Renewable Energy

Renewable Energy Chapter 18

Shift from Oil to Hydrogen Fuel • Will be used to produce electricity, to run cars & appliances, heat water, heat/cool buildings • Burning hydrogen (adds oxygen) = production of water (not carbon dioxide) • Eliminates air pollution = slows global warming

Energy Efficiency • Measure of the useful energy produced by an energy conversion device compared to the energy that is converted to useless (low quality) heat • 2nd Law of Thermodynamics- 41% of energy used is wasted • US wastes 43% unnecessarily (fuel-wasting, vehicles, furnace, poorly designed/insulated buildings)

Figure 18-2Page 380 Solutions Solutions Reducing Energy Waste Reducing Energy Waste Prolongs fossil fuel supplies Reduces oil imports Very high net energy Low cost Reduces pollution and environmental degradation Buys time to phase in renewable energy Less need for military protection of Middle East oil resources Improves local economy by reducing flow of money out to pay for energy Creates local jobs

Life Cycle Cost • Initial cost plus life-time operating costs • 3 LEAST efficient devices: • Incandescent light bulb • Nuclear power plant • Motor vehicle

Net Energy Efficiency • Determine by efficiency of each step in energy conversion for entire system • Improved by: • Keeping number of conversion steps low • Strive for highest possible energy efficiency for each step

Cogeneration • Combined heat & power system (CHP) • 80-90% efficient • 30-40% for coal/nuclear plants • Energy Savers: • Replace energy-wasting electric motors • Switch from incandescent light bulbs to fluorescent lighting

Saving Energy In Transportation • Increase fuel efficiency • Encourage development of hybrid, fuel cell, or other fuel-saving vehicles • Not in US because • Inflation – adjusted price of gasoline = low price • 2/3 of Americans prefer SUVs, pickup trucks, minivans, & other large inefficient vehicles • CAFE standards have not been raised since 1985

Hidden Costs of Gasoline • Subsidies & tax breaks for oil companies & road builders • Pollution cleanup • Military protection for oil supplies in Middle East • Increased medical bills & insurance premiums • Harmful effects on habitats

Hybrid-Electric Cars + Super efficient (80-300 mpg) + Recharged by internal combustion engine

Figure 18-9Page 385 A C Electric motor Traction drive provides additional power, recovers breaking energy to recharge battery. Combustion engine Small, efficient internalcombustion engine powers vehicle with low emissions. D B Fuel tank Liquid fuel such as gasoline, diesel, or ethanol runs small combustion engine. Battery bank High-density batteries power electric Motor for increased power. E Regulator Controls flow of power between electric Motor and battery pack. F Transmission Efficient 5-speed automatic transmission. B A E F C D Fuel Electricity

Hydrogen-Fuel Cell Cars + Abundant fuel (hydrogen) + 2x efficient + No moving engine parts + Little maintenance + Little or no pollution - Expense - Development needed

Figure 18-10aPage 385 1 2 Hydrogen gas 3 4 H2 Cell splits H2 into protons and electrons. Protons flow across catalyst membrane. 3 1 O2 React with oxygen (O2). 2 Produce electrical energy (flow of electrons) to power car. 4 H2O Emits water (H2O) vapor.

Figure 18-10bPage 385 Fuel cell stack Hydrogen and oxygen combine chemically to produce electricity. Fuel tank Hydrogen gas or liquid or solid metal hydride stored on board or made from gasoline or methanol. A C D B Turbo compressor Sends pressurized air to fuel cell. E Traction inverter Module converts DC electricity from fuel cell to AC for use in electric motors. Electric motor/transaxle Converts electrical energy to mechanical energy to turn wheels. B A E C D Fuel Electricity

Ways to Save Energy in Buildings • Passive solar heating • Superinsulation – like strawbales • Ecoroof (green roof) – plants provide insulation, absorb storm water, outlast conventional roofs

Superinsulated Homes • Heavily insulated & air tight • Heat from direct sunlight, appliances, & human bodies warm home with little or no need for backup heating system • Air-to-air heat exchanger prevents indoor air pollution

R-60 or higher insulation Figure 18-12Page 387 R-30 to R-43 insulation Small or no north-facing windows or superwindows Insulated glass, triple-paned or superwindows (passive solar gain) R-30 to R-43 insulation House nearly airtight R-30 to R-43 insulation Air-to-air heat exchanger

