renewable energy and conservation chapter 12. direct solar energy i. direct solar energy a....

Renewable Energy Renewable Energy and Conservationand Conservation

Chapter 12Chapter 12

Direct Solar EnergyDirect Solar Energy

I. Direct Solar EnergyI. Direct Solar EnergyA. Availability:A. Availability:

Solar energy is dispersed over Solar energy is dispersed over the Earth’s surface, but the Earth’s surface, but varies varies in intensityin intensity depending on depending on latitude, season, time of day latitude, season, time of day and degree of cloud cover; for and degree of cloud cover; for solar energy to be useful, we solar energy to be useful, we must must collectcollect it it

B. Cost:B. Cost:Although initial costs associated Although initial costs associated with converting to solar power with converting to solar power are high, are high, the long-term savings the long-term savings may offset the high start-up may offset the high start-up costscosts; efficiency of collecting ; efficiency of collecting systems is also increasing, systems is also increasing, making it a more cost effective making it a more cost effective alternativealternative

Direct Solar EnergyDirect Solar EnergyC. Uses:C. Uses:

1. Passive solar heating1. Passive solar heatinga.. Uses a.. Uses infrared infrared

radiationradiation (waves of heat energy) to (waves of heat energy) to heat buildings without the need for heat buildings without the need for pumps or fans to distribute the pumps or fans to distribute the collected heatcollected heat

b. May utilize b. May utilize south-south-facing windows, floors of concrete facing windows, floors of concrete or stone, and excellent insulationor stone, and excellent insulation

2. Active solar heating2. Active solar heatinga. Uses a series of a. Uses a series of

collection devicescollection devices mounted on a mounted on a roof or in a field to gather solar roof or in a field to gather solar energyenergy

b. Used primarily b. Used primarily for for heating waterheating water – heat absorbed is – heat absorbed is transferred to a liquid inside the transferred to a liquid inside the panel which is then pumped to a panel which is then pumped to a heat exchanger, where the heat is heat exchanger, where the heat is transferred to water that will be transferred to water that will be stored in a hot water tankstored in a hot water tank


3. Solar thermal electric 3. Solar thermal electric generationgeneration

a. Systems that a. Systems that collect incident sunlight and collect incident sunlight and concentrate it, using mirrors or concentrate it, using mirrors or lenseslenses, to heat a working fluid to , to heat a working fluid to high temperatures; water is high temperatures; water is converted to steam, which turns a converted to steam, which turns a turbine to generate electricityturbine to generate electricity

b. Usually have a b. Usually have a backup (such as natural gas) that is backup (such as natural gas) that is available to generate electricity available to generate electricity at at night and on cloudy daysnight and on cloudy days

c. With improved c. With improved engineering, manufacturing, and engineering, manufacturing, and construction methods, solar thermal construction methods, solar thermal energy may become energy may become cost-cost-competitivecompetitive with fossil fuels with fossil fuels


4. Photovoltaic solar cells4. Photovoltaic solar cellsa. a. Wafers or thin films Wafers or thin films

of solid state materialsof solid state materials that are treated that are treated with certain metals in such a way that with certain metals in such a way that they generate electricity (a flow of they generate electricity (a flow of electrons) when solar energy is electrons) when solar energy is absorbedabsorbed

b. Can be used on any b. Can be used on any scale scale – small, portable modules to – small, portable modules to large power plantslarge power plants

c. Produce c. Produce no no pollutionpollution, require minimal maintenance, require minimal maintenance


d. Only about d. Only about 10-15% efficient at 10-15% efficient at converting solar energy to converting solar energy to electricity, but efficiencies electricity, but efficiencies are are improvingimproving

e. e. Future Future technological progresstechnological progress may make PVs may make PVs economically competitive economically competitive with electricity produced by with electricity produced by conventional sourcesconventional sources

Direct Solar EnergyDirect Solar Energy5. Solar-Generated Hydrogen5. Solar-Generated Hydrogena. Electricity generated by PVs a. Electricity generated by PVs

(or any energy source) can (or any energy source) can be used to split water into be used to split water into oxygen and hydrogenoxygen and hydrogen

b. Hydrogen is a b. Hydrogen is a clean fuelclean fuel, , producing very little air producing very little air pollution (minimal amounts pollution (minimal amounts of nitrogen oxides are of nitrogen oxides are produced)produced)

c. Hydrogen offers a convenient c. Hydrogen offers a convenient way to way to store solar energy store solar energy as chemical energyas chemical energy; can be ; can be easily transported by easily transported by pipelinepipeline

d. Hydrogen d. Hydrogen fuel cellsfuel cells (similar to (similar to batteries) may be used to batteries) may be used to power automobilespower automobiles

