Renewable Energy Technology Assessments - Kauai Island Utility ...

Kaua’i Island Utility Cooperative
Renewable Energy Technology Assessments
3.0 Renewable Energy Technology
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Sea Solar Power International (SSP) has been developing CC-OTEC with funding
from the Abell Foundation. They have proposed a 10 MW plant on Guam, and several
100MW floating plants, but were unsuccessful in obtaining financing. They are now
proposing a CC-OTEC 10 MW plant for the Cayman Islands using propylene as the
working fluid. This appears to be fully funded by the Abell Foundation. This plant is
expected to produce 10 MW of net power and 3 million gallons of desalinated water per
day.
OTEC plants allow a wide range of other services to be derived from the supply
of cold deep ocean water including desalinated water, air conditioning and industrial
cooling, aquaculture, and chilled soil agriculture. Many of the current approaches to
commercializing OTEC utilize the added-value that these services can bring for a small
incremental increase in cost. Since air conditioning and aquaculture can generally only
use a small amount of the water required for the OTEC plant, the main added-value
service is normally desalinated water.
Resource Availability
OTEC requires warm ocean surface water and cold deep ocean water with a
temperature difference exceeding 36ºF. Water cold enough to provide the required
temperature difference is normally only found at depths of over 3,000 ft. Further, surface
water temperature requirements limit development to tropical oceans. Land-based
applications require steep underwater slopes to minimize the length of cold water piping.
The use of off-shore OTEC facilities expands the number of suitable locations for
development.
Cost and Performance Characteristics
In general, OTEC plants must be large to be economic, which has made financing
difficult for developers as there are no large demonstration plants to provide real-world
data on costs. The World Bank determined that a pilot plant of 5MW operating for 5
years would be required before the funding risks associated with a large scale plant
(50MW) could be justified. Therefore, developers are concentrating on pilot scale plants
that are located in niche markets where the price of electricity (and often desalinated
water) is high. Table 3-21 presents the estimated performance and costs for an on-shore
and off-shore CC-OTEC facility. There is a broad range for the cost estimates, as there
has not been a large-scale facility built to test the cost estimates.
21 March 2005 3-49 Black & Veatch