Subject: Re: Solar on the Road...

From: [email-masked] (Nick Pine)
Date: 27 Apr 1996 09:14:02 -0400

Donald Kulha <[email-masked]> wrote:

>      I've been working on a somewhat interesting project lately...

Sounds nice :-)

>The maximum daily power production has been about 1400w so far...

I guess you mean 1400 W-h? Are you wasting the rest of the 8,000-10,000 W-h
of sun that falls on the photovoltaic panels on the roof of your van as heat?

>     The main use of the system will be to power computers, lights, a fan,
>my coffee grinder, a stereo, a deskjet 660 and misc other stuff when I
>work with friends on our CD-ROM. The system also powers a CB, a
>2-meter/440mhz Kenwood transceiver, a TNC, a cell phone and charges
>various sized small nicads for radios, flashlights, a shaver, etc.

You don't mention how you keep the van warm inside or make hot water. Perhaps 
the fan could be a solar chimney. Or you might trickle a little water over
those PV panels, under another layer of single polycarbonate glazing. Or hook
up a small model-sized jet engine powered by Freon, a mini-version of the
Ormat turbine generators used to make 5 million watts of electrical power
>from  63 acres of solar salt ponds in the dead sea, starting from 170 F brine.

Nick

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From: [email-masked] (Mike Morris)
Date: Sat, 27 Apr 1996 22:10:50 pdt

>From: [email-masked] (Nick Pine)
>Subject: Re: Solar on the Road...
>Date: 27 Apr 1996 09:14:02 -0400

In article <[email-masked]> [email-masked] (Nick Pine) writes:

<discussion of solar panels on the roof of a van>

>from 63 acres of solar salt ponds in the dead sea, starting from 170 F brine.

Could you elaborate about the model-sized jet engine powered by freon?
I've not heard about that before...

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From: [email-masked] (Nick Pine)
Date: 28 Apr 1996 15:03:55 -0400

Mike Morris <[email-masked]> wrote:
 
>>...Or you might trickle a little water over those PV panels, under another
>>layer of single polycarbonate glazing. Or hook up a small model-sized jet
>>engine powered by Freon, a mini-version of the Ormat turbine generators 
>>used to make 5 million watts of electrical power from 63 acres of solar
>>salt ponds in the dead sea, starting from 170 F brine.
 
>I've not heard about that before...

As I understand it, these Ormat generators are more or less full sized
jet engines, running on Freon in a Rankine thermodynamic cycle. I think
their thermodynamic efficiency is only 6%, vs. the 30% Stirling cycle
generators used by Cummins with tracking and concentrating solar collectors
with higher temperature differences using liquid sodium heat transport, but
it seems to me that what matters is overall efficiency, ie the product of
solar collection efficiency and engine efficiency, and cost-effectiveness
in $/kWh. Salt ponds have higher collection efficiencies and they are a lot 
cheaper than tracking concentrators. 

If you want to read more about this, you might try contacting Ormat or
looking at 

Tabor, H., Proc. of the UN Conference on New Sourches of Energy, 4, 59,
(1964). "Large Area Solar Collectors (Solar Ponds) for Power Production,"

Tabor, H. and R. Matz, Solar Energy, 9, 177, (1965). "Solar Pond Project,"

or

Tabor, H. and Z. Weinberger, in Solar Energy Handbook (J. Kreider and
F. Kreith, eds), McGraw Hill, NY (1981) "Non-convecting Solar Ponds."

Nick

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From: [email-masked] (John D. Muccigrosso)
Date: Mon, 29 Apr 1996 23:52:25 -0400

In article <[email-masked]>, [email-masked]
(Nick Pine) wrote:

| Donald Kulha <[email-masked]> wrote:
| >The maximum daily power production has been about 1400w so far...
| 
| I guess you mean 1400 W-h? Are you wasting the rest of the 8,000-10,000 W-h
| of sun that falls on the photovoltaic panels on the roof of your van as heat?

