Dear iccb and WeatherCat observers of the sun,
I'm thinking is there way to use synthetic channels to convert daily kWh from measured solar radiation? I have Davis vantage pro 2 and trying to figure the conversion to kWh...
Unfortunately, you'll need to clarify your units in order to accomplish what you want. What Davis is reporting is watts per square meter. That means if you had a panel 1x1 meter, what the sensor is reporting is the number of watts of solar energy are falling upon it. That's raw energy, solar panels aren't 100% efficient. If you had a solar array 1 meter square you would get substantially less electricity.
The unit you are trying to convert to is kilowatts (10
3 watts) • hours. That, believe it or not is a measure of energy - not power. The definition of a watt is 1 joule per second. What you are seeking is 1000 Joules/seconds • 1 hour. To make everything consistent, convert 1 hour into 3600 seconds. How you can resolve the dimensions:
1000 Joules • 3600 seconds/1 second = 3600000 Joules.
Yes, I have a bachelor's degree in Physics which is why I can crunch through all this dimensional analysis as it is called.
Returning to your problem, your goal of getting Kilowatt•hours is actually attempting to determine out much energy (I presume) you could get out of a solar array exposed to the sun for some period of time. As already mentioned, if you already have a solar setup installed, you would need to know how efficient it is. If you are simply considering such a thing, you would need to get the same information from the vendors you are considering.
The next question I must leave for you to answer. Why are you interested in the amount of energy you could collect over some length of time? Is your plan to store this energy in a battery? Otherwise, for most household solar installations the main point of interest is the amount of power and is it sufficient to power things like your central air conditioner.
As long as you are looking into a solar installation where you remain connected to the grid, the issue is cost. The more you can rely on your solar, the less you'll need to pay your utility for electricity. Nonetheless, without some sort of battery, you'll always be paying for power when there is no sunshine. Even without precise quantities, a graph of your solar radiation should open your eyes about what can and cannot be accomplished with solar power.
If you have aspirations to go off the grid, that's a much more difficult nut to crack. In order to do that, you need to deal with cloudy days, smoke from wildfires, and so on. If your batteries run low, then you need to get power from somewhere else or go without electricity.
I'd better stop here, but I hope this sort of issue is more complex and mathematically thorny than most people realize.
Cheers, Edouard
