Tuesday, 27 June 2017

At the wheel

This is the blog post I wrote yesterday and then forgot to post!

For the first time in six years Jan got behind the wheel of a vehicle and did some local driving.  It’s like riding a bike….. You never forget!  Well that’s how Jan went.  A slightly nervous start, but it quickly came back to her.  We kept to the quieter residential roads until the navigator (me) forgot where he was and suddenly she was on a busy road with traffic lights.  That was all taken in her stride, although there was some muttering about traffic going to starboard instead of port and why was the steering position so far forward!  Like me; she found the lack of voice street names from the gps slightly disconcerting.  Our  8 year old Garmin Nuvi GPS has audio street names, so why can’t a 2017 system have the same?

Once back home I decided to fit the electrical energy monitoring hub to the house.  There wasn’t much to do.  Electrical mains power was turned off at the meter board before removing the screws holding the panel in place.  Once access to the rear was obtained I clipped the sensor around the main supply cable.  The sensor was then plugged into a battery powered waterproof wireless transmitter which was located outside the meter box.  Then the switchboard was reinstated and the electricity turned back on.

Inside the house I plugged the monitoring system hub into the internet router, before also connecting the hub to the nearest 240V power socket.  The transmitter and hub then automatically wirelessly linked and the hub started sending our electrical consumption over the internet to the website.

After registering on the website I configured the hub data by entering the electrical tariff rate and our initial power consumption target.

The website dashboard then started to record and cost our electrical consumption which you can see in the screen dump below.

Electrical Monitor

The top left box shows our real time usage.  During the initial 90 minutes we consumed 0.12kW of electricity.  The middle box shows our running cost as $0.08 and my budget of $150 for the month.  The top right box has three options:

  • Total cost since implementation
  • Cost for the current month
  • Today’s cost

The graph at the bottom shows usage by minute/hour/day/month,year

You can see a spike in the graph when the fridge was opened to retrieve items for lunch!  All this usage data can be downloaded into a spreadsheet.

There are two reasons we have fitted the monitor.  First, hopefully it will assist us to reduce our electrical consumption and also identify energy hungry appliances.  Second, by recording our daily electrical consumption I should be able to calculate the required size of the planned solar array.  We will need an array that has sufficient capacity to power the house during the day and also provide additional power to charge the lithium battery I’m thinking of building.  The long term idea is to build a battery of sufficient capacity so we can go “off grid”.

Perth has a kWh rate of 26.474 cents and a daily supply charge of 48.60 cents which equates to $177pa just to have the grid connection.  Whilst the electrical company charges consumers 26.474 cents per kWh, they only pay 7 cents per kWh for surplus solar power sent back into the grid from residential solar arrays.   It’s therefore more cost effective to use you solar electricity rather than sell it.  Moreover, if I can build a cheap lithium battery we won’t have to buy electricity when there is no sun.

Lastly, the electrical companies have recognised the threat residential solar power poses to their business and have successfully lobbied the state government to introduce legislation limiting the size of residential solar arrays connected to the grid to a maximum size of 5kW.  Their claim is if too much solar power is fed back into the grid it might overload it or provide a safety risk to employees.  Also, recognising daylight demand is reducing, they have increase the fixed daily supply charge.


Daykin said...

If you are doing a new build then plan to go off grid with a Tesla Powerwall (or two) The power company can go xyzzy.

Tom and Jan said...

Exactly. But rather than buy an expensive Lithium battery I want to make one!

Daykin said...

People are thinking old electric cars will be a cheap option. https://youtu.be/sLZOUlkrDy4?t=763

Tom and Jan said...

It's the most obvious source but the battery would need to be stripped down to find the defective cells which resulted in the car battery having to be replaced.