WindPV System

John Millard

I have been a renewable energy buff since the 1974 energy crisis. Windmachines for generating electrical power always fascinated me. In 1974, I bought a 200 Watt 12 Volt windcharger and installed it on a 35 foot steel tower. It generated a small amount of power for the house. At the time, I had 5 @ 24V aircraft 35 Ampere-hour batteries (wired in series to produce a pack of »130 VDC). The batteries fed a 1kW. rotary converter, 130 VDC in and 120 vac out, which ran the house. The 12V output of the wind charger fed a 12V to 120V, 150 watt Tripplite inverter which in turn fed a rectifier driven by a small auto transformer to boost the voltage up high enough to charge the 130V battery.

Getting Started

The system sounds good, but was very inadequate. It was fine for first few hours, but the energy input to the batteries was extremely low. The windcharger mainly kept wind recording records over the years. I used an old G.E. chart recorder to record the 12V output whenever the wind blew. The tower was too short, the trees are higher than the tower in some directions. But we learn from our mistakes. System Location

This wind plant attempted to power our summer home in Round Top, upstate New York. We are on three acres of land in the the Catskill Mountains, at 860 feet elevation. Our property is in a resort area with a lot of boarding houses dating back to the 1850's. It's a nice mountain resort with cool summer nights. Wind Machine & Tower

In 1975, with my father's encouragement, I purchased an Electro Windplant made in Winthur, Switzerland from Real Gas & Electric in California for $3,500. It sat in its crate for 3 years until I completed the 80 foot tower.

The tower is built from eight 9 foot sections of 3"x3"x1/4" angle iron and 2" angle iron. This angle iron came from what was once an 8 foot wall around the roof of "The Valencia", a movie theater in Jamacia, Long Island. After pricing new angle iron, the 45 year old iron and bolts looked very attractive. The district manager was glad to find someone who would dismantle that section for free. With the help of my cousins, Jim Sweeney and Bob, the roof was dismantled and all the angle iron, complete with nuts and bolts, was hauled to upstate New York.

It took three years to build the tower following carefully drawn plans. The whole tower was built on the ground. It was raised with the windplant on it from horizontal to vertical using a hand cranked, 5 ton winch. It took three people two days to raise the tower to the vertical (thanks Frank, Mike and Dan Gilroy). When the tower was finally vertical and the reinforcement bars were in the three holes, the concrete was poured. I used existing large trees, guyed temporarily, to lift the tower. The winch was mounted to the trunk of one large tree. I left the guy cables from the tower to the trees in place for extra security, but after ten years and tremendous winds over the winter, I figured that the tower could support itself as was originally planned. The tower is also anchored in solid rock below the concrete using two rock anchors per hole. The tower was completed in 1978.

In my area the wind usually comes from the northwest or the southwest. The wind machine is producing 6 to 12 kilowatt hours in

24 hours depending on conditions. When the wind is gusty (NW wind) the wind machine is constantly yawing to catch the wind and in the process loses a lot of power. The gentler and more constant wind from the southwest generally produces more power.


The battery house, next to the tower, is the size of a one car garage. It was completed in 1980. I built shelves on both sides of the building out of 2x4's and 2x6's. I have two battery banks with 60 cells in each bank. The 2 Volt, lead calcium cells weigh approximately 110 pounds each and are rated at 50 Amps for 8 hours, some are 62.5 Amps for 8 hours. The two battery banks supply about 1200 Amp hours at the 100 hour rate or »140 KWH of storage. This supplies 2 weeks of storage using 10 KWH/day.

Photovoltaics & Tracker

In the summer the windplant just sits like a monument, doing nothing, so I decided to try solar. I bought 33 panels @ $200 each from Solarex. They are factory seconds with blemishes, no frames, and no guarantee. All of the panels tested between 2.5 to 2.8 Amps in strong sunlight. Some of the cells were missing their beautiful crystal blue color, but they still produced full current. I built a wooden frame of 2x4's and household wood molding to frame the 33 panels. The whole frame pivots on a center beam that tilts up. The high end of the frame faces north, the lower end faces south. The frame tilts, like a seesaw, east and west to track the sun. I can also tilt the main beam up (north side) higher using a small hand crank winch and pulley system at the rear of the panels. I adjust the tracker's tilt monthly so the sun hits the panels more directly at 12 Noon. The panels track east to west using a small electric winch and electronic timer which almost precisely keeps the panels in direct sun all day.

