8th Indo-German Winter Academy
Combined Solar and Thermal Power generation.
What does it bring for the future?
Presented by:
Rachit Khare
B.Tech Chemical Engineering
Indian Institute of Technology Roorkee
Tutor:
Prof. Dr. Dr. h.c. F. Durst
FMP TECHNOLOGY GMBH
OUTLINE
o Solar Energy
o Solar Thermal Power Plants
o Solar Photovoltaic Power Plants
o Hydro Energy
o Hydro Power
o Tidal Energy
o Wave Energy
o Ocean Thermal Energy Conversion (OTEC)
o Other Renewable Energy Resources
o Wind Energy
o Geothermal Energy
o Biomass and biofuels
o Nuclear Energy
o Sustainability by combining nuclear, fossil, and renewable energy sources
Rachit Khare (IIT Roorkee)
Renewable Energy
December 18th 2009
2
SOLAR ENERGY
o Basic Principles
o Exergy Analysis
o Solar Thermal Power Plants
o Basic Principles and Applications
o Thermodynamics – Energy & Exergy Analysis
o Solar Photovoltaic Plant
o Basic Principles and Applications
o Thermodynamics – Energy & Exergy Analysis
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Renewable Energy
December 18th 2009
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Solar Energy
Basic Principles
Basic Principles - Exergy Analysis
Exergy analysis is a technique that uses the conservation of mass and conservation of
energy principles together with the second law of thermodynamics for the analysis, design
and improvement of energy and other systems.
 Exergy is defined as the maximum amount of work which can be produced by a
system or a flow of matter or energy as it comes to equilibrium with a reference
environment.
 Unlike energy, exergy is not subject to a conservation law (except for ideal, or
reversible, processes). Rather exergy is consumed or destroyed, due to
irreversibilities in any real process.
 The exergy consumption during a process is proportional to the entropy created
due to irreversibilities associated with the process.
 Exergy is a measure of the quality of energy which, in any real process, is not
conserved but rather is in part destroyed or lost.
 For exergy analysis, the characteristics of a reference environment must be
specified. This is commonly done by specifying the temperature, pressure and
chemical composition of the reference environment.
 “The exergy of a system is zero when it is in equilibrium with the reference
environment.”
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Renewable Energy
December 18th 2009
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Solar Energy
Basic Principles
Energy and Exergy Balances
Energy and exergy balances for a flow of matter through a system can be expressed as
The chemical energy
is the maximum
work obtainable
from the flow as it is
brought from the
environmental state
to the dead state.
Since min = mout = 0 for a closed systems,
The specific exergy of a flow of matter can be expressed as:
Often, ke = 0 and pe = 0 and physical energy is the maximum available work from the flow
as it is brought to the environmental state.
The exergy consumed due to irreversibilities during a process is,
Rachit Khare (IIT Roorkee)
Renewable Energy
December 13th 2009
5
Solar Energy
Solar Thermal Power Plants
Solar Thermal Power Plants – An Introduction
Solar Thermal Energy is a technology for harnessing solar energy for thermal energy (heat).
Solar thermal collectors are defined by the USA Energy Information Administration as
 Low-temperature collectors
Low temperature collectors are flat plates generally used to heat swimming
pools.
 Medium-temperature collectors
Medium-temperature collectors are also usually flat plates but are used for
creating hot water for residential and commercial use.
 High-temperature collectors
High temperature collectors concentrate sunlight using mirrors or lenses and are
generally used for electric power production.
“While only 600 MW of solar thermal power is up and running worldwide
in October 2009 other 400 MW is under construction and there are 14,000 MW of
serious concentrating solar thermal (CST) projects being developed.”
Rachit Khare (IIT Roorkee)
Renewable Energy
December 13th 2009
6
Solar Energy
Solar Thermal Power Plants
System Description
Solar Thermal Power Systems can be
considered as consisting of two subsystems:1. Collector-receiver Subsystem
2. Heat engine Subsystem
Fig 3: Solar Thermal System Sketch
Collector-receiver circuit
• The collector-receiver circuit consists of a number of parabolic trough collectors
arranged in modules.
Heat engine circuit
• The heat engine circuit consists of a heater (here the boiler heat exchanger), a
turbine having two stages, a condenser, pump and a regenerator.