Sorry to butt in here, but since Nick brought it up...;-)

Watts _are_ power, aren't they?  Watt-hours are joules (or watt-seconds
are anyway) and that's energy.

-- 
John D. Muccigrosso                         Department of Classical Studies
[email-masked]                            University of Michigan

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From: [email-masked] (Nick Pine)
Date: 30 Apr 1996 06:50:42 -0400

John D. Muccigrosso <[email-masked]> wrote:

>|Donald Kulha <[email-masked]> wrote:
>|>The maximum daily power production has been about 1400w so far...
>| 
>|I guess you mean 1400 W-h? Are you wasting the rest of the 8,000-10,000 W-h
>|of sun that falls on the photovoltaic panels on the roof of your van as heat?
>
>Watts _are_ power, aren't they?

Yes, but I'm sure Don meant Watt-hours above, as in "The maximum number of
bushels of potatos I have dug in a day was 5," not "my personal maximum 
instantaneous potato digging rate was 3 per second." Altho the two are
equivalent over a day in some sense, the first is a quantity of energy,
and the second is an instantaneous _rate_ of energy collection, ie a
(potato) power. Like miles vs miles per hour.

Don also said his solar collection area was about 4' x 8', ie about 3 m^2,
and most places receive about 3-5 kWh/m^2 on a day, so at 10% PV collection
efficiency, he would collect about 3 m^2 x 4,000 watt hours/m^2/day  x 0.1
= 1200 W-h of energy in a day.

And he mentioned that his peak power output was 375 watts nominal. One can
collect about 3X the peak power output in Watt-hours per day, numerically-
speaking, as a very rough rule of thumb. 

Watt-hours are joules (or watt-seconds are anyway) and that's energy.

Right, 1 Watt-hour is 1 Watt-hour x 3600 seconds/hour, which is 3600 joules.

My point was, why waste the other 90% of the sun, while using some other
device to heat water? Why not trickle some water over your PVs to collect
some of that 90% "waste heat," or put them inside a sunspace and collect
some warm air to heat the attached house, or add some 2:1 reflectors and
collect twice as much electrical energy with the same hideously-expensive
PV cells, while making some hot water too? The electrical output goes down
a bit, but on the whole, this seems worthwhile, eg using Ovshinsky's cells
at $3./50/peak watt, with 50 W/m^2 @ 20 C and 45 W/m^2 @ 60 C.

Nick

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From: [email-masked] (AI Group)
Date: 1 May 1996 13:07:45 GMT

: 
: >      I've been working on a somewhat interesting project lately...
: 
I would like to set up solar panels on top of my Pop up camper.  Any 
suggestions?

Would it be practical to buy some of the small ones and connect them in 
series to increase the wattage enough to charge the 12 v battery that runs 
the inverter?
Henry
[email-masked]

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From: Pete Tyjewski <[email-masked]>
Date: Thu, 02 May 1996 16:43:40 -0700

> >from 63 acres of solar salt ponds in the dead sea, starting from 170 F brine.

why not just put a tire on the shaft of a generator and hang it on the 
bumper be more reliable than the turbine..

or Direct drive to the engine that way it would still work at stop signs

or did I miss the point again?
Pete

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From: [email-masked]
Date: Mon, 06 May 1996 12:50:44 GMT

>series to increase the wattage enough to charge the 12 v battery that runs 

There is a company that produces solar charging systems for RVs. I had
a catalogue a few years ago. Don't remember the name but someone else
might.

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From: [email-masked] (Nigel Roberts)
Date: 9 May 1996 01:40:37 GMT

>a catalogue a few years ago. Don't remember the name but someone else
It is indeed quite possible and feasible to mount solar panels on your 
RV and use them to charge your battery.  We produce a number of kits 
specifically for use on RV's.  You can find further information on our 
home page http://www.sovran.ca/~sovran.  Feel free to e-mail us if you 
have any specific questions.