Harnessing Hydropower To Boost Clean Energy Resources

Energy needs in industrial, transport, agricultural and domestic sectors are being met mainly from fossil fuels. Presently, about 74% of energy being utilised is obtained from fossil fuels and the rest from renewable energy sources like hydropower, solar, wind and bioproducts.

The most important advantage of using renewable energy resources is to avoid the emission of greenhouse gases like carbon dioxide, oxides of nitrogen and sulphur and particulate matter to the atmosphere. These greenhouse gases are responsible for global warming and climate change, which have brought a lot of disasters to human beings and other living beings on the earth. Out of all renewable energy sources, hydropower is the most important.

For long, the construction of dams in rivers and streams and other water bodies to reserve water has been an integral part of human civilisation, as these control floods, providing water for drinking and agricultural purposes and generating hydropower. 

The water stored in the dam at suitable sites of the river is allowed to fall from a certain height on turbines and in this process, the energy present in water is converted into mechanical energy and subsequently to electrical energy by putting a generator along with the turbine. In this process, no water is lost. The water going out of the system is used for agricultural, industrial and domestic purposes. Similarly, by storing rainwater at suitable land sites, it is also possible to harness energy as and when required. In this way, the potential energy stored in water is converted to electrical energy without the loss of any water as shown below.  

Some of the advantages of hydroelectric power plants are:

• The supply of electric power can be maintained constantly.
• Water can be stored and used when electricity demand is high.
• The longevity of dams is quite long which helps to generate electricity at a low cost.
• Hydroelectric power is renewable and eco friendly.
• The dam area can be converted into a tourist attraction spot. 

However, there are certain disadvantages of hydropower plants particularly when water stored is quite large as given below.

• The construction of big dams is quite expensive and it has to be constantly maintained.
• From time to time, the desilting of dams has to be done.
• The rehabilitation problems of the people in the area are quite delicate and expensive.
• The dam has to be operated for many years as the return on the cost invested for the construction of the dam is obtained after a long time.
• Sometimes, the dam blocks the river water resulting in an irregular supply of water downstream.

In addition to this, in recent years, the construction of large dams has been avoided because of the following reasons.

• Alteration of water quantity and quality occurs in downstream areas.
• Water quality and bio-diversity are very much affected by increased erosion and sedimentation due to deforestation of the catchment areas.
• Large reservoirs produce a significant amount of greenhouse gases like carbon dioxide, methane etc.
• Many times benefits of large dams are not enjoyed by local communities or displaced families.

In view of these problems, in recent years, small hydropower plants are being encouraged. Some of the advantages of small hydropower plants are:

• The socio-economic impact is very little in comparison to large hydropower plants.
• In a micro dam, investment is low, durable and sometimes it can last for 50 years or more without much investment.
• It is considered to be cost-effective.
• The maintenance cost is quite low.
• If small hydropower produces excess electricity, some power companies can buy the same.
• It is possible to supplement small hydropower with intake from the power grid.

There are mainly four types of hydropower:

1. Run-off-river hydropower: 

In this case, the flowing water from a river is allowed through a narrow canal or penstock to spin the turbine, which is connected to a generator to produce electricity. The run-off-river system provides a continuous supply of electricity with some fluctuation depending on the water flow. 

2. Storage hydropower: 

In this case, water is stored in a reservoir with the help of a dam. When water is released from the reservoir, the turbine rotates and the connected generator produces electricity. This type of hydropower system provides base load as well as the ability to shut down and startup at short notice according to the demand. This system because of enough storage capacity operates independently of hydrological inflow.

3. Pumped storage hydropower: 

In this system, water is pumped from a lower reservoir to an upper reservoir. The water is released back to the lower reservoir through a turbine which is attached to the generator to produce electricity.

4. Off-Shore hydropower: 

In this case, the tidal current of the waves of the sea rotates the turbine which is connected to a generator to produce electricity. However, this technology has to be fully developed.

At present in the world, electric generation from hydropower, solar, wind and biofuel is 16%, 2%, 4% and3% respectively of the total electricity produced and the rest are from fossil fuels. In 2009, 16.5% of electricity produced in the world was contributed by hydropower.

According to World Energy Council 2010 report, about 160 countries have hydropower. However, the production of hydropower in the top ten countries accounts for about 70% of the hydropower electricity produced in the world as given in Table – 1.

Table – 1

Hydro Electricity Production and share of the world, total electricity production in top ten countries and the rest of the world in 2010, adapted from World Energy Council

Hydropower contributes approximately 62.10% of the total electricity produced by renewable energy sources. At present, the world’s installed capacity of hydropower is 1292 GW. It is hoped that, because hydropower is predictable and has high efficiency with flexibility and reliability, many more hydropower units should come up in future. International Energy Association predicted that hydropower would continue to become the main renewable energy source in future years

Large hydropower is associated with a number of problems like displacement of people, submergence of land in the catchment area, risk of dam malfunctioning, damage to ecosystem etc.

In view of this, nowadays small hydropower units are being preferred. It is reported that by utilising hydropower for electric generation in place of the amount of coal used at present, it is possible to prevent the release of about 148 million tons of particulate matter, 62 million tons of sulphur dioxide and 8 million tons of nitrogen oxide to the atmosphere every year.

In view of this and considering a number of merits of small hydropower, it is suggested that more efforts should be made to set up large numbers of small hydropower units to meet our increasing demands of electricity while keeping our environment clean and healthy.