Alternating Current AC Electricity Generation, Storage, and Power Usage

Question

With DC we have a stored potential difference (9v) for later usage (remote control). What about AC? AC electricity is generated from a power plant (hydro, fossil) by generators that create AC power for use in the home, but my confusion is "How is this power always readily available?"

Is there storage of this power?

Are the power plants producing just what we need 24/7?

What happens when the power is generated but there is no consumption?

Is the power generation and consumption just in time of each other or should it be viewed like a DC battery (created for future use)?

Thanks for your time.

Answer 1

There is no means to store energy in an AC circuit.  All generation and load must be in balance every cycle, or else the frequency changes.

This is true for the entire interconnected electric grid.  Each and every one of them!

Operation of the grid involves scheduling generators to be online with capacity available to pick up the load changes (such as turning on your lamp at home).

If power is generated without corresponding consumption, the grid frequency increases.  If frequency goes too high, equipment trips offline.  Small perturbations in frequency are normal, and are used as a control feedback mechanism to the mechanical input of the generators (i.e. steam valves on boilers, fuel valves on gas turbines, etc.)

Answer 2

Power plants produce just what we need 24/7. It is like driving a car. When a car goes faster or goes up a hill, the throttle opens, more fuel flows and more power is produced. When more electric power is used, the generators produce more power and the turbines driving the generators use fuel at a faster rate. Large turbines can't "open the throttle" as quickly as the throttle on a car engine opens, but millions of people don't suddenly start using more power at the same time. Since many power stations are connected together through the power grid, the total power demand is the sum of the demand of millions of people. In addition, there are some smaller "peak demand" generators that can be started and stopped or adjusted more quickly. Adjustments are made automatically by computers and electronic regulators.

Some hydroelectric stations provide storage by using electric power from the grid to pump water up to a high reservoir when the power is not being used by consumers.

The use of the term "power" actually means energy per hour. Using more power means to use more energy per hour. Power is the rate of flow of energy like gallons of oil per minute.

Answer 3

its a biggest confusion for all electrical engineers, but try to think like: when there is an outage(power cut) in your locality; you have two options, 1) if you have a battery big enough to run your appliances such as in Inverter battery of some 10 KW then what you use is stored power in the form of DC charge in the battery and the inverter inverts the dc current into AC current through SCRs(Thyristors).

and the second option is to go for direct AC generator(house hold Generator) on some 5 KVA.

Now, the power from the inverter is a STORED power and it runs as long as you have stored charge in your battery. but in case of the generator power is GENERATED continuously through electromechanical conversion, and the moment you switch it off or the  moment fuel is exhausted the power supply is gone.

OK... Now think of a BIG generator, the prime mover can be of Hydel or thermal or nuclear type, and a big network that acts as a infinite platform, having constant voltage, which recieves and delivers power from in numerous generators, this network is also known as a GRID.

So, the power we use 24/7 is being generated according to the demand of the GRID i.e. demand of people, industries etc.

Lastly, AC power can only be stored in capacitors and to deliver  such an amount of power the size of the capacitor would be enormous, but researches is going on is this regard.

thats all...

hope u have less doubts now :)