Development and Experience of a Practical, Pressure-Tolerant, Lithium Battery for Underwater Use
For a number of years, lithium-ion batteries have promised energy and power densities that make them an attractive alternative to the silver-zinc batteries historically used in underwater vehicles. For AUV (Autonomous Underwater Vehicle) application, polymer-electrolyte cells offer the promise of pressure tolerance; this key attribute impacts vehicle design and operational logistics in a number of ways. Primarily, it facilitates the design of arbitrarily large battery packs by obviating many of the problems associated with large, heavy and expensive pressure vessels that would have been otherwise required to house batteries at depth. This allows a single AUV operator to recover the vehicle and remove and replace the batteries in minutes without the down time associated with servicing o-rings and seals. In a military context, this new operational paradigm has made back to back search and classify missions a practical reality. As with all new technologies there is a hiatus between availability, practical implementation and adoption. Many fundamental, logistical and practical engineering problems in design and manufacture have been solved in the past 5 years leading to a range of commercially available batteries with power densities exceeding 100Wh per neutrally buoyant Kg. This paper will explore these challenges, examining specific solutions derived from experience gained through the pressure testing of over 20,000 cells
Ocean 73. [Engineering the storage battery as an underwater power supply]
Engineering of the storage battery into an integrated oceanographic power system has been successfully accomplished. This is evidenced by the scores of systems in operation below the seas today. This accomplishment was made possible by the development of a sophisticated pressure compensation system and applying it to existing electrochemical couples. Comprehensive studies of lead-acid and silver zinc cell operating characteristics at temperatures as low as 30\deg F and pressures up to 10,000 psi have led to the use of these batteries in systems ranging from small underwater vehicles to mobile sea floor equipment to large stationary habitats. From laboratory evaluations, it was determined that the advantageous effect of elevated pressures on the performance of lead-acid batteries is offset by the deleterious effect of cold temperature. The net effect of these same environs on the silver zinc cell is a decrease of 10% in discharge performance.
Parboiled rice effluent: A wastewater niche for microalgae and cyanobacteria with growth coupled to comprehensive remediation and phosphorus biofertilization
Abstract The potential of microalgae and cyanobacteria for bioremediation of wastewater by nutrient uptake combined with simultaneous biomass production is a well recognized perception of today's world. The present study illustrates the treatment of a highly polluted wastewater generated during parboiling of paddy in rice mill industries, widely operational in developing countries where rice is the staple food crop, with the help of microalgal and cyanobacterial isolates capable of growing at high rates in parboiled rice mill effluent (RME). This endeavor leads to comprehensive bioremediation of the said effluent and subsequent use of the harvested biomass as slow release phosphorus biofertilizers and the treated effluent for crop irrigation. The RME-acclimatized algal consortium demonstrated highest growth in terms of fresh weight and greatest remediation efficiency at the end of 36 days' treatment of RME, with 93.9% phosphorus and 100% ammonia-nitrogen removal, 98.7%, 91.6% and 93.5% reduction in biological oxygen demand, chemical oxygen demand and total dissolved solid, respectively, and an increment of 186 ± 0.3 mg L − 1 dissolved oxygen, bringing down the pollutants level well below the discharge limits suggested by Central Pollution Control Board, India. Additionally, microalgae in the consortium aggregated in clumps spontaneously in presence of the filaments of Phormidium sp. facilitating easy harvest. The RME-acclimatized algal consortium demonstrated highest accumulation of polyphosphate (poly-P) (0.76 ± 0.01% of dry weight) as well as highest release of phosphorus in non-sterile soil emphasizing the essential role of soil phosphorus solubilizing organisms to leach soluble phosphorus from the insoluble poly-P present in the biomass. The rice seedlings watered with treated RME also showed improved growth effect on shoot height and leaf width. The study results establish the suitability of RME as an excellent growth media for microalgae and cyanobacteria.