Deep Ocean Water Resource Development Ocean Thermal Energy Conversion and Open Ocean Mariculture A Seminar Presentation By Clark C. K. Liu, Ph.D., P.E., F.ASCE Professor of Civil and Environmental Engineering University of Hawaii at Manoa

1.Introduction: Deep ocean water (DOW) as a natural resource (a) DOW is Cold Temperature Difference Between Surface and 1000 m depth

(b) DOW is nutrient rich DOW Enhanced Bio-Productivity in Pacific Ocean

Integrated DOW Resources Utilization

The Second Law of Thermodynamics Heat Reservoir, T h Heat Reservoir, T c Heat engine Work, W Heat to engine, Q h Waste heat,Q c 2. Ocean Thermal Energy Conversion

History of OTEC Development 1881 Dr. D’Arsonval proposed to use relatively warm tropical ocean water to vaporize pressurized ammonia through a heat exchanger (evaporator) and then to use the resulting vapor to drive a turbine generator. The cold deep ocean water would then be used to condense the ammonia vapor through another hear exchanger (condenser) Professor Claude conducted experiment with a device at the French Academy of Sciences to demonstrate that electricity could be generated using thermal difference. His subsequent field experiments were failed due to difficulties of installing cold water pipe

Mini-OTEC 1979 Hawaii Mini-OTEC was built on a barge to produce 50 kW of gross power, with a net power output of 18 kW. It is a close-cycle OTEC with ammonia as the working fluid. The cold water pipe of polyethylene is 0.6 m in diameter.

Nauru OTEC 1981 a close-cycle land-based OTEC was built in the island of Nauru by a consortium of Japanese companies. Twenty-two tons per minute of cold deep ocean water and twenty-four tons per minute of warm surface seawater were pumped. A 100 kW gross power was generated.

Hawaii Open-cycle OTEC An open-cycle land-based OTEC was built in Hawaii and was successfully operated During a period of 6 years ( ). It produced up to 255 kW gross power with a corresponding net power of 103 kW. Freshwater of 0.4 liters per second was also produced.

Evaporator Condenser Turbo- generator Warm water in Discharge water to sea Working fluid vapor Working fluid vapor Discharge water to sea Cold Water in Working fluid condensate Working fluid Working fluid pressurizer Closed-Cycle OTEC System

Open-Cycled OTEC System Vacuum chamber flash evaporator Condenser Turbo- generator Non- Condensable gases Discharge water to sea Water vapor (unsaturated) Water vapor (saturated) Discharge water to sea Cold Water in Aeaeration (optional) Non- Condensable gases Warm Sea water in Freshwater

Design Considerations (a). Heat Exchanger Shell-and-tube spray evaporator

Design Considerations (b). Working Fluids

It was estimated that approximately 4 m 3 /s of warm seawater (at 25 0 C) and 2 m 3 /s of cold seawater (at 5 0 C) are needed by a OTEC to produce a 1 MW net electricity. OTEC Size, MW Cold Seawater Flow m 3 /s Pipe dia. m Warm Seawater Flow m 3 /s Pipe dia.m Flow velocity = 2 m/s Design Considerations (c). Cold water pipe

Alternative Cold-Water Pipe Construction

3. Mariculture in Deep Ocean Water Mariculture and Power Generation

FAO Aquaculture Values for 1992 Proceedings of Open Ocean Aquaculture 97, Maui, Hawaii

Benefits of Open Ocean Mariculture Mass production of marine protein. Produce biomass for fuels, Alleviate global warming trends by CO 2 sequestration. Reduce stresses on inshore ecosystems and fish stocks

Pelagic Fishery in Upwelling Region off Northeastern Taiwan Yeh, S., Liu, J., and Ju, D Comparison on pelagic fisheries resources in the vicinity of upwelling cold dome region off Northeastern Taiwan, Proceedings ofIOA97, International OTEC/DOWA Association Findings: The traditional most productive fishing grounds off Northeastern Taiwan are near the upwelled region

Artificial Upwelling as a Solution to the problem of Global Warming Global CO 2 cycle

4. Research and Development on Artificial Upwelling and Mixing A commercially-viable open ocean mariculture industry must be developed based on new technologies of artificial upwelling and mixing (AUMIX) Ocean Ranch

Physical System of a Wave-Driven Artificial Upwelling Device

Simple Analysis of the Motion of an Upwelling Device t 1, valve opens t 2, valve closes

Estimation of Upwelling Flow Rate

Artificial Upwelling Device Deep Ocean Water Plume Artificial Upwelling and Mixing (AUMIX) Buoy Chamber Tail Pipe Waves

Deep Ocean Water Plume Wave Current Near Field Intermediate Field Far Field Equilibrium Depth Initial Dilution

Constant Head Tank Electronic Weight Scale Lower Tank Wave Maker Laboratory Experimental

Experimental Results of DOW Plume Mixing

Entrainment hypotheses in the Kernel Model Mathematical Modeling of DOW Plume Mixing

Case 1: Nomogram by Model Kernel

Formation of a Nutrient-rich DOW Plume in the Open Ocean

Descending Depth of a DOW Plume in ambient Ocean Wave effect on descending depth is not obvious if current velocity is over 0.2m/s.

Ocean Experimental

Wave-Driven Artificial Upwelling

Deep Ocean Water Plume Mixing

Ocean Experiment on OTEC and Open Ocean Mariculture, Toyama Bay, The Sea of Japan,

Ocean Experiments on DOW Enhanced Marine Bio-Productivity by Research Institute for Subtropics, Okinawa, Japan

Adding DOW into Mesocosms

Measured Chlorophyll-a Time Series

Proposed Experimental Investigation on Primary Productivity and CO 2 Balance in a DOW Enriched Water Data logger DOW Surface Water Computer Valve & Sensor Plug Flow Reactor Monitoring and Sampling Automatic monitoring and sampling instruments will be installed to measure salinity, temperature, Chlorophyll-a, dissolved CO 2, bicarbonate (HCO 3 - ), carbonate (CO 3 -2 ), dissolved oxygen, and other relevant parameters.

Study of Bio-Productivity and CO 2 transfer in DOW Enriched Ocean Water Task II. Primary Productivity and CO 2 Balance in a DOW Enriched Water Task I. Artificial Upwelling and DOW Supply CO 2 Interface Transfer Kinetics Open Ocean Mariculture Task III. CO 2 transfer kinetics By carbonate equilibrium Task IV. Primary Productivity and DO diurnal variation

OTEC/DOWA Research and Development in Taiwan 1.From Commercialization of OTEC to Small- scale Demonstration Plants 2. Other DOW-related Activities 3.Pending: Formulation of an Action Plan

US-ROC Workshop on Deep Ocean Water Application and Ocean Resources