​

​

​

​

​

*

UNIT – IV

Renewable Energy Resources

​

Dr.A.Geetha

Associate Professor

Department of Chemistry

Kongu Engineering College

*

Renewable Energy Resources

Introduction - global energy consumption scenario - types of energy resources – nuclear energy – nuclear power reactor – breeder reactors – applications and disadvantages of nuclear energy – design, working, advantages and disadvantages of solar energy, hydropower, wind energy, geothermal energy, tidal and wave power, ocean thermal energy – biomass and biofuels – hydrogen as an alternate fuel – hydrogen production – advantages, disadvantages and applications – nanotechnology for energy sector.

Renewable Energy Resources�

*

• Renewable resources are an energy source that cannot be depleted and are able to supply a continuous source of clean energy.

​

• Renewable energy is also called "clean energy" or "green power" because it doesn't pollute the air or the water.

​

• Renewable energies are also often referred to as “green energies” or “clean energies”. Still, this doesn’t mean that these energies aren’t harmful to the environment and have zero impact. Nonetheless, they have a low environmental impact compared to fossil fuels. That’s why they’re increasingly becoming important elements in terms of sustainable development.

​

​

​

​

*

• Renewable energies (or renewables) are ways to generate energy from (theoretically) unlimited natural resources. These resources are either available with no time limit or replenish more quickly than the rate at which they are consumed.

​

• Renewable energies are generally spoken of as opposed to fossil fuel energies. The fossil fuels’ stocks are limited and non-renewable in the human timescale. The most known examples of these resources are coal, oil or natural gas. On the contrary, renewable energies are produced from renewable sources.

​

*

• The major types of renewable energy sources are:
• Biomass
• Wood and wood waste
• Municipal solid waste
• Landfill gas and biogas
• Ethanol
• Biodiesel
• Hydropower
• Geothermal
• Wind
• Solar

*

• Non-renewable energy comes from sources that will run out or will not be replenished for thousands or even millions of years. Most sources of non-renewable energy are fossil fuels. ... Non-renewable energy comes from sources that will run out or will not be replenished in our lifetimes—or even in many, many lifetimes.

​

Types of Non-Renewable Energy

• Coal: Coal comes from the remains of plants that died hundreds of millions of years ago. ...
• Oil: Oil – also known as petroleum – can be extracted and refined in order to make products such as gasoline, diesel, and jet fuel. ...
• Natural Gas.
• Nuclear Energy.

​

*

*

Global energy consumption scenario

​

​

​

​

​

​

​

​

​

​

​

​

​

​

*

​

​

​

Energy distribution:

• Developed countries like USA and Canada constitute only 5% of the world’s population, but consume 25% of the available world’s energy resources.
• It has been observed that in USA and Canada an average person consumes 300 GJ (giga joules: equal to 60 barrels of oil) per year.
• But in poor countries like Bhutan, Nepal and Ethiopia, an average person consumes 1 GJ per year.

*

*

​

​

Energy Crisis in India

• MW stands for megawatt, a unit of power equal to one million watts.

​

• Sometimes, the two letters are used as an abbreviation for milliwatt, a unit equal to one thousandth of a watt.

*

*

Renewable Energy Sources in India

*

TYPES OF ENERGY RESOURCES

​

*

Nuclear Energy

• Nuclear energy is the energy that is stored in the nucleus of an atom. Nuclear energy contribute to about 11% of world’s electricity consumption. 
• Dr. H.J. Bhabha was the father of nuclear power plant in India. 
• India has 10 nuclear reactors, which produce 2% of India’s electricity. Nuclear energy can be produced by two types of reactions.
• By nuclear fission.
• By nuclear fusion.

​

​

​

​

​

​

​

​

​

​

​

​

​

​

​

​

​

​

​

​

*

Nuclear Fission

• Splitting a heavier atom into two or more smaller ones, by bombarding it with a neutron.
• Today, nuclear reactors are used through out the world including India are fueled by naturally­ occurring uranium 235.
• The fission of U²³⁵ releases an enormous amount of heat energy.
• In fact one kg of U²³⁵, completely fissioned, could yield as much energy as 2000 metric ton of coal.

