Energy Security and Conservation

A Major Part of the Solution to Energy Generation and

Environmental Degradation

Dr. R.P. DahiyaProfessor, IIT Delhi

Email: rpdahiya@ces.iitd.ac.inApril 21, 2023

ENERGY SECURITY

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.April 21, 2023

Scientists in Energy

James Joule

First Law of

Thermodynamics

Sadi Carnot

Second Law of

Thermodynamics

Carnot Cycle

Thomas Edison

Light Bulb, etc.

Alexander

Graham Bell

Telephone

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Scientists in Energy

Albert Einstein

E=mc²

Enrico Fermi

First Nuclear

Reactor

William Shockley

Transistor

Bill Gates

Computers

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Topics

• Energy Sources and Uses • Fossil Fuels• Nuclear Power• Energy Conservation• Solar Energy• Fuel Cells• Biomass• Energy From the Earth’s Forces• What’s Our Energy Future?

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PART 1: ENERGY SOURCES AND USES

• Work is the application of force through a distance.• Energy is the capacity to do work.• Power is the rate of flow of energy, or the rate at

which work is done.– A small calorie is the metric measure of energy necessary to heat

1 gram of water 1oC, whereas a British Thermal Unit (BTU) is the energy needed to heat 1 pound of water 1oF

– A joule is the amount of work done by a force needed to accelerate 1 kilogram 1 meter per second per second. Another definition for joule is the force of an electrical current of 1 amp/second through a resistance of 1 ohm.

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Measurements

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Worldwide Commercial Energy Production

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How We Use Energy• What are the commercial uses of energy?

– Industry uses 38%;

– Residential and commercial buildings use 36%; and,

– Transportation uses 26%.

• Half of all energy in primary fuels is lost during conversion to more useful forms while being shipped or during use.– Nearly two-thirds of energy in coal being burned to generate

electricity is lost during thermal conversion in the power plant. Another 10% is lost during transmission and stepping down to household voltages.

• Natural gas is the most efficient fuel.– Only 10% of its energy content is lost during shipping and

processing. Ordinary gas-burning furnaces are about 75% efficient. High-economy furnaces can be 95% efficient.

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Energy Use Trends

• A general trend is for higher energy use to correlate with a higher standard of living

• In an average year, each person in the U.S. and Canada consumes more than 300 times the amount of energy consumed by a person in one of the poorest countries of the world; however,

• Several European countries have higher living standards than the U.S., yet they use about half as much energy.

Per Capita Energy Use & GDP

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ENERGY RESOURCE AVAILABILITY IN INDIA

Source Capital cost (crores/MW)

Emissions (t CO2-eq/Mwh)

Reserves Longevity

Coal 4-5 1.1 10 5820 MT 70 years

Oil 2.5 0.62 1200 MT ~ 10 years

Gas 3.5 0.47 1.5 TCM ~ 20 years

Hydro 6- 20 (Site and size dependant)

0 148.7 GW NA

Nuclear 8-13 0 70,000 tonnes of Uranium~ 200 tonnes of Pu

40 years with Uranium

Source : BP statistical review report, NHPC,NTPC

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INDIA'S ENERGY ASPIRATIONS

• Annual GDP growth projection : 8 – 9%• Elasticity of electricity : GDP ~ 0.95• Net electricity generation required in 2020 : 1850 billion units

– per capita electricity consumption in 2020 : ~ 1200 kWh– Still, well below world average of 2800 kWh

• India has announced intent to reduce CO2 intensity: GDP by 20-25% from 2005 levels by 2020

• Multiple objectives for Indian energy policy – Access for all– Reliability– Low cost– Low carbon– Energy Security

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INDIA’S PRIMARY ENERGY CONSUMPTION :

A SNAPSHOT

Source : BP statistical review of world energy, 2011; CSTEP

In 2010 alone, India’s primary energy consumption grew by 9.2%

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ELECTRICAL ENERGY STATUS IN INDIA

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ELECTRIC POWER• Current Capacity : 173,855 MW (utility)

