Renewable energy sources

Renewable Energy Sources
1 Energy science & Technology 9/22/2014

Introduction to Energy Science and Energy Technology,
Renewables and Conventionals
• What is Energy ?-Energy, Exergy, Anergy-Forms of Energy-Various Sciences
and Energy Science-Energy Technology-Energy, Man and Environment-Law of
Conservation of Energy-Thermodynamics and Energy Analysis -First and
Second Laws of Thermodynamics.
• Energy chains and Energy Links- Energy Resources-Primary Energy -
Intermediate Energy-Usable (Secondary) Energy -Energy Calculations-Units
and Conversion Factors.
• Conventional, Renewable, Non-conventional and Alternate Sources of
Energy. Energy Demand - Energy Requirements by various sectors-Energy
Routes of conventional energy-Renewable Energy. Wind Energy-Solar Energy
-Biomass Energy-Energy from Ocean-Geothermal Energy-Changing Energy
Consumption trends.
• Electrical Energy - Load curves-Peak Load/Base Load, Generating Units-
Energy Storage Plants. Energy
• Supply System in India - Coal and Coal Technologies-Petroleum and Natural
Gas-Nuclear Fuels and Power Plants-Hydro Resources and Power Plants-
Energy Strategies-Energy Conservation-Energy Audit-Cost of energy-Scope of
subject - Summary - Questions.

What is Energy?
The concept drawn from classical physics
while explaining work
Energy is the capability to produce motion; force,
work; change in shape, change in form, etc.
Energy exists in several forms. Energy transformations are
responsible for various activities
.

Hydrogen energy conversion paths

 Energy exists in many forms such as
• chemical energy (Ech),
• nuclear energy (Enu),
• solar energy (Eso),
• mechanical Energy (Eme)
• electrical energy (Eec),
• internal energy in a body (Ein),
• bio-energy in vegetables and animal bodies (Ebi),
• thermal energy Eth, etc.

coal, petroleum, solar,
wind, geothermal, etc
steam, chemicals
fuels, electricity etc

Energy Technology?
distinguish between 'Energy' 'Useful
Energy' and Worthless Energy' with
reference to useful work content.
Energy Science
Science is a systematized body of knowledge
about any department of nature, internal or
external to man.
The energy science deals with scientific
principles, characteristics, laws, rules,
units/dimensions, measurements, processes etc.
about various forms of energy and energy
transformations.
Science involves experimentation, measurement,
mathematical calculations, laws, observations, etc.

Energy Technology
 concerned with 'demand' for
various forms of secondary energy
(usable energy) and the methods of
'supply‘
 various alternative routes.
 deal with plants and processes
involved in the energy
transformation and analysis of the
useful energy (exergy) and
worthless energy (anergy). Energy
Technology includes study of
efficiencies and environmental
aspects of various processes.
 The applied part of energy
sciences for work and processes,
useful to human society, nations
and individuals is called Energy
Technology. Energy
technologies deal with various
primary energies, processing,
useful energies and associated
plants and processes. The
coverage including exploration,
transportation, conversion,
utilization.

Mother Science
Energy science has
interface with every other
science. Energy science is
the mother science of
physics, thermodynamics,
electromagnetic, nuclear
science, mechanical
science, chemical science,
biosciences etc. Each
science deals with some
'activity'. Energy is the
essence of activities.

Energy technology deals with the complete energy route and its steps
such as :
 - Exploration of energy resources- Discovery of new sources
 - Extraction or Tapping of Renewable or Growing of Bio-farms
 - Processing
 - Intermediate storage
 -Transportation/Transmission
 - Reprocessing
 - Intermediate storage
 - Distribution
 -Supply
 - Utilization.

Energy Strategies include
 long term policies,
 short-term and Mid-Term
Planning,
 Economic planning,
 Social and Environmental Aspects
of various energy routes.
These are analyzed from the
perspectives of the world, Region,
Nation, States, sub-regions,
various economic sectors,
communities and individuals
 Energy Science and Energy
Technology is of immense
interest to the Planers,
Economists, Scientists,
Engineers, Professionals
and Industrialists, Societies
and Individuals, etc.