*

Nuclear Fusion

• Process of combining two or more smaller atoms to form a heavier one.
• Nuclear fusion involves uniting of two small atoms to form a larger one.
• In this process, enormous amount of energy is liberated.
• Energy released by

​

​

​

• The sun and other stars are prime

examples of fusion power.

​

​

​

​

​

​

​

​

​

​

​

​

​

​

​

​

*

Nuclear Power Plants in India

• Tarapur, Maharastra 
• Ramapratap Sagar, Rajasthan 
• Kalpakkam, Tamil Nadu 
• Narora, UP 
• Kudangulam, Tamil Nadu

​

Major Problems of Nuclear Energy

• Waste disposal 
• Thermal pollution 
• Limited supply and availability of uranium 
• High cost 
• Environmental contamination of long lasting radioactive nuclides.

​

*

Nuclear Power Reactor

• Nuclear reactors are designed to carry out nuclear reactions for generation of electricity, heat, radioactive isotopes and nuclear chemistry research.
• It may be classified as power and breeder reactors.

​

• Principle: The energy released from of fissionable material (e.g. enriched ²³⁵U) is harnessed as heat and is used to produce steam, which drives the turbine to produce electricity.

​

• Main components and their functions:

1. Fuel rods: These are made up of hundreds of ²³⁵U pellets stacked with each other. These rods are arranged into fuel assemblies inside the core.

2. Moderator: Its function is to slow down the speed of neutrons because proper speed of neutrons is required in order to get captured by nucleus cause fission. In most cases, water is used as a moderator.

3. Control rods: these materials are highly efficient neutron captures, for example, cadmium and boron. These rods can be inserted or withdrawn from the reactor core to control the rate of reaction.

*

4. Coolant: It is used to absorb heat from the reactor. Example: water

​

5. Steam generator: It generates steam to spin the turbine (not used in boiling water reactors).

​

6. Containment: It is a shield made of concrete and steel to protect the nuclear reactor from the environment and to protect the environment form any radiation due to malfunction.

​

​

​

​

*

Nuclear reactor may also classified in different ways , depending on the type of coolant, moderator and fuels used.

​

1. Thermal neutron reactors :

• Light water moderated reactors (LWRs): These reactors use ordinary water as moderator and coolant. These are simpler and cheaper than other reactors; and also have excellent safety and stability in comparison to the others.
• Boiling water reactors (BWRs)
• Pressurized water reactors
• Supercritical water reactors
• Heavy water moderated reactors
• Graphite moderated reactors
• Gas cooled reactors
• Water cooled reactors

​

​

​

​

2. Fast neutron reactors:

The nuclear fission in these reactors is carried out by unmoderated fast neutrons. These are generally cooled by liquid metal.

​

*

Breeder Reactors

• Breeder reactors generate new fissionable material at a rate greater than their consumption rate.
• Due to their superior fuel economy, they are highly in demands.
• Normal reactors consume less than 1 % of the natural uranium, while breeder reactors can utilize a much greater amount of initial fissionable materials, and can consume almost all the remaining initial material too by reprocessing.
• While normal reactors use naturally occurring uranium, which has very small quantities of fissile ²³⁵U, breeder reactors can be designed to utilize thorium, which has abundant than uranium.

​

*

Breeding ratio is the measure of the efficiency of a reactor. It is the average number of fissile, atoms created per fission event. While normal LWRs show a breeding ratio of 1.1 or 1.2, breeders give ratios as high as 1.8.

Types:

1. Fast breeder reactor: This uses plutonium as the initial fuel, and thereafter only natural uranium. Therefore, this fuel cycle is termed as plutonium economy.
2. Thermal breeder reactor: This type of reactor uses enriched uranium, or mixed oxide fuel as the initial fuel, and thereafter requires only thorium as the input. ²³²Th produces ²³⁵U after neutron capture and β-decay.

