Hydro Power: A Sustainable Clean Source of Energy

As the world is gripped in by climate change, mankind for its survival is thriving towards greener and cleaner solutions to almost everything in use to human life. In this quest for cleaner source of energy, hydro power has secured one of the top spots and has been a widely used source of power since 19^th century. Green, clean and renewable sources of energy are being increasingly used to generate electricity to meet the ever-increasing demand of power and to phase out the use of fossil fuel sources such as coal and gas which are key causes of climate change. 

Green energy is energy that can be produced using a method, and from a source, that causes no harm to the natural environment. Renewable energy comes from sources that are constantly and naturally renewed and are thus sustainable. Hence major sources of green, renewable and sustainable energy are solar, wind, hydroelectric including tidal energy, geothermal, bioenergy. Amongst the above, hydroelectricity is the most commercially developed source. 

Electricity is one of the most important aspects for the economy of any country. Demand for electricity is set to increase further with the increase of household incomes, shift to electric means of transport and heat and growing demand of digital devices and air conditioning. Unabated fossil fuels currently account for over 60% of total global electricity generation. To be consistent with the Net Zero Scenario, that share needs to drop rapidly to below 30% by 2030. The pace of deployment of low and zero-emission sources must pick up significantly in order to meet this milestone. 

In India, as per Government data currently fossil fuel such as coal, gas, diesel etc. accounts for about 57% of total electricity generation of which 49% is dominated by coal alone. On the other hand, non-fossil fuel accounts for 43% of which solar, wind and other renewable sources (excluding hydro) has a lion share of 30%. As per latest Government data India now stands committed to achieve about 50% cumulative electric power installed capacity through non-fossil fuel sources by 2030. India stands 4^th globally in Renewable energy installed capacity, 4^th in Wind Power capacity and 4^th in Solar Power capacity.

Hydroelectric Power – As a Clean Source:

A. Role of Hydro: There is a paradigm change in Power System operation at present with the large-scale variable of Renewable Energy in an effort to achieve net zero emission. The variability of Renewable resources due to characteristic weather fluctuation introduces uncertainty in generation output and need adoption of grid scale energy storage technologies to compliment these renewable resources.

Hence in such a scenario hydro can not only act as a clean source of power but can be a complimentary source to other renewable sources for stabilization of the grid. Pumped storage hydro power plants are becoming most preferred storage technologies in the present Power System operation. Therefore, with most of the countries pushing for Solar and Wind Power as a primary source also have trust on the importance of development of hydro specially pumped storage as the balancing source of power for a stable grid in the process of clean energy transition.

• B. Advantages of Hydro-Electric Power: The energy potential of hydropower is enormous. Indeed, the gigantic masses of water found at high altitudes are endowed with a considerable amount of gravitational potential energy, and harnessing even a portion of it means having plenty of energy at disposal. Suffice to say that all the World's largest power generation plants are hydroelectric, and it can take only one plant to meet the energy needs of millions of people. Below are some of the advantages of hydropower as India commits to generation of 500GW from non-fossil fuel based sources by 2030 and decarbonization by 2070 at the COP26, the UN Climate Change Conference:
• i. Hydropower is a renewable source of energy: The energy generated through hydropower relies on the water cycle, which is driven by the sun, making it renewable.
• ii. Hydropower is fuelled by water wherein electricity is generated without emitting greenhouse gases or other pollutants, making it a clean source of energy that mitigates climate change.
• iii. Hydroelectric power is a domestic source of energy, allowing each country to produce its own energy in a sustainable way without being reliant on international fuel sources.
• iv. Impoundment hydropower creates reservoirs that offer recreational opportunities such as fishing, swimming, boating and other water sports. Most hydropower installations are required to provide some public access to the reservoir to allow the public to take advantage of these opportunities thus helping in the development of tourism of the area where it is located. 
• v. Hydropower provides benefits beyond electricity generation by providing flood control, irrigation support, and clean drinking water. The amount of water that is released from a hydro power plant can be controlled over time and with great precision both in terms of flow rate and total volume thus regulating the flow of the river over which it is located
• vi. Hydropower is affordable. Although the initial investment in setting up a hydro plant is both challenging and costly, it provides low-cost electricity and durability over time compared to other sources of energy. 
• vii. Hydropower compliments other renewable energy sources. Technologies like pumpedstorage hydropower (PSH) store energy to use in tandem with renewables such as wind and solar power when demand is high.
• viii. Hydropower creates jobs in rural locations and boosts local economies.

ix. Hydroelectric power is flexible. Some hydropower facilities can quickly go from zero power to maximum output. Because hydropower plants can generate power to the grid immediately, they provide essential backup power during major electricity outages or disruptions.

