A couple years back I wrote a piece for SurvivalBlog about alternative energy in the suburbs. I described a strategy for dealing with a potentially prolonged blackout in suburbia. Essentially the plan is to keep a low profile, by camping in my grid tied, stick built, difficult to defend home. This was accomplished by shrinking our energy footprint by using a well-insulated basement, propane heat and small scale solar to primarily power DC appliances. The article is still available in the SurvivalBlog archives. It is a sound strategy, well within the reach of most suburbanites and could keep many people safe especially if the grid went down over the winter. If you have any interest in this topic I suggest you read it.
Its two years later. God has seen fit to allow me to not only live, but to prosper a bit. I have used this additional time to add additional capacity to my home’s PV system. Power outages are now a minor inconvenience.
In this article I will guide you on how to make your suburban home livable beyond “camping” during an outage using alternative energy. It has been personally tested. A step by step would be a very long article, but this over view can get you going.
The point of view is not just as an alternative energy hobbyist, but as a resilient, suburban prepper. A guy, who is very motivated to avoid large, angry, scared crowds, like the ones at gas stations after Superstorm Sandy trying to get fuel for their generators.
This upgrade was a financial stretch, about $2,800, and took me about six months to construct. I will describe where I did and did not cut corners. For brevity, I will only give a brief summary of each component of a PV system.
Without grid power, I can do some laundry, (washer, but not dryer), run the fridge and furnace enough for them to do their respective jobs, and have hot water. I can do this quietly for a long time. The system runs when the grid is up to lower my electric costs. The hitch is that this is a small, relatively inexpensive system, so I can only do one thing at a time and I have to actively manage use.
Financially, this is may not be a good investment in a traditional return on investment model, although it could add some resale value to the house; it will take many years before savings on my electric bill pays off this system. Staying in my home and avoiding mobs is priceless.
Investments in energy conservation have a much higher return. Energy efficient appliances and weather proofing/insulating also make small alternative energy systems viable by lowering electric and heating requirements.
This is still a work and progress – and your mileage may vary.
Equipment Summary – I used ground mounted DM Solar 145 panels, a used Outback FM 60 charge controller, Wal-Mart marine type 29 deep cycle batteries, a Samlex 3,000 watt, 120 volt inverter, and modified cord set to allow a 120 volts inverter to work with a standard 240 volt transfer switch.
Here are the details-
The transfer switch
My earlier PV system, I had small inverters to convert DC to AC power to run a few very small appliances. Whenever possible I utilized DC appliances (fans, my RV style cooler, battery chargers etc.). There is certainly a limit as to how many DC gadgets one can utilize
Central to my upgrade plan was a transfer switch. The transfer switch allows you to isolate certain circuits from the grid. Your power source whether gas generator or alternative gets plugged into the transfer switch, and when the switch is engaged, electricity runs through your homes wiring to the selected circuits. They are designed so that electricity cannot back feed into the grid and injure utility workers. Transfer switches are safe and eliminate most extension cords.
I purchased a Protran 8 circuit transfer switch made by Reliance from a big box hardware store. The cost difference between this model and larger units in not large, but I wanted to limit the temptation of overloading the system and keep the costs as low as possible. The transfer switch is generally placed inside near the circuit breakers. There were some key differences between this and a typical installation. Most transfer switches are designed for 240 volts and come with two plugs for the power source. One is on the switch and the other is wired some distance in an outlet box, generally outside for the generator. I had the 2nd plug placed in an ideal place for a gas generator and the wire run but did not have the final connection. The plug on the transfer switch was completely wired. If a conventional generator was called for, with 20 minutes of work the outside plug could be connected and the inside plug disconnected. Conversely, less than ideal, I could also run an extension cord through a window to connect a generator to the transfer switch.
I opted to have only one plug wired to avoid any possibility of a situation where power is feeding in from two sources. While I totally understand the system, if I am out the picture, I want to make it safe as possible for those remaining.
Picking the circuits requires some careful thought. I picked my furnace, refrigerator, whole house fan, power vent for gas hot water heater, a few choice outlets, and an ejector pump for the basement bathroom.