Various Sciences and Energy Science
 Physics : It is a branch of natural science dealing
with properties and changes in matter and energy.
Physics deals with continuous changes in matter and
energy and includes mechanics, electromagnetic,
heat, optics, nuclear energy etc. and laws governing
the energy transformations. Energy science has
been developed by Physicists.
 Thermodynamics : It is a branch of physics dealing
with transformation of thermal energy into other
forms of energy, espe6ially mechanical energy and
laws governing the conversions. Thermodynamics
plays a dominant role in Energy Technologies.
 Biological Sciences deal with biomass and
biological processes.
 Bio sciences are concerned with the physical
characteristics,' life processes of living vegetation
and animals on land and in water and their remains.
 Biomass is the matter derived from vegetation and
nimals. Biomass is a natural renewable source of
energy and is being given highest priority in recent
years. (1980s onwards) Biomass is the important
renewable energy for the 21st century.
 Chemistry is a science dealing with composition and
properties of substances and their reactions to form
other substances. The chemical reactions are
accompanied by release of thermal energy
(exothermic reactions) or absorption of thermal
energy (endothermic reaction). Chemical Reactions
are intermediate energy conversion processes.
Many useable energy forms are obtained from
chemical reactions. (e.g. petroleum products,
synthetic gases and liquids). Natural Gas and
Petroleum products are most important energy forms
in the world during 20th and 21st century.
 Electromagnetic : The flow of electrons and
electrical charges through a circuit produces
associated electromagnetic fields and electrical
energy. Electromagnetic is a branch of physics
dealing with electricity, magnetism and various
transformations of ·other forms of energy
(mechanical, thermal, chemical etc.) into electrical I
energy and vice-versa. Electrical energy is the most
superior; efficient, useful form of energy which can
be generated, transmitted, distributed, controlled,
utilized. Electrical energy is an intermediate and
secondary form of energy being used very widely all
over the world.

Science : Finally figured out

Energy science and other sciences are co-related

Energy Technology and Energy
Sciences
Energy Science and Technology deal with several useful natural and artificial (man-made)
energy systems. The basic objectives are to extract, convert, transform,
transport, distribute and reconvert different types of energy with least pollution and
with highest economy.
Energy technology is a systematized knowledge of various branches of energy flow
and their relationship with human society as viewed from scientific, economic,
social, technological, industrial aspects for benefit of man and environment.
Science of energy is concerned with the natural rules and characteristics of energy,
energy resources, energy conversion processes and various phenomena related
directly or indirectly to the extraction conversion and use of energy resources
essential to the economy and prosperity.
Science of energy deals with the phenomena related with energy conversion plants and
processes for generating secondary energy (electricity, heat, steam, fuel, gas, etc.) by
converting various kinds of primary energy sources. It also deals with aspects of
useful energy, (exergy), work, power, efficiency and worthless energy (anergy)
losses etc.

Energy, Man and Environment
Close liason between Energy, Energy Conversion Processes, Man and Environment.

Renewables & Non-conventionals
Renewables
Conventional & Non-conventionals
Renewables are those which are renewed by the
nature again and again and their supply is not
affected by rate of consumption
Sources: solar, wind, geothermal, ocean thermal,
ocean wave, ocean tide, mini-hydro, bio-mass,
chemicals, waste fuels etc. These are available
from nature in renewable but
periodic/intermittent form.
Global Status: Renewables in the world is less
than 2% (excluding hydro). This is likely to
increase to about 10% by 2000 AD and to
about 15% by 2015· AD.
Merits & Demerits: Renewables are cheap, clean
energy resources. However, solar and wind
sources are intermittent, diffused and their
conversion technologies are presently costly
and suitable only of smaller plant capacities.
 Energy resources which are in
use during 1950-1975 are called
conventionals.
 Energy resources which are
considered for large-scale use
after 1973 oil crisis are called
Non-conventional or Alternate.

