Environment in the News
nayo0f033
chapter_18.pptRenewable Energy Resources
Chapter 18
Reducing Heat Loss
- Two strategies to decrease reliance on fossil fuels
- Alternative energy sources
- Reducing energy sources
- Thermal images show heat escaping from a building
- Dark blue and green represent cold
- Reds and yellows represent heat
- Allow homeowners to detect where heat is escaping their home and insulate, caulk, replace old windows
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Reducing Heat Loss
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Direct Solar Energy
- Learning Objectives:
Distinguish between active and passive solar heating ad describe how each is used
Contrast the advantages and disadvantages of solar photovoltaic cells and solar thermal electric generation in converting solar energy into electricity
Explain how fuel cells work
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Energy Consumption
- Direct Solar Energy
- Small portion of sun’s energy reaches Earth’s surface
- Always available, not like fossil and nuclear fuels
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Energy Consumption
- Heating Buildings and Water
- Active Solar Heating
- Collectors absorb solar energy and pumps and fans distribute the collected heat
- Primarily used for heating water
- Household use
- Swimming pools
- Can provide a family with hot water year-round
- More than 8% of energy consumed in the US goes toward heating water
- Not used as much for space heating, but may become more important as oil, gas, electricity prices rise
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Energy Consumption
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Energy Consumption
- Passive Solar Heating
- Does not require mechanical devices to distribute the collected heat
- Design features are used to warm buildings in the winter and keep them cool in the summer
- South facing windows receive more sunlight
- Sunlight provides heat, stored in floors and walls
- Heat is transmitted by convection
- Must be well-insulated to maintain heat
- Passive heating can save as much of 50% of heating costs
- About 7% of new homes built have passive heating
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Energy Consumption
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Energy Consumption
- Photovoltaic Solar Cells
- A wafer or thin film of solid-state materials, such as silicon or gallium arsenide, that is treated with certain metals in such a way that the film generates electricity when solar energy is absorbed
- No pollution, minimal maintenance
- Absorbs sunlight even on cloudy or rainy days
- Currently limited by low efficiency, would require too much land to generate sufficient electricity
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What a Scientist Sees
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Energy Consumption
- Cost of manufacturing PV modules has steadily decreased over the past 35 years
- $90/watt in 1975 to $4/watt in 2010
- Cost of producing electricity has also declined
- $0.15–0.25/kwh
- In developing countries and rural areas PVs are cheaper than extending power lines
- A solar panel the size of 2 pizza boxes is enough to power
5 lights, 1 radio, 1 television
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Energy Consumption
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Energy Consumption
- Thin-Film solar cells are much cheaper to manufacture than standard PVs
- 120,000 Japanese homes have installed solar roofs in the past few years
- Million Solar Roofs Initiative
- Solar panels on 1 million buildings by 2016
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Energy Consumption
- Dye-sensitized solar cells are being developed, and can be produced at 1/5 the cost of conventional solar cells
- Operating PVs creates no air or water pollution, but manufacturing requires toxic industrial chemicals
- Cleaner technologies need to be developed
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Energy Consumption
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Energy Consumption
- Solar thermal Generation
- Means of producing electricity in which the sun’s energy is concentrated using mirrors or lenses onto a fluid-filled pipe; the heated fluid is used to generate electricity
- Computer-guided mirrors track the sun for optimum efficiency, heat oil within pipes to 735F, hot oil is used to boil water into super-heated steam, which is then used to generate electricity
- More efficient than other solar technologies
- Becoming cost-competitive with fossil fuels
- No pollution, acid deposition, or climate change
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Energy Consumption
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Energy Consumption
- Solar-Generated Hydrogen
- Hydrogen: fuel of the future
- Abundant, easily produced
- Electricity form any source can split water into oxygen and hydrogen gases
- Environmental impact depends on the source of electricity used
- Hydrogen itself is a clean fuel
- Produces water and heat as byproducts
- Potential to provide energy for transportation, heating buildings, producing electricity
- Solar electricity must be used immediately, whereas hydrogen can be stored and transported by pipeline
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Energy Consumption
- Hydrogen production from PVs electricity currently has low efficiency high cost
- Replacing H as transportation fuel has other costs as well:
- Complex infrastructure is needed to provide H to service stations
- H is very flammable
- Fuel cells must be developed for motor vehicles
- Similar to batteries, but instead of storing energy, they can produce energy as long as they are supplied with fuel
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Energy Consumption
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Global Climate Change
What is active solar energy?
What are the advantages of producing electricity by solar thermal energy? Using hydrogen and photovoltaic (PV) solar cells?
How do fuel cells work?
