Renewable Energy - Indirect Solar Energy - Nonsolar Energy

Indirect Solar Energy several sources of indirect solar energy biomass energy wind energy hydropower ocean waves ocean thermal energy conversion

#1: Biomass Energy consists of wood, fast-growing plants and algae, crop wastes, sawdust, wood chips, and animal wastes solid forms include: firewood charcoal  wood that has been turned into “coal” by partial burning animal dung peat  partly decayed plant matter found in bogs and swamps * ½ of the world’s population relies on biomass solids as their main source of energy *

Biogas a mixture of gases (mostly methane) that is produced by converting biomass (i.e. animal wastes) into gas can be stored and transported like natural gas “clean” fuel

Production of Biogas biogas digesters: use microbial decomposition of household and agricultural wastes to produce biogas for cooking and lighting several million in China and India

Conversion of Biomass to Liquid Fuels biomass can be converted to methanol and ethanol can be used in internal combustion engines gasoline + 10% ethanol = gasahol commercial conversion of agricultural and municipal wastes into ethanol costs are still high, but this may be able to compete with gas at some point what types of wastes are converted? major disadvantage?

Advantages of Biomass Use reduces dependence on fossil fuels often makes use of wastes reduces disposal problem produces low levels of sulfur and ash can offset CO2 production by planting new crops/trees

Disadvantages of Biomass Use requires land and water competes with food production  not sustainable if you don’t replant can result in soil erosion, deforestation and desertification, air pollution, and degradation of water supplies crop residues that are used actually prevent erosion by helping to hold the soil in place also, residue decomposition enriches the soil

#2: Wind Energy surface air currents are caused by the solar warming of air may be the world’s fastest growing source of energy radiant energy  mechanical energy highly dispersed turbines have become larger and more efficient currently, the most cost-competitive form of renewable energy

Where is Wind Energy Used? most profitable in rural areas that receive fairly continual winds e.g. islands, coastal areas, mountain passes, and grasslands the world’s largest concentration of turbines is in the Tehachapi Pass at the southern end of the Sierra Nevada Mountains in California

Pros and Cons of Wind Energy no major environmental problems clean source of energy  no SOx, CO2, or NOx cons birds sometimes collide with the turbines what are some preventative measures that can be taken? aesthetic concerns  turbines change the character of the landscape what can be done to deal with this?

#3: Hydropower energy harnessed as water flows from higher elevations to sea level pretty concentrated form of energy potential energy (water held back by a dam)  kinetic energy (water falls down a penstock where it turns turbines to generate electricity) currently the form of solar energy in greatest use

Impacts of Dams changes the natural flow of a river water backs up  floods large areas of land to form a reservoir destroys habitats disrupts migrations of spawning fish (e.g. salmon) below the dam, river flow is greatly reduced

Impacts of Dams continued reservoir-induced seismicity earthquakes can occur during and after the filling of a large reservoir area does NOT have to be seismically active to be affected serious water loss and increasing water salinity in arid areas prevent silt from enriching agricultural lands downstream e.g. Egypt now relies on chemical fertilizers to maintain fertility of the Nile River Valley/Delta

Impacts of Dams continued displace people in areas that are being flooded to make reservoirs e.g. Three Gorges Project of the Yangtze River in China largest dam ever displaced 2 million people flooded 1200 temples and other cultural sites

Impacts of Dams continued breaks in the dam harm people and properties downstream waterborne diseases can be a particular problem e.g. schistosomiasis (a tropical disease caused by a parasitic worm that can damage the liver, urinary tract, nervous system, and lungs) ½ the population of Egypt suffers from this disease (due to problems with the Aswan Dam on the Nile River)

Wild and Scenic Rivers Act prevents the hydroelectric development of certain rivers, although the number of rivers protected by this law is less than 1% of the nation’s total river systems

Why DO We Use Dams Then? Dams cost a lot to build, BUT they are relatively cheap to operate!

#4: Ocean Waves produced by winds  wave energy a hollow chamber is sunk into a gully off the coast to catch waves rising water in the chamber pushes air into a vent that contains a turbine, causing the turbine to spin when the water recedes, it draws the air back into the chamber  moving air continues to drive the turbine need to be able to harness energy at a rate that is efficient and productive

#5: Ocean Thermal Energy Conversion (OTEC) the generation of electricity from ocean temperature gradients (the differences in temperature at various ocean depths [~24 °C]) gradients are the result of solar energy warming the surface of the ocean

Electricity Generation Using OTEC warm surface water is pumped into a power plant where it heats a liquid, such as ammonia, to the boiling point ammonia steam drives the turbine ammonia is cooled by the very cold water from the deep ocean cold water can be used to air condition building, or used in aquaculture facilities

Disadvantages of OTEC must pump A LOT of water to generate power requires a lot of energy not very efficient (~3-4%) costs are high

Other Sources of Renewable Energy other renewable energy sources (not necessarily dependent on the sun) include: tidal energy (although this is somewhat dependent on the gravitational pull of the sun) geothermal energy

Tidal Energy caused by changes in water level between high and low tides what are the tides? the alternate rising and falling of the surface waters of the ocean and seas that generally occur twice each day the result of the gravitational pull of the moon and the sun can harness tidal energy by building a dam across a bay

Disadvantages of Tidal Energy few locations have large enough differences in water level between high/low tides to make power generation feasible costs a lot affects organisms that use bays and estuaries as habitat

Geothermal Energy the naturally occurring heat within the Earth amount of energy is enormous

Geothermal Energy is Associated with Volcanism hydrothermal reservoir: as groundwater travels downward and is heated, it becomes buoyant and rises until it is trapped by an impermeable layer in the Earth’s crust hot water + steam can escape to the surface  hot springs and geysers tapped by drilling wells similar to those used for extracting oil and natural gas can be used directly for heating or to generate electricity electricity is inexpensive and reliable requires a very small area of land (relative to other energy sources)

Where is Geothermal Energy Used? the U.S. is the world’s largest producer of geothermal energy largest plant is The Geysers in northern California Iceland  only uses hydro- and geothermal power used to generate electricity and heat 2/3 of the homes most produce is grown in geothermally heated greenhouses water used to transfer heat can be recirculated into the reservoir

Environmental Problems with Geothermal Energy the most common environmental hazard is the emission of H2S some of the surrounding land may subside (sink)

Geothermal Energy From Hot, Dry Rock conventional use relies on groundwater limited geographically can fracture hot, dry rock and circulate water into the area to make an artificial underground reservoir very expensive

Geothermal Heat Pumps (GHPs) use the difference in temperature between the Earth’s surface and subsurface at depths from 1 m to about 100 m installation can be expensive, but operating costs are low VERY efficient (best heating systems available)