Renewable Energy Chapter 16

Core Case Study: Iceland’s Vision of a Renewable-Energy Economy Supplies 75% of its primary energy and almost all of its electrical energy using – Geothermal energy – Hydroelectric power No fossil fuel deposits – imports oil

Wasted Energy Energy Conservation - Energy Efficiency -

The Second Law of Thermodynamics in Living Systems

Wasted Energy Four widely used devices that waste energy

Fig. 16-4, p. 404 Solutions Improving Energy Efficiency Prolongs fossil fuel supplies Reduces oil imports and improves energy security Very high net energy yield Low cost Reduces pollution and environmental degradation Buys time to phase in renewable energy Creates local jobs

Flow of Commercial Energy through the U.S. Economy

Net Energy is the Energy That Counts

We Can Improve Energy Efficiency and Save Money in Transportation Hidden prices in gasoline – Should be $12/gallon – Car manufacturers and oil companies lobby to prevent laws to raise fuel taxes Build or expand mass transit and high speed rail Encourage biking

High Speed Magnetic Train

More Energy-Efficient Vehicles Are on the Way Superefficient and ultralight cars Gasoline-electric hybrid car Plug-in hybrid electric vehicle Energy-efficient diesel car Electric vehicle with a fuel cell

Stepped Art Conventional hybridFuel tank Battery Internal combustion engine TransmissionElectric motor Plug-in hybrid Fuel tank Battery Internal combustion engine Transmission Electric motor

We Can Design Buildings That Save Energy and Money Green Architecture Green Roofs (Living Roof) Blue Roof Superinsulation

Green Architecture

Green Roof

Green Wall

Blue Roof

Los Angeles River

Houses out of bottles?

What is Renewable Energy? Renewable energy is energy from sources that are constantly being formed. Renewable energy includes:

Fig , p. 412 Available Energy Flow (exajoules per year) World energy use (2010) Direct solar Wind Geothermal Biomass Hydropower Ocean < >1, <250

Solar Energy Passive solar heating – Active solar heating –

Solutions: Passive and Active Solar Heating for a Home

Fig , p. 415 Trade-Offs Passive or Active Solar Heating AdvantagesDisadvantages Net energy is moderate (active) to high (passive) Need access to sun 60% of time during daylight Very low emissions of CO 2 and other air pollutants Sun can be blocked by trees and other structures High installation and maintenance costs for active systems Very low land disturbance Moderate cost (passive) Need backup system for cloudy days

Passive Heating and Homes Passive solar buildings have large windows that face south. Solar energy enters the windows and warms the house. Must be well insulated

Active Solar Heating Solar energy can be used to heat water and generate electricity.

Photovoltaic (PV) Cells Photovoltaic cells(PV) = solar cells Cons: – Produce only a little bit of energy – Expensive – Energy produced must be stored in batteries

Fig , p. 419 Solar Cells AdvantagesDisadvantages Medium net energy yield Need access to sun Little or no direct emissions of CO 2 and other air pollutants Need electricity storage system or backup Easy to install, move around, and expand as needed Costs high for older systems but dropping rapidly Solar-cell power plants could disrupt desert ecosystems Competitive cost for newer cells Trade-Offs Some designs have low net energy yield

Wind Energy Wind farms – large arrays of wind turbines Reminder- wind caused by the uneven heating of Earth’s surface Wind energy is the fastest growing source of electricity in the world

Fig. 16-1a, p. 402 Gearbox Electrical generator Power cable Wind turbine

Wind Energy Controversy: Cape Wind

Fig. 16-1b, p. 402

Fig , p. 423 Trade-Offs Wind Power AdvantagesDisadvantages High net energy yield Needs backup or storage system when winds die down Low electricity cost Visual pollution for some people Low-level noise bothers some people Can kill birds if not properly designed and located Widely available Easy to build and expand Little or no direct emissions of CO 2 and other air pollutants

Advantages of Wind Energy Easy and quick start up – new turbine takes about 3 months to put up Wind energy is cheap and abundant Have the potential to generate a LOT of energy Turbines don’t take up much space so the land can be used for other things as well, such as farming.