I purposely avoided any lights. Lighting requirements are easily met with rechargeable LED lanterns, and flash lights. The clothes dryer, microwave and central air conditioning are out of the question due to the load requirements.
Picking the electrician also requires some thought. Many have little understanding about alternative energy. I ended up with a guy I know from the rifle and pistol club. We have similar political views, but he lives some distance away. I kept my preps out of site while he was around.
Special Power Cord
My inverter (more on inverters soon) produces 120 volts; my transfer switch, like most, is set up for 240 volts.
The step here is to make a special cord that has a 240 volt plug on one end, and a 120 volt plug on the other. The cord is wired so that only one leg of the 240 volt is utilized. The transfer switch is only using ½ of its potential, but that’s the tradeoff for using a small PV system and is enough to keep what I need running.
[JWR Adds: If you ever fabricate any sort of “male to male” power cord or “220 to 120” cord, then you must consider that it might be in the hands of a friend, neighbor, or relative (for example an heir, after your death) with less electrical knowledge than you, and they might end up hooking it up to a generator and inadvertently back-feed the local power grid and put utility workers at risk of electrocution. It is far, far better to pay an electrician to install a more elaborate transfer switch. But at the very minimum, be sure to attach permanently laminated safety wording tags to both ends of the cord!]
You need to know what you are doing to make this 240/120 cord, beyond the scope of this piece to describe. Your electrician can do it, or you can order one from the Internet, I used nooutage.com for my backup cord and my electrician for the primary. Improperly wired cords can be very dangerous, get qualified help if needed.
With this cord, my inverter is compatible with my transfer switch. There are two ways to avoid this special cord, either a 240 volts inverter (way out of my price range), or a 110 transfer switch (limited choices, as most are designed for docked boats.)
The inverter
The inverter takes DC power from your batteries and converts it to AC power for your appliances. Significant power is lost during the conversion. DC appliances are more efficient in that department. There is plethora of inverters available, I don’t have enough space for a complete discussion, but what follows are some of the main points, type, size and outlets.
Inverter type – pure sine wave or modified sine wave
For putting electricity in your household wiring, a pure sine wave inverter is needed. Cheap, modified sine wave, inverters make “dirty” electricity, and they have their uses. If you use a modified sine wave (MSW) inverter then you may damage your appliances, at which point the MSW inverter may not seem like such a bargain. More likely than actual damage is that your Energy Star-rated efficient appliance won’t run properly or run at all. (Mine are erratic with a MSW. I ended up with a Samlex 3000 inverter, made in Canada. I have no idea if they are the best inverter, but the cost seemed comparable. What sold me on Samlex is that when researching, I promptly spoke with knowledgeable people from Samlex, who spent the time to thoroughly answer my questions. You aren’t going to get that from China.
The 2nd issue is size. The size of components could be a complete separate article; a “Kill-A-Watt”current measuring device is invaluable to calculate demand. My transfer switch will take up to 5000 watts, which is adequate for most homes. Plan on at least a 2000 watt inverter for a suburban home for this type of system. Inverters are not a good place to cut costs, buy the largest and best according to your system and budget.
The 3rd issue is the outlet. Many inverters have outlets that are GFI protected, which is an excellent idea when running many individual appliance through an inverter. I do not have space for the details, but GFI outlets from your inverter (or gas generator) to your transfer switch may cause breakers to trip due to floating/bonded neutral issues. From personal experience, If you want to use an inverter through a transfer switch, or to appliances like gas heaters, you can avoid some annoying problems by having at least one outlet not GFI protected. I have read of a dangerous workaround of removing the ground prong from the cords instead – don’t do it. A safer, but expensive work around is to use a 1:1 isolation transformer that eliminates the floating neutral problem. Best is to have at least one non-GFI outlet. Inverters are not a good place to cut corners.
PV Panels-
I saved money here, by buying Chinese panels. There are all kinds of panels out there, with their associated opinions. I went with DM Solar which seemed to be the best tradeoff on price and quality. Panels are highly vulnerable, and I wanted to limit my cost exposure. Time will tell if I made a good choice, but so far so good. Again, sizing of components could be its own article, but 400 watts for a system like this is a good start.
