日本財団 図書館

Gerard P. Pereira
Energies Naturelles (Energinat S.A.)
Port-au-Prince, HAITI
The Caribbean island Republic of Haiti is a country blessed with cold (4-6℃) deep ocean water (DOW) in close proximity to its entire coast. The Common Heritage Corporation (CHC) has been developing economic and environmentally sustainable, self-sufficient community habitat systems at the Natural Energy Laboratory of Hawaii Authority (NELHA) for more than a decade. A demonstration DOW system with pipelines, pumps and reservoirs to access the cold resource is now in operation which fully demonstrates the economic and environmental sustainability of such systems even for nations that are virtually devoid of capital, trained manpower and terrestrial resources. The systems do depend on the proximity of cold deep ocean water and high solar insolation.
Each DOW system has five potential profit centers: (1) generation of electricity with Ocean Thermal Energy Conversion (OTEC) and Thermal Electric Generator (TEG) systems; (2) air conditioning and industrial cooling; (3) fresh water production; (4) cold water agriculture; and (5) marine aquaculture. Two types of DOW systems can be designed to serve many purposes: Type 1 is a CHC basic system to provide an economically and environmentally sustainable habitat on a tropical coastal desert, while Type 2 is a system designed to focus on providing high market value recreational experiences, e.g. hotels, resorts, cold thalassotherapy and sports facilities in these tropical coastal desert locations.
The Haitian corporation, Energies Naturelles (Energinat S.A.), and CHC have negotiated a joint venture agreement for the purpose of establishing along the coast of Haiti a complete system of five DOW sites linked by sea transportation and submarine fiber optic telecommunications. Each site will be provided with a Type 1 or a Type 2 DOW system or a combination of the two. This paper describes the innovative technologies employed in the two types of DOW systems and how such ocean technologies can create paradise along much of the coastline of Haiti.
When U.S. Senator Mike DeWine returned from his ninth trip to Haiti in January 2002, he reported in an article posted in the Miami Herald Web site on the 17th of March 2002 that the country - once a lush, tropical sanctuary - was now a "paradise lost" where he witnessed "devastation, destitution and desperation".
The Republic of Haiti is the leeward half of the trade wind Caribbean island of Hispaniola which it shares with the Dominican Republic and which the Windward Passage separates from Cuba itself located only 90 miles from the Florida Keys. Because of the trade winds, the coastal regions of the country are, for the most part, dry and barren, so that its topography is characterized mainly by coastal deserts and mountains.
Moreover, because peasants, of necessity, have stripped the land of its tree cover to produce charcoal (the country's primary fuel), today the thick forest that once blanketed the nation covers only 5% of the land area, 95% being deforested (Cobb, 1987). Once one of the world's most productive agricultural regions, agriculture in Haiti is now limited to scattered patches, being marginal or nonexistent in the remainder of the land. Yet Haiti is an essentially agricultural country with very few terrestrial resources. Does this mean that it is a hopeless case with no signs for optimism? Is there any hope that some day it will become in Milton's words a "paradise regained"?
This paper describes how a complete system utilizing innovative deep ocean water technologies can revitalize Haiti by creating paradise in at least five promising geographic sites identified along the coast of the country.
Fortuitously, Haiti is blessed with deep ocean water in close proximity to its entire coast. This is evident in a conventional map of Haiti on which the 1,000-meter isobath has been superimposed. Even its largest offshore island. Gonave Island, is surrounded by deep seawater. Thus, Haiti, by virtue of its land-sea configuration and its 200-nautical mile exclusive economic zone (EEZ), is the most favored nation in the Caribbean for access to deep ocean water.
In maps revealing the difference in temperature between the surface water and water at a depth of 1,000 meters in the world's oceans, this difference is more than 20℃ in a band from latitudes of about 25°south and 32°north of the Equator extending from east to west (Penney and Daniel, 1988). Haiti is conveniently located at latitudes of 18°to 20°north of the Equator where it can take advantage of the earth's natural ocean thermal energy conversion system, which distributes cold deep ocean water to the tropical regions. Indeed, the country occupies a region where the temperature difference between the warm tropical surface seawater and the cold arctic or antarctic water at a depth of 1,000 meters is 22-24℃, a difference that can be exploited in vanous ways.
The Common Heritage Corporation (CHC) of Hawaii is a leader in the development and demonstration of new technologies for use of the Earth's most abundant and useful resource - deep ocean water (DOW). In addition to being cold, DOW is rich in dissolved inorganic nutrients (nitrates, phosphates and silicates) and free of surface pathogens. It is a renewable, abundant and inexhaustible resource that can be used continuously and in a non-polluting fashion. This virtually unlimited resource is also inexpensive. A simple calculation shows that, while it costs US$0.10 to pump 1.000 gallons of DOW, it would cost US$3.00 to refrigerate the same volume of water. In the Kochi Prefecture of Japan, local residents have been encouraged to find commercial applications for pumped up deep seawater; one of the applications they have come up with is bottling the pure, nutrient rich seawater after desalinization (Hisatake, 1997). One 750-ml bottle of this pure water sells for US$10.00. No wonder Dr. John P. Craven, the CHC founder and Chief Scientist enjoys repeating that deep ocean water as "CLEAN, COOL, CASH".
