Chemistry: electrical current producing apparatus – product – and – Deferred action type – Responsive to addition of liquid
Patent
1993-03-23
1995-04-11
Maples, John S.
Chemistry: electrical current producing apparatus, product, and
Deferred action type
Responsive to addition of liquid
429175, 429241, H01M 634
Patent
active
054057175
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to sea water cells or batteries which use oxygen dissolved in sea water as oxidants, as for instance cells described in international patent application Nos. PCT/N089/00040 and PCT/N090/00045.
BACKGROUND ART
The sea water cell described consists of an anode made from an electronegative alloy e.g. based on magnesium, zinc, aluminum or lithium, and the cathode is a more or less inert current conductor. Common materials in the cathodes are materials which are resistant to sea water, such as copper, stainless steel, titanium or carbon. The cathode may also be coated with a catalyst which catalyzes the reduction of oxygen. Sea water contains little oxygen, about 10 g/m.sup.3. As a result of this the oxygen reducing sea water cells must have a very open structure in order to allow sufficient flow of fresh sea water through the cathode. Batteries consist usually of cells which are connected in parallel because the cells have the seawater as a common electrolyte. The common electrolyte would give short circuit currents via the sea water in series connected batteries. A DC/DC converter converts the low voltage (1 to 2 V) of the sea water cell to a more useful value, as e.g. 28 V.
In a battery having magnesium anodes the following reaction will take place: positive electrode (the cathode):
The concentration of oxygen in sea water is low, so that the transport of oxygen to the surface of the cathode will be the reaction step limiting the performance of the battery. Further one has to ensure that the surface of the electrode does not become so alkaline that it leads to deposition of calcium carbonate from the sea water, as this may form a layer on the cathode. Such a layer will, if it is formed, lead to a permanent reduction of the performance of the battery. For this reason the alkalization must be limited. This is obtained by limiting the current so that it does not exceed a certain percentage of the limiting current of the cathode. The limiting current is the current density at which the concentration of oxygen at the surface of the electrode is zero, in other words where the current density is so high that any oxygen molecule which is transported to the electrode surface by diffusion or convection, is reduced by formation of hydroxyl ions. The cathode is therefore given such a structure that a highest possible limiting current is obtained. A different parameter which is often used in literature is the so called mass transfer coefficient, k.sub.m, which in this case is the limiting current density divided by the oxygen concentration.
The limiting current density increases with increased water velocity, oxygen concentration and temperature and decreases with increased size of the cathode element. It has been found to be advantageous to make the cathode from expanded metal, net or metal wool because this can limit the size of the cathode in the flow direction of the sea water. The cathode can also be designed so that there is little resistance against flow-through, so that the sea water within the cathode is renewed continuously. These problems and solutions are described in int. pat. appl. PCT/N090/00045.
DESCRIPTION OF INVENTION
The object of the present invention is to increase the efficiency of sea water cells of the above mentioned type. The main features of the invention are defined in the following patent claims. The invention makes use of the vertical movement of the sea water cell to increase the water flow through the cathode and thereby the maximum current delivered by the cell.
BRIEF DESCRIPTION OF DRAWINGS
Above mentioned and other features and objects of the present invention will clearly appear from the following detailed description of embodiments of the invention taken in conjunction with the drawings, where
FIG. 1 shows a sketch of a sea water cell,
FIG. 2 shows the principle of the invention,
FIG. 3 shows a light buoy
FIG. 4 shows the embodiment of a cell which is suspended in accordance with the invention, and
FIG. 5 shows an anode structure.
REFERENCES:
patent: 2721342 (1955-10-01), Pickren
patent: 3401063 (1968-09-01), Opitz
patent: 3497393 (1970-02-01), Dreisbach et al.
patent: 3542599 (1970-11-01), Fiandt
patent: 3907596 (1975-09-01), Ketler
patent: 4601961 (1986-07-01), McCartney
patent: 4822698 (1989-04-01), Jackovitz et al.
Forsvarets Forskningsinstitutt
Maples John S.
LandOfFree
Seawater cell with increased efficiency does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Seawater cell with increased efficiency, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Seawater cell with increased efficiency will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-1537501