Alternative Energy Sources: Application of Geothermal, Wave Energy, Biomass and Fusion.

Steven CavadeasDecember 1, 2004

Overview

US consumption Geothermal Biomass Wave Energy Fusion Conclusions

US Electric Consumption*

Total for 2002: 3.95 · 109 MW·hr % Breakdown by source:

2002 Emissions, in Thousands of Metric Tons:

Coal Nuclear Gas Hydro Oil Other

50 20 18 17 2 2

* 2002, from EIA

SO2 NOX CO2

9,940 4,680 2,313,290

Geothermal Basics

Clean (little to no greenhouse gases) and reliable (system availability of 95%).

Steam harvested drive turbines to generate electricity Three types of geothermal power plants

1. Dry steam plants2. Flash steam plants3. Binary-cycle plants

Direct-use reservoirs for heating applications Geothermal Heat Pumps (GHPs) used for heating and

cooling

Powerplants

58 plants in California, Utah, Nevada, and Hawaii are operating with capacity of just under 3000 MW. 27% of Philippine’s electricity

is produced geothermally

Puna power plant in Hawaii. This plant produces about 30% of the electricity demands on the Big Island

Power Plant Economics

Plant Size Unit Cost (US c/kWh)

 

High Quality Medium Quality Low Quality

< 5 MW 5.0 - 7.0 5.5 - 8.5 6.0 - 10.5

5 - 30 MW 4.0 - 6.0 4.5 - 7 Not suitable

> 30 MW 2.5 - 5.0 4.0 - 6.0 Not suitable

Average US retail electricity price: 7.67 c/kWh

Capital cost for coal-fired plants: $600 - $1000 / kW

capacity

Source: Department of Energy

Unit production cost of geothermal electricity

Plant Size High Quality Medium Quality Low Quality

< 5 MW $1600-2300 $1800-3000 $2000-3700

5 - 30 MW $1300-2100 $1600-2500 Not Suitable

> 30 MW $1150-1750 $1350-2200 Not Suitable

Direct capital costs (US $/kW capacity)

Source: The World Bank Group

Source: The World Bank Group

Direct-use Reservoirs

Provide large-scale direct heat for residential, industrial, and commercial uses.

Uses low to moderate temperature water: 68°F – 302°F. Savings of 30% – 50%* when compared to heating with natural gas.

(~$4-$6/tonne steam compared to ~$10/tonne steam) 271 cities within 5 miles of potential resources in western states. Currently 120 separate operations use direct-use.

*Source: U.S. Department of Energy

Geothermal Heat Pumps

Provides small-scale heating for residential and commercial buildings

Uses Earth as heat sink Upper 10 feet of Earth’s surface maintains temperature between 50°F – 60°F. Heat during summer can also be used as energy to heat water.

70% of energy incorporated with this system is from the ground. For a typical 2000 ft2 home in Wisconsin,

Capital cost: $8000 - $10,000. Heating is competitive with fossil fuels, air conditioning is 10% - 20%

cheaper with geothermal than with fossil fuels.Source: U.S. Department of Energy and Alliant Energy

Geothermal Limitations

Geographically limited Only 4 US states have capability

High start up cost due to exploration Small impact on US energy consumption

Only 0.75% of US consumption

Biomass

Uses feedstock from Urban wastes Mill wastes Forest residues Agriculture residues Switchgrass

Primary components are cellulose and hemi cellulose, which can be burned or gasified to produce electricity.

Ag Residues Switchgrass Mill Wastes Urban Wastes Forest Residues SWRC TOTAL

289 254 175 133 103 254 1208

2002 Coal consumption: 1,067 Million tons

1998 US Biomass feedstock availability, in Millions of tons

Biomass Quick Facts

9700 MW installed capacity in 2002 5900 MW from forest products 3300 MW from agricultural residues 500 MW from other capacities

Responsible for 4% of all energy produced in US in 2003 Comprised 47% of all renewable energy in same year

Fewer emissions when compared to coal

Electricity Production from Biomass Three classes for electricity production

Direct-fired Most prevalent, biomass replaces fossil fuels in current plants ~22% efficient

Co-fired Some coal is replaced by biomass, similar to direct-fired 33-37% efficient

Gasification Heat biomass to break solids down to gas Filter and clean gas Combine with gas and steam turbines ~60% efficient Fuel cell applications

Biomass Limitations

Inefficient when compared to coal High transportation costs

Ave. biomass cost: ~ $28/ton Ave. coal cost: ~$23/ton

Geographically limited

Wave Energy

The total power of waves breaking on the world's coastlines is estimated at 2 to 3 million megawatts. In favorable locations, wave energy density can average 65 megawatts per mile of coastline.

Three approaches to capturing energy Floats or pitching devices Oscillating water columns (OWC) Water surge or focusing devices

Floats

Pelton Turbine uses hoses connected to floats that ride the waves.

The rise and fall of the float stretches and relaxes the hose, which pressurizes the water, which, in turn, rotates a turbine.

Situated offshore in ~ 130’ water.

Up to 20 kW generation/float

Oscillating Water Column

As waves enter the air column, they cause the water column to rise and fall. This alternately compresses and depressurizes the air column

Up to 500 kW generation

Most widely used

Focusing Devices

The system consists of a tapered channel, which feeds into a reservoir constructed on cliffs above sea level

Requires near constant wave activity and less than 1 meter tide

Not very practical, only one ever tested

Wave Energy Limitations

Limited to coastlines with heavy surf Energy generation is minimal Eyesore on coastlines Expensive to construct

OWC on the Island of Pico, Azores.

Fusion

Combining of two nuclei

No troublesome emissions

Few or no proliferation concerns

Fuel readily available

Hazardous waste?

Fusion

Magnetic fusion energy (MFE) uses a magnetic field to confine a plasma and hold it at the required density and temperature.

Inertial Fusion Energy (IFE) uses powerful lasers or particle beams focused on a small pellet of fuel for a few billionths of a second.

Fusion Reaction

Get out 4250 times energy input! 1 mole of each reactant yields ~1.6 109 Btu

Enough energy for ~ 45 typical US homes for 1 year.

Deuterium + Tritium He + n0

At 45,000,000 C

Ignition Energy Output Energy

4 keV 17,000 keV

Fusion Limitations

Plasma phase is not fully understood Requires extreme temperatures Impact of wastes?

….But probably best bet for sustainable energy in the future.

Conclusions

As we shift from fossil fuels to another energy source, only nuclear power has the ability to provide a sustainable source

Fusion has possibility to provide clean, efficient, and sustainable energy, more so than fission.

Technological and scientific advances needed before fusion becomes an available alternative.

QUESTIONS???