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Renewable Energy
December 18th 2009
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Solar Energy
Solar Thermal Power Plants
Energetic Analysis of a Solar Thermal System
Energy Analysis: Collector-receiver Circuit
Collector Subsystem
• Energy received by the collector system is
• Energy absorbed by the collector absorber is Qs, therefore,
First law efficiency,
Receiver Subsystem
• Useful energy delivered to the fluid in the receiver, Qu,
• Energy Loss
• First Law Efficiency,
• Overall efficiency of the collector-receiver subsystem,
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Renewable Energy
December 18th 2009
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Solar Energy
Solar Thermal Power Plants
Energetic Analysis of a Solar Thermal System
Energy Analysis: Heat Engine Subsystem
Heat Engine Subsystem
• Energy received by the working Fluid of the
heat engine, Qh,
Assumption:
There is no loss of heat in the heat
exchanger
• Net work done by the heat engine cycle,
Wnet,
• Energy Loss,
• First Law Efficiency,
• Overall energy efficiency of the Solar
Thermal Power system,
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Fig 5: T-S Diagram
December 18th 2009
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Solar Energy
Solar Thermal Power Plants
Exergetic Analysis of a Solar Thermal System
Exergy Analysis: Collector-receiver Circuit
Collector Subsystem
• Exergy received by the collector, Exi,
• Exergy absorbed by the collector absorber, Exc,
• Exergy Loss = Irreversibility (IR1)
• Second law efficiency,
Receiver Subsystem
• Useful exergy delivered, Exu,
• Exergy Loss = Irreversibility (IR2)
• Second law efficiency,
• Overall second law efficiency of the collector-receiver circuit,
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December 18th 2009
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Solar Energy
Solar Thermal Power Plants
Exergetic Analysis of a Solar Thermal System
Exergy Analysis: Heat Engine Subsystem
Heat Exchanger
• Useful exergy delivered by the thermic fluid, Exu,
• Exergy available to the working fluid of the heat engine cycle
• Exergy Loss in heat exchanger = Irreversibility (IRhx)
• Second law efficiency of the heat exchanger,
Heat Engine Cycle
• Exergy available to the working fluid of the heat engine cycle circuit, Exu1 = Exn
• Exergy Output = Net work done by the heat engine
• Exergy transferred to the cooling medium in the condenser
• Exergy Loss = Irreversibility (IRhe)
• Second law efficiency of the heat engine,
• Overall second law efficiency of the Solar Thermal Power system,
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Renewable Energy
December 18th 2009
11
Solar Energy
Solar Photovoltaic Power Plants
Solar Photovoltaic Power Plants – An Introduction
 Solar photovoltaics (PVs) are arrays of cells containing a material that converts solar
radiation into direct current electricity.
 Materials presently used for photovoltaics include amorphous silicon, polycrystalline
silicon, microcrystalline silicon, cadmium telluride, and copper indium
selenide/sulfide.
 A photovoltaic system is a system which uses solar cells to convert light into
electricity.
 A photovoltaic system consists of multiple components, including cells, mechanical
and electrical connections and mountings and means of regulating and/or modifying
the electrical output.
Fig 10a: A PV Solar Cell
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Fig 10b: A Photovoltaic Array
December 13th 2009
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Solar Energy
Solar Photovoltaic Power Plants
Thermodynamic Analysis - Physical Energy
Physical Energy
• Change in the enthalpy of the system
• The total entropy of the system
• Thus, the total physical exergy for a PV cell system,
EGH = highest energy
content of the electron
Voc
Vm
Voltage (V)
For solar PV cells, efficiency measures the ability
to convert radiative energy into electrical energy.
• Vm, Im – Voltage and current at max power
output point
• Voc = open-circuit Voltage
• Isc = short-circuit Current
Maximum power conversion efficiency of a PV
device:
EL = low energy content
of the electron
Current (A)
Im Isc
December 18th 2009
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Fig 11: General I-V curve and its parameters
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Renewable Energy
Solar Energy
Solar Photovoltaic Power Plants
Chemical Energy
Thermodynamic Analysis - Chemical Energy
• In general, the process of PV energy conversion can be divided into two steps:
• Electronic excitation of the absorbing component of the converter by light
absorption with concomitant electronic charge creation. The excitation can be an
electron-hole pair in a semiconductor, an electronic excitation of a molecule.
• Separation of the electronic charges
Electronic excitation in the absorber promotes
the system into:
• The highest energy content with associated
electronic energy level, H.
• Simultaneously creating an electrondeficient, the low-energy content with
associated energy level, L.
The departure of the populations of the states
from their thermal equilibrium values implies a
difference in their chemical potentials (partial
free energies)
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Fig 12: An idealized photovoltaic converter
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December 18th 2009
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Solar Energy
Solar Photovoltaic Power Plants
Total Energy of a PV Solar Cell
Chemical Energy
• The separation of Fermi levels arises as a result of the absorber at a lower ambient
temperature, Tamb than the radiation temperature, Tp. Carnot cycle argument gives
the following upper limit chemical potential for the open-circuit voltage:
EGH = generated electricity at the highest energy content of the electron
EL = available energy content of the electron (as the practical case).
• Further simplifying by taking EGH’s curved area as rectangular one, based upon the
Carnot cycle analogy:
Total Energy of a PV solar cell
• Maximum power can be generated in a PV cell system at nearly open-circuit voltage
and short-circuit current. But from a thermodynamic perspective, the unconsidered
remaining components should be extracted from the overall I–V curve.
• Thus, the total exergy of the PV solar cell can be formulated as:
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Renewable Energy
December 18th 2009
15
Solar Energy
Solar Photovoltaic Power Plants
Energy and Exergy Efficiency
Solar cell power conversion efficiency, ηpce,
St = hourly measured total solar irradiation
The exergy of solar irradiance, Exsolir, can be evaluated approximately from,
Exergy efficiency, ψ, could be represented as,
The energy efficiency is defined dependent on the generated electricity of PV cells, Egen,
and total energy input given by the measured total solar irradiation, St.
