Solar simply as backup to possible grid failure - post SHTF

Xizang · January 2016

I'm living with a girlfriend in one of those 'flyover' states that the politicians in Washington mock and make fun of. I'm coming close to being one of those "preppers" who believes tough times are coming, and I'm wanting to be able to produce power to run the house should the system fail. And on the practical side, I'm also a marina manager between management gigs, looking for a large marina to manage along the southern coast or in Central America. Once I have a decent marina to operate, I'm loading up the solar stuff and girlfriend and heading south. Solar works fine on boats as well as it does as backup in a landlocked northern state.

Okay, question: Have any of you invested in a solar power plant that is set up as a backup source of power? And have any of you built a package that's intended to be transplanted from one land location to perhaps a marine application?

verdigo · January 2016

I have a backup system that powers most all of my 120 volt loads with the exception of heating and cooling, and hot water. I have 3500 watts of panels and around 400 amp hours of backup batteries. It is somewhat portable as I built my power shed to be moved, and most of the ground mounts can be moved as well. Might be a bit much for a boat though

Dave Angelini · January 2016

Buy a Catamaran! The best platform for solar at sea! A nice sun/solar mount Bimini under the main and set the autopilot.
The store here can ship most anywhere and I do also. A large system can be shipped by DHL into central america in a shipping container. You can rent one!

When we were along that coast we always had a ditch marina to leave the boat. It had to have a cinder block bar high up on the hill to watch Astraea.

BB. · January 2016

In general, solar is not great as a short term backup power source (or prep'ing for major disasters).

Simply, because of the battery bank and the expenses. Batteries are good for 5-8 years typically. You can get forklift batteries that can last 20+ years, but they still need monthly checks for water levels, and consume a fair amount of power for float charging. And Lead Acid Deep Cycle Batteries, do need to be cycled for best life and performance (discharge to 75% state of charge once a month is a good starting point).

Also, a battery bank to power an off grid home with a near normal amount of electrical life (call it 100 kWH per month or ~3.3 kWH per day) is heavy (and not cheap). For example 3.3 kWH a day will power a refrigierator, LED lights, TV+Laptop Computer, clothes washer, and well pump (pretty heavy conservation on your family's part):

3,300 WH per day * 1/0.85 inverter eff * 1/48 volt battery bank * 2 days storage * 1/0.50 max discharge = 324 Amp*Hour @ 48 volt battery bank

Or something like 8-16 6 volt @ 200 AH "golf cart" type batteries (2x strings of 8 batteries in series, 16 batteries total, for 400 AH @ 48 volt battery bank).

Amount of solar panels. Two calculations, one based on size of battery bank and 5% to 13% rate of charge. And second hours of sun per day (by season). Size based on battery bank:

400 AH * 59 volts charging * 1/0.77 panel+controller eff * 0.05 rate of charge = 1,532 Watt array minimum (standby/weekend/seasonal usage)
400 AH * 59 volts charging * 1/0.77 panel+controller eff * 0.05 rate of charge = 3,065 Watt array nominal (full time off grid)
400 AH * 59 volts charging * 1/0.77 panel+controller eff * 0.05 rate of charge = 3,984 Watt array "cost effective" Maximum

And then based on hours of sun per day... This stuff is seasonal, and unless you live in an area with few long term stormy weather/dark winters, you usually need a backup power source for full time off grid living (genset, or similar).

Say you live near Lincoln Nebraska... Fixed array, tilted for optimal year average solar collection:

http://solarelectricityhandbook.com/solar-irradiance.html

Lincoln
Average Solar Insolation figures

Measured in kWh/m2/day onto a solar panel set at a 49° angle from vertical:
(For best year-round performance)

Jan	Feb	Mar	Apr	May	Jun
3.65	3.82	4.65	4.91	5.16	5.54
Jul	Aug	Sep	Oct	Nov	Dec
5.73	5.41	5.38	4.70	3.72	3.47

Toss out the bottom three months (assume generator assist when needed), then February is your "break even" month:

3,300 WH per day * 1/0.52 average system eff * 1/3.82 hours of sun per day average = 1,661 Watt array minimum

So--"prep'ing" you would need (at least) a 1,661 watt array, and if you where planning on living full time off grid, I would suggest that a 3,065 Watt array minimum (minimize generator use, happier battery, power to carry you through much of winter).

And add that electronics, on average, and about a 10+ year life (and still age even if in storage)--You are hard pressed to come up with a bullet proof system that would operate "problem free" for 10-20 years (yes, it can happen, but on average something will go wrong and you will still need to obtain parts/new batteries/distilled water/etc.). Even hard to find a refrigerator that will last 20 years these days.

