Subject: Sun Juice 2 of 4

From: [email-masked] (Scott Parks)
Date: 13 May 94 22:05:22 -0800

-=> Note:
Forwarded (from: homepowr) by Scott Parks using timEd.
Originally from Don Kulha (1:125/7.0) to All.
Original dated: May 05 '94, 10:04

Use
When a customer orders, Lu slices up the appropriate 
ingredients on the stainless steel work top, flips on the juicer, 
and tosses everything in. The juice pours out the bottom, and 
all pulp is diverted to a waste bucket. After the sale, he 
washes his hands in the hot water and is ready to start all 
over. He's still waiting for the day he has to say "please wait a 
few minutes while the batteries charge". That will mean he 
has a line of people buying juice, one after another. The system 
has proved capable and completely reliable through the short 
and cloudier days of winter. Summer production will be a snap.
The electrical capacity was sized to meet the single load. 
Initially, Lu made the mistake of believing the rating plate on 
the side of the juicer, and ended up with too small of an 
inverter. The current Trace inverter, however, seems to be 
working fine. The motor is rated at 1/3 hp, but a closer look at 
the plate shows that it is rated at 5.7 amps, and under load 
(carrots!) surges to 1000 watts. Also, the motor simply can't 
put out as much power with the modified sine wave it's being 
fed.
The PV panels generate 260 Watt-hours on a good four hour 
day. One cup of juice takes about 3.3 Watt-hours (20 seconds x 
600 Watts / 3600 seconds/hour = 3.333 Watt-hours) to 
squeeze. This is only an approximation - carrots obviously take 
lots more power than oranges, but with these numbers he can 
max out at 78 cups per day. Of course, by starting the week 
with a full charge and ending with a low one he can exceed this 
amount pretty handily. It takes about 3 minutes to recharge 
from each cup of juice. The 4 hour limit was imposed by the 
health department. If he cleans the juicer and gets fresh 
produce, he can go on for 4 more hours.
The water system is charged up with hot water in the morning, 
and then kept piping hot with a simple double reflector system. 
Pressure is provided with a foot type air pump - another of the 
clever touches in this whole system.
After he closes up shop, he pedals over to 20 Carrots (a local 
juice bar/produce store) to clean the equipment and stash his 
food. Health department regulations make this easier and more 
practical than subjecting his kitchen to inspection. The cart is 
taken home and locked up. The inverter is removed and taken 
indoors for protection from humidity. Albuquerque does have a 
5 month freeze season, so care must be taken to keep frost out 
of the inverter.
Why didn't he use a 12 Volt DC system and reduce the initial 
outlay and complexity? For several reasons tied to the 
educational goals and versatility of this cart, that's why. 
There simply aren't equivalent juicers (or many other items) 
available in 12 Volt DC models. He would have had to rig a 12 
Volt motor with belts to a gutted 115 vac juicer, which would 
look like some crazy contraption. He wanted to present the 
image of solar power driving mainstream applications, not 
some uniquely modified equipment. With the full system he can 
explain the process for producing home power, and help people 
to 'click' that it really does work here and now. Also, the cart 
can be used and expanded to drive any other electrical 
equipment that may be needed for work away from the grid - 
construction, repair jobs, whatever. Certainly a 12 Volt only 
system could be made for this application, but it wouldn't 
provide all the same benefits.

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