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“It is pleasant, when the sea is high and the winds are dashing the waves about, to watch from shore the struggles of another.” Lucretius, 99-55 B.C. An.

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Presentation on theme: "“It is pleasant, when the sea is high and the winds are dashing the waves about, to watch from shore the struggles of another.” Lucretius, 99-55 B.C. An."— Presentation transcript:

1 “It is pleasant, when the sea is high and the winds are dashing the waves about, to watch from shore the struggles of another.” Lucretius, B.C. An Introduction to Wave and Tidal Energy Frank R. Leslie, BSEE, MS Space Technology 5/25/2002, Rev. 1.7 (321) Renewable Energy in (and above) the Oceans

2 Overview of Ocean Energy zOcean energy is replenished by the sun and through tidal influences of the moon and sun gravitational forces zNear-surface winds induce wave action and cause wind- blown currents at about 3% of the wind speed zTides cause strong currents into and out of coastal basins and rivers zOcean surface heating by some 70% of the incoming sunlight adds to the surface water thermal energy, causing expansion and flow zWind energy is stronger over the ocean due to less drag, although technically, only seabreezes are from ocean energy

3 What’s renewable energy? zRenewable energy systems transform incoming solar energy and its alternate forms (wind and river flow, etc.), usually without pollution- causing combustion zThis energy is “renewed” by the sun and is “sustainable” zRenewable energy is sustainable indefinitely, unlike long-stored, depleting energy from fossil fuels zRenewable energy from wind, solar, and water power emits no pollution or carbon dioxide zRenewable 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)

4 Renewable Energy (Continued) zFuel combustion produces “greenhouse gases” that are believed to lead to climate change (global warming), thus combustion of biomass is not as desirable as other forms zBiomass combustion is also renewable, but emits CO2 and pollutants yBiomass can be heated with water under pressure to create synthetic fuel gas; but burning biomass creates pollution and CO 2 zNonrenewable energy comes from fossil fuels and nuclear radioactivity (process of fossilization still occurring but trivial) yNuclear energy is not renewable, but sometimes is treated as though it were because of the long depletion period

5 The eventual decline of fossil fuels zMillions of years of incoming solar energy were captured in the form of coal, oil, and natural gas; current usage thus exceeds the rate of original production zCoal may last 250 to 400 years; estimates vary greatly; not as useful for transportation due to losses in converting to liquid “synfuel” zWe can conserve energy by reducing loads and through increased efficiency in generating, transmitting, and using energy zEfficiency and conservation will delay an energy crisis, but will not prevent it

6 Available Energy zPotential Energy: PE = mh zKinetic Energy: KE = ½ mv 2 or ½ mu 2 zWave energy is proportional to wave length times wave height squared (LH 2 )per wave length per unit of crest length yA four-foot (1.2 m), ten-second wave striking a coast expends more than 35, 000 HP per mile of coast [Kotch, p. 247] zMaximum Tidal Energy, E = 2HQ x 353/(778 x 3413) = 266 x HQ kWh/yr, where H is the tidal range (ft) and Q is the tidal flow (lbs of seawater) zE = 2 HQ ft-lb/lunar day (2 tides) or E = 416 x HV kWh, where V is cubic feet of flow

7 Economics zCost of installation, operation, removal and restoration zCompare cost/watt & cost/watt-hour vs. other sources zRelative total costs compared to other sources zExternality costs aren’t included in most assessments zCost of money (inflation) must be included (2 to 5%/year) zLife of energy plant varies and treated as linear depreciation to zero zTax incentives or credits offset the hidden subsidies to fossil fuel and nuclear industry zEnvironmental Impact Statements (EIS) require early funding to justify permitting

8 Ocean Energy zThe tidal forces and thermal storage of the ocean provide a major energy source zWave action adds to the extractable surface energy zMajor ocean currents (like the Gulf Stream) may be exploited to extract energy with underwater rotors (turbines) zThe oceans are the World’s largest solar collectors (71% of surface) zThermal differences between surface and deep waters can drive heat engines zOver or in proximity to the ocean surface, the wind moves at higher speeds over water than over land roughness

9 Wave Energy zEnergy of interchanging potential and kinetic energy in the wave zCycloidal motion of wave particles carries energy forward without much current zTypical periodicities are one to thirty seconds, thus there are low-energy periods between high-energy points zIn 1799, Girard & son of Paris proposed using wave power for powering pumps and saws zCalifornia coast could generate 7 to 17 MW per mile [Smith, p. 91]

