Solar lights on wintry nights
Most of the activity in the dining hall will be occurring during daylight hours, and the array of skylights and windows will insure that most areas of the kitchen will have adequate natural lighting.
And in those areas of the dining hall where natural light won't reach, such as along the north wall, we've installed "daylight" florescent tubes to provide supplemental illumination sufficient to encourage folks to curl up on the back bench with a good book on a wintry day.
While most of us spend our private time in our private quarters, there are times when you just want to be somewhere else. In summer, that's probably kicking back in a hammock under the shade of one of our old oaks, but in winter, it's likely to be in the dining hall around the woodstove.
Wood heat is "dry heat," so it's a common practice to "temper" the air by leaving a kettle of water on the woodstove. The joy of settling in with a cup of tea and a good book on a snowbound winter day is of the great pleasures of this lifestyle, and we'll want to make the dining hall a good place for that to happen.
And so, one of the design parameters for the dining hall was that it have lots of lighting. Can do, no problem there; but even using the new compact flourescent bulbs, lots of lighting implies a correspondingly large electric bill.
We're currently using around $6K in electricity; on the one hand, that's only about $400 per person per year, which is way below the national average, but on the other hand, it's a number that we don't want to see grow and eat up more of our funds. Every dollar that goes out in operating expenses is a dollar that's not available for construction - it's that simple - so we're sensitive to any change that raises our operating expenses.
There's also a social dimension to this because it's so very easy to leave a commons room and forget to turn off the lights. Everyone does it, and everyone gets irritated at others when they do it. By generating our own electricity we eliminate one source of frustration and discord, and when tempers get short in the dead of winter, that's a good thing.
At each end of the dining hall, there are earthsheltered "cellars" some 14' long and 6' wide. The western cellar will eventually be the dining hall's walk-in freezer; the eastern cellar will be the dining hall's power center.
The dining hall is many things, one of which is an overgrown mounting system for an array of photovoltaic panels. PVs need to be positioned so that they get maximum exposure to sunlight, which translates in practice to facing south and being inclined at an angle roughly equal to 90 degrees minus the latitude of where they're located.
It just so happens that the dining hall faces south, and the slope of the roof matches the correct solar angle for this location. :-) While you can mount solar panels proud of the roof anywhere, it's a lot nicer when they're incorporated into the original design. instead of added on as a clumsy afterthought.
When designing photovoltaic systems, there are three seasons you have to plan for: spring/fall, summer and winter. Given the capital intensive nature of renewable energy systems, you scale the size of your array to match the load you'll be servicing in March or September, thereby creating a system which will cover your needs eight months out of the year.
While it would be nice to be able to rely on PV panels to supply your energy needs year round, that's just not going to happen here in the Pacific-Northwest. Neither is it reasonable to install a really big battery so that you can store up the surplus energy produced in summer for use the next winter. Fortunately, there's now a better option available here in Washington and in most other states too.
That better way is called "net metering." The concept is that in summer, when you have lots of sunshine generating lots of watts, you just pump that energy back onto the grid. This causes your power meter to run backwards, thereby giving you a credit against the bill that you racked up during the winter months.
The result is that all during the summer, when the days are long and we won't need a lot of lighting anyway, our solar panel array will be supplying energy to the grid thereby earning us a credit with the power company. Under net metering, we won't ever get a check in the mail from the power company, and we still have to pay the same meter charge we've always had to pay, but that's fine. Being able to use the grid as a really big battery is a whole lot better than a system in which every household has to purchase and maintain a major battery array.
That being said, we have a major battery array anyway - actually, we have two of them.
While we are committed to developing a sustainable community, and while sustainable energy does have a key role to play in achieving that goal, there's another reason for installing this gear.
Most winters here are mild, but the key word there is "most." On occasion, the snow can get deep and the power can go out for days. It's one thing to hunker down for a day to await the power company getting around to servicing our sparsely populated area of the county, but we've seen power down here for as long as five days in the dead of winter, and I can promise you that by the third day or so, trying to operate a community without electricity in sub-freezing weather becomes a most memorable experience.
The 2x3 battery array
As long as the grid is energized, our most cost effective option is to buy power from the grid - at five cents per kilowatt hour, there's no cheaper way to go. But, when the grid goes down, it's best to have a viable backup plan - and that's where the battery array comes in.
The battery array consists of six 6 volt Trojan L-16s. These puppies weigh in at 113 pounds each and have an electrical capacity of 350 amp hours. Configured as a 12 volt array, that gives us a thousand amp hours of reserve capacity.
The way these systems work is that you even have backups for your backups - and in this case, the secondary back-up is an Onan generator modified to operate off of propane.
An internal combustion engine driving a generator burns fuel and exhausts hot gases. Room heaters burn fuel and exhaust hot gases. Notice the similarity :-) This is where "co-generation" comes into play.
The trick is build a heat exchanger exhaust system for the generator. That way, you can simultaneously heat the room and recharge the battery - two benefits for the price of one.