Indirect Solar Energy
- Learning Objectives
Define biomass and outline its use as a source of energy
Compare the potential of wind energy and hydropower
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Indirect Solar Energy
- Some renewable energies use the sun’s energy indirectly
- Combustion of biomass (organic matter) is an example
- Plants use solar energy for photosynthesis and store the energy as biomass
- Wind energy
- Uses wind to generate electricity
- Hydropower
- Uses dammed rivers and streams to generate electricity
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Indirect Solar Energy
- Biomass Energy
- Plant and animal material used as fuel
- Renewable if used properly
- May be solid, liquid, or gas
- Crop wastes, sawdust, wood, charcoal, peat, animal dung
- At least half of the world’s population relies on biomass fuel
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Indirect Solar Energy
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Indirect Solar Energy
- Biogas
- Biomass can be converted into a mixture of gases
- Mostly methane
- Biogas digesters produce gas for cooking and lighting, by microbial decomposition of wastes
- Solid remains can be used as fertilizer
- Biogas has the potential to power fuel cells to generate electricity
- Boston pilot poject - 1997
- Provides electricity for 150 homes from sewage sludge
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Indirect Solar Energy
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Indirect Solar Energy
- Biomass can also be converted into liquid fuels
- Methanol
- Ethanol - Can replace gasoline in internal combustion engines
- Biodiesel - made from plant or animal oils
- Biomass is attractive to politicians and consumers as source of energy
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Indirect Solar Energy
- Problems of Biomass
- Use of land and water that might be dedicated to food production
- Higher food prices
- Reduces food supplies
- Unsustainable use of wood
- Trees are cut faster than replanted
- Severe damage to environment
- Harm to Soil Quality
- Crop residues are not left for conservation tillage, reduce erosion
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Indirect Solar Energy
- Wind Energy
- Electric energy obtained form surface air currents caused by solar warming of air
- Wind turbines are huge, and becoming more efficient
- $0.40/kwh in 1980 to $0.04–0.07/kwh now
- Cost competitive with most conventional energy
- Most profitable in areas with consistent winds
- Coastal areas, mountain passes, islands, grasslands
- Tehachapi pass, CA has highest concentration of wind turbines
- US, Germany, Denmark are main wind electricity producers
- Denmark produces 21% of its energy by wind
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Environmental InSight
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Environmental InSight
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Indirect Solar Energy
- Best Locations for Wind Energy in US
- ND, TX, SD, MT,NE, WY, OK, MN, IO, KS
- If we developed wind energy in ND, TX, and KS, we could supply enough electricity to meet the current needs of the entire US
- Projects are underway
- Currently, wind power is captured and placed in regional electricity grids
- Requires development of distribution methods
- No waste, clean energy
- Every kwh od wind electricity reduces release of 2.2lb of CO2 from fossil fuels into the air
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Indirect Solar Energy
- Problems with Wind Turbines
- Can cause bird kills if turbines are on bird migration pathways (Altamont Pass, CA)
- Can be corrected by not placing turbines on those sites, painting blades, using anti-perching devices, and shutting down during peak migration periods
- Developers currently conduct voluntary wildlife studies to locate sites away form bird and bat routes
- Aesthetic Issues
- Maple Ridge Wind Farm, in Upstate NY
- Some residents welcome extra money form wind leases
- Others complain that turbines ruin their view of Adirondacks
- Nantucket Sound residents oppose off-shore wind project in MA, because tourists may find it offensive
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Indirect Solar Energy
- Hydropower
- A form of renewable energy that relies on flowing or falling water to generate electricity
- Sun drives hydrologic cycle
- Potential energy of water held back by a dam can be converted into electricity
- More efficient than any other source of energy
- 90% of potential energy is converted to electricity
- Generates about 19% of world’s electricity
- 7% in US
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Indirect Solar Energy
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Indirect Solar Energy
- Problems with Hydropower
- Dams change natural flow of rivers
- Water backs up, floods large areas of land to form reservoir, destroys plant and animal habitats
- Natural beauty of countryside is affected
- Earthquakes may occur and damage dams in areas of seismic activity
- In some areas, there is greater evaporation of water
- Displaces people when reservoir is created
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Global Climate Change
What is biomass and how is it used?
What are the advantages and disadvantages of using wind to produce electricity? Of using hydropower to produce electricity?
