WMOD00479

• Title: Design and Field Testing of a Remote Ground-Based Liquid Propane Dispenser
• Weather Modification - Doc Type: Report

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Design and Field Testing of a Remote Grmmd-h~)3ed
Liquid Propane Dispenser

David W. Re}nolds
Water Augmentation Group, Bureau of Reclamation, Sacramento, CA 94236-0001

Abstract. Toe design and field test results of a re;notely operated ground-
based liquid propane dispenser used for augmenting snO\....pack in the Sierr~
Nevada are described. Operation of the dispenser is controlled by a
microprocessor interfaced to a VHF radio. Software resident O;l a
Sacramento-based personal computer (PC) provides the necessary
commands for dispenser operation via a microwave mountaintop repeater.
Each microprocessor is progran-lIned with a separate J.D. allowing
independent operation. With eight analog and eight control ch:mnels
available on the microprocessor, options are availabie both for disper:ser
control and monitoring dispenser performance. Verification of liquid
propane release consists of monitoring air temperature within Lhe
evaporating liquid spray, and flow rate through the valve assenlb!y. BJ.sed
on a two-year test program, a final design has now been completed. Ten
disper.sers have been fabric~ted and installed in the field for operation this
wir-aer. If environmental procedures can be completed, this winter will be
the first year of a five-year prototype test progiam to evaluate propane as
an effective seeding agent ior augmenting winter snowpack.

1.0

Introduction

Rep.olds (1989, hereafter referred to as R89)
presented the design of a ground-based suO\-.pack
_enhancen:ent ~rog.'im ~sing liquid p~opane. Th~
Program IS desl!u~ec to Increase the tl.m water YIeld to
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Oroville Reservoir, the main reservoir of the California
State Water Project. Since completi<Ju of R89, two
winter seasons of dis?enser field testir.g have been
completed. Remotely operated liquid propac.e dispensers
were tested at high elevation sites typic::.1 of what would
be used in a follow-on five-year demor:stration program
to begin during the wbter of 1990-91.

The two-year test program determined dispenser
and communic::.tions reliability. Seeding effectiveness
could not be determined during this limited test period.
Propane releases in supercooled fog over a rr.ountain
lake were used to determine that designed release rates
(9 to 13L/hr) at temperatures anticip~ted at
mour.:aintop level (-3 to -5eC) would be effective in
producing sufficient ice crystal concentrations. These
results will be reviewed in a forthcoming paper. This
paper will concentrate on the design of the dispensers
and resul:s of t,\'o years of field testir.g.

2.0 Remote Liquid Propane Dispenser Design and
Testir.g

2.1 1988-89 Dispenser Design and Testing

The initial design of the remote liquid propane
dispeaser is described in R89. This dispenser consists of
three separate modules. Each module is installed in a
weat!:ertight box. The main mocule cor-tains system
electronics, Fig. 1, which perform two main functions.
The first is communication via a vl1F radio for
receiving control instructions and telemetering

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Figure 1 Electronics module showing microprocessor
(lower left), VHF radio (upper right) flowmeter
electronics (upper center) and switches for
initiating manual release of propane (upper left).

veriacation data back to Sacramento. The second
function is dispenser control and data collection via a
microprocessor (Odessa Engineering DSM model 3260).
Eight analog channels are available for recording data
and eight control channels for operating tank, nozzle
solenoids, and the radio. Included in this module is a
calibration unit used to convert voltages from an in-line
flowmeter to flow rates. The output of this is recorded
to one of the eight analog channels.

The second major module consists of the
plumbing and solenoid valve assembly. Two 2,176-L
(575-gaIlon) propane tanks are used to supply propane
to the dispenser. Fifty-seven liters of methanol are added
to each tank to prevent freezing of Lhe nozzle and
temperature probe. Each line coming from the tank is
connected to a solenoid allowing propane to be drawn