Anyway--A quick sizing of a "smallish" off grid system that would keep you relatively comfortable... Just remember to look at your monthly power bill--Good chance it is in the 500 to 1,000 kWH per month range--And I am suggesting a system that is 1/5 to 1/10 that size. A major change in lifestyle if you want to live this way. And this uses other fuel sources for heating/cooking/hot water. You can do an OK job with solar thermal to supplement (solar ovens, solar thermal systems--which do approach "plumbing" nightmare of pumps and piping). But wood/propane/oil are typically the source of heat.

Or go how folks a 100 years ago did and have a root cellar, canning, dry goods, tallow candles, go to bed when the sun goes down, etc.

A good magazine to read about off grid life is:

http://www.homepower.com/

Please ask questions--This is just a conversation starting point.

-Bill

mike95490 · January 2016

First off. Batteries are expensive. And need replacement every 6-10 years. The solar electric panels are generally good for +20 years. The electronics can be counted on for 10 years.
Solar on boats is a troublesome issue. Panels need to be aimed properly for best harvest. No good aim = poor harvest. Shadows from masts, stays, radar racks, will shut off a panel while it's shaded.
Building a trailer with a battery box (count on at least 8 ea, 6V batteries wired in series for a 48V system) Smaller systems may not last through a 3 day cloudy/storm period. Panels are great sails, and going 65mph down the interstate will need attention to aerodynamic loads to not blow them off or apart.
For 3 or 4 days backup, a generator and can of gas is all you need. If you want to store more gas, easy to get to a month. After a month, the expense of Panels and Batteries begins to make sense, If a bad storm takes out the power grid, it's also likely to take out your panels (big wind sails and lawn chair catchers) too.

oil pan 4 · January 2016

Mine is portable, mobile adaptable and expandable but since I am land locked and a land lover marine applications just are not in my wheel house.

http://ecorenovator.org/forum/solar-power/4544-home-made-solar-inverter-generator-hybrid.html

The 180 watts of solar panels on my suburban are also pretty mobile, they go every where I do.

The suburban solar panels and the solar hybrid generator can tie solar panels together.

Xizang · January 2016

When in California I had a small 50 watt solar panel mounted outboard on an aft rail, out of the way, on a 28 ft sailboat. Batteries and inverter were down below, and it worked great for 12 volt gear on short trips. Looking at (hopefully) a job in Central America, where I can live aboard a houseboat or larger sailboat. I realize everyone's needs and goals are different, just like all our various lifestyles. But I'm of the age (69) and mood to keep life as simple as possible. It's just easier that way.

Xizang · January 2016

UPDATE Major snowstorm hits the US northeast and east coast. Millions without power.

So how impractical is it for folks to invest in solar simply as backup power for seasonal power outages?

BB. · January 2016

Do a real cost/benefit study on each major source of backup power. Solar, genset (may have several fuel options), wood stove, etc.

In general, a natural gas fired genset is difficult to beat. Gensets store pretty well (keep them cool and dry), no fuel to handle/store. Years ago, knew a family that from somewhere in the east and brought their natural gas backup genset--Used it much more in California SF Bay Area than they ever did back east.

When you have to look at other fuel choices (gasoline, diesel, propane), then you have other issues (cost of tanks, recycling fuel--gasoline with fuel stabilizer may last 6-12 months), diesel (double wall tanks, water in diesel will grow stuff), propane stores well--but in a city, may have permit issues.

Me, I like gensets, but want to keep them small. A 1,600 Watt genset will keep me warm and a refrigerator/freezer cold. And only cost me a couple of gallons of fuel per day. "Real" backup gensets seem to start at ~8-10 kWatts minimum size (other than gasoline fuel source, electric start, auto start+transfer switches). When you look at a 10 kWatt genet that may consume >1 gallon of fuel per hour minimum, you are talking about a lot of fuel storage (24 gallons per hour). A smaller genset will run 4-9+ hours on a gallon of fuel--This is emergency backup for me, not full time off grid. 24 gallons of fuel will last me 10 days or so with a small genset.

And small gensets are easily portable (my Honda eu2000i is 50lbs). Plus I can use the stored fuel in my car/truck for bugout, or use the fuel in the car and truck for genset--Options.

And running a genset--Noise, smell, CO2 poisoning, etc.

Solar is a fairly costly & "low density" power source. Lots of panels and batteries (if you want lots of power). Sun does not always shine, flying objects break glass panels, batteries only last 5-8 years (on average, even if never used). If you want to move anything larger than a few panels and batteries, it is a major amount of work.

For folks that are out in the country (well, septic system, pantry)--Planning on bedding down for a few months is not out the question.

In the city (sewer, water, power)--If there is no power to run the city services, they may do things that don't work well for me (i.e., shut down drinking water to prevent sewer systems from overflowing because of no pumps--At least one person here put in a septic field valve so he could shut off city sewer and prevent backup into his house). And they can red tag/force me out even if I am warm and comfy in my home.