Renewables and Non-conventionals
Feature
Conventional/
Nonrenewable
Renewables
- Technologies Established Under development
- Plant size Large (MW range) Small (kW range)
- Main Power Plants Suitable Not sufficient
- Energy density of source High Low
- Pollution problems More Less
- Energy reserves Limited Will continue to renew
- Cost of generation Low High
-Storage Easy Uneconomical

Conventional and Renewable Resources for Electrical Generation
Conventional Alternative, Renewable*
Coal Wind power
Petroleum oils Solar power
Natural Gas Geothermal
Hydro Ocean waves
Nuclear fission fuels Ocean tide
Fire-wood Bio-mass fuels
Waste-fuels
Bio-gas
Synthetic gases
Nuclear fusion fuels+
Fuels for fuel cells
Firewood*
Ocean-algae fuel
Ocean salinity gradient+
*Considered on priority after 1973 oil crisis.
+ Not yet on commercial scale. *For power plants

 Non-renewable energy resources can not be get replenished
after their consumption. e.g. coal once burnt is consumed
without replacement of the same (Fossil fuels, Nuclear fission
fuels).
 The energy resources which are formed very slowly in nature
and which are likely to be exhausted in a few more decades or
centuries are called Non-renewable. World is presently
dependant on such resources (90% supplies of world primary
resources are by Nonrenewables-1990)

Energy Demand
Rising rapidly with growing
population and
industrialization.
Secondary (usable) energy forms
of importance are :
- Fuels: Coal, petroleum (Oil),
Natural Gas, Chemicals, Fire-wood
etc.
- Electrical power
- Chemicals for processes.
- Renewables such as solar heat,
bio-gas, wind, bio-mass etc.
Energy in various secondary
(usable) forms for various
activities.
- Domestic, Social, Municipal -
Agriculture
- Commercial
- Industrial
- Transportation
- Defence, Medical, Scientific
work etc.

Increasing demand of primary energy resources
in India

Total annual primary energy consumption between 1994 and 2004. Key: kWh, kiloWatt hours.
Source: US Dept of Energy Information Administration

World consumption of primary energy by fuel type between 1994 and 2004.
Key: GSWW, geothermal, solar, wind and wood/waste; kWh, kiloWatt hours

Energy consumption per capita in 1994 and 2004, by region. Total is the
average global energy use per capita. Key: kWh, kiloWatt hours

Increase in primary energy consumption per capita between 1994 and 2004. Total is the
average global increase, per capita, over the period.

Carbon dioxide emissions from fossil fuel consumption, in 1994 and 2004, by region

Percentage increase in carbon dioxide emissions from fossil fuel consumption, between 1994
and 2004, by region.
Note: emissions in Eurasia actually fell slightly. Total is the average global increase over the
period.

Projected increase in primary energy consumption from 2003 to 2030, by energy
type.
Key: energy "other" in this case is hydroelectricity together with renewables
(GSWW); kWh, kiloWatt hours

Projected percent increase in primary energy consumption from 2003 to 2030, by
energy type.
Key: energy "other" in this case is hydroelectricity together with renewables
(GSWW)

The cycle consisting of the gross
domestic product and the demand
for primary energy, which
determines the standard of living.
Correlation between the gross domestic product and the demand for primary energy of selected countries in 2000
The higher the demand for primary energy is in a country, the higher is its
gross domestic product and therefore the (measurable) standard of living.

During past several decades, the energy demand of the world has continued to
increase at an annual growth rate of 3 to 4% due to the following reasons:
- Increasing per capita energy consumption with increasing standard of living.
- Increasing population.
- Increasing industrialization.
-Invention of large energy conversion machines. (Electric motors, gas turbines internal
combustion engines etc.
- Increasing transportation.
- Development of energy supply systems and availability of electrical energy and fuels.
Energy needs of man vary with life-style, climatic conditions, season, industrial
progress etc.

 Industry needs coal, steam, electrical energy, furnace oils,
diesel, chemicals, lubricating oils etc. Raw materials, like steel,
copper, aluminum, etc. are produced by energy-intensive
processes. Water is pumped and distributed by using motor-pumps
which consume electrical energy. Transportation by
road, rail, ocean and air requires high energy input.
 Higher per capita energy consumption of a country indicates
industrial progress and prosperity. For example, the annual per
capita electrical energy consumption of India in 1988 was 2388
kWh against 92,000 kWh of USA.