Indirect Solar EnergyIndirect Solar EnergyII. Indirect Solar EnergyII. Indirect Solar Energy

A. BiomassA. Biomass

1. Consists of 1. Consists of wood, crop wood, crop wastes, and animal wastes, and animal dungdung containing containing chemical energy chemical energy that can be traced to that can be traced to the sun (radiant the sun (radiant energy used by energy used by photosynthetic photosynthetic organisms to form organisms to form the organic the organic molecules of molecules of biomass)biomass)

Indirect Solar EnergyIndirect Solar Energy2. Availability:2. Availability:

a. A renewable a. A renewable source of energy, source of energy, as long as it is as long as it is managed managed properlyproperly

b. At least b. At least ½½ of the of the world’s world’s population relies population relies on biomass as on biomass as their main source their main source of energyof energy

3. Cost:3. Cost:Converting Converting

biomass to biomass to liquid fuelsliquid fuels is is expensive and overall expensive and overall efficiency is lowefficiency is low

Indirect Solar EnergyIndirect Solar Energy4. Types:4. Types:

a. a. CombustionCombustion of wood of woodb. b. BiogasBiogas – a mixture of – a mixture of

gases produced by gases produced by biomass, mostly animal biomass, mostly animal waste; easy to store waste; easy to store and transport, and and transport, and burns cleanlyburns cleanly

c. Liquid fuels such as c. Liquid fuels such as ethanol and methanolethanol and methanol can also be produced can also be produced from corn, sugar cane from corn, sugar cane or even agricultural or even agricultural wastes and used in wastes and used in internal combustion internal combustion engines (gasohol – engines (gasohol – alcohol mixed with alcohol mixed with gasoline)gasoline)

Indirect Solar EnergyIndirect Solar Energy5. Advantages:5. Advantages: a. Reduces dependence on a. Reduces dependence on fossil fossil

fuelsfuels b. Often makes use of b. Often makes use of wasteswastes, ,

reducing our waste disposal reducing our waste disposal problemproblem

c. Reduced c. Reduced air pollutionair pollution problems problems (as compared to fossil fuels)(as compared to fossil fuels)

6. Environmental Impact:6. Environmental Impact: a. Requires a. Requires land and waterland and water, shifting , shifting

its use from food productionits use from food production b. Intensive use of wood as fuel b. Intensive use of wood as fuel

contributes to contributes to deforestation, deforestation, erosion, and desertificationerosion, and desertification

c. Removal of crop residues for c. Removal of crop residues for biomass fuel exposes soil to biomass fuel exposes soil to erosion and deprives the land of erosion and deprives the land of nutrient enrichment nutrient enrichment from from decompositiondecomposition

Indirect Solar EnergyIndirect Solar EnergyB. Wind EnergyB. Wind Energy

1. Wind results from the warming 1. Wind results from the warming of the atmosphere by the sun; of the atmosphere by the sun; radiant energy of the sun is radiant energy of the sun is transformed into transformed into mechanical mechanical energyenergy

2. Availability:2. Availability:Wind is Wind is sporadicsporadic

over the surface of the Earth, and over the surface of the Earth, and varies in direction and magnitude; varies in direction and magnitude; must be harnessed to be usefulmust be harnessed to be useful

3. Cost:3. Cost:As turbines have As turbines have

become larger and more efficient, become larger and more efficient, costs for wind power have declined costs for wind power have declined rapidly; currently the rapidly; currently the most cost-most cost-competitivecompetitive of all forms of renewable of all forms of renewable energyenergy

4. Mechanism:4. Mechanism:Wind turbines spin a Wind turbines spin a

drive shaftdrive shaft, powering a generator that , powering a generator that sends electricity to nearby utilitiessends electricity to nearby utilities

Indirect Solar EnergyIndirect Solar Energy5. Advantages:5. Advantages:

Produces Produces no waste / no waste / emissionsemissions – a – a

clean clean source of source of energyenergy

6. Environmental impact:6. Environmental impact:a. a. Birds collideBirds collide with the with the

turbines; should be located turbines; should be located away from migratory away from migratory routesroutes

b. b. Aesthetically displeasingAesthetically displeasing; ; may be combined with may be combined with pasture land, or located pasture land, or located offshore to utilize ocean offshore to utilize ocean windswinds

