How We Get Our Energy

Well, we're one year in and...we've learned a lot and we're not ready to give up yet.  I must admit, the engineer (a.k.a. geek) in me has really gotten a kick out of studying and maximizing the efficiency of our energy system.  There are several ways to survive/thrive off-grid.  Here are few in no particular order:

1. Hire a company to design/maintain a state-of-the-art renewable energy system designed to meet all of your needs.  
2. Buy a lot of propane.
3. Scrape together what you can to get by and go to bed when the lights go out.  
4. Use less energy.

Most people I've met that live off-grid in Montana do a combination of #2 , 3, and 4. Not many people get by completely with number 1. The people we bought the house from tried to get by with #1 and a fair bit of #2.  They bought a good system.  Unfortunately it wasn't designed very well for them and they never really embraced the idea of energy conservation.  I feel like we've done pretty well on the energy conservation side things (more on that later).  We have also learned that you're better off learning how to maintain your system yourself than relying on any company to take care of it for you.

So here are the nuts and bolts.

Energy Producers:

• Solar: We have ten 150w solar panel with a total energy producing capability of 1500w in full sun. They are mounted on a stationary pole and no, they don't "track" the sun.  We could add a sun tracker and may at some point.  The concern is that it may be more trouble than it's worth since we get so much wind.  

• Wind:  We have a 1000w Bergey wind turbine.  Bergey is a reputable company, but the wind turbine never really functioned properly for the first winter of use.  It produced very little power and was extremely noisy.  Enough so to keep us awake at night.  By spring, the power production dwindled down to zero and we knew that it was time for maintenance.  With longer summer days (and plenty of solar input), we opted to lower the tower in May and perform repairs over the summer.  Turns out the rectifying unit (the part that converts the AC to DC current) inside the wind generator completely burnt up.  The turbine blades were also in need of replacement.  We contacted Bergey and they replaced all parts under warranty.  We finally raised the tower again last week.  So far it runs like a champ and is a lot quieter.  It will be nice to have this winter.    

I suckered a group of friends into helping me lower the tower.
We got the tower about 10% of the way down before raising
the tower back up and running away with our tails between our
legs.  100' is a long way up!  Some things are better left for the professionals.  

• Generator: Kohler 12 kw propane standby generator.  Our goal is to use this as little as possible, but some use is unavoidable.  Having enough solar and wind to account for every day of the year in Montana is an expensive proposition.  A more realistic solution is to size the system to meet your needs for the majority of the year and use a generator to get you through the darkest of days.  Last year, we used our generator about a total of 75 hours.  Just for comparison, the previous owners put 3500 hours on it in roughly 4 years.  That was after they burnt up their first (undersized) generator.  The generator comes on automatically when then batteries get down to a certain voltage.  Once it comes on, it generally runs for a couple hours and shuts itself down after the batteries get back into a comfortable range.   

Energy Storage:

Batteries and lots of 'em.  (This part gets a little technical.) When we first moved in we had twenty  6-volt batteries. Each battery has about 400Amp-hours of storage.  To put this into perspective, an average car battery has about 100 Amp-hours of storage.  Since our batteries are 6-volt, however, it takes 2 batteries, wired in series, to make a 12-volt circuit with 400Amp-hours. So, 2 of our batteries have about 4 times the amount of storage as a car battery -- we have 20.  However, since our system is designed to run at 24-volts, it actually takes 4 batteries wired in series to make a single 24-volt circuit.  Since we "had" 20 batteries, we had 5 sets of four batteries, each set was wired in parallel which increased our total capacity to 5 x 400 = 2000Amp-hours (or 48,000 watt-hours). What does this mean?  Well, since we use about 4000 watt-hour per day, we should have 12 days of storage, right?  Nope!    

• Problem 1:  Batteries should stay above 50% at all times.  That drops us to 6 days.
• Problem 2:  Batteries like to be fully charged every day or at least every few days.  We don't generate enough power to charge that many batteries.  Here are all the details if you want to know why.  