The electronic timer operates a relay which closes the circuit to the 1/6hp ac winch motor every 15 minutes for eight seconds. It uses a 555 IC from Radio Shack. It has two adjustments, one for off time and one for on time. Once the two potentiometers are set, it will work reliably for the whole season. In the evening, the panels stop tracking when a mercury switch opens the circuit to the winch motor, just before the panels hit the stops. I then throw a reverse switch to tilt the panels back to the east. The reverse process takes about 3 minutes. The sun hits the panels at about 7 AM. I have calculated that the tracker increases the panels output by 30% in the summer.

In 1986 I added 11 more Solarex seconds to the frame increasing output 25%. The original frame had three "holes", I then added 4 panels to each side of the frame. That gave me 44 panels or 4 sets

John Millard and helper mount the PV panels on the homemade wooden tracker.

John Millard's Mom & Dad standing before the loaded tracker. 44 Solarex PV panels wired to make 10.5 Amperes at130 Volts DC.

A view of John Millard's house and 6kW. Electro Windmachine with 16.4 foot diameter propeller.

of 11 panels in series. Each 11 panels in series produces 130V at 2.5 Amps. The four sets of 11 panels are each connected in parallel to produce 10 Amps at 130V in good summer sun.


I had been using a Silicon Control Rectifier (SCR) inverter, but last year I set out to design and build an inverter with improved power handling capability and efficiency. I built a 4.5KW inverter that uses 20 mA. at 130V with no load. It is 97% efficient at 20% load and 94% efficient at full load, which doesn't happen very often. It is a HexFet™ power inverter that's transformerless. I feed the inverter with 130VDC and get squarewave 130vac directly to the load, it's efficient and durable.

Last summer I caused a short circuit on its output, not once but twice. I was cleaning a 32 watt circular kitchen fluorescent light fixture with steel wool. I had removed the fluorescent tube and accidentally touched the socket with the steel wool. I had fireworks with burning steel wool raining on the floor. Good thing I was on a wooden chair. I was careful, but the same thing happened while I was cleaning a second fixture. The inverter didn't fail. The old SCR inverter would have. The inverter and PVs have also survived several thunderstorms with hail as large as 3/4" in diameter. Knock on wood.

Last year I replaced our frost free refrigerator with a manual defrost model, reducing power consumption from 4KWH to 1.8KWH daily. That's a power savings of over 12KWH per week. I have rechanneled the saved energy into a two burner electric stove to supplement our gas range. For two weeks this summer we used the electric stove for all our cooking with no noticeable reduction in battery voltage, besides running everything else in the house (4 electric fans, water pumps, washing machine, toaster, electric tractor, a GE electric riding lawn mower and tractor which uses 6 golfcart batteries) During the summer, when there's company, we need up to 5KWH just to pump water. The rest of the time the pump uses 0.8KWH. PV Voltage Booster

I made a device this past summer called a maximizer which boosts the voltage output of the solar panels about 15%. It makes use of the solar panels ability to produce higher voltage when they are cool.

Normally the battery voltage is 130V, but with the maximizer I can get 170V from the panels when the temperature is 50°F at practically the same current and drop it down to 130V through a transformer. Of course, you have to change the DC from the panels to ac before you feed the transformer. That extra 40 Volts at 10 Amps is a 400 Watt gain. This extra energy is rectified with a bridge rectifier on the output windings of the step down transformer which changes it back to DC to feed the batteries. It is also an isolation transformer. I have seen an extra couple of Amps going into the batteries.

