About District Cooling >> FAQ
Frequently Asked Questions and Answers:
Q: What is the temperature of the chilled water that district cooling will provide?
A: Chilled water will be delivered at a constant temperature of 44°F, 24 hours a day, 7 days a week.
Q: If seawater is used in the cooling system of my building, will that cause corrosion problems?
A: Definitely not! No seawater will be used in buildings. Seawater is only used to cool the closed-loop freshwater system. The seawater is then returned to the ocean in an environmentally safe manner. A corrosion-resistant heat exchanger will separate seawater from chilled water. The seawater and freshwater never mix. The chilled water provided to buildings is treated potable water, similar to that currently used in existing building systems.
Q: What experience does Honolulu Seawater Air Conditioning have with district cooling?
A: Our personnel have direct experience in developing Scandinavian and European projects, including Europe's largest seawater air conditioning project in Stockholm, Sweden. The Stockholm system includes approximately 80,000 tons of air conditioning load and continues to expand. Honolulu Seawater Air Conditioning's personnel recently undertook the responsibility to handle everything ranging from the preliminary design, to construction and complete market concept of two Dutch systems, both located in Amsterdam with an aggregate capacity of more than 35,000 tons of cooling.
Honolulu Seawater Air Conditioning’s district cooling deep water engineer, Makai Ocean Engineering, undertook the deep water pipe design for the Toronto, Canada, and Cornell University systems. Makai Ocean Engineering was also the design engineer for the Natural Energy Laboratory of Hawaii Authority’s (NELHA) seawater pipes, located in Kona on the Big Island, that were successfully initiated over 20 years ago. The seawater pipes have since then been expanded and extended.
Q: How much will it cost to connect my building to the district cooling system?
A: The cost varies and is dependent on the particular building’s existing chilled water distribution system. Some building chillers are located in the basement, while other buildings may have their chillers on the roof. Additionally buildings taller than 275 feet will require a heat exchanger to physically separate the building’s system from the Honolulu Seawater Air Conditioning system. Buildings less than 280 ft tall can directly connect their system to Honolulu Seawater Air Conditioning’s fresh chilled water.
Honolulu Seawater Air Conditioning will work with each building to aid in the design of the connection to the district system, ensuring that these costs are clearly identified and minimized. The Hawaii Energy (HE) rebate program will cover a substantial amount of these interconnection costs.
Q: How will we be billed?
A: Your monthly bill will consist of a capacity charge and an operating charge, and is billed in twelve monthly installments. Your monthly capacity charge is determined by multiplying your building's capacity, in tons, by the capacity charge rate ($/ton/month). The capacity charge rate is a fixed monthly rate determined before the start of service. The operating charge is determined by multiplying your building’s monthly actual measured energy usage, in ton hours, by the operating charge rate ($/ton-hour). The operating charge rate consists of 1) a fixed rate also determined before the start of service, and 2) a small portion based on the monthly Hawaiian Electric Company current rates.
Q: How reliable is a Seawater Air Conditioning system?
A: Reliability is very important to Honolulu Seawater Air Conditioning. District cooling systems are more reliable than individual building cooling systems. The Honolulu Seawater Air Conditioning central plant has been designed with multiple points of redundancy, including dual electrical service feeds, and a back-up diesel generator to provide uninterrupted service in the case of a power outage. With respect to the chilled water distribution system, the pipes are buried and experience infrequent problems. Current district energy systems around the world are operating today with a high 99% reliability measured over decades of service.
Q: Do we need to maintain our existing chillers and cooling towers as a backup to district cooling?
A: No. You will continue to use your current system during district cooling system construction, and then changeover to district cooling once construction is complete. After the changeover, keeping your existing system is no longer needed as Honolulu Seawater Air Conditioning will provide 24/7 cooling to the property for decades to come. The removal of existing systems will free up space that can be used for other revenue generating purposes (such as parking spaces, in-building storage, etc). Just imagine a new roof top garden where your old cooling towers once took up space.
Q: What is the "down time" associated with interconnection to a district cooling system?
A: The associated down time is minimal. The final interconnection can be done very quickly and if necessary, after hours.