PhD

HTML5 Canvas versus SVG for interactive charts and graphical models

Some links and notes:

Making graphs for websites and web apps

I've been doing a little research into creating interactive graphs on web pages.  Some quick notes from my research (this isn't meant to be an exhaustive list by any means):

Smart Meter Disaggregation

This blog entry is part of a series of posts introducing the topic of smart meter disaggregation.  In previous posts we've looked at the wider reasons for wanting to reduce energy consumption and we've taken a brief look at smart meters.  In the following blog post, I want to introduce the concept of smart meter disaggregation, also known as "non-intrusive load monitoring" or NILM for short1.  The main aim of smart meter disaggregation is to infer two things from a smart meter signal: 1) which appliances are active in the signal and 2) how much energy has each device consumed.  This blog post will summarise the arguments for disaggregation and we'll look at some of the main challenges.

Why bother to reduce energy consumption

This blog entry is part of a series of posts introducing the topic of smart meter disaggregation.  This specific post looks at the wider reasons for reducing energy consumption.  In other words, this post explains some of the reasons which keep me up at night when I'm not distracted by work! The reasons for reducing energy consumption typically fall into one of two categories: financial and environmental.  We'll focus mostly on the consumption of electricity but the arguments are mostly applicable to the consumption of all sorts of energy.

Financial reasons

There's been a lot of coverage in the press recently about high energy prices.  In January 2012, for example, the Citizens' Advice Bureau stated that 43% of people are worried that they can't afford their next fuel bill.  The following plot shows average annual domestic electricity prices in the UK from 1994 to 2011 (data from DECC, 2011).

Average annual domestic electricity prices in the UK.Average annual domestic electricity prices in the UK.

Electricity prices have risen from 2004 to today; but, when compared to data from the 1990s, today's prices are not quite as earth-shatteringly high as some news papers would have us believe.

What has caused the 35% price rise (in real terms) from 2003 to 2011?  I'm no expert but let's discuss two datasets which shed some light on what's going on.

What is a smart meter?

This blog entry is part of a series of posts introducing the topic of smart meter disaggregation.

Your existing electricity meter probably looks something like this:

Attribution: Kristoferb at en.wikipedia

(image taken by Kristoferb at en.wikipedia)

By 2019, the UK government have mandated every electricity meter in homes and businesses will be replaced by a "smart meter" (that's a grand total of 53 million meters).  A smart meter is simply a digital meter with some basic communications functions.  It will be paid for and installed by the utility company.  It will talk to the utility company over a GPRS data connection; and it will also be able to talk to the "home area network" to provide data to in-house energy displays.

The draft spec for smart meters in the UK was published by the Smart Metering Design Group in August 2011.  The specification states that the meter must be able to supply meter readings to the home area network at a rate of one reading every five seconds.  The meter will measure voltage, real power and reactive power (in both directions).  Some utility companies have already started to install smart meters; British Gas plan to have 2 million smart meters installed by the end of 2012 (Centrica, 2010). 

If you can't wait for a smart meter to be installed then you could buy and install a "home energy monitor". These are available for around £40; although some utility companies give them away for free.  Home energy monitors are user-installable.  I used a Current Cost home energy monitor for my MSc project on disaggregation.  It recorded a sample of apparent power once every six seconds.

This is a reading produced by my Current Cost home energy monitor:

meterPlotmeterPlot

The value of sample at time t is the sum of the power being consumed by every appliance active at time t​.

Free Stanford course on Probabilistic Graphical Models

One of the main research directions for my PhD is likely to be experimenting with bispoke probabilistic graphical models for representing multi-state appliances like washing machines.  As such, I need to learn about existing probabilistic graphical models.  For the past few days I've been reading a textbook called "Probabilistic Graphical Models" by Koller and Friedman.  So far I've really enjoyed the book.

Over lunch today, a friend of mine told me that Stanford are running a free on-line course on Probabilistic Graphical Models, presented by Koller. I've signed up - it looks like a great course; it starts in Feb. Stanford are also running a course on Information Theory, which I've also signed up for.

My copy of David MacKay's "Information Theory, Inference and Learning Algorithms" arrived

My copy of David MacKay's book "Information Theory, Inference and Learning Algorithms" arrived yesterday and I started reading it last night. It looks absolutely fascinating.

I first came across Professor MacKay when I read his other book, "Sustainable Energy Without the Hot Air" and  I was struck by how lucid, readable and entertaining it is. There is every reason to expect that his information theory book will be at least as readable.

Why get a book on "Information Theory, Inference and Learning Algorithms"? The main reason is because it should be very useful for my PhD in smart meter disaggregation. One of the god-fathers of disaggregation, George Hart, wrote the following in Hart 1992:

It is insightful to consider the [disaggregation problem] in the context of a communication model. Appliances can be thought of as “transmitters”, inadvertently broadcasting information as a by-product of their operation. The communication “channel” here is the house wiring. Any of the many signatures... may be the “codes” used in this communication scheme. Our task is to design a “receiver” for these codes which can decode them in terms of appliance state-change “messages”.

In other words, the disaggregation problem can be considered in an information-theoretic framework. This conceptual step allows us to take advantage of the tools developed in communication technology (i.e. coding theory).

Also, for a while now I've thought of information theory as one of those "sexy but mysterious" things which I'd love to learn more about. I read "Decoding Reality: The Universe as Quantum Information" a couple of years ago and found it fascinating (although I only understood about half the content of the book).

So, hopefully MacKay's information theory book will be a great self-study book.

My MSc project on disaggregation is on the Imperial website

During the academic year 2010-2011, I did a computer science MSc at Imperial (which I thoroughly enjoyed). During the last 3 months of the course, each student does an "individual project". Mine was on "Disaggregating Smart Meter Readings using Device Signatures" and the PDF is now available on the Imperial website (note that my birth name is "Daniel" although I've had the nickname "Jack" since I was 11!)

This MSc project formed the basis for my PhD (I'm doing my PhD with the same excellent supervisor with whome I did my MSc project). 4 months into my PhD, I now recognise that my MSc project was pretty naive but it was lots of fun!

E-readers for academic papers & converting LaTeX to EPUB

I currently read academic papers by downloading the PDF and printing; and the tiny collection of LaTeX documents I've authored are output as PDFs. It feels like I should embrace e-readers for academic reading and writing. I have a Kindle Keyboard which does handle PDFs but reading PDFs is not especially pleasant on the Kindle because of its small screen, relatively sluggish refresh rate and clunky note-taking feature.

Reference library available online

I've been using Zotero as my reference manager for my MSc project and my PhD.  It's free.  It's open source.  It's awesome. One of the really nice things about Zotero is that you can easily publish your library.  So that's what I've done. There are references on climate science, smart meter non-intrusive load monitoring (NILM), graphical models and a few other subjects.

 

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