– 5th largest in the world

• Low per capita electricity consumption– India 717 kWh– US 14,000 kWh– China 2500 kWh– World 2800 kWh

• Peak shortage ~ 15%• 800,000 MW in 2030 – 40

– ~ 25,000 MW per year

• Environmental concerns – India 3rd largest emitter of CO2 behind China and US– 38% of emissions from power sector

• Energy security concerns– 67% power from coal-based thermal plants - need to depend on imports– Prototype breeder reactors to exploit thorium reserves

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SOURCE: CEAApril 21, 2023

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ENVIRONMENTAL CONCERNS : GHG EMISSIONS IN INDIA (2007)

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ENERGY SECURITY CONCERNS

Source : Telegraph, FT

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PROJECTED FUEL MIX IN 2020 • Required capacity in 2020 assuming 8% growth = 387,280 MW in BAU

scenario

Source : Interim report, Planning commission 2011 April 21, 2023

• How do we grow to ~ 2,000 billion kWh by 2020

• How do we get 3,00 billion kWh of low-carbon power?

• What fuel options & technologies? • Wind• Nuclear,• Solar• Hydro • Bio-fuels• Carbon Sequestration• Hydrogen & fuel cells• Hybrid cars

• Investments, research, policies?

HOW TO GROW AND BE SUSTAINABLE?

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WIND POWER • Power proportional to V 3

• Cost of generation reasonable: ~ Rs 3 per kWh

– Economics sensitive to wind speeds

• World total installed 194,000 MW

• India: – Potential: 50,000 MW based on hub height

of 50 m and 2% land usage– Recent studies offer reassessed potential

at 80m 6-7% land usage• Onshore - 676, 000 MW• Offshore - 214,000 MW

– Intermittent; grid stability is a concern

China 44, 733 MW

US 40,180 MW

Germany 27,215 MW

Spain 20,676 MW

India 13,000 MW

India - 5th in wind capacity

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SOLAR POWER

• JNNSM launched in 2010 targets 22,000 MW by 2022– Phase 1 ( until March 2013)

• Target of 1300 MW : 800 MW PV and 500 MW CSP • 25 years of guaranteed feed in tariff

– Off-grid PV• Target of 2000 MW by 2022• Rural applications where grid is unviable or unreachable

– Challenges• High nominal cost of generation : ~ Rs 15 per kWh• Water scarcity issues for CSP• Requirement of skilled personnel

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NUCLEAR POWER

• Installed Capacity 4780 MW• Generation ~ 23 Billion kWh

(2.5 % of total)

• Domestic Uranium reserves ~ 61,000 Tons– Poor quality ore (0.01% - 0.05% Uranium)

• Large Thorium deposits– But, Thorium is fertile and has to be converted to fissile U233 in a reactor

• Phase Nuclear Program– Phase I Build Pressurized Heavy Water Reactors using domestic Uranium– Phase II Reprocess spent fuel from Phase I to get Plutonium for Breeder Reactors– Phase III Use U233 (obtained from Thorium) and use it with Plutonium

• Domestic Uranium reserves can sustain 10,000 MW PHWR for 40 years– Low capacity factors due to Uranium mining constraints

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INDIAN NUCLEAR POWER PROGRAM

Type Operating Projections (2020)

Projections (2030)

Heavy Water Reactors

4,460 MW 10,000 MW 10,000 MW

Light Water Reactors

320 MW 9,300 MW 22,000 MW

Fast Breeder Reactors

- 1,500 MW 1,500 MW

Total 4780 MW 20,800 MW 33,500 MW

Nuclear capacity presently under construction : 5300 MW

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ELECTRICITY GENERATION COSTS : COMPARISON

Source : LBNL, CERC , CSTEP & NPCILApril 21, 2023

POTENTIAL R&D DOMAINS

• New and affordable materials for photovoltaic• Clean coal technologies; carbon capture and

sequestration• Low-speed wind power• Cellulosic ethanol• Efficient and affordable hybrids, electric vehicles• Energy storage – efficient batteries and condensers• Demand side management of power• Trained human resource

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Conservation of Energy

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PART 4: ENERGY CONSERVATION

Hybrid gas-electric automobileApril 21, 2023

ENERGY CONSERVATION– Most potential energy in fuel is lost as waste heat.– In response to 1970’s oil prices, average US automobile gas-mileage

increased from 13 mpg in 1975 to 28.8 mpg in 1988. Falling fuel prices of the 1980’s, however, discouraged further conservation.

