Tuesday, 29 July 2014

Paper accepted to Journal of Artificial Intelligence

Last week we got the notification that our paper had been accepted to appear in the Journal of Artificial Intelligence. The paper describes a method for building generalisable appliance models from existing data sets, and also a method which tunes such models for previously unseen households using only aggregate smart meter data. This material also appeared in chapters 4 and 5 of my thesis.

The final reference for the article is:

Oliver Parson, Siddhartha Ghosh, Mark Weal, Alex Rogers. (2014). An Unsupervised Training Method for Non-intrusive Appliance Load Monitoring. In: Artificial Intelligence, 217, 1–19.

and the abstract is:

Non-intrusive appliance load monitoring is the process of disaggregating a household's total electricity consumption into its contributing appliances. In this paper we propose an unsupervised training method for non-intrusive monitoring which, unlike existing supervised approaches, does not require training data to be collected by sub-metering individual appliances, nor does it require appliances to be manually labelled for the households in which disaggregation is performed. Instead, we propose an approach which combines a one-off supervised learning process over existing labelled appliance data sets, with an unsupervised learning method over unlabelled household aggregate data. First, we propose an approach which uses the Tracebase data set to build probabilistic appliance models which generalise to previously unseen households, which we empirically evaluate through cross validation. Second, we use the Reference Energy Disaggregation Data set to evaluate the accuracy with which these general models can be tuned to the appliances within a specific household using only aggregate data. Our empirical evaluation demonstrates that general appliance models can be constructed using data from only a small number of appliances (typically 3-6 appliances), and furthermore that 28-99% of the remaining behaviour which is specific to a single household can be learned using only aggregate data from existing smart meters.



Friday, 25 July 2014

PhD Graduation

This week I finally graduated from my PhD, nearly four years after I started my work on energy disaggregation (and this blog) back in October 2010. It was cool to finally get closure on the whole process, and celebrate our achievements along with four other PhD students from our lab. Fortunately, I'm still working in the field of non-intrusive load monitoring, so this blog will remain active for at least the next six months. In case you missed it, here's a link to my thesis, which I already feel like was finished a long time ago!

Monday, 14 July 2014

Workshop on Human Centric Energy Management

Last week I attended a workshop on human-centric energy management organised by Dominik Egarter, Wilfried Elmenreich and Martin Krch in Klagenfurt, Austria. The schedule featured a series of keynote talks, discussions, and a trip to Kraftwerk Forstsee.


I presented some work from my group on disaggregating a home's fridge-freezer energy consumption from smart meter data, and also some work on providing home heating feedback via the Joulo project. My full presentation slides are available via my website.


The workshop also included talks from Wilfried Elmenreich on work from their group aiming to bring the smart grid into people's homes, and also Andreas Reinhardt on the opportunities for novel services based on appliance-level power consumption monitoring.

I really want to thank the organisers for inviting me to attend such a great workshop. I'm particularly excited about the potential for collaborations within NILMTK, and hope it leads to some interesting joint projects.

Wednesday, 25 June 2014

WikiEnergy Data Set Statistics

I recently wrote a post about the WikiEnergy data set released by Pecan Street Inc, and have since written a downloader and converter for the data set as part of NILMTK. In total, the data set contains 71 feed feeds monitored across 239 buildings over the period 1 Jan 2014 - 31 May 2014. However, only a subset of feeds were monitored for each building, and many buildings were not monitored for the full 5 months. This post provides a bit more insight into the content of the data set at the time of writing.

Feeds per building:


The histogram below shows the number of feeds monitored in each of the 239 buildings. It can be seen that the mode of the distribution is around 12 feeds per building, and therefore most of these buildings will be useful for evaluation energy disaggregation approaches.


Duration per building:


The histogram below shows the number of months for which each of the 239 buildings were monitored. It can be seen that vast majority of buildings were monitored for the full 5 months, while the remaining buildings were distributed between 1-4 months. However, this distribution will change dramatically once data for 2012-2013 is released.


Percentage energy sub-metered:


The histogram below shows the percentage of energy sub-metered in 235 of the 239 buildings. The remaining 4 buildings appeared to have energy sub-metered greater than 100%, and were therefore excluded from this plot. This distribution has two distinct peaks; one centred around 70% and another which peaks around 5%. The 63 buildings for which less than 40% of the energy was sub-metered are likely to be of limited use for evaluating energy disaggregation methods.



Buildings per feed:


The table below shows the number of buildings in which each of the 71 feeds were present. A description of each of the feeds is available from the Wiki-Energy Knowledge Base. It can be seen that the presence of feeds in buildings is quite sparse. However, the following feeds are present in the majority of buildings: the household aggregate power (use), air conditioning (air1), washing machine (clotheswasher1), dishwasher (dishwasher1), clothes dryer (drye1), electric heating (furnace1) and refrigerator (refrigerator1).