​

​

​

​

​

​

*

Applications of Nuclear Energy

1. Electricity generation:
• Environment-friendly energy resource for power generation.
• A small amount of nuclear fuel is sufficient for production of large amount of energy in nuclear-powered reactors.
• The water that is discharge from the nuclear reactors is free from radiation and is clean to conserve wild and aquatic ecosystem.
2. Healthcare:
• Radioactive isotopes find use in treatment of cancer by radiotherapy.
• A large number of diagnostic techniques make use of nuclear radiation.
• These include X-ray imaging using ⁶⁰Co, positron emission tomography (PET) using positron emitting nucleotides, etc.
• Nuclear radiation is also used for sterilization to destroy microorganisms.

*

3. Agriculture:

• Nuclear energy is used to enhance the production of / yield of crops.
• The use of nuclear radiation prevents moulding of seeds, delays ripening of fruits and brings about other such desirable changes.
• Some techniques such as sterile insect technique are useful in control of agricultural pests.

​

*

Disadvantages of Nuclear Energy

• The major disadvantage associated with the nuclear energy is the expulsion of radiation.
• The nuclear radiations penetrate deep into the body, damage cells and lead to illness, and sometimes even death.
• Any malfunction in the nuclear reactor may lead to leakage of radiation and people exposed to it may be susceptible to illness, years after exposure.
• The radioactive waste from nuclear reactors is hazardous and once it enters the biosphere (ecosystem), it will take years to decay to safe levels.
• Another disadvantage of nuclear energy is a disaster known as meltdown. This occurs when a nuclear reaction goes out of control leading to a nuclear explosion, thereby producing a lot of harmful radiation.

*

SOLAR ENERGY

• Energy from the sun
• They are two categories : Thermal Energy & Electric Energy

Solar Cells

• ability to convert the light energy from sun into electricity.
• Appliances: lighting, water pumping, refrigeration, telecommunications and television, which utilize photovoltaic electricity.

​

​

​

​

​

​

​

​

​

*

• Consists of a p-n junction formed in a semiconductor material
• The solar cell consists of 0.2 to 0.3 mm thick silicon having two layers with different electrical properties formed by the process of doping.
• The doping method involves the combination of two dissimilar impurities (Example: boron and phosphorus).
• An electric field is established at the junction between negatively (using phosphorus atoms) and positively doped (using boron atoms) silicon layers.
• If light is incident on the solar cell, then energy from the light (photons) creates free charge carriers, which are separated by the electrical field.
• An electrical voltage is generated at the external contacts, so that current can flow when a load is connected.
• The most common types using silicon semiconductor material (Si) are monocrystalline Si cells, polycrystalline Si cells and amorphous Si cells.

​

​

​

​

*

Solar Cooker

1. Concentrating sunlight:
• A mirrored surface with high specular reflectivity is used to concentrate light from the sun on to a small cooking area.
• The solar cooking products are typically designed to achieve temperatures between 150°F (65°C) (baking temp.) to 750°F (400°C) (grilling/searing temp.) on a sunny day.

2. Converting light energy to heat energy:

• The solar cookers concentrate sunlight onto a receiver such as a cooking pan.
• Eventually, the interaction between sunlight and the receiver material converts light energy into heat energy.

*

​

​

Solar Dryer

• Solar dryers are devices that use solar energy to dry substances, especially food.

1. Direct Solar Drier:

• The direct solar dryers expose the substance to be dehydrated through direct sunlight.
• Traditionally, food items and clothes are dried in outdoor area through direct sunlight.
• In Mongolia, cheese and meat are still conventionally dried on top of the tent, where it acts as a natural solar dryer.
• A modern solar dryer consists of a black absorbing surface which collects the light energy and converts it into heat energy.

2. Indirect Solar Drier:

• In indirect solar dryers, the black surface or medium heats the incoming air rather than directly heating the substance to be dried.

​

​

​

​

​

*

• The hot air is passed over to the medium or substance which is to be dried and it exits upwards often through a chimney, thus vaporizing the moisture released from the substance.
• Indirect solar systems are very simple, it contains a tilted cold frame with black cloth to an insulated brick building with active ventilation and a backup heating system.
• One of the advantages of the indirect system is that it is easier to protect the food from contamination (wind, birds, insects or animals).

