GREEN POWER

EET 3700

Presented by: Dan Ehlke

OVERVIEW

What is Green Power? Why Green Power? Kinds of Green Power

Hydro Wind Biomass Solar Geothermal

Conclusion

WHAT IS GREEN POWER?

“Green” Power: any energy source with a negligible impact on greenhouse gas emissions.

Includes: hydro, wind, biomass, geothermal, & solar

WHY GREEN POWER?

In the 1970s & 1980s the interest in green power was driven by the goal of replacing fossil fuels after the first oil shock in the mid 1970s

Now, the broader goal includes minimizing the emission of CO2.

WHY GREEN POWER?

There are considerable external costs for electricity from fossil fuels that someday must be taken into account as concerns about global warming become real.

While contributions from renewable energy is small, with the exception of hydro, their market penetration is growing at a much faster rate than from conventional sources.

WHY GREEN POWER?

Competition: green option as a means of differentiating their service & winning customer loyalty.

More than 190 electric utilities offer green power in the U.S.

50% of consumers surveyed are willing to pay an extra $15 per month to receive green electricity.

HYDRO

Most mature renewable source of electricity around the world. 700,000 MW contributes 21% of electricity worldwide (year

2000)

Negetive: Limited exploitable sites Potential damage to environment – Indiginous

people of developing countries.

HYDRO

Types Impoundment

Allows operators to stabilize power with fluctuating water levels.

Reduce flooding River – flow.

Relies on river flowing water to keep producing electricity.

HYDRO

Impoundment type Water turns turbines at bottom of the penstock (powerhouse) Turbine attached to series of gears which increase the speed of

rotation. When there is too much water, the spillway allows extra water to

bypass the penstock.

WIND

Second most popular source of green power. 17,500 MW worldwide (70% of which was in

Europe) in 2000 However, in 2001 1,695 MW was added in the

U.S. making it the second largest concentration of wind power in the world.

WIND HAWT: Horizontal-axis wind turbine

Axis about which blades rotate is horizontal Higher height for greater wind speeds All commercially available wind turbine

generators. Utility-scale

Utility-scale typically have greater requirements Solid towers, concrete pads, built on-site.

Individual-scale

VAWT: Vertical-axis wind turbine Axis about which blades rotate is vertical Must be mounted closer to the ground

WIND The nacelle houses the gearbox, generator, and

associated controls. Rotor blades pitch angle may

be controlled to optimize energy

capture with changing wind speeds Prevent damage past design rotational speed

Rounded tips reduce minimum speed

needed to start, and increases aerodynamic

efficiency Cut-in speed: wind speed necessary to

begin producing electricity (as low as 3 m/s)

BIOMASS

Plant matter, trees, grasses, agricultural crops or other biological materials.

14,000 MW of annual worldwide generation capacity.

The U.S. is the largest biomass generator in the world with 7,000 MW.

Expected to grow more than 30,000MW by 2020. Developing countries: availability of cheap feedstock

Bio Materials steam turbine Bio Materials fuel gas engine, turbine or fuel cell Biomass gas may also be integrated into industrial

manufacturing plants for power, heat or cooling needs.

SOLAR -THERMAL Concentrating sunlight and trapping its’ heat

to produce steam 3 types:

Central receiver 2,000 sun-tracking heliostats to single collection vessel Molten salt flowing through the receiver and

transferred to a hot salt storage tank, then steam generator when needed.

Trough based Mirrors are parabolic Tracks the sun on one axis due to linear focus Lower concentration factor Lower cost potential

Dish based Point focused – 2 axis tracking

SOLAR - PHOTOVOLTAIC

800 MW worldwide capacity Fundamental unit: cell Material: semiconductor material

Gallium arsenide Crystalline silicon Amorphous silicon

Available current is a function of cell area & light intensity.

Formed into modules (series & parallel configs) to obtain greater voltage & current.

GEOTHERMAL

Heat at the core of the earth exploited to produce electricity through steam.

7,974 MW generated worldwide (1999) Capital intensive:

enough steam supply wells have to be drilled up-front to provide the full plant capacity at startup.

CONCLUSION

As the concerns about the availability & environmental impacts of fossil fuels become

more wide spread, the interest on environmentally benign renewable energy technologies will surely take center stage

among engineers & policymakers.

Questions?