So we have lots of good batteries, but because they haven't been taken care of, they are dying young.  Based on my recent calculations, our current system and our needs, we are much better off with only 8 batteries.  I am in the process of pairing down our batteries to the best 8 and we will give that a try for a year.  Hopefully we can keep them charged and make them last a little bit longer.  A few of the batteries have already expired.  The rest we will keep in storage, and charge a couple of times of year, cycling them into duty as other batteries die. Eight batteries should give us roughly 2.5-3 days of storage.  We rarely have a 3 day period where the sun doesn't come out or the wind doesn't blow.  Even if that happens, that generator will come on automatically anyway.  We can live with that.  

Energy Use:

Since our batteries are wired for 24-volts DC, do we need 24-volt appliances?  Nope. Our house is wired just like everyone else's, with both 120V and 240V AC outlets.  Two, 3500-watt inverters convert the electricity into AC current.  Having 7000 watts of capability means we have roughly 50 amp service.  Most people who are connected to the grid have 100 amp or 200 amp service.  To be honest, we rarely use more than 1000 watts at any one time, so this really isn't a problem for us.  It does mean I can't run woodworking tools with large motors, but that's about the only downside so far. 

Energy Conservation:

According to the U.S. Energy Information Administration, the average American household uses about 29kw hours of electricity each day.  We don't really have a good monitoring system, but we estimate the we average about 4 kw/day.  We are going to invest in a monitoring system as soon as we can fit it into our budget, so then we'll have a much better idea.  Here are some steps we've taken to lower our energy usage:

• Lighting: All of our lights are compact florescents and we turn them off when we're not using them.  In the grand scheme of things, lighting accounts for a very small percentage of our total energy usage. 
• Deep well water pump:  We have a very efficient water pump for our well that runs directly off our batteries.  Although it doesn't have very high capacity, it meets our needs and uses very little energy.
• Refrigeration:  Our refrigerator and freezer are certainly unique.  A standard stand-up fridge uses about 2000watt-hours per day!  This varies widely.  If you're interested in lowering your energy usage, take a good look at your refrigerator.  We don't have a stand-up fridge.  Instead, we use a chest-freezer and regulate the temperature using an external thermostat designed for beer coolers.  Packing a chest freezer took a little getting used, but the benefits in energy savings are significant.  Freezer are inherently well insulated and since the door is on the top, the cold air sinks to the bottom when the door is opened.  In a stand-up fridge, much of the cold escapes when the door is opened.  This freezer-converted-to-fridge design uses about 300 watt-hours per day.  We also have a solar-specific chest freezer. It is super-insulated and runs directly off our batteries.  It runs on about 600 watt-hours per day.  So, we use under 1000 watt-hours per day on refrigeration, with a lot of food-space capacity.
• Space Heating: First of all, our house is very well insulated.  A central wood stove easily keeps the house in the 60's even on the coldest of winter days.  The house is equipped with in-floor heat, powered by a propane boiler, but so far we haven't used it very much.  Firewood is plentiful and we just don't really like the idea of burning propane if we don't have to. We used roughly three cords last winter to keep us warm and happy--not too bad for a Montana winter. In the long run we are hoping to incorporate some solar hot water heaters.  If we design it right, we will be able to pump the hot water through the floors on sunny winter days.  
• Water heating:  We have an on-demand propane hot water heater.  The on-demand aspect of it is efficient, but we hope to limit our use of propane once we install solar hot water heaters.   We also hope to install a hot water heating coil in our wood stove which will help distribute the heat through the floors. 
• Cooking:  Our stove and oven are propane.  OK, not really energy efficient, but we sure like it.  This is a luxury that we are unlikely to give up. 

Otherwise, we live pretty much like everyone else.  We have a computer (with satellite internet), a big screen TV, and most modern appliances.  We are a lot more conscious of the energy we use and both like that aspect of it.  We also feel like we are much more in tune with the weather and what's going on outside.  It's been a great experience so far!