The Natural Energy Laboratory of Hawaii Authority (NELHA), located at Keahole Point on the Big Island of Hawaii, operates a variety of polyethylene pipelines and pumping stations which access seawater from depths of 17 meters with a temperature of 26°-29℃ and 700 meters with a temperature of 5℃ (Daniel, 1994). At its Demonstration Site at the NELHA, which is a functional living habitat, the CHC has developed DOW technologies that encompass a number of revolutionary methods and applications. These technologies constitute the Deep Ocean Water Energy Recovery (DOWER) system that has three major components: (1) the Energy Utilization Subsystem, (2) the Cold Utilization Subsystem, and (3) the Nutrient Utilization Subsystem. As the water passes through each linked subsystem, it gradually warms before it is discharged into an injection well or wetland/park where it reaches ambient surface ocean temperature for final discharge. This paper will focus on how the use of DOW, either alone or in combination with warm surface seawater, in each of these subsystems can transform many of the barren coastal deserts of Haiti into oases of prosperity and plenty.
Energy Utilization Subsystem - OTEC and TEG Technology
Ocean Thermal Energy Conversion (OTEC) is a process which utilizes the temperature difference between warm surface seawater and cold deep ocean water to drive turbines to generate electricity. The OTEC process requires a temperature difference of at least 20℃elsius. This is achieved by using concentrated solar energy that has been absorbed by warm 24°to 29℃ tropical surface seawater in combination with cold 6℃ seawater pumped from a depth of at least 600 meters. Since the temperature of both the tropical surface seawater and the cold deep ocean water stays fairly constant daily and throughout the year, the 20℃ temperature difference is always available both day and night and from season to season.
Basically, there are two different OTEC systems for the extraction of thermal energy from the oceans to generate electricity: the open-cycle system and the closed-cycle system. A summary of this technology is given by Penney and Daniel (1988).
Georges Claude, a French scientist who also invented the neon sign, first designed an open-cycle OTEC system, which he tested at Matanzas Bay in northern Cuba in 1930. Open Cycle OTEC exploits the scientific principle that water boils at low temperature in a vacuum. In this system, warm surface seawater (about 25℃) is pumped into a vacuum chamber. The low pressure (1,400 pascals) of the chamber causes the seawater to boil and partially vaporize at that low temperature. The resulting low-pressure steam turns a turbine that drives an electrical generator. After it has passed through the turbine, the steam is then condensed either by "direct contact" with cold seawater or by passing it over a heat exchanger through which cold ocean water is pumped, thereby providing a cold surface to reliquefy the steam. The resultant condensate is a bonus byproduct - desalinated water that has the purity of distilled water and a crisp taste and can therefore be used for drinking and irrigation. A 250 kW experimental open-cycle plant was built at NELHA in the early 1990s.
Jacques-Arsne d'Arsonval, a French engineer, first proposed the concept of a closed-cycle OTEC system in 1881. In the closed-cycle system, warm surface seawater is pumped into a heat exchanger (the evaporator) containing a low-boiling point "working" fluid such as ammonia. Heat transferred from the warm surface water via the heat exchanger vaporizes the working fluid. The expanding vapor turns a turbine driving an electrical generator. Cold deep ocean water pumped to a second heat exchanger (the condenser) provides a cold surface to reliquefy the ammonia vapor. The fluid is then returned to the first heat exchanger. It is proposed that a hybrid OTEC plant be used for desalinated water production; the hybrid plant would include a closed cycle component for electricity generation and a second stage, consisting of a separate vacuum "flash" evaporator and a surface condenser, for fresh water production.
It is estimated that a 1 MW hybrid cycle plant can produce one million gallons of fresh water per day (4,000 m3/day), while a 50 MW plant can produce as much as 16 million gallons of water per day (62,000 m3/day). That is sufficient to support a community of approximately 300,000 people in the developing world (Vega, 1992). The first OTEC plant to yield more electrical power than it consumed was "Mini-OTEC", a closed-cycle system mounted on a barge offshore of NELHA. One megawatt closed-cycle plants are under construction at NELHA and on an offshore platform in India. However, an OTEC generating plant is capital-intensive to construct and will make economic sense only if the costs of fossil fuels continue to rise and are passed on to the customers of utilities that generate their power from either diesel or oil-fired conventional generating plants. Ocean thermal energy power generation is expected to be very competitive as an alternative energy source to anticipated mean conventional utility costs as much as US$0.15/kWh or more.
Another promising and competitive electrical energy production system using DOW is the Thermal Electric Generator (TEG) developed by Dr. Maxwell Goldberger, which has no moving parts, creates no pollution discharge and is currently ready for commercial application. Basically, the TEG system generates an electrical potential by using the thermo-electric potential between dissimilar metals maintained at different temperatures. A prototype TEG utilizing solar parabolic mirrors as the heat source and DOW as the cold source was constructed at the CHC Demonstration Site. The TEG produces an effective temperature difference of 300℃ with an electrical output of 1 kilowatt. To maintain electrical output during non-solar hours, a small reservoir of oil, heated by solar mirrors, is plumbed in the system as a heat sink. This system, which is estimated to produce electricity at a cost of US$0.15/kWh, can be expanded to generate 1 megawatt.