Sagehen Station is my second adventure in off-grid, remote living. I am an admitted junkie with a bad, bad addiction. My drug of choice is first and foremost a natural and powerfully-beautiful landscape. Through the 2000s, I lived off-grid and off-highway at 7,000 ft. north of Truckee on 20 acres. The property's southern border was about 900 ft. of the Little Truckee River. Life in Sierra County was good, a fine place to call home, and a community I am proud to still be a part of, at least on my visits back. I moved onto the Sagehen property in 2011 and have called it my home since.
Living off-grid, as far as I'm concerned, means you are your own utility company when it comes to water, sewer and power. Best if you put it all in yourself, as was the case on my first adventure. But absolutely necessary are the requirements that you are familiar with and capable of troubleshooting/fixing the technologies that are supporting your life. It is for this reason that living off-grid is all about the systems. Today's ramble is about the electricity system.
PHOTOVOLTAICS AND BRIGHT SUNSHINE
PHOTOVOLTAICS AND BRIGHT SUNSHINE
Sagehen Station has just over 4 kw of photovoltaic electricity generation comprised of two fixed-rack-mount solar panel arrays. The newer and more powerful array of 12 panels generates 2.1 kw (175w panels) and the older array of 15 panels generates 1.95 kw (130w panels). I had the newer array installed last summer shortly after I bought the property. Having shivered through two stormy, frigid weeks during the previous 2010/2011 winter during a "trial run" of the house (then in escrow), I realized part of the purchase requirements would include the addition of more power generation. The system, now with two large solar arrays for power generation, seems to run this all-electric home throughout the cold, darker winter months just fine.
BATTERIES, BATTERIES, BATTERIES
BATTERIES, BATTERIES, BATTERIES
To store all this instant, free electricity (free once the solar bill is paid!), Sagehen Station has a large battery bank. The battery bank is made up of 24 Rolls Surrette CS 17P 4-volt batteries.
Battery specifications can be confusing to understand.
To ease the difficulty, battery manufacturers use a standard unit to rate the capacities of different batteries. That unit is the amp-hour. The number to remember is the 20-hr amp-hour (Ah) rate, which provides a usable benchmark across different battery models and manufacturers. In this case, the 20-hr rate is 546 Ah for each 4-volt battery. The 24 batteries are wired in two groups of twelve 4-volt batteries each, each group wired in series, resulting in two individual 48-volt banks (each bank has 12 batteries x 4-volts each = 48-volts). When you wire batteries in series, the voltages add, the amperages stay the same, so the resulting bank capacity expressed in amp-hours is equivalent to the amp-hour rating of each individual battery within the bank. The two individual banks are then wired together in parallel as they power the 48V positive input leg of the inverter. Wired in parallel, the bank voltages stay the same but the bank amp-hour capacity adds. Since each of the two individual 12-battery banks has a 546 Ah rating at 20 hours, the 20-hour amp/hour capacity of the overall system battery bank is just shy of 1,100 Ah (2x546).
Here is Sagehen Station's battery bank:
To ease the difficulty, battery manufacturers use a standard unit to rate the capacities of different batteries. That unit is the amp-hour. The number to remember is the 20-hr amp-hour (Ah) rate, which provides a usable benchmark across different battery models and manufacturers. In this case, the 20-hr rate is 546 Ah for each 4-volt battery. The 24 batteries are wired in two groups of twelve 4-volt batteries each, each group wired in series, resulting in two individual 48-volt banks (each bank has 12 batteries x 4-volts each = 48-volts). When you wire batteries in series, the voltages add, the amperages stay the same, so the resulting bank capacity expressed in amp-hours is equivalent to the amp-hour rating of each individual battery within the bank. The two individual banks are then wired together in parallel as they power the 48V positive input leg of the inverter. Wired in parallel, the bank voltages stay the same but the bank amp-hour capacity adds. Since each of the two individual 12-battery banks has a 546 Ah rating at 20 hours, the 20-hour amp/hour capacity of the overall system battery bank is just shy of 1,100 Ah (2x546).
Here is Sagehen Station's battery bank:
Each off-grid solar power system has three main components. We've covered the Generation and Battery components above. The third component is all of the electrical equipment necessary to channel all that power generation into the battery bank and then to take it back out of the battery bank and convert it into electricity that you can use to power your life, including your lighting, water heating, space heating, cooking, computers, printers, toothbrushes, vacuums, turkey-carving knives, etc.).
OF CHARGE CONTROLLERS AND INVERTERS
OF CHARGE CONTROLLERS AND INVERTERS
Putting power into the battery bank requires Charge Controllers...at Sagehen Station that's the two black boxes bottom-center in the photo at right. In this case, the charge controllers are manufactured by Outback. The power being generated by the solar arrays and going through the charge controllers into the battery bank is direct current, or DC. Then, to get power out of the DC battery bank and into a more standardized form like 120-volt AC (alternating current), the power goes through an Inverter, which is the white box directly above the two charge controllers, the one with the little LCD display in the upper right corner. This inverter is a Xantrex 5548...a 48-volt inverter capable of handling a maximum load of 5500 watts. The white boxes on each side of the charge controllers and inverter house various circuit breakers and act as wiring chases (places to connect the ends of wires to each other).
