I need some info on types of powers used in buildings.1. make a list of the buildings where you think an emergency generator is essential. 2. Here...

The supplementary information give with the question includes request for completing activities which perhaps a student is required to carry out in his or her locality. The second paragraph identifies three different sources of power supply for buildings - Hydroelectric, coal based power station, and local generators for each building. And the third paragraph asks for advantages and disadvantages  of each. In my answer I will discuss this last point, the advantages and disadvantages of different sources of power supply for a building.

We can identify tho main source of power supply for a building. One is to purchase power from a power utility, and the other is to generate power independently for the building using a small generator set. The power utility may generate its power from different sources like hydro, coal, gas, or nuclear power. This original source of power for the power utility makes no difference for the building. So we need to compare just the advantages and disadvantages of buying power from a utility versus generating power using small generating set. These are discussed below.

The biggest advantage of buying power from a utility is that, because they generate power in bulk, and they are expert in this business, the power supplied by them is usually economical. In addition, the quality of power in terns of stability of frequency and voltage is better.

The reliability of utility power is also higher. In case of separate generator installed in a building breaks down, building has no alternate source of power. However the power utility have enough stand by capacity to make up ensure uninterrupted supply in spite of break downs in some of the plants.

The generators installed in buildings create noise pollution and storage and handling of fuel can be a messy affairs.

The self generated electricity option is worth while only in cases the supply from power utility is very erratic, or is not available at all due to remote location of the building.

Usually in most situation the best alternative may be to buy power from a power utility, and also install a small standby generator to supply electricity only for some essential services in case of failure of utility power supply.