The dining hall lights are standard 110 volts AC units - and they don't care where the power comes from. In our case, instead of being powered directly by the grid, they're powered by an inverter which takes 12 VDC from the battery array, and converts that energy into a modified square wave at 118 VAC.
At night, the battery array powers the interior lighting. The battery is then recharged by the PV panels the next day, and once the battery is recharged, the rest of the energy from the panels is "sold" to the power company. If we have a series of overcast days, then we can use grid power to recharge the battery array, and if the grid is down, we can recharge using the generator.
All these extra options require extra wiring and extra switches, and extra attention paid to learning how the system works; Jefferson's Law applies. In addition, there are serious safety issues that need to be respected; it's important to not do for sustainable energy what Jim Jones did for Kool-Aide.
Mastering alternative energy systems requires one to master the underlying science and math, one sad reason why it's likely that such systems will remain beyond the reach of most people. While the systems are getting more "user friendly" over time, there's only so much that can be done. As soon as you make a system more idiot proof, The System seems to respond by producing a higher grade of idiot.
Fortunately, it isn't necessary to understand all the underlying science in order to use a renewable system, and one of the key advantages of living as part of an interested team of self-reliant individuals is that there's no better opportunity to learn all sorts of things. Our experience is that everyone brings something to the table of knowledge, and that we as a group are way smarter than any one of us is as an individual.
What is necessary is to pay attention, and while there is a financial cost to gaining a notable degree of independence from The System, I'm convinced that the primary and essential price you have to pay for independence is that you have to pay attention. When the wheel's in spin, if you snooze, you lose - it's that simple. That's why Windward's Third Principle is "Take it seriously, or take it somewhere else."
There are scientific laws that describe how these sustainable energy systems work and which prescribe the limits within which they function; Ohm's law being a good example. There are also less precise laws which describe how systems work within a social context, and these are important too since no technology can function effectively if the operators are willing and able to use it properly.
Ohm's Law describes the relationship between certain characteristics of energy in motion. It states that the voltage observed will be determined by the rate at which the energy is flowing multiplied by the resistance it's having to overcome in order to flow. In more mathematical terms, Ohm's Law is written as E=I x R, where E is the applied voltage, I is the current in amps and R is the resistance in ohms.
This is important because you want the voltage at the point of use to be as close to the input voltage as possible - any loss is wasted energy. Ohm's law points us in the direction of ways we can lower the system's inefficiency, i.e. by raising the circuit voltage from 12 volts to 118 volts and reducing the circuit resistance by using heavier gauge wire.
There are also "laws" which describe the social dynamics involved in using such systems. I alluded to Jefferson's Law earlier; it goes,
"Those who want to be
Ignorant and free
Want what never was,
And never soon shall be."
Another law relevant to sustainable systems advises us that "Systems which work in accordance with motivational vectors sometimes work. System which function contrary to motivational vectors work poorly if at all."
Frank Herbert said it in another way that I've found to be very relevant to what we're doing here; "Perhaps your deficiency rests in the false assumption that you can order men to think and cooperate . . . men must want to do things out of their innermost drives." That's a key part of why Windward isn't big on rules and orders; they work poorly if at all, and come under the heading of "last resort" options.
When a system is "stand alone," i.e. not connected to the grid, then things are fairly straight forward, but interconnecting an on-site generating system with the grid in any way requires the incorporation of mechanisms which make it impossible for the system to be operated improperly.
The primary way this is done is by the inclusion of transfer switches. Finney trailer has a 200 amp grid service, and therefore it had to have a 200 amp switch - something which folks around here call "spendy."
Finney Trailer's 200 amp transfer switch
When the grid is "up," the transfer switch is set in the up position and Finney is connected to the grid. When the grid is "down," the handle goes in the down position and Finney is connected to the generator in the shed. It's always a good thing to wire circuits so that the switch settings are consistent with the effect desired - especially when it's a switch that you don't use very often, or might need to work in the dark or when you're under emotional stress such as in the case of a fire and you're needed to cut off all power to the trailer.
And when the handle's in the middle position, Finney isn't connected to anything thereby making it safe to work on the main electrical panel inside Finney. The key point here is that there's no power configuration in which it's possible for the generator to be connected to the grid.
The dining hall uses 20 amp transfer switches to switch the lighting circuits from grid to internally generated power. Again, there's no configuration of the switches by which it's possible to for 118 VAC power being generated by the Trace inverters to be fed onto the grid portion of the wiring. The lights can be on grid or on internal power, but never on both.
This requires a good deal of wiring, especially since just about every light has its own switch. We want folks to have all the light they want, but to also be able to forego lighting up areas that aren't in use. Yet another example of the way that sustainable systems often require a greater capital outlay up front, but since we're doing the work ourselves, the savings on labor costs more than make up for the added materials.
The reason for the lights even have transfer switches is to that when the internal power system is down for repair or maintenance, the lighting can switch over to grid power. This insures that the primary work of the kitchen can continue unimpeded, and that repairs or improvements can be made without undue haste.
Bob's Battery Box
What we're going to do
Windward Home Page - - - - Notes From Windward, Volume 62