Strawbale House • Walls made by stacking compacted bales of low-cost straw & covering with plaster or adobe

Figure 18-13Page 387 DO NOT POST TO INTERNET

Eco-roof • Covered with green plants • Provides good insulation • Absorbs stormwater & releases slowly • Outlasts conventional roofs • Increases efficiency

Reducing Energy Waste • Insulate & plug leaks • Use energy-efficient windows • Stop other heating & cooling losses (leaky heating & cooling ducts in attics & unheated basements) • More efficient home heating • More efficient water heating • Use energy efficient appliances & lighting • Turn off unused electrical devices • Stricter energy-efficiency standards for new buildings

Four Efficient Home Heating Methods • Superinsulation • Geothermal heat pump • Passive solar heating • Conventional heat pump

Efficient Ways to Heat Water • Tankless instant water heater • Well-insulated, conventional natural gas or LPG water heater • Electric water heaters are inefficient

Not Saving because… • Glut of low-cost oil/gasoline • Lack of sufficient government tax breaks or economic incentives to improve energy efficiency

Passive Solar Heating • Absorbs & stores heat from sun directing with structure + No special equipment needed - Small backup heating system + Cheap heating method - Cannot convert existing homes + 3-7 years payback time

Figure 18-16aPage 389 Summer sun Heavy insulation Superwindow Winter sun Superwindow Stone floor and wall for heat storage PASSIVE

Active Solar Heating • Absorbs energy from sun by pumping heat-absorbing fluid (like water) through collectors - Collectors are expensive + Some collected heat is used directly + Can supply hot water - Maintenance required - Unappealing appearance

Figure 18-16bPage 389 Heat to house (radiators or forced air duct) Pump Heavy insulation Hot water tank Super- window Heat exchanger ACTIVE

Cooling Homes Naturally • Superinsulation & superinsulating windows • Open windows for breezes • Use fans to move air • Block summer sun with deciduous trees or window overhangs (awnings) • Use light colored roof • Suspend reflective insulating foil in attic to block downward radiating heat

Direct Gain Figure 18-17aPage 392 Ceiling and north wall heavily insulated Summer sun Hot air Super insulated windows Winter sun Warm air Cool air Earth tubes

Greenhouse, Sunspace, or Attached Solarium Figure 18-17bPage 392 Summer cooling vent Warm air Insulated windows Cool air

Figure 18-17cPage 392 Earth Sheltered Reinforced concrete, carefully waterproofed walls and roof Earth Triple-paned or superwindows Flagstone floor for heat storage

Figure 18-19Page 393 Trade-Offs Solar Energy for High-Temperature Heat and Electricity Advantages Disadvantages Moderate net energy Moderate environmental Impact No CO2 emissions Fast construction (1-2 years) Costs reduced with natural gas turbine backup Low efficiency High costs Needs backup or storage system Need access to sun most of the time High land use May disturb desert areas

Solar Cell • Photovoltaic (PV) cell- converts solar energy directly into electrical energy

Figure 18-21Page 395 Trade-Offs Solar Cells Advantages Disadvantages Fairly high net energy Work on cloudy days Quick installation Easily expanded or moved No CO2 emissions Low environmental impact Last 20-40 years Low land use (if on roof or built into walls or windows) Reduce dependence on fossil fuels Need access to sun Low efficiency Need electricity storage system or backup High land use (solar cell power plants) could disrupt desert areas High costs (but should be competitive in 5-15 years) DC current must be converted to AC

Hydropower • Large-scale hydropower- high dam built across a large river to create reservoir; water is stored or allowed to flow through huge pipes at controlled rate; spinning turbines & producing electricity • Small-scale hydropower- low dam with little or no reservoir; small high-efficiency turbine in stream without impeding stream navigation or fish movements • Pumped-storage hydropower- pumps use surplus electricity from conventional plant to pump water to lake or reservoir at higher elevation

Trade-Offs Large-Scale Hydropower Advantages Disadvantages Moderate to high net energy High efficiency (80%) Large untapped potential Low-cost electricity Long life span No CO2 emissions during operation May provide flood control below dam Provides water for year-round irrigation of crop land Reservoir is useful for fishing and recreation High construction costs High environmental impact from flooding land to form a reservoir High CO2 emissions from biomass decay in shallow tropical reservoirs Floods natural areas behind dam Converts land habitat to lake habitat Danger of collapse Uproots people Decreases fish harvest below dam Decreases flow of natural fertilizer (silt) to land below dam Figure 18-22Page 396