Historical Review of Growing Energy Demand of Man
Daily per capita Energy Consumption, kWh per day, per capita
Historical age Food Agriculture Domestic Industry Transport Total
-Cave Man
(10,00,000 years ago)
3 3
-Hunting Man
(1,00,00 years ago) 4 3 7
- Agricultural Man (5000 BC)
5 2 6 13
-Industrial Man
- (20th Century) 10 5 60 100 85 260
- Technologically advanced
man (21st Century)
10 5 60 150 185 410
1 kWh = 1 kilo-watt hour = 1000 Watt. hour = 3.6 x 106 J

India’s electrical power plants:
India's demand for electrical energy is growing at an annual increase by 8 to 10%.
Conventional
Relative use % Non conventional
Renewable
Relative
use %
1. Coal Fired Steam Thermal 68 1. Wind-power
2. Hydro-electric Plants 25 2. Solar power
3. Nuclear Plants 5 3. Geothermal
4. Gas-Turbine Plants 4. Ocean-Thermal
5. Combined Cycle 2 5. Ocean-waves
-Gas 6. Waste incineration
-Steam 7. Biomass
8. Fuel cells
6. Cogeneration Plants 1 9. Nuclear Fusion
-Heat 10. Others
-Steam Total <1%
- Electricity
7. Renewable 1

Age of Renewables and
Alternatives
 Fossil Fuel age is expected to span only 1000 years
of human civilization (1700 AD to 2700 AD).
 The prices of petroleum are increasing.
 Environmental imbalance created by combustion
of coal; nuclear waste deposits, deforestation by
hydro power plants etc.

 Some alternate energy power plants have been built
on commercial basis in several advanced countries.
Developing countries have also initiated ambitious
projects for harnessing the Renewables.
 Present installed capacities of non-conventional
renewable energy plants (except hydro) in India are
negligible.

U.S. Energy Consumption by Energy Source, 2003-2007 (Quadrillion Btu)
Energy Source 2003 2004 2005 2006 2007
Total 98.209 100.351 100.503 99.861 101.605
Fossil Fuels 84.078 85.830 85.816 84.662 86.253
Coal 22.321 22.466 22.795 22.452 22.786
Coal Coke Net
0.051 0.138 0.044 0.061 0.025
Imports
Natural Gasa 22.897 22.931 22.583 22.191 23.625
Petroleumb 38.809 40.294 40.393 39.958 39.818
Electricity Net
0.022 0.039 0.084 0.063 0.106
Imports
Nuclear 7.959 8.222 8.160 8.214 8.415
Renewable 6.150 6.261 6.444 6.922 6.830
Biomassc 2.817 3.023 3.154 3.374 3.615
Biofuels 0.414 0.513 0.595 0.795 1.018
Waste 0.401 0.389 0.403 0.407 0.431
Wood Derived
Fuels
2.002 2.121 2.156 2.172 2.165
Geothermal 0.331 0.341 0.343 0.343 0.353
Hydroelectric
2.825 2.690 2.703 2.869 2.463
Conventional
Solar/PV 0.064 0.065 0.066 0.072 0.080
Wind 0.115 0.142 0.178 0.264 0.319
a Includes supplemental gaseous fuels.
b Petroleum products supplied, including natural gas plant liquids and crude oil burned as fuel.
c Biomass includes: biofuels, waste (landfill gas, MSW biogenic, and other biomass), wood and wood-derived fuels.
MSW=Municipal Solid Waste.
Note: Ethanol is included only in biofuels. In earlier issues of this report, ethanol was included both in petroleum and biofuels,
but counted only once in total energy consumption. Totals may not equal sum of components due to independent rounding.
Data for 2007 is preliminary.
Sources: Non-renewable energy: Energy Information Administration (EIA), Monthly Energy Review (MER) March
2008, DOE/EIA-0035 (2008/03) (Washington,DC, March 2008,)

Global Carbon Cycle (Billion Metric Tons Carbon)

9/22/2014
Energy science & Technology
65

World Renewables Energy Sources
Resource Form of delivered energy
(Application)
comments
Solar: Total Solar radiation ab-sorbed
by the earth and its
atmosphere is 3.8 x1024 J/yr.
Low temperature heat (space
heating water heating and
electricity)
Million of solar water heaters
and solar cookers are in use.
Solar cells and power towers
are in operation.
Wind: The kinetic energy
available in the atmosphere
circulation is 7.5 x1020 J
Electricity Several multi-megawatt wind
turbines are in operation and
many more in construction.
Mechanical energy (Pumping
transport)
There are numbers of small
wind turbines and wind
pumps in use.
Biomass: Total solar radiation
absorbed by plants is 1.3 x 1021
J/yr.
High temperature heat
(cooking, smelting etc.)
Bio-mass (principally wood
accounts for about 15% of the
world's (commercial fuel)
consumption; it provides over
80% of the energy needs of
many developing countries.
The worlds standing biomass
has an energy content of about
1.5 x 1021 J.
Bio-gas (cooking, mechanical
power etc.)
There are millions of biogas
plants in operation, most of
them are in China.

