Are you off the Grid?

hayden · Feb 8, 2003

Clint, I've got a second home that's off the grid. It's solar powered with a backup generator, and I plan to add a small hyro plant in the next few years.

Regarding the economics, your comparison is unfortunately apples to oranges. As I go through this, keep in mind that I'm a fan of solar/hydro and locally generated power.

A solar setup that can produce the same power that you use today (and pay $100+ per month) will cost way more than $30k. A $30k solar setup would have to be coupled with significant power consumption reductions in your home. Of course if you make those same reductions, your $100 power bill will drop too. It unfortunately turns out that the per KWH cost of commercial power is still below that of solar (figuring the solar cost of a 30 year period).

Turns out there's another fly in the ointment. Batteries. They have a limited life, and are expensive. Just the cost of the batteries assuming a 10 year life gets you close to many grid power rates.

Where I've found independent power to make clear economic sense is where a house is a distance from commercial power and the up front cost of running power lines is the same or greater than the cost of installing solar or some other independent power generation. This was my case and the economics are unquestionable.

I can see all this changing over time. Grid power is costing more and more, and solar is dropping in cost. They keep getting closer and closer, and as the solar control technology continues to improve, it makes solar as seamless to use as grid power.

I've found that just going through the exercise of figuring out where all your power is going will make you a more efficient consumer. You can save energy and money starting today, and start the process of readying your home for solar.

Enjoy it, it's lots of fun.

hayden · Feb 8, 2003

There's another way to do this as well. It's called a ram pump or something like that. I don't know all the details, but essentially you take a portion of the energy from flowing water, and use it to pump a fraction of the water. The pumped water can be used as presurized domestic water, or can be converted to electricity. The waterwheel principal is the same, but with a different mechanism.

This approach basically let's you convert water flow into water pressure. Water has energy based on it's mass (how much water), and the distance it's dropping. Lot's of water with a small drop still contains lots of energy, but low water pressure. Domestic water use requires 15+ psi of pressure. Harnessing some of the low pressure water energy can be used to pump some of the water up to a higher pressure. There are a number of mechanisms to accomplish this conversion. You described a water wheel powering a pump. There's also this funky thing called a water ram pump.

rationalizer · Feb 8, 2003

One more thing to think about is "cost of money". Several notes have compared "one time up front investments" in solar equipment to the "monthly bill" being paid each month for 30 years etc. This isn't a fair comparison - and makes solar look more attractive than it really is.

If you put the $30K (or whatever) in the bank you should earn "some interest" (I know - these days that is wishfull thinking /forums/images/graemlins/frown.gif - but "typical" rates should apply over a 30 year timeframe) So - if you actually had the $30k today and put it in the bank you might be able to pay for your energy costs out of the interest - and still have the $30k or more left at the end of the 30 years...
Mass produced energy is very cheap....

Bill

TWINKLE_TOES · Feb 8, 2003

I plan to add a small hyro plant 
Nigel Smith wrote a book "Motors as Generators fo Micro Hydro Power". (on Amazon) He has done a great deal of work in developing Hydro power in third world countries where the economics and maintenance are big factors. He explains how to use three phase motors as generators driving Pelton wheels.

StoneHeartFarm · Feb 8, 2003

( I met this guy who was going to pump water with his well to run a hydro generator. I asked him where the electrity was going to come from to run the well pump?----this dude clearly failed grade school science. J )

Sounds like the same guy I talked to. He wanted to put an electric motor on a windmill. When the wind was blowing, the windmill would make electricity. When the wind wasn't blowing, the motor would turn the windmill, thereby making electricity.

He also wanted to dig a hole into the bank down by the river. He figured he could live there for the summer and not have to pay any rent. Neeedless to say, he was not impressed when I suggested that instead of diggin a hole, he should get a precast septic tank to live in.
/forums/images/graemlins/smile.gif

Steve

hayden · Feb 8, 2003

I'll check it out - thanks

TWINKLE_TOES · Feb 9, 2003

What kind of flow and head do you think you may be able to achieve?

hayden · Feb 9, 2003

I can get 100 feet of head (elevation), maybe more depending on how long I'm willing to make the pipeline. It will be a minimum of around 1200ft and that's a lot of digging.

I also did a very rough measurement of water flow a few winters ago before the droughts and figured I could draw off 30 gal/ min without seriously altering the flow in the stream. According to my books, that should yield a continuous 300 to 350W depending on the type of alternator used. That's gobs and gobs of power for my needs.

My thinking is to run the hydro hard in the winter when there's plenty of water and not much sun, then actually shut it down in the summer since at least the past two years the stream has run so low it wouldn't produce any power. But of course the sun is plentify in the summer so I think the two systems will compliment each other nicely across all seasons.

By the way, I ordered that book yesterday - thanks again for the tip.

TWINKLE_TOES · Feb 9, 2003

Fun project Hayden I'm envious. I have plenty of water head but no depenable flow. Varies from 100's of gallons per minute to zip. This link, which you probably already have, has lots of design information. Micro Hydro
I looked up your configuration and your right on @ 300-350 watts. For 100 feet of head, (no head loss figured) your are at 43 PSI. For 30 GPM you need a 3/8 nozzle which will give you a turbine speed of 2070 RPM. Good luck, post your progress.

Cacinok · Feb 9, 2003

I appreciate all of the posts. I have been doing some more research and here is what I have found.

Hayden, my $30k number that I used in my last example was based upon what previous posters had said they priced out systems at. I did some research and this is a valid number. I found two kits, one solar about 280 square feet worth and one wind (batteries included). When pricing I leaned toward the higher powered set ups and my price came in at $25k.

What seems to be the most important in trying to get off the grid is to reduce your electrical consumption. Many of the "off the grid homes" I read about used between 500 and 900 kWH/ month.

Rationalizer, you could put 30k in the bank an get interest off of it, but by the time you paid taxes the money would not cover my yearly electric bill.

Clint.