10 Ocean Energy: Wave Energy zWave energy potential varies greatly worldwide Source: Wave Energy paper. IMechE, 1991 and European Directory of Renewable Energy (Suppliers and Services) 1991 Figures in kW/m

11 Concepts of Wave Energy Conversion zChange of water level by tide or wave can move or raise a float, producing linear motion from sinusoidal motion zWater current can turn a turbine to yield rotational mechanical energy to drive a pump or generator ySlow rotation speed of approximately one revolution per second to one revolution per minute less likely to harm marine life yTurbine reduces energy downstream and could protect shoreline zArchimedes Wave Swing is a Dutch device [Smith, p. 91]

12 Salter “Ducks” zScottish physicist Prof. Stephen Salter invented “Nodding Duck” energy converter in 1970 zSalter “ducks” rock up and down as the wave passes beneath it. This oscillating mechanical energy is converted to electrical energy zDestroyed by storm zA floating two-tank version drives hydraulic rams that send pressurized oil to a hydraulic motor that drives a generator, and a cable conducts electricity to shore Ref.: TidalPower.html ©1996 Ramage

13 Fluid-Driven Wave Turbines zWaves can be funneled and channeled into a rising chute to charge a reservoir over a weir or through a swing-gate yWater passes through waterwheel or turbine back to the ocean yAlgerian V-channel [Kotch, p.228] zWave forces require an extremely strong structure and mechanism to preclude damage zThe Ocean Power Delivery wave energy converter Pelamis has articulated sections that stream from an anchor towards the shore yWaves passing overhead produce hydraulic pressure in rams between sections yThis pressure drives hydraulic motors that spin generators, and power is conducted to shore by cable y750 kW produced by a group 150m long and 3.5m diameter

14 Fluid-Driven Wave Turbines zDavis Hydraulic Turbines since 1981 yMost tests done in Canada y4 kW turbine tested in Gulf Stream zBlue Energy of Canada developing two 250 kW turbines for British Columbia zAlso proposed Brothers Island tidal fence in San Francisco Bay, California 1000 ft long by 80 ft deep to produce 15 – 25 MW zAustralian Port Kembla (south of Sydney) to produce 500 kW

15 Air-Driven Wave Turbines (Con’t) z A floating buoy can compress trapped air similar to a whistle buoy zThe oscillating water column (OWC) in a long pipe under the buoy will lag behind the buoy motion due to inertia of the water column zThe compressed air spins a turbine/alternator to generate electricity at $0.09/kWh The Japanese “Mighty Whale” has an air channel to capture wave energy. Width is 30m and length is 50 m. There are two 30 kW and one50 kW turbine/generators

16 Air-Driven Wave Turbines zBritish invention uses an air-driven Wells turbine with symmetrical blades zIncoming waves pressurize air within a heavy concrete box, and trapped air rushes upward through pipe connecting the turbine zA Wavegen™, wave-driven, air compressor or oscillating water column (OWC) spins a two-way Wells turbine to produce electricity zWells turbine is spun to starting speed by external electrical power and spins the same direction regardless of air flow direction zEnergy estimated at 65 megawatts per mile Photo by Wavegen

17 Ocean Energy: Tidal Energy zTides are produced by gravitational forces of the moon and sun and the Earth’s rotation zExisting and possible sites: yFrance: 1966 La Rance river estuary 240 MW station xTidal ranges of 8.5 m to 13.5 m; 10 reversible turbines yEngland: Severn River yCanada: Passamaquoddy in the Bay of Fundy (1935 attempt failed) yCalifornia: high potential along the northern coast zEnvironmental, economic, and esthetic aspects have delayed implementation zPower is asynchronous with load cycle

18 Tidal Energy zTidal mills were used in the Tenth and Eleventh Centuries in England, France, and elsewhere zMillpond water was trapped at high tide by a gate (Difficult working hours for the miller; Why?) yRhode Island, USA, 18 th Century, 20-ton wheel 11 ft in diameter and 26 ft wide yHamburg, Germany, 1880 “mill” pumped sewage ySlade’s Mill in Chelsea, MA founded 1734, 100HP, operated until ~1980 yDeben estuary, Woodbridge, Suffolk, England has been operating since 1170 (reminiscent of “the old family axe”; only had three new handles and two new heads!) yTidal mills were common in USA north of Cape Cod, where a 3 m range exists [Redfield, 1980] yBrooklyn NY had tidal mill in 1636 [?]

