Al salaam a'alaykum Bob

17 Jan 04 14:55, Bob Lawrence wrote to David Drummond:

 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 

 BL>  What's the difference between a composting toilet and a deep hole
 BL> outside? 

A composting toilet has a (usually) plastic tank with grates inside and
fan(s) which force a dry decomposition of the contents. After a year one
removes "compost".

 BL> Is the composting toilet inside?

It can be. The tank is usually under the floor.

 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.... 

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

The outside body of the fridge feels cold to the touch.

 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). 

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

Yeah, I still have to align mine properly.

 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. 

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

It's behind the trees much of the day in winter....

 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... 

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

Indeed.

 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. 

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

The advantage of having the panels up the tower is LESS SHADE from the trees.

Regards,
David

--- Msged/LNX TE 06 (pre)