Chapter 13 Renewable Energy and Conservation

Overview of Chapter 13 Direct Solar Energy Indirect Solar Energy Heating Buildings and Water Solar Thermal Electric Generation Photovoltaic Solar Cells Indirect Solar Energy Biomass Energy Wind Energy Hydropower Other Renewable Energy Sources Geothermal Energy Tidal Energy High and Low Technology Energy Solution Hydrogen and Fuel Cells Energy Efficiency

Direct Solar Energy Varies with latitude, season, time of day, and cloud cover Current technology…

Heating Buildings and Water Passive solar energy system of putting the sun’s energy to use without requiring mechanical devices to distribute the collected heat Certain design features can enhance passive solar energy’s heating potential South facing windows (in N. hemisphere) Well insulated buildings Attic vents Overhangs and solar sunspaces Why don’t more homes have passive solar energy technology?

Solar sunspace Utilizes passive solar energy to heat and cool homes Can be added to existing homes

Heating Buildings and Water Active Solar Energy System of collecting and absorbing the sun’s energy, and using pumps or fans distribute the collected heat Most common Series of collection devices on roofs or in fields Typically a black panel or plate Used to heat water

Heating Buildings and Water Solar Thermal Electric Generation Means of producing electricity in which the sun’s energy is concentrated by mirrors or lenses to either heat a fluid filled pipe or drive a Stirling engine Examples… More efficient than other solar technologies Benefits No air pollution No contribution to global warming or acid precipitation

Solar Thermal Electric Generation Solar thermal plant in CA – uses troughs to focus sunlight on fluid filled tube…

Photovoltaic Solar Cells Thin cells are treated with certain metals so that they generate electricity when they absorb solar energy Convert sunlight directly into energy Pros: No pollution, minimal maintenance Used on any scale Lighted road signs Entire buildings Cons: Not very efficient Requires a great deal of land

Photovoltaic Solar Cells Benefit to utility companies Rural areas in developing countries– it is more economical to use PV solar cells Future - can be incorporated into building materials Roofing shingles Tile Window glass

Cost of Electrical Power Plants Other technologies… Indirect Solar Energy Combustion of biomass Wind energy Hydropower

Indirect Solar Energy Biomass Can convert to biogas or liquids Plant materials used as fuel Ex: wood, crop wastes, sawdust, and animal wastes Contains energy from sun via photosynthesizing plants Renewable when used no faster than it can be produced Can convert to biogas or liquids Ethanol and methanol Pros and cons…

Advantages and Disadvantages of Biomass Reduces dependence on fossil fuels Often uses waste materials If trees are planted at same rate biomass is combusted, no net increase in atmospheric CO2 Disadvantages Requires land, water and energy Can lead to Deforestation Desertification Soil erosion

Indirect Solar Energy Wind Energy Electric or mechanical energy obtained from surface air currents caused by solar warming of air World’s fastest growing source of energy Wind results from sun warming the atmosphere Varies in direction and magnitude New wind turbines harness wind efficiently

Wind Energy Kills birds and bats Cost Public resistance Most profitable in rural areas with constant wind Few environmental problems Kills birds and bats No waste- clean source of energy Biggest constraints Cost Public resistance

Indirect Solar Energy Hydropower Form of renewable energy reliant on flowing or falling water to generate mechanical energy or electricity Sun’s energy drive hydrologic cycle Most efficient energy source (90%)

Hydropower Generates 19% of world’s energy Traditional hydropower Only suited for large dams New technology May be able to utilize low flow waterways Impacts of Dams Changes natural flow of rivers Disrupts migratory fish patterns Potential dam breaks

Three Gorges Dam 1990s China began work on the Three Gorges Dam (TGD), which will meet several goals: Designed to produce electricity equivalent to 18 nuclear power plants or large coal power plants  advantage because air pollution is a concern in China Agricultural productivity downstream will be optimized Will be used for transportation, commercial fishing and recreation Range of problems associated w/ building dams… China had difficulty finding investors – since uncertainty about design, construction and effectiveness was so great

Other Indirect Solar Energy Ocean waves Produced by winds Has potential to turn a turbine- and create electricity Ocean Temperature Gradients Use difference in temperature of surface and deep water to create electricity

Other Renewable Energy Sources Geothermal Energy Energy from the Earth’s interior for either space heating or generation of electricity Typically associated with volcanism From Hydrothermal Reservoirs (right) Created by volcanoes Reservoirs used directly for heat or to generate electricity Renewable? Environmentally benign?

Geothermal Energy From hot, dry rock Geothermal heat pumps Technology exists but is expensive Geothermal heat pumps Use difference in temperature between surface and subsurface Great for heating buildings Expensive installation

Other Renewable Energy Sources Tidal Energy Form of renewable energy that relies of the ebb and flow of the tides to generate electricity Typical difference between high and low tide is 1-2 ft but range can be higher Narrow bays may have greater variation Energy can be captured with A dam across the bay A turbine similar to a wind turbine

Energy Conservation vs. Energy Efficiency Human requirements for energy will continue to increase as the population increases and as developing countries raise their standards of living Energy conservation – using less energy by reducing energy use and waste, for example Example… Energy efficiency – using less energy to accomplish a given task, as for example with new technology Important environmental benefits from greater energy efficiency and conservation: Using energy efficient appliance could reduce CO2 emissions by millions of tons each year (slowing climate change) Reduce air pollution, acid precipitation and other environmental damage

Hydrogen as a Fuel Source H2 contains large amounts of available energy Gas at RT, liquid when cooled to -435 ˚F Explode when combined with the O2  releasing energy and forming water Advantages to Hydrogen as a fuel source Very high energy density Can be produced from any electrical source Electrolysis (see illustration on next slide) No greenhouse gases and few other pollutants Can be use in vehicles Disadvantages to Hydrogen as a fuel source Highly volatile (requires special storage) Relatively inefficient

Hydrogen as a Fuel Source- Electrolysis

Hydrogen Fuel Cell Fuel cell Device that directly converts chemical energy into electricity Requires hydrogen from a tank and oxygen from the air Similar to a battery, only the reactants are supplied from outside source

Applications of Fuel Cells Although technology is improving, not commonly available Vehicles Not yet commonly available Hydrogen is not yet readily available as a fuel source Batteries in cells phones or laptops

Energy Consumption Trends and Economics Lower energy intensity – implies economy is more energy efficient as it generates wealth Energy Trends in Developing Countries Per capita energy consumption is substantially less in developing countries than in industrialized countries

Energy Efficient Technologies Compact Fluorescent light bulbs Condensing furnaces Super-insulated buildings (right) Energy efficient appliances National Appliance Energy Conservation Act (NAECA) Automobiles Aircraft technology

Cogeneration Production of two useful forms of energy from the same fuel Cost effective on small or large scale…

Energy Savings in Commercial Buildings Energy services companies often offer their assistance so that businesses make little or no financial outlay How does this work?

Electric Power Companies and Efficiencies Traditionally to meet future power needs, electric utilities planned to build new power plants or purchase additional power from alternative sources Now they avoid these large expenses by demand-side management – help electricity consumers save money by reducing energy costs How? Improvements: US electric power plants are important target for improved energy efficiency – much heat is lost during generation of electricity Improve our electric grids – about 10% of electricity is lost during transmission right now  

Saving Energy at Home