Rachit Khare (IIT Roorkee)
Renewable Energy
December 18th 2009
16
HYDRO ENERGY
o Hydro Energy
o Wave Energy
o Tidal Energy
o Ocean Thermal Energy Conversion (OTEC)
o Areas Covered:
o Basic Principles and Applications
o Advantages, Limitations and Challenges Faced
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Renewable Energy
December 18th 2009
17
Hydro Energy
Hydro Power
Hydro Power
Most established and widely used renewable resource for electricity generation
Accounts for about 20% of world’s electric generation
In at-least 20 countries it accounts for 90% of the total electric supply e.g. Brazil
Power generation efficiency can be as high as 80-90%
Term hydro power is usually restricted to generation of shaft power from falling water.
Hydro turbines have rapid response for
power generation and so the power
may be used to supply both baseload
and peak demand requirements.
 Turbines are of two types:
• Reaction turbines; totally
embedded in fluid; power is
derived from pressure drop across
the device
• Impulse turbines; flow hits the
turbine as a jet, power is derived
from the kinetic energy of the
flow
Fig 17: Net exploitable hydropower potential TWh/annum






and percentage exploited
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December 18th 2009
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Hydro Energy
Hydro Power
Basic Principles
 Useful power available – from Bernoulli’s theorem:
 Effective power generated at the input of the turbines:
ηt – Simplified Turbine Efficiency ( ≈ 0.80 for most of the cases)
Ha – Available Water Head = Geometric Head – Head loss due to friction
Turbines: Forces and Power generated
• Potential energy of water – Kinetic energy of blades of the turbine
uc = velocity of the cup
• Force experienced by the cup:
ui = velocity of the input jet
• Power transferred to the cup:
• Q j is the volumetric flow rate through the jet
• Maximum power transferred to the cup:
• Therefore an ideal turbine has a 100 % efficiency
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Renewable Energy
December 13th 2009
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Hydro Energy
Hydro Power
Advantages & Disadvantages
Advantages
•
•
•
•
Elimination of the cost of fuel
Operating labor cost is also usually low – automated plants
Dam serves multiple purposes – Multi purpose river valley projects
Hydroelectricity produces the least amount of greenhouse gases and externality of
any energy source
Disadvantages
• The use of hydropower depends upon large difference in elevation that exists only
in some parts of the world
• Dam failures can be catastrophic: Lead to loss of lives and large power outages.
• Where the reservoir is large compared to the generating capacity (less than 100 watts
per square meter of surface area) and no clearing of the forests in the area was
undertaken prior to impoundment of the reservoir, greenhouse gas emissions from
the reservoir may be higher than those of a conventional oil-fired thermal
generation plant
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Renewable Energy
December 18th 2009
20
Hydro Energy
Ocean Thermal Energy Conversion
Ocean Thermal Energy Conversion
 Oceans are the world’s largest solar energy collector and energy storage systems.
 OTEC, or Ocean Thermal Energy Conversion, is an energy technology that converts solar
radiation to electric power.
 In tropical seas, temperature differences of about 20-25 °C may occur between the
warm, solar-absorbing near-surface water and cooler “deep” water (at a depth of about
500-1000 m)
 OTEC systems use ocean's natural thermal gradient to drive a power-producing cycle.
 Small magnitude of the temperature
difference
low thermal efficiency.
 Maximum theoretical efficiency lies
between 6-7 %.
 The only heat cycle suitable for OTEC, is
the Rankine Cycle, using a low pressure
turbine.
 Systems may either be closed-cycle
(using refrigerants like ammonia or R134a) or open-cycle (sea water as the
working fluid)
Fig 17: Temperature difference between surface and depth
of 1000 m
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December 18th 2009
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Hydro Energy
Ocean Thermal Energy Conversion
Basic Principles
 Ideal system with perfect heat exchangers.
 Power given up from the warm water, P0,
 According to the II law of thermodynamics,
maximum output of work energy
obtainable E1from heat input E0,
 ηcarnot is the efficiency of an Ideal Carnot
engine,
Fig 17: Schematic Diagram of an OTEC system
 As ∆T is only ≈20 °C, therefore, ηcarnot is only about ≈7 %.
 The efficiency of the real systems is low at about 2-3 % with temp drop across the heat
exchanger being only about 5 °C.
 The ideal mechanical output power is
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December 18th 2009
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Hydro Energy
Ocean Thermal Energy Conversion
General Analysis
Heat Exchangers
• A temperature difference of δT is required to drive heat flow across the conductive
resistances of the heat exchanger.
• Let Pwf be the heat transfer from the water to the working fluid, then
Rwf is the thermal resistance between the water and the fluid
• Assuming a similar temperature drop in the other heat exchanger, the temperature
difference available to drive the heat engine is
• Therefore the mechanical power output would be
• To increase the power output, It is crucial to minimize the transfer resistance, Rwf, by
making the heat exchanger as efficient as possible.
• If rwf is the resistivity and Awf is the total wall area, then
• Much of the development work in OTEC concerns improvements in the design of the
heat exchangers. Aim is to decrease rwf, and thereby to decrease the Awf.
