Smart Grid Mash Up - Part 1 : The Plan

Mercry Timewise Daily Usage Graph

It's been a few months since I received my 'official' invite to join Mercury Timewise program. A smart meter replaced our old mechanical meter at some point before this.

The smart meter delivers power usage data to the power company automatically and at regular intervals. The resolution is 30 minutes as opposed to 30 days with a manually read mechanical meter.

The benefits for the power company are obvious; detailed data delivered without the need for a meter reader walking the streets and, if users buy in, a flatter power demand, but what are the benefits for me?

Primarily that night and weekend power is a quarter the price of peak power ($0.11 vs $0.42). My previous power plan worked out at about $0.21 per unit so on peak power is much more costly but night power is half price. This means if I shift my power usage away from peak times I stand to save some money. So far the saving are averaging at ~$7.00/month. Not massive but I haven't put much effort in. My only strategy so far has been to turn the hot water off before we start using it in the morning and turning it back on when I go to bed at night.

Manual control of the hot water is fine, as long as I remember to turn it back on. Forgetting this vital step results in several frosty events occurring...

As part of the Timewise program customers are supplied with a monitoring 'bug'. This little device sits on top of our microwave and changes colour according to the current power rate- green being cheapest, red being most expensive. It is updated by the power company via a radio link so that it shows the current rate and when the next rate will begin.


The Mash Up Plan
The bug has some LEDs inside that indicate the current power rate. It shouldn't be too difficult to attached some leads to the LEDs to provide signalling to other circuitry. Once this signalling is available I should be able to supply power to my hot water, heated towel rail and dehumidifier only when power is green and therefore cheapest. The fridge can run any time except when the power is red and most expensive. The peak rate currently occurs twice daily and for, at most, two hours. The fridge can easily cope with being 'off' for this length of time.

The dishwasher and washing machine would be nice additions but that are a little more difficult due to be a little bit smart themselves.

I had originally thought of using timers for these tasks but 7 day, mains voltage timers are not cheap and they have to be configured and maintained. Deriving the switching information from the bug means weekends and week days are taken care of, the timing is always (mostly?) correct and I have an excuse to toy with a few electronics.

Part 2 of this series will cover the rest of the plan and progress to date. There are several other components to introduce including the netduino, featured in previous posts and some remote controlled power sockets bought from Jaycar. This project is shaping up to be a real mash up that any Web 2.0 developer would be proud of.