Energy Conversion Efficiencies•Energy Efficiency is a measure of energy produced compared to energy consumed.

–Household energy losses can be reduced by one-half to three-fourths by using better insulation, glass, protective covers, and general sealing procedures. Energy gains can be made by orienting homes to gain passive solar energy in the winter.

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Definition

Conservation of energy refers to efforts made to reduce energy

consumption and to increase efficiency of energy use.

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Conservation of Energy

P.E K.E. P.E. K.E. … Is energy lost?

No! Energy is converted!April 21, 2023

Conserve Electricity

Conserve Natural Gas

Conserve Water

So On ………...

What does conserve energy mean?What does conserve energy mean?

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Energy ConservationEnergy ConservationEnergy ConservationEnergy Conservation

Consider safety first

Saving energy is important, but avoid measures that have negative impacts on people and communities

All existing and potential health and safety issues should be evaluated prior to implementing any conservation measures

Safety First!Safety First!

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Law of Conservation of Energy

• Energy can be neither created nor destroyed. • The total energy in a “closed” system is always

the same.• The energy may be in different forms, but the

amount will be equal.

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Conservation of Energy

• Thermal Energy produced by friction is not useful energy-Why?

• It IS NOT used to do work.

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Perpetual Motion

• A machine that would run forever without the addition of energy.

• Some energy is wasted due to the thermal energy produced, so perpetual motion is not possible.

• So how does the “drinking bird” work? April 21, 2023

Technically, the Drinking Bird is a type of "Heat Engine". But thankfully you won't need a degree in physics or thermodynamics to understand the basics of how it works!

The body of the bird comprises 2 glass "bulbs", one for the head and The glass tube which interconnects the two bulbs dips deep into a special liquid (usually coloured methylene chloride) in the body.

ANATOMY OF A HAPPY DRINKING BIRD -HOW IT WORKS - The techie stuff.

An important fact is that the bird will "drink" providing the head bulb is slightly cooler than the body bulb (i.e. there is a "temperature differential").

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ANATOMY OF A HAPPY DRINKING BIRD -HOW IT WORKS - The techie stuff.Technically, the Drinking Bird is a type of "Heat Engine". But thankfully you won't need a degree in physics or thermodynamics to understand the basics of how it works!The body of the bird comprises 2 glass "bulbs", one for the head and The glass tube which interconnects the two bulbs dips deep into a special liquid (usually coloured methylene chloride) in the body.one for the lower body.An important fact is that the bird will "drink" providing the head bulb is slightly cooler than the body bulb (i.e. there is a "temperature differential").The head is usually coated in a red felt-like material which absorbs water when the bird "drinks". Evaporation of water from the head causes the head to become cooler than the body. By lucky coincidence, the swaying motion of the bird assists the evaporation.Although the head and upper part of the glass tube appear to be "empty", they are actually full of invisible vapour from the methylene chloride. Methylene chloride is good for this because it doesn't take much heat energy to turn it into a vapour (It has a "low latent heat of evaporation").Because the head is cooler than the body, some of this vapour condenses inside the head, like steam when it touches a cold window. As this vapour "shrinks" into minute droplets of fluid, it takes up a lot less space. This makes the pressure inside the head slightly lower than the body, causing the liquid to be sucked up the tube. You could also think of it as the "hot" fluid in the body making "steam" above itself, which blows the liquid up the tube (vapour pressure); it's all relative. The main thing is, the body is always warmer than the head. It's not the same a thermometer, though, because it does not rely on expansion of the liquid itself, which is insignificant. It's the pressure of the vapour that does the work.As the liquid rises up the tube, it gradually changes the centre of gravity of the bird. This makes it tip over more and more until eventually it tilts into the water. If everything is adjusted just right, then as it tilts over, the end of the tube inside the body comes out of contact with the liquid. Instead of pushing the liquid up the tube, the vapour above the liquid in the body can now quickly rush up the tube, equalising the pressures in head and body. As this happens, the liquid which has moved up towards the head now gurgles back down into the body. This rapidly moves the centre of gravity back to the lower body, and the bird swings back away from the glass.When you understand how the bird works, you will see how you can even "trick" it to "dip" with no water at all:If you shine a lamp towards only the bottom part of the bird, this slightly warms it (compared to the head), so there is the necessary "temperature differential" and it should "dip".If you have just shown your friends how the bird works (with water), then you may perhaps puzzle them again by removing the glass, and watching it continue to drink long even though the head has become dry, secretly using the warmth from a lamp nearby (which may have been on before). Take care, though, because excessive heat will burst the glass and make a terrible mess! (Thanks to Jan at "Arabesk" for this interesting trick

