Power Regeneration: The majority of submers- 

 ibles recharge batteries after each dive. This 

 is accompHshed with the vehicle aboard or 

 alongside its support craft which carries a 

 battery charger. A few submersibles carry 

 their own diesel-electric motor to charge the 

 batteries while they are surfaced. 



In an extremely simplified manner, such is 

 the genesis, distribution and control of elec- 

 trical power in manned submersibles. The 

 variations on this theme equal the number of 

 past, present and future vehicles. The reason 

 for such diversity is found in the several 

 factors which enter into the choice of a sub- 

 mersible's power source. 



In a discussion of electrical power supplies 

 to meet the needs of deep submersibles, Lou- 

 zader and Turner (3) identify the following 

 as considerations important in the evalua- 

 tion of candidate power sources: 



Total Power Requirements 



Weight and Volume 



Operational Handling 



Maintainability and Repair 



Reliability 



Cost 



Total Power Requirements 



The total power required in a submersible 

 depends upon the vehicle's primary mission 

 and projected submerged endurance. These, 

 in turn, are governed by the weight and 

 volume available for the power package. The 

 major power user is propulsion. Running a 

 close second, and sometimes exceeding pro- 

 pulsion are external lighting and scientific or 

 work equipment requirements. Hotel load 

 (life support, communications, avoidance 

 sonar, monitoring instruments) is a con- 

 sumer of power which must be dealt with on 

 a continuing basis, and, finally, the prudent 

 operator will maintain some amount (25%) of 

 power in reserve. 



An examination of Table 7.1 reveals that 

 the total power capacity (kWh) of submers- 

 ibles ranges from 2.5 to 1,200 kWh. Of the 83 

 vehicles for which there is information, 74 

 carry less than 100 kWh while the remain- 

 der, nine, exceed this value. Further exami- 

 nation shows that 61 vehicles carry 50 kWh 

 or less. The distribution and nature of this 

 power varies from vehicle-to-vehicle. Some 



operate solely with 12 VDC (KUMUKAHI), 



while others operate with 12, 28, 60 and 120 

 VDC and carry an inverter to supply AC 

 power as well, e.g., SDL-1 . There are no hard 

 and fast rules governing total power require- 

 ments or rated voltages, but once the total 

 power capacity is established, one can calcu- 

 late how much will be available for various 

 instrument or machinery functions and for 

 what mission profiles. The ideal procedure, 

 however, would be to determine the power 

 requirements through power spectrum anal- 

 ysis of the vehicle's intended mission(s) and 

 then design the vehicle and its power system 

 accordingly. Many builders have followed 

 this latter procedure, but in several in- 

 stances, it would appear that a more casual 

 approach was taken. 



An example of a power spectrum analysis 

 is presented in Figure 7.2 which was per- 

 formed by Bodey and Friedland (4) for a 

 small submersible on a "typical" mission. 

 First, the authors divided the overall mission 

 into categories (pre-dive, dive, etc.) where 

 the operation of various electrical devices 

 could be prognosticated. Then, an operating 

 time for each device was assumed and multi- 

 plied by the power it would require (time x 

 amps X voltage) — based on manufacturer's 

 specifications. Summing each column pro- 

 vided the power for each category and, 

 hence, the total power to complete the 6-hour 

 mission. It is important to note that almost 

 one-half of the total kWh was allocated for 

 reserve power. Such power analysis is una- 

 voidable when the owner plans to lease the 

 vehicle's services to a user who desires to 

 operate his own electronic equipment in ad- 

 dition to that listed in Figure 7.2. 



Weight and Volume 



The small size of most submersibles places 

 severe restraints on the weight and size of 

 possible power systems. The decision to lo- 

 cate the system inside or external to the 

 pressure hull is critical in determining the 

 total power a vehicle will carry. If the power 

 system is located within the hull an increase 

 in propulsion power is needed because of the 

 added hull weight. This also decreases the 

 vehicle's payload and submerged endurance 

 and limits the volume available for internal 

 instrumentation. Locating the system exter- 



316 



