batteries - Uma visão geral
batteries - Uma visão geral
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They are available in a variety of sizes, from very small button cells for hearing aids to the large batteries used in film cameras.
Primary batteries readily available to consumers range from tiny button cells used for electric watches, to the Pelo. 6 cell used for signal circuits or other long duration applications.
A voltaic pile can be made from two coins (such as a nickel and a penny) and a piece of paper towel dipped in salt water. Such a pile generates a very low voltage but, when many are stacked in series, they can replace normal batteries for a short time.[28]
Batteries and similar devices accept, store, and release electricity on demand. Batteries use chemistry, in the form of chemical potential, to store energy, just like many other everyday energy sources. For example, logs and oxygen both store energy in their chemical bonds until burning converts some of that chemical energy to heat. Gasoline and oxygen mixtures have stored chemical potential energy until it is converted to mechanical energy in a car engine. Similarly, for batteries to work, electricity must be converted into a chemical potential form before it can be readily stored. Batteries consist of two electrical terminals called the cathode and the anode, separated by a chemical material called an electrolyte. To accept and release energy, a battery is coupled to an external circuit.
The fundamental relationship of electrochemical cell operation, put forth by the English physicist-chemist Michael Faraday in 1834, is that for every ampere that flows for a period of time, a matching chemical reaction or other change must take place. The extent of such changes is dependent on the molecular and electronic structure of the elements constituting the battery electrodes and electrolyte. Secondary changes may also occur, but a primary pair of theoretically reversible reactions must take place at the electrodes for electricity to be produced. The actual energy generated by a battery is measured by the number of amperes produced × the unit of time × the average voltage over that time.
Primary batteries are designed to be used until exhausted of energy then discarded. Their chemical reactions are generally not reversible, so they cannot be recharged. When the supply of reactants in the battery is exhausted, the battery stops producing current and is useless.[29]
It can be used for high- and low-drain devices but can wear out quickly in high-drain devices such as digital cameras. These batteries have a higher energy density and longer life, yet provide similar voltages as zinc-carbon batteries.
Batteries come in many shapes and sizes, from акумулатори miniature cells used to power hearing aids and wristwatches to, at the largest extreme, huge battery banks the size of rooms that provide standby or emergency power for telephone exchanges and computer data centers.
The C-rate is a measure of the rate at which a battery is being charged or discharged. It is defined as the current through the battery divided by the theoretical current draw under which the battery would deliver its nominal rated capacity in one hour.[51] It has the units h−1. Because of internal resistance loss and the chemical processes inside the cells, a battery rarely delivers nameplate rated capacity in only one hour. Typically, maximum capacity is found at a low C-rate, and charging or discharging at a higher C-rate reduces the usable life and capacity of a battery.
New methods of reuse, such as echelon use of partly-used batteries, add to the overall utility of electric batteries, reduce energy storage costs, and also reduce pollution/emission impacts due to longer lives.
Vanadium-Redox Flow: These batteries integrate energy from renewable resources, such as solar and wind farms. For years, sensitivity to high temperature, high cost, and smaller storage capacity limited the widespread use of these batteries. PNNL researchers developed a new generation of vanadium flow battery with a significantly improved energy density and wider temperature window for operation, that is capable of deployment at grid scale.
These types of batteries remain active until the power runs out, usually about three years. Benefits of this battery include flat discharge voltage, safety environmental benefits, and low cost.
The battery's cathode slowly disintegrates, and forms molecules called polysulfides that dissolve into the battery's electrolyte liquid. PNNL researchers have developed solutions to protect the anode and stabilize the cathode, and we're working to bring them to real-world applications.
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