esrm 100 2010feb10 ch12benergy web

Energy• Energy Sources and Uses• Coal - Oil - Natural Gas• Nuclear Power• Conservation• Solar Energy

– Photovoltaic Cells

• Fuel Cells• Energy From Biomass• Energy From Earth’s Forces

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Conserving Energy

• Minimize use

• Use energy more efficiently

• Cogeneration - use waste heat from industry to heat water and generate electricity

Buying energy-efficient appliances can cut your energy consumption considerably.

Heat Losses

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High heat losses = white, red, orange(Miller 2006)

Increasing Home Insulation

Standard Insulation in U.S. homes = R-12 – R-19 Super-Insulated Homes = R-25 – R-60Super-insulated homes in Sweden use 90% less energy for heating and cooling than typical homes in the U.S.

Mesa Verde NP (SW USA) – many energy efficient features

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Domestic Energy Efficiency

Earth-sheltered house in Taos, New Mexico

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Renewable Energies:SOLAR ENERGY

• Average amount of solar energy arriving on top of the atmosphere is 1,330 watts per square meter.– Amount reaching the earth’s surface is

10,000 times more than all commercial energy used annually.• Until recently, this energy source has been

too diffuse and low intensity to capitalize for electricity. 7

Solar Energy

• Passive Solar Heat - Using absorptive structures with no moving parts to gather and hold heat.– Greenhouse Design

• Active Solar Heat - Generally pump heat-absorbing medium through a collector, rather than passively collecting heat in a stationary object.

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Underground massive heat storage unit

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Passive Solar Active Solar

http://en.wikipedia.org/wiki/File:PS10_solar_power_tower.jpg

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http://en.wikipedia.org/wiki/File:Moody_Sunburst.jpg

Solar troughs

Concentrating Solar Power (CSP)

http://en.wikipedia.org/wiki/File:Dish_Stirling_Systems_of_SBP_in

_Spain.JPG

Parabolic Dishes

Solar Power Towers

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Solar Ponds

Ocean Thermal Electric Conversion (OTEC) Plant

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Average Daily Solar

Radiation

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Photovoltaic Cells

• 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 40+% in laboratory conditions.

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Photovoltaic Cells

• However consider energy needed to produce cells (1970s required as much energy to produce cells as they could produce in their 20 yr lifetime)!

• Also total emissions were about 2x that emitted by other power plants 10 yrs ago. LIFE CYCLE ANALYSIS– But today lower emissions produced by PV cells for

equivalent amount of energy produced by other power plants (2-11%).

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Photovoltaic Cells Invention of amorphous silicon collectors

has allowed production of lightweight, cheaper cells.

dye-sensitized solar cell (DSSC or DSC) - relatively new class of low-cost solar cell, that belong to the group of Thin film solar cells (3rd generation technology)

????

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Costs for alternativeand renewable energy sources have dropped in recent years and the efficiencies have increased.

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Storing Electrical Energy

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

low energy density. (lithium ion better)• 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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Fuel Cells

• Fuel cells - use ongoing electrochemical reactions to produce an electrical current

• Oxygen, hydrogen• Reformers• Efficiency- 70%

theoretically but practically around 40-45%?

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Fuel Cell Electric

Car

Typical fuel cell efficiency is 40-45%.

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BIOMASS

• Wood provides less than 1% of US energy, but provides up to 90% in poorer countries.

– 1,500 million cubic meters of fuelwood collected in the world annually.

• Inefficient burning of wood produces smoke laden with fine ash and soot and hazardous amounts of carbon monoxide (CO) and hydrocarbons (silent killer).

• However it produces fewer sulfur gases, and burns at lower temperature than coal therefore fewer NOx.

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Fuel wood Crisis in Less-Developed Countries

• About 40-50% of the world’s population depends on firewood and charcoal as their primary energy source.

• Supplies diminishing

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Using Dung as Fuel

• 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. 24

Swedish workers harvesting marsh reeds for biomass energy

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• Modern waste-processing facilities may convert organic waste into methane (biogas) using microorganisms in “digestion” chambers.

Using Methane as Fuel

Anaerobic Fermentation 28

Alcohol from Biomass

Ethanol - grain alcohol Methanol - wood alcohol

• Gasohol - a mixture of gasoline and alcohol - reduced CO emissions

• Biodiesel – plant oils (10% methanol)

• Ethanol production could be a solution to grain surpluses or a competition for grain.

