Chapter 16 Energy efficiency and renewable energy
Energy efficiency Measure of how much work we can get from each unit of energy we use Improving in US but far behind Europe and Japan 43% is unnecessarily wasted Costing US $570,000 per MINUTE!
Four widely used big energy wasters Incandescent light bulbs use only 5-10% Internal combustion engines uses 20% Nuclear power plants wastes 75% Coal fired power plants wastes 66%
How can we cut energy waste?
Industry and Utilities Cogeneration: using a combined heat and power system (CHP); steam and electricity produced from same fuel source are used for 2 different things: generate electricity and to heat bldgs rather than being released into environment 70-90% energy efficient Denmark #1 - gets 82% of electricity from CHP systems US only 8%
Replace energy wasting electric motors with variable speed motors - motor operates at full speed no matter what the output is Use recycled metals and steel - producing steel from recycled materials uses 75% less energy and emits 40% less CO2 Switch from incandescent to fluorescent or LED lighting (light emitting diode) Utilities commission should reward utilities for cutting bills to save energy instead of rewarding them for selling more electricity
Smart grid: digitally controlled respond to changes in supply and demand Involves a 2 way flow of energy and info Also shows consumer what they're using per minute Upfront costs to build this $200-500 billion but would pay for itself in a few years; saves $100 billion per year
Save in Transportation
CAFE: corporate average fuel economy 1973-85: avg fuel efficiency increased Since 1985 it's been decreasing 21 mpg No increase in standards and increasing popularity of SUVs and trucks
2008 law to 35 mpg by 2016 Hidden costs in gasoline: subsidies, tax breaks for oil co., car manufacturers, road builders, cost of pollution, cost of military protection of oil supplies in Middle East ~$12 / gallon Tax breaks for consumers who buy efficient cars. $ comes from tax paid by people who buy inefficient cars Increase bike use lanes, incentives
Plug in hybrid- 2nd and more powerful battery runs primarily on electricity Challenge is making a powerful and affordable battery; LED is promising but high heat, expensive Improve car efficiency Fuel cell - 2x efficiency of internal combustion engine, little maintenance, use H gas, no emissions New diesel - energy efficient- 45% of new car, low emissions, quiet, can use biodiesel Build cars out of lighter materials
Increasing energy efficiency in buildings Face sun Increase insulation Use natural lighting Solar heating Solar water heating Recycle waste water Living roofs
LEED: Leadership in Energy & Environmental Design
1st step in improving energy efficiency is an energy survey Thermography
Improving existing buildings Increase insulation Use energy efficient windows Fix leaks Light colored roofs Roofs that change colors winter vs. summer Roof mounted solar hot water heater Tankless hot water heater as flows thru heats water Energy efficient appliances Lighting
Solar Energy
Residential Passive solar heating system absorbs and stores heat from sun using stone, concrete walls and floors, heavy insulation, white roof Active solar heating system captures energy from sun by pumping fluid thru collectors mounted on roof that faces sun; some heat is used some is stored
Advantages net energy is moderate (active) to high (passive) Low emissions Low land disturbance Moderate cost (passive) Disadvantages Need access to sun 60% of the time Sun can be blocked High install and maintenance costs Need backup system for cloudy days
World's fastest growing way of producing electricity Use photovoltaic cells - Si other trace metals that conduct electricity; connect to an existing grid or batteries to store it Solar Power Plants
Advantages Disadvantages Low net energy only 3% Moderate environmental impact No emissions Lower cost with natural gas backup High cost Need backup system for cloudy days High water use for cooling to condense steam back to water for reuse and washing panels and usually in areas where water is scarce
Hydropower Uses kinetic energy of flowing and falling water Leading renewable energy source Build dam, created reservoir, some allowed to flow thru which spins turbines Worlds largest dams are large methane producers
Other forms of hydropower Small scale uses suitcase size floating turbines Using tides and waves- esp in estuaries
Saudi Arabia of wind power: N. And S. Dakota, Kansas, Texas could supply electricity needs of lower 48 Denmark gets 20% from wind aiming for 50% Wind Energy
Wind energy Advantages Disadvantages Moderate to high energy yield No emissions Widely available Low cost -cheapest way to produce electricity Visual pollution Need backup system Low level noise pollution Threat to birds?? Easy to build
Biomass
Advantages Widely available Moderate cost No increase in CO2 if harvested, burned, replanted sustainably Plantations can help restore degraded land Lower cost with natural gas backup Disadvantages Moderate to high environmental impact CO2 emissions if not harvested and burned sustainably Clear cutting: soil erosion, water pollution, loss of habitat, increased CO2 Use of fertilizer Often burned in stoves or open fires - pollution, inefficient
Reduced from veg oil Biodiesel ethanol produced from plants and plant waste Used in place of petroleum based diesel fuel US biggest producer of ethanol from corn Brazil is biggest from sugar cane EU is biggest from veg oil
biofuel over gasoline Advantages Disadvantages Crops can be grown anywhere No net CO2 if crops aren't used faster than they're replenished Available now Easy to store, transport Can be used in cars at little or no additional cost Increased NO emissions Low net energy yield for soybeans Decreased biodiversity Lower gas mileage e.g. E85 has 30% Lower gas mileage
Cellulosic Ethanol MSW municipal solid waste
Cellulosic Ethanol
Geothermal Heat stored in soil, underground rocks and fluids in earth's mantle Capture heat using geothermal heat pump If designed well, most energy efficient, reliable, environmentally clean, cost effective way to heat/cool,a space
Advantages Disadvantages Moderate net energy & high efficiency at some sites Can be low efficiency at some sites Scarcity of suitable sites No emissions Noise Low cost Some CO2 emissions Moderate cost (passive) Need backup system for cloudy days