nimitzbrood (nimitzbrood) wrote,

In the city of winds no one should be buying power...

April 3, 2008 11:15 AM

So on my frozen ride to work this morning (Again, awesome!) I had a fair amount of time to think about power generation at home. We got the first electric bill which is pretty much a 50% usage bill in my opinion. It was $48 for the month of March in which we weren’t all powered up at that time and we still used an average of 16 KW of power. (Probably quite a bit of that is the servers.)

So how can I try and offset that without spending for expensive solar panels or a wind generator that needs a tower, impossible in the city, and a permit.

The answer came to me when I remembered being on the rooftops of Chicago when I was much younger. (Yes mom - we _did_ play on the rooftops like all the other kids in the city. It was actually pretty fun.) Anyway if you search Google for the term “turbine vent” you’ll know what I’m thinking about.

These vents are actually for removing heat and moisture from attics but it occurred to me that with some modifications they can be used as micro-wind generators.

First - they are lightweight and respond to wind from any direction.

Second - they are cheap and can be installed on existing vent pipes.

So here’s what I’m thinking...

1) Take apart an existing turbine vent and install a 1/2“ thick flexible cable exactly in the center of the rotating top. This will likely negate the balancing feature of the vent but we’re looking to place it above the ridge line if possible - depends entirely on the roof in question.

2) Tack-weld/epoxy one half of a thrust bearing to the center of the vent top making sure the cable is threaded through the center and moves freely.

3) Construct a four-way support with a hole in the center and a clamp that will hold the other half of the thrust bearing. Also make sure the cable is threaded through the hole and moves freely.

4) Take three pieces of long and skinny sheet metal (depends on the size of the turbine vent) and make three blades that are the same shape and curve of the existing vent fins and rivet them evenly around the outside of the vent. Length of the blades depends entirely on the roof space, pitch, etc.

5) Assembly the entire thing running the cable into the vent pipe and into the roof.

6) Inside the roof fashion a mount with a collar bearing that tensions the cable but lets it rotate freely. The tension here is what is keeping the vent top held down so it won’t blow away in the wind.

7) Attach a 12” v-belt pulley to the end of the cable. When the vent top rotates it should rotate the 12“ pulley.

8) Mount and tension a small permanent magnet generator with a 1” v-bent pulley on the end so that when the 12“ pulley rotates it turns the generator.

9) Attach the generator to a charge controller and then to some batteries.

I’m not sure what kind of out put this will produce because it depends on many factors but it should produce something and quite honestly most of these parts are cheap except for the charge controller and batteries. I priced the vent at $20 - $40 depending on size, I bought a generator suitable for this for about $30, and charge controllers run anywhere from $35 - several hundreds of dollars. I figure you can probably construct the whole assembly minus batteries for about $200 maximum.

Not a bad investment cost and well within the ability for most people. I think I’ll be buying a turbine vent soon...

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