Renewable Energy Sources

What is Renewable Energy? Renewable resources are natural resources that can

be replenished in a short period of time.

A renewable resource is a natural resource that can be re-made or re-grown at a scale comparable to its consumption

Nonrenewable / Fossil Fuels1. Coal2. Liquid Hydrocarbons- Petroleum (oil)3. Natural Gas

HOW ARE FOSSIL FUELS MADE ???

Coal, petroleum, and natural gas are considered nonrenewable because they can not be replenished in a short period of time

Why Renewable Energy?Conventional fuels are having high energy value, low cost, easily transportable etc.,But…

Why Renewable Energy?

Problems with Fossil Fuels Limited Supply- At projected consumption rates, natural

gas & petroleum will be depleted by the end of the 21st century

Global Warming - Burning fossil fuels produces large amounts of CO2, which is the main green house gas

Impurities are major source of pollution For e.g.; SO2 travels on air currents & falls with

precipitation as acid rainMakes one country rely on other countries for their

energy needs

RENEWABLE RESOURCES Solar Wind Biomass Water Geothermal OTEC Tidal and Wave

Solar Energy

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What is Solar Energy?

Energy produced by the sunClean, renewable source of energyHarnessed by solar collection methods such as solar cells, solar Collectors etc.Converted into usable energy such as electricity, heat etc.

Photovoltaic (solar) panel

Set of solar panels

Solar Energy Conversion Systems Solar Photovoltaic System – PV Cell

Solar Energy Electrical Energy Solar Thermal Energy Conversion SystemSolar Energy Thermal Energy

ORSolar Energy Thermal Energy Electrical Energy

Solar Photovoltaic System

© NASA/NREL

Solar cells (or photocells) turn light energy from the Sun directly into direct current electricity. Once the solar cell is built it produces no pollution and requires little maintenance.

This makes solar cells ideal for use in remote locations where maintenance is difficult and other sources of electricity would be expensive.

Solar cells

Solar cells suffer from a low efficiency. This is because only light with enough energy causes an electron to be released which is only about 25% (maximum) of all sunlight.

Producing enough electricity to power a town would require a very large area of solar panels but covering the roof of a house can meet the annual electricity needs of the household.

Efficiency of a solar cell

n-type semiconductor

p-type semiconductor

+ + + + + + + + + + + + + + + - - - - - - - - - - - - - - - - - -

Depletion Zone

Photo voltaic Cell

Photovoltaic System

Typical output of a module (~30 cells) is ≈ 15 V, with 1.5 A current

PV Technology Classification

Amorphous Silicon PV Cells Efficiency is less around 5% Makes 13% of PV market

Multi Crystalline PV Cells Efficiency is less around 10 to 15% Accounts for 90% of crystalline Si market

Mono Crystalline PV Cells Operating efficiency 20 to 25%

Applications of PV Water Pumping: PV powered pumping systems are excellent

,simple ,reliable – life 20 yrs Commercial Lighting: PV powered lighting systems are

reliable and low cost alternative. Security, billboard sign, area, and outdoor lighting are all viable applications for PV

Consumer electronics: Solar powered watches, calculators, and cameras etc.

Telecommunications Residential Power: A residence located more than a mile

from the electric grid can install a PV system more inexpensively than extending the electric grid (Over 500,000 homes worldwide use PV power as their only

source of electricity)

Solar Thermal Energy Conversion SystemsPassive SystemActive system (Solar Thermal Collectors)

Solar Thermal Collectors

• Non focussing Collectors (Flat plate collector)

• Focussing Collectors

• Line focussing

• Point Focussing

Flat Plate Collector

Solar water heater

Thermal storage

Steam power plant – a recap

Line focussing- parabolic Collector

© Warren Gretz/NREL© Warren Gretz/NREL

Point Focussing

© Bill Timmerman/NREL

Point Focussing

Solar power stations use the energy from the sun to heat water to make steam, which is then used to drive a turbine.

Some solar power stations use a series of mirrors called heliostats to reflect light onto a boiler.

