Energy: Renewable Energy

EVPP 111 Lecture

Dr. Kim Largen

• Renewable vs. non-renewable energy
• Renewable energy types
• Energy conservation

• Renewable vs. Non-Renewable Energy
• Renewable energy
• replenish themselves
• biomass
• continuously present
• solar
• geothermal
• tidal/oceanic
• collectively supply ~3% of world’s energy
• fossil fuels ~ 90%, nuclear ~ 7%

• Renewable energy types
• hydroelectric
• using flowing water to generate electricity
• today, used almost exclusively to generate electricity
• in past, used to directly power some machines
• grain mills
• saw mills
• machinery for textile industry
• three ways to produce hydroelectric power
• impoundment
• diversion
• pumped storage

• hydroelectric power potential
• distributed among continents in rough proportion to
• land area

• topography

• hydroelectric power
• supplies ~2.5% of world’s commercial energy
• % electricity generated by hydropower
• Norway, ~99%
• South America, ~73%
• developed world as whole, ~44%

• advantages
• high efficiency (80%)
• low-cost electricity
• long life spans for "plants"
• very clean
• no emissions of CO₂ or other greenhouse gases from operation
• may provide flood control below dam
• provides water for year-round irrigation in some areas

• disadvantages
• high environmental impacts
• floods natural areas
• converts terrestrial to aquatic habitats
• potential loss of species
• reduction in nutrient-rich silt deposition downstream
• emission of CO₂ and CH₄ from rotting vegetation trapped in reservoirs
• high construction costs
• danger of collapse
• decreases fish harvest below dam
• relocates communities
• causes loss of fertile agricultural land
• submerges cultural resources

• Three Gorges Dam
• across Yangtze River, China
• began in 1997, should be complete in 2009
• largest dam in world
• 1.3 miles wide, 610 feet tall
• cost ~$40 billion
• reasons for dam
• electricity
• transform upper Yangtze into more navigable, economic waterway
• provide flood control to middle and lower reaches of river (prone to frequent, disastrous floods)

• projected consequences of dam
• threaten migratory fish
• concentrate water pollution
• endanger to point of extinction: Chinese alligator, river dolphins, Siberian white crane, Chinese sturgeon
• inundate 153 towns, 4500 villages, necessitating relocation of people
• submerge archeological sites, scenic canyons

• tidal/oceanic
• employs same principle as hydroelectric plant
• problems
• obstruction of
• fish migration
• silt transport
• water flow
• concentration of pollutants
• facilities are rare
• Rance River Estuary, Brittany coast, France
• Nova Scotia. Canada

• geothermal
• earth’s core temps ~ 4,400 °C
• in some areas, molten material is close enough to surface to heat underground water and form steam
• used to generate electricity
• alternative energy source rather than true renewable energy source
• heat can be withdrawn faster than it can be replenished
• use
• US has ~50% of world’s geothermal electrical generating power
• California alone produces ~40% of world’s geothermal electricity
• Pacific Gas & Electric has one of world’s largest of geothermal generating facilities, north of San Francisco, serves ~2.9 million people
• Iceland
• ~all buildings of Reykjavik are heated with geothermal energy
• consequences
• steam contains hydrogen sulfide gas
• can contribute to air pollution
• produces unpleasant odor
• minerals in steam
• corrode pipes
• toxic to fish

• heat mining
• uses parallel wells
• water is pumped from surface, under pressure down one well
• "hot rocks" heat water as it percolates through rock fissures
• adjacent well recaptures hot water and returns it to surface
• steam from hot water generates electricity
• Hot Dry Rock Project, Los Alamos, NM
• temperature at well bottom is ~240°C (~430°F)
• research indicates sufficient useful heat in dry rocks beneath US to generate 6000 times the energy used in US in one year

• wind
• takes advantage of flowing air
• fastest-growing new source of electricity since 1998
• increasing ~30% per year
• some regions better suited to than others
• open areas better than wooded
• usually used in conjunction with other sources of electricity that can take over when wind doesn’t blow
• advantages
• high efficiency
• moderate capital cost
• low electricity cost
• very low environmental impact
• no CO₂ emissions
• quick construction
• easily expanded
• disadvantages
• blades make noise
• blades hazardous to birds
• visual pollution
• requires a lot of land
• needs steady winds, backup for when winds don’t blow

• solar
• sun provides continuous supply of energy that far exceeds world’s demands
• main problems
• intermittent in nature
• varies within day, across year, by location
• all systems that use solar energy must store energy or use alternative sources when sun is not available
• diffuse energy source
• utilized in three ways
• passive heating
• active heating
• solar-generated electricity
• passive heating
• sun’s energy is converted directly to heat energy when it is absorbed by a surface
• based on design, construction materials
• energy is "captured"and used on site
• no moving parts, system is maintenance free
• no energy is used to transfer heat within system
• no operating costs
• practical only in new construction
• design
• large window through which sunlight can enter in winter, not directly during summer
• large mass upon which sunlight impinges that collects and stores the heat
• heat re-radiating from storage mass warms air

• active heating
• sun’s energy is converted into heat, but transported elsewhere to be used
• requires
• solar collector
• pump
• system of pipes
• operation and maintenance costs
• solar collector transfers sun’s energy to liquid-filled tubes
• tubes carry warm liquid to area to be heated
• heat from liquid-filled tubes is transferred to area to be heated (or transferred to water that needs to be heated
• heat-depleted liquid in liquid-filled tubes is re-circulated to solar collectors
• solar-generated electricity
• process of converting solar energy directly into electrical energy by use of
• photovoltaic (PV) cell
• transparent wafer containing a semiconductor material
• sunlight energizes electrons, causing them to flow, creating electrical current
• produces only tiny amount of electricity
• many must be wired together in modular panels to produce significant amount of electricity
• photovoltaic (PV) cell uses
• solar calculators
• road signs
• radios
• roofs
• window, under development
• large arrays can power small communities

• biomass conversion
• biomass
• any accumulation of organic material produced by living organisms
• biomass conversion
• process of obtaining energy from chemical energy stored in biomass

• biomass can be
• burned directly as source of heat or for cooking
• burned to produce electricity
• converted to alcohol
• used to generate methane

• waste to energy
• use of municipal waste as source of energy
• requirements
• sorting waste
• securing sufficient quantity and steady supply
• concerns
• air pollution
• formation of toxic compounds such as dioxins

• Energy conservation
• important part of strategy for meeting energy needs
• ~84% of all commercial energy in US is wasted
• 41% wasted automatically
• 43% wasted unnecessarily
• using fuel-wasting vehicles, furnaces, devices
• living in leaky, poorly-insulated, poorly designed buildings
• three least energy-efficient devices in widespread use today
• incandescent light bulb
• wastes ~95% of energy input
• vehicles with internal combustion engines
• waste ~86-90% of energy in their fuel
• nuclear power plants producing electricity for space heating or water heating
• wastes ~86% of energy in their nuclear fuel (92% when energy associated with dealing with radioactive wastes is included)
• in homes/buildings
• insulate thoroughly
• eliminate leaks
• replace incandescent with fluorescent bulbs
• same amount of light for 25% of the energy
• use energy-efficient appliances
• use low-emissive glass
• reduce amount of heat entering building while allowing light to enter
• automatic timing devices for heating, lighting, air conditioning