*

Solar Pond

​

• The key feature of a salt-water solar pond is that it has increasing amounts of salts dissolved in the water with depth.
• The salinity and density at each level of the pond thus increases with depth, so it is often called ‘salt stabilized’ or ‘salinity-gradient’ solar ponds.

​

• Below this salinity-gradient zone there is a layer of near saturated salt solution. Across the ‘storage zone’ and above it there is a thin layer of fresh or low-salinity water called the surface zone.

*

• The storage zone is typically one or two meters thick and the overall pond is two or more meters deep.
• Most of the incoming solar radiation reaches the storage zone at the bottom of the pond where it heats up the concentrated salt solution there.
• Small heat loss occurs by conduction through the bottom and sides of the pond.
• The storage zone heats up and retains this thermal energy until it is withdrawn for use.
• Temperatures above 80°C can be obtained in periods of high solar radiation and elevated temperatures over ambient are maintained overnight and to some extent from summer to winter too.
• The surface zone with a thickness of typically half a meter is mixed and kept cool by the winds blowing across the pond and heat loss occurs by evaporation.

*

Advantages of Solar Energy

• Solar energy is a universal, decentralized and pollution-free energy.

​

• Solar energy is the energy acquired from the sun which reaches earth in the form of short wave radiation, it is a visible light and near ultraviolet light.

• Solar energy helps considerably in maintaining the ecological balance through the process of photosynthesis and greenhouse effect.

• Solar energy is bound to achieve great economic importance in the impending future due to the depletion of conventional energy sources.

​

​

​

​

​

​

​

​

​

​

​

​

​

Hydropower

• Most common form of renewable energy in electric power generation across the globe.

​

• Why hydropower?

Renewable energy

Hydropower is clean

​

• What is hydropower ?

“Hydro” derives from the Greek word meaning of water. From that origin, hydroelectric power refers to electricity generated from a falling or fast-running water source.

​

Working

• Initially the water from catchment area flows to the dam.
• At the dam the water gets accumulated. Thus the potential energy of the water increases due to the height of the dam.
• When the gates of the dam are opened then the water moves with high Kinetic energy into the penstock. Through the penstock water goes to the turbine house.
• Thus the Kinetic Energy of the moving water gets converted into the Electrical Energy with the help of Turbine & Generator combination.

​

​

Wind energy

• Wind power can be used to generate electricity. It is a renewable energy source and one of the fastest growing energy sources in the world.
• Wind turbine is a device that converts the wind’s kinetic energy into electrical energy.
• Wind farm is a group of wind turbines in the same location used for the production of electric power.
• In India, electricity is produced by windmills in the coastal regions of Tamil Nadu, Gujarat, Andhra, Maharashtra, Kerala and Karnataka.
• In India, Tamil Nadu is the leading producer of windmill electricity followed by Gujarat.
• In Tamil Nadu with the help of Danish International Agency (DIA), wind farms are established at Kayatharu (Thoothukudi district), Muppandal and Mullakkadu (Kanyakumari district).

Working

• The wind passes over the blades and makes them turn(kinetic energy).
• The blades turn a shaft within the nacelle.
• The shaft turns a generator which converts the kinetic energy into electrical energy.
• A transformer converts the electricity to the right voltage.
• The electricity is then exported to the local electricity grid network.

​

​

*

WAVE POWER, TIDAL POWER AND OCEAN THERMAL ENERGY

​

The ocean can produce two types of energy: 

1.Thermal energy from the sun’s heat, and 

2.Mechanical energy from the tides and waves.

​

Oceans cover more than 70% of Earth’s surface, making them the world’s largest solar collectors. The sun’s heat warms the surface water a lot more than the deep ocean water, and this temperature difference creates thermal energy. Just a small portion of the heat trapped in the ocean could power the world.

Ocean thermal energy is used for many applications, including electricity generation. There are three types of electricity conversion systems: closed-cycle, open-cycle, and hybrid. 

​

Closed-cycle systems use the ocean’s warm surface water to vaporize a working fluid, which has a low-boiling point, such as ammonia. The vapor expands and turns a turbine. The turbine then activates a generator to produce electricity.