Solar power stations

© Sandia National Laboratory/NREL

Other Solar devicesSolar StillSolar Air HeaterSolar Water PumpSolar CookerSolar dryer

Solar still

WIND ENERGY

Uneven heating of earth’s surface and rotation

Turbine Evolution

Used for Pumping water Grinding grain

Mainly used for Generating Electricity

Types of turbinesVAWT – Vertical Axis Wind Turbine

Drag is the main force

Nacelle is placed at the bottom

Yaw mechanism is not required

Lower starting torque

Difficulty in mounting the turbine

Unwanted fluctuations in the power output

HAWT – Horizontal Axis Wind Turbine

Lift is the main force

Much lower cyclic stresses

95% of the existing turbines are

HAWTs

Nacelle is placed at the top of the tower

Yaw mechanism is required

Two types of HAWTDOWNWIND TURBINE

UPWIND TURBINE

A Typical HAWT

Offshore turbines – coastal development

Offshore turbines

More wind speeds

Less noise pollution

Less visual impact

Difficult to install and maintain

Energy losses due long distance transport

Disc type wind turbineMuch more efficient than HAWT

Requires less height

Low noise

Works in any wind direction

BIOMASS

Biomass Sources

Direct combustion

Thermo chemical

Gasification

Pyrolysis

Bio Chemical Conversion

Digestion

Fermentation

Conversion of Biomass

Solid Fuel Combustion Biomass was the first fuel

mankind learned to use for energy, Burning wood for warmth and cooking

Direct combustion of solid matter where the biomass is fed into a furnace where it is burned. The heat is used to boil water and the energy in the steam is used to turn turbines and generators.

Animal Dung

Wood

Gasification A process that uses heat, pressure, and steam to convert materials directly into a gas composed primarily of carbon monoxide and hydrogen.

GasificationTypical raw materials - coal, petroleum-based

materials, and organic materials.

The feedstock is prepared and fed, in either dry or slurried form, into a sealed reactor chamber called a gasifier.

The feedstock is subjected to high heat, pressure, and either an oxygen-rich or oxygen-starved environment within the gasifier.

Pyrolysis Heat is used to chemically convert

biomass to Gaseous liquid and solid fuels.

Biomass is heated to 500oC to 900 oC in a closed vessel in the absence of Oxygen

Pyrolysis can perform almost all form of organic materials

Digestion Decomposition of organic matter by anaerobic bacteria in an oxygen-starved environment.

Anaerobic digesters compost (or “digest”) organic waste in a machine that limits access to oxygen encouraging the generation of methane and carbon dioxide by microbes in the waste. This digester gas is then burned as fuel to make electricity.

Digestion

Fermentation Unlike other renewable energy sources, biomass

can be converted directly into liquid fuels— bio-fuels— for our transportation needs (cars, trucks, buses, airplanes, and trains)

The two most common types of bio-fuels are ethanol and bio-diesel

Ethanol – An additive to gasoline

Bio-diesel - made by combining alcohol with vegetable oil, animal fat etc.

Hydropower

Water power• Converts Potential

energy of water to mechanical energy and then to electrical energy

• One of the main source of energy after conventional energy

• In india, approximately 22% of energy is from hydel power

Water power

Water power- working of turbine

Impulse Turbine (Pelton Wheel) High Head, Low discharge

Mixed flow Reaction Turbine (Francis Turbine) Medium Head, Medium discharge

Axial flow Reaction Turbine (Kaplan Turbine ) Low Head, High discharge

Water Turbines

GEOTHERMAL ENERGY

Steam power plant – a recap

Geothermal

• The thermal energy contained in the interior of earth is called Geothermal Energy• Use heat to make steam

which rotatesturbine for electrical generation

Geothermal Energy

Ocean Thermal Energy Conversion (OTEC)

MAIN COMPONENTS OF AN OTEC SYSTEM

The temperature at the top of sea and that at the bottom of sea has a temperature difference of 20 degrees

A steam power cycle is operated between the top surface (the source) and the bottom of the sea (sink)

Working of OTEC plant

1. Open cycle

Water is the working fluid Desalinated water can be produced

2. Closed cycle

Ammonia can be used as a working fluid

Tidal and Wave Energy

Wave Energy

Wave Energy Conversion

Wave Energy Conversion

Tidal PowerNo dam, but a turbine alone is needed for energy conversion

Tidal Energy

Renewable energy resources are the only solution for a sustainable world

Solar energy is clean energy which makes no pollution, no harm to environment

In remote areas, the only solution for energy is solar power Most of the Renewable energy resources are pollution free

and nature friendly Solar, Biomass, Hydel and Wind energy has very good

potential and they are the fastest growing renewable energy sources

Conclusions

Conclusions (contd..) The future looks bright for Renewable energy because

technology is becoming more advanced and efficient Initial Cost is high (Cost may not be a factor in many

occasion..!) intermittent supply

Energy storage equipments are needed Must be coupled with other sources of electricity

It is best suited if using as a hybrid energy source

Save energy, save earth

Thank you