• C. Contribution of Hydro Power towards Climate Change: Hydro power and climate change share a paradoxical relationship. On one hand, as a renewable and clean source, hydro power contributes to reduction in greenhouse gas emission and hence to mitigation of global warming and climate change, on the other hand climate change is likely to affect weather pattern in any region impacting water availability and thus hydro power generation. However as per studies hydro power prevents emission of 3 Giga Tonne of equivalent CO₂ per year which represents about 9% of global annual CO₂ emissions.
• According to the World Energy Council (WEC), the CO₂ emissions per GWh are 3–4 T for hydropower run-of the river, and 10–33 T for hydropower with a reservoir; these values are about 100 times less than the emissions from traditional thermal power. Moreover, it is seen that the greenhouse gas emissions from Hydro Power is 4 gram CO₂/kWh against 38 gram CO₂/kWh from Solar Power. In a world engulfed by pollution and greenhouse gas emission endangering human civilization, hydropower which is the oldest form of clean, green and cheap source of electricity can act as a established technology in contributing towards mitigation of climate change and play a role in climate change adaptation of water resource availability.

In addition, hydropower also supports the rapid growth of other renewable sources like solar and wind power due to the flexibility and storage it can offer to the grids that are increasingly becoming reliant on variable power supply. 

Furthermore, as has already been mentioned in the advantages of hydropower, beyond its power benefits, hydropower also provides water services. Reservoir storage capacity can be used for drinking water supply, irrigation and flood control. Increasing global water storage capacity is imperative to adopting to a warmer world and meeting water demand. 

• D. Benefit in Power Sector: Hydropower is often used as a peaking station to cater peak load condition in the grid. Generally hydro power plants are given minimum schedule of three hours during the day. In addition to that, it is often used as a Tertiary Reserve Ancillary Services (TRAS) for maintaining uniform frequency due to quick start capability of hydro power plants. 

Blackout is a condition in power system where suddenly a particular area goes dark as all generating units supplying power crashes. This event has a cascading effect and can perturb entire power grid if not contained. Hydro power is the first generation plant that is started to restore the grid in blackout.

Hydropower is an excellent source of voltage regulation. During low load condition especially at night when the reactive power (Volt-Amps Reactive, VAR) is more in the grid, hydro generators have the capacity to absorb VAR and during peak load, it injects VAR to the grid. Many of the hydro generators are designed to operate as synchronous condenser also.

These days we are witnessing big push for development of renewable sources which is also commitment of the developed as well as developing nations to sustainable environment. But the electricity generated by wind and solar energy do not take place during the peak hours.

Moreover, the weather forecasting becomes very important for operation of renewable sources of energy other than hydro as there is no or very less spinning reserve (electronically controlled). In case sudden outage or less generation due to adverse weather conditions, heavy power crisis may occur in the grid.

With significantly increasing amount of wind and solar facilities into the electricity supply system, this kind power fluctuations in the grid due to high and low generation creates disturbances in the grid. Hydro due to its inherent quality of flexible operation is used as Secondary Reserve Ancillary Service to overcome such situations.

Pump Storage Hydro Project

As discussed above in the benefit of hydropower, with massive integration of solar and wind energy in the national grid, the importance of hydropower remains undeniable for grid reliability. Large hydro power plants are often time taking projects and involves huge investments. Pump Storage Hydro is a very promising alternative to this problem and is the natural large-scale energy storage solution which is often termed as natural battery. All the features of hydro projects are available in pump hydro project. In a pump hydro project, there are two interconnected reservoirs, one in higher elevation and other in lower elevation. The turbine used in the pump storage hydro project can be used as generator as well as motor which offers a great deal of flexibility of grid operations.

So far, India have already developed pumped storage plants of installed capacity of 4.74 gigawatt (GW). Total potential of Pump Storage Project (PSP) in the country is assessed as 123.95GW for both On-River and Off-River mode.

