Luis A Vega Ph DPh.D. - CRRC · 2013. 10. 22. · Luis A. Vega, Ph DPh.D. Hawai’i National Marine Renewable Energy Center Ha ai’iHawai’i Nat ralNatural Energy Instit teInstitute

OTEC Environmental Impact:Historical PerspectiveHistorical Perspective

Luis A Vega Ph DLuis A. Vega, Ph.D.

Hawai’i National Marine Renewable Energy Center

Ha ai’i Nat ral Ener Instit teHawai’i Natural Energy Institute

University of Hawai’i

1OTEC Potential Environmental Impact

HINMREC‐HNEI‐UH

MiniOTECMiniOTEC (1979)

50 kW CC OTEC50 kW CC-OTEC

210 kW OC-OTEC Experimental Plant

(Vega: 1993-1998)

Desalinated WaterWater

Production(Vega:’94 ’98)(Vega: 94- 98)

50 kW CC-OTEC (NH3) Test Apparatus

(Vega: 1999)

OTEC Potential Environmental Impact HINMREC‐HNEI‐UH

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Conclusion: Major Issuej

• Utilizing ocean water drawn from 1,000 m depths is the only activity that differentiates OTEC from well established regulated industrial activities;

• Major Question: What would be the effect of the OTEC• Major Question: What would be the effect of the OTEC water returned below the photic zone?

• The only way to evaluate this major OTEC differentiator is to obtain field data with a pilot/demonstration/pre‐commercial plant sized at 5 to 10 MW;

• Firstly NOAA/DOE must concentrate in developing the• Firstly, NOAA/DOE must concentrate in developing the monitoring protocol for evaluating the environmental impact of OTEC operations before embarking into considering all potential OTEC designs.considering all potential OTEC designs.


HINMREC‐HNEI‐UH

Demonstration Plant (OTEC Act)Demonstration Plant (OTEC Act)

“a test platform which will not operate as ana test platform which will not operate as an OTEC facility or plantship after conclusion of the testing period”the testing period .

A EIS ld b i d if “ h hAn EIS could be required if “there are other permits to be obtained that are considered a

j f d l i ”major federal action”.


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Conclusion: EIS a MUST• An EIS and related permits et al will have to be obtained/secured;obtained/secured;

• The 1981 Baseline EIS along with References 2 and 3 ( t ) need to be updated however2 and 3 (next page) need to be updated, however, Table‐of‐Contents are complete;

• Artificial Upwelling: There is a misconception• Artificial Upwelling: There is a misconception that OTEC will biostimulate the photic zone but OTEC designs should not provide a g p“sustainable flow of relatively nutrient rich deep water over a wide ocean swath and within the photic zone”and within the photic zone .


HINMREC‐HNEI‐UH

References(1)NOAA July 1981, Final EIS for Commercial OTEC Licensing;Licensing;

(2)NOAA Technical Report NMFS 40, June 1986, Myers et al The Potential Impact of Ocean Thermal Energy p f gyConversion (OTEC) on Fisheries

… Due to the lack of a suitable precedent, however, there will remain some level of uncertainty regarding these initial conclusions until a pilot plant operation can be monitored for some period ofregarding these initial conclusions until a pilot plant operation can be monitored for some period of time…

(3)NOAA Technical Memorandum, John Harrison, February 1987 The 40 MW OTEC Plant at KaheFebruary 1987, The 40 MW, OTEC Plant at Kahe Point, Oahu, Hawaii: A Case Study of Potential Biological Impacts [NB uses marine causeway]


HINMREC‐HNEI‐UH

Phytoplankton Pigment Concentration

Euphotic Zone: Tropical OceansEuphotic Zone: Tropical Oceans

• The euphotic zone: layer in which there isThe euphotic zone: layer in which there is sufficient light for photosynthesis;

• Conser ati e Definition 1 % light• Conservative Definition: 1 % light‐penetration depth (e.g., 120 m in Hawaii);

P ti l D fi iti bi l i l ti it• Practical Definition: biological activity requires radiation levels of at least 10 % of the sea surface value (e.g., 60 m in Hawaii);the sea surface value (e.g., 60 m in Hawaii);

• Is 1990’s “Practical Definition” valid in 2010?