Resource Form of delivered energy
(Application)
comments
Alcohol(transport) Several thousand, million liters of alcohol
are being produced notably in Brazil and
the U.S. Production is increasing rapidly ;
many countries have lunched liquid bio-fuel
programmes.
Geothermal: The heat flux from
the earth's interior through the
surface is 9.5 x 1020J/yr.
Low temperature heat
(bathing. space and water
heating)
Geothermal energy supplies about 5350
MW of heat for use in bathing principally
in Japan, but also in Hungary, Iceland and
Italy. More than a lakh houses are supplied
with heat from geothermal wells. The
installed capacity is more than 2650 MW
(thermal).
The total amount of heat stored in
water or stream to a depth of 10
km is estimated to be
4 x 1021J ; that stored in the first 10
km of dry rock is around 1027 J.
Electricity Installed capacity is more than 2500 MW
but output is expected to increase more
than seven fold by 2000.

Resource Form of delivered
energy (Application) comments
Tidal: Energy dissipated in connection
with slowing down rotation of the
earth as a result of tidal action is
around 1026 J/yr.
Electricity Only one large tidal barrage is in operation (at La
Rance in France) and there are small schemes in
Russia and China. Total installed capacity is about
240 MW and the output around 0.5 TWh/yr.
Wave: The amount of energy stored
as kinetic energy in waves may be of
the order of 1018 J.
Electricity The Japanese wave energy research vessel, the
Kaimei, has an installed capacity of about 1 MW.
There are, in addition several hundred wave
powered navigational buoys: Designs after large
prototype wave energy converters are being drawn
up.
Hydro: The annual precipitation land
amounts to about 1.1 x 1017 kg of
water. Taking the average elevation of
land area as 840 m, the annually
accumulated potential energy would
be
9 x 1020 J.
Electricity Large hydroscheme15 provide about one quarter of
the world'l5 total electricity supply and more than
40% of the electricity used in developing countries.
The installed capacity is more than 363 GW. The
technically usable potential is estimated to be 2215
GW or 19000 TWb/yr. There are no accurate
estimates of the number of capacity of small
hydroplants currently in operation.

Primary
Energy
Resources
Non-electric
routes
World’s 48%
12% by non-commercial
route
World’s 40%
Electrical route
Final Energy
consumption
Two alternate route of energy supply

.
The yield ratio of the total sequence with n = 2 respectively n = 3 stations is calculated
according to the product rule
.
The factors have values which depend on the state of technological development in
every county. At the beginning of the 21. century
the values in fully developed countries were

Electrical energy
route
Primary Energy Processing Electrical
power plant
Electrical energy
Consumer

Efficiencies for various conversion engines

The second image above shows some of the conversions used in powering vehicles

Individual fuel consumption in 24 years and the years of complete exhaustion of individual fuels

Global primary energy structure, shares (%) of oil and gas, coal,
and non-fossil (zero-carbon) energy sources - historical
development from 1850 to 1990 and in SRES scenarios. Each
corner of the triangle corresponds to a hypothetical situation in
which all primary energy is supplied by a single source - oil and
gas on the top, coal to the left, and non-fossil sources
(renewables and nuclear) to the right. Constant market shares of
these energies are denoted by their respective isoshare lines.
Historical data from 1850 to 1990 are based on Nakic´enovic´ et
al. (1998). For 1990 to 2100, alternative trajectories show the
changes in the energy systems structures across SRES
scenarios. They are grouped by shaded areas for the scenario
families A1B, A2, B1, and B2 with respective markers shown as
lines. In addition, the four scenario groups within the A1 family
A1B, A1C, A1G, and A1T, which explore different technological
developments in the energy systems, are shaded individually. In
the SPM, A1C and A1G are combined into one fossil-intensive
group A1FI. For comparison the IS92 scenario series are also
shown, clustering along two trajectories (IS92c,d and
IS92a,b,e,f). For model results that do not include non-commercial
energies, the corresponding estimates from the
emulations of the various marker scenarios by the MESSAGE
model were added to the original model outputs.

