Energizing your off-grid homestead.
A solar array is the heart of your off-grid power system
In this series, we are considering the very basic steps that would allow anyone with average skills and the requisite adventuresome disposition, to successfully establish an ‘off-grid’ homestead. Going off-grid requires some of the same ‘spirit’ that many of our forefathers had when they first came to America in the 1800’s, taking their families into the wilds to establish their homesteads.
So far we’ve covered; choosing a piece of land and improving the access to and across the land. In this article we’ll look into getting some electrical power online to support the ongoing development projects.
Honda makes a very dependable line of portable generators
When you’re starting out with your off-grid project, you will need an interim source of reliable power, possibly for many weeks while you’re constructing your permanent power systems.
The Honda generator pictured above has more than 500 hours and still runs like it’s new! And it provided us with reliable power for many power tools, as well as powering our 5th wheel for many weeks. The key to reliable endurance with small engine driven generators is regular maintenance with high quality lubricating oil. I prefer to use the tough synthetic oils in these hard working small engines.
AGM batteries like the one pictured above are great; because they are sealed, acid spills aren’t a problem
We also have a 250-watt Sharp solar panel on the roof of the 5th wheel that is connected to two Lifeline group 27 AGM batteries via a new technology (high efficiency) MPPT charge controller. I installed this system for use while we were touring off-road in various wilderness areas, and it also served to keep the RV energized when the generator was offline.
There are also some other excellent interim power options that can provide power for initial off-grid operations, which can also serve folks in the city during emergency power outages as well as during camping trips, such as the solar generator pictured below.
The photo above shows the ‘Lion’ solar generator system that is available through SurvivalBased.com
Another consideration during initial operations is the need for 240-VAC power for big tools like my Miller wire-feed welder, and in our case, to power a 3-hp. submersible well pump. Powering this kind of equipment requires a large generator capable of at least 30 amps at 240 VAC (7,200 watts). Electric motors are tricky because they can use double (sometimes triple) the power for an instant during startup. So it is important to have a generator that has a ‘surge’ capacity that is considerably more than the continuous wattage needed (watts = voltage X amps) for nominal operations. In the case of our 3-hp 240-VAC well pump, the placard shows it draws 16-amps at 240-VAC. However, on startup, it actually draws about 30 amps for an instant. In order to handle that momentary load, as well as the running load, we acquired a Honda 10,000-watt gasoline generator. It has outputs for both 120-VAC and 240-VAC, and provides a max ‘surge’ power of 10,000-watts, with a continuous output rating of 7,500-watts.
Cement blocks and 1-1/8” subflooring (plywood) makes a stout temporary work bench
This generator also powers my Miller wire-feed welder, which is very handy when you’re building things using steel, such as frames to support solar panels.
So now that we hopefully have some reliable interim sources of power for living and for our power tools, let’s talk about the next steps:
Based upon several factors, including the fact that our building site has a direct line-of-sight with the sun all day long (summer and winter; not withstanding clouds) we decided to go with an all-solar electrical system.
Generally speaking, the return on investment for wind-power (cost of equipment vs. energy produced over time) doesn’t make sense for most off-grid homesteads when compared to solar, so I am not going to go into any wind-power systems in this article, even though I have used them extensively on boats. And locations where there is consistent wind of an adequate velocity are usually not ideal for a homestead.
There are many choices in solar panels these days so you need to do your homework. We made the decision to go with panels made by Sharp, since we have experience with those panels and they have proven very durable. That said, brand name solar panels are a bit more expensive than some of the new-comer solar panels, some of which I am told are of good quality. The insurance you have is provided by knowing your supplier. SurvivalBased.com has some great basic panels that they sell and they are a very reliable company, which eliminates the risks of buying expensive products over the Internet (or the phone).
If you are looking to build a large multi-kilowatt solar array, then you may need a commercial supplier for the big panels and the accessories that go with those panels. After shopping around and meeting some of the people in the commercial solar industry, I ran into a former aircraft mechanic and electrician in Portland, OR by the name of Miles Heiner who has changed vocations and has become a provider of quality solar equipment. Besides being a great guy, Miles is a fountain of knowledge and is a good person to know if you’re going to design and install your own solar system and ‘do it yourself’. (Miles Heiner: [email protected] / Lightharvest solar / 503-501-7733).
Working with Miles, I designed an upgradable 2,000-watt solar array that nominally puts-out 70 VDC and 28-amps with full sunlight (output varies with sun-angle and cloud cover). The solar panels feed into new technology MPPT charge controllers (http://www.lightharvestsolar.com/charge-controllers.html), which in-turn monitors and keeps the large battery bank charged and equalized.