• Both methanol and ethanol make good fuel for fuel cells.

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Water Power• Stored form of solar energy – hydrologic cycle is driven by the sun

• Hydroelectric power plants use water that falls from reservoirs behind high dams

• Provides 10% of US electricity supply, 25% of global power

Energy from the Earth’s Forces

• Water power produces 25% of the world’s electricity (10% US).

• Clean, renewable energy

• Dams - social and ecological damage

Hydropower

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Disadvantages of Hydropower

• Increased loss of water to evaporation• Human Displacement• Ecosystem Destruction• Flooding of large tracts of land• Sedimentation• Herbicide Contamination• Nutrient Flow Retardation• CO2 emissions• Block the migration of fish (salmon, sturgeon)• Alters river ecology and destroys wetland habitat

• Future growth of large-scale water power will be limited• Many existing dams may be removed to restore ecosystems and

species

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Wind Power• Historically used by sailing ships, and windmills to grind

grain and pump water

• Wind power is one of the fastest-growing sources of energy, doubling nearly every three years

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• Wind results from differential solar heating of the Earth surfaces.

• Abundant in coastal and offshore areas, plains, ridges, mountain passes

• The U.S. produces 6700 megawatts (MW) per year, mostly in California. World production of wind power in 2005 was about 47,300 MW, of which about two thirds was in Europe.

• Increasing by about 30% per year, and can be produced at 5c per kWh – competitive with natural gas powered electricity

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Disadvantages of Wind Power

• Bird and bat deaths from collisions with blades

• Interrupt view in remote places or destroy sense of isolation

• Cannot place w/i 70 km of military airbases, etc

• Sources vary geographically

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• Natural heat from Earth’s interior.

• Can be converted to heat buildings and to produce steam for generating electricity.

• Total worldwide production is approaching 9000 MW - less than 0.15% of the total energy supply

Geothermal Energy

• Have long life-span and

• no mining needs, so

• little waste disposal, but

potential danger of noxious gases, and

noise problems from steam valves.

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Tidal Energy

• Requires a high tide/low-tide differential of several meters

• Saltwater flooding behind the dam and heavy siltation

• Locations w/ large waves?

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• Concerns over hydrological changes to estuary, and restriction of fish movements

Wave Power!!

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Promoting Renewable Energy

• 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.

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Loss of power in transmission: Move from Centralized to Decentralized power systems?

Small scale micropower

systems

• Less losses in long transmission

• Fewer people affected by blackouts

• Less vulnerable to terrorism and other disasters

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Roof– solar cellsLandscape-berm,

trees on NInterior-wood,

carpetLiving Machine-

H2O purificationPond-irrigation waterLighting-facing sun 45

Careek Park?Oberlin Coll - 79% less Energy

Carbon Capture Sequestration (CCS)

http://en.wikipedia.org/wiki/File:Carbon_sequestration.jpg

Coal gasification with CCS is

promising. It does drastically reduce

CO2 but also is linked with an increase in air pollution (SOx,

NOx)

http://en.wikipedia.org/wiki/File:GenIVRoadmap.jpg

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Nuclear Energy Development Roadmap

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Steps to Energy Conservation

• Limit fuel use by walking, bicycling, taking a bus or train, car-pooling, or purchasing a hybrid vehicle

• Turn off lights when not in use and fit compact fluorescent lamps

• Take shorter showers to conserve hot water• Put on a sweater and turn down the thermostat in

winter• Choose energy-efficient appliances • Switch to solar power in homes and offices.

Future?

An Alternative

Energy Future? 4949

Present

Summary:Energy Sources and Uses:• Fossil Fuels (Coal, Oil, Natural Gas) are non-renewable and we

need to decrease our dependence on them.• Nuclear Power has many disadvantages but with today’s

technology and the future?• Conservation can/should be practiced at all levels from individuals

to governments.• Solar Energy is becoming more economical.• Fuel Cells can help us decentralize power and perhaps be used in

vehicles.• Energy From Biomass can help us decrease use of fossil fuels now

and is ‘carbon neutral’ relative to inputs of CO2 from fossil fuels.• Energy From Earth’s Forces (hydro, wind, tidal, wave,

geothermal) can help decrease our dependence upon fossil fuels but even with better technology these energies may still be limited spatially and/or temporally.

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