Answer:

1) The first known use of fuel was the combustion of wood or sticks by Homo erectus nearly two million years ago. Throughout most of human history only fuels derived from plants or animal fat were used by humans. Because fossil fuels are being used at large scale and they are non renewable sources of energy, they will disappear after some time. After the depletion of non renewable sources of energy we will be left with nothing, hence we are trying to develop alternate sources of energy.

2) Hydroelectricity, or hydroelectric power, is electricity produced from hydropower. In 2015, hydropower generated 16.6% of the world's total electricity and 70% of all renewable electricity, and was expected to increase by about 3.1% each year for the next 25 years.

3) Reduce your carbon footprint: Green, renewable sources of energy don't release carbon dioxide or other harmful pollutants into the atmosphere. According to the Energy Saving Trust's Solar panels page, a typical solar PV system could save around 1.5 - 2 tonnes of carbon per year.