NorthEast-US-Solar Emergency Backup Pwr

System

Greetings:

I'm a long time resident of S. NH, where weather is 4 seasons, cold winters, power outages when serious ice storms come along. Last winter we were hit in mid-December with an ice storm which knocked us out of power for 7 days. The region suffered a lot of damage, and some were out as much as 14+ days. Having experienced this in past, I was prepared with a back up gas generator, candles, flashlights, gas cooking, Wood stoves and Wood. Furnace uses oil for both heat and hot water (variable and costly), and water is 100 ft well (220 VAC pump). We did fine but the generator consumed a lot of gasoline to keep all going, and required constant attention. Rains came and flooding was a problem, especially when out of the house because sump pumps did not come on. Keeping on top of it all was doable, and we eventually swum out of it. Nonetheless, it made for a very long winter.

This year I decided to give solar a try to provide back up power in emergency situations such as above. I've obtained and roof mounted 4 - 42 W EVP solar panels (Thin film type-open voltage 55-60 vdc in full sun, .96 amp). I'm in the process now of wiring them in parallel using MC4 connectors and ~ 30 foot run to my solar power panel (in progress) in the basement. These panels are wired 14 AWG, so I stayed with that gauge wiring for starters. The solar panel will reside beside the mains house panel breaker box (200 Amp service).

I purchased a Morningstar MPPT 15 Amp charge controller, battery thermometer, PC - RS 232 connector to monitor and track data via laptop, two 12 volt Interstate deep cycle Marine batteries (flooded), a DC surge arrestor for the panels, and have some electrical boxes and starter supplies to begin mounting this weekend.
I'm close to purchasing an inverter, but have a few questions before I spend more $$.

Q-1 I'm trying to decide the best location to place the batteries, inside or out. I have an outside location with plenty air flow that is well contained and under my porch adjacent to basement control room. Temperatures in winter average in the 20's, sometimes close to 0 ~ Jan-Feb. If I place in basement, I can mount in a corner location above the oil tank (275 gal monster), in an enclosed box with air flow and vent to outside (temp controlled, 65-75 year round). My research indicates batteries perform best and last longer if not exposed to big temp swings. Any and all input is appreciated.

Q-2 I plan to install Main disconnect between panels and charge controller. Can I use a circuit breaker here or does it need to be a D-2 type fused disconnect?

Q-3 I have access to a auto salvage yard and can obtain battery cables of various lengths and sizes at low prices. Is this OK to use as long as they are not worn or damaged?

Q-4 I plan to install disconnect between batteries and incoming power/inverter. Same question as 2 above.

Q-5 I'm leaning toward the Excel Tec inverter product, and trying to decide whether to set up the battery bank in 12 or 24 V? Pros and Cons? Do I need also an AC arrestor here?

Q-6 This is the pilot project for now, and based upon what I can realize with this initial set up will drive my expansion going forward. Ultimately, I'd like to be able to provide enough power to operate 2 sump pumps when called for, pull water from well (will consider adding a 110-220 VAC step up transformer to do this for starters), the furnace (115 vac, hot water baseboard) and some minimal lighting. I'd like to experiment with a combination of AC and DC power. To access the AC components, I plan to initially use/modify my current generator input configuration. I envision doing this as an 'off grid' system for starters, manual switching. I can still use my gas generator to supplement in power outages, and also to charge up the batteries to supplement the panels.

Generally, it's a work in progress as I hope to gain some expertise along the way, generate power to use daily and in emergencies, and perhaps get to a point where I can be a solar provider in my area.

I appreciate any and all feedback, suggestions, ideas and help from the many experienced users on the forum to one or more of the questions above.

Thank you in advance for your time and willingness to share your experiences and expertise.

Best to all. Bill

Cariboocoot

Re: NorthEast-US-Solar Emergency Backup Pwr

The very first thing you need to do is buy a Kill-A-Watt meter or similar and get some real world figures on how much back-up power you need to provide. You mention well and sump pumps - these will use a lot of power and may not be practical to supply via solar. But since you can't leave your gen on 24/7 you have to have some sort of sump pump capacity (well pump can be run from a gen on an as-needed basis). There's a thread somewhere on this forum discussing various sump pump alternatives for power outages. Try a search for it.

As for questions:

Q1; charged batteries will not freeze. If there is a great concern about the potantial, AGM's will not freeze even if only partially charged (but are more expensive per Amp/hr). Locate them wherever is best to keep the cables short.