Indirect Solar EnergyIndirect Solar EnergyC. HydropowerC. Hydropower

1. The sun’s energy drives the 1. The sun’s energy drives the hydrologic cyclehydrologic cycle; as water ; as water flows from higher elevations flows from higher elevations back to sea level, we can back to sea level, we can harness its energyharness its energy

2. Availability:2. Availability:a. Currently, hydropower a. Currently, hydropower

generates generates ~19%~19% of the of the world’s electricity (9% of world’s electricity (9% of the US’s energy)the US’s energy)

b. Highly developed b. Highly developed countries have already countries have already built dams at most of their built dams at most of their potential sites, but still potential sites, but still represents a great represents a great potential source of potential source of electricity in the electricity in the developing worlddeveloping world

3. Cost:3. Cost:Dams cost a great deal to Dams cost a great deal to

buildbuild but are relatively inexpensive but are relatively inexpensive to to operateoperate; also have a ; also have a limited limited lifespanlifespan (50-200 years) due to (50-200 years) due to siltation of the reservoirsiltation of the reservoir

Indirect Solar EnergyIndirect Solar Energy4. Mechanism:4. Mechanism:

The potential energy of water The potential energy of water held back by a dam is converted to kinetic held back by a dam is converted to kinetic energy as water falls down a energy as water falls down a penstockpenstock, where it , where it turns a turbine to generate electricityturns a turbine to generate electricity

5. Advantages:5. Advantages:Produces Produces no waste/emissionsno waste/emissions – –

a clean source of energya clean source of energy6. Environmental Impact:6. Environmental Impact:

a. Formation of a reservoir (by damming a a. Formation of a reservoir (by damming a river) river) destroys plant and animal destroys plant and animal habitats and displaces peoplehabitats and displaces people

b. Alteration of the river affects native b. Alteration of the river affects native fishes, especially fishes, especially migratorymigratory species species

c. c. Seismic activitySeismic activity may be induced by may be induced by filling a reservoirfilling a reservoir

d. Dams d. Dams trap silttrap silt carried by the river, carried by the river, preventing nutrient-enrichment of preventing nutrient-enrichment of agricultural land downstream and agricultural land downstream and decreasing productivitydecreasing productivity

Indirect Solar EnergyIndirect Solar Energy

D. Ocean Waves and Temperature D. Ocean Waves and Temperature GradientsGradients

1. Ocean waves are 1. Ocean waves are produced by produced by windswinds, which are caused by the , which are caused by the sunsun

a. A concrete, hollow a. A concrete, hollow power plant box is sunk into a gulley power plant box is sunk into a gulley off the coast to catch waves; as each off the coast to catch waves; as each new wave enters the chamber, the new wave enters the chamber, the rising water in the chamber pushes air rising water in the chamber pushes air into a vent that contains a turbine, into a vent that contains a turbine, causing the turbine to spincausing the turbine to spin

b. More testing and b. More testing and improvements in design are needed improvements in design are needed before this technology can be widely before this technology can be widely implementedimplemented

Indirect Solar EnergyIndirect Solar Energy2.2. Ocean Thermal Energy Ocean Thermal Energy

Conversion (OTEC) involves the Conversion (OTEC) involves the generation of electricity by using generation of electricity by using the the differences in temperature at differences in temperature at various ocean depthsvarious ocean depths (temperature (temperature gradients)gradients)

a. Warm surface water is a. Warm surface water is pumped into a power plant where it pumped into a power plant where it heats a liquid (such as ammonia) heats a liquid (such as ammonia) to the boiling point; the ammonia to the boiling point; the ammonia steam drives a turbine to generate steam drives a turbine to generate electricity as ammonia is cooled by electricity as ammonia is cooled by the very cold water brought up the very cold water brought up from the ocean depthsfrom the ocean depths

b. Only about 3-4% efficient, b. Only about 3-4% efficient, costly, and may have costly, and may have extreme extreme consequences on marine consequences on marine ecosystemsecosystems

Other Renewable Energy Other Renewable Energy SourcesSources

III. Other Renewable Energy SourcesIII. Other Renewable Energy Sources

A. Tidal energyA. Tidal energy

1. In areas where the difference in 1. In areas where the difference in water level between high and water level between high and low tides is great enough, it is low tides is great enough, it is possible to possible to build a dam across build a dam across a baya bay and harness this energy and harness this energy