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Renewable Energy
December 18th 2009
23
Hydro Energy
Ocean Thermal Energy Conversion
Applications & Challenges
Applications of OTEC
•
•
•
•
•
Helps produce fuels such as hydrogen, ammonia, and methanol
Produces base-load electrical energy
Produces desalinated water for industrial, agricultural, and residential uses
Is a resource for on-shore and near-shore mariculture operations
Has significant potential to provide clean, cost-effective electricity for the future.
Challenges
• Due to quadratic dependence on the temperature, experiments have shown that
only sites with ∆T > 20 °C are economically possible.
• Substantial flow is required to give a reasonable output
• Biofouling: The inside of the pipe is vulnerable to encrustation by marine organisms,
which increases the resistance to heat flow.
• There are many common fluids having an appropriate boiling point, e.g. ammonia,
freon, etc, but many of these are environmentally unacceptable
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Renewable Energy
December 18th 2009
24
Hydro Energy
Tidal Power
Tidal Power
 The level of water in the large oceans of the earth rises and falls according to
predictable patterns.
 The main time periods τ of these tides are diurnal at about 24 h and semidiurnal at
about 12 h 25 min.
 The change in the height between successive high and low tides as the range, R.
 This varies between about 0.5 m in general and about 10 m at particular sites near
continental land masses.
 The movement of water produces tidal currents which may reach speeds of 5 m/s in
coastal and inter island channels.
 There are two ways of utilizing the tidal
power:
• Tidal Barrage methods
• Tidal Current Technology
 World tidal power potential is
estimated to be 3000 GW.
 Only less than 3 % is located in areas
suitable for power generation.
Fig 17: Major world tidal power potential sites
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December 18th 2009
25
Hydro Energy
Tidal Power
Basic Principles
There are two fundamentally different approaches to the exploitation of tidal energy.
Tidal Barrage Methods
• An estuary or bay with a large natural tidal range is identified and then artificially
enclosed with a barrier
• The electrical energy is produced by allowing water to flow from one side of the
barrage, through low-head turbines, to generate electricity.
• Seawater is trapped at high tide in an estuarine basin of area A and is allowed to run
through the turbines at low tide. Average power produced is
There are variety of suggested modes of operation:
• Single basin tidal barrage schemes
• Ebb generation mode
• Flood generation mode
• Two way generation
• Double basin generation
•
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Fig 25: Single basin tidal barrage schemes
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December 13th 2009
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Hydro Energy
Tidal Power
Basic Principles
Tidal Current Technology
• Utilizes the kinetic energy in flowing tidal currents
• The physics of the conversion of energy from tidal currents is superficially very
similar, in principle, to the conversion of kinetic energy in the wind
• Energy available in the tidal currents: The kinetic energy flux in moving water when
accessing available energy is given by:
• Actual potential of a site to deliver energy is a more complex relationship involving
understanding of the nature of the total flow environment
• For ocean current energy to be utilized successfully at a commercial scale, a number
of potential technical challenges need to be addressed, including:
• avoidance of cavitations (bubble formation)
• prevention of marine growth buildup
• reliability (since maintenance costs are potentially high)
• corrosion resistance
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Renewable Energy
December 13th 2009
27
Hydro Energy
Tidal Power
Advantages & Limitations
Advantages
• The most important advantage of tidal energy is its economical benefits, as tidal
energy does not require any fuel
• Free from pollution
• The economic life of a tidal plant is very high.
• Do not damage large areas of valuable land
• Peak power demands can be effectively met when it works in combination with
thermal or hydroelectric system.
Challenges & Limitations
• The high capital costs associated with tidal barrage systems are likely to restrict
development of this resource in the near future
• Technology is yet not developed fully and hence construction of efficient, cheap and
strong conversion device is a bit problematic.
• Location is also one of the major problems as appropriate tides are not found
everywhere.
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December 18th 2009
28
Hydro Energy
Wave Power
Wave Power
 Sea wave energy has the highest concentration of renewable energy.
 Ocean waves are created by the interaction of wind with the surface of the sea.
 The amount of energy transferred and hence the size of the resulting waves, depends
on the wind speed, the length of time for which the wind blows and the distance over
which it blows.
 Waves with power levels of in excess of 100 kW/m of wave crest length can be created
in certain locations.
 Waves continue to travel in the
direction of their formation even after
the wind dies down.
 In deep water, waves lose energy very
slowly, so they can travel enormous
distances from their point of origin
with minimal power loss
 Wave-power rich areas of the world
include the western coasts of Scotland,
northern Canada, southern Africa,
Fig 17: Average annual wave power levels as kW/m
Australia.
of wave front
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December 18th 2009
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Hydro Energy
Wave Power
Basic Principles
Wave energy and wave energy flux
• The average energy density per unit area of gravity waves on the water surface is
proportional to the wave height squared, according to linear wave theory
• E is the mean wave energy density per unit horizontal area (J/m2); the sum of kinetic
and potential energy density per unit horizontal area
• Hm0 is the significant wave height and is four times the standard deviation of the
water surface elevation.
• As a result, the wave energy flux, through a vertical plane of unit width perpendicular
to the wave propagation direction, is equal to:
• cg the group velocity (m/s) or the energy transport velocity
• In deep water where the water depth is larger than half the wavelength, the wave
energy flux is
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December 13th 2009
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Hydro Energy
Wave Power
Advantages & Challenges
Advantages
• The energy is free - no fuel needed, no waste produced.
