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a device to accumulate energy for its subsequent utilization. Depending on the type of energy being accumulated, the following accumulators are used: electric, hydraulic, thermal, and inertial.
Electric accumulators—storage batteries—accumulate electrical energy by converting it into chemical energy, with a reverse conversion as required. They can be used repeatedly, their operational readiness being reestablished by means of a charge—that is, by running current through them in the direction opposite to the direction of the current during discharge. The first experiments in the building of an electrical accumulator were performed at the beginning of the 19th century by V. V. Petrov and J. Ritter. Especially significant contributions in the study of properties, development, and perfection of the design of storage batteries were made by the Russian scientists E. Kh. Lents, D. A. Lachinov, E. P. Tveritinov, N. N. Benardos, P. N. Iab-lochkov, M. P. Avenarius, the English physicist W. Grove, the Frenchman G. Plante, and many others (some 20,000 patents were registered until 1937 on the subject of lead accumulators throughout the world). In 1900, T. A. Edison invented a storage battery of the alkaline type which has been widely used. An electrical accumulator consists of two electrodes immersed in an electrolyte solution. The difference in the potential of the electrodes is the storage battery emf. The conversion of chemical energy into electrical energy in a closed circuit is based on a chemical (current-generating) reaction. The most widely used electrical accumulators, in terms of their electrochemical arrangement, are divided into lead (acid), cadmium-nickel, iron-nickel (alkaline), silver-zinc, and silver-cadmium (see Table 1).
A storage battery is characterized by its service life (the number of charge-discharge cycles obtainable without a significant decrease of its characteristics); its electrical charge (the term “capacity” is widely used), the amount of electricity in coulombs (C), kilocoulombs (kC), or ampere-hours (A-hr) which it is capable of delivering upon discharge; average voltage in volts during charge and discharge; the specific energy in joules, kilojoules, or watt-hours available during the discharge of 1 kg of mass or 1 cubic decimeter of volume; and the energy delivery or efficiency (1 ampere-hour = 3,600 C; 1 watt-hour = 3,600 joules).
The area of application of Group I accumulators is in motor vehicles, aviation, and communications: for example, accumulator starter batteries of the 6ST-68EMS or 6TST-120EMS type and stationary storage batteries of the SN-1 and SN-3 type and others of closed construction, which are used in electric power stations and central stations for telegraph and telephone. Storage batteries of Group II are used in aviation, communications equipment, electrically powered vehicles, satellite equipment, and portable apparatus. For example, power storage batteries TNZh-300VM are used in electrical lift and stack trucks; sealed cadmium-nickel batteries of the KNGM-10D type in mining lamps; KNG-1D in prosthetic devices with bioelectric control; and KNGTs-3D and disk batteries and storage batteries of types D-0.06, D-0.1, D-0.25. and 7D-0.1 in supplying miniature radio receivers, flashlights, hearing aids, photoflashes, and the like. Storage batteries of Groups III and IV are used in aviation, communications equipment, motion picture cameras, and so on.
Hydraulic accumulators serve for the equalization of pressure or flow of fluid or gas in hydraulic devices. There are load accumulators and air accumulators with and without pistons. Hydraulic accumulators are utilized in systems with rapidly changing fluid or gas flow. During periods of decreased requirements the accumulator accumulates fluid (gas) entering from the pumps (compressors) and supplies it during bursts of high demand. The accumulator consists of a reservoir, usually cylindrical in shape, with a freely moving piston inside. Fluid under pressure is pumped into the reservoir, which is maintained at constant pressure as a result of the external influence upon the piston of a load or of air from a pneumatic system connected to it. In accumulators without a piston, constant pressure is maintained by the pressure of the pneumatic system connected directly to the reservoir of the accumulator, where the air pressure is equal to the fluid pressure. A pneumatic accumulator, a variant of the hydraulic accumulator, is utilized to decrease pressure fluctuations of the compressed air as desired in the pneumatic system. Pneumatic accumulators are used in large pneumatic systems, wind-driven electrical power stations, and so on. They consist of a reservoir connected to the air lines and fitted with a safety valve. The valve is set to a predetermined limiting pressure.
A thermal accumulator is used to store thermal energy for the purpose of equalizing thermal and power loads and for the prevention of interruptions in steam supply and energy supply in industrial installations.
An inertial accumulator is a moving body which has momentum content significantly exceeding the momentum of external forces acting upon this body. The most frequently used inertial accumulator is a rotating flywheel (for example, the inertial drive widely utilized in children’s toys).
|Table 1. Basic types of electrical accumulators|
|Storage battery type||Group||Electrochemical system||Discharge potential(V)||Maximum electric current density||Specific energy||Service life (cycles )|
|Lead (acid) ...............||I||(+) PbOa H2S04)Pb (-)||2.0–1.8||1,000||100||35–110||10–30||200–500|
|Cadmium-nickel and iron-nickel (alkaline) .....||II||(+) NiOOH(KOH)Cd (-)||1.3–1.0||500–2,000||50–200||70–125||20–35||1,000–3,000|
|(+) NiOOH(KOH)Fe (-)||1.3–1.0||500||50||90–126||25–35|
|Silver-zinc ................||III||(+) Ag20 (KOH)Zn (-)||1.5–1.3||1,000–2,000||100–200||360–430||100–120||20–100|
|Silver-cadmium ............||IV||(+) Ag20(KOH)Cd (— 1)||1.1–0.9||300–500||30–50||215–250||60–70||50–500|
REFERENCESTerent’ev, B. P. Elektropitanie radioustroistv, 2nd ed. Moscow, 1958.
Vinal, G. W. Akkumuliatornye batarei, 4th ed. Moscow-Leningrad, 1960. (Translated from English.)
Bagotskii, V. S., and V. N. Flerov. Noveishie dostizheniia v oblasti khimicheskich istochnikov toka. Moscow-Leningrad, 1963.
ii. A device sometimes incorporated into the fuel system of a gas turbine engine to store and release fuel under pressure as an aid in starting. Also called a collector.
iii. A device for storing fuel in a fuel tank for inverted flying.
iv. In pneumatic and oxygen systems, the reservoir where compressed air or oxygen is stored.
v. An electrical storage battery that can be recharged.
The canonical example is summing a list of numbers. The accumulator is set to zero initially, each number in turn is added to the value in the accumulator and only when all numbers have been added is the result written to main memory.
Modern CPUs usually have many registers, all or many of which can be used as accumulators. For this reason, the term "accumulator" is somewhat archaic. Use of it as a synonym for "register" is a fairly reliable indication that the user has been around for quite a while and/or that the architecture under discussion is quite old. The term in full is almost never used of microprocessor registers, for example, though symbolic names for arithmetic registers beginning in "A" derive from historical use of the term "accumulator" (and not, actually, from "arithmetic"). Confusingly, though, an "A" register name prefix may also stand for "address", as for example on the Motorola 680x0 family.
2. <programming> A register, memory location or variable being used for arithmetic or logic (as opposed to addressing or a loop index), especially one being used to accumulate a sum or count of many items. This use is in context of a particular routine or stretch of code. "The FOOBAZ routine uses A3 as an accumulator."