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“Zero energy” new homes

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Household Energy Use for Entertainment Electronics

0 200 400 600

Plasma HDTV

DVD/VCR

HD set top box

Analog CRT

DVD/VCR

Digital cable set top box

Annual Energy Use (kWh)

Primary TV

Secondary TV

Combined energy use~ 1200 kWh per year

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Lighting

• Compact Fluorescents or Long Fluorescents using plasma discharges use only 1/3 of the energy and heat of incandescent lights, which derive their light from heating filaments hot enough to emit visible light.

• If every home changed their five most used lights, they would save $60 per year in costs.

• This would also be equal to 21 power plants.• The fluorescents also last up to 10 times as long.• Replacing one bulb means 1,000 pounds less CO2

emitted over the compact fluorescent’s lifetime.• Traffic signal LEDs use 90% less energy and last 10 years

rather than 2 years.

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Additional Advantages of Energy Conservation (Moralizing)

• Less need to secure oil overseas with attendant military and civilian casualties while costing hundreds of billions of dollars

• Fewer power plants and liquid natural gas ports are needed

• Less air pollution• Less drilling for oil in Alaska and near national parks• Less global warming and attendant environmental

destruction

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Conclusions on Energy Conservation

• Energy conservation has saved the need for many power plants and fuel imports.

• It has also avoided CO2 and environmental pollution.• Regulations on efficiency work, but voluntary efforts lag far behind.• Much has been done, but much more can be done• In this new era of global warming and high energy costs and energy

shortages, the public must be informed and politicians sought who are sensitive to these issues.

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PART 6: FUEL CELLS

• Fuel cells use ongoing electrochemical reactions to produce electrical current

• Fuel cells provide direct-current electricity as long as supplied with hydrogen and oxygen.

• Hydrogen is supplied as pure gas, or a reformer can be used to strip hydrogen from other fuels.

• Fuel cells run on pure oxygen and hydrogen produce only drinkable water and radiant heat.

• Reformer releases some pollutants, but far below conventional fuel levels.

• Fuel cell efficiency is 40-45%.• Positive electrode (cathode) and negative

electrode (anode) separated by electrolyte which allows charged atoms to pass, but is impermeable to electrons. Electrons pass through external circuit, and generate electrical current.

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PART 7: BIOMASS

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Fuelwood Crisis

• Currently, about half of worldwide annual wood harvest is used as fuel.– Eighty-five percent of fuelwood is harvested in developing countries.

• By 2025, worldwide demand for fuelwood is expected to be twice current harvest rates while supplies will have remained relatively static.

• About 40% of world population depends on firewood and charcoal as their primary energy source.– Of these, three-quarters do not have an adequate supply.

• Problem intensifies as less developed countries continue to grow.– For urban dwellers, the opportunity to scavenge wood is generally

nonexistent.

