Batteries, High Winds and Other Off-Grid Considerations

http://www.motherearthnews.com/renewable-energy/batteries-high-winds-other-off-grid-considerations.aspx

 By Cam Mather

I’ve been doing some consulting work lately for people who are contemplating going off the grid, so I thought I’d incorporate some of my thoughts on this along with some answers to questions we’ve recently received from our blog readers.

For most people, the decision to be on the grid or off grid is an economic one. If your property is $20,000 from the nearest utility pole, then you’re probably further ahead to go off grid. This is especially true for a remote cottage or cabin that may only be used in the summer months. In this situation, going off grid makes complete sense.

But if the electricity lines are close to your property, it’s a tough call. I love living off grid. It’s been a huge pain in the butt from time to time but I’m glad to be off-grid. Getting your electricity from someone else is just so easy compared to making it yourself. And 14 years ago when we started our little odyssey it was even more of a challenge. We’ve shared many of these challenges in our book “Little House Off The Grid: Our Family’s Journey to Self Sufficiency.” I share the problems we’ve had with most of our systems… solar, wind, batteries … you name it, and I also share our solutions.

Now that we’ve dealt with the various challenges and the system is working well, I love it! When was the last time you turned on a light switch and marveled at the miracle of it? It never ceases to amaze me that I can power our home and business with the sun and wind. It’s totally awesome.

The biggest challenge for many people who want to be off-grid will be the batteries. We started with a room full of Ni-cads that the previous owners got out of a decommissioned military bunker. They seemed to work all right for a while, but eventually they needed to be replaced. Whenever I talk to people who are on the grid and complaining about their latest electricity bill, I like to remind them that I don’t have an electricity bill, and that I’m not paying my share of the utility’s “debt retirement charge.” Then I remind them that I just spent $4,000 on batteries. They are great batteries that should last 17 to 20 years, but they still need to be maintained. They are the biggest and really the only part of my system that requires any on-going maintenance. I have 6 large 4 Volt Surrette batteries wired at 24Volts.

My battery charge controller can tell me the “voltage” of my batteries but periodically I have to check their specific gravity. This involves me putting a “hydrometer” into the electrolyte, which is sulfuric acid. This stuff is dangerous so I need to wear eye and hand protection. If you get sulfuric acid on the your clothes it will burn holes in them.  I compare the reading that I get with the manufacturer’s specifications to make sure that their state of charge is what the voltage is telling me. From time to time I have to add distilled water to the batteries to replace what’s been burned off during charging.

Periodically I also have to equalize the batteries, which is a regulated overcharge of them to make sure they are all at the same state of charge. During equalization, the batteries produce hydrogen gas, which is explosive. Our battery room has a vent to the outside but I usually open the window when I’m doing an equalization just to make sure to get lots of airflow. If you are building a battery enclosure from the ground up you’ll need to make sure that there is a way to ventilate the hydrogen gas that is released from the batteries during charging. You might consider putting them in a garage or an outbuilding, but you’ll need to keep them from freezing, which will effect your decision. The efficiency of batteries will decline as they get colder (think of starting your car on a bitterly cold morning) so the warmer you can keep them, the better. The better you treat your batteries the longer they will last so unlike solar panels that you just put up and forget about for 30 years, batteries will require some maintenance and monitoring.

One of the other challenges of living off grid is the use of a generator. In this climate, the months of November and December are dark (shorter hours of daylight) and often cloudy. If you have a few days of dark, cloudy weather you’ll probably have to run a generator to charge up your batteries. Your generator will be powered by a fossil fuel like gas, diesel or propane. After 14 years here we finally have our system working well and generally we only have to run our generator 2 or 3 times a year and only if we have an extended cloudy period with little wind. Prior to upgrading our solar panels and adding our wind turbine we’d have to run it 10 to 15 times a year.
You can set up your generator to be fully automated so that it automatically starts and charges your batteries whenever their voltage gets low, but I still run mine manually. Again, some people would consider this a hassle. I think that it’s important to understand how the system works so that if it breaks I can fix it.

I think this is the real joy of living off grid. I have control. I’m not reliant on some person somewhere else to maintain the quality of my life. When I see how often other people are without electricity because of snowstorms, or floods, or hurricanes, I can’t imagine living any other way. The people interviewed on the news are always angry about being without electricity. Well, they can make it themselves, if they choose to. It’s not for everyone, but I love it.

Wind Load on Trackers

On other note, a blog reader recently asked about the danger of wind loads on solar trackers. Yes, this is a reality, which means that they should be properly engineered. Putting a bunch of solar panels up on a big pole is like hoisting a sail, only in this case you don’t have a ship that you want to move, and you want everything to stay in place.

Commercial trackers today are designed to withstand high winds so there’s no reason not to go with one. Sometimes really large trackers will have an anemometer on them (the little whirly gig that twirls around and measures wind speed.) Those trackers are designed to automatically move the panels to a horizontal position to minimize wind load when the wind speeds reach a certain threshold.

My neighbor Ken built my trackers (I helped a little bit) and they have weathered some horrendous winds marvelously. I hate watching them getting buffeted by big gusts, but they take a lickin’ and just keep on tickin’. The key to any system is to engineer and install them correctly. A tracker is not something you should skimp on. If it is suggested that you use a certain amount of concrete for the base, use at least that much, or more in the hole. It may be calm the day you install it, but trust me, some blustery day you’re going to watch that tracker get pummeled by a high wind and you will NOT be saying to yourself “Gee I wish I’d put LESS concrete in that hole.”

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Photos by Cam Mather. For more information about Cam or his books please visit www.cammather.com or www.aztext.com