Feed Buildings
use 239
air1 224
air2 38
air3 5
airwindowunit1 3
aquarium1 1
bathroom1 57
bathroom2 7
bedroom1 65
bedroom2 30
bedroom3 4
bedroom4 0
bedroom5 0
car1 62
clotheswasher1 133
clotheswasher_dryg1 28
diningroom1 20
diningroom2 1
dishwasher1 150
disposal1 85
drye1 141
dryg1 29
freezer1 13
furnace1 184
furnace2 29
garage1 25
garage2 3
gen 116
grid 0
heater1 2
housefan1 2
icemaker1 1
jacuzzi1 13
kitchen1 46
kitchen2 17
kitchenapp1 103
kitchenapp2 73
lights_plugs1 79
lights_plugs2 40
lights_plugs3 16
lights_plugs4 4
lights_plugs5 2
lights_plugs6 0
livingroom1 64
livingroom2 10
microwave1 113
office1 31
outsidelights_plugs1 16
outsidelights_plugs2 3
oven1 89
oven2 3
pool1 4
pool2 0
poollight1 2
poolpump1 17
pump1 3
range1 61
refrigerator1 164
refrigerator2 14
security1 7
shed1 3
sprinkler1 9
unknown1 16
unknown2 6
unknown3 1
unknown4 1
utilityroom1 5
venthood1 19
waterheater1 21
waterheater2 2
winecooler1 4

Monday, 23 June 2014

Hart, G.W., Prototype Nonintrusive Appliance Load Monitor, 1985

Since Hart founded the field of energy disaggregation back in the '80s, most papers since have cited his 1992 summary article published in the Proceedings of the IEEE. However, I've seen many references to other papers but have rarely managed to get my hands on the full text. For this reason, I was particularly excited when the following technical report surfaced recently:

Hart, G.W., Prototype Nonintrusive Appliance Load Monitor, MIT Energy Laboratory Technical Report, and Electric Power Research Institute Technical Report, September 1985

Apparently, Hart had received a few requests for older papers over the years, which so far he'd been unable to locate. However, he recently came across a copy of the above paper in the online catalog of a library in Singapore. Mario Bergés then requested the paper via an inter-library loan, Suman Giri scanned the paper copy and Simon Leigh (Jack Kelly's MSc student) applied some post-processing to provide you with the beautiful copy you see today. Quite a good community effort in my opinion!

Thursday, 12 June 2014

New data sets released by WikiEnergy and University of California, Berkley

I've recently come across two new data sets which have been released in the past month:

WikiEnergy data


Pecan Street Inc have released a large amount of domestic electricity data via the WikiEnergy project. The data set currently contains data from 200 homes, in which both the household aggregate power demand and individual appliance power demands are monitored at 1 minute intervals. The data set currently contains 4 months of data from January-April 2014, although more data is likely to be released soon. The data is freely available to University members of the WikiEnergy community, and full details for database access can be found on the WikiEnergy Knowledge Base after registering.

BERDS - BERkeley EneRgy Disaggregation Data Set


The University of California, Berkley, have released electricity data collected from the Cory Hall on the UC Berkeley campus. The data set contains data collected from 4 categories of sub-metered loads: lighting, HVAC, receptacle (sockets) and other, for which many feeds are available for each load category. The data set contains measurements of active, reactive and apparent power which were collected at 20 second intervals. The data is available for free via Mehdi Maasoumy's website, and a paper briefly describing the data set appeared at the Big Learning workshop at NIPS 2013.

I've updated my blog post of publicly available data sets to include both of these releases.

Sunday, 1 June 2014

Attending NILM 2014

I'm really excited to be travelling to Austin tomorrow to attend NILM 2014. I'm particularly looking forward to meeting other people working in the field, so please come and introduce yourself if you're also attending! I've been involved in two papers which will be presented at the workshop:

  1. A Scalable Non-intrusive Load Monitoring System for Fridge-Freezer Energy Efficiency Estimation. Oliver Parson, Mark Weal, Alex Rogers. This paper summarises the final chapter of my thesis, which covers a large scale application of my work to 117 UK households. I'll be presenting this work in the 'new perspectives' afternoon session of the workshop, and also as a poster in the poster session at the end of the workshop.
  2. NILMTK: An Open Source Toolkit for Non-intrusive Load Monitoring. Nipun Batra, Jack Kelly, Oliver Parson, Haimonti Dutta, William Knottenbelt, Alex Rogers, Amarjeet Singh, Mani Srivastava. This paper summarises the initial release of NILMTK; an open source toolkit for energy disaggregation research. This will be presented by Jack Kelly as a 30 minute demo in the final session of the workshop, and also as a poster in the following poster session.

I'll also be attending the Pecan Street WikiEnergy Data conference on the 4th of June, which also promises a very exciting list of speakers.

See you all in Texas!