Short-circuiting cells

The photogenerated current is in the same direction as /, but is always less than because the battier potential under load conditions is always less than F, which results in a larger flow of majority carriers than that in a short-circuited cell. Thus, when a solar cell is under load, the current and voltage are always less than and lU, respectively this condition is the curve-factor loss. Depending on the characteristics of the particularp—n junction and on the cell operating conditions, there is an optimal load resistance that maximizes the power output of the cell, ie, the product of its current and voltage. 

A typical distribution is portrayed in Table 11 for a configuration of fifty cells arranged in five ten-cell banks, where for the sake of safety, a short-circuited cell will disconnect an entire bank. This arrangement is essentially identical to a five-cell bank with single short-circuits. The more efficient (i.e., the faster) the repair service (i.e., the smaller X/p), the smaller the probability that short-circuited cells are not repaired at any arbitrary time. Conversely, if repair takes a long time, a certain number of cells will always be short-circuited, and if kip is extremely large, a complete shutdown of cell operation will be highly probable (the Xlp = 10, ps 0.9 case is a case in point, albeit not overly realistic.)... 

Figure 10-30(a) applies to an open circuit cell in the dark Fig. 10-30(b) applies to a short circuit cell in the dark. After the cell circuit is closed in the dark, the Fermi level is equilibrated between the two electrodes thereby forming a space charge layer both in the n-tyi>e anode and in the p-type cathode. The overall potential, AE, generated in the two space charge layers nearly equals the difference of the flat band potential between the n-type anode and the p-type cathode as eiqpressed in Eqn. 10-57 ... 

This description of the photoelectrochemical event was originally based on the use of an illuminated semiconductor electrode in a standard three electrode cell configuration. The theory can easily be extended, however, for practical applications to short-circuited cells prepared by deposition of inert metal with low overvoltage characteristics on a powdered semiconductor Such a metallized powder is shown in... 

The total amount of energy a reaction can supply under standard conditions at constant pressure and temperature is given by AH0. If the reaction takes place by combining the reactants directly (no cell) or in a short-circuited cell, no work is done and the heat released is AH. If the reaction takes place in a cell that performs electrical work, then the heat released is diminished by the amount of electrical work done. In the limit of reversible operation, the heat released becomes... 

At level flow (If), analogous to a short-circuited cell, the phosphate potential vanishes. Hence, no net work is performed by the mitochondria, and we have... 

The mode of attack on metals described above is referred to as the hydrogen evolution type of corrosion, since gas is actually evolved at the more noble portion of the system. This type of corrosion requires a combination of two metals, the nobler one of w4iich has a low overvoltage, but it is not necessary that the metals should be in a massive form. For example, the addition of a small quantity of copper sulfate to an acid solution greatly expedites the rate at w hich zinc dissolves copper is deposited, by replacement, on various parts of the zinc and a large number of local short-circuited cells are set up. Another possibility, which frequently arise., is that the base metal should have in-... 

The advantage of the currentless oxydation consists in the complete regeneration of the etchant. The re-oxydation of the CU2CI2 can be performed by inserting oxygen directly into the solution or by oxydation at electrocatalyzed 02-fed electrodes in a short circuited cell. The latter methode prevents the formation of aerosols from gas bubbling. 

Figure 1 Externally Short Circuited Cells and Dual Phase Membranes...

Table 7 Current Density, Syngas Yields in Short Circuit Cells. 

Decomposer reaction (essentially a short circuited cell)... 

Separator shutdown is a useful and essential mechanism for limiting tanperature and preventing venting in short-circuited cells. It usually takes place close to the melting temperature of the polymer when the pores collapse, turning the porous ionically... 

Electrolytic cells that account for the corrosion of metals are analogous to the short-circuited cell. The measured potential of a corroding metal, the mixed potential of both polarized anodes and cathodes, is also referred to as the corrosion potential, ( )corr- The value, /max, is known as the corrosion current, /con- By Faraday s law, the corrosion rate of anodic areas on a metal surface is proportional to /corr, and hence the corrosion rate per unit area can always be expressed as a current density. For zinc, a corrosion rate of 1 gmd is equivalent to 0.0342 A/ m. For Fe corroding to Fe +, the corresponding value is 0.0400 A/m. Values for other metals are listed in the Appendix (Section 29.8.2). 

The amalgam leaves the cells, which are sloped to permit gravity flow. Each mercury cell has a companion denuder or decomposer. This is a short-circuited cell, usually packed with graphite, in which amalgam decomposition in the presence of added water regenerates the mercury and forms caustic soda or potash ... 

FIG. 5—Profiles of electrode potential, referred to the rest potential of zinc, at the surface of a rod shaped zinc platinum/ zinc short-circuited cell in acidic chloride media. The dashed lines represent platinum electrodes of varying length [9]. 

Current density of cell at short circuit Cell potential difference at maximum power Maximum power density... 

Intercetl Connections. In a series-arranged battery of pile constraction, the anode of one cell is connected to the cathode of the adjacent cell. To accomplish this without producing a short-circuited cell, an insulating tape or film is placed between the electrodes on nonsilver batteries. For silver batteries silver foil is used alone or in conjunction with an insulating tape. 

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