1
2	15.N In Other News . . . “Gulf Stream Turbines has developed a turbine system it says could produce electricity continuously from the ocean current running from the Gulf of Mexico and up the US Atlantic Coast “ Gulf Stream turbine inventors seek investors Thursday March 25, 2010 By James Cartledge
3	16.O Overview of Ocean Energy Ocean energy is replenished by the sun and through tidal 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 incoming sunlight 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 ocean energy
4	16.0 About This Presentation 16.1.1 Tidal Energy 16.1.2 Tidal Water Turbines 16.2.1 Wave Energy 16.3 Ocean Thermal Energy Convertors 16.4 Ocean Currents 16.5 Ocean Wind 16.6 Economics 16.0 Conclusion
5	16.1.1 Tidal Energy Tidal mills were used in the Tenth and Eleventh Centuries in England, France, and elsewhere Millpond water was trapped at high tide by a gate (Difficult working hours for the miller! Why?) Deben estuary, Woodbridge, Suffolk, England has been operating since 1170 (reminiscent of “the old family axe”; only had three new handles and two new heads!) Brooklyn NY had tidal mill at Bull Creek in 1636 (details at http://watercourses.typepad.com/watercourses/water-old-mill-creekbull-creek-east-new-yorkcanarsie-brooklyn/) Rhode Island, USA, 18^th Century, 20-ton wheel 11 ft in diameter and 26 ft wide ** Slade’s Mill in Chelsea, MA founded 1734, 100HP, operated until ~1980 Hamburg, Germany, 1880 “mill” pumped sewage Tidal mills were common in USA north of Cape Cod, where a 3 m range exists [Redfield, 1980]
6	16.1.1 Tidal Energy (continued) Tides are produced by gravitational forces of the moon and sun and the Earth’s rotation Existing and possible sites: France: 1966 La Rance river estuary 240 MW station Tidal ranges of 8.5 m to 13.5 m; 10 reversible turbines England: Severn River proposed Canada: Passamaquoddy Bay in the Bay of Fundy (1935 attempt failed); Truro Bay site operational. California: high potential along the northern coast Environmental, economic, and esthetic aspects have delayed implementation Power is asynchronous with daily load cycle
7	16.1.1 Tidal Energy (continued)
8	16.1.1 Tidal Energy (continued) Potential energy = ∫ S from 0 to 2H (ρgz dz), where S is basin area, H is tidal amplitude (high to low), ρ is water density, and g is the gravitational constant yielding 2 S ρ gH² Mean power is 2 S ρ gH²/tidal period; semidiurnal better Tidal Pool Arrangements Single-pool empties on ebb tide (going low) Single-pool fills on flood tide (going high) Single-pool fills and empties through turbine (both ways) Two-pool ebb- and flood-tide system; two ebbs per day; alternating pool use Two-pool one-way system (high and low pools) (turbine located between pools)
9	16.1.1 Tidal Energy (continued)
10	16.1.2 Tidal Water Turbines Current flow converted to rotary motion by tidal current Turbines placed across The Rance River, France Large Savonius rotors (J. S. Savonius, 1932?) placed across channel to rotate at slow speed but creating high torque (a large current meter) Horizontal rotors proposed for Gulf Stream placement off Miami, Florida by FAU (Dr. Rick Driscoll, Director) East River, NYC, has some turbines installed Blades failed at hub, and now replaced with new
11	16.1.2 Tidal Energy (continued)
12	16.1.2 Tidal Currents (continued)
13	16.1.2 Tidal Energy (continued)
14	16.1.2 Tidal Flow: Rance River, France 240 MW plant with 24, 10 MW turbines operated since 1966 Average head is 28 ft Area is approximately 8.5 square miles Flow approx, 6.64 billion cubic feet Maximum theoretical energy is 7734 million kWh/year; 6% extracted Storage pumping contributes 1.7% to energy level At neap tides, generates 80,000 kWh/day; at equinoctial spring tide, 1,450,000 kWh/day (18:1 ratio!); average ~500 million kWh/year Produces electricity cheaper than oil, coal, or nuclear plants in France
