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RESIDENTIAL ELECTRICITY
FROM A WIND GENERATOR

Picture how you would use electricity in your home if you weren't worried about cost, despite the fact that your neighbors pay 13.9 cents per kilowatt hour-one of the highest residential electricity rates in the nation. Now picture a luxurious home with no monthly electric bills because a wind generator supplies all the needs of the home, with extra to sell back to the local utility.

We live at an elevation of 6,970 feet (2,124 m) in Sandia Park, New Mexico, ona flat, furrowed two and a half acres that was once a pinto bean field. We liveseven miles (11 km) from a mountain range called the Sandias, which is Spanish for watermelon. At sunset the mountains take on a strange deep green and hotpink glow-one of the reasons our state is called The Land of Enchantment.

There are challenges to living in our high desert area. Temperatures swing50 degrees Fahrenheit (28°C) almost every day of the year, so heatingcosts are important to a household budget. There are also dust devils,lightning strikes, cactus, and tumbleweeds that make the outdoors in hospitable.

We do, however, have some of the best winds in the nation. These arecanyon-effect winds, funneled between the Sandia Mountains and the Manzano mountains, and down through the Tijeras canyon. After observing the weather conditions in our area for about ten years, we were confident that a windg enerator would be profitable.

We Purchase a Used Jacobs
We purchased a used gear-driven Jacobs Wind Energy Systems turbinethrough the want ads in our local electrical co-op's newsletter. The system came with two sets of 23 foot (7 m) spruce blades, an oversized 25 KVA alternator with inductive field winding (no brushes), and a 100 foot (30 m)free-standing Rohn tower. The Jacobs uses an oversized alternator to provide alonger alternator life.

The stub tower consists of a custom eight foot (2.4 m) tower segment which houses the 25 KVA alternator and has the 90 degree hypoid gear drive mounted ontop of it. Altogether, the stub tower weighs about 1,200 pounds (544 kg). Most of that weight is in the hypoid gear drive. The stub tower assembly bolts to the three flange plates on the top of the Rohn tower.

As part of the purchase agreement, we promised not to divulge our cost, but a good price for a system like ours would be US$7,000 to $13,000. The man whosold us this system was getting out of the wind generator business altogether,due to his age. He had professionally sold and installed many systems identical to ours for thousands more than we paid. If all runs smoothly, it should pay for itself in about nine years, with a cost of about a dollar per installed,rated watt.


We made the decision to follow all rules and regulations at every governmentlevel. We even made sure we had the neighborhood's blessing. This paid offgloriously about two years into system operation. We were working in the yardand a van-load of Bernalillo County building inspectors demanded to see our paperwork on the spot. Our ducks were all in a row, so the inspectors droveaway. Since our permit was approved, cell phone towers have sprouted like mushrooms (some would say to ads tools) in our area, giving towers a bad name.

Tim Builds the Tower
Tim assembled the tower in the back yard in his free time. Getting everything ready took about seven months, working weekends and evenings. The tower went together like a giant's erector set. It lay there on its side until the day of the tower raising.

We put the Jacobs stub tower on the end of the Rohn tower and then used afront-end loader to prop up the stub-tower end of the assembly on a 55 gallon barrel. With the top of the tower propped up, we were all ready to mount the blades on tower raising day.


Each trench contained 252 feet (77 m) of 5/8 inch (16 mm) rebar, and wood formsto create a 2 by 2 foot (0.6 x 0.6 m) L-shaped structure. After six yards ofconcrete had been poured into the forms of each trench, the triangular formjoining the three legs was filled. The integrity of the triangular pad is insured by remesh (welded wire fabric). The whole foundation has about 20 yardsof concrete.

When we were all finished, the only things visible were three flange plate sprotruding from a triangle-shaped concrete pad. These three flange plates were precisely located to mate with the three flange plates on the bottom of the assembled Rohn tower. This fit was critically important because the entire assembled tower and wind generator were to be lifted by a crane and bolted tothese flange plates after the concrete set.