Wind Power • Winds turn turbine to generate electricity

Figure 18-23aPage 396 Gearbox Electrical generator Power cable Wind Turbine

Figure 18-23bPage 396 Wind Farm

Figure 18-24Page 397 Trade-Offs Wind Power Advantages Disadvantages Moderate to high net energy High efficiency Moderate capital cost Low electricity cost (and falling) Very low environmental impact No CO2 emissions Quick construction Easily expanded Land below turbines can be used to grow crops or graze livestock Steady winds needed Backup systems when needed winds are low High land use for wind farm Visual pollution Noise when located near populated areas May interfere in flights of migratory birds and kill birds of prey

Figure 18-26Page 399 Trade-Offs Solid Biomass Advantages Disadvantages Large potential supply in some areas Moderate costs No net CO2 increase if harvested and burned sustainably Plantation can be located on semiarid land not needed for crops Plantation can help restore degraded lands Can make use of agricultural, timber, and urban wastes Nonrenewable if harvested unsustainably Moderate to high environmental impact CO2 emissions if harvested and burned unsustainably Low photosynthetic efficiency Soil erosion, water pollution, and loss of wildlife habitat Plantations could compete with cropland Often burned in inefficient and polluting open fires and stoves

Figure 18-27Page 399 Trade-Offs Ethanol Fuel Advantages Disadvantages High octane Some reduction in CO2 emission Reduced CO emissions Can be sold as gasohol Potentially renewable Large fuel tank needed Lower driving range Net energy loss Much higher cost Corn supply limited May compete with growing food on cropland Higher NO emission Corrosive Hard to start in colder weather

Geothermal Energy • Consists of heat stored in soil, underground rocks, & fluids in earth’s mantle • Reservoirs (other than near surface) • Molten rock • Hot dry-rock zones- magma penetrates crust & heats subsurface rock (8-10km down) • Warm-water rock

Figure 18-29Page 401 Trade-Offs Geothermal Fuel Advantages Disadvantages Very high efficiency Moderate net energy at accessible sites Lower CO2 emissions than fossil fuels Low cost at favorable sites Low land use Low land disturbance Moderate environmental impact Scarcity of suitable sites Depleted if used too rapidly CO2 emissions Moderate to high local air pollution Noise and odor (H2S) Cost too high except at the most concentrated and accessible source

Figure 18-30Page 401 Trade-Offs Hydrogen Advantages Disadvantages Can be produced from plentiful water Low environmental impact Renewable if produced From renewable energy resources No CO2 emissions if produced from water Good substitute for oil Competitive price if environmental and social costs are included in cost comparisons Easier to store than electricity Safer than gasoline and natural gas Nontoxic High efficiency (65-95%) in fuel cells Not found in nature Energy is needed to produce fuel Negative net energy CO2 emissions if produced from carbon-containing compounds Nonrenewable if generated by fossil fuels or nuclear power High costs (but expected to come down) Will take 25 to 50 years to phase in Short driving range for current fuel cell cars No distribution system in place Excessive H2 leaks may deplete ozone

Micropower • Decentralized, dispersed small-scale power plants

Small modular units Fast factory production Fast installation (hours to days) Can add or remove modules as needed High energy efficiency (60–80%) Low or no CO2 emissions Low air pollution emissions Reliable Easy to repair Much less vulnerable to power outages Increase national security by dispersal of targets Useful anywhere Especially useful in rural areas in developing countries with no power Can use locally available renewable energy resources Easily financed (costs included in mortgage and commercial loan) Figure 18-33Page 406

Wind farm Bioenergy Power plants Figure 18-32Page 405 Small solar cell power plants Fuel cells Rooftop solar cell arrays Solar cell rooftop systems Transmission and distribution system Commercial Small wind turbine Residential Industrial Microturbines

ECONOMIC APPROACHES TO CHANGING ENERGY SOURCES Keep energy prices artificially low to encourage use of selected energy resources - Encourages energy waste - Rapid depletion of nonrenewable energy resources - Discourages development of other energy alternatives - Discourages improvements in energy efficiency

Renewable Energy