day power outages.

Aside from the freezer and refrigerator, the biggest issue is the pump -- without power, no water. We've hauled water from the creek to flush toilets. That's no fun, so we've had a 10kw propane powered generator with an auto start, auto transfer switch for 6 years. For us, it has been well worth the investment.

But for long term outages or larger loads, I agree with previous posters. Generator.

K

I keep looking at the costs of solar electric for our house and can't justify it yet. The generator was cheaper to install than a solar system and is not impacted by snow and ice.

Keith

Kamala · October 2010

Re: Solar As Backup

Yes. I am lucky. Minnesota is as close to Canada on one can get and still be in the U.S. Not that such should be a goal.

The electric utility here in Minneapolis/St Paul (once NSP now Exel) does a good job of keeping the current flowing. Again, I am lucky. Birthright?

Kamala · October 2010

Re: Solar As Backup

KeithWHare wrote: »

... we've had a 10kw propane powered generator with an auto start, auto transfer switch for 6 years. For us, it has been well worth the investment.

I keep looking at the costs of solar electric for our house and can't justify it yet. The generator was cheaper to install than a solar system and is not impacted by snow and ice.
Keith

Well, no matter where you go, there you are.

As the gurus here preach, conservation is the way.

Good luck!

Craig

Cariboocoot · October 2010

Re: Solar As Backup

Kamala wrote: »

Yes. I am lucky. Minnesota is as close to Canada on one can get and still be in the U.S. Not that such should be a goal.

The electric utility here in Minneapolis/St Paul (once NSP now Exel) does a good job of keeping the current flowing. Again, I am lucky. Birthright?

Nothing like a good utility company, eh?

I've experienced a few different companies over the years. Aside from their policy schizophrenia, BC Hydro is pretty good.
But there was RG&E back in NY. Their policy was "Profits first, second, and last". The high Voltage line in front of our house there had 14 splices in 1/4 mile because the company would not replace any wire unless it absolutely couldn't be repaired. And power outages were a once-a-month, year 'round occurrence.

Solar As Backup

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