Why most of the equipment in domestic as well as industrial use to run on AC power
Answers
Answer:
Because in nineteenth century when AC systems started to grow rapidly, we lacked power electronics technology and also did not have strong focus on renewable energy and energy storage system.
We did not have power electronics technology. This means voltage step up and step down were downright impossible for dc systems. This is the main point why ac became so popular. It is very important to transmit the generated power in very high voltage and distribute it at lower voltage which requires voltage step up and down.
Another important point is voltage regulation. If ac voltage drops due to the line resistance it is very easy to bring it back to the original value just by using capacitors. We do not need any active energy source. However, in DC systems the drop in voltage must be supported by an active dc source and power electronics.
Third point is circuit breakers. As we know that AC has zero crossings so it is very easy to break a circuit at zero current. However a pure dc does not have any zero crossing. So it is extremely difficult to design a circuit breaker for a dc system.
Another very crucial point is Induction motors. They run on ac, very robust, long life, workhorse of the industry. Made the ac systems look more attractive.
This is why we built ac grids, ac loads, ac generation systems, and ac domestic line even if the dc systems have the following advantages. Transmission is efficient and reliable for long distance (look for High-voltage direct current). No pain of reactive power. Power factor is always unity. No Skin effect. Hence reduced copper cost. These are all good points of dc.
Now consider the current scenario. We are shifting from fossil fuel to renewable energy which are nothing but dc (wind is ac but it must be converted to dc to use it). Energy storages (these are also dc) are being heavily researched (see what Elon Musk is doing). Most importantly we have power electronics which can convert any form of electricity to any form of electricity.
Now we can step up or step down dc. We do not have to depend on centralized generation. Thanks to renewable energies like solar PV, distributed generation is possible. Hence, active dc energy source can easily be put to adress the voltage drop issue. Due to the immense research in power electronics dc circuit breakers have started to become popular. Even if induction motors are still popular we are using a variable frequency drive to operate them which needs a dc supply. The high efficiency BLDC motors and low cost Switched Reluctance Motors have started to evolve which are more efficient than Induction motors. Moreover, all the energy storage devices like batteries or supercapacitors are dc.
Do you see where I am going? The feasibility of a dc supply in our houses. Believe me, it has already been implemented in some places in the form of DC Micro grid. The interconnection of two different grids (ac and dc) is also possible. AC loads can be connected to a dc supply with an inverter. Thanks to the recent development in power semiconductor technology prices are going down rapidly.
Recent studies have shown that direct-current (DC) microgrid interface can result in significantly simpler control structure, more energy efficient distribution and higher current carrying capacity for the same line ratings.
We still have ac in our houses. But, according to me, the dusk of fossil fuels and the dawn of renewable energies may lead to a future where we will have either only dc or a hybrid of ac and dc in our houses.