HONOLULU - Honolulu Seawater Air Conditioning LLC (HSWAC) is currently developing a 25,000-ton seawater air conditioning district cooling system for downtown Honolulu. The system is designed to serve buildings in the downtown core.
As a tropical island state, Hawaii has a year-round, relatively uniform need
for air conditioning. Conventional air conditioning systems are energy
intensive and represent 35 to 45 percent of energy use in typical office and
hotel buildings in Hawaii, said the company. Hawaii also has some of the
highest electricity rates and air conditioning costs in the country. And,
Hawaii relies on expensive imported fossil fuels for more than 90 percent of
its energy needs. At the same time, all islands have some shorelines that have
good access to deep, cold seawater used in a seawater air conditioning system.
In operation, a seawater air conditioning system pumps seawater through a
supply pipeline to a cooling station on the shore. The intake pipe is located
at a depth where the water temperature is 39° to 45°F year-round. Heat
exchangers at the cooling station transfer the cold temperatures of the
seawater to a fresh water distribution network. The heat exchangers ensure that
the seawater and fresh water never mix. The warmed seawater is returned to the
sea through a diffuser, while the closed loop, fresh water distribution
network, including pumps, provides chilled water to cool the buildings.
Seawater air conditioning is suitable for coastal developments with a large air
conditioning demand and reasonable access to deep, cold seawater. Notable areas
are southern Kauai, several areas of Oahu, and the southern 60 percent or more
of the Big Island, said HSWAC.
A number of studies have been conducted to evaluate the potential of seawater
air conditioning in Hawaii, and there is an operating system at the Natural
Energy Laboratory of Hawaii Authority (NELHA) at Keahole Point, Hawaii.
According to HSWAC, these studies all show that there is significant potential
for seawater air conditioning in Hawaii. More recent studies show that
combining seawater air conditioning with thermal energy storage and auxiliary
chillers increases the cost effectiveness and applicability of such systems.
The Hawaii State Department of Health, Office of Environmental Quality Control
(OEQC) has published an initial environmental impact statement preparation
notice (EISPN) providing for a 30-day public review and comment period on
HSWAC’s downtown Honolulu project. Any comments that are raised during the
public review and commenting period of the EISPN will be included and addressed
in a subsequent draft environmental impact statement (DEIS).