The dif­fer­ence be­tween elec­tri­cal en­ergy and elec­tri­cal ca­pac­ity

Financial Mirror (Cyprus) - - OPINION - By An­dreas Poul­likkas

Elec­tri­cal ca­pac­ity, which is mea­sured in kilo­watts (kW) and elec­tri­cal en­ergy, which is mea­sured in kilo­watt hours (kWh), are very i mpor­tant con­cepts for un­der­stand­ing elec­tric­ity mar­kets and how elec­tric­ity tar­iffs are cal­cu­lated.

To make things eas­ier, think of a car in which the speedome­ter mea­sures the pace of the trip (or speed) in kilo­me­ters per hour and the odome­ter mea­sur­ing the to­tal kilo­me­ters. In this case, the car’s speed is pro­por­tional to the elec­tri­cal ca­pac­ity and the to­tal kilo­me­ters are the amount trav­elled be­ing pro­por­tional to the to­tal con­sump­tion of elec­tri­cal en­ergy (elec­tric­ity).

For a bet­ter un­der­stand­ing we can com­pare an elec­tri­cal sys­tem with an ir­ri­ga­tion sys­tem con­sist­ing of pumps (elec­tric gen­er­a­tors) and wa­ter pipes (elec­tric­ity lines or ca­bles).

The ir­ri­ga­tion sys­tem serves a large num­ber of plants (con­sumers) where daily wa­ter­ing is re­quired with a cer­tain amount of wa­ter for each sep­a­rate plant at ran­dom time pe­ri­ods. The process be­gins in the morn­ing with the wa­ter­ing of the first plant by open­ing the spe­cific valve (switch), the pumps start gen­er­at­ing wa­ter flow (elec­tri­cal ca­pac­ity) so that a suf­fi­cient amount of wa­ter (elec­tric­ity) reaches the plant.

When a sec­ond plant needs wa­ter­ing at the same time, then the valve opens so that the pumps in­crease the flow of wa­ter (if nec­es­sary, an ex­tra pump will be put in op­er­a­tion) to be able to sat­isfy the to­tal amount of wa­ter for wa­ter­ing both plants.

Dur­ing the en­tire day, the pumps will reg­u­late the flow of wa­ter in the ir­ri­ga­tion sys­tem so that the re­quired amount of wa­ter is pumped so that the plants will be wa­tered.

Of course, there should be enough pumps to pro­vide wa­ter even at the most busy and de­mand­ing hour (max­i­mum de­mand).

That is, they should be able to cre­ate the max­i­mum flow of wa­ter in the event that all the valves to the plants are open so that there is a seam­lessly sat­is­fac­tory amount of wa­ter in all plants.

Since each plant’s valve opens and closes at ran­dom hours (e.g., by mea­sur­ing the mois­ture in the soil around the plant) then this sce­nario is re­mote (it may hap­pen 1 or 2 times a year) how­ever, de­mand must be sat­is­fied, oth­er­wise some of the plants will not have avail­able wa­ter and will wither (re­li­a­bil­ity of the elec­tri­cal sys­tem).

This, of course, would re­quire the in­stal­la­tion of many pumps (which en­tails a high cost), some of which will not be used through­out the year.

In ad­di­tion, back-up pumps (aux­il­iary ser­vice) have to be in­stalled in the sys­tem so as to sat­isfy the wa­ter de­mand in the event that some of the other pumps should fail.

If ad­di­tional plants are added to the sys­tem, then ad­di­tional pumps should be added to en­sure seam­less sup­ply of wa­ter to the plants.

In all cases, the own­ers of the plants (con­sumers) will have to pay the sup­plier (elec­tric­ity com­pany): (a) for the to­tal amount of wa­ter (elec­tric­ity - kilo­watt-hours), (b) an amount in re­gards to the level of wa­ter flow (elec­tri­cal ca­pac­ity- kilo­watt) needed to wa­ter their plants, in such a way that cov­ers the cap­i­tal ex­pen­di­ture for ex­tra pumps needed to meet the max­i­mum de­mand and (c) an ad­di­tional amount to cover the cost for spare pumps (aux­il­iary ser­vices).

Fi­nally, in math­e­mat­i­cal terms, elec­tri­cal ca­pac­ity is the pace with which the elec­tri­cal en­ergy is used (or elec­tric­ity flow) and elec­tri­cal en­ergy is the time in­te­gral of elec­tri­cal ca­pac­ity. Dr. An­dreas Poul­likkas is Pres­i­dent of the Cyprus En­ergy Reg­u­la­tory Author­ity (CERA)

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