RENEWABLE ENERGY SOURCES AND THIER SHARE IN INDIA

Renewable energy is generally defined as energy that comes from resources which are naturally replenished on a human timescale, such as sunlight, wind, rain, tides, waves, and geothermal heat. Renewable energy replaces conventional fuels in four distinct areas: electricity generation, air and water heating/cooling, motor fuels, and rural (off-grid) energy services.

Based on REN21's 2014 report, renewables contributed 19 percent to our global energy consumption and 22 percent to our electricity generation in 2012 and 2013, respectively. This energy consumption is divided as 9% coming from traditional biomass, 4.2% as heat energy (non-biomass), 3.8% hydro electricity and 2% is electricity from wind, solar, geothermal, and biomass. 

SOLAR ENERGY

Solar panels converts the sun's light in to usable solar energy using N-type and P-type semiconductor material.  When sunlight is absorbed by these materials, the solar energy knocks electrons loose from their atoms, allowing the electrons to flow through the material to produce electricity. This process of converting light (photons) to electricity (voltage) is called the photovoltaic (PV) effect.  Currently solar panels convert most of the visible light spectrum and about half of the ultraviolet and infrared light spectrum to usable solar energy.

Solar energy technologies use the sun's energy and light to provide heat, light, hot water, electricity, and even cooling, for homes, businesses, and industry.

There are a variety of technologies that have been developed to take advantage of solar energy.

Solar Energy Technologies:

Photovoltaic Systems
      Producing electricity directly from sunlight.

Solar Hot Water
       Heating water with solar energy.

Solar Electricity
       Using the sun's heat to produce electricity.

Passive Solar Heating and Daylighting
       Using solar energy to heat and light buildings.

Solar Process Space Heating and Cooling
       Industrial and commercial uses of the sun's heat.

WIND ENERGY

Wind turbines, like windmills, are mounted on a tower to capture the most energy. At 100 feet (30 meters) or more aboveground, they can take advantage of the faster and less turbulent wind. Turbines catch the wind's energy with their propeller-like blades. Usually, two or three blades are mounted on a shaft to form a rotor.

A blade acts much like an airplane wing. When the wind blows, a pocket of low-pressure air forms on the downwind side of the blade. The low-pressure air pocket then pulls the blade toward it, causing the rotor to turn. This is called lift. The force of the lift is actually much stronger than the wind's force against the front side of the blade, which is called drag. The combination of lift and drag causes the rotor to spin like a propeller, and the turning shaft spins a generator to make electricity.

Wind turbines can be used as stand-alone applications, or they can be connected to a utility power grid or even combined with a photovoltaic (solar cell) system. For utility-scale sources of wind energy, a large number of wind turbines are usually built close together to form awind plant. Several electricity providers today use wind plants to supply power to their customers.

Stand-alone wind turbines are typically used for water pumping or communications. However, homeowners, farmers, and ranchers in windy areas can also use wind turbines as a way to cut their electric bills.

Small wind systems also have potential as distributed energy resources. Distributed energy resources refer to a variety of small, modular power-generating technologies that can be combined to improve the operation of the electricity delivery system.

GEOTHERMAL ENERGY

Geothermal energy is the natural heat of the earth. Earth's interior heat originated from its fiery consolidation of dust and gas over 4 billion years ago. It is continually regenerated by the decay of radioactive elements, that occur in all rocks.

From the surface down through the crust, the normal temperature gradient - the increase of temperature with the increase of depth - in the Earth's crust is 17 °C -- 30 °C per kilometer of depth (50 °F -- 87 °F per mile).

Below the crust is the mantle, made of highly viscous, partially molten rocks with temperatures between 650 °C -- 1250 °C (1200 °F -- 2280 °F). At the Earth's core, which consists of a liquid outer core and a solid inner core, temperatures vary from 4000 °C -- 7000 °C (7200 °F-- 12600 °F).

Major geothermal fields are situated in circum-pacific margins, rift zones of East Africa, North Africa, Mediterranean basin of Europe, across Asia to Pacific.

Geothermal reserves up to depths of 10 km are estimated at 403X106 Quads. The world average geothermal heat flow is 0.06 W/m2 

There are four major types of Geothermal energy resources.

 Hydrothermal 
 Geopressurised brines
 Hot dry rocks
 Magma


Currently, hydrothermal energy is being commercially used for electricity generation and for meeting thermal energy requirements. In 1997, The world's geothermal electricity generation capacity was 8000 MW and another 12000 MW for thermal applications. 

Italy, New Zealand, USA, Japan, Mexico, Philippines, Indonesia are some of the countries which are using geothermal energy for electricity generation and thermal applications. Exploration of geothermal fields needs knowledge of geology, geochemistry, seismology, hydrology and reservoir engineering. 

In India, exploration and study of geothermal fields started in 1970. The GSI (Geological Survey of India) has identified 350 geothermal energy locations in the country. The most promising of these is in Puga valley of Ladakh. The estimated potential for geothermal energy in India is about 10000 MW. 

