Category Archives: renewables

DIY Offgrid Project – PV panels

I found 13 x 250 watt PV panels on Gumtree for $100 each. It turned out they came with mounting rails and most of the clamps. That’s about $500 of cost avoided! The panels all appear in perfect condition. That’s 3,250 watts of panels for 40 cents per watt. By the time I get them on the roof they will owe me nearly 60 cents per watt. That’s about 4 cents per kWh over ten years. Cheap power!


The open circuit voltage of the panel, Voc is 37.6 so three in series is 113 volts which is less than 120.

There is an interesting loophole in the electrical safety rules. You don’t need to be a licensed electrician to install DC equipment that operates below 120 volts. Technically you don’t have to follow all the pesky safety rules around isolators, conduits, fuses and earthing. You know, all the SAFETY rules. I will be following those rules regardless. (You can find the rules online if your Google-foo is good. I don’t want to draw attention to them because hiding Standards behind paywalls is what we do in Australia: put up a fence and charge rent and if I link to the set I found they will probably be taken down.

More to come! Installing and wiring the panels is next.

DIY Offgrid Project – goals

The goals of my home brew off-grid solar storage system are:

  • make my house relatively black-out proof – keep the lights, fridge, hot water and internet running
  • run big daytime loads direct from solar – the pool, the air-con
  • reduce my effective electricity cost to $0.10 per kWh assuming a 10 year life of the system
  • cover the capital expense with two years of savings

I need to generate around 1 megawatthour of electricity each month to do this.

Based on the performance of my current system, in summer I need 5 kilowatts of solar panels, but in winter I need significantly more, around 10 kilowatts.

I have 3 kilowatts on a 2.8 kW grid-tie inverter already and I want that to export like crazy to maximise my return.

A key reason for building an off-grid solar system is to avoid losing my feed-in tariff. That’s going to take some dancing at some point after SAPN look at the NearMap photos and notice I have a bunch of new solar panels.

In the short term I need around 6 kilowatts of extra panels to generate all the electricity my household consumes.

Of course I will need to focus consumption into daylight hours as much as possible because that’s easier than storing it. My largest nighttime consumer is the pool but I can just change the timer. If I have a surplus and my car is home I will charge it. That will be a whole other project 🙂


Does installing wind turbines emit more CO2 than they save?

The Australian government’s own data: national-greenhouse-accounts-factors-2014.pdf says that when an industrial consumer in New South Wales consumes 100,000 kWh, 86 tonnes of CO2 are emitted.

Using this is generous, for consumers it’s more like 100 tonnes and it’s 134 tonnes in Victoria but let’s not point at Loy Yang and laugh.

This anti-wind farm web site: says making and installing a wind turbine emits 241.85 tons of CO2, as if this is a lot.

But that is how much CO2 is emitted in NSW when 281,221 kWh of mostly fossil fired electricity is consumed.

A 2MW wind turbine generates this in 140.6 hours of operation.

Even if the turbine only generates power at a 10% yield requiring 1406 hours of operation that’s only 56 days.

The idea that they must run hour for hour to back up each and every turbine in Australia is demonstrably wrong. By simple observation coal fired power stations are being shut down. You don’t do that unless no one is prepared to pay you for your cheap power.

So is it as simple as the anti-wind farm activist websites are published by people with faulty calculators?

Or have I missed something?