​

Open-cycle systems actually boil the seawater by operating at low pressures. This produces steam that passes through a turbine/generator.

​

And hybrid systems combine both closed-cycle and open-cycle systems.

*

Ocean mechanical energy is quite different from ocean thermal energy. Even though the sun affects all ocean activity, tides are driven primarily by the gravitational pull of the moon, and waves are driven primarily by the winds. As a result, tides and waves are intermittent sources of energy, while ocean thermal energy is fairly constant.

​

Also, unlike thermal energy, the electricity conversion of both tidal and wave energy usually involves mechanical devices.

A barrage (dam) is typically used to convert tidal energy into electricity by forcing the water through turbines, activating a generator.

​

For wave energy conversion, there are three basic systems: channel systems that funnel the waves into reservoirs; float systems that drive hydraulic pumps; and oscillating water column systems that use the waves to compress air within a container. The mechanical power created from these systems either directly activates a generator or transfers to a working fluid, water, or air, which then drives a turbine/generator.

Ocean waves and Tidal power

• Tidal energy is a form of hydropower that converts the energy of the tides into electricity while wave power harnesses the energy of Ocean waves.
• There is a distinct difference between Wave power and Tidal power.
• The tide is created by the gravitational effects of the sun and the moon on the earth causing cyclical movement of the seas. Waves are created by wind blowing over the surface of water.
• As 75% of earth’s surface is covered by water, there is scope to generate wave and tidal power on large scale.

​

Energy from the Ocean

• Tidal power
• Wave power
• Ocean Thermal Energy

Tidal energy generation

Tidal Barrage

• There are many ways of harnessing tidal energy. One way is with Tidal Barrages.
• A Tidal Barrage is a huge dam that is build across an estuary. There are tunnels in the dam that water flows through as the tide goes in and out.
• The flow of tides through the dam turn a turbine which in turn generate electricity.

Wave energy generation

Pelamis P-750

• One popular way of generating electricity from wave energy is the Pelamis Machine Wave Energy Converter.
• This is a device that floats along the surface of the water and is anchored down on one end. The rolling motion of the waves is used to generate electricity.
• A hydraulic motor converts the wave motion to electricity by powering electrical generators.

​

*

Ocean Thermal Energy Conversion(OTEC)

• Ocean Thermal Energy Conversion(OTEC)is a process that can produce electricity by using the temperature difference between deep cold ocean water and warm tropical surface water.
• OTEC process uses temperature difference between cold deep water (5^◦C) & warm surface water (27^◦C) to power a turbine to generate electricity.

Types of OTEC systems:

1. Closed-cycle OTEC
2. Open-cycle OTEC
3. Hybrid OTEC

1. Closed –cycle OTEC

In this system, a low boiling fluid such as ammonia, to rotate a turbine to generate electricity. Warm surface seawater is pumped through a heat exchanger where the low-boiling-point fluid is vaporized. The expanding vapor turns the turbo-generator. Then, cold deep seawater pumped through a second heat exchanger condenses the vapor back into a liquid, which is then recycled through the system.

ii. Open –cycle OTEC:

• In this system, the sea water is itself used to generate heat without any kind of intermediate fluid.
• Open-cycle OTEC uses the tropical oceans warm surface water to make electricity. Warm sea water is made to boil and the produced steam drives the turbine attached to the electrical generator.

iii. Hybrid OTEC:

• A hybrid cycle combines the features of both the closed-cycle and open-cycle systems.
• In this system, warm sea water enters a vacuum chamber where it is evaporated into steam.
• The steam vaporizes the working fluid that drives a turbine to generate electricity.

Geothermal Energy

• Geothermal energy is a renewable and sustainable power source that comes from the heat generated by the earth.
• “Geo” means earth and “thermal” means heat.
• This thermal energy is contained in the rock and fluids beneath Earth’s crust.
• Geothermal Power Plant uses superheated water to generate electricity.
• Geothermal resources
• Reservoirs of steam or hot water
• Hot dry rock and magma
• Geothermal Hotspots

The areas in the world with the higher underground temperatures are regions with active volcanoes or Geologically young volcanic events.