BUT WHAT IF SOMETHING GOES WRONG
BUT WHAT IF SOMETHING GOES WRONG
If your off-grid hideout is in an environment that occasional throws deadly weather your way, I advise having some type of redundant backup system that can keep you safe and warm in emergencies.
The backup to Sagehen Station's solar power system is a propane generator. This is a Kohler 8 Kw propane generator. The generator conductors cable into the inverter, just like the cables from the battery bank. The inverter switches the house electrical panel feeds back and forth when necessary, either from the batteries or from the generator. All of this switching can be done automatically, depending on the charge state of the battery bank, or it can be done manually (my recommendation). I am happy to report that my generator sat idle all winter long, never needing to provide supplemental power.
YOU GET WHAT YOU PAY FOR
Sizing and cost considerations for solar electricity systems can be all over the board, and if you ask 10 different "experts" to suggest system components and sizes, you'll likely end the day confused with 10 different recommendations. And until you live in a solar power home for awhile, you won't know how any particular system is going to respond. You sort of "sail" a solar home much like you sail a boat...making small adjustments here and there, watching how the system responds, then altering some of those adjustments maybe, all in an effort to get your lifestyle adjusted "with" your system. With the above caveats, here are some rough guidelines to make general concept decisions with:
Regarding photovoltaic panels, I run this 1,550 sq ft home successfully through the year, including the cold, dark winter months, on 4 Kw of generation capacity. That's 2.58 watts/sq.ft. of house. In Truckee, a 2.8 Kw system runs my 1,132 sq ft home (for sale, by the way), which calcs to 2.47 watts/sq.ft. My lifestyle has grown sensitive to depending on solar electricity, but I burn plenty of lights and operate standard electric appliances in a manner not so different from the average grid user. Unlike the Sagehen system, the Truckee system does not heat water or power a stovetop. The two photovoltaic capacities feel very equivalent to each other. General rule to live pretty normally here in mid-latitude California would be 2.5 watts of photovoltaic generation for every foot of living space. Midrange current costs for installed photovoltaics, ground-mount, is somewhere around $5.00/watt. So a 1,000 sq ft home would require 2,500 watts of photovoltaics costing $12,500 (1,000 sq.ft. x 2.5 watts/sq.ft. x $5.00/watt). You can see that going off-grid is much less painful with a small home.
Battery costs are increasing relative to photovoltaics. Eight years ago my 1,375 Ah battery bank in Truckee cost about $10,000, not including installation costs (I install and I don't pay myself very well). Today the same battery bank would run closer to $16,000. For the Truckee house, that's just over $14.00/sq.ft. at today's prices. Here at Sagehen, current material costs for the 24 battery Rolls Surrette CS 17P battery bank (1,100 Ah) would be roughly $15,000, again not installed. That calcs to $10.00/sq.ft. I'd be happier with a slightly larger battery bank. So maybe $12.00/sq.ft. is a fair mid-range figure for a really quality battery bank.
Electronics are electronics, and the number of battery charge controllers and the size of the inverter are mostly dictated by the capacity of the photovoltaic generation and size of the battery bank. One detail to be very aware of, however, is whether or not the inverter you install is a modified sine wave inverter or a pure sine wave inverter. The former puts out electricity that approximates that from the utility companies, but that includes a few little bumps and hiccups in its flow characteristics. Some of these irregularities can cause problems for SOME electronic devices like computer printers and LCD readouts. A pure sine wave inverter provides a perfectly "clean" type of electricity, cleaner than electricity provided by the utility companies, and won't cause problems for any equipment. And, yes, going the pure sine wave route costs more money. Both inverters I have experience with are pure sine wave inverters. I have friends with a modified sine wave system, and they have burned out (literally, as in fire) two gas ranges that had LCD display panels.
When I installed the Truckee system in 2003, each of the three components - the photovoltaics, the batteries and the electronics - cost roughly the same, or one-third each of the total cost of roughly $28,000 (equipment only). Today, I believe the photovoltaic component will be a little less than a third, the batteries will definitely be more than a third, and the electronics will be similar to their 2003 price. For general consideration decisions, then, a fully-functioning, free-standing solar electricity system (no grid power available) is going to run $30-$35 per sq.ft. of living space, or $30,000 for a small home. The backup generator adds another $5,000 to that.
You can see that solar power is not cheap. It takes somewhere in the 20-year range to recoup all costs through savings on month-to-month utility company bills. That's a long time. But because the systems work so well, they do add instant resale value to any home. Of course the largest benefit is that solar power makes living far off the grid these days very possible. And beyond the mere economics of going solar is the extraordinary satisfaction of deriving all of one's household power needs from the sun. It is good for the environment, and it is good for the heart. Here at Sagehen Station, the sun shines bright, and the lights and water heater and stove turn that beautiful sunshine into Internet surfing, nighttime reading, delicious meals and long, hot showers. Electricity costs will go up as fossil fuels take a heavier and heavier toll on our world. My utility company is our solar system's gentle star, and it won't let me down for a long, long time.
-gmm