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2010?

OTEC Return WaterOTEC Return Water

• Mixed seawater returned at 60 m depth→• Mixed seawater returned at 60 m depth →dilution coefficient of 4 (i.e., 1 part OTEC effluent is mixed with 3 parts of the ambient seawater)→equilibrium (neutral buoyancy) depths below the photic zone;

• Marine food web should be minimally affected and sea surface temperature panomalies should not be induced.


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ConstructionConstruction

OTEC Construction phase:

‐ similar to construction of power plants; shipbuilding; and offshore platforms;shipbuilding; and, offshore platforms;


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OperationsOperations

U i OTEC i h f• Unique to OTEC is the movement of seawater streams and the effect of passing such streams through the componentssuch streams through the components before returning them to the ocean;

• Losses of plankton, fish eggs and larvae, as well as juvenile fish, due to impingement and entrainment ma red ce fishand entrainment may reduce fish populations (site and flow dependent).


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• CC‐OTEC handling of hazardous substances is limited to the working fluid (NH3) and the g ( 3)biocide (Cl2, evaporator biofouling);

• None for OC‐OTEC


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• Use of Cl2 and NH3 similar to other humanUse of Cl2 and NH3 similar to other human activities;

• Cl2 biocide for OTEC Evaporator is < 5% of EPA Limit;Limit;

• Allowable working fluid and biocide emissions from OTEC will difficult to detect.


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CO OutgassingCO2 Outgassing

• CO2 out‐gassing from the seawater used for the operation of an OC‐OTEC plant is < 0.5% the amount released by fuel oil plants;

h l l h f• The value is even lower in the case of a CC‐OTEC plant.


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Environmental ImpactEnvironmental Impact

• OTEC can be an environmentally benignOTEC can be an environmentally benign alternative for the production of electricity and desalinated water in tropical islandsand desalinated water in tropical islands

• Potentially detrimental effects can bePotentially detrimental effects can be mitigated by proper design


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1990’s Major Question:1990 s Major Question:

Can OTEC have an impact on the penvironment below the photic zone and, therefore, long‐term significance in the , g gmarine environment?


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Annex Eddies & Internal WavesAnnex: Eddies & Internal Waves

Power Output as a Function of Cold Water Temperature

6.20 258

6.10

6.15

ure

(670

m),

255

256

257

ower

Out

put,

6.00

6.05

ter

Tempe

ratu

deg

C

253

254

255

TEC

Gros

s Po

kW

5.90

5.95

32 35 38 41 44 47 50 53 56 59 02 05 08 11 14 17

Seaw

at

251

252 OC-

OT

14:32

14:35

14:38 14:41

14:44

14:47

14:50

14:53

14:56

14:59

15:02

15:05

15:08

15:11

15:14

15:17

Time (September 8, 1993)

1‐minute avrg./1‐sec samples : 3,500m; P 60 minutes; H 50 m

OC-OTEC Power Output as a Function of Warm Water Temperature

27.50 235.0

26.50

27.00

ure

(20

m),

215.0

220.0

225.0

230.0

tput

, kW

26.00

26.50

ter

Tem

pera

tde

g C

200.0

205.0

210.0

215.0

oss

Powe

r O

ut

25.00

25.50

0 9 8 7 6 5 4 3 2 51 0 9 8 7 6 5 4 3 2 21 0 9 8 7

Sawa

185.0

190.0

195.0 Gro

13:3013:3913:4813:5714:0614:1514:2414:3314:4214:5115:0015:0915:1815:2715:3615:4515:5416:0316:12 16:2116:3016:3916:4816:57

Time (July 21, 1993)

Ocean Gyre shed from Alenuihaha Channel between Maui and Hawaii

A 2008 T Diff i lAugust 2008 Temp. Differential


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Documents

Luis A Vega Ph DPh.D. - CRRC · 2013. 10. 22. · Luis A. Vega, Ph DPh.D. Hawai’i National Marine Renewable Energy Center Ha ai’iHawai’i Nat ralNatural Energy Instit teInstitute