We bought 1,000 feet (305 m) of #6 (13 mm2) wire, which in theory meant three runs of about 333 feet (100 m), at least on paper. When we actually dug the trench and laid the wire from the tower to our house, Tim pulled the wire, and there was only about six inches (15 cm) to spare! We felt fortunate that itturned out six inches too long, instead of six inches too short.

Jacobs Wind Genny InstallationCosts
Item Cost (US$) % of Total
20 yards concrete 1,157 25.3%
Architectural approval 685 15.0%
Wire 500 10.9%
Front-end loader rental 450 9.8%
About 4 hours of crane rental 400 8.7%
Miscellaneous welding 375 8.2%
Trencher rental 354 7.7%
PUC administration fees 280 6.1%
Machining work 250 5.5%
Building permit for tower 127 2.8%
Total $4,578 100.0%

Tower Raising Day
Tapping the years of experience of the former owner, we decided to use a craneto raise the tower. We followed his recommendation to assemble the tower on the ground, where we could take all the time we needed. In fact, we hired him on tower raising day to insure that everything would go smoothly. This was well worth it, since the most expensive part of the installation was the hours of crane time involved.

First we installed the blades on the governor and adjusted the governing spring tension to properly set the blade feathering rpm. The next step was to lift the wind plant and tower, still parallel to the ground, and bolt on hinges between the footings and tower leg flange plates.The crane then slowly tipped up the entire assembly-blades, turbine, stubtower, tower and all. The whole thing went up perfectly, and rested on thefootings. If the measurements had been even one-sixteenth of an inch (1.6 mm)off, the tower would not have mounted on the bolts. Once the tower was upright,we removed the hinges and bolted all three flange plates together.

Local Payback Rates
Month $ per KWH
January 0.0174
February 0.02586
March 0.01716
April 0.02043
May 0.02022
June 0.01807
July 0.0162
August 0.01725
September 0.03706
October 0.0342
November 0.0326
December 0.02989

Tim then did his first tower climb to disconnect the rigging. As he climbed,rain threatened to fall, and there was lightning in the distance. We had heard a story of a rainstorm resulting in a stuck crane and US$3,000 of rental timebefore a D-8 Caterpillar was used to tow the crane out. But as an old adage says, "He that observeth the wind shall not sow; and he that regardeth theclouds shall not reap." So Tim climbed to the top, unhooked the cranerigging, added oil to the gearbox, and climbed back down. Rotten weather hass lowed us down, but never stopped us!

History & Service
We purchased the system. We were officially hooked up to the grid. Over the past four and a half years, we have only had afew problems. The lower alternator bearing needed to be replaced once. And theelectronics have needed minor adjustments.

Data Summary
Monthly Data
Description Data
Outside meter reading (Start KWH) 95,945
Outside meter reading (End KWH) 95,577
Inside meter reading (Start KWH) 38,460
Inside meter reading (End KWH) 40,500
Plains Energy purchase rate (per KWH) $0.02043
CNMEC rate (per KWH) $0.139
Tax rebate (per KWH) $0.015
 
Analysis
Description Data
Total generated (KWH) 2,040
Total sold to Plains G&T (KWH) 368
Total consumed (KWH) 1,672
Tax rebate$ 5.52
Plains owes us$ 7.52
Utility savings from wind genny$232.41
Personal use of business product$ 34.16
Total Benefit$245.45

The yearly maintenance on our machine consists of greasing the zerk fittings(two on the drive shaft, two on the roller plate that the hypoid gear sits on,and one on each blade), and draining and replacing the 1.5 gallons (5.7 l) ofgear lube in the hypoid gear drive. If we hired someone to do the work, we believe it would cost about US$150 per year, but since Tim does all the maintenance, the only cost is grease, gear lube, and Tim's time.