Working of Geothermal Power Plant

• Hot water is pumped from deep underground through a well under high pressure.
• When the water reaches the surface, the pressure is dropped, which causes the water to turn into steam.
• The steam spins a turbine, which is connected to a generator that produces electricity.
• The steam cools off in a cooling tower and condenses back to water.
• The cooled water is pumped back into the Earth to begin the process again.

Biomass and Biofuel

Biomass is made up of living things(or things that were once living).This can include any plant or animal material, such as sugarcane, corn crops, wood chips or dung. All these type of biomass contain energy.

Sources of Biomass energy

​

​

​

Biomass energy production

Biomass feedstocks can be used to create both heat and electricity.

Biomass create heat by burning feedstocks.

Biomass can generate electricity in a number of ways- but the most

common is direct combustion. This means burning the agricultural

waste or wood to heat water. This produces steam, which spins

turbines.

Biofuels:

Biofuels are basically fuels that are made out of biomass. These can be

solid, liquid or gas.

Example : Biodiesel, Bioethanol, Biogas

​

​

HYDROGEN

THE ALTERNATIVE FUEL

• Due to the increase in dependency in non-renewable energy resources, there has been studies and interest in using a cleaner and more eco-friendly approach to consuming energy.
• One of the methods in obtaining clean energy is the utilization of hydrogen.
• Hydrogen is an abundant element on Earth and stands out from the rest of the renewable forms of energy.
• One kilogram of hydrogen is able to produce energy equivalent to a gallon of gasoline.
• Hydrogen is being used as fuel in increasing numbers of today’s motor vehicles which are expanding locally and internationally, with the goal to reduce carbon dioxide emissions.

​

Reasons to consider hydrogen as an alternative fuel:

• Zero emission on the roads
• High efficiency
• Fast filling time
• Hydrogen is non-polluting:

Hydrogen production

• Electrolysis
• Natural gas reforming (steam reforming)

This method is the cheapest, most efficient, and the most common way to extract hydrogen from hydrocarbons

especially methane.

It is a process of combining high temperature steam with natural gas.

​

​

​

​

​

​

In electrolysis, water molecule is split into two hydrogen and one oxygen atom using an electric current.

​

• Advantages
• Readily available
• Doesn’t produce harmful emissions
• Fuel efficient
• Can be used as fuel in rockets
• Renewable

• Disadvantages
• Expensive
• Explosive
• Difficult to store
• Highly flammable
• It is not easy to replace existing infrastructure
• It is dependent on fossil fuels
• Applications
• Hydrogen can be used to propel rockets and space shuttle
• Hydrogen can be combined with compressed natural gas to increase efficiency and reduce pollution
• Hydrogen is used in the construction and working of fuel cells
• It can also be used in cars, buses, submarines etc.

​

​

Nano Technology For Energy Sector

• Generating steam from sunlight : Sunlight concentrated on nanoparticles can produce steam with high energy efficiency.
• Producing high efficiency light bulbs : A nano-engineered polymer matrix is used in high efficiency light bulbs.
• Increasing the efficiency of windmills : An epoxy containing carbon nanotubes is being used to increase the amount of electricity generated by windmill.
• Generating electricity from waste heat :Sheets of nanotube could be wrapped around hot exhaust pipe of a car to generate electricity from heat that is usually wasted.
• Storing hydrogen for fuel cell powered cars : Graphene layers are used to increase the binding energy of hydrogen to the graphene surface in a fuel tank, resulting in a high amount of hydrogen storage.
• Clothing that generates electricity : Piezoelectric nanofiber is used to make cloth. The fibres can turn normal motion into electricity to power cell phone and other mobile electronic devices.
• Reducing friction : Lubricants using inorganic buckyballs can significantly reduce friction
• Reducing the cost of solar cells : Nano solar cells are inexpensive than conventional solar cells
• Reducing the cost of catalysts used in fuel cells : Platinum nanoparticles used instead of solid platinum to reduce the cost of catalysts used in fuel cells.

THANK YOU