15	16.1.2 Tidal Flow: Passamaquoddy, Lower Bay of Fundy, New Brunswick, Canada Proposed to be located between Maine (USA) and New Brunswick Average head is 18.1 ft Flow is approximately 70 billion cubic feet per tidal cycle Area is approximately 142 square miles About 3.5 % of theoretical maximum would be extracted Two-pool approach greatly lowers maximum theoretical energy International Commission studied it 1956 through 1961 and found project uneconomic then Deferred until economic conditions change
16	16.1.2 Tidal Energy (continued)
17	16.1.2 Other Tidal Flow Plants under Study Annapolis 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 Experimental site at Kislaya Guba on Barents Sea French 400 kW unit operated since 1968 Plant floated into place and sunk: dikes added to close gaps Sea of Okhotsk (former Sov. Union) under study in 1980 White Sea, Russia: 1 MW, 1969 Murmansk, Russia: 0.4 MW Kiansghsia in China
18	16.1.2 Other Tidal Flow Plants under Study (continued) Severn River, Great Britain: range of 47 feet (14.5 m) calculated output of 2.4 MWh annually. Proposed at $15B, but not economic. Chansey Islands: 20 miles off Saint Malo, France; 34 billion kWh per year; not economic; environmental problems; project shelved in 1980 San Jose, Argentina: potential of 75 billion kWh/year; tidal range of 20 feet (6m) China built several plants in the 1950s Korean potential sites (Garolim Bay)
19	16.2.1 Wave Energy
20	16.2.1 Wave Energy (continued) Change of water level by tide or wave can move or raise a float, producing linear motion from sinusoidal motion Water current can turn a turbine to yield rotational mechanical energy to drive a pump or generator Slow rotation speed of approximately one revolution per second to one revolution per minute less likely to harm marine life Turbine reduces energy downstream and could protect shoreline Archimedes Wave Swing is a Dutch device [Smith, p. 91]
21	16.2.1 Wave Energy (continued) Wave energy potential varies greatly worldwide
22	16.2.1 Wave characteristics
23	16.2.1.1 Wave Energy E = 1/8 ρ g H² Where E = energy, and H is the high-to-low wave height P = E n C Where P = power in the wavefront, n = the ratio of energy propagation to the phase speed, and C = phase speed of the wave P = ρ g²TH² / (32 pi) Where P = power, g = gravitation constant, T = wave period, and H = wave height
24	16.2.2 Wave Energy: Salter “Ducks” Scottish physicist Prof. Stephen Salter invented “Nodding Duck” energy converter in 1970 Salter “ducks” rock up and down as the wave passes beneath it. This oscillating mechanical energy is converted to electrical energy Destroyed by storm A 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
25	16.2.2 Wave Energy: OWEB
26	16.2.2 Fluid-Driven Wave Turbines Waves can be funneled and channeled into a rising chute to charge a reservoir over a weir or through a swing-gate Water passes through waterwheel or turbine back to the ocean Algerian V-channel [Kotch, p.228] Wave forces require an extremely strong structure and mechanism to preclude damage The Ocean Power Delivery wave energy converter Pelamis has articulated sections that stream from an anchor towards the shore Waves passing overhead produce hydraulic pressure in rams between sections This pressure drives hydraulic motors that spin generators, and power is conducted to shore by cable 750 kW produced by a group 150m long and 3.5m diameter
27	16.2.2 Wave Energy: Pelamis