• Not expensive to operate and maintain.
• Wave energy is predictable; Satellites can measure waves out in the ocean one to two
days in advance of their impact on coastal location
• Offshore wave energy has the potential to be one of the most environmentally
benign forms of electricity generation
Challenges
• Capturing a reasonable fraction of the wave energy in irregular waves, in a wide
range of sea states.
• Constructing devices that can survive storm damage and saltwater corrosion.
• Efficiently converting wave motion into electricity; wave power is available in lowspeed, high forces, and the motion of forces is not in a single direction.
• Extremely large fluctuation of power in the waves. The peak absorption capacity
needs to be much (more than 10 times) larger than the mean power.
• Positive or negative impacts on marine habitat.
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December 18th 2009
31
OTHER RENEWABLE ENERGY
RESOURCES
o Wind Energy
o Geothermal Energy
o Biomass and Biofuels
o Areas Covered:
o Basic Principles and Applications
o Advantages, Limitations and Challenges Faced
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December 18th 2009
32
Other Renewable Energy Resources
Wind Energy
Wind Energy
 The Earth is unevenly heated by the sun, such that the poles receive less energy from
the sun than the equator; along with this, dry land heats up (and cools down) more
quickly than the sea.
 The differential heating drives a global atmospheric convection system reaching from
the Earth's surface to the stratosphere which acts as a virtual ceiling.
 Wind power is the conversion of wind energy into a useful form of energy.
 In a wind farm, individual turbines are interconnected with a medium voltage (usually
34.5 kV) power collection system and communications network.
 To be worthwhile, an average wind speed of around 25 km/h is required.
 The best places for wind farms
are in coastal areas, at the tops
of rounded hills, open plains and
gaps in mountains. Some are
offshore.
 An estimated 72 TW of wind
power on the Earth potentially
can be commercially viable.
Fig 32: World wind energy potential Sites
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Other Renewable Energy Resources
Wind Energy
Basic Principles
A column of wind passing upstream to the turbine has KE passing per unit time, Po,
Power extracted from the wind, PT,
The power coefficient, Cp, is the fraction of power extracted by the turbine;
when a = 1/3
The interference factor, a, is the fractional wind speed decrease at the turbine.
There are two extreme theoretical conditions of operation:
• Variable rotor speed for constant tip-speed ratio, λ, hence constant Cp. This is the most
efficient mode of operation and captures the most energy.
•
Constant (fixed) turbine rotational frequency, hence varying Cp. Although less efficient
than variable speed turbines, the use of standard induction generators allows easy grid
connection.
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December 18th 2009
34
Other Renewable Energy Resources
Wind Energy
Advantages & Disadvantages
Advantages
• Wind is free, wind farms need no fuel.
• Wind Power Plants do not produce any pollution or waste products and do not
contribute towards the greenhouse effect.
• The land beneath can usually still be used for farming.
• A good method of supplying energy to remote areas.
• Very less maintenance required.
Disadvantages
•
•
•
•
•
•
The wind is not always predictable - some days have no wind.
Suitable areas for wind farms are often near the coast, where land is expensive.
Noise pollution
Effect on the ecosystem: killing of birds.
Wind Farms are Unsightly.
Wind Turbines interfere with Television Reception and radio signals
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December 18th 2009
35
Other Renewable Energy Resources
Geothermal Energy
Geothermal Energy
 Geothermal energy is the natural heat of the earth.
 The inner core of earth reaches a maximum temperature of about 4000 °C.
 Heat passes out through the solid submarine and the land surface mostly by conduction
– geothermal heat – and occasionally by active convective currents of molten magma
or heated water.
 The Average Geothermal Heat Flow at the earth’s surface is only about 0.06 W/m2.
 At certain specific locations increase temperature gradients occur, indicating significant
geothermal resources.
 There are four major geothermal
resources:
• Hydrothermal Energy
• Geo-pressurized brines
• Hot dry rocks
• Magma
 Only hydrothermal energy is widely
used to generate electricity.
Fig 21: Potential sites for Geothermal power generation
across the world
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December 18th 2009
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Other Renewable Energy Resources
Geothermal Energy
Basic Principles
There are three classes of geothermal energy:
 Hyper-thermal: Temperature gradient > 80 °C/km. These regions are usually on tectonic
plate boundaries.
 Semi-thermal: Temperature gradient 40-80 °C/km. Such regions are associated generally
with anomalies away from plate boundaries. Heat extraction is from harnessing natural
aquifers or fracturing dry rock.
 Normal: Temperature gradient < 40 °C/km. Unlikely for energy production economically.
Geothermal power plant
• To harness the energy, deep holes are drilled
into the earth until a significant geothermal hot
spot is found.
• When the heat source has been discovered, a
pipe is attached deep down inside the hole
which allows hot steam from deep within the
earths crust to rise up to the surface.
• The pressurized steam is then channeled into a
turbine which begins to turn under the large
force of the steam.
• The turbine is connected to a generator which
produces electricity
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Fig 36: A typical geothermal power plant
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December 13th 2009
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Other Renewable Energy Resources
Geothermal Energy
Advantages & Disadvantages
Advantages
• There is also no consumption of any type of fossil fuels.