I would be really happy (for backup power) if I could get a small ~2-3 kWatt genset with natural gas/propane fuel operation and auto start/pressurized oil system+filter. A few folks will use RV (Onan or similar) genset for backup home power. Looks very nice.

In the end though--It is not really something that makes a lot of sense... The last 2 week outage I lived through was >55 years ago in a coastal valley (I was ~5 year old or less). And everyone was doing OK without power, but the water tanks (on hills) were near running out when power was restored. Few people had gensets at that time. The rest of the outages--2 hours or less (usually a car hit a pole).

Lost water (broken main) for the morning last year--Quite surprised how that made me feel unprepared without water (had 50 gallon water heater and some flats of drinking water)--But trying to prepare for "anything" in a crowded metro region--Short of bugging a 100 miles to a vacation home outside the region (for us, earth quakes are the major problem) expecting to last more than 1 week without services--I think it could get ugly trying to stay.

-Bill

Dave Angelini · January 2016

You are on the short list of those who could bring their trailer here. 16,000 gallons of rainwater right now not including the "pool". "Staying" would get ugly in a major earthquake, just getting out in time before the SHTF might be quite a challenge.

softdown · January 2016

Being prepared for a SHTF scenario is attractive to those who like to "be prepared." The problems lie in the execution:

1) What will create the SHTF scenario? Nobody knows.

2) So one logically should prepare for the "most likely" SHTF scenarios. This is almost impossible if living in the city. It is exceedingly expensive for most country dwellers. I think some farmers/ranchers and the Amish/Mormons are already prepared for a lot of situations.

Now our government is de facto at war with preppers. Accusing them of being "anti-government." When the Soviet threat all but disappeared, our government turned their fearful eyes inward. Along with the constant selling of "sand pirates" hell bent on our imminent destruction.

By insisting on backdoors to everything, CENTCOM has created an extraordinarily huge risk to a hostile governments hacking of our financial markets.....a significant problem.

Yes....the risks are there. One either needs a lot of cash or a lot of time to prepare for many possible risks. Every generation has felt it was the final generation. Someday that generation will be right.

Dave Angelini · January 2016

I do not know about all that but I was born and raised between Superbowl city 2016 and Marin and we always knew a major earthquake was going to happen. My dad always said he hoped we were in Marin at the time and at least we could go north when the golden gate bridge was not usable.

oil pan 4 · January 2016

Xizang said:

UPDATE Major snowstorm hits the US northeast and east coast. Millions without power.

So how impractical is it for folks to invest in solar simply as backup power for seasonal power outages?

During a storm and immediately afterwards solar would be useless unless you had a big battery backup. Batteries used purely as backups are expensive and wasteful. This is when you would want a generator.

Impracticality depends on how much money you have to spend. I put about $1000 into my gas generator to turn it into a solar hybrid generator and only have enough solar capacity to run a refrigerator during day light hours.

MarkC · January 2016

Xizang said:

UPDATE Major snowstorm hits the US northeast and east coast. Millions without power.

So how impractical is it for folks to invest in solar simply as backup power for seasonal power outages?

Couple of suggestions;
1. Try to get techntrek of this forum to give you the latest update on his PriUPS use during major Nor'Easter storms - he seems to have done this successfully (for the generator part), and meanwhile having a useful method of transportation every day. I have a PriUPS system, but have not yet had to use it (no hurricanes have barreled up the Houston ship channel recently). No real maintenance required the past year - just periodic testing for operationals. It is set up to run my 240 volt well pump for water (and some AC), with minimal use of gasoline (months with various storages).

2. Get an electric vehicle that matches your lifestyle and figure out how to use the battery effectively with solar. For me, it's an off-road golf cart that has 4 - 155AH, 12 volt Trojan batteries, PLUS a spare set that is new, but backs up the 5 year old set. When they fail (soon?), I'll simply recycle the old, and put in the new. I'll probably buy another spare set fairly quickly - depends on the "prepper" mood of the country.

I can charge the 8 batteries (48 volt) using the Secure power supply on my on-grid SMA SunnyBoy inverter for an (almost) complete charge on a sunny day. If it really looks bad for a long period, I'll reconfigure the PVs and put a Midnite Kid on line for decent charge efficiency - and live with it. FYI, I keep the spare batteries on a 48 volt trickle/desulfator charger, but "excercise" them periodically with my "off grid" UPS inverter - that is hooked up to run a fridge, some lights, ceiling fans and a TV.

Is this all "impractical"? The on-grid system is paying for itself in about 5-7 years (have a generous co-op electrical supplier). The other stuff I have anyway (exceptions - the UPSs) and my "retirement" is playing with improvements.

However, this system is not very portable!!!

Solar simply as backup to possible grid failure - post SHTF

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Lincoln
Average Solar Insolation figures

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Solar simply as backup to possible grid failure - post SHTF

Comments

LincolnAverage Solar Insolation figures

Categories

Lincoln
Average Solar Insolation figures