28	16.2.2 Fluid-Driven Wave Turbines Davis Hydraulic Turbines since 1981 Most tests done in Canada 4 kW turbine tested in Gulf Stream Blue Energy of Canada developing two 250 kW turbines for British Columbia Also proposed Brothers Island tidal fence in San Francisco Bay, California 1000 ft long by 80 ft deep to produce 15 – 25 MW Australian Port Kembla (south of Sydney) to produce 500 kW
29	16.2.2 Air-Driven Wave Turbines British invention uses an air-driven Wells turbine with symmetrical blades Incoming waves pressurize air within a heavy concrete box, and trapped air rushes upward through pipe connecting the turbine A Wavegen™, wave-driven, air compressor or oscillating water column (OWC) spins a two-way Wells turbine to produce electricity Wells turbine is spun to starting speed by external electrical power and spins the same direction regardless of air flow direction Energy estimated at 65 megawatts per mile
30	16.2.2 Air-Driven Wave Turbines (Con’t) A floating buoy can compress trapped air similar to a whistle buoy The oscillating water column (OWC) in a long pipe under the buoy will lag behind the buoy motion due to inertia of the water column The compressed air spins a turbine/alternator to generate electricity at $0.09/kWh
31	16.2.2 Hydraulic Pressure Absorbers Large synthetic rubber bags filled with water could be placed offshore where large waves pass overhead Also respond to tides A connecting pipe conducts hydraulic pressure to a positive displacement motor that spins a generator The motor can turn a generator to make electricity that varies sinusoidally with the pressure Rectify to charge batteries or use newer conversion technologies to make 60 hertz output
32	16.3.1 Ocean Thermal Energy Conversion (OTEC)
33	16.3.1 OTEC (continued) French Physicist Jacque D’Arsonval (meter inventor) proposed in 1881 Georges Claude (neon lamp inventor) built Matanzos Bay, Cuba 22 kW OTEC plant in 1930 [Smith, p.94] Keahole Point, Hawaii has the US 50 kW research OTEC barge system OTEC requires some 36 to 40°F temperature difference between the surface and deep waters to extract energy Open-cycle plants vaporize warm water and condense it using the cold sea water, yielding potable water and electricity from turbines-driven alternators Closed-cycle units evaporate ammonia at 78°F to drive a turbine and an alternator
34	16.3.2 OTEC (continued)
35	16.3.3 OTEC (continued)
36	16.3.3 OTEC: Infrastructure
37	16.3.3 OTEC (continued)
38	16.3.3.1 Florida Solar Energy Center & OTEC In the 1977 era, FSEC was involved (Dr. David Block) in the Florida OTEC plans for a Key West station using the barge http://pdf.aiaa.org/preview/1981/PV1981_2563.pdf has a report on the installation
39	16.3.4 OTEC Nemesis: Biofouling
40	16.4.1 Ocean Currents
41	16.4.1 Ocean Currents (continued)
42	16.4.1 Gulf Stream Gyres Can energy extraction stop the Gulf Stream? Some are alarmed due to potential climate change! Will the UK freeze? Note the wandering gyres east of Delmarva
43	16.4.1 Ocean Currents (continued)
44	16.4.2 Current Flow Turbines
45	16.4.3 Ocean Energy Center Florida Atlantic University at Dania has established the $5M Florida Center of Excellence in Ocean Energy Technology to investigate Gulf Stream energy The basic approach is to lower a turbine with a 10-foot diameter, three-bladed rotor several hundred feet into the Gulf Stream and take measurements They estimate that ocean energy could supply 30% of Florida’s electricity needs
46	16.5 Ocean Wind Energy