Proper battery cabling ensures function, safety and access to water the cells
To increase efficiency and redundancy, we decided to utilize a 24-VDC battery system made up of three groups of four 6-volt L-16 batteries that are wired in series providing 24+ VDC per group (when you wire batteries in ‘series’ the voltages are added together). We chose the Trojan L-16 (6-volt) batteries for a couple of reasons; First, they are more available, as opposed to some other brands in the marketplace should a replacement be needed. And they are in my book, in this application, more cost effective and the more expensive brands. All things being equal, and with proper battery care (using only steam distilled water in the cells), field experience with these particular batteries shows they will last about 5-years, and up to 7-years, depending on how they are cycled. There are batteries of the same size that cost almost double and will last up to 10 years nominally, but in our application, and given the regular advancements being made in battery technology, we went with the Trojan brand and hedged our bets.
Prior to taking delivery of the chosen batteries (in our case, twelve 6-volt Trojan L-16 batteries) you should have your battery box built and ready to accept the batteries (you don’t want them sitting outside in the elements waiting for a home). One important consideration is the weight of your battery bank; in our case we are looking at about 1,500 pounds of weight (batteries and cabling). I poured a small cement foundation that was dug into the ground (earth coupling for thermal value) and on top of that I built my battery box. The bottom of my box is a piece of 1-1/8” sub-flooring that is treated and coated with epoxy. The sides and top of the box are also treated and epoxy coated ¾” plywood. I lined the bottom of the box and 8” up the sides with EDPM pond-liner material to protect the box from any acid that could accidentally spill. And finally, I added 2” of rigid foam insulation to moderate temperature changes. Another important consideration is the venting of the box to eliminate the explosive hydrogen gas that is generated by the batteries. Hydrogen gas is lighter than air, so the majority of the vents need to be at the highest point inside your battery box. And to accompany those vents, you should have an intake vent down low on the box. All vents should be screened to keep insects out and designed so that rain and moisture cannot enter the box.
Once the batteries are correctly oriented in the battery box, you can begin the cabling process. When moving batteries I like to take a few precautionary measures:
- I place a protective plastic cap or wraps of electrical tape over the battery terminals so they cannot be accidentally shorted; and,
- I make sure the cells are not too full; and,
- I sprinkle a light coating of baking soda on the outer edges of the tops of the batteries, which will neutralize any small amounts of acid that might leak out of any cells as the batteries are jockeyed into position. Once the batteries are in place, I sweep the baking soda off the tops of the batteries down into the battery box using a paint brush. The baking soda in the bottom of the box is not wasted and will neutralize any acid that might find its way down into the box.
Some of the basic parts and tools you’ll need to do your cabling job
Building your battery cables is a time consuming process, but it’s well worth it. Factory made cables are not up to snuff in my book. I like to both crimp and solder all my cable ends onto the cables. If you do it this way, your cables will not fail and your cables will conduct the needed amperage without losses that result from crevice corrosion in the cable terminal ends that occurs over time. I also like to use MAPP gas as opposed to propane for my soldering torch since it burns much hotter and speeds the time needed to heat the heavy cable and terminal ends to the temperature to accept the solder. Another tip is; don’t scrimp on the solder; fill the terminal end where the cable enters until the solder starts to run out. This eliminates any voids where corrosion can take a foothold.
Capt. Bill fabricating the steel frames for the solar panels
Solar panels must be securely mounted to a very solid framework. You can buy commercially made mounts, some of which have additional features, including the ability to track the sun as it arcs through the sky. But tracking frames are expensive, use a little power, and are a possible point of failure. In some areas, the panels and framework will have to withstand wind velocities and gusts up to 100 mph, and possibly more. This is why I decided to build my own frames using 2” X 1” X 3/16” steel channel.
Installing the panels to their frames requires care and planning-ahead
Once your chosen frames are in place, the next step is to securely mount the panels to the frames. The frames and panels need to be rock-solid. Because of the angle they form to the oncoming winds (from many directions), panels can oscillate if not properly mounted, and that is not good; oscillations generate vibrations which can loosen hardware and work-harden framing leading to metal fatigue over time.
On the left side of the photo are two MPPT solar charge controllers and a 5KW inverter on the right; note the ‘added’ 40-amp fuse holders (back with red wires) going from the converter outputs to the batteries.
Now that we have our batteries safely inside their waterproof house and our solar panels securely mounted on the roof of the storage container, we’ll use the interior of the storage container as the location for the electronics that control the system.