2. Availability:2. Availability:

Cannot become a significant Cannot become a significant resource worldwide because resource worldwide because few geographical locations few geographical locations have a have a large enough differencelarge enough difference between high and low tidesbetween high and low tides

3. Cost:3. Cost:

Very expensive to build, but Very expensive to build, but relatively low operating costsrelatively low operating costs


4. Mechanism:4. Mechanism:The dam’s floodgates are The dam’s floodgates are

opened as high tide raises the opened as high tide raises the water on the bay side, then the water on the bay side, then the floodgates are closed; as the tide floodgates are closed; as the tide falls, falls, water flowing back out to the water flowing back out to the ocean over the dam’s spillway is ocean over the dam’s spillway is used to turn a turbine and used to turn a turbine and generate electricitygenerate electricity

5. Advantages:5. Advantages:No waste products / No waste products /

emissionsemissions; a clean source of ; a clean source of energyenergy

6. Environmental Impact:6. Environmental Impact:Building a dam across the Building a dam across the

mouth of an estuary would prevent mouth of an estuary would prevent many ocean organisms from many ocean organisms from reaching their reaching their breeding groundsbreeding grounds

Other Renewable Energy Other Renewable Energy SourcesSourcesB. Geothermal EnergyB. Geothermal Energy

1. Large, underground 1. Large, underground reservoirs of heat exist in reservoirs of heat exist in areas of geologically areas of geologically recent volcanismrecent volcanism; ; hydrothermal reservoirshydrothermal reservoirs (formed when heated (formed when heated groundwater is trapped by groundwater is trapped by impermeable layers in the impermeable layers in the Earth’s crust) contain hot Earth’s crust) contain hot water and possibly steam water and possibly steam


2. Availability:2. Availability:

a. The US is the world’s largest a. The US is the world’s largest producer of geothermal producer of geothermal electricity from hydrothermal electricity from hydrothermal reservoirs, but other countries reservoirs, but other countries (such as Iceland) also use this (such as Iceland) also use this type of electricity to power type of electricity to power many homesmany homes

b. Scientists are also studying b. Scientists are also studying how to extract some of the how to extract some of the geothermal energy found in geothermal energy found in hot, dry rockshot, dry rocks of the Earth; of the Earth; would make this form of energy would make this form of energy production more widely production more widely availableavailable


3. Cost:3. Cost:Installation of different types of Installation of different types of

geothermal systems may be expensive, geothermal systems may be expensive, but have low operating costs and but have low operating costs and high high efficiencyefficiency

4. Types:4. Types:a. a. Geothermal wellsGeothermal wells – hot fluid is – hot fluid is

brought to the surface and the brought to the surface and the resulting steam is expanded resulting steam is expanded through a turbine to spin a through a turbine to spin a generator, creating electricitygenerator, creating electricity

b. b. Geothermal heat pumpsGeothermal heat pumps – use – use an underground arrangement an underground arrangement of pipes containing circulating of pipes containing circulating fluids to extract natural heat in fluids to extract natural heat in winter and transfer excess winter and transfer excess heat in summerheat in summer

Other Renewable Energy Other Renewable Energy SourcesSources 5. Advantages:5. Advantages:

Emits a fraction of Emits a fraction of air pollutants of fossil fuel air pollutants of fossil fuel based technologies, and based technologies, and entails entails minimal land useminimal land use

6. Environmental Impact:6. Environmental Impact:a. The water used to a. The water used to

transfer transfer geothermal heat to geothermal heat to the surface is not the surface is not inexhaustible – inexhaustible – must be must be recirculatedrecirculated to to ensure renewable ensure renewable energyenergy

b. May emit b. May emit hydrogen hydrogen sulfide gassulfide gas

Energy Solutions: Conservation Energy Solutions: Conservation and Efficiencyand Efficiency

IV. Energy Solutions: Conservation and EfficiencyIV. Energy Solutions: Conservation and Efficiency

A. Conservation vs. EfficiencyA. Conservation vs. Efficiency

1. Conservation – 1. Conservation – moderating or moderating or eliminatingeliminating wasteful or unnecessary wasteful or unnecessary energy-consuming activitiesenergy-consuming activities

Ex. Ex. carpooling, lowering driving carpooling, lowering driving speedsspeeds

2. Efficiency – 2. Efficiency – using technologyusing technology to to accomplish a particular task with accomplish a particular task with less energyless energy

Ex. Ex. designing and manufacturing designing and manufacturing more fuel-efficient automobilesmore fuel-efficient automobiles

