In another installation we have done, we had used an Oregon Scientific weather station to allow the attendant to see the windspeed hitting his turbine.  At that point we had observed how these stations were made, and that the rain bucket used pulses from a reed switch to send data to the indoor display unit.  We had also observed that most of these weather stations are computer connectable.  At some point we had come up with the idea, from these facts, that we could input other data into such a pulse connection, and that a computer could convert those numbers in any way we like.

An opportunity came to install a public display unit for a 10 kW Bergey grid tie wind turbine.  We decided it would be a good time to give this theory a try.  This unit will be in a Texas Public Rest Stop near Guadalupe Pass in West Texas.

Essentially what we wanted was to latch on to the Vantage Pro signal, much like a parasite, and utilize that rain input for our kWh production.  In this scenario, it worked out especially well, since we wanted to display weather information anyway.

For general weather station information, please use Google and search for personal weather stations. There are over ten manufacturers with different features available. Some are wired and some are wireless.

What we had was a rain gauge input that accepted contact pulses at a rate that the unit thought was acceptable for rainfall. We did not know the limits of the unit in this respect. This information was not available in the basic public information, so we emailed a representative of Davis. He kindly sent me documentation detailing the input/output data of the Vantage Pro. This information gave us insight into the limits of the unit, but still did not answer some basic questions we had such as:

• How many pulses (rain) is allowed per month on the display?
• What is the conversion factor of pulses to rain?

By experimenting we found that 66 pulses manually applied always produced 0.62 inches of rain. So from this we calculated that 108.64 pulses=1 inch of rain. We also found that 104 inches of rain was the max allowed. That translates to 11,298 pulses. This number is essential to our project because our kWh display relies on the conversion from this rain number. If it reaches the maximum rain, it reaches the max kWh we can record.

We needed to decide how we would obtain a kWh reading, then how to put that reading into a form that the Davis unit could understand. Our initial idea was to take an old kWh rotary meter, and adapt it to output a pulse. We were thinking along the lines of using an ir diode and receiver. They would be arranged in such a way that the spinning disk would block the light until it hit a hole in the disk which would let the light through. This would give us a pulse to convert into a relay contact, which in turn would output to the rain gauge input of the DVP. Since one rotation of the disk should always be one kWh, it would not be hard to calculate the conversion. In theory I believe this would work, but there are many things to consider.

• We would be altering a good kWh meter.
• Calibration may be effected.
• Our mechanical alterations would have to be very precise and unmovable.
• Light and other interference may give unwanted results.

After some consideration we came up with another plan. We could build a circuit to use a current transformer to output pulses in direct relation to the current flow. We could connect a variable voltage current transformer connected to a voltage-to-frequency converter. This frequency could then be converted to a connection pulse, as the rain input needed. The advantages of this design were primarily that we eliminated the physical aspects and everything would be solid state. A good idea, but it would take someone a good deal of time to design the circuit, build the circuit, and calibrate it.

From the beginning we had hoped to come up with a simple design that a homeowner or turbine installer could do easily themselves. Back to the drawing board.

Why We Chose The Black Box Option

The basic reasons we chose this design are:
Reliable and solid state components.
Simple to assemble and describe to others.
High accuracy can be obtained by customizing the choices in this design.
It allows us to display 24 hrs a day the status of the turbine and the weather.

Vantage Pro Transmitter Unit
	Notice that on our unit (lower photo) we have removed the rain bucket.  It is unnecessary since we are using that input.

Simple 5v voltage regulator for Wattnode signalling.	Multi-Mode timer to output 1 sec relay pulses from square wave.	Wattnode Unit from Continental Control Systems to output square wave pulses from the generated kWh.

Software 

There are numerous software choices on the market for Davis weather stations. We chose Virtual Weather Station by Ambient Software because it seemed to be more flexible in its layout than all the others we sampled. You can click here to see that we were able to seamlessly integrate a kWh reading into the display.

Click here to see a diagram of the entire system.

In essence what we have come up with is a relatively low cost system that will display the following:

• Weather Forecast
• Weather Conditions
• Barometer.
• Temperature inside.
• Temperature outside.
• Wind Speed.
• Wind Direction.
• Historical Datalogging
• 30 days on the Vantage Pro Display.
• Unlimited on the Weather Display software.
• Kilowatt Hours Produced
• Accurate at least to 2 kWh/mo. (determined by choice of Wattnode)
• Kilowatts currently produced.
• Averaged over 5 minutes, ballpark accuracy.
• Historical and real-time graphing.
• Image capture based on movement.

Web Integration

The Virtual Weather Station software that we chose has the ability to post all displayed data to the website of your choice.  So, in essense you can put all of this real-time information at your fingertips anywhere in the world.

