Here at UH, there's a url at which you can just about see how much energy each floor of several for the university dorms is consuming. As part of a federally funded study, the university has outfitted the energy meters and submeters in several of the dorms with power, voltage, and energy consumption sensors, that take readings at the sub-minute level and relay them back to a central server. By visiting a url at hat central server, you can pretty much see what energy consumption looks like for college dorm students.
The university's computer science department has designed and implemented a framework for energy data sharing, uniform access, storage, dissemination, analysis, and visualization, called WattDepot. The API is hosted on the Google Projects site, and once you download it, you can have some command line interactions with the server working in just a few minutes. WattDepot provide a nice API designed to hide the lower layer protocols, that makes interacting with the server much like interacting with a file on your local machine.
First I implemented a class called SourceListing that just listed the sensors associated with a particular WattDepot server, which is known as the "owner" of those sensors. This was pretty simple and pretty much spelled out on the WattDepot documentation examples on the Google project page. THis took me about 15 minutes to write the code and another 15 minutes to set up my Eclipse IDE to associate the framework source and javadocs with the library jar file, for easier editing, code completion, and javadoc perusal.
Then I wrote a SourceLatency class that sorted all the sources at the same url by latency, and this invloved using the code I already had and writing an anonymous inner class to do the comparison of latencies by implementing the Comparable interface. This took me about 20 minutes.
After that, I wrote a SourceHierarchy class that uses the subsources attribute of each source, spelling out which sources are its "children", to construct a set of trees of sources, and then print out those trees recursively using indentation to visualize the hierarchy much like files are shown in a file system browser, or on the command line using the Unix "tree" command. This took me about a half hour, since it involved formulating a game plan to build the trees in the most economic way. What I did was to simply find out what the roots were, by going through all the sources and eliminating all children as root candidates. Then I printed the trees at those roots recursively, so there's never an explicit actual tree data structure in RAM, but I'm able to print out the tree structure nonetheless.
After that, I was energized so to say, and I proceeded to writing a class called EnergyYesterday. Here started the pain. I had to find out how to have Java give me yesterday's date, so as not to hard code it, and I had to find out how to translate between various date formats: XMLGregorianCalendar which WattDepot uses, java.util.Date and java.util.Calendar. Well, let's just say I found some code online that braves this tedious translation, I put in in a class, duly attributing it of course, and doing date calculations should be much easier from here going forward. This class took me maybe an hour and a half to write, much of it having been spent wrestling with dates and date formatting, cleaning up useful date conversion code I found on the web, and making utility classes out of it. THis task would have been garder had it not been for a simple WattDepot API function called getEnergyConsumed that takes two timestamps and provides the total energy consumed between them, so no adding or aggregating was necessary in my part. I just had to loop through all the sources at
After that, I did some energy analysis in a class called HighestRecordedPowerYesterday, which uses an API call by the name of getPowerConsumed, but here I had to loop through each sensor's data points between the starting and ending timestamp and keep track of the maximum power consumed and its related timestamp. This took me about 45 minutes, and I borrowed much of the code from the WattDepot wiki documentation on the Google project site.
Finally, in a class called MondayAverageEnergy, I wrote code to average the energy consumed at each sensor for this past Monday and the one before it. Here I hard codes the dates, and the code is a minor extension of EnergyYesterday. This took me about a half hour.
Now that I accomplished these tasks, I feel like I have a decent grip on the WattDepot client API, and the workflow for getting data from the WattDepot servers, but I have a feeling there's much more to the WattDepot framework, and I'll definitely be wring more about that in the next few weeks.
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