Q2; you can use an auto-transfer switch to separate inverter from grid power. You can also use an inverter with built-in charger, feed it off one breaker, and feed the 'critical loads' from the inverter. This will keep your batteries up as long as there is grid power.

Q3; you need to get a fix on system design first. These automotive wires may not be sufficient gauge to handle the DC current load. Especially on a 12V inverter. Typically, auto cables are no bigger than 4 gauge, and are meant to handle less than 100 Amps. That's like a 1200 Watt 12V inverter at maximum current. (NOT exactly - just as an example. The actual current depends on other factors as well).

Q4; generally fuses are used between batteries and inverter, because they're cheaper. It is more elegant to use a breaker here, as it also provides convenient disconnect. It must be a DC breaker rated for the application.

Q5; figure out what your power needs are first. The reason to go to higher DC system Voltage is the need to supply greater Watts while keeping current levels manageable. If your maximum Watts don't exceed 1000, there's no need to go up to 24 or 48 VDC. In between 1kW and 2kW you have to consider things like average use, peak use, and line losses. A 12 VDC system is generally less expensive in terms of capital outlay, but may not be in terms of cost per Watt.

Q6; when you start trying to run pumps and heaters off inverters you take a quantum leap into the realm of the expensive. These things are big power users; several magnitudes higher than typical loads like TV's or even refrigerators.

You can start with a small inverter set-up, and then add an entirely separate big system for heavy loads later - once you got your feet wet, so to speak.

You can also skip the solar panels to begin with, and re-charge with your generator during the day to supply 'quiet power' at night if that would be more practical for you.

This is just the start; you'll be getting more advice and some of it may seem contradictory. Just several different ways of achieving the same result.:D

icarus

Re: NorthEast-US-Solar Emergency Backup Pwr

Welcome to the forum,.

Without trying to be too gloomy and discouraging you from the project but your 42X4 panels won't give you much usable power, especially in the winter.

A general rule of thumb is take the name plate rating of your panels, multiply by ~.52 to account for system loses and then multiply that by the number of hours of GOOD sun (ususaly ~4) to give you a rough number of watt/hours you can draw.

So in your case, 168X.52=87.36X4=349 wh/day, assuming ideal sun for those four hours. That would be enough to run a 125 watt TV for b~2.79 hours, or one 15 watt cfl bulb for ~23 hours.

So a couple of answers. If you are looking for this system to provide anywhere near "living" type power, it is way too small. You will probably find that a small generator system, (Honda Eu1000 or Eu2000) gives way more bang for the buck as an emergency power source.

Second, it is important to size your components to your loads. Start with your expected loads, then work backward to see how big an inverter/ battery bank/ charge controller/ PV array you need. Running 300 watts off a 1500 watt inverter is very inefficient. I would suggest a Suresine 300 pure sine wave inverter for your system. With your solar capacity you are not likely to be able to power anything bigger.

Batteries want to be cool. With your tiny little PV you have no worries about creating enough hydrogen to be a problem where ever they are located. What you really need is the shortest wire length from PV to battery, and especially battery to load. For example, 300 watts at 120 vac = 4 amps. The same 300 watts powered from your batteries to the inverter is 40 amps @ 12vdc. so any line loss is 10 times greater with the lower voltage.

Any disconnects can be fuses or breakers. For a simple system such as this, I would lean toward fuses as being cheaper.

Good luck, and once again welcome to the forum,

Tony

PS I see Marc beat me to the punch. (Fully charged batteries WILL freeze, but it has to get to ~ -60 for them. On the other hand, a 1/2 charged battery can freeze at ~-20f if memory serves.

BB.

Re: NorthEast-US-Solar Emergency Backup Pwr

Regarding how much power you can capture for your location with Solar--Using the PV Watts website for Concord NH, assuming 1kW of panels and 0.52 for an off grid system:

"Station Identification"
"City:","Concord"
"State:","New_Hampshire"
"Lat (deg N):", 43.20
"Long (deg W):", 71.50
"Elev (m): ", 105
"PV System Specifications"
"DC Rating:"," 1.0 kW"
"DC to AC Derate Factor:"," 0.520"
"AC Rating:"," 0.5 kW"
"Array Type: Fixed Tilt"
"Array Tilt:"," 43.2"
"Array Azimuth:","180.0"

"Energy Specifications"
"Cost of Electricity:","12.5 cents/kWh"