There are seven geothermal provinces in India : the Himalayas, Sohana, West coast, Cambay, Son-Narmada-Tapi (SONATA), Godavari, and Mahanadi. 

BIOMASS

We have used biomass energy or bioenergy - the energy from organic matter - for thousands of years, ever since people started burning wood to cook food or to keep warm.

And today, wood is still our largest biomass energy resource. But many other sources of biomass can now be used, including plants, residues from agriculture or forestry, and the organic component of municipal and industrial wastes. Even the fumes from landfills can be used as a biomass energy source.

The use of biomass energy has the potential to greatly reduce our greenhouse gas emissions. Biomass generates about the same amount of carbon dioxide as fossil fuels, but every time a new plant grows, carbon dioxide is actually removed from the atmosphere.The net emission of carbon dioxide will be zero as long as plants continue to be replenished for biomass energy purposes. These energy crops, such as fast-growing trees and grasses, are called biomass feedstocks. The use of biomass feedstocks can also help increase profits for the agricultural industry.

 Estimates have indicated that 15% - 50% of the world?s primary energy use could come from biomass by the year 2050. Currently, about 11% of the world?s primary energy is estimated to be met with biomass.

For India, biomass has always been an important energy source. Although the energy scenario in India today indicates a growing dependence on the conventional forms of energy, about 32% of the total primary energy use in the country is still derived from biomass and more than 70% of the country?s population depends upon it for its energy needs.

HYDRO POWER

Flowing water creates energy that can be captured and turned into electricity. This is called hydroelectric power or hydropower.

The most common type of hydroelectric power plant uses a dam on a river to store water in a reservoir. Water released from the reservoir flows through a turbine, spinning it, which in turn activates a generator to produce electricity. But hydroelectric power doesn't necessarily require a large dam. Some hydroelectric power plants just use a small canal to channel the river water through a turbine.

Another type of hydroelectric power plant - called a pumped storage plant - can even store power. The power is sent from a power grid into the electric generators. The generators then spin the turbines backward, which causes the turbines to pump water from a river or lower reservoir to an upper reservoir, where the power is stored. To use the power, the water is released from the upper reservoir back down into the river or lower reservoir. This spins the turbines forward, activating the generators to produce electricity.

Ministry of New and Renewable Energy has been vested with the responsibility of developing Small Hydro Power (SHP) projects up to 25 MW station capacities. The estimated potential for power generation in the country from such plants is about 20,000 MW. Most of the potential is in Himalayan States as river-based projects and in other States on irrigation canals. The SHP programme is now essentially private investment driven. Projects are normally economically viable and private sector is showing lot of interest in investing in SHP projects. The viability of these projects improves with increase in the project capacity. The Ministry’s aim is that at least 50% of the potential in the country is harnessed in the next 10 years.

The basics of power from water is the result of conversion of potential energy (the water body at a certain height which is known as the "Head") to kinetic energy (a flow which is known as "Discharge" down the pipe) which is transferred to the buckets in the turbine (mechanical energy). It is the prime mover for the generator (electrical energy) which produces electricity.

Essentially power from a small hydro potential site is derived from two parameters, head and discharge .

Where "head" is the vertical height from which the potential energy of water is converted into electricity after the fall and discharge is the flow rate of the water in the stream/river.

Power (kW) = H * Q * Y

Where
H = Head in m(meter)
Q = Discharge in m3/sec (cumecs) Y = Specific weight of water, being the product of mass and acceleration due to gravity (9.81 kN/m3).

Hydro Power Project Classification   

Hydro power projects are generally categorized in two segments i.e. small and large hydro. In India, hydro projects up to 25 MW station capacities have been categorized as Small Hydro Power (SHP) projects.  While Ministry of Power, Government of India is responsible for large hydro projects, the mandate for the subject small hydro power (up to 25 MW) is given to Ministry of New and Renewable Energy. Small hydro power projects are further classified as

Class	Station Capacity in kW
Micro Hydro	Up to 100
Mini Hydro	101 to 2000
Small Hydro	2001 to 25000

The Ministry’s aim is that the SHP installed capacity should be about 7000 MW by the end of 12th Plan. The focus of the SHP programme is to lower the cost of equipment, increase its reliability and set up projects in areas which give the maximum advantage in terms of capacity utilization.
Water  Mill, Uttarakhand.

An estimated potential of about 20,000 MW of small hydro power projects exists in India. Ministry of New and Renewable Energy has created a database of potential sites of small hydro and 6,474 potential sites with an aggregate capacity of 19,749.44 MW for projects up to 25 MW capacity have been identified.

TIDAL ENERGY

Oceans cover 70 percent of the earth’s surface and represent an enormous amount of energy in the form of wave, tidal, marine current and thermal gradient. The energy potential of our seas and oceans well exceeds our present energy needs. India has a long coastline with the estuaries and gulfs where tides are strong enough to move turbines for electrical power generation. A variety of different technologies are currently under development throughout the world to harness this energy in all its forms including waves (40,000 MW), tides (9000 MW) and thermal gradients (180,000 MW).