Global renewable energy potentials for 2020 to 2025, maximum technical
potentials, and annual flows, in EJ. Data sources: Watson et al., 1996;
Enquete-Kommission, 1990.
Consumption Potentials by Long-term
Technical
Potentials
Annual
1860-1990 1990 2020-2025 Flows
Hydro 560 21 35-55 >130 >400
Geothermal - <a 4 >20 >800
Wind - - 7-10 >130 >200,000
Ocean - - 2 >20 >300
Solar - - 16-22 >2,600
>3,000,0
00
Biomass 1,150 55 72-137 >1,300 >3,000
Total 1,710 76 130-230 >4,200
>3,000,0
00

Non-electrical energy route
Primary energy Processing Secondary
energy
Transport by
road/rail/ocean/pipeline
Consumer

Renewable Energy sources like wind, solar heat,
waves etc. cannot be stored in original natural
form. It is converted continuously to electrical
form. transmitted, distributed and utilized without
long-term intermediate storage. The Renewables
are available free of cost. Hence, consumption of
renewable should be maximized. Non-renewable
should be conserved for some more decades /
centuries.

Thank you for
your kind
attention

Solar Energy Storage
90 Solar Energy Storage 9/22/2014

Introduction
• Solar energy is a time dependent and intermittent
energy resource
• The need for energy storage of some kind is
almost immediate evident for a solar electric
system.
• solar energy is most available will rarely coincide
exactly with the demand for electrical energy
• high insolation times could be used to provide a
continuous electrical output or thermal output

Storage of solar energy in a
solar system may:
• Permit solar energy to be captured when
insolation is highest
• it possible to deliver electrical load power demand
during times
• Be located close to the load
• Improve the reliability of the solar thermal as well
as solar electric system
• Permit a better match between the solar energy
input and the load demand output

Optimum capacity of an energy
storage system
• The expected time dependence of solar radiation
availability.
• The nature of load to be expected on the process.
• The degree of reliability needed for the process.
• The manner in which auxiliary energy is supplied.
• The size of the solar thermal power system or solar-electric
generator.
• The cost per kWh of the stored energy.
• The permissible capital cost allocated to storage.
• Environmental and safety considerations.
• An economic analysis that determines how much of the
total usually annual loads should be carried by solar and
how much by auxiliary energy sources. 93 Solar Energy Storage 9/22/2014

Solar Energy Storage Systems

Thermal Storage
Energy can be stored by
heating, melting or
vaporization of material,
and the energy
becomes available as
heat.
I. Sensible heat
storage
II. Latent heat

I. (A ) water storage
The most common heat transfer fluid for a solar
system is water, and the easiest way to store thermal
energy is by storing the water directly in a well
insulated tank.
Characteristics for storage medium
• It is an inexpensive, readily available and useful
material to store sensible heat.
• It has high thermal storage capacity.
• Energy addition and removal from this type of
storage is done by medium itself. thus
eliminating any temperature drop between
transport fluid and storage medium.
96 • PSuolmar Epneirngyg Stocraogest is small 9/22/2014

I. (B) Packed Bed Exchanger
Storage
Sensible heat storage with air as the energy transport
mechanism, rock, gravel, or crushed stone in a bin has the
advantage of providing a large, cheap heat transfer
surface.
Rock does have the following advantages over water
• Rock is more easily contained than water.
• Rock acts as its own heat exchanger, which reduces total
system cost.
• It can be easily used for thermal storage at high
temperatures, much higher than 100°C; storage at high
temperature where water can not be used in liquid form
without an experience, pressurized storage tank.
• The heat transfer coefficient between the air and solid is
high.
• The cost of storage material is low.
• The conductivity of the bed is low when air flow is not

II. (B) Latent heat storage
Materials that undergo a change of phase in a suitable temperature range may be
useful for energy storage
• The phase change must be accompanied by high latent heat
• The phase change must be reversible over a very large number of cycles without
degradation.
• The phase change must occur with limited super cooling.
• Means must be available to contain the material and transfer heat into it and out
of it.
• The cost of materials and its containers must be reasonable.
• Its phase change must occur close to its actual melting temperature.
• The phase change must have a high latent heat effect, that is, it must store large
quantities of heat.
• The material must be available in large quantities.
• The preparation of the phase changing material for use must be relatively
simple.
• The material must be harmless (non-toxic, non-inflammable, non-combustible,
non-corrosive).
• A small volume change during the phase change.
• The material should have high thermal conductivity in both the phases.

