Friday 3 September 2010

Going Green(ish)

Yesterday I signed a contract for NuEnergy to install a 1.5kW photovoltaic power system on our roof. The installation won't happen for 10-12 weeks (as all the application paperwork for the Federal government rebate has to be approved before installation can commence). So, hopefully, the system will be installed before Christmas.

I decided to sign-up immediately because the state government feed-in tariff of 66c per kWhr power generated by small PV systems is due to be reconsidered now that the review threshold of 50MW PV capacity has been reached. The review is due to be completed by the end of September, and soon afterwards new legislation will be passed by state parliament for a new (probably lower) Gross feed-in tariff, or possibly removing the option of Gross feed-in for new agreements. So, time was of the essence in getting signed up for the existing Gross feed-in tariff with Energy Australia.

The PV system should cost around $3,000 installed (due to the Federal governments rebate worth about $6,000!), and at a Gross feed-in tariff of 66 per kWhr the system should generate about $1,400 income per year until the end of the current tariff in 6.5 years time. So the PV system should pay itself off in the first two years, and earn us a net profit of around $5,000 by 2017. After that it should continue to provide about 15% of our energy needs at zero cost, saving around $500 off our annual electricity bill. Since the cost of electricity is rapidly rising the annual saving from 2017 is likely to be much greater, but we will still have a much bigger electricity bill than today. By 2017 there may be more efficient PV cells available, so it might be worth augmenting the capacity of our system at that time.

Once the system is installed and I have actual energy production data available from the 'smart' meter, I may experiment with boosting output by positioning some mirrors around the PV panels. As second-hand mirrors are available for minimal cost, it may be possible to reflect additional sunlight onto the panels relatively simply. A carefully positioned fixed mirror would direct additional sunlight onto the panels in the middle of the day, and only cast a shadow onto the PV array when the sun is at low altitude. The net effect should be a gain in total daily output from the PV system.

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Bigchrisb said...

Two comments - nice idea about the mirrors! However, when doing this, bare in mind that the current output from the panel is constrained to the limit of the lowest cell in the string / circuit. That means that if reflecting additional light onto the panel, you will need to get the light distribution close to even across the string. Check what orientation the strings of cells are wired up - this may impact on how you place the mirror array.

Secondly, congratulations for installing a PV system - its helping to reduce Australia's carbon emissions from electricity emissions. However, one common misunderstanding is that when you use feed in tariffs, you are effectively selling the carbon abatement. This means that your power use will have the same greenhouse impact as prior. Good deal financially, but means that your own footprint is no greener than it was previously. said...

Yes, I'm be making and selling green power to others for 66c per kWhr, but I haven't signed up for 'green' power so I still buy 'black' power as cheap as possible (about 6c for off-peak, 16c for the most of my std power us, and 25c per kWhr for the 'excess' use). Hence, I'm greenish, rather than greem ;)

ps. I recently got some information about metal roof panels that are shaped to look like normal roof tiles. Within a decade I'd expect PV technology to have developed a panel that is high efficiency and shaped to match standard roof tiles. Such panels could be installed in amongst standard roof tiles during new house construction rather than being added on top of the roof post-construction (perhaps new house will be required to use them - similar to the rules on water efficiency, underground power line connectivity etc.).

I have tentative plans to build a retirement house on my parent's 10 hectare hobby farm in about ten years time - I might have it designed to be 100% solar powered, although could be issues with PV systems not being bush-fire resistant.