• Geothermal energy does not produce any pollution and does not contribute towards
the greenhouse effect.
• After the construction of a geothermal power plant, there is little maintenance to
contend with.
• In terms of energy consumption, a geothermal power plant is self-sufficient.
• Power plants do not have to be huge which is great for protecting the natural
environment.
Disadvantages
• The big problem is that there are not many places where a geothermal power
station can be built.
• Hazardous gases and minerals may come up from underground, and can be
difficult to safely dispose of.
• It is also possible for a specific geothermal area to run dry or lose steam.
Rachit Khare (IIT Roorkee)
Renewable Energy
December 18th 2009
38
Other Renewable Energy Resources
Biomass and Biofuels
Biomass
 The material of plants and animals, including their wastes and residues, is called
biomass.
 It is organic, carbon-based, material that reacts with oxygen in combustion and natural
metabolic processes to release heat.
 The initial material may be transformed by chemical and biological processes to
produce biofuels e.g. methane, ethanol, methyl esters, etc.
 The initial energy of the biomass oxygen system is captured from solar radiation in
photosynthesis.
 Biomass is sustainable and generally carbon neutral because the carbon released in the
combustion process is offset by the carbon trapped in the organic matter by
photosynthesis during its growth.
 To be truly carbon-neutral we need to make sustainable use of plants or trees as fuel,
and replant them as we harvest them - so that the carbon is reabsorbed in a continuous
and virtuous cycle.
 Bioenergy is renewable energy made available from materials derived from biological
sources.
Rachit Khare (IIT Roorkee)
Renewable Energy
December 18th 2009
39
Other Renewable Energy Resources
Biomass and Biofuels
Biofuels
 Broadly speaking, biofuel refers to any solid, liquid or gas fuel that has been derived
from biomass.
 One of the main challenges when producing biofuel is to develop energy that can be
used specifically in liquid fuels for transportation
 First generation biofuels
First-generation biofuels are biofuels made from sugar, starch, vegetable oil, or animal
fats using conventional technology. E.g. bioalcohols, biodiesel, bioethers, biogas, syngas
and solid biofuels.
 Second generation biofuels
Second generation biofuels use biomass to liquid technology, including cellulosic
biofuels from non food crops.Many second generation biofuels are under development
such as biohydrogen, biomethanol, DMF, Bio-DME, Fischer-Tropsch diesel, biohydrogen
diesel, mixed alcohols and wood diesel.
 Third generation biofuels
Third generation biofuel is biofuel from algae. Algae are low-input, high-yield feedstock
to produce biofuels. Based on laboratory experiments, it claimed that Algae can
produces up to 30 times more energy per acre than land crops
 Second and Third generation bioguels are also called advanced biofuels
Rachit Khare (IIT Roorkee)
Renewable Energy
December 13th 2009
40
Other Renewable Energy Resources
Biomass and Biofuels
Advantages & Disadvantages
Advantages
• Theoretically inexhaustible fuel source
• When direct combustion of plant mass is not used to generate energy (i.e.
fermentation, pyrolysis, etc. are used instead), there is minimal environmental impact
• Fuels produced by biomass are efficient, viable, and relatively clean-burning
• Available throughout the world
Disadvantages
•
•
•
•
Could contribute a great deal to global warming and pollution if directly burned.
Still an expensive source, both in terms of production and conversion to alcohols.
On a small scale there is most likely a net loss of energy.
Non-sustainable biofuel production – Many first generation biofuels are not
sustainable
• The food V fuel debate - Another concern is that if biofuels become lucrative for
farmers, they may grow crops for biofuel production instead of food production.
Rachit Khare (IIT Roorkee)
Renewable Energy
December 18th 2009
41
NUCLEAR ENERGY
o An Introduction
o Basic Principles
o Nuclear Reactors
o Boiling Water Reactor
o Pressurized Water Reactor
o Nuclear Fuel Cycle
o Internal and External Factors impacting Nuclear Power
Generation
Rachit Khare (IIT Roorkee)
Renewable Energy
December 18th 2009
42
Nuclear Energy
An Introduction
Nuclear Energy
 Nuclear power is power produced from
controlled nuclear reactions. Commercial plants
in use to date use nuclear fission reactions.
 As of 2005, nuclear power provided 2.1% of the
world's energy and 15% of the world's
electricity.
 In 2007, the IAEA reported there were
439 nuclear power reactors in operation in the
world, operating in 31 countries.
Fig 41a: Nuclear Power Capacity and Generation
Operating reactors, building new reactors
Operating reactors, planning new build
No reactors, building new reactors
No reactors, planning new build
Operating reactors, stable
Operating reactors, considering phase-out
Civil nuclear power is illegal
No reactors
Fig 41b: The status of nuclear power globally
Rachit Khare (IIT Roorkee)
Renewable Energy
December 18th 2009
43
Nuclear Energy
Basic Principles
Basic Principles
 Nuclear energy is released by the splitting (fission) or merging together (fusion) of the
nuclei of atom(s).
 The conversion of nuclear mass to energy is consistent with the mass-energy
equivalence formula
 Nuclear energy is released by three exoenergetic (or exothermic) processes:
• Radioactive decay, where a neutron or proton in the radioactive nucleus decays
spontaneously by emitting either particles, electromagnetic radiation (gamma
rays), neutrinos (or all of them).