Tides are generated through a combination of forces exerted by the gravitational pull of the sun and the moon and the rotation of the earth. The relative motion of the three bodies produces different tidal cycles which affect the range of the tides. In addition, the tidal range is increased substantially by local effects such as shelving, funneling, reflection and resonance. Energy can be extracted from tides by creating a reservoir or basin behind a barrage and then passing tidal waters through turbines in the barrage to generate electricity. Tidal energy is extremely site specific requires mean tidal differences greater than 4 meters and also favorable topographical conditions, such as estuaries or certain types of bays in order to bring down costs of dams etc. Since India is surrounded by sea on three sides, its potential to harness tidal energy has been recognized by the Government of India.

The most attractive locations are the Gulf of Cambay and the Gulf of Kachchh on the west coast where the maximum tidal range is 11 m and 8 m with average tidal range of 6.77 m and 5.23 m respectively. The Ganges Delta in the Sunderbans in West Bengal also has good locations for small scale tidal power development. The maximum tidal range in Sunderbans is approximately 5 m with an average tidal range of 2.97 m.

The identified economic tidal power potential in India is of the order of 8000-9000 MW with about 7000 MW in the Gulf of Cambay about 1200 MW in the Gulf of Kachchh and less than 100 MW in Sundarbans.

HYDROGEN POWER

Hydrogen is the simplest element. An atom of hydrogen consists of only one proton and one electron. It's also the most plentiful element in the universe. Despite its simplicity and abundance, hydrogen doesn't occur naturally as a gas on the Earth - it's always combined with other elements. Water, for example, is a combination of hydrogen and oxygen (H₂O).

Hydrogen is also found in many organic compounds, notably the hydrocarbons that make up many of our fuels, such as gasoline, natural gas, methanol, and propane. Hydrogen can be separated from hydrocarbons through the application of heat - a process known as reforming. Currently, most hydrogen is made this way from natural gas. An electrical current can also be used to separate water into its components of oxygen and hydrogen. This process is known as electrolysis. Some algae and bacteria, using sunlight as their energy source, even give off hydrogen under certain conditions.

Hydrogen is high in energy, yet an engine that burns pure hydrogen produces almost no pollution. NASA has used liquid hydrogen since the 1970s to propel the space shuttle and other rockets into orbit. Hydrogen fuel cells power the shuttle's electrical systems, producing a clean byproduct - pure water, which the crew drinks.

Hydrogen is a colorless, odorless, tasteless, flammable gas. It is found in water, organic compounds, biomass, and hydrocarbons such as petrol, natural gas, methanol, and propane. Hydrogen is high in energy content as it contains 120.7 kilojoules/gram. This is the highest energy content per unit mass among known fuels. However, its energy content per unit volume is rather low. Thus, challenges are greater in the storage of hydrogen for civilian applications, as compared to storage of liquid fossil fuels. When burnt, hydrogen produces water as a by-product and is therefore not only an efficient energy carrier but a clean, environmentally benign fuel as well.

Hydrogen can be used for power generation and also for transport applications. It is possible to use hydrogen in internal combustion (IC) engines, directly or mixed with diesel and compressed natural gas (CNG) or hydrogen can also be used directly as a fuel in fuel cells to produce electricity. Hydrogen energy is often mentioned as a potential solution for several challenges that the global energy system is facing. The advantages are the fact that hydrogen use results in nearly zero emissions at end-use, and that hydrogen opens up the possibility of decentralized production on the basis of a variety of fuels. But it is found that hydrogen will not play a major role in India without considerable research, technology innovations and cost reductions, mainly in fuel cell technology. This section provides inputs on the status of hydrogen energy in India.

Hydrogen Energy programme started in India after joining the IPHE (International Partnership for Hydrogen Economy) in the year 2003. There are nineteen other countries including Australia, USA, UK, Japan, etc.This global partnership helps India to set up commercial use of Hydrogen gas as an energy source. This will be implemented through Public Private Partnership.

Hydrogen Production

Globally, over 95% of hydrogen is produced from hydrocarbons; about 4% is produced through electrolysis of water

Hydrogen is also produced as a by-product in chloralkali industries.

There are several other methods to produce hydrogen that are at different stages of research and demonstration.

These methods include hydrogen production through

(a) Biomass and biological route,
(b) Photo electrochemical route,
(c) Thermo chemical decomposition of water using nuclear energy or solar energy, and
(d) Electrolysis using renewable energy (solar, wind).

Hydrogen Storage Technologies

The most common method of storage of hydrogen is in gaseous form in pressurized cylinders/tanks.

Hydrogen-Fuelled Vehicles

It is possible to run commercially available IC-engine vehicles directly on hydrogen, or on hydrogen mixed with CNG.

Fuel Cell Power Packs

Research efforts over the past several years have resulted in the development of phosphoric acid fuel cell (PAFC) systems and polymer electrolyte membrane fuel cell (PEMFC) systems.