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The Special Boiler Design Bureau JSC is Russia's only enterprise involved in the shipborne AIP plant development and production with genuine experience in developing electrochemical generator plants for naval submarines.

1. Electrochemical generator-based AIP system

In the late 1980s, work on power plants for Poisk-6 and Sirena-K was suspended, following the acceptance of contract design and successful tests of scaled models and prototypes. The year 1991 saw the completion of overall effort to design an electrochemical generator-based AIP system (Kristall-20) for the Pirahnya-class submarines. This was the first national full-size 130 kW power plant equipped with electrochemical generators, presenting the first generation of Russian marine AIP systems, which was developed, manufactured, tested on stands, and accepted by an interdepartmental commission. 

During the development project, cooperation infrastructure was fully established with almost 30 specialized enterprises; basic principles and development trends of the marine electrochemical generator-based power plants were formulated, which envisaged provision in the near future for submarines' continuous multi-month  submerged missions with assured power plant operational safety; and considerable knowledge was acquired of basic AIP systems and equipment, including various types of hydrogen and oxygen storage systems. The following variants have been researched: bottle-type storage of gaseous reagents at a pressure of 40 MPa; bound hydrogen storage in sodium boron hydrate and hydro-reacting compounds; bound oxygen storage in hydrogen peroxide and sodium and potassium permanganates;  hydrogen and oxygen cryogenic storage; and, finally, bound hydrogen storage in intermetallid compounds. The majority of these variants were developed through the phase of scaled models and prototypes which were tested on stands and certified  by  interdepartmental commissions. 

As the electrochemical generator AIP plants belong to an unconventional type of power-generating systems which use such agents as hydrogen and oxygen, special attention was paid to the development of fire/detonation proofing techniques, ground storage, and refueling facilities. 
 

2. Layout of AIP system in an Amur-class submarine

 
During the development of  Kristall-20, we conducted a thorough examination of foreign AIP experience and domestic space-oriented programs pursued by the Ural Electrochemical Works (UEKhW) in electrochemical generators and the Korolev  Rocket and Space Corporation Energia in LOX/LH2 storage systems and overall power plant design. Although the UEChW-designed Photon generators for space applications do not in many terms meet  the requirements of shipborne equipment, they feature high fuel efficiency and acceptable weight and size parameters. Therefore, SKBK contracted UEChW to develop from Photon a submarine electrochemical generator which would feature a six-fold increase in service life, 320 V battery voltage, significantly lower cost, and full adaptability to submarine conditions. 

Currently, SKBK is involved in the development of Kristall-27 second-generation automated AIP system with electrochemical generators, which  surpasses all first-generation  designs in terms of performance. 

The Kristall-27 outline design has already been approved with a considerable amount of contract design work completed and engineering documentation for models and prototypes under preparation. The experience and knowledge gained during the development of first-generation AIP systems (fire/detonation protection, shore-based support equipment, etc.) are being fully exploited in the current project. 

A version of automated electrochemical generator system, Kristall-27E, is being designed to generate electricity for the propulsion and power supply of the Amur-class submarines. It increases their dived endurance by 15 to 45 days at economic speed (continuous or with intervals). It will also be able to charge the main batteries and ensure additional submerged operation capability. 

The main operating principle of electrochemical generator AIP system is based on the direct conversion of chemical energy produced by the  reaction of fuel (hydrogen) and oxidizer (oxygen) into electrical energy without intermediate conversion into heat energy and inevitable in this case energy losses typical to all thermal engines. Energy conversion takes place in a fuel cell. The AIP plant employs an electrochemical generator with low-temperature hydrogen/oxygen fuel cells. 

The AIP plant comprises: 
— electrochemical generator; 
— intermetallid hydrogen storage and feed system; 
— cryogenic oxygen storage and feed system; 
— fire/detonation protection system; 
— thermostatic regulation system; 
— control system; 
— power-supply system. 

Hydrogen is bound in intermetallid compounds, while oxygen is kept in liquid state cryogenically. 

Safety issues have been considered most thoroughly. 

Several safety levels were envisaged to provide for fire/detonation-proof operation of the power plant: 
— dedicated facilities and design features of equipment and systems are intended to cut off the reagents' feed in emergency system depressurization and exclude a possibility of detonating mixture formation (as a result of  reagent leakage) and generation of energy pulses capable of initiating fire or detonation; 
— the control and fire/explosion protection systems are designed to automatically check the power plant's technological parameters and the atmospheric parameters in electrochemical generator sections and intermetallid accumulators to cut off the reagent feed in emergency; 
— automatic detection of fire/ 
detonation conditions in power plant compartments; 
— dedicated systems for fire/ 
detonation prevention, including  the emergency refluxing of atmosphere in power plant compartments; 
— containment of fire/detonation nodes within the electrochemical generator compartment by high-strength bulkheads. 

The above principles were implemented by a set of design, structural and technological solutions, as well as organizational and technical measures which were developed by SKBK, jointly with the  Applied Chemistry Research Center, All-Russia Firefighting Research Institute 
(VNII PO) and other organizations,  using prototype hydrogen/oxygen systems tested on a dedicated fire/detonation test stand erected at the Sokol test complex, as well as on test stands of the above-mentioned enterprises during conduct of R&D work on Kristall-20. Their efficiency was confirmed by the State Commission which accepted the Kristall-20 powerplant. 