Noisy?
Most people are surprised at how quiet the wind generator is. It's very quietin winds up to 30 mph (13 m/s). At this speed, the centrifugally actuated governor begins to feather the blades, making them less aerodynamic and muchnoisier. When the winds are above 30 mph, we're not usually outside anyway. Our neighbors to the north have their home about 500 feet (150 m) from our wind generator and say they usually don't even hear it. The neighbor on the other side has told us that when he can't sleep, he likes to go outside to listen tothe soothing hum of the wind generator.

We live in an area of independent people. In our neighborhood, one manrestores Model A Fords. One woman raises exotic birds, and another breedsshar-pei dogs, so we all have an attitude of live and let live. In fact, hotair balloonists and hang gliders have used our wind generator as a landmark to navigate by. They often land in the 80 vacant acres behind our property.

Paperwork & Contracts
It took about nine months to receive the legal permission from the federalgovernment and the Public Utilities Commission to hook our system into the gridto sell back power. This meant a back and forth letter exchange, with usfilling out many forms and exercising the authority given us by New Mexico Public Service Commission Rule 570. We then were given a five year contract with our local utility, Plains Generation and Transmission (Plains G&T). Weare paid a low of 1.620 cents per kilowatt-hour to a high of 3.706 cents perkilowatt-hour for the electricity we generate. We joke that the monthly payback rate seems to be inversely proportional to the winds. If there were not so muchtruth in it, we could laugh more.

We pay a US$10 monthly fee to the Central New Mexico Electric Co-operative(CNMEC). For this fee, they are supposed to read our meter monthly, and report these readings to Plains G&T. Plains G&T is a separate business fromwhich CNMEC purchases all its power. When we buy electricity, we purchase itsecondhand from CNMEC. When we sell it back, our electricity goes to PlainsG&T at wholesale rates. This reporting process of our meter readings is important because it determines the amount we are paid for what we generate.The Co-op is also supposed to report the meter readings in an efficient, timelymanner. Although we pay our $10 monthly, their part of the agreement has never been fulfilled.

For this reason, and also because of the deplorable payback rate, we quicklycame to the conclusion that the best use of our electricity was to use it upentirely. The contract forbids us from selling extra electricity to our neighbors, but many months we produce enough to supply about four households.We still pay the fee because we believe they would disconnect us if we didn't up hold our end of the contract.


Tim designed and installed a radiant heated floor. It heats our entire houseusing wind-generated electricity. It warms up to 90°F (32°C) in abouttwenty-five minutes. And, best of all, it can use up 100 kilowatt-hours perday.

With our heated floor, we only used our woodstove once or twice throughout the entire winter of 1998. We also have a forced air heating system powered with propane, but we do not use it much anymore. This radiant floor design isakin to standing on a beach, where the sand has been warmed by the sun-nice!

The floor is Vermont slate. Under it, cemented to the tile with mastic are quarter inch (6 mm) copper pipes set six inches (15 cm) apart and nestled inwood grooves. The foundation of the floor is a concrete slab. The copper pipesare filled with about 80 gallons (300 l) of a 60/40 water/antifreeze mixture.The fluid circulates in an integrated pattern, so there are no cold spots on the floor. Tim buried a hot tub thermostat in the grout of the floor to act asa temperature sensor.


It is a closed system that circulates through either an electric or a propane water heater. With a switch on the wall, we can choose between heating the floor with electricity or propane. The propane is a backup that we seldom use.

No Need to Conserve
We put up a wind generator because Tim got bit by the wind energy bug. We hopeto be an encouragement to anyone who has a similar ambition. We like the freedom that the wind generator represents. We're not millionaires, but we surefeel like we are. If you visit us, we'll never tell you to turn off the lightsor turn the heat down.

Heated Floor Costs
Item Cost (US$)
100 square feet of Vermont slate $1,000
Copper pipe and fittings $500
Sub-flooring (plywood & 2 x 6 lumber) $500
Propane water heater $200
Electric water heater $150
70 gallons deionized water $70
Water heater safety tank $60
70 gallons antifreeze $45
Hot tub temperature sensor $35
Total $2,560

Written by: Home Power


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