A second inverter is used to change the DC to ac. I used an isolation transformer and adjustable variac so that I can change the turns ratio to match the best possible voltage the panels put out. It is like tuning in a radio station for the best signal level. I just vary the variac for the highest Amperage reading into the batteries. Then I back off a little to the low Amperage side because I know the panels are warming up if its in the morning. The ratio of the transformer windings is less as the panels heat up. If you go above the high side of the ammeter reading (more turns ratio on the variac) you will soon end up with less output even without the maximizer because the transformer match becomes very poor. At present, I have to go to the battery house twice a day to reset the variac for maximum match between the PVs and batteries. It would be nice to have an automatic device to keep the match at maximum at all temperatures throughout the day. Alternative Energy Engineering carries Maximizers, but not at the voltages I'm interested in.

System Instrumentation

I have a large plus and minus Amp meter similar to a car ammeter in the battery house. It has 0 center reading from +70 to -70 Amps. I've seen that meter go over 20 Amps when I have a clear sunny day with a brisk NW wind. That's 10 Amps from the windplant and 10 Amps from the panels. One day last summer the batteries collected 16KWH from the sun and the wind.

The windplant and the PVs can each produce a maximum of about 13KWH in a 24 hour period.

I use two electronic Ampere-hour meters from Natural Power in my system, one measures DC Ampere-hour input to battery and the other the Ampere-hour consumption of the inverter. These Ampere-hour meters tally energy gained or lost per day. A good day in the summer will show approximately 100 Amp-hours input to the battery at 130V. This time of year (Nov. 15, 1988) the solar panels produce about 50 Amp-hours on a good day. The wind plant will produce more energy as we approach the windy season and its output will approach 100 Amp-hours.

I have a small recorder hooked up to an anemometer which measures wind speed calibrated to 50 MPH top scale and 1/8 inch per hour tape speed. One roll of recording paper will last six months. I set this recorder every fall and have winter winter recordings for the past 5 years. The anemometer head is mounted near the wind plant in the tower. The winter wind recordings are very impressive. The wind blows for two weeks straight at times with hardly a break. In fact, the wind blows more days than it doesn't in the winter.

The anemometer is powered by normal utility power over the winter which is at the house and used as backup when my system is off. My system is really not a necessity as I know it is for many other people out there. But since it is already in the house why disconnect it? It's good security if all else fails. Besides it's only $6.00 per month to have the utility there.

I want to thank my mother and father and all people mentioned for their support.

John MIllard, 46-27 157st St, Flushing, NY 11355 Windplant Specifications

Model WV650, 6KW peak output at 130VDC, 16 pole alternator, Double Lundel field rotor.

Electro magnetic field shunt fed from a three phase rectifier in head, main three phase output is rectified at base of tower in control box.

Propeller is a three blade spruce wood, 16.4 feet in diameter which automatically feathers in high wind. Maximum prop rpm is 200 stepped to 800 rpm at alternator with 4 to 1 gear box in front of alternator.

The tower is 80 feet tall.

I built an electronic rpm monitor which automatically causes the tail to furl thus shutting down the plant if for any reason it overspeeds. A small winch which operates off a 24 volt tap on the main battery pulls on a 5/16 steel cable which goes up the center of the tower through the turntable at the top and is attached to the tail via a chain.

The windplant is made by Electro GMBC of Winterthur, Switzerland.

Daily Power Production (PV & Wind) during July/August 1988

0 10 CP













7/3 7/4 7/5 7/6 7/7 7/8 7/9 7/10 7/11 7/12 7/13 7/14 7/15 7/16 7/23 7/24 7/25 7/26 7/27 7/28 7/29 7/30 7/31 8/1 8/2 8/3 8/4

Dates during July and August 1988

Renewable Energy 101

Renewable Energy 101

Renewable energy is energy that is generated from sunlight, rain, tides, geothermal heat and wind. These sources are naturally and constantly replenished, which is why they are deemed as renewable. The usage of renewable energy sources is very important when considering the sustainability of the existing energy usage of the world. While there is currently an abundance of non-renewable energy sources, such as nuclear fuels, these energy sources are depleting. In addition to being a non-renewable supply, the non-renewable energy sources release emissions into the air, which has an adverse effect on the environment.

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