Materials for phase change energy
storage.
• Glauber's salt (Na2S04.10 H20), water, Fe(N03)2 .6
H20, and salt Eutectics
• Organic compound or substances serve as heat
storage materials Paraffin and fatty acids
• Refractory materials (MgO, Al203, SiO2) are also
suitable for high temperature sensible heat storage
in addition to Rock or pebble bed storage. Some
thermal storage materials such as ZnCI2, Na(OH)3,
NaOH, KOH-ZnCl2 KCl-MgCl2-NaCI, MgCl2 NaCl,
etc. are also used for the temperature range of 200-
450°C.

Latent Heat Storage Arrangement

Electrical Storage
 Capacitor storage
 Inductor storage
 Battery storage: stored electrochemically, and
later regained as electrical energy. Battery
storage system may be included under chemical
energy storage also.

Chemical Storage
1. Storage in the form of fuel:
• storage battery in which the reactant is generated by a
photochemical reaction brought about by solar radiation. The
battery is charged photo -chemically and discharged
electrically whenever needed.
• It is also possible to electrolyze water with solar generated
electrical energy, store O2 and H2 and recombine in a fuel cell
to regain electrical energy
• Solar energy could be used by the anaerobic fermentation
• Photosynthesis has been mentioned as a method of solar
energy conversion
• The carbohydrates are stable at room temperature; but at
high temperature the reaction is reversed, releasing the
stored energy in thermal form.

2. Thermo-chemical energy storage (Reversible
chemical reactions).
Thermo-chemical storage
systems are suitable for medium or high
temperature applications only. For storage of
high temperature heat, some reversible
chemical reactions appear to be very attractive.
Advantages of thermo-chemical storage include
high energy density storage at ambient
temperatures for long periods without thermal
losses and potential for heat pumping and
energy transport over long distances.

3. Hydrogen storage.

Mechanical Energy Storage
(i) Pumped hydroelectric
storage:
the water is allowed to flow
back down through a
hydraulic turbine which
drives an electric
generator. The overall
efficiency of the pumped
storage, that is, the
percentage or the
electrical energy used to
pump the water is
recovered as electrical
energy is about 70%.

(ii) Compressed Air
Storage.
when the wind is not
blowing the energy
stored in the air could
be utilized to drive an
air turbine, whose shaft
would then drive a
generator
(iii) Flywheel storage.
The energy is stored as
kinetic energy, most of
which can be electrically
regained when the
flywheel is run as a
generator

Electromagnetic energy
storage
Electromagnetic energy storage requires the use of
super conducting materials. These materials
(metals and alloys) suddenly lose essentially all
resistance to the flow of electricity when cooled
below a certain very low temperature. If
maintained below this temperature a super
conducting metal (or alloy) can carry strong
electric currents with little or no loss.

Solar Pond
Introduction: A natural or artificial body of water
for collecting and absorbing solar radiation energy
and storing it as heat. Thus a solar pond combines
solar energy collection and sensible heat storage.

Features
 The simplest type of solar pond is very shallow, about 5 - 10
cm deep, with a radiation absorbing (e.g., black plastic)
bottom.
 All the pond water can become hot enough for use in space
heating and agricultural and other processes.
 the water soon acquires a fairly uniform temperature.
 Solar ponds promise an economical way over flat-plate
collectors and energy storage by employing a mass of water
for both collection and storage of solar energy.
 The energy is stored in low grade (60 to 100ºC)
 Salt-gradient solar pond or nonconvecting solar pond' are
also often used, as to distinguish these ponds from 'shallow
solar pond'.

The salt used in a solar pond for creating
density gradient should have the following
characteristics:
 It must have a high value of solubility to allow high solution
densities.
 The solubility should not vary appreciably with temperature.
 Its solution must be adequately transparent to solar radiation.
 It must be environmentally benign, safe to handle the ground
water.
 It must be available in abundance near site so that its total
delivered cost is low, and
 It must be inexpensive.

Extraction of Thermal Energy
The process of heat extraction, accomplished by
hot brine with drawn and cool brine return in a
laminar flow.
Thermal energy from solar pond is used to drive a
Rankine cycle heat engine. Hot water from the
bottom level of the pond is pumped to the
evaporator.