Other Renewable Resources
- Learning Objectives:
Describe geothermal energy and tidal energy
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Other Renewable Resources
- Geothermal Energy
- Energy form the Earth’s interior, used for space heating or generation of electricity
- Just 1% of the heat containe din the uppermost layer of the Earth’s crust is 500X the energy contained in all of Earth’s oil and natural gas resources
- Volcanic activity heats groundwater forming a hydrothermal reservoir
- Contains hot water, possibly steam hot springs
- Drilling a well can bring up hot water/steam and used to generate electricity, or to supply heat directly to consumers
- Inexpensive and reliable
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Other Renewable Resources
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Other Renewable Resources
- US is largest producer of geothermal electricity
- The Geysers geothermal power plant, in CA provides electricity to 1.7 million consumers
- Iceland is a volcanic island
- Generates electricity
- Heats 2/3 of homes directly with geothermal energy
- Fruits and vegetables are grown in geothermally heated greenhouses
- Geothermal energy is renewable on a human timescale
- Water used to transfer energy is not inexhaustible
- Considered environmentally benign
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Other Renewable Resources
- Heating and Cooling Buildings with Geothermal Energy
- Geothermal heat pumps (GHPs) take advantage of the difference in temperature between Earth’s surface and subsurface
- Underground arrangement of pipes, circulating liquids, extract natural heat in winter, transfers excess heat underground in summer
- Heating systems can be modified to provide supplemental hot water
- Installation is expensive, but operation costs are low
- Green architecture popularity and increasing fuel costs are making GHPs more popular
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Other Renewable Resources
- Tidal Energy
- Tides are caused by the gravitational pull of the moon and sun
- A dam across a bay can harness the energy of large tides to generate electricity
- Water at high tide gets trapped on land side, as tide recedes, the water falls through the dam’s spillway and turns a turbine
- France, Russia, China, Canada have tidal power plants
- Problems
- Few places in the world have tides large enough to support this mode of energy
- High economic cost
- Potentially high environmental costs in estuaries
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Global Climate Change
What are the pros and cons of using geothermal energy to produce electricity and what are the pros and cons of using tidal power to produce electricity?
Energy Solutions:
Conservation and Efficiency
- Learning Objectives:
Distinguish between energy conservation and energy efficiency and give examples of each
Summarize options to conserve energy at home
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Energy Solutions:
Conservation and Efficiency
- Energy Conservation:
- Using less energy by reducing energy use and waste, for example
- Energy Efficiency:
- Using less energy to accomplish a given task, by using new technology, for example
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Energy Solutions:
Conservation and Efficiency
- Consumption trends and Economics
- Even though US has become more energy efficient, consumption has increased
- Per capita consumption in developing nations is substantially less than in developed nations
- But greatest increase in consumption is increasing in developing countries - China and India
- Increase in economic development and population
- Use of older, less expensive, less efficient technology
- Need to balance economic development with environmental degradation
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Energy Solutions:
Conservation and Efficiency
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Energy Solutions:
Conservation and Efficiency
- Energy-Efficient Technologies
- Appliances, automobiles, buildings, industrial processes
- CFLs produce light comparable to that of incandescent lightbulbs, but require only 25% of energy and last up to 15% longer
- Condensing furnaces require 30% less fuel
- Superinsulated buildings use 70–90% less energy
- Refrigerators today consume 75% less energy than in mid 1970s
- Automobile efficiency has improved dramatically since 1970s - Lighter materials and drag-reducing design
- Efficiency doubled between mid 70s and mid 80s
- Declined after that as larger vehicles became popular
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Energy Solutions:
Conservation and Efficiency
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Energy Solutions:
Conservation and Efficiency
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Energy Solutions:
Conservation and Efficiency
- Cogeneration/Combined Heat and Power
- Energy technology that involves recycling ‘waste’ heat
- Production of two forms of energy form same fuel
- Fuel combustion generates electricity and steam
- Steam is used to heat buildings and water, in industrial processes or to produce additional electricity instead of being wasted
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Energy Solutions:
Conservation and Efficiency
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EnviroDiscovery
- Netting the Benefits of Home Energy Production
- Home solar systems are expensive to install and owners have often paid a large economic price for environmental awareness
- Utility companies are now permitting homeowners who produce own energy to ‘net meter’ their electricity
- Excess energy is supplied to the utility - meters run back
- When homeowner’s consume more energy than they produce, meter runs forward
- This increase affordability of solar systems
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EnviroDiscovery
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Energy Solutions:
Conservation and Efficiency
- Electric Companies and Energy Efficiency
- Changes in regulations allow utilities to make more money by generating less electricity
- Provides incentives for conservation
- Reduce emissions that contribute to environmental problems
- Utilities make money if they help consumers save energy-don’t have to build new power plants
- Cash awards, free CFLs, air conditioners, other appliances
- Utilities themselves need to be more energy efficient
- Use cogeneration
- Improve power grids, reduce transmission loss
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Energy Solutions:
Conservation and Efficiency
- Energy Conservation at Home
- Average household spends several thousand dollars/yr on utility bills
- Cost could be reduced by having energy efficient home
- Costs more upfront, but improvements pay for themselves in 2–3 yrs
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Energy Solutions:
Conservation and Efficiency
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Case Study
- Green Architecture
- Hearst Tower, Manhattan, NY
- 26% higher efficiency than standard office buildings
- Earned first Gold LEED certification from US Green Building Council
- Diagrid design floods interior with natural light and uses 2000 tons less steel (90% of steel used is recycled)
- Efficent cooling and heating systems
- 10 story “Icefall” cools the atrium and irrigate plants
- Water comes from collected rainwater
- Low-vapor paints, low toxicity sealants, low toxicity carpets and sustainable materials
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Case Study
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Global Climate Change
What is the difference between energy conservation and energy efficiency?
How can you conserve energy at home?