19 Tidal Energy (continued) zPotential energy = S integral from 0 to 2H (ρgz dz), where S is basin area, H is tidal amplitude, ρ is water density, and g is gravitational constant yielding 2 S ρ gH 2 zMean power is 2 S ρ gH 2 /tidal period; semidiurnal better zTidal Pool Arrangements ySingle-pool empties on ebb tide ySingle-pool fills on flood tide ySingle-pool fills and empties through turbine yTwo-pool ebb- and flood-tide system; two ebbs per day; alternating pool use yTwo-pool one-way system (high and low pools) (turbine located between pools)

20 Tidal Water Turbines zCurrent flow converted to rotary motion by tidal current zTurbines placed across Rance River, France zLarge Savonius rotors (J. S. Savonius, 1932?) placed across channel to rotate at slow speed but creating high torque (large current meter) zHorizontal rotors proposed for Gulf Stream placement off Miami, Florida

21 Tidal Flow: Rance River, France z240 MW plant with 24, 10 MW turbines operated since 1966 zAverage head is 28 ft zArea is approximately 8.5 square miles zFlow approx, 6.64 billion cubic feet zMaximum theoretical energy is 7734 million kWh/year; 6% extracted zStorage pumping contributes 1.7% to energy level zAt neap tides, generates 80,000 kWh/day; at equinoctial spring tide, 1,450,000 kWh/day (18:1 ratio!); average ~500 million kWh/year zProduces electricity cheaper than oil, coal, or nuclear plants in France

22 Tidal Flow: Passamaquoddy, Lower Bay of Fundy, New Brunswick, Canada zProposed to be located between Maine (USA) and New Brunswick zAverage head is 18.1 ft zFlow is approximately 70 billion cubic feet per tidal cycle zArea is approximately 142 square miles zAbout 3.5 % of theoretical maximum would be extracted zTwo-pool approach greatly lower maximum theoretical energy zInternational Commission studied it 1956 through 1961 and found project uneconomic then zDeferred until economic conditions change [Ref.: Harder]

23 Other Tidal Flow Plants under Study zAnnapolis River, Nova Scotia: straight-flow turbines; demonstration plant was to be completed in 1983; 20 MW; tides 29 to 15 feet; Tidal Power Corp.; ~$74M zExperimental site at Kislaya Guba on Barents Sea yFrench 400 kW unit operated since 1968 yPlant floated into place and sunk: dikes added to close gaps zSea of Okhotsk (former Sov. Union) under study in 1980 zWhite Sea, Russia: 1 MW, 1969 zMurmansk, Russia: 0.4 MW zKiansghsia in China

24 Other Tidal Flow Plants under Study (continued) zSevern River, Great Britain: range of 47 feet (14.5 m) calculated output of 2.4 MWh annually. Proposed at $15B, but not economic. zChansey Islands:20 miles off Saint Malo, France; 34 billion kWh per year; not economic; environmental problems; project shelved in 1980 zSan Jose, Argentina: potential of 75 billion kWh/year; tidal range of 20 feet (6m) zChina built several plants in the 1950s zKorean potential sites (Garolim Bay)

25 Hydraulic Pressure Absorbers zLarge synthetic rubber bags filled with water could be placed offshore where large waves pass overhead yAlso respond to tides yA connecting pipe conducts hydraulic pressure to a positive displacement motor that spins a generator yThe motor can turn a generator to make electricity that varies sinusoidally with the pressure

26 Ocean Thermal Energy: OTEC (Ocean Thermal Electric Conversion) zFrench Physicist Jacque D’Arsonval proposed in 1881 zGeorges Claude built Matanzos Bay, Cuba 22 kW plant in 1930 [Smith, p.94] zKeahole Point, Hawaii has the US 50 kW research OTEC barge system zOTEC requires some 36 to 40°F temperature difference between the surface and deep waters to extract energy zOpen-cycle plants vaporize warm water and condense it using the cold sea water, yielding potable water and electricity from turbines-driven alternators zClosed-cycle units evaporate ammonia at 78°F to drive a turbine and an alternator Ref.: zHybrid cycle uses open-cycle steam to vaporize closed-cycle ammonia zChina also has experimented with OTEC

27 Wind Energy Equations (also applies to water turbines) zAssume a “tube” of air the diameter, D, of the rotor yA = π D 2 /4 zA length, L, of air moves through the turbine in t seconds yL = u·t, where u is the wind speed zThe tube volume is V = A·L = A·u·t zAir density, ρ, is kg/m 3 (water density ~1000 kg/m 3 ) zMass, m = ρ·V = ρ·A·u·t, where V is volume zKinetic energy = KE = ½ mu