PV Placement- Trade Off between OPSEC and Sun
Panels need to be placed where they can get some sun. There is a tremendous amount of information available about proper placement. My problem as a prepper is to balance these issues with opsec. Roof mounted panels are safe from minor vandalism and can get good sun exposure. The problem is that they are proclaiming from the roof tops that this house has PV power. The other issue is taking them down if I need to relocate or hide them. I opted for ground mount. I can easily access them for movement (as can looters). You might want to keep them in storage and prop them up against a south facing wall when needed.
My solution was to use ground mounted pole system, placed in a fairly sunny, south facing, inconspicuous corner of the yard. I can move them for more optimal placement or bring them in if things are unstable.
For the actual mounts, I went with an US based eBay seller, “markp-017″7. He uses what appears to be a modified satellite dish mount, at a reasonable cost. I only purchased the basic mount and made the frame myself from pressure treated 1×4. The mounts fit standard fence poles; I used 4 foot pieces, mounted in a 5 gallon bucket with concrete, buried 2 foot deep, so the panels are only about 2 feet off the ground, low profile helps keep them out of casual sight.
[JWR Adds: A mount like that would be insufficient in a high wind area–or even in a normal wind area if there is a microbusrt. The larger an array, the more that it acts like a sail. I would recommend using mount with Schedule 80 steel pipe for the post(s). The amount of concrete that you pour around the posts depend on the anticipated wind loading and your local soil. I generally err on the side of over-engineering these projects.]
The mount is capable of holding 4 panels, but when I tested a 4 panel prototype, it was too heavy to lift by myself, so I ended up with 2 panel mounts.
The other issue with placement is distance. The placement needs to be inconspicuous; they may need to be some distance from the house. This means increased wire costs and DC line loss. Wiring the panels in series instead of parallel lowers the amperage and line loss and could be a good solution if the panels are evenly lit and the charge controller is compatible. Another possible solution is double lines, when I buried my lines in a PVC conduit, I used a size large enough to allow future lines.
Charge Controller
Charge controllers regulate the amount of charge the PV panels deliver to the battery. This topic could easily be its own article. They are sized by amps. Try to buy a unit larger than the output of your PV panels for a margin of safety and to accommodate future expansion.
To save money, my backup controller is a no-name, Chinese unit from eBay. I tested it for few days, and then put it back in its box, inside the Faraday cage, where it sits with all the other backup electronics. It was a fraction of the price of an American made unit. I hope I never end up using it, but it does work.
The more sophisticated charge controllers are capable of more efficiently charging your batteries and can help compensate for less than ideal PV placement. As mentioned, the better ones can work with panels wired in both series and parallel, and battery banks of either 12 or 24 volts.
A good strategy may be to buy a quality US charge controller, right after a new model has been introduced. I purchased a used Outback MX60 MPPT. Its priced drop considerably when the new outback model was released. You could save some money, buy using an appropriately sized, inexpensive charge controller from China until a higher quality unit can be purchased. The original could then be saved as a backup.
Batteries 12 or 24 volt
If one were starting from scratch, you could make a strong argument for a 24 volt system, if I were to start again; I would go with 24 volt system. I stayed with 12 volt due to legacy issues with my previous PV setup. Research it and make the best choice for you.
[JWR Adds: I concur that a higher voltage system with a larger number of batteries cabled in series, or in series-parallel arrangement is the best option. A typical starter system would use four 6 VDC batteries cabled in series, connected to a 24 VDC inverter. If more batteries are added latter (typically in increments of four), then the cabling can easily be switched to a series-parallel pattern.]
Battery bank
Deep cycle batteries used in alternative energy are rated in amp hours. Another topic worthy of a separate article. Batteries are a budget issue, they are expensive, and it’s problematic to add additional batteries later on.
The amp hour requirement could be met with fewer, larger batteries, or more, smaller batteries. It’s less expensive to go with fewer, larger batteries. Less wiring costs and the batteries are less money per amp hour. The down side to larger batteries is that they are heavy and that moving them during a relocate could be even more difficult.