• Fusion, two atomic nuclei fuse together to form a heavier nucleus.
• Fission, the breaking of a heavy nucleus into two (or more rarely three) lighter
nuclei.
 It is often claimed that nuclear stations are inflexible in their output, implying that
other, typically fossil stations would be used to meet peak demand. Whilst it may have
been true for certain reactors, this is not longer true of at least some modern designs.
 The economics of nuclear power plants are primarily influenced by the high initial
investment necessary to construct a plant.
Rachit Khare (IIT Roorkee)
Renewable Energy
December 18th 2009
44
Nuclear Energy
Nuclear Power Plant
Nuclear Reactors
Classification of Nuclear Reactors
• Type of fuel used:
•
•
Natural Fuel Type
Enriched Fuel Type
• Type of coolant used:
•
•
•
Water Cooled Reactors
Gas Cooled Reactors
Liquid Metal Cooled Reactors
• Type of moderator used:
•
•
•
Ordinary water moderated reactors
Heavy Water moderated reactors
Graphite moderated reactors
• Type of core:
•
•
Homogeneous Reactors
Heterogeneous Reactors
• As per neutron energy:
•
•
Fast Reactors
Thermal Reactors
Rachit Khare (IIT Roorkee)
Renewable Energy
December 18th 2009
45
Nuclear Energy
Nuclear Power Plant
Nuclear Reactors
Fig 44a: Boling water reactor (BWR)
•
•
•
•
•
Fig 44b: Pressurized water reactor (PWR)
In the BWR, steam is provided directly
from the reactor
Inlet temperature: 278 C
Outlet temperature: 288 C
Pressure: 72 bar
The boiling water reactor is a major
alternative to the PWR and both are used
Rachit Khare (IIT Roorkee)
•
•
•
•
•
The water in the reactor vessel is
maintained in liquid form by high pressure
Inlet temperature: 292 C
Outlet temperature: 325 C
Pressure: 155 bar
The pressurized water reactor accounts
for almost two-thirds of all capacity.
Renewable Energy
December 13th 2009
46
Nuclear Energy
Nuclear Power Plant
Nuclear Fuel Cycle
Enrichment
Conversion
Uranium
Milling
Mining
Fuel Fabrication
Plutonium
Final Disposition
Reactor
Spent Fuel
Processing
Interim Storage
Fig 25: Schematic of the nuclear fuel cycle
Rachit Khare (IIT Roorkee)
Renewable Energy
December 18th 2009
47
Nuclear Energy
An Introduction
Factors Impacting Nuclear Power Plant
Internal Factors Impacting Nuclear Power Plant
•
•
•
•
•
Nuclear Accidents
Reactor Designs: Safe and economical to build
Waste Disposal
Assessment of radiation hazards
Resistance to proliferation and terrorism
External Factors Impacting Nuclear Power Plant
•
•
•
•
Energy & Electricity demand
Limitations on oil and gas resource
Global climate change
Renewable Energy: The technical and economic feasibility of renewable sources and
assessments of their environmental impacts are critical to judging the need for
nuclear power.
• Fusion Energy: If the hopes of fusion energy are fulfilled, the need for alternatives
will be greatly lessened
Rachit Khare (IIT Roorkee)
Renewable Energy
December 18th 2009
48
SUSTAINABILITY BY COMBINING NUCLEAR, FOSSIL,
AND RENEWABLE ENERGY SOURCES
o Basic Principles
o Peak Power Production
o Hydrogen intermediate and peak electricity system (HIPES)
o Nuclear-combustion combined-cycle (NCCC) systems
o Nuclear–fossil liquid-fuels production
o Nuclear–biomass liquid-fuels production
Rachit Khare (IIT Roorkee)
Renewable Energy
December 18th 2009
49
Combined Power Generation
Basic Principles
Sustainability by combining nuclear, fossil, and renewable energy sources
 The Energy Industries face two sustainability challenges:
•
need to avoid climate change
•
need to replace traditional crude oil as the basis of our transport system
 Radical changes in our energy system will be required to meet these challenges.
 These challenges may require tight coupling of different energy sources (nuclear,
fossil, and renewable) to produce liquid fuels for transportation, match electricity
production to electricity demand, and meet other energy needs.
 This implies a paradigm shift in which different energy sources are integrated together,
rather than being considered separate entities that compete.
 The pathway to such a future will likely be initiated in the production of liquid fuels
using nuclear-fossil and nuclear-biomass liquid-fuel production pathway.
 Nuclear–renewable and nuclear–fossil futures involve nuclear plants providing heat.
 In the longer term, nuclear energy is potentially the enabling technology for the largescale use of renewable electricity because nuclear energy may be able to provide peak
electricity when the sun does not shine or the wind does not blow.
Rachit Khare (IIT Roorkee)
Renewable Energy
December 18th 2009
50
Combined Power Generation
Peak Power Production
Peak Power Production
 Electricity demand varies daily, weekly, and seasonally.
 Renewable forms of electricity (wind and solar) compound the challenge.
