Renewable Energy Sources
• SUN! • What is the distribution of fuel use in the world?
– Petroleum 34% – Coal 25% – Natural gas 21% – Renewables 14% – Nuclear 6%
How can we use energy from the sun directly?
• Solar Heat
– Passive designs – Active designs
• Solar Thermal Electricity
– Trough collection – Tower collection – Dish collection
• Photovoltaic Electricity
– Using the photoelectric effect explained by Einstein
• Passive Design
– Maximizes the capture of direct solar energy
• Direct gain (the simplest system) stores and slowly releases heat energy collected from the sun shining directly into the building and warming materials such as tile or concrete. Care must be taken to avoid overheating the space. • Indirect gain (similar to direct gain) uses materials that hold, store, and release heat; the material is located between the sun and living space (typically the wall). • Isolated gain collects solar energy remote from the location of the primary living area. For example, a sunroom attached to a house collects warmer air that flows naturally to the rest of the house.
– According to US-DOE Buildings with passive heating design require ~1/2 heating requirements of conventional new buildings.
• Active Design
– Called active because a source of energy other than solar is required to drive the system. – Solar hot water heat – Radiative building heat
Nearly 300 homes in this San Diego development have solar water heating systems, and some have solar electric systems. The solar water heating collectors on the roof look like skylights.
Solar Heating – Active design
Flat-plate collectors are used for residential water heating and hydronic space-heating installations.
Consult Fig. 4.2 from text
Energy Star Residential Water Heaters Available January 1, 2009
Solar Thermal Electricity
Generating electricity from sunlight - Advantages *10,000 mi2 of Nevada desert could supply the TOTAL electricity needs of the US using flat-plate solar collectors (at 10% efficiency)! *It can complement existing systems and is becoming more attractive for peak power additions
*It’s very costly *Sunlight is an intermittent source
*However, as costs diminish & price of fossil fuels increase, solar electricity will become very competitive
Solar Thermal Electricity (Fig. 4.3) Trough system
•Oil in pipe is heated to 400°C •Heat is used to generate electricity in conventional generator.
This solar thermal power plant located in the Mojave Desert in Kramer Junction, California, is one of nine such plants built in the 1980s. During operation, oil in the receiver tubes collects the concentrated solar energy as heat and is pumped to a power block (in background) for generating electricity. For a picture of how this works see: http://www1.eere.energy.gov/solar/review _meeting/pdfs/prm2008_cohen_acciona.p df
Solar Thermal Electricity (Fig. 4.3) Power Tower
•Uses molten salt at 565°C
•Heat is used to generate electricity in conventional generator.
•Can operate 65% of year without backup
This 1996 photo shows the solar tower and surrounding field of mirrors for Solar Two, a demonstration project located near Barstow, California.
Solar Thermal Electricity (Fig. 4.3) Dish
•Energy is directed to focal point •Powers an engine generator directly at 800°C •Good for remote power needs
This solar dish-engine system is an electric generator that "burns" sunlight instead of gas or coal to produce electricity. The dish, a concentrator, is the primary solar component of the system, collecting the energy coming directly from the sun and concentrating it on a small area. A thermal receiver absorbs the concentrated beam of solar energy, converts it to heat, and transfers the heat to the engine/generator. (Credit: Sandia National Laboratories)
• Sunlight can also be transformed directly into electricity via the photovoltaic effect.
– When light is absorbed by certain materials, electrons get excited and move.
*Simple and versatile *Portable (road signs) *Can be much less expensive than grid extensions
*It’s still more expensive than conventional power (3 times)
• Semiconductors – a look at bonding
– Metals (conductors) – Nonmetals (insulators) – Semimetals (semiconductors)
• Photocell Design
– How do we get the electrons to move?
n-layer is doped with As
p-layer is doped with Ga
This results in an electric potential – the cell acts like a battery
Hydroelectricity Uses running water to turn a turbine and generate electricity. Provides about 20% of world’s electricity needs. Advantages:
* No CO2 or other emissions
* Small facilities can utilize riverflow directly * Large facilities require a dam (which can be beneficial)
Disadvantages: * Riverflow is variable
* Dams can be harmful to environment * Future development is very limited
Beauharnois Dam The Beauharnois Dam on the St Lawrence Seaway harnesses some of the river's enormous electric potential (photo by J.A. Kraulis). Produces 1658 MW.
Wind Power The technology has been around for 2000 years to harness the power of the wind.
Fastest-Growing Energy Source Taking Off Worldwide
U.S. and World Wind Energy Capacity
25000 20000 Installed 15000 Capacity (MW) 10000 5000 0 U.S.
Wind Leaders: 1. Germany (2.3%) 2. United States(.2%) 3. Spain (2.4%) 4. Denmark (13%) 5. India (0.6%)
Based on information supplied by International Energy Agency and the American Wind Energy Association.
World Total (at the end of 2001)
Cost of Wind Energy
12 COE (¢/kWh [constant 2000 $]) 10 8
Low wind speed sites
High wind speed sites
Bulk Power Competitive Price Band
4 2 0 1990
An All American Resource
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17
North Dakota Texas Kansas South Dakota Montana Nebraska Wyoming Oklahoma Minnesota Iowa Colorado New Mexico Idaho Michigan New York Illinois California
World Class Wind Potential
Germany’s Potential: 100 GW North Dakota’s Potential: 250 GW
Slide Courtesy of the American Wind Energy Association.
The Community Energy Wind Farms
The 15-MW Mill Run Wind Farm Fayette County, PA On-Line October 2001
The 9-MW Somerset Wind Farm Visible From the PA Turnpike On-Line October 2001
The 31-MW Fenner Wind Farm Madison County, NY On-Line June 2002
The 66-MW Mountaineer Project Allegheny Plateau, WV On-Line December 2002
The 61-MW Pocono Wind Farm Northeast of Scranton, PA Expected On-Line Fall 2003
The 7.5-MW Jersey Atlantic Project Atlantic City, NJ Expected On-Line Spring 2004
Who uses wind?
O rga n iza tion U n iv ersity of P en n sylvan ia P enn S tate U n iv ersity U n iv ersity of B u ffalo C arn eg ie M ello n U n iv. C ath o lic U n iv ersity D rex el U n iversity G ian t E ag le S up erm ark ets A m erican U n iv ersity P ercen t W in d 11% 5% 2% 6% 1 1.7 % 9 .5 % 3% 5% k W h / y ea r 4 0,000 ,0 00 1 7,600 ,0 00 8,000 ,0 00 5,80 5 ,0 00 4,000 ,0 00 4,000 ,0 00 3,000 ,0 00 2,170 ,0 00 # o f T u rb in es 10 4 .4 2 .0 1 .5 1 .0 1 .0 .75 .55
Wind Power’s Low Environmental Impact Rating
-- Power Scorecard
*Tidal Energy – in the research stages *Using Temperature Gradients In Hawaii – Ocean Thermal Energy Conversion (OTEC) integrated power, air conditioning, water and farming activities
EPRI Ocean Energy Program
Using the earth’s molten core (hot springs, volcanos)
Currently supplies 0.3% of world’s electricity (high T - 150°C) Can also be used for space heating, industrial process steam, greenhousese, and aquaculture (medium T – 90 - 150°C) Low T (<90°C) can be coupled with heat pumps for home heating and cooling.
The first modern geothermal power plants were also built in Lardello, Italy. They were destroyed in World War II and rebuilt. Today after 90 years, the Lardello field is still producing.