I cut corners on the battery bank, and utilized type 29 marine batteries from Wal-Mart. Marine batteries are a hybrid, probably not a good choice for a larger, totally off grid home. I purchased three, 114 amp hour type 29 batteries for $108/each with a two year replacement policy, less than half the cost of a conventional deep cycle battery. I am not sure what the future will bring, but I am pretty sure that if both I and Wal-Mart are still in business in two years, there will be a visit to exchange batteries. Every two years after that as well.
[JWR Adds: Abusing a warranty policy by returning a battery that still holds a charge would be unethical. Be honest, folks and only return goods if they are defective or if they have truly failed within the warranty period. Back when I lived in California, I was sickened by hearing some of my neighbors brag about how they had worked the system to buy gear to use on a short duration camping trip and then returned the items for a full refund, under lenient store return policies. Abusing a warranty or return policy is tantamount to theft.]
Additionally, although I am not a complete novice, I do not have extensive experience with battery banks, if I trash my batteries it’s not as painful with the Wal-Mart type 29’s as it would be a better quality deep cycle battery. You can make your own choices about type and size. My opinion is that for a suburban homes’ backup system the range of 300 amp hours is adequate. Cheaper batteries do not hold a charge or last as long as higher quality batteries.
Wires and Fuses
Wiring holds all this together, fuses help keep it safe. On the advice of the Samlex engineers, I got thick AWG 00 wires to connect batteries and inverters; I also followed their recommendations on fuses. Was an expensive one time hit, but thicker gauge wires are safer and more efficient. I would advise following your inverter manufacturer recommendation on fuses and wires and not cut corners here.
I saved some money by making my own connections and crimps. The 00 wire was too thick for my wire strippers, had to use a separating disk with my Dremel tool. I could have safely used smaller gauge less expensive wire had I used a 24 volt system. The wire for the PV panels was 10 AWG and much easier to handle.
Not Enough Sun
Many off grid homes use a generator to make up for shortfalls in sun light; I have that consideration in addition to relatively small hour amp size to my battery bank. My solution is to use car and truck as a backup generator. When I had the wiring for transfer switch, I also had a 10 gauge extension cord placed with an outside outlet that runs to the battery bank/inverter area of the basement.
An inexpensive MSW 1500 watt inverter from Harbor Freight is connected to the vehicle with an AIMS inverter and alligator clamp and a Scoshe fuse. I don’t think it’s feasible to go much beyond 1,500 watts with a car inverter system. The vehicle must be idling for this to work. I can park in the driveway “nose in”, but near the house [with no risk of carbon monoxide intrusion], with the vehicle’s doors locked, and with a steering wheel lock, to help deter theft. The car inverter/generator is probably less efficient than a generator, but quiet and less conspicuous. My truck can idle for a long time on a tank of gas.
With the electricity from the car generator, I can charge my batteries with an inexpensive Schumacher battery charger, don’t buy larger than 15 amps. I would not recommend this type of charger to maintain the charge of batteries, but it seems to be okay for bulk charging. I can also plug appliances into the outlet or use my modified cord sets and send electricity through the transfer switch. I need to careful what I run due to low available wattage, MSW electricity and the GFI issue. The fridge work and ejector pump work ok, but not the furnace or hot water heater.
Separate PV systems
I alluded to having previously assembled a smaller PV system. It is still in place and running nicely, powering my alarm system, router, television cables box and a few other odds and ends. In a pinch, I could use the old panels and controller to charge my newer battery bank, or my old battery bank with the new inverter and transfer switch. Not a good idea to charge both banks simultaneously with the same charge controllers, but I can connect the banks for extended run time. My opinion is that for a prepper, separate standalone systems are a better, more robust strategy than one larger one. Nothing I have described here interferes with having multiple running systems.
In Closing
I have attempted to give a guided overview of a small PV system, just large enough to run household appliances, that is a resilient option over a traditional generator. This seems to be a segment of the PV market that is over looked. While maybe not a beginner system, it can be assembled and installed by a home handyman with relatively little professional help. I feel it has utility in both TEOTWAWKI or in simply smoothing out the bumps of life when there is a short term power outage. The Yahoo Groups 12 VDC Group was invaluable in this project. I have no commercial interest in any products mentioned.