Costs of generating electricity ( $US quoted ) Coal (Avg of 27 plants) $1K-$1.5K/kWe capital –$45-60/MW.h (Inv. 50%, O&M 15%, Fuel 35%) Gas (23) $ K/kWe –$40-63/MWh (Inv. 20%, O&M 7%, Fuel 73%) Nuclear (13) $1-$2K/kWe –$30-50/MWh (Inv. 70%, O&M 13%, Fuel 10%) Wind (19) $1-2K/kWe –$45-140/MWh (O&M 12-40%) –Load factor variability is a major factor in setting the costs of running a wind plant Solar (6) approaches $300/MWh Cogeneration (24) estimated $30-70/MWh

Types of Windmills/turbines According to wikipedia, as of 2006 installed world-wide capacity is 74 GW (same capacity as only 3.5 dams the size of the three-Gorges project in China). Altogether, there are 150,000 windmills operating in the US alone (mainly for water extraction/distribution) 7% efficiency, but work at low wind speeds Up to 56 % efficiency with 3 blades, do very little at low wind speeds

Wind Energy An extensive site for Wind Information!! According the article from the IEA (previous slide), the typical availability of a wind farm is 17-38% for land- based plants and 40-45% for off- shore plants.

Worldwide Wind Capacity

US Wind Distribution

Types of Windmills (cont.)

Altamont Pass (CA) turbines, built 1980’s

San Gorgonio Pass (CA) turbines, built 1980’s

Basics of a Wind Turbine

GE 2.5MW generator Blade diameter: 100m Wind range: 3.5m/s to 25m/s Rated wind speed: 11.5 m/s

GE 3.5 MW Blade diameter: 111m Wind range: 3.5m/s to 27 m/s Rated wind speed: 14 m/s Specifically designed for off-shore deployment

Web site for movie on wind turbine construction

Wind Turbines

Water wheels through the ages

ITAIPU (Brazil/Paraguay)

ITAIPU (Brazil/Paraguay)

Essentials of PV design

Basics of Photo-Voltaics A useful link demonstrating the design of a basic solar cell may be found at: There are several different types of solar cells: –Single crystal Si (NASA): most efficient (up to 30%) and most expensive (have been $100’s/W, now much lower) –Amorphous Si: not so efficient (5-10% or so) degrade with use (but improvements have been made), cheap ($2.5/W) –Recycled/polycrystalline Si (may be important in the future)

Engineering work-around # 2: Martin Green’s record cell. The grid deflects light into a light trapping structure

Power characteristics (Si) cm 2 silicon Cell under different Illumination conidtions Material Level of efficiency in % Lab Level of efficiency in % Production Monocrystalline Silicon approx to17 Polycrystalline Silicon approx to15 Amorphous Silicon approx. 135 to7

Solar Cell Costs Costs have dropeed from about $5.89/pk Watt output in 1992 to $2.73/pW in 2005

Solar House This house in Oxford produces more electricity than it uses (but only about 4kWh/yr!! According to the NREL, hardly worth selling)

Advanced designs-multilayers

Typical products 15W systems for $150 Flood light system for $390 (LED’s plus xtal. cells) Battery charges (flexible Amorphous cells)

Example of a retrofit

Dick SwansonMartin Green

Fuel Cells- sample schematics For more details on these and other types, see also:

Ballard Power Systems (PEM) 85kW basic module power (scalable from 10 to 300kW They say) for passenger cars. 212 lb (97 kg) 284 V 300 A Volume 75 liters Operates at 80 o C H2 as the fuel (needs a reformer to make use of Methanol etc.) 300kW used for buses

Fuel Cell Energy (“Direct Fuel Cell”) Appears to be a molten carbonate systme based on their description Standard line includes units of 0.3,1.5 and 3 MW Fuel is CH 4 (no need for external reformer) can also use “coal gas”, biogas and methanol Marketed for high-quality power applications (fixed location) This is a nominal 300kW unit (typically delivers 250kW according to their press releases). Most of the units installed to date are of this size.

The Hydrogen Hype Can’t mine it, it is NOT an energy source –Why not just use electricity directly? Even as a liquid, energy density is low –Storage and transport are difficult issues More dangerous (explosive) than CH 4 No existing infrastructure The Realities H 2 burns with 0 2 to make water H 2 comes from the oceans (lots of it) Fuel cells can “burn” it efficiently

Hydrogen Economy Need lots of research in areas such as: –Production –Transmission/storage –Distribution/end use Hydrogen seems to be an attractive alternative to fossil fuels, but it cannot be mined. You need to treat it more like electricity than gasoline (i.e. as a carrier of energy, not as a primary source).

Storage Possabilities Physisorbtion Chemical Reaction Chemisorbtion Encapsulation Weak binding energy -> Low T required Carbon nanotubes Porous materials Zeolites Reversible Hydrides PdH, LiH, … Large energy input to release H2 Slow Dynamics Very large energy input to release H2 Not technologically feasible H2 trapped in cages or pores Variation of physical properties (T or P) to trap/release H 2 4 H molecules in cage Al H

DOE report from 2004 is available at: MIT web site on photo-production: Nature and Physics Today articles: Nature Vol. 414, p (2001)Physics Today, vol 57(12) p39-44 (2004)

Three Gorges Dam (China)