Part	Price
Vantage Pro System	$350
Pulse Output Wattnode (Custom Built to 10.11 pulses per kWH)	$300
Multi-Mode Timer Circuit	$19
Web Cam	$20
Ambient Virtual Weather Station Software	$39
Wireless Repeater	$100
Total	$828

Read the Following List

High Voltage Soldering Multimeter Ammeter Frequency Computers Wireless Communications

If any of those words scare or confuse you, or you are unfamiliar with them, please do not attempt these modifications on your own!  This is especially true with the high voltage, It can KILL YOU!

AEI is not responsible for anything you do with this information.  We are only offering a guideline and description to this project that we accomplished. 

Only YOU are responsible for your actions!

Other Notes & Recommendations

It is advisable to plan to have your weather transmitter relatively close to the kWh you are reading.  Remember that the transmitter must physically connect to your load or power producer, just as you would a ammeter.  We have tested a wire length of 100', but I am not sure of the limits.  Shielded wire is recommended, but most any wire should work.

 

To calibrate more exactly, it would be useful to have a kWh meter such as the KILL-A-WATT unit from P3 International to verify.

 

The closer you determine the frequency that will suit you for the Wattnode, the more precise your readout will be.  On a small turbine I believe that the standard Wattnode would work(under 2 kW)

 

This entire design should be applicable to any load or generator, whether it is PV, wind, gas, diesel, etc.  The wattnode will read 110 or 220v and I believe they have models that will read 3 phase.  So, in theory, it can be upsized or downsized to any application.

Initially we did not consider the limits of the software and the Vantage Pro hardware.  We assumed wrongly that we could change the computers interpretation as long as we received the rain numbers in proportion to the kWh.  What we did not consider is that the Vantage Pro ROM is programmed to only count rain up to 104 inches and then it stopped.  So if we input too many pulses, the kWh is very accurate until we reach 104 inches, then we have no reading.  Since we wanted to display a monthly total, this was unacceptable.  Our kWh would only reach around 19, then stop.  We already knew that our turbine in this location was producing over 300 kWh each month. 

There were three ways we could possibly remedy this. 

1. We could write our own custom software to reset the monthly total periodically on the Vantage Pro, while keeping the real numbers totaling on the computer display.  This would take much time and work, and was frustrating because we already had bought the software, etc.  All we needed was less pulses.
2. Build our own circuit reducing the square wave output ten times.  This would take time and resources, and would not be easy to recommend to others. 
3. Order a custom Wattnode:  We decided this is the best choice, and that it is what we would have originally done if we had known beforehand.  We might have spent $300 on parts and labor on either of the above options besides.

We had already ordered the standard Wattnode with 571.429 pulses per kWh.  Although we had not truly installed the standard Wattnode we ordered, they have a no-return policy at Continental Control Systems.  So in essence we lost $300 and had to order another one.  In our case, maybe not such a bad thing, because we will more than likely be able to use that unit elsewhere in the future, but as a homeowner I would not have liked to make that mistake.

In order to avoid this you must make a valid estimate of the amount of power you will be producing.  From this estimate you can take the 11298 pulses allowed, the kWh estimate, and come up with a good number of pulses you would like per kWh.  The highest number you can get away with is best, because it will give you more precision in your kWh display.  For example, if your true kWh measurement was 1.62, you could display 1.5 instead of 1.  More precision is possible with exact measurements and calibration.

NOTE:  We used a 70 A current transformer to send the kWh signal to the Wattnode.  This matches our max amperage passing through the lines we are measuring.  You must match this CT to your specific purposes.  This also effects the amount of pulses output from the Wattnode unit.  Complete details can be found at http://www.wattnode.com. 

Here is an example calculation:

Generator:  100 kWh per month max production

 

11298/100=112.98

 

Wattnode:  Custom with 112 pulses per kWh or lower.

Once you know the number of pulses you need, you can call the guys at CCS and they can build you a custom unit to your specs.

We spent a lot of time trying to develop our own software, and design our own circuitry.  We have staff competent in those areas, and more than likely could have gone that route, in twice as much time!  All of these good products were already out there waiting to be combined.  We only had to look around and figure out how to put the puzzle together.  A mechanic doesn't build a new carburetor for the car he is fixing, he orders one predesigned and prebuilt.  As engineers and technicians, it is easy to get caught in the trap of "what you can do versus what is practical to do".

Once we decided that we could do it all with outside components, it became a much easier project to tackle, and the engineering had, for the most part, been done for us.

Click here to view the photo gallery of Pine Springs System Installation and Pump Side Building.