As can be read in the previous blog posting, I have now some weather data around. Here the header from the CSV file I generate out of the XML file of the software:
Date;Humidity (room);Temp (room);Humidity (out);Temp (out);Pressure (abs);Wind (ave);Wind (gust);Wind (dir);Rain
Currently I programmed the weather station to save the data every 5 minutes. The long-term goal is to decide if a given wind turbine delivers a sane amount of energy (during a complete year) at a given place. As I do not want to wait that long to get some information out of this, the question arises, what I can do with this weather data?
Here an example of the output (ignore the rain and wind values, the sensors are not attached at a place where there is wind or rain, the complete set is horizontally on the floor instead of vertically how they are supposed to be; and do not be shocked about the room values, it is the “server room” in the basement):
2010-09-02 12:55:01;52.0;18.700;30.0;27.000;978.600;0.0;0.0;135.0;4.200
2010-09-02 12:50:01;53.0;18.700;30.0;27.500;978.600;0.0;0.0;135.0;4.200
2010-09-02 12:45:01;53.0;18.600;30.0;27.300;978.500;0.0;0.0;135.0;4.200
2010-09-02 12:40:01;53.0;18.600;30.0;27.800;978.600;0.0;0.0;135.0;4.200
2010-09-02 12:35:01;53.0;18.600;30.0;27.700;978.500;0.0;0.0;135.0;4.200
2010-09-02 12:30:01;54.0;18.500;31.0;27.500;978.700;0.0;0.0;135.0;4.200
Some things I came up with myself:
- A line-graph of the values during a day/week/month.
- A graph of the amount of accumulated rain per hour/day/week/month/year.
- The average temperature/humidity (as an error bar, so see the min/max too) per day and night, but what to use as the times where the day starts/ends? I would like to have the day-part cover the real daylight time (minus some ramp-up and ramp-down time), but I do not have any idea how to get this for each day and for my region.Does it make sense to do the same per hour (without any ramp-up/-down)?
- Does the combination of temperature and humidity and maybe wind tell something? If yes, how to combine them and how to interpret the result?
- Similar for the pressure. I do not know what it tells me, but in a graph I can maybe add some horizontal lines which tell something (rain probability and maybe danger zones?).
- For the wind speed the instruction manual comes with a nice table of the beaufort scale and a corresponding description. This can be put into some colored horizontal lines which show more or less dangerous speeds.
For the plotting of the data, I intend to use gnuplot with the CSV data as the input. It should allow me to automate a lot of things, and some of the graphs should also be easy to realize inside gnuplot itself without any external processing, the question is only how to realize it. For example for the average of some values I do not know if it makes sense to use something else than the arithmetic mean.
Knowing the wind speed you can use this to predict your power output for a real turbine. Different turbines are optimised for different locations – the cut in speeds and maxing out speeds varies. Every wind turbine should have a power/wind speed curve. For example there are some here:
http://westwindturbines.co.uk/products/10kwwindturbine.asp. You can feed in the curve data and integrate hourly for a good estimate. However, gustiness will affect it too and I don’t know much about that. Also, obviously you need to have measured the wind speed where the turbine is going to be. Wind speed increases with height above the ground, usually.
That is the reason why I bought the weather station. After a year of collecting data, I want to get the data sheets of interesting turbines and calculate the power output.
Another thing you can do – you can work out your degree days and correlate that with your home heating consumption to see how well your house is performing insulation-wise. Degree days is the sum of (days * degrees C heating need) over time. It allows you to meaningfully compare your energy use from one week to the next when it isn’t the same temperature outside. There is a good explanation of it here
http://www.energylens.com/articles/degree-days