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