Energy Ocean Wind Intro

8/8/2019 Energy Ocean Wind Intro

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An Introduction to Ocean

and Sea Breeze Wind Energy

Frank R. Leslie,

BSEE, MS Space Technology

5/25/2002, Rev. 1.7

[email protected]; (321) 768-6629

Renewable Energy from Ocean Winds


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Overview of Ocean Energy

Ocean energy is replenished by the sun and throughtidal influences of the moon and sun gravitational forces

Near-surface winds induce wave action and cause wind-

blown currents at about 3% of the wind speed Tides cause strong currents into and out of coastal

basins and rivers

Ocean surface heating by some 70% of the incomingsunlight adds to the surface water thermal energy,causing expansion and flow

Wind energy is stronger over the ocean due to less drag,although technically, only seabreezes are from oceanenergy

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Whats renewable energy?

Renewable energy systems transform incoming solar energy and itsalternate forms (wind and river flow, etc.), usually without pollution-causing combustion

This energy is renewed by the sun and is sustainable

Renewable energy is sustainable indefinitely, unlike long-stored,depleting energy from fossil fuels

Renewable energy from wind, solar, and water power emits nopollution or carbon dioxide

Renewable energy is nonpolluting since no combustion occurs(although the building of the components does in making steel, etc.,for conversion machines does pollute during manufacture)

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Renewable Energy (Continued)

Fuel combustion produces greenhouse gases that are believed tolead to climate change (global warming), thus combustion ofbiomass is not as desirable as other forms

Biomass combustion is also renewable, but emits CO2 andpollutants

Biomass can be heated with water under pressure to createsynthetic fuel gas; but burning biomass creates pollution andCO2

Nonrenewable energy comes from fossil fuels and nuclearradioactivity (process of fossilization still occurring but trivial)

Nuclear energy is not renewable, but sometimes is treated asthough it were because of the long depletion period

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The eventual decline

of fossil fuels

Millions of years of incoming solar energy were capturedin the form of coal, oil, and natural gas; current usagethus exceeds the rate of original production

Coal may last 250 to 400 years; estimates vary greatly;not as useful for transportation due to losses inconverting to liquid synfuel

We can conserve energy by reducing loads and through

increased efficiency in generating, transmitting, andusing energy

Efficiency and conservation will delay an energy crisis,but will not prevent it

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Available Energy

Potential Energy: PE = mh

Kinetic Energy: KE = mv2 or mu2

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Economics

Cost of installation, operation, removal and restoration

Compare cost/watt & cost/watt-hour vs. other sources

Relative total costs compared to other sources

Externality costs arent included in most assessments

Cost of money (inflation) must be included (2 to 5%/year)

Life of energy plant varies and treated as linear depreciation to zero

Tax incentives or credits offset the hidden subsidies to fossil fuel

and nuclear industry Environmental Impact Statements (EIS) require early funding to

justify permitting

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Ocean Wind Energy

Over or in proximity to the ocean surface, the windmoves at higher speeds over water than over landroughness

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Ocean Wind Energy

Wind energy results from uneven heating of the atmosphere

Wind resources vary greatly worldwide; strong over oceans

Power is proportional to the cube of the wind speed

Ref.: www.freefoto.com/pictures/general/ windfarm/index.asp?i=2

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Ocean Wind Energy (continued)

Long fetch (distance) of unhindered wind increasesspeed and available energy beyond land installations

Offshore wind turbines diminish public outcry againstwind turbines (low visibility, monopod supports)

Turbines are typically placed on concrete supports ingroups; rotors are often 80 m in diameter

Turbines are also placed along a coast on the foreshorearea to intercept the prevailing wind from over the ocean

Must avoid bird migration routes; turbine ~20 to 30 rpm

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Ocean Wind Energy (continued)

Present and planned offshore wind energy plants willsupply significant consumer demand and reduce needfor coal- and oil-fired plants and resultant pollution

Middlegrunden near Denmark

Oil-drilling platforms

Small auxiliary turbine

Platform design can be modified to support largewind turbine

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Wind Energy Equations

(also applies to water turbines)

Assume a tube of air the diameter, D, of the rotor

A = D2/4

A length, L, of air moves through the turbine in t seconds L = ut, where u is the wind speed

The tube volume is V = AL = Aut

Air density, , is 1.225 kg/m3 (water density ~1000

kg/m3

) Mass, m = V = Aut, where V is volume

Kinetic energy = KE = mu2

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Wind Energy Equations(continued)