47	16.5.1 Wind Energy Equations (also applies to water turbines; the density is different) Assume a “tube” of air the diameter, D, of the rotor A = π D²/4 A length, L, of air moves through the turbine in t seconds L = u·t, where u is the wind speed The tube volume is V = A·L = A·u·t Air density, ρ, is 1.225 kg/m³(water density ~1000 kg/m³) Mass, m = ρ·V = ρ·A·u·t, where V is volume Kinetic energy = KE = ½ mu²
48	16.5.1 Wind Energy Equations (continued) Substituting ρ·A·u·t for mass, and A = π D²/4 , KE = ½·π/4·ρ·D²·u³·t Theoretical power, P_t = ½·π/4·ρ·D²·u³·t/t = 0.3927·ρ_a·D²·u³, ρ (rho) is the density, D is the diameter swept by the rotor blades, and u is the speed parallel to the rotor axis Betz Law shows 59.3% of power can be extracted P_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 For example, 59.3%·90%·98%·80% = 42% extraction of theoretical power
49	16.5.2 Wind Energy (continued)
50	16.5.2 Wind Energy: SeaWinds
51	16.5.2 Wind Energy (continued)
52	16.5.2 Wind Energy (continued)
53	16.6 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 aren’t 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
54	16.S Ocean Energy: Summary Offshore winds are unhindered and strong The tidal gravitational forces and thermal storage of the ocean can provide a major energy source Wave action adds to the extractable surface energy, but is less than tidal energy Major ocean currents (like the Gulf Stream) may be exploited to extract energy with strong underwater rotors similar to wind turbines
55	Olin Engineering Complex 4.7 kW Solar PV Roof Array
56	References: Books Boyle, Godfrey. Renewable Energy, Second Edition. Oxford: Oxford University Press, 2004, ISBN 0-19-26178-4. (my preferred text) Brower, Michael. Cool Energy. Cambridge MA: The MIT Press, 1992. 0-262-02349-0, TJ807.9.U6B76, 333.79’4’0973. Duffie, John and William A. Beckman. Solar Engineering of Thermal Processes. NY: John Wiley & Sons, Inc., 920 pp., 1991 Gipe, Paul. Wind Energy for Home & Business. White River Junction, VT: Chelsea Green Pub. Co., 1993. 0-930031-64-4, TJ820.G57, 621.4’5 Patel, Mukund R. Wind and Solar Power Systems. Boca Raton: CRC Press, 1999, 351 pp. ISBN 0-8493-1605-7, TK1541.P38 1999, 621.31’2136 Sørensen, Bent. Renewable Energy, Second Edition. San Diego: Academic Press, 2000, 911 pp. ISBN 0-12-656152-4. Texter, [MIT]
57	References: Websites, etc. http://folk.ntnu.no/hals/nedlasting/lysark/WaveEnergy.ppt#444,81,The Swedish IPS buoy http://www.nrel.gov/otec/ awea-windnet@yahoogroups.com. Wind Energy elist awea-wind-home@yahoogroups.com. Wind energy home powersite elist mailto:energyresources@egroups.com rredc.nrel.gov/wind/pubs/atlas/maps/chap2/2-01m.html PNNL wind energy map of CONUS windenergyexperimenter@yahoogroups.com. Elist for wind energy experimenters www.dieoff.org. Site devoted to the decline of energy and effects upon population www.ferc.gov/ Federal Energy Regulatory Commission www.hawaii.gov/dbedt/ert/otec_hi.html#anchor349152 on OTEC systems telosnet.com/wind/20th.html www.google.com/search?q=%22renewable+energy+course%22 solstice.crest.org/ dataweb.usbr.gov/html/powerplant_selection.html http://rads.tudelft.nl/gulfstream/ http://www.fujitaresearch.com/reports/tidalpower.html http://media.wiley.com/product_data/excerpt/9X/04701070/047010709X.pdf http://www.instructables.com/id/Build-your-own-Savonius-VAWT-Vertical-Axis-Wind-T/
58	In Other News . . . Lockheed Martin and Ocean Power Technologies, Inc. plan to develop utility-scale PowerBuoy systems DOI Sec’y Salazar plans offshore energy strategy for wind, wave, and ocean current Stimulus Act provides EERE with $16.8B, 10 times the 2008 budget Marine Current Turbines Ltd. developing tidal facilities at the Bay of Fundy, Canada, a 1.5MW tidal flow generator News from ON&T, March, 2009