Biomass Biomass fuel - Plant material, manure, and any other organic matter that is used as an energy source Wood and dung (both biomass fuel), are major sources of energy in developing countries.

Biomass Fuel

Solid Biomass AdvantagesDisadvantages Widely available in some areas Contributes to deforestation Clear-cutting can cause soil erosion, water pollution, and loss of wildlife habitat No net CO 2 increase if harvested, burned, and replanted sustainably Medium net energy yield Plantations can help restore degraded lands Trade-Offs Increases CO 2 emissions if harvested and burned unsustainably Can open ecosystems to invasive species Moderate costs

Methane Methane can be burned to generate heat or electricity. In China, more than 6 million households use biogas digesters to ferment manure and produce gas used for heating and cooking.

Hydroelectricity Hydroelectricity - energy produced from moving water,

Hydroelectricity

Benefits of Hydroelectricity Do not release air pollutants that cause acid precipitation. Last longer than fossil fuel powered plants.

Disadvantages of Hydroelectricity Dams can alter the flow of a river, disrupting downstream ecosystems Present a flood risk if the dam leaks or breaks

Large-Scale Hydropower AdvantagesDisadvantages High net energy yield Large land disturbance and displacement of people Low-cost electricity High CH 4 emissions from rapid biomass decay in shallow tropical reservoirs Low emissions of CO 2 and other air pollutants in temperate areas Disrupts downstream aquatic ecosystems Trade-Offs Large untapped potential

Modern Trends Hydroelectricity Micro-hydropower - electricity produced in a small stream without having to build a big dam. Uses a small turbine floating in a stream/river, does not disrupt the flow of the water or a small

Micro-hydropower

Geothermal Energy Geothermal energy - energy from heat in the Earth’s crust This heat can be used to generate electricity

Geothermal Energy Fig a, p. 428 Production well Geothermal reservoir Injection well Heat exchanger Steam turbine Generator 2. Heat from underground spins a turbine to power a generator and produce electricity 1. Hot water or steam is pumped under pressure to the surface from underground 3. Steam from turbine condenses to water and is pumped back down to geothermal reservoir

Fig , p. 430 Geothermal Energy AdvantagesDisadvantages Medium net energy yield and high efficiency at accessible sites High cost except at concentrated and accessible sites Lower CO 2 emissions than fossil fuels Scarcity of suitable sites Low cost at favorable sites Noise and some CO 2 emissions Trade-Offs

Alternative Energy and Conservation Section 2

What is alternative energy? Alternative energy - describes energy sources that are still in development. The source must be proven to be cost effective. The environmental effects of using the energy source must be acceptable.

Tidal Power Tides are the movement of water in the oceans and seas caused by gravitational attraction between the sun, Earth, and moon. A tidal power plant works much like a hydroelectric dam.

Tidal Power

Potential Problems with Tidal Power The cost of building and maintaining a tidal power plant is high There are few locations that are suitable. May have negative impacts on fragile coastal ecosystems.

Hydrogen Fuel Cells Hydrogen, the most abundant element in the universe, can be burned as a fuel. When burned, water vapor is the byproduct Hydrogen gas (H2) can be produced by using electricity to split molecules of water (H2O).

Fig , p. 430 Electrons Hydrogen gas (H 2 ) in Polymer electrolyte membrane Anode Cathode Protons Water vapor (H 2 O) out Air (O 2 ) in

Potential Problems with Hydrogen Fuel Takes a lot of energy to split water – not energy efficient by today’s standards Water vapor is still a GHG

Fig , p. 432 Trade-Offs Hydrogen AdvantagesDisadvantages Can be produced from plentiful water at some sites Fuel cell Negative net energy yield CO 2 emissions if produced from carbon-containing compounds No CO 2 emissions if produced with use of renewables Good substitute for oil High costs create need for subsidies High efficiency in fuel cells Needs H 2 storage and distribution system

Fig , p. 434