"Results"
"Month", "Solar Radiation (kWh/m^2/day)", "AC Energy (kWh)", "Energy Value ($)"
1, 3.80, 63, 7.88
2, 4.56, 69, 8.62
3, 4.89, 79, 9.88
4, 5.19, 76, 9.50
5, 5.40, 78, 9.75
6, 5.42, 74, 9.25
7, 5.59, 78, 9.75
8, 5.47, 77, 9.62
9, 4.93, 68, 8.50
10, 4.01, 60, 7.50
11, 3.13, 47, 5.88
12, 2.87, 46, 5.75
"Year", 4.61, 815, 101.88

You can capture around 46 kWhrs per Month (December) to >70 kWhrs per Month for 1/2 the year. (1kW is as small as the PV program goes--multiply the above by 0.164 (kW) worth of solar panels for your system).

Looking at Nov/December--46 kWhrs per month per 1kW of panels:

46kWhr per month per 1kW of panels * 1mnth/30 days * 0.164 kW of panel= 0.251 kWH/day = 250 Watt*Hours per day

To be honest, that is not a lot of power for the average utility connected home.

Take the number of Watt*Hours (kWhrs) that you measure with the Kill-A-Watt meter and lay that against your solar+generator+battery setup.

What is your generator setup? What is your average maximum power requirements (i.e., run the microwave+sump pumps+lighting+TV together, and run the turn off the loads to run a well pump, or size the system to run everything--which tends to be fuel inefficient).

I tend to recommend the smallest practical genset for people's needs. And the genset should be quiet and fuel efficient. And it will not be "cheap"...

For small systems/homes/etc., the Honda eu2000i (manual start) or eu3000i are nice and quiet emergency power gensets. For larger gensets (and alternate fuels like propane)--looking at RV wrecking yards may turn up a nice Propane fueled RV generator. A definite step up over manual/portable units.

The "cheap" 5kW noise makers can still have a place... Run it a couple times a day to pump water / pressurize the tank. And run the rest of the home on the small/quiet model.

Using a genset during the day to charge the batteries, power large loads (pumps, day time loads) and running off of the batteries at night (lights, TV, etc.) is not a bad solution to a low Solar Power Environment.

Keeping the batteries around 70-80 degrees F is ideal... Below freezing, the batteries lose capacity. Above 80F they age quicker. Above 110F or so, they can fail.

-Bill

niel

Re: NorthEast-US-Solar Emergency Backup Pwr

you may also need to check for your voltage drop percentage. the small gauge wire you are using (#14) may not allow the power to transfer well and depends on how much current is going how far through what gauge wire at a certain voltage. there is a sticky for a calculator in the info and facts section. you shouldn't think in terms of what is ok for ac wiring as the voltages are 10x higher for that making the percentage 10x lower than you will see.
in any case you should try to use larger wires and this is especially true for any battery bank and inverter where current levels can be high. also note that you can use conservation methods to reduce the amount of power you need for some things like going with cfls or led lighting as every little bit helps when there's a power outage.

halfcrazy

Re: NorthEast-US-Solar Emergency Backup Pwr

Also it looks to me like the 45 degree corners are shading the corners of the panels? I may be wrong though.

niel

Re: NorthEast-US-Solar Emergency Backup Pwr

good catch as the corners are shading it. if the pvs allow for it you should try to devise a way to secure from underneath.

System2

Re: NorthEast-US-Solar Emergency Backup Pwr

Many thanks to all for the comprehensive comments, advice, data, information and help. It is very much welcome and appreciated.

I realize I was 180 degrees out of phase on some of my thinking, notably not figuring the loads beforehand. The panels were a gift from a colleague so they acted as a seed for the project to get going. These EVP-42 units are glass on both sides, and serve both collector and architectural functions. They are intended to be used in large numbers on buildings and massive arrays, running at higher voltages. So probably not the best choice for me to start a small project with. But it's a start nonetheless.

Yes, in my naivete, I secured them in the wood frames with wooden triangle corners which do block out some light at all 4 corners on all 4 panels. I see now this detracts from performance and needs to be changed. If I replaced the wood with plexiglass (or facsimile) will this be OK? Perhaps I can glue something to the back side to attach to?

I will need to add more panels sooner than later. If you have any suggestions on style/value/watt/ etc it would be helpful. I assume I can integrate additional panels even if they are not the same kind. Voltage issues will need to be addressed, other considerations??