Hydroelectric Power in India:

India is the third largest producer and consumer of electricity globally, having annual electricity production between 1200-1300TWh and growing at an annual growth rate of 5% during the last decade. As on February 2024 data, the installed generation capacity of the country stood at 434.195 GW, comprising 243.217 GW of thermal, 136.570 GW of renewables (Wind, solar, small hydro and biomass), 46.928 GW hydro(above 25 MW capacity) and7.480 GW of nuclear power. The hydro generation with an installed capacity of 51.922 GW including 4.994 GW small hydro (below 25 MW capacity) constitute the largest share of 28% in the renewable generation mix.

India’s first hydro power plant was developed in the year 1897 at Darjeeling with an installed capacity of 130 KW which was also the first hydroelectric plant in Asia. As per study conducted by the Central Electricity Authority (CEA) during 1978-1987, the assessed hydro power potential in the country is about 145 GW. Whereas hydropower harnessed till date stands at 46.9 GW which is approx. 32% of the potential. Amongst these 33% have been developed by Central agencies, 60% by state utilities and 7% by private players. 

As India put forth its strong climate change commitment by reducing carbon emission intensity by 33 to 35% as a percentage of its GDP and addition of 500 GW of non-fossil energy by 2030, development of hydropower is imperative. Lately, due to the thrust on renewable, the Government of India has also put its attention to the development of Pumped Storage Hydropower for a reliable and stable grid.

New Hydro Policy: A riverine country like India when set out to achieve an ambitious target to have its 50% of electricity supply from non-fossil fuel, then it has to provide conducive environment to develop its hydropower potential. Hence, in the recent hydro policy the Ministry of Power, Govt. of India has brought the following measures for promoting hydro power sector,

a.  Previously only hydropower projects less than 25MW were considered in renewable sources. But, now as per the new hydro policy all hydro projects are declared as renewable sources of energy. However, the requirement for obtaining statutory clearances for large hydro power plants are still mandatory.

b.  This policy has made the provision for Hydropower Purchase Obligation (HPO) within Non-Solar Renewable Purchase Obligation. With this the hydropower projects will be given incentive as a fixed percentage of power will be purchased by large consumers/ entities/ discoms electricity generated from Large Hydropower Projects.

c.  The debt repayment period for hydro projects has been increased to 18 years from current 12 years with the provision to introduce an escalating tariff of 2%. Moreover, the project life is increased to 40 years from earlier 35 years.

d. This policy allowed storage hydroelectric projects to have budgetary support for flood moderation component which will further bring down the cost of development of hydropower project.

e. As the hydro power projects are located in very remote locations the new policy has made the provision for budgetary support for development of infrastructure such as roads and bridges. The grant will be limited to 1.5 crore per MW for projects upto 200 MW and 1 crore per MW for project above 200 MW.

With this new hydro policy, the cost of development of hydropower will be reduced substantially and a competitive levelized tariff can be fixed. This step will promote development of clean energy in the country.

As the world commits to low greenhouse gas emission, renewable and clean energy sources have become today’s norm as far as Power sector is considered. In this new norm hydro power is the oldest form to be harnessed and shall act as the balancing source in the new power operation system. India is also a stakeholder in this commitment towards cleaner and greener World.

In this context, Northeast can be the Power House of the country with its vast hydropower potential. Many hydropower plants are under construction in the Northeastern region which are planned to be commissioned in 2022-27 shall add 10,462 MW to installed capacity of hydropower. In Arunachal Pradesh large hydropower projects like Subansiri Lower H.E. Project (2000 MW) and Dibang Multipurpose Project (2880 MW) are under construction by NHPC Limited.

In August 2023 Government of Arunachal Pradesh signed MOU with Central PSUs, viz., NHPC Limited, SJVN Limited, THDC India Ltd and NEEPCO for developing 12 hydropower projects with a total capacity of 11,523 MW. When cost benefit analysis is conducted between different sources of energy the hydropower emerges as the most cost-effective option as it does not have any expenditure towards fuel. India has the blessing of many rivers and its basins. Development of these river basins will not only benefit the country economically but also will make the country energy secure without affecting the climate.

Pulak Deka is Senior Manager (Mech.), NHPC Ltd, Anirban Bhattacharjee is Senior Manager (Elec.), NHPC Ltd and A.N. Mohammed is Consultant, NHPC Ltd.