The two plots above show watt hours generated per day by our solar panels and grid interactive inverter. This first plot shows the daily cycle for today and the last 4 days, while the second plot shows the total daily energy every day since installation. Clicking each plot will show more detail.

The daily plot is restricted to the hours of 6am to 6pm, since input is negligible outside these hours. This is a change from the previous 24 hour display, and is experimental. It is probably adequate for the winter half of the year, but may need to be revised for the summer half. One reason for this change is to investigate more closely the odd 30 minutes in every hour that output appears to fall. I have not been able to find any explanation for this - there is nothing in the manufacturer's manuals, nor their web pages. If anyone can shed any light on why this occurs, I would be pleased to hear from them. My best guess currently (sorry!) is that it is some battery recharge regime.

There is a slight liberty taken with the data in the second plot. This was due to equipment failure over the summer of 2004/5. Data from the previous summer is substituted to maintain the shape of the graph. As the data shows a slight upward trend (more likely due to tree clearing than global warming!), this should not distort the analysis too much. The daily plot is generated by our house computer, and updated automatically every 10 minutes. The long-term plot is generated manually (last update 20080901).

The solar assembly consists of 20x75W panels (1500W total) feeding into a Trace SW3024 E 3300W inverter system, buffered by 4 Sonnenschein 6v 330AH gel cells (7920WH). In sunny weather, the system generates enough power that the meter is usually spinning backwards! Two of the house power circuits (including the refrigerator and all computers) are fed from this inverter, giving about 24 hours of autonomy (at normal current levels) in the event of grid supply failure. (see footnote *)

Our current electricity drawdown from the grid is about 14KWh per day (averaged over the year), and the solar system supplies an average of 4.6KWh (see chart above). That gives an average fraction of about one quarter of our electricity needs being supplied by the sun. That translates a saving of approximately $0.67 a day. The system cost about $6000 ($4000 for the inverter, $2000 for the rebated solar panels, not counting the batteries, which are only for UPS protection), and will therefore pay for itself (assuming no increase in electricity costs, an unrealistic assumption) in about 25 years! But of course, we are also saving about 2.5 tonnes of greenhouse gas a year, (roughly) the equivalent of not driving our car anywhere for the year.

We also have a rainwater system consisting of two 2250 litre Plastanks, fed from the house roof, and pressurised by a 240v Onga Riva-Flo TF30 centrifugal pump. This pump delivers 30 litres/minute at 8 metres head, and is quite adequate for our purposes. Delivery is to two toilet cisterns, and to a garden watering system (8 solenoid operated outlets and 2 standpipes). The garden watering system is driven automatically by cron jobs running on the house computer.

We used to have the water level in the rainwater tanks monitored electronically and displayed here as well; however corrosion problems forced the abandonment of this. There are plans to re-introduce the system, using 1-wire technology. Watch this space!

On the right here is a plot of the inside and outside temperatures of the house. You can see the effect that the heating system has. The data is collected from a Dick Smith wx200 weather station and logged through an RS232 interface. The heating is controlled by a relay driven from the house computer (which also generates these plots). The cycling of the "thermostat" (There is no such animal, it is all soft controlled) can be clearly discerned when the heating is in operation. The actual temperature is controlled by a cron job, which can be overridden through a web interface.

• Our place
• My Digital Photos
• Uniting Church
  • I sing in the choir.
  • I am one of the Glen Waverley church representatives on Presbytery
• Choral Singing: I have been a member of the following groups
  • UNCS (University of New South Wales Choral Society
  • SCUNA (Australian National University Choral Society
  • MONUCS (Monash University Choral Society
• I have done some work on using XML to generate genealogical data for my family. A password-protected directory contains the data (not accessible unless you contact me for the password).
• My cat did a very naughty and expensive thing to my laptop. Read my son's account about how Every Cloud has a Silver Lining
• Australian Rules Football ( Hawthorn Football Club Member)
• Cricket (South Australian Cricket Association Member)
• Why I dislike Microsoft products

• The Railway Photograph Catalogue is a web-based description of my railway photograph database.
• Railways: I am a member of the following societies
  • Australian Railway Historical Society: both
    • ACT Division. Note also the Kingston Mail has some interesting bits of news about the division.
    • Victorian Division
  • Puffing Billy Railway Preservation Society
  • Pichi Richi Railway Preservation Society
• Railway Modelling (HO gauge)

• Meccano: as a boy, I had a 9++ Meccano set, which I think is a fantastic toy for encouraging creativity in an engineering context. David Williams has an equally fantastic Meccano Home Page. While I still have the set (in a pair of wonderful cabinets my father made), I don't play with it much nowadays. Sadly, neither did my sons, who much preferred Lego. Sit transit gloria mundi!

  Postscript: In Marysville, Victoria (Oz), there is an excellent Meccano Museum with many working models. It's called "Maniacal Mechanicals", in Murchison St (the main street). Worth a visit if you are in the area.