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.
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.
- 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.
- 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.
- 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.