Substituting Aut for mass, andA = D2/4 , KE = /4D2u3t

Theoretical power, Pt = /4D2u3t/t = 0.3927aD

2u3,

(rho) is the density, D is the diameter swept by the rotor blades, and u is the speedparallel to the rotor axis

Betz Law shows 59.3% of power can be extracted

Pe = Pt59.3%rtg, where Pe is the extracted power, r is rotorefficiency, t is transmission efficiency, and g is generatorefficiency

For example, 59.3%90%98%80% = 42% extraction of theoreticalpower

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Generic Trades in Energy

Energy trade-offs required tomake rational decisions

PV is expensive ($4 to 5 perwatt for hardware + $5 per wattfor shipping and installation =$10 per watt)

compared to wind energy($1.5 per watt for hardware+ $5 per watt forinstallation = $6 per watt

total)

Are Compact FluorescentLamps (CFLs) always betterto use than incandescent?

Ref.: www.freefoto.com/pictures/general/windfarm/index.asp?i=2

Ref.:http://www.energy.ca.gov/

education/story/story-images/solar.jpeg

Photo ofFPLsCapeCanaveralPlant byF. Leslie,2001

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Energy Storage

Renewable energy is often intermittent, and storageallows alignment with time of use.

Compressed air, flywheels, weight-shifting (pumped

water storage at Niagara Falls) Batteries are traditional for small systems and electric

vehicles; first cars (1908) were electric

www.strawbilt.org/systems/ details.solar_electric.html

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Hydrogen can be made by electrolysis

Energy is best stored as a financial credit throughnet metering

Net metering requires a utility to bill at thesame rate for buying or selling energy


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Energy

Transmission

Electricity and hydrogen are energy carriers, not natural fuels

Electric transmission lines lose energy in heat (~2% to 5%); tradesloss vs. cost

Line flow directional analysis can show where new energy plants arerequired to reduce energy transmission

Hydrogen is made by electrolysis of water, cracking of natural gas, orfrom bacterial action (lab experiment level)

Oil and gas pipelines carry storable energy

Pipelines (36 or larger) can transport hydrogen without appreciableenergy loss due to low density and viscosity

More efficient than 500 kV transmission line and is out of view

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Legal aspects and other

complications

PURPA: Public Utility Regulatory Policy Act of 1978. Utilitypurchase from and sale of power to qualified facilities; avoidedcosts offsetting basis of purchases

Energy Policy Act of 1992 leads to deregulation

NIMBYs rally to shrilly insist Not In My Backyard!

Investment taxes and subsidies favor fossil and nuclear power

High initial cost dissuades potential users; future is uncertain

Lack of uniform state-level net metering hinders offsetting costs

Environmental Impact Statements (EIS) require extensive andexpensive research and trade studies

Numerous public interest advocacy groups are well-funded andready to sue to stop projects

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Conclusion

Renewable energy offers along-term approach to theWorlds energy needs

Economics drives the energyselection process and short-term (first cost) thinking leadsto disregard of long-term,overall cost

Increasing oil, gas, and coalprices will ensure that thetransition to renewable energy

occurs Offshore and shoreline wind

energy plants offer a logicalapproach to part of futureenergy supplies

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References: Books, etc.

General: Srensen, Bent. Renewable Energy, Second Edition. San Diego: Academic Press, 2000, 911 pp. ISBN 0-

12-656152-4. Henry, J. Glenn and Gary W. Heinke. Environmental Science and Engineering. Englewood Cliffs: Prentice-

Hall, 728pp., 1989. 0-13-283177-5, TD146.H45, 620.8-dc19 Brower, Michael. Cool Energy. Cambridge MA: The MIT Press, 1992. 0-262-02349-0, TJ807.9.U6B76,

333.7940973. Di Lavore, Philip. Energy: Insights from Physics. NY: John Wiley & Sons, 414pp., 1984. 0-471-89683-7l,

TJ163.2.D54, 621.042. Bowditch, Nathaniel. American Practical Navigator. Washington:USGPO, H.O. Pub. No. 9. Harder, Edwin L. Fundamentals of Energy Production. NY: John Wiley & Sons, 368pp., 1982. 0-471-08356-

9, TJ163.9.H37, 333.79. Tidal Energy, pp. 111-129.

