DD> I use the electriciy primarily for the refrigerator, lighting,
DD> and running the little audio system. Eventually I'll have a
DD> "composting" toilet. That requires a little 12v fan (think
DD> computer PSU) running 24/7 

 What's the difference between a composting toilet and a deep hole
outside? Is the composting toilet inside?

BL> You're still stuck with a few hundred watts for the electrics,
BL> but they're only intermittent ( a few hours at a time).

DD> When I'm in residence the fridge is turned on 24 hours. In the
DD> warmer weather its duty cycle is about 40%. I'm thinking of
DD> putting an extra layer of insulation around it.... 

 Actually, the design of fridge insulation is pretty good. Leaks
are a more likely cause of losses. An easy way to check is measure the
fridge outside surface against a similar metal in free air. I'd be
surprised if there's more than a couple of degrees in it.

DD> All of solar powered blurb sites on the web write of not
DD> expecting more than about 6 hours of usable sunlight per day. I
DD> have some tall trees on my property which shade the panels for
DD> some of the day. It seems I cannot have shade and sun at the
DD> same time (maybe I'll have cake and eat it instead). 

 It's easy enough to check for yourself, and discouraging too. It's
not just "sunlight," it's the angle of the sun. You get more in the
two hours around midday than the rest of the day put together... and
that assumes you've got the cells pointed at the right angle, and
north.

DD> At this time of the year I can see a charge rate of 20amps
DD> going into the battery during the middle of the day. In the
DD> cooler months when the sun is lower it's only about 3-5. 

 That's exactly right. The trick is to point the cells at the lower,
winter sun.

DD> I could cut down the trees - but that would make it a whole lot
DD> hotter (and the fridge duty cycle would get worse). The
DD> anti-tree clearing laws may have something to say too... 

 Check your amps through the day... they drop off to buggery once the
sun moves off centre. I'd guess that the trees only cast shade at low
angles anyway. As long as it's clear at midday...

DD> A thirty metre tower with the panels near the top (and a space
DD> for a wind turbine - it's breezy at the top of the canopy)
DD> would see more production. Towers of this nature can be a tad
DD> expensive. 

 That sounds like bullshit to me, David. The breeze is stronger up
there (and its direction more reliable), but the sun isn't. It always
amuses me when they mount a satellite dish on the roof, as if an extra
six-metres makes any diference in 40,000 km.

Regards,
Bob


 




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