28 Wind Energy Equations (continued) zSubstituting ρ·A·u·t for mass, and A = π D 2 /4, KE = ½·π/4·ρ·D 2 ·u 3 ·t zTheoretical power, P t = ½·π/4·ρ·D 2 ·u 3 ·t/t = ·ρ a ·D 2 ·u 3, ρ (rho) is the density, D is the diameter swept by the rotor blades, and u is the speed parallel to the rotor axis zBetz Law shows 59.3% of power can be extracted zP e = P t ·59.3%·ή r ·ή t ·ή g, where P e is the extracted power, ή r is rotor efficiency, ή t is transmission efficiency, and ή g is generator efficiency zFor example, 59.3%·90%·98%·80% = 42% extraction of theoretical power

29 Generic Trades in Energy zEnergy trade-offs required to make rational decisions  PV is expensive ($4 to 5 per watt for hardware + $5 per watt for shipping and installation = $10 per watt) compared to wind energy ( $1.5 per watt for hardware + $5 per watt for installation = $6 per watt total ) zAre Compact Fluorescent Lamps (CFLs) always better to use than incandescent? Ref.: pictures/general/ windfarm/index.asp?i=2 Ref.: education/story/story- images/solar.jpeg Photo of FPL’s Cape Canaveral Plant by F. Leslie,

30 Energy Storage zRenewable energy is often intermittent, and storage allows alignment with time of use. zCompressed air, flywheels, weight-shifting (pumped water storage at Niagara Falls) zBatteries are traditional for small systems and electric vehicles; first cars (1908) were electric details.solar_electric.html zHydrogen can be made by electrolysis zEnergy is best stored as a financial credit through “net metering” yNet metering requires a utility to bill at the same rate for buying or selling energy

31 Energy Transmission zElectricity and hydrogen are energy carriers, not natural fuels zElectric transmission lines lose energy in heat (~2% to 5%); trades loss vs. cost zLine flow directional analysis can show where new energy plants are required to reduce energy transmission zHydrogen is made by electrolysis of water, cracking of natural gas, or from bacterial action (lab experiment level) zOil and gas pipelines carry storable energy yPipelines (36” or larger) can transport hydrogen without appreciable energy loss due to low density and viscosity yMore efficient than 500 kV transmission line and is out of view

32 Legal aspects and other complications zPURPA: Public Utility Regulatory Policy Act of Utility purchase from and sale of power to qualified facilities; avoided costs offsetting basis of purchases zEnergy Policy Act of 1992 leads to deregulation z“NIMBYs” rally to shrilly insist “Not In My Backyard”! zInvestment taxes and subsidies favor fossil and nuclear power zHigh initial cost dissuades potential users; future is uncertain zLack of uniform state-level net metering hinders offsetting costs zEnvironmental Impact Statements (EIS) require extensive and expensive research and trade studies zNumerous “public interest” advocacy groups are well-funded and ready to sue to stop projects

33 Conclusion zRenewable energy offers a long- term approach to the World’s energy needs zEconomics drives the energy selection process and short-term (first cost) thinking leads to disregard of long-term, overall cost zWave and tidal energy are more expensive than wind and solar energy, the present leaders zIncreasing oil, gas, and coal prices will ensure that the transition to renewable energy occurs zOffshore and shoreline wind energy plants offer a logical approach to part of future energy supplies

34 References: Books, etc. zGeneral: ySørensen, Bent. Renewable Energy, Second Edition. San Diego: Academic Press, 2000, 911 pp. ISBN yHenry, J. Glenn and Gary W. Heinke. Environmental Science and Engineering. Englewood Cliffs: Prentice- Hall, 728pp., , TD146.H45, dc19 yBrower, Michael. Cool Energy. Cambridge MA: The MIT Press, , TJ807.9.U6B76, ’4’0973. yDi Lavore, Philip. Energy: Insights from Physics. NY: John Wiley & Sons, 414pp., l, TJ163.2.D54, yBowditch, Nathaniel. American Practical Navigator. Washington:USGPO, H.O. Pub. No. 9. yHarder, Edwin L. Fundamentals of Energy Production. NY: John Wiley & Sons, 368pp., , TJ163.9.H37, Tidal Energy, pp zWind: yPatel, Mukund R. Wind and Solar Power Systems. Boca Raton: CRC Press, 1999, 351 pp. ISBN , TK1541.P , ’2136 yGipe, Paul. Wind Energy for Home & Business. White River Junction, VT: Chelsea Green Pub. Co., , TJ820.G57, 621.4’5 yJohnson, Gary L, Wind Energy Systems. Englewood Cliffs NJ: Prentice-Hall, Inc. TK 1541.J ’5; zWaves: zSmith, Douglas J. “Big Plans for Ocean Power Hinges on Funding and Additional R&D”. Power Engineering, Nov. 2001, p. 91. zKotch, William J., Rear Admiral, USN, Retired. Weather for the Mariner. Annapolis: Naval Institute Press, , QC994.K64, Chap. 11, Wind, Waves, and Swell. zSolar: yDuffie, John and William A. Beckman. Solar Engineering of Thermal Processes. NY: John Wiley & Sons, Inc., 920 pp.,

