Beer, Coffee, and a little DSP

The Fluksometer is a Wifi device that measures your household power using a sensor that clips over the mains cable in your fuse box. The Fluksometer then associates with your Wifi network and automatically logs power data to the Flukso web site. Your data can then be viewed via your account on the Flukso web site:

When I see graphs like this I am shamed by my profligate energy use so I go stomping around the house yelling at children and switching off lights!

The Web is pretty cool for connecting people with related interests. I met Bart from the Flukso project through a post to the Village Telco Google Group. Bart was working on similar technology to the Mesh Potato - an Atheros based Wifi router coupled with a micro-controller to help interface analog signals. However instead of telephony, his device logs household power consumption data. Just like the Mesh Potato, the Flukso project is also open hardware. Very cool. I am really interested in minimising my household energy consumption, so I bought one of the Beta Flukso’s as soon as they were available.

For 85 Euros you get a full kit in a very nice box with very simple, easy to read instructions printed on the outside:

Here is the kit of parts inside the box:

The Wifi router is tiny - just 6 by 9 cm. The OpenWRT based GUI is extremely simple to use, just enter a few details of your Wifi network and that’s it. You do need a power point for the Flukso near the fuse box. In Australia many of our fuse boxes are outside so this can be tricky. As a start I extended the DC cable a few meters into the nearest room of the house. I’ll get a power point installed inside the fuse box soon.

Hacking my Fuse Box

Don’t try this at home. Get an electrician instead.

I have a grid connect Solar PV system which complicated my installation a little, as my house exports electricity during the day. The Flukso sensor can’t sense direction so initially I could see my day-time electricity “use” going up as the sun rose overhead and PV system exported electricity.

What I really want to know is how much power the house is consuming. This is actually obscured by the PV system. For example if the PV system is generating 1000W, and the house is using 1200W, I will be importing 200W from the grid. My house electricity meter and the Flusko will read 200W as they are measuring net power. I would get the same reading if the house was using 200W at night with no solar power being generated. In both cases all I get is a net reading from my power meter of 200W. So the problem is to separate out Solar PV power from the household power consumption by clamping the Flukso sensor over the right wire in the fuse box.

In my case some editing of the fuse box wiring was in order. After discussing the problem with Bart and Dickson (an electrician friend and fellow EVer) I worked out what I needed to do. So one Sunday morning while the house was quiet I armed myself with a pair of rubber gloves and a screwdriver. After shutting down the power via the main breaker, and the solar power via the solar breaker, I took a cautious peek inside my fuse box:

The solar breaker is on the far right. It feeds current into my power system via the long red wire that leads to the main breaker on the far left. Here is a close up of the main breaker:

The mains from the grid enters at the bottom, the top are the various connections to my house. One of these wires is the solar power, the other two lead off to various household circuits via other breakers. The top of the main breaker was being used as a junction, making it tricky to separate solar from household power.

What I wanted for the Flukso sensor was a single wire that had all of the household power flowing through it. This wire should be separate from current flowing from the solar system. So I went to work with the screwdriver and moved the junction points to some of the other breakers. This left me with just two wires connected to the house side of the main breaker, the solar and “everything else”

Note the Flukso current sensor clipped over the “everything else” wire. Dickson said to make sure that the extra wires weren’t wired to the main breaker for a reason (for example high current load). However these circuits lead to minor loads so I figured I was OK. With the minor rewiring job I ended up shortening the entire path anyway.

Next steps

For the record I currently use about 22 kWh a day (large house with a pool, 5 people, 4 TVs including one flat screen, 4 computers in daily use). I work from home so the house is in use during the day.

An average of 6kWh is for the EV - this I have no problem with as my Solar PV generates an average of 8kWh/day so it’s fossil-fuel free driving. Even when we charge at night it’s electricity made right here in South Australia (approaching 20% wind power in South Australia, with much of the balance natural gas power stations) rather than running my car on nasty, rapidly depleting foreign oil (Australia is way past peak oil production, we import 70% of our oil).

But the 16kWh balance annoys me. I am in the process of tracking that down by performing another power audit, this time with a more accurate power meter that can handle inductive loads. I am sure it’s the kids, but another audit will no doubt point to my office like last time. My goal is 10 kWh/day, excluding the EV.

Bart also suggests this approach: “When the kids are asleep, pull out all electrical appliances, especially heavy users like your fridge. Then look at the reading on the ‘hour’ chart. Switch off the fuses one by one (except the one the Fluksometer is drawing its power from!), while looking at the hour chart in between those switch-offs. You’ll have to wait a couple of minutes to see the result. When you notice a big drop in consumption, you’ll at least know which circuit the phantom load is on.”

Managing Household Energy Consumption

A similar product already available here in Australia is the Centameter. This has a sensor that talks to a wireless display via a short range wireless link (not Wifi). The big difference with the Fluksometer is that it is built around Web technology. This means you can access the data anywhere (for example while out of town or at work), and do lots of clever things like examine your homes historical power usage over time and seasons and compare with other peoples usage patterns. Here is an example of my power consumption compared to Barts:

Bart puts me to shame!

One other difference is that the Centameter sensor doesn’t require AC power near the fuse box (although it does need batteries) or a Wifi Internet connection. The Fluskometer (85 Euros) costs roughly the same as a Centameter (about AUD$200).

BTW these devices usually pay for themselves very quickly. To recover the $200 in 1 year at my current electricity rate (18 cents/kWh) works out to 3kWh/day, or just a 125W load running 24 hours/day. However for me it’s more than the $ - it’s about needless waste and the folly of burning irreplaceable fossil fuels.

Both devices share a very important principle - if you can measure your power you can manage it. Reducing power consumption (Negawatts) is by far the most powerful alternative energy technology we have today. A good example is our household. We have dropped our electricity consumption by 50% and are now shooting for 70% and we use maybe 10% of the petrol we used a few years ago.

Buying a Flukso

If you live in Australia and New Zealand you can buy a Fluskometer from the Free Telephony Project Store. If you live in another country please contact the Flusko Project for other purchasing options.

Links

[1] Flukso Web Site
[2] Technical details of Fluksometer including open hardware design
[3] EV Battery tester - another use for a Wifi router connected to a micro-controller.
[4] Halving my Gas and Electricity Bills

This entry was posted on Friday, October 2nd, 2009 at 9:30 am and is filed under Uncategorized. You can follow any responses to this entry through the RSS 2.0 feed. You can skip to the end and leave a response. Pinging is currently not allowed.