Sunday, 10 March 2013

Differences between disaggregation in the UK and US

I was asked recently what I thought the differences were between disaggregation in UK households in comparison to those in the US. My first reaction was that a UK household is just a simplification of a US household, but I've been thinking it over since and come up with quite a few key differences. This is my attempt to categorise them:

Load diversity

There are quite a few differences in the loads that can be found in American households compared to their British counterparts. The most significant of which is the presence of heating, ventilation and air-conditioning (HVAC) systems in American households. In comparison, UK households are far more likely to be heated by gas, and not require air-conditioning at all. Since the HVAC system often constitutes the largest electrical load in American households, the problem of disaggregating the remaining appliances is clearly simpler for UK households. Furthermore, in my experience, American households contain not only a wider range of loads (pool pumps, etc.) but also contain more duplicate appliances (2 or 3 fridge/freezers, etc.). This again contributes to a harder disaggregation problem for US households.

Split-phase power

American and British households also vary in the way that electricity is supplied to the properties. UK households typically receive single-phase (1 electricity input wire) power at 230 volts, while US households receive split-phase (2 electricity input wires) power at 120 volts. The case of split-phase power provides a convenient opportunity to install two current clamps instead of one. Through this small additional installation cost, the complexity of the disaggregation is more than halved, since most appliances are connected to only one of the input cables.

Smart meters

To the best of my knowledge, the capabilities of smart meters in both countries are yet to be finalised. However, the UK provides an interesting extension to the government mandated smart meter rollout, in which households will also receive an in-home display (IHD). IHDs will primarily provide a household's occupants with real-time information, such as their current power demand and cost of electricity. However, since these devices are likely to have access to electricity data at a higher granularity than is transmitted to the energy provider, they provide a convenient platform on which disaggregation can be performed. Furthermore, performing on higher granularity data within each household even circumvents any privacy concerns related to transmitting private data outside of the home. However, IHDs will clearly have limited resources in terms of processing power etc., which raises the interesting field of resource constrained energy disaggregation.

1 comment:

  1. Great points! There definitely are significant differences between US and UK consumption profiles. This is one of the main reasons why I wanted to record my own dataset from UK households. For example, IIRC, the washing machine power signatures in the REDD data look nothing like the washing machine signatures that I've been recording from UK households. I don't know why!

    On the topic of heating (and that US homes use resistive heating whilst UK homes tend to use natural gas): I wonder if the situation will start to change now that natural gas is considerably cheaper in the US than in the UK due to the considerable growth of shale gas in the US.