35 References: Internet zGeneral: yhttp://www.google.com/search?q=%22renewable+energy+course%22 yhttp://www.ferc.gov/ Federal Energy Regulatory Commission yhttp://solstice.crest.org/ yhttp://dataweb.usbr.gov/html/powerplant_selection.html yhttp://www.dieoff.org. Site devoted to the decline of energy and effects upon population zTidal: yhttp://www.unep.or.kr/energy/ocean/oc_intro.htmhttp://www.unep.or.kr/energy/ocean/oc_intro.htm yhttp://www.bluenergy.com/technology/prototypes.htmlhttp://www.bluenergy.com/technology/prototypes.html yhttp://www.iclei.org/efacts/tidal.htmhttp://www.iclei.org/efacts/tidal.htm yhttp://zebu.uoregon.edu/1996/ph162/l17b.html zWaves: yhttp://www.env.qld.gov.au/sustainable_energy/publicat/ocean.htm yhttp://www.bfi.org/Trimtab/summer01/oceanWave.htmhttp://www.bfi.org/Trimtab/summer01/oceanWave.htm yhttp://www.oceanpd.com/http://www.oceanpd.com/ yhttp://www.newenergy.org.cn/english/ocean/overview/status.htmhttp://www.newenergy.org.cn/english/ocean/overview/status.htm yhttp://www.energy.org.uk/EFWave.htmhttp://www.energy.org.uk/EFWave.htm yhttp://www.earthsci.org/esa/energy/wavpwr/wavepwr.html

36 References: Internet zThermal: yhttp://www.nrel.gov/otec/what.htmlhttp://www.nrel.gov/otec/what.html yhttp://www.hawaii.gov/dbedt/ert/otec_hi.html#anchor on OTEC systems zWind: Wind Energy elist Wind energy home powersite elist yhttp://telosnet.com/wind/20th.html

37 Units and Constants zUnits: yPower in watts (joules/second) yEnergy (power x time) in watt-hours zConstants: y1 m = ft exactly by definition y1 mile = km; 1m/s = mi/h (mph) y1 mile 2 = ft 2 = m 2 y1 ft 2 = m 2 ; 1 m 2 = ft 2 y1 ft 3 = L = 7.34 gallon = m 3 ; 1 m 3 = US gallons y1 m 3 /s = US gallons/minute yg = 32.2 ft/s 2 = 9.81 m/s 2 ; 1 kg = 2.2 pounds yAir density, ρ (rho), is kg/m 3 or pounds/ft 3 at 20ºC at sea level ySolar Constant: 1368 W/m 2 exoatmospheric or 342 W/m 2 surface (80 to 240 W/m 2 ) y1 HP = 550 ft-lbs/s = BTU/min = = 746 W (J/s) y1 BTU = 252 cal = Wh = kJ y1 atmosphere = psi = 33.9 ft water = kPa = 76 cm Hg = mbar y1 boe (42- gallon barrel of oil equivalent) = 1700 kWh

38 Energy Equations zElectricity: yE=IR; P=I 2 R; P=E 2 /R, where R is resistance in ohms, E is volts, I is current in amperes, and P is power in watts y Energy = P t, where t is time in hours zTurbines: yP a = ½ ρ A 2 u 3, where ρ (rho) is the fluid density, A = rotor area in m 2, and u is wind speed in m/s yP = R ρ T, where P = pressure (Nm -2 = Pascal) yTorque, T = P/ω, in Nm/rad, where P = mechanical power in watts, ω is angular velocity in rad/sec zPumps: yPm = gQ m h/ή p W, where g=9.81 N/kg, Q m is mass capacity in kg/s, h is head in m, and ή p is pump mechanical efficiency


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