My genset is a 20 yr old coleman, 4000 watt. It puts out 120 VAC / 33 Amp -- 240 vac / 16.5 amp. Gas powered. It doesn't have a lot of hours on it, and still runs well. Perhaps I can convert it to propane? An electric start would certainly be an improvement, particularly on those cold days when yanking the pulley is easier said than done.

I ordered a Kill-A-Watt meter to make measurements. I followed your advice and picked the 300 watt Morningstar inverter.

Realizing the batteries can be inside without worrying too much about gas buildup from a small system is helpful. It would shorten cable lengths certainly, and make it easier to monitor, service, etc. Safety First!

Lots to learn here and I will review in more detail everyone's posts to understand better. I'm sure I'll have more questions.

Once again, thanks to BB., niel, halfcrazy, icarus, Cariboocoot. You all sure know your stuff.

Cheers

Bill

icarus

Re: NorthEast-US-Solar Emergency Backup Pwr

I'm not sure I would bother converting to L/P, (propane) but if you are interested have a look here: http://www.propane-generators.com/

Or here:http://www.propanecarbs.com/

As a suggestion for your current generator, run it at least once a week and keep fresh fuel in it. Use light weight oil in the winter, or add a dipstick heater so that it turns over a bit easier. You could also keep a can of starting fluid (ether) handy, although I don't I don't think that it is very good for engines to use every start.

The other suggestion I can make on this project in general is read,study and learn all you can here and elsewhere. There are some very smart folks that populate this site, sharp enough that in many ways they have forgotten more about Pv than most of us will know. This allows folks that are just getting started to not have to invent the wheel at each turn of it.

Tony

BB.

Re: NorthEast-US-Solar Emergency Backup Pwr

Bill,

Just so you know (it is not obvious)--Our forum is hosted by Northern Arizona Wind & Sun. A wholesaler/retailer out of Flagstaff Arizona.

You can visit their web store here and see what they offer. They stand behind their product and try to offer reliable products at good prices.

However, there is no pressure for you to purchase from NAWS. In the end, pick the products and (delivered) pricing+service that works best for you.

Some items (solar panels, lead acid batteries, etc.) can be expensive to ship and purchasing local (if you are not buying large volume) may make more sense.

Other than Windsun (the Admin)--none of us here are associated with NAWS in any way other than providing our writings here (and in Niel and my case -- volunteer spam control).

Take a look at mono or poly crystalline silicon solar panels. You can collect almost twice as much energy per square foot/meter with those versus the typical thin film units. Very helpful if space is limited (even though they do cost more). When comparing good quality solar panels--always converter back to $$$/Watt pricing (delivered) to make sure your solutions are optimally priced. Usually a few large 100+ watt panels are an, overall, better deal than a bunch of <100 watt panels wired and mounted together.

Regarding your Battery Bank... Yes, AGM's under normal conditions do not vent hydrogen gas or acid/electrolyte fumes.

HOWEVER, if there is a failure in the charge controllers, a short in the wiring, or other issue... AGM batteries can pressurize, vent, spray acid, and/or explode with shrapnel when exposed to sparks/fire/hot wires with the best of any lead acid battery.

Always treat them with respect. Use fuse/breakers/appropriately sized wring/etc. in your setup. Do not install your battery bank under your bed or in your closet. Keep away from possible ignition sources and provide some sort of venting + shielding (from dropped tools, keep acid mist away from sensitive objects/devices).

Even a small lead acid/AGM/Sealed battery can supply a surprising amount of current. One or more Car Sized (or larger) lead acid battery equipped bank can supply an astonishing amount of current into a short circuit. Personally, I am more worried when working on a lead acid battery bank than round typical home wiring.

-Bill

PS: Sorry for the warnings if they are redundant for you... I just want to make sure that everyone (new and old) remain safe around here.

peakbagger

Re: NorthEast-US-Solar Emergency Backup Pwr

Since you are in NH, you may want to consider going for a solar rebate. NH offers $3 per installed watt for both on grid and off gird (this is very rare, most states dont rebate off gird systems). Granted a lot of paperwork, but when you add in the federal 30% solar rebate, you need to keep paperwork anyway. Obviously make sure your read and understand the rules on the PUC website as you need to apply for the rebate in advance and get your design approved as well as a site survey. The easiest way to go is to do a grid tied with an Outback Inverter with battery backup, but if you want to design your own, you are in the right place.