Sunday, April 05, 2009

Solar Project

We do a lot of things the Crunchy Granola way at our house. It's not so much that we're a bunch of tree hugging hippies but that we're professional cheapskates. As it turns out, buying local produce and meat is super affordable and the fact that it's way healthier for your is a nice bonus. So we've got freezers full of free range, organic meat; bags and bags of locally grown, organic produce; and a host of other goodies that save the planet and the pocket book.

All of this is in pursuit of lowering the bottom line. With The Missus staying home with the Short People bringing home the bacon falls on me. We're still a two income family, I just happen to be both of those incomes. So we've done a lot of things like replace most of our lights with compact fluorescent bulbs, significantly lowered our thermostat, and even gone as far as to make the majority of our food on site. Now we're looking for additional ways to cut back.

Getting "off the grid" is often associated with the type of folks you find living in desert compounds with large stocks of automatic weapons and possibly an affinity for Kool Aid. That's not us, we're just pinching pennies. We're definitely not at the point of trying to power the whole house with wind or solar, it's just not economical. But with a few windfalls and the available (cheap) technology I'm thinking I might be able to get a partial solution going.

Working at the hospital I come across all sorts of gear that's getting thrown out because the law mandates it. Of particular interest are the UPS systems that back up critical gear in the event of a power outage. Most are tiny little things that are just meant to run a computer for a few minutes until the generator kicks in but some of them run machines that are the size of a Volkswagon. So now I'm at the point of saving $300 to $500 on an expensive controller and inverter because I'm actually doing the hospital a favor and saving them the disposal fee.

The problem with most alternative energy solutions for homes is that they just cost too darn much. It's an economy of scale issue as well. Taking one small load off the grid can easily cost hundreds of dollars. Dollars that you will never make back in savings before the equipment ages out. Doing a larger project makes the ratios more favorable but you're still just a hobbyist playing around with batteries and expensive electronics and not a frugal homeowner saving money. Free stuff put me ahead in the game, scrounging is what it takes at this point in the evolution of alternative energy.

So... now that I've got a self contained box that is ready, willing and able to run the entire second floor of my house all I need is a method to charge the batteries and some switching and monitoring equipment. Anyone looking for the technical jargon has probably already clicked on to something else by now but here I go anyway. The following is not something that you want to undertake unless you have a very good understanding of both AC and DC power. If you don't and you still feel like tinkering you should invite an electrician and an auto mechanic over for a barbecue and get the free advice going that way.

I'm going to start by disabling the circuit that charges the battery bank from utility power. I'm going to substitute a small solar panel and charging circuit. That will have to be purchased and it looks like about $150. With the UPS installed in the basement and the charger hooked up I can then route the AC output to the circuit that runs my second floor.

Side note: most modern homes would have a separate circuit for each room and likely a general lighting circuit for a similar area. My home was re-wired in the 1970s when there wasn't so much electrical draw, a light and a couple outlets to run very light loads were all that was expected. A single twenty amp circuit covers three bedrooms, a hallway and a bathroom and never trips because the load for that area is still very low. (Unless someone is running the hair dryer) This makes it an easy way to take a large area of my house off the grid as an experiment, one circuit, one wire, small load.

Back to the action. With just those three things done I'll be ready to manually switch over to making AC power from the batteries and feeding it to all my second floor lights and outlets. The UPS is designed for a large load over a short time. Using it for a small load over a long time will make much better use of the batteries. A few lights and alarm clocks, the odd humidifier or music device, that's it. I'll have to do some load testing to find out how long I can go and that will involve simply spending some time switching and watching.

The next step will be to make it automatic. If the batteries finally get tired in the middle of the night and our alarm clocks all go dead it's going to close down the operation in a hurry. Same goes if The Missus plugs in the hair dryer and draws down the batteries quickly. The solution is automatic switching back to utility power. A simple three-way switch is all it will take for manual change over so to automate things will take a relay.

The UPS already has a battery monitoring circuit. If I'm able to tap in to that, I can use it to signal the relay to trip when the batteries are tired and the solar charger can do it's thing. When the batteries are full, it can automatically switch back. If that's not possible I can build a circuit very cheaply that will do the job. Total cost for this part I estimate to be under $50 including the relay. There are a lot of variables involved here though. How fast will the batteries run down and how fast can they be recharged.

It may be that I can run all night and charge all day and have that load disappear completely from my electric bill. It could also easily be that it will take a week of sunny days to keep the bedrooms lit for a single evening. If that's the case then more batteries and larger chargers will be in order. If that's the case then the challenge will be to look for other crafty ways to recharge.

A small wind turbine would work day and night, but they're even more expensive per watt than solar chargers. I'll likely be looking into DIY versions though. Water flow meters generate a small current from water passing through pipes. One of those just after the water meter would make a small amount of current every time we ran a faucet or a load of wash. Again though, it's a case of wanting to be a frugal homeowner and not a hobbyist playing with expensive gadgets.

This has gotten pretty wordy but it was mostly to help me map out the project. Once I start to actually get this stuff installed I'll be posting more articles, hopefully more concise, as I iron out the kinks and hopefully pinch some pennies.

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1 comment:

  1. Oh my! I want one for the camp! I would totaly do this!


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