Power and its Distribution
Types
of Power
Pneumatic: compressed air used to empty
ballast tanks of seawater
Hydrostatic: operation of pressure depth gages
and pressure compensation of batteries
Electrical:
Types:
Batteries: most commonly used
is Lead-Acid (other types: Nickel-Cadmium and Silver-Zinc)
Advantages:
simple construction (all components
contained within battery)
operate at ambient deep-sea pressure
(not in hull)
no moving parts
operate at any sea temp
highly reliable, failure occurs one
cell at a time
available commercially in a large
variety of types
Disadvantages:
energy density (energy per unit
weight) and specific energy (enrgy per unit volume) are low
designed for operation at power
levels of not fmore than a few tens of watts per pound and a few kW per cubic
foot
Fuel Cells: converts energy
from the reaction of two chemicals into DC electrical energy. Battery's energy
is stored; fuel cell produces current on demand as long as chemicals are supplied.
Advantages:
turn-around time is minimal (only
the refurbishing of fuel and oxidant is required)
ligher than comparable batteries
take up less space than comparable
batteries
longer life than conven tional
underwater power sources
may be tapped at any voltage and
this doesn't affect cell life
silent and operate at relatively low
temps
Disadvantages:
not as much info on fuel cells as
batteries
more costly than batteries
Nuclear Power: um, no.
Cable-to-Surface (Umbilical):
cable from submersible to power source on the surface. Once again, no.
Diesel-Electric: diesel
engines in their power inventory for surface propulsion, recharging depleted
patteries, and powering an air compressor to refill air tanks
Applications of Electrical Power:
·
Propulsion:
all submersibles use electrically-powered motors for lateral or vertical
maneuvering
·
Life
Support: All submersibles use electrically-powered carbon dioxide scrubbers
·
Communications:
two-way sub-to-surface communication
·
Illumination:
internal and external lighting
·
Work
and Operating Instruments: scientific and engineering instruments, such as
those used to control and operate the vehicle
·
Ballast
Drop: electrical impulse or signal to activate weight drops or fettison
instruments
·
Manuevering:
orient propulsion devices or dive planes and rudders
·
Sensors:
status sensors
·
Emergency
Indicators: seawater leak indicators
·
Tracking/Navigation:
these systems
·
Hydraulics:
hydraulically powered devices require electricity to pump hydraulic fluid
Terminology and General Considerations:
Power Distribution:
connectors and cables are used to carry the power. Electrical Hull penetrator
permist passage of current through the pressure hull
Power Changers: Batteries and
Fuel Cells generate DC. Many instruments need AC. Inverters change DC to AC,
may be within or external to hull. Other components may operate on lower DC
voltages, so a converter is used.
Power Protection: three
approaches used to protect batteries from seawater and pressure
1. pressure-compensation: battery
placed within sealed and vented case filled with a dielectric fluid (usually
oil) and connected to a compensating fluid reservoir which acts to maintain
zero or slightly positive pressure differential across the enclosed
oil/seawater face
2. pressure-protection: battery is
enclosed in a pressure resistant pod outside the pressure hull and maintained
in a dry, 1-atm environment
3. interior location where the
battery is placed within the pressure-hull
Protection from the Power:
sound circuit design, fuses, circuit breakers, shielding, physical separation
of two cables
Power Monitors: Ampere Hour
Meter ( battery current), Voltmeter (battery voltage), Ground Measuring System
(detect ground currents on the battery), Megohm Meter (ground resistance
readings)
Total Power Requirements:
Weight and Volume
Operational Handling
Maintainability and Repairs
Reliability
Cost