These tests confirmed the power plant's  complete ecological safety because no problems exist with either the reaction product (water) disposal or the overall disposal of power plant's equipment and systems  when submarine's service life is expired. 

Equipping nonnuclear submarines  with AIP systems increases their costs due to the following factors: 
—  the cost of power plant's pilot (series) production model can account for approximately 15-20 percent of total submarine's cost; 
— requisite R&D and engineering costs also increase submarine's price tag. 

Operation of submarines equipped with AIP systems in conjunction with diesel-electric submarines is cost-effective, because the total number of submarines can be reduced owing to the considerably enhanced combat efficiency of the fleet. 

FRG contemplates to replace 18 diesel-electric submarines of Project 206/206A with four Project 212 boats equipped with AIP system based on electrochemical generators. 

Countries involved in the production of AIP systems for submarines are going not only to supply them to their own Navies but (owing to the AIP technology high export potential) sell them abroad. These countries primarily include Germany, Sweden, and France (the latter  intends to only export the AIP-equipped submarines). Currently, several attractive commercial projects are underway in this field. 

For example, four Project 212 submarines equipped with an electrochemical generator AIP plant are being built in Germany under a DM 2.6 billion government contract. Consequently, each submarine will cost about U.S. $370 million. 

From two to four  Project 212 submarines will be possibly built in Italy in team with Germany also under a 
government-sponsored contract. 

France is planning to supply to Pakistan three Agosta-class submarines, one of them equipped with the MESMA steam-and-gas turbine AIP system, under contract with a total cost of about $900 million. 
 

3. Shore-based refueling  complex for submsrines equipped with the Kristall-27E AIP system (a- hidrogen, b-oxigen)

 
Apparently, a Russian-made submarine equipped with the electrochemical generator AIP plant will not yield to its foreign counterparts in performance, specifically to German Project 212 submarines, and will  successfully compete on the market. 
The Kristall-27E AIP plant, featuring the intermetallid storage of hydrogen, cryogenic storage of oxygen and low-temperature electrochemical generator with alkali matrix electrolyte, fully meets all requirements including those of fire/detonation safety, and can beat the AIP system of Project 212 submarines, surpassing it in terms of fuel efficiency and shore-based support facilities due to the availability of  dedicated autonomous shore-based refueling complex. 

The shore-based refueling complex does not integrally belong to the AIP system. However, it can be supplied optionally: this feature contributes to the competitiveness of the Russian project. Customer will receive in a single package the autonomous refueling complex which will provide hydrogen and oxygen for the submarine's AIP system in peace and war time. As the characteristics of the second-generation air-independent propulsion systems based on electrochemical generators are not yet marginal, they can be considerably improved mainly through better organization of hydrogen storage and feed system on board a submarine. Under the AIP system development concept evolved by SKBK, third-generation shipborne AIP systems will be developed. They are to enter service with conventional submarines after the year 2010. 

While the first- and second-generation AIP systems serve as auxiliary powerplants only at economic speed and make it possible to increase the submerged endurance of a submarine by almost 10 and 15 to 45 days, respectively, the third-generations AIP systems feature a single all-mode powerplant which provides for both underwater and surface navigation at all power ratings. The third-generation AIP systems increase underwater endurance of conventional submarines to 60 - 90 days and, in terms of major parameters, almost equate them with nuclear boats. peace or war time. 

As the characteristics of the second-generation air-independent propulsion systems based on electrochemical generators are not yet marginal, they can be considerably improved mainly through better organization of hydrogen storage and feed system on board submarine. Under the AIP system development concept evolved by SKBK, third-generation shipborne AIP systems will be developed. They are envisioned to enter service with conventional submarines after the year 2010. 

While the first- and second-generation AIP systems serve as auxiliary powerplants only at economic speed and make it possible to increase the submerged endurance of a submarine by almost 10 and 15 to 45 days, respectively, the third-generation AIP systems feature a single all-mode powerplant which provides for both underwater and surfaced navigation at all power ratings. The third-generation AIP systems increase underwater endurance of conventional submarines to 60 - 90 days and, in terms of major parameters, almost equate them with nuclear boats. 

The Special Boiler Design Bureau JSC is Russia's only enterprise involved in the shipborne AIP plant development and production with genuine experience in developing electrochemical generator plants for naval submarines. 

Building on the existing cooperation ties with other organizations, SKBK is prepared to develop, manufacture and deliver to customers the AIP plants rated at 10 to 600 kW (up to 4,000 kW for short time), having 100 to 100,000 kWh power capacity, 150 to 200 W h/kg or 200 to 
250 W h/l specific power capacity and complete with all support systems both for marine and ground applications. These powerplants will satisfy your demand in high-quality electricity when you are cut off from atmospheric air supply and when you need a highly effective, small-size, low-noise, ecologically-friendly and low-heat-emitting powerplant.