Wednesday, October 12, 2016

End of winter recap

Now that winter is over, how have we done?


My last post about my solar systems' performance has made me think a bit more about their performance, so I've done some analysis.

I have taken some meter readings over winter, which gives me
  • solar PV production over winter
  • grid draw over the same period
  • grid export over the same period
This gives these data (for the period June 1st to October 6th):
average total daily consumption (PV self consumption and grid-draw): 6.26 kWh
average Daily PV production: 6.13 kWh
average daily grid draw over winter: 3.9 kWh
average daily grid export over winter:  3.7 kWh

The same calculations for the period June 1st to August 2nd look like this:
average total daily consumption (PV self consumption and grid-draw): 6.29 kWh
average Daily PV production: 4.67 kWh
average daily grid draw over winter: 3.91 kWh
average daily grid export over winter:  2.66 kWh
 We tend to cook more with the electric oven in winter, which I think largely explains the higher daily consumption. Also, we use lights more, etc. We needed to boost the solar hot water system once, for about an hour, which used about 2.4 kWh.
Overall, I am fairly happy with these numbers. I think we're losing at least 0.5 kWh/day to phantom loads, but there's only so much energy I have for turning things off at the power point. Clearly, for our PV to cover our consumption in winter, we need ~50% more panels.

Propagation area

I've been busy building a spot for seed propagation. Seeds need constant moisture, and the requirement that we keep them moist for several weeks was just too much for us (forget to water them for a day and they're dead). I built this bench using almost 100% found or scrounged materials. Even the nails and bolts were mostly reused. It's also amazing what you can build with poly pipe and clothesline! It has a watering system that waters it for 1 minute every 6 hours. Bonza!

tomatoes and beetroot and basil, oh my!

does your propagation table have turned legs? ;-)

Composting loo

Now that we've had the last rain until about March (well, we can't expect much!) I'm again feeling unhappy about putting potable water down the toilet. I've started building a box composting toilet. It's designed to hold a 20 L plastic bucket and a urine diverter. It's made from pallet wood (and pallet nails), with a few bits of nice timber I found on an old air-conditioner facade that I found on the side of the road (they made them attractive in the old days!). Not quite finished, but getting there. As I said in a previous post, I'm using this device as a urine diverter, and they have some plans online for how to make the toilet. I am vaguely following those.

It is spring, and the garden is blooming. Here are some photos from the garden:
New citrus grove (sorry for the dark photo)

Broad beans


  1. Hi Angus,
    Well done with the solar! Yup more panels is a good thing, although your inverter will have an upper limit. Nice work with the propagation setup too. And I look forward to reading about your composting loo setup in the future. It is a great idea as doesn't it seem a bit strange to dump our effluent in the ocean? Your broad beans are miles ahead of here too and they are looking very good.

  2. I'm still mulling over your Antarcticite PCM idea. Here is one with a higher melting point sunamp heat battery YouTube I think they use a HWS heat pump. Also revisiting some older Canadian ideas on cost effective insulation. I am beginning to see why some of the retrofits I have looked at have worked so poorly, small gaps and heat bridges lose a ton of heat.

  3. Hi Chris,

    Thanks -- yeah, we'll have wattage and current and voltage limits that will need to be respected. It will take some thought...

    regarding effluent in the ocean, the best way I’ve heard it described is that we used to have a closed cycle of fertility — from plate to toilet to field to plate. Now we dispose of the waste in the ocean and need to bring in artificial fertility — we took a solution and neatly divided it into two problems :-)

    The beans are amazing — I took that photo at my eye-level (I’m about 177cm tall). I’m not sure if many will make it inside the house though — the kids love eating them.

    Cheers, Angus

  4. Hi Yahoo2,

    I've seen that company, but not this video. It's unclear to me whether it uses a heat-pump or not. There could have been a compressor in the box, but there wasn't any clear condensor. I'm thinking perhaps not. (Also, as far as I know, there is no supply-constrained heat-pump on the market -- ie. a heat pump that can work with whatever intermittent power is available to it). The other thing about the sunAmp, is that it's only (apparently) designed for storing heat -- not coolth (this is not surprising since it's designed in Scotland!)

    Regarding building performance, yes it's a weak-link-in-the-chain sort of thing.

    Cheers, Angus

  5. Hi, Sun amps brochure shows a heat pump mounted on the outside of the house and they call it "sophisticated" so who knows! I have played with stepper motor driven compressors a bit, infinitely variable speed is their bread and butter.I have a danfoss controller here somewhere that was designed for a simple solar freezer in the African market (no batteries), using bottled water as PCM. The inverter style AC units are technically capable, it just needs the right control. I suspect that without that fine control they could still ramp heat transfer in stages and use a resistive heater to fill the gaps or capacitors to smooth the electrical input. Dave Southgate has a nice article on using the immersun to charge his Nissan leaf that is a very basic version.
    I have looked at my own temp data and it looks like the brick walls smooth out the temp change. I lose .25 degree per hour from 4.30pm till 7.30am and gain .5 degree when the sun is out. body heat and whitegoods account for .05 degree of that. I expected it to vary with outside temp but it doesn't, the temp gain varies every day but the passive loss is rock solid. Ive scribble some calculations about tanks in insulated garden sheds, coldrooms, flued condensers and converted freezers but I'm a long way from costing and spreadsheeting all the variables. thanks yahoo


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