Applications of Solar Ponds
1. Heating and
Cooling of
Buildings.
Because of the large
heat storage
capability in the lower
convective zone of the
solar pond, it has
ideal use for heating
even at high latitude
stations and for
several cloudy days.
2. Production of
Power.
A solar pond can be used
to generate electricity by
driving a thermo-electric
device or an organic
Rankine cycle engine-a
turbine powered by
evaporating an organic
fluid with a low boiling
point.

3. Industrial
Process Heat.
Industrial
process heat is the
thermal energy used
directly in the
preparation and of
treatment of materials
and goods
manufactured by
industry.
4. Desalination.
The low cost thermal
energy can used to
desalt or otherwise
purify water for
drinking or irrigation.

5. Heating animal
housing and drying
crops on farms.
6. Heat for biomass
conversion.
Site built solar
ponds could provide
heat to convert
biomass to alcohol
or methane

Thank you for kind
attention

Solar Energy Storage

Introduction
• Solar energy is a time dependent and intermittent
energy resource
• The need for energy storage of some kind is
almost immediate evident for a solar electric
system.
• solar energy is most available will rarely coincide
exactly with the demand for electrical energy
• high insolation times could be used to provide a
continuous electrical output or thermal output

Storage of solar energy in a solar
system may:
• Permit solar energy to be captured when
insolation is highest
• it possible to deliver electrical load power demand
during times
• Be located close to the load
• Improve the reliability of the solar thermal as well
as solar electric system
• Permit a better match between the solar energy
input and the load demand output

Optimum capacity of an energy
storage system
• The expected time dependence of solar radiation
availability.
• The nature of load to be expected on the process.
• The degree of reliability needed for the process.
• The manner in which auxiliary energy is supplied.
• The size of the solar thermal power system or solar-electric
generator.
• The cost per kWh of the stored energy.
• The permissible capital cost allocated to storage.
• Environmental and safety considerations.
• An economic analysis that determines how much of the
total usually annual loads should be carried by solar and
how much by auxiliary energy sources. 129 Solar Energy Storage 9/22/2014

Solar Energy Storage Systems

Thermal Storage
Energy can be stored by
heating, melting or
vaporization of material,
and the energy
becomes available as
heat.
I. Sensible heat
storage
II. Latent heat

I. (A ) water storage
The most common heat transfer fluid for a solar
system is water, and the easiest way to store thermal
energy is by storing the water directly in a well
insulated tank.
Characteristics for storage medium
• It is an inexpensive, readily available and useful
material to store sensible heat.
• It has high thermal storage capacity.
• Energy addition and removal from this type of
storage is done by medium itself. thus
eliminating any temperature drop between
transport fluid and storage medium.
132• PSuolmar Epneirngyg Stocraogest is small 9/22/2014

I. (B) Packed Bed Exchanger
Storage
Sensible heat storage with air as the energy transport
mechanism, rock, gravel, or crushed stone in a bin has the
advantage of providing a large, cheap heat transfer
surface.
Rock does have the following advantages over water
• Rock is more easily contained than water.
• Rock acts as its own heat exchanger, which reduces total
system cost.
• It can be easily used for thermal storage at high
temperatures, much higher than 100°C; storage at high
temperature where water can not be used in liquid form
without an experience, pressurized storage tank.
• The heat transfer coefficient between the air and solid is
high.
• The cost of storage material is low.
• The conductivity of the bed is low when air flow is not

II. (B) Latent heat storage
Materials that undergo a change of phase in a suitable temperature range may be useful for energy
storage
• The phase change must be accompanied by high latent heat
• The phase change must be reversible over a very large number of cycles without degradation.
• The phase change must occur with limited super cooling.
• Means must be available to contain the material and transfer heat into it and out of it.
• The cost of materials and its containers must be reasonable.
• Its phase change must occur close to its actual melting temperature.
• The phase change must have a high latent heat effect, that is, it must store large quantities of
heat.
• The material must be available in large quantities.
• The preparation of the phase changing material for use must be relatively simple.
• The material must be harmless (non-toxic, non-inflammable, non-combustible, non-corrosive).
• A small volume change during the phase change.
• The material should have high thermal conductivity in both the phases.