So the way this all works (simply put): The electricity from the solar panels flows down the wiring from the roof and in through the side-wall of the container using the heavy grey sheathed 10 ga. wiring. I used heavy duty 240-volt burial cable because it has a U.V. resistant sheath and solid copper 10 gauge wire leads. We wired the panels in two groups, each having its own charge controller that feeds the batteries. The 10 gauge wire going from each group of 4-solar panels can easily carry the current (amperage) from the panels since we wired and are running the panels in a combination of series and parallel, thus producing approximately 70 volts DC to each of the two respective charge controllers. The charge controllers we picked can accept and use voltages as high as 100-volts DC from any solar panel (or group of panels) and will deliver up to 40-amps at 24+ volts D.C. into our 24-volt battery bank.
To recap; we have our twelve 6-volt batteries wired so that they form three 24-volt battery banks that are wired in parallel, resulting in a 24-volt battery bank. Each charge controller handles 4 of the eight solar panels, with each of the two groups of solar (4) panels producing about 1KW into their respective charge controllers. And each of the 2 charge controllers sends about 40-amps at 24-volts (peak) into the 24-volt battery bank.
As it becomes apparent, there is built-in redundancy in this design; if one charge controller fails, the other can still provide charging capacity. If one or more solar panels are damaged in the same group, the other group can provide energy to its charger and thereby to the battery-bank. And of course, if a 6-volt battery fails, that 24-volt group of batteries can be taken off-line, and the remaining two 24-volt groups can handle the load requirements (at a reduced rate of discharge of course).
The final element in the system is the conversion of the 24-volts D.C. from the battery bank into 120-volt A.C. to run the homestead, which is accomplished through the use of an inverter.
Most RV parks have 30-amp 120-VAC circuits for utilization by most RVs. Some really large RVs use 50-amp 240-VAC circuits. In our case, we are wired for 30-amps and 120-VAC. So, converting this to wattage, we arrive at approximately 3,600-watts peak load. In consideration of the fact that we have never needed more than 3,600-watts, and usually use much less, we chose a high efficiency 5,000 watt inverter, which gives some overhead capacity. And to increase the system efficiency, this inverter uses 24-volts D.C. input power from the battery bank (matched to our battery bank), as opposed to the more common 12-volt D.C. version.
When installing the inverter, it is very important to have a properly rated and classed fuse in series between the inverter and the battery. Instead of fusing our inverter to its maximum rated output of 5KW, we fused the input cable to the inverter at 4.5KW as an added safety measure, since the circuit breaker at the load (at the RV) is rated at 3.6KW. So we have a class ‘T’ fuse that is wired in series on the B+ battery cable terminal, with the fuse located within 12-inches of the positive terminal on the batteries. And the positive cable from the inverter makes its connection at this point, with the fuse between the inverter and the batteries. We also installed a properly rated ‘class T’ fuse on the negative side of the circuit in the same manner for extra protection. It’s advisable to check with your local building and electrical codes for compliance with the low voltage and high voltage requirements as well; it’s all about safety!
Trenching is so much fun… not!
Of course the 120-volt AC output from the inverter is run via approved cabling to a power pole and electrical box that is wired with a suitable 30-amp circuit breaker and 30-amp female receptacle. We decided that since we would be using an all-underground water pipe-system, we would use the same trench to also bury our 120-VAC electrical wiring using suitably rated waterproof conduit.
As of this writing, we have been living off the grid and powering everything we want (refrigerator, freezer, satellite system, household appliances) without any problems, and it has been down to 18-degrees and cloudy for several days at a time; no problems! Of course at this point in time, we don’t have the wattage requirements of a full-on household.
The beauty of a properly designed system is that it can be upgraded as the demand for more power arises. Upgrades can be done incrementally by adding a couple solar panels at time, along with additional batteries (assumes there is designed overhead available in the chargers and inverter). Sizing your solar system should be accomplished with the help of someone who has experience with both the equipment (panels, chargers, batteries, inverters) and with doing the load calculations based upon your local solar situation. Obviously the system for a home in Arizona would be vastly different than the same exact home and power demands that is located in Seattle, WA due to sun-angle and annual cloud cover.
So, now we’re down to developing a permanent water system, which is the subject of the next article in this series, so stay tuned for some more interesting ideas!
Being prepared today means being ready for tomorrow!
Cheers! Capt. Bill
This post originally appeared at SurvivalBased.com. Reprinted with permission.
Photos courtesy of the author – copyright 2014