Seawater air conditioning for economical district cooling in the Caribbean

Makai Ocean Engineering has completed a feasibility study of a district cooling system that uses deep cold seawater, known as seawater air conditioning (SWAC), which would be sited in the Caribbean. The study evaluated eight sites for SWAC and includes conceptual designs and cost estimates at the two most economically attractive locations. The results suggest that SWAC development is likely to be economically attractive in these two locations. Makai Ocean Engineering is a member of the International District Energy Association.

The study, which was commissioned by CAF —Development Bank of Latin America with co-financing from the Agence Française de Développement (AFD), used Makai’s recently upgraded Makai Economic, Thermal, and Hydraulic Optimization and Design, or METHOD™ modeling software (see illustration).

This screenshot (click twice for larger size) shows the Makai METHOD™ software being used to design