Wind: Patel, Mukund R. Wind and Solar Power Systems. Boca Raton: CRC Press, 1999, 351 pp. ISBN 0-8493-

1605-7, TK1541.P38 1999, 621.312136 Gipe, Paul. Wind Energy for Home & Business. White River Junction, VT: Chelsea Green Pub. Co., 1993.

0-930031-64-4, TJ820.G57, 621.45 Johnson, Gary L, Wind Energy Systems. Englewood Cliffs NJ: Prentice-Hall, Inc. TK 1541.J64 1985.

621.45; 0-13-957754-8. Waves:

Smith, Douglas J. Big Plans for Ocean PowerHinges on Funding and Additional R&D. Power Engineering, Nov.2001, p. 91.

Kotch, William J., RearAdmiral, USN, Retired. Weather for the Mariner. Annapolis: Naval Institute Press, 1983.551.5, QC994.K64, Chap. 11, Wind, Waves, and Swell.

Solar: Duffie, John and William A. Beckman. Solar Engineering of Thermal Processes. NY: John Wiley & Sons,

Inc., 920 pp., 1991.

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References: Internet

General: http://www.google.com/search?q=%22renewable+energy+course%22

http://www.ferc.gov/ Federal Energy Regulatory Commission

http://solstice.crest.org/

http://dataweb.usbr.gov/html/powerplant_selection.html

http://mailto:[email protected]

http://www.dieoff.org. Site devoted to the decline of energy and effects upon population

Tidal: http://www.unep.or.kr/energy/ocean/oc_intro.htm

http://www.bluenergy.com/technology/prototypes.html

http://www.iclei.org/efacts/tidal.htm

http://zebu.uoregon.edu/1996/ph162/l17b.html

Waves: http://www.env.qld.gov.au/sustainable_energy/publicat/ocean.htm http://www.bfi.org/Trimtab/summer01/oceanWave.htm

http://www.oceanpd.com/ http://www.newenergy.org.cn/english/ocean/overview/status.htm

http://www.energy.org.uk/E FWave.htm

http://www.earthsci.org/esa/energy/wavpwr/wavepwr.html

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References: Internet

Thermal: http://www.nrel.gov/otec/what.html

http://www.hawaii.gov/dbedt/ert/otec_hi.html#anchor349152 on OTEC systems

Wind: http://[email protected]. Wind Energy elist

http://[email protected]. Wind energy home powersite elist

http://telosnet.com/wind/20th.html

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Units and Constants

Units: Power in watts (joules/second) Energy (power x time) in watt-hours

Constants: 1 m = 0.3048 ft exactly by definition

1 mile = 1.609 km; 1m/s = 2.204 mi/h (mph) 1 mile2 = 27878400 ft2 = 2589988.11 m2

1 ft2 = 0.09290304 m2; 1 m2 = 10.76391042 ft2

1 ft3 = 28.32 L = 7.34 gallon = 0.02832 m3; 1 m3 = 264.17 US gallons 1 m3/s = 15850.32 US gallons/minute g = 32.2 ft/s2 = 9.81 m/s2; 1 kg = 2.2 pounds Air density, (rho), is 1.225 kg/m3 or 0.0158 pounds/ft3 at 20C at sea level

Solar Constant: 1368 W/m2 exoatmospheric or 342 W/m2 surface (80 to 240W/m2)

1 HP = 550 ft-lbs/s = 42.42 BTU/min = = 746 W (J/s) 1 BTU = 252 cal = 0.293 Wh = 1.055 kJ 1 atmosphere = 14.696 psi = 33.9 ft water = 101.325 kPa = 76 cm Hg =1013.25

mbar 1 boe (42- gallon barrel of oil equivalent) = 1700 kWh

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Energy Equations

Electricity: E=IR; P=I2 R; P=E2/R, where R is resistance in ohms, E is volts,

I is current in amperes, and P is power in watts Energy = P t, where t is time in hours

Turbines: Pa = A

2 u3, where (rho) is the fluid density, A = rotor areain m2, and u is wind speed in m/s

P = R T, where P = pressure (Nm-2 = Pascal) Torque, T = P/, in Nm/rad, where P = mechanical power in

watts, is angular velocity in rad/sec Pumps:

Pm = gQmh/p W, where g=9.81 N/kg, Qm is mass capacity inkg/s, h is head in m, and p is pump mechanical efficiency

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Energy Ocean Wind Intro