In 2005 I installed a single flat plate solar hot water system, connected to an ancient Rheem 180litre HWC. That single panel easily provided too much heat for the glass lined Rheem HWC (max 65oC) during the summer months. The fortuitous acquisition of a 310 litre stainless HWC from a friend allowed the fitting of a second solar flat plate panel, and it’s been providing 95% of our hot water for the 5 months between December and April each year ever since, plus providing a very useful preheat during the autumn and winter months when electricity top-up is necessary. The payback was a very satisfactory 5 years because the cost of a kWh of power has increased considerably but mainly because I installed it myself with guidance from the helpful folk at Energy Conscious Design (Thanks Ian) What has been interesting is the number of folk who do not understand this is a simple flat plate collector system, water pumped through tubes bonded to a flat plate collector under solar rated glass heated by the sun. Many thought the panels created electricity which then heated the water.
Back in 2005 solar Photovoltaic (PV) panels were prohibitively expensive. In 2013 the situation is different, there is a PV panel oversupply and manufacturers are discounting panels aggressively. We also have a local supplier Enasolar in Christchurch who build state of the art grid tied inverters, complete with WiFi web access. It was clearly time to recheck the financials, but it’s not all about ROI, there is also the FG and HWDWTMTW factors to be considered, not to mention environmental empathy.
I fitted an energy monitor which showed the household 24 x 7 background consumption was around 0.5kW to run 2 x Mysky boxes, 1 x Tivo, 1 x fridge, 1 x freezer, 1 x home ventilation fan, 3 x WiFi AP’s and a VDSL modem plus the usual collection of wall plugs and standby devices like TV’s and PC’s. We have a 7kW heat pump, electric oven, gas hobs (LPG bottle) and electric HWC (solar assisted as above) This all combines for an annual consumption of 9600kWh. Those MySky boxes and Tivo use a lot of power, they pump out a lot of wasted heat, no energy star ratings just wanton consumerism, guilty as charged.
Careful analysis of the last 12 months power usage and the houses daytime usage suggested a 3kW system would be more appropriate than my initial ‘bigger is always better, it does not matter what the question is....’ 5kW system. I was able to get a 3kW 12 x 250W panel installation for under $12k complete with warranty and an internet connected monitoring system (essential geek functionality) Checking the daytime usage was an important decision factor, because with a grid tied system what you do not use gets exported and the price paid for exported power is at the whim of the energy retailers.
It’s been 2 weeks now since switch on and I have my very first power bill, but first to discuss how I got to the point of being able to turn it on and turn photons into electrons. Feedback welcomed if anyone thinks this is a subject worth continuing, or not.
FG = Feel Good
HWDWTMTW = He who dies with the most toys wins
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