 The output of these energy sources is highly variable on a day-to-day basis and thus
requires large peak electricity production capacity as backup power.
 Much of the world also experiences very large seasonal variations in renewable
electricity output.
 This implies the need for seasonal energy storage.
 Renewable electricity is the great uncertainty in the future of electricity production.
 Each of the existing major non-fossil methods to produce peak electricity has major
limitations:
• Hydropower: limited sites
• Compressed air energy system (CAES): Expensive
• Nuclear: Capital-intensive systems
 These considerations lead to the conclusion that in a carbon dioxide–constrained
world, one of the great electricity challenges is finding low-cost methods to meet
variable electrical demands.
Rachit Khare (IIT Roorkee)
Renewable Energy
December 18th 2009
51
Combined Power Generation
HIPES
Hydrogen intermediate and peak electricity system (HIPES)
 HIPES consists of three major components:
• Hydrogen production
• Hydrogen and Oxygen storage
• Hydrogen-to-electricity conversion
 The economics of HIPES are based on:
• minimization of the cost of hydrogen production by producing hydrogen at the
maximum rate possible from capital-intensive facilities
• low-cost bulk hydrogen and oxygen storages
• low-capital-cost, high-efficiency conversion of hydrogen and oxygen to electricity
 HIPES requires oxygen. This favors nuclear and renewable hydrogen production
systems that simultaneously produce oxygen as a by-product of hydrogen production.
 The high hydrogen transport costs will likely determine preferred hydrogen production
technologies for much of the world:
• Wind may be the preferred technology where there are high wind speeds.
• Solar energy becomes a competitive option where there are sunny skies.
• Nuclear energy does not have these geographical constraints and thus may
become the primary long-term method of hydrogen production
Rachit Khare (IIT Roorkee)
Renewable Energy
December 18th 2009
52
Combined Power Generation
NCCC
Nuclear-combustion combined-cycle (NCCC) systems
 NCCC power plant uses heat from a high-temperature nuclear reactor and hydrogen to
meet base- and peak-load electrical demands
 For base-load electricity production, air is first compressed; then flows through a heat
exchanger, where it is heated to between 700 and 900 °C; and finally exits through a
high temperature turbine to produce electricity.
 The heat, via an intermediate heat-transport loop, is provided by a high-temperature
reactor.
 To meet peak electrical demand, after the nuclear heating of the compressed air,
hydrogen is injected into the hot air and burnt to increase power levels.
 This process raises the peak inlet temperatures to both the gas turbine and the steam
turbine with corresponding increases in electricity output by up to a factor of four
 The response time to changes in power demand is much faster in an NCCC plant than
in a plant that uses traditional fossil-fueled combustion turbines
 An NCCC plant would use the same hydrogen production and storage systems as
HIPES, providing the option for production of hydrogen by electrolysis at periods of
time with low electricity demand
Rachit Khare (IIT Roorkee)
Renewable Energy
December 18th 2009
53
Combined Power Generation
Liquid Fuel Production
Nuclear–fossil liquid-fuels production
 Massive underground resources of fossil fuels could be converted into liquid fuels, but
many of these resources have been economically unrecoverable with existing
technologies.
 Conceptually, the technology is simple. A fossil deposit is heated to high temperatures.
As the temperatures increase, any volatile hydrocarbons will vaporize (be distilled),
move as gases toward recovery wells, condense in the cooler zones, and be pumped
out of the ground as a liquid or vapor.
 In effect, heating the underground fossil-fuel deposit duplicates the distillation and
thermal-cracking processes found in a refinery.
 Advantages:
• Abundant light crude oil
• Control of CO2 emission
 Conventionally electricity is used for heating purposes.
 Heat from the nuclear power plant can be used for this purpose.
 Direct use of high-temperature heat avoids the conversion of heat-to-electricity (with
all the associated losses) and subsequent use of the electricity to produce heat.
Rachit Khare (IIT Roorkee)
Renewable Energy
December 18th 2009
54
Combined Power Generation
Liquid Fuel Production
Nuclear–biomass liquid-fuels production
There are major worldwide initiatives to produce liquid fuels from biomass.
Liquid fuels from biomass are greenhouse neutral.
Biomass is produced by sunlight, carbon dioxide from the atmosphere, and water.
The carbon dioxide from burning biomass fuels recycles the carbon dioxide back to the
atmosphere.
 No net increase in atmospheric carbon dioxide levels occurs with biomass fuels.
However, the production of liquid fuels from biomass is currently limited.
 The energy value of the 1.3 billion tons of dry biomass per year that is available in the
United States depends upon the form in which it is used:
• Burnt biomass: 9.8 million barrels of diesel fuel per day
• Fuel ethanol: 4.7 million barrels of diesel fuel per day
• Diesel fuel: 12.4 million barrels of diesel fuel per day
 The nuclear–biomass liquid-fuels option is not a single option but rather three options
that could be implemented sequentially as technology is developed
• Ethanol from starch
• Ethanol from cellulose
• Biomass-to-hydrocarbon fuel: Fischer-Tropsch


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Rachit Khare (IIT Roorkee)
Renewable Energy
December 18th 2009
55
THANK YOU!!!
Rachit Khare (IIT Roorkee)
Renewable Energy
December 18th 2009
56