Energy Solutions: Energy Solutions: Conservation and EfficiencyConservation and Efficiency

B. B. Energy intensityEnergy intensity – a country’s or – a country’s or region’s total energy region’s total energy consumption divided by is consumption divided by is GDPGDP

a. In developed countries, a. In developed countries, energy intensity is energy intensity is considerably higher in considerably higher in the the US and CanadaUS and Canada than in than in Japan and EuropeJapan and Europe

b. Energy intensity in b. Energy intensity in developing countries is developing countries is substantially less than it is substantially less than it is in industrialized countries, in industrialized countries, but the greatest increase in but the greatest increase in energy consumption is in energy consumption is in developing nations (developing nations (as as countries boost their countries boost their economic development, economic development, energy demands increaseenergy demands increase))


C. Energy-efficient technologiesC. Energy-efficient technologies

1. Homes, Cars, and 1. Homes, Cars, and Industries:Industries:

a. a. Compact fluorescent Compact fluorescent lightbulbslightbulbs require require 25% of the energy 25% of the energy used by incandescent used by incandescent lightbulbs and last 9x lightbulbs and last 9x longerlonger

b. “b. “SuperinsulatedSuperinsulated” ” homes use 70-90% homes use 70-90% less heat than those less heat than those insulated by standard insulated by standard methodsmethods


C. Appliances:C. Appliances:

i) National Appliance Energy i) National Appliance Energy Conservation Act Conservation Act (NAECA) sets national (NAECA) sets national appliance standards appliance standards for major home for major home appliancesappliances

ii) Requires manufacturers to ii) Requires manufacturers to provide provide Energy Guide Energy Guide labelslabels on all new on all new appliances to provide appliances to provide estimates of annual estimates of annual operating costsoperating costs

Energy Solutions: Energy Solutions: Conservation and EfficiencyConservation and Efficiencyd. Automobile efficiency has d. Automobile efficiency has

improved dramatically as a improved dramatically as a result of the use of result of the use of lighter lighter materialsmaterials and designs that and designs that reduce reduce air dragair drag

e. New aircraft are much more e. New aircraft are much more fuel-fuel-efficientefficient than older models than older models

f. Technological improvements in f. Technological improvements in the paper making industry the paper making industry translates to translates to increased profitsincreased profits for manufacturersfor manufacturers

2. Cogeneration / 2. Cogeneration / Combined Heat and Combined Heat and PowerPower (CHP) - involves the (CHP) - involves the production of two useful forms of production of two useful forms of energy from the same fuel; energy from the same fuel; typically involves the typically involves the generation of generation of electricityelectricity, and then the , and then the steam steam produced during the process is produced during the process is used rather than wastedused rather than wasted


3. Commercial Buildings – energy 3. Commercial Buildings – energy costs usually account for ~30% costs usually account for ~30% of a company’s operating budget of a company’s operating budget but those housed in older but those housed in older buildings don’t have the benefit buildings don’t have the benefit of new technologies; of new technologies; energy-energy-services companiesservices companies assess how assess how to improve energy efficiency, to improve energy efficiency, provide funding for provide funding for improvements, then are paid by improvements, then are paid by energy savingsenergy savings

D. Electric Power Companies and Energy D. Electric Power Companies and Energy EfficiencyEfficiency

1. 1. Demand-side ManagementDemand-side Management - - electric companies help electric companies help consumers save energy; may consumers save energy; may offer offer cash awardscash awards for installation for installation of energy-efficient technologies of energy-efficient technologies or may give consumers compact or may give consumers compact fluorescent lightbulbs, air fluorescent lightbulbs, air conditioners, or other appliances conditioners, or other appliances in exchange for a in exchange for a slightly higher slightly higher raterate


2. Electricity 2. Electricity DeregulationDeregulation – – competitive utilities are competitive utilities are more likely than regulated more likely than regulated monopolies to adopt monopolies to adopt technological advances that technological advances that increase energy efficiency increase energy efficiency and thereby lower costsand thereby lower costs

E. Energy Conservation at the E. Energy Conservation at the Individual LevelIndividual Level

1. Lower 1. Lower thermostat thermostat in winter in winter and raise it in summerand raise it in summer

2. Turn off 2. Turn off lights lights when you leave when you leave a rooma room

3. Drive more 3. Drive more slowlyslowly4. Utilize 4. Utilize carpoolingcarpooling or or public public

transportationtransportation

renewable energy and conservation chapter 12. direct solar energy i. direct solar energy a....

Documents