Phil and Wrenches,
Thank you for the response; good food for thought.
We looked at Aerovironment as a result of your suggestion, but it
appears to be out of production and unavailable.
Kent's suggestion to use the gennie starting battery also makes
sense, as the battery would be recharged daily and the load is
negligible. I also suspect that a Morningstar SunLight controller
with a small PV module would provide the daily start/stop signal to
the Relay Driver.
However, as Kent points out, finding a relay would be difficult, as
the customer is looking at controlling multiple (four?) SQF pumps
from AC or their respective arrays. That's too many poles at too
high a DC voltage to prevent arcing - multiple relays with 240V AC
coils paralleled would handle control of the relays, but can anyone
suggest a relay that can handle 100-150 VDC array voltage? MDI
mercury contactors, as were used in early APT/Pulse powercenters,
come to mind, available in 1-3 poles. Any better ideas?
While solutions to some of the issues are workable, ultimately I
don't see an easy way to accomplish what he wants to do. He's
talking 10-12 gpm continuously 24/7. That's 30gpm raised 400' if
array-direct, more than any solar pumps I know can supply. Thus the
diesel generator for night operation. Ranchers are used to diesel
generators.
Allan Sindelar
[email protected]
NABCEP Certified Photovoltaic
Installer
NABCEP Certified Technical Sales Professional
New Mexico EE98J Journeyman Electrician
Positive Energy, Inc.
3201 Calle Marie
Santa Fe, New Mexico 87507
505 424-1112
www.positiveenergysolar.com
On 7/5/2011 6:57 PM, Phil Undercuffler wrote:
Use
an ac charger to charge a small battery when the generator
runs each evening, and then power a timer or photosensor from
the battery. Sears, <$40. I wouldn't worry about the
phantom load of the timer -- you're running an 8kW diesel
genset throughout the night. It oughta keep up.
The question I can't answer is how this makes
sense, with diesel above $4/gallon and service every 100
hours. Did you look at an Aerovironment UPC controller
running array direct with a standard AC pump?
Phil
-----------
"When we learn how to store
electricity, we will cease being apes ourselves; until
then we are tailless orangutans. You see, we should
utilize natural forces and thus get all of our power.
Sunshine is a form of energy, and the winds and the tides
are manifestations of energy. Do we use them? Oh, no! We burn
up wood and coal, as renters burn up the front fence for
fuel. We live like squatters, not as if we owned the
property.
There must surely come a time
when heat and power will be stored in unlimited quantities
in every community, all gathered by natural forces."
-- Thomas Edison --
On Tue, Jul 5, 2011 at 4:28 PM, Allan
Sindelar <[email protected]>
wrote:
Wrenches,
A good client of ours is a rancher in the New
Mexico/Arizona border area. He has a specific need for
which I couldn't offer a simple system.
He needs to raise water from a lake 400+/- vertical feet
to a 100K gallon storage tank for agricultural use. The
site is remote. The amount is substantial - about 10-12
gpm continuously, 24/7. He would like to use 4 Grundfos
SQ Flex pumps at about 2.5-3 gpm, each running
array-direct feeding a common pipe to the tank. He then
wants to use about an 8kW (derated to 6kW for 7,500'
elevation) diesel generator (with standard two-wire
automatic start) to run all four pumps when the sun goes
down, and shut off and transfer back to PV when the sun
comes up the next morning.
How might this be done? If we assume that each pump has
four 210W modules, that would be an 80Vnom array with
MPP around 120V and Voc around 150V. I would assume that
both of these voltages are too high to use any
stand-alone AGS, such as Atkinson or Magnum. We
considered a separate tiny 12V or 24V battery with small
PV module, used just to power an AGS voltage sense
signal, with the voltage difference between float
(13.6V) and rest (12.7V) triggering a voltage-actuated
start signal, but rejected this as problematic as
battery temperatures affected charge voltages. A
self-contained time switch, such as some of the newer
Intermatic units, might work, if the right model can be
identified and isn't a substantial phantom load.
We would also have to adapt a relay to switch between
sources, with a 120 or 240 V AC relay coil current,
energized by the generator. The Grundfos IO101 AC
interface unit is manual only.
Has anyone solved this problem? Any ideas for a
reasonably simple and trouble-free approach would be
welcome.
Thank you,
Allan
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