Scientists have developed a new inexpensive system for direct electrochemical extraction of energy from sea water, which can autonomously switch between two operating modes.
Submarine and equipment for functioning for a long time, an independent source of energy is required. In such conditions, the generators should not only maintain a stable stream of energy throughout the time of their work, but also ensure the supply of higher power with rapid motion, capture or other active actions. Chinese researchers have created a new generator, which is similar to marine organisms, can switch between aerobic and anaerobic regime using various materials as electrons acceptors.
The basis of the system is a cathode from Berlin Lazuri, an open frame structure with «racks» from cyanide ions and «nodes» from iron ions. In combination with a metallic anode, this structure can be used to produce electricity from sea water.
With low energy consumption, electrons entering the cathode are transferred directly to dissolved oxygen. Since in the sea water, its reserves are inexhaustible, then in this mode, the system theoretically can provide meals with a weak current throughout unlimited time.
During the growth of power consumed, dissolved oxygen becomes not enough to make all incoming electrons. Therefore, the Berlin Azure should store them, reducing the degree of oxidation of iron atoms with +3 to +2. To maintain the charge balance, positively charged sodium ions are settled in the frame. In seawater, a sufficient concentration of Na in order to absorb a large amount of electrons in a short time.
When reducing power consumption, electrons are again transferred to oxygen, which restores the framework, Fe2 + is oxidized to Fe3 +, and sodium ions are removed.
A new system is resistant to aggressive sea water and can cope with numerous switching modes. When the metal-organic structures are turned on, the theoretical density of the device’s energy is 3960 VTH / kg.
During the test of the prototype of the generator, in the energy mode, it worked continuously four days without loss of power. In the mode of high power, the energy was enough to power 39 LEDs and propellers.
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