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Fuelwood Crisis in Less-Developed Countries

• About 40% of the world’s population depends on firewood and charcoal as their primary energy source.

• Supplies diminishing• Half of all wood

harvested worldwide is used as fuel.

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Using Dung as Fuel

• Where other fuel is in short supply, people often dry and burn animal dung.

• When burned in open fires, 90% of potential heat and most of the nutrients are lost.

• Using dung as fuel deprives fields of nutrients and reduces crop production.

• When cow dung is burned in open fires, 90% of the potential heat and most of the nutrients are lost.

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Using Methane As a Fuel

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Alcohol from Biomass

• Ethanol (grain alcohol) production could be a solution to grain surpluses but thermodynamic considerations question it being practical on a sustainable basis. Gasohol (a mixture of gasoline and alcohol) reduces CO emissions when burned in cars. Ethanol raises octane ratings, and helps reduce carbon monoxide emissions in automobile exhaust.

• Methanol (wood alcohol)• Both methanol and ethanol make good fuel for fuel cells.

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PART 8: ENERGY FROM EARTH'S FORCES

• Water power produces 25% of the world’s electricity and it is clean, renewable energy.

• Dams cause social and ecological damage.

WindGeothermalTidalWaveHydropower

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• Hydropower– By 1925, falling water generated 40% of world’s electric power.

• Hydroelectric production capacity has grown 15-fold, but fossil fuel use has risen so rapidly that now hydroelectric only supplies one-quarter of electrical generation.

• Total world hydropower potential estimated about 3 million MW.– Currently use about 10% of potential supply.

• Energy derived from hydropower in 1994 was equivalent to 500 million tons of oil. Much of recent hydropower development is in very large dams.

• Drawbacks to dams include:– Human Displacement– Ecosystem Destruction– Wildlife Losses– Large-Scale Flooding Due to Dam Failures– Sedimentation– Herbicide Contamination– Evaporative Losses– Nutrient Flow Retardation

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Wind Energy

• Wind power - advantages and disadvantages• Wind farms - potential exists in Great Plains, along seacoasts and Eastern

Washington

http://www.awea.org/projects/washington.htmlApril 21, 2023

This energy source involves the use of high-pressure, high-temperature steam fields that exist below the earth’s surface.

Geothermal Energy

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Tidal & Wave Energy

•Ocean tides and waves contain enormous amounts of energy that can be harnessed.

–Tidal Station - Tide flows through turbines, creating electricity. It requires a high tide/low-tide differential of several meters.–Main worries are saltwater flooding behind the dam and heavy siltation.–Stormy coasts with strongest waves are often far from major population centers.

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Part 9:An Alternative Energy Future?

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THANK YOU

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DEMAND-SIDE MEASURES : SMART GRIDS • Indian Institute of Science & CSTEP

– “Smart grid” test bed in IISc campus– Consortium of technology provider companies

• Ministry of Power (under R-APDRP)

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BIOFUEL POTENTIAL

• India’s total land area 328 million hectares (mha)– Cultivated 142 mha– Cultivable wasteland 30 mha– Rice 40 mha– Wheat 26 mha

• Hazardous to divert agricultural area for bio-fuels.

• If entire wasteland used for growing bio-fuels, – Produce about 30 million tons of bio-oil – 10% of oil demand by 2031.

• Advisable to cultivate on such a large area?

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ETHANOL OPPORTUNITIES

• Increase yield of sugarcane using drip irrigation & fertigation– Present average yield ~ 80 tons per ha– Using drip irrigation & fertigation 150 tons per ha

• Sweet sorghum:– Less water intensive than sugarcane– Two crops a year

• Cellulosic ethanol from agro-forest residues such as bagasse, rice husk, wood chips, crop residues. – Technology needs to be developed

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WHAT CAN 1 HECTARE DO?

Bio-Fuels indirectly use solar energy

Why not do it directly?

Solar

Option 1Sugarcane

Option 2Corn Ethanol

Option 3Jatropha

Option 4Sweet Sorghum

Option 5Solar

Sugarcane:80 tons

No SugarCane juice used to make ethanol.

Ethanol:6000 Liter per hectare

Corn Yield:7500 Kg per hectare

Ethanol: 0.37 Liter per kg

2800 Liter per hectare

2000 to 3000 Trees per hectare

Seed yield: 1 to 2 Kg per tree

Oil Yield: 1 to 1.5 Ton per hectare

Stalk yield: 35 – 50 tons per hectare

Juice Extraction45 – 50%

Ethanol: 2500 to 3500 Liters per hectare

Average daily radiation:5- 6 kWh/m2250 days of sunshine

50% area covered by PV panels

10% Efficiency of solar cells

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LAND REQUIRED(HA/1000 MW)

Source : NPCIL & CSTEP

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PART 2: FOSSIL FUELS

• Fossil fuels are organic chemicals created by living organisms that were buried in sediments millions of years ago and transformed to energy-rich compounds.

• Because fossil fuels take so long to form, they are essentially nonrenewable resources.

Coal Oil Natural Gas

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Oil

Coal

Natural Gas

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Coal Extraction and Use

• Mining is dangerous to humans and the environment

• Coal burning releases large amounts of air pollution, and is the largest single source of acid rain in many areas.

• Economic damages are billions of rupees

• Billions of tons of coal are burned the world over for electric power generation. As a result, multiple pollutants are released such as:

– Sodium Dioxide (18 million metric tons)

– Nitrogen Oxides ( over 5 million metric tons)

– Particulates (over 4 million metric tons)

– Hydrocarbons (over 600,000 metric tons)

– Carbon Dioxide (over 1 trillion metric tons)

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Oil Extraction and Use

• The countries of the Middle East control two-thirds of all proven-in-place oil reserves. Saudi Arabia has the most.

• The U.S. has already used up about 40% of its original recoverable petroleum resource.

• Oil combustion creates substantial air pollution.• Drilling causes soil and water pollution.• Often oil contains a high sulfur level. Sulfur is corrosive, thus

the sulfur is stripped out before oil is shipped to market.• Oil is primarily used for transportation providing > 90% of

transportation energy.• Resources and proven reserves for the year 2000 are 650

billion barrels (bbl). 800 bbl remain to be discovered or are currently not recoverable.

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Natural Gas Consumption

• Proven world reserves and resources of natural gas equal 3,200 trillion cubic feet. This equals a 60 year supply at present usage rates.

• Natural gas produces only half as much CO2 as an equivalent amount of coal.

• Problems: difficult to ship across oceans, to store in large quantities, and much waste from flaring off.

•World’s third largest commercial fuel (23% of global energy used).

•Produces half as much CO2 as equivalent amount of coal.

•Most rapidly growing used energy source.

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PART 3: NUCLEAR POWER

• President Dwight Eisenhower, 1953, “Atoms for Peace” speech.– Eisenhower predicted that nuclear-powered electrical generators would

provide power “too cheap to meter.”– Between 1970-1974, American utilities ordered 140 new reactors, but

100 were subsequently canceled.

• Nuclear power now produces only 7% of the U.S. energy supply.

• Construction costs and safety concerns have made nuclear power much less attractive than was originally expected. – Electricity from nuclear power plants was about half the price of coal

in 1970, but twice as much in 1990.

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How Do Nuclear Reactors Work

• The common fuel for nuclear reactors is U235 that occurs naturally (0.7%) as a radioactive isotope of uranium.

• U235 is enriched to 3% concentration as it is processed into cylindrical pellets (1.5 cm long). The pellets are stacked in hollow metal rods (4 m long).

• 100 rods are bundled together into a fuel assembly. Thousands of these fuel assemblies are bundled in the reactor core.

• When struck by neutrons, radioactive uranium atoms undergo nuclear fission, releasing energy and more neutrons.This result triggers a nuclear chain reaction.

• This reaction is moderated in a power plant by neutron-absorbing solution (Moderator).

• Control Rods composed of neutron-absorbing material are inserted into spaces between fuel assemblies to control reaction rate.

• Water or other coolant is circulated between the fuel rods to remove excess heat.

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Nuclear fission occurs in the core of a nuclear reactor

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Kinds of Reactors

• 70% of nuclear power plants are pressurized water reactors (PWRs). Water is circulated through the core to absorb heat from fuel rods. The heated water is then pumped to a steam generator where it heats a secondary loop. Steam from the secondary loop drives a high-speed turbine making electricity.

• Both reactor vessel and steam generator are housed in a special containment building. This prevents radiation from escaping and provides extra security in case of accidents. Under normal operations, a PWR releases little radioactivity.

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Reactor Design

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Radioactive Waste Management

• Production of 1,000 tons of uranium fuel typically generates 100,000 tons of tailings and 3.5 million liters of liquid waste.

– Now approximately 200 million tons of radioactive waste exists in piles around mines and processing plants in the U.S.

• About 100,000 tons of low-level waste (clothing) and about 15,000 tons of high-level (spent-fuel) waste in the US.

– For past 20 years, spent fuel assemblies have been stored in deep water-filled pools at the power plants. (designed to be temporary).

– Many internal pools are now filled, and a number plants are storing nuclear waste in metal dry casks outside.

• A big problem associated with nuclear power is the disposal of wastes produced during mining, fuel production, and reactor operation.

– U.S. Department of Energy announced plans to build a high-level waste repository near Yucca Mountain Nevada in 1987.

– Cost is $10-35 billion, and earliest opening date is 2010.– This allows the government to monitor & retrieve stored uranium.

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PART 5: SOLAR ENERGY

• Photosynthesis• Passive solar heat is using

absorptive structures with no moving parts to gather and hold heat. Greenhouse design

• Active solar heat is when a system pumps a heat-absorbing medium through a collector, rather than passively collecting heat in a stationary object. Water heating consumes 15% of US domestic energy budget.

Mean solar energy striking the upper atmosphere is 1,330 watts per square meter. The amount reaching the earth’s surface is 10,000 times > all commercial energy used annually. Until recently, this energy source has been too diffuse and low intensity to capitalize for electricity production.

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High-Temperature Solar Energy

•Parabolic mirrors (left) are curved reflective surfaces that collect light and focus it onto a concentrated point. It involves two techniques:

–Long curved mirrors focus on a central tube containing a heat-absorbing fluid.–Small mirrors arranged in concentric rings around a tall central tower track the sun and focus light on a heat absorber on top of the tower where molten salt is heated to drive a steam-turbine electric generator.

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Photovoltaic Solar Energy

• During the past 25 years, efficiency of energy capture by photovoltaic cells has increased from less than 1% of incident light to more than 10% in field conditions, and 75% in laboratory conditions.– Invention of amorphous silicon collectors has allowed

production of lightweight, cheaper cells.

• Photovoltaic cells capture solar energy and convert it directly to electrical current by separating electrons from parent atoms and accelerating them across a one-way electrostatic barrier.– Bell Laboratories - 1954

• 1958 - $2,000 / watt• 1970 - $100 / watt• 2002 - $5 / wattApril 21, 2023

Photovoltaic energy -solar energy converteddirectly to electricalcurrent

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Transporting & Storing Electrical Energy

• Electrical energy storage is difficult and expensive.– Lead-acid batteries are

heavy and have low energy density.

• Typical lead-acid battery sufficient to store electricity for an average home would cost $5,000 and weigh 3-4 tons.

– Pumped-Hydro Storage

– Flywheels

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•Distributional Surcharges–Small charge levied on all utility customers to help finance research and development.

•Renewable Portfolio–Mandate minimum percentage of energy from renewable sources.

•Green Pricing–Allow utilities to profit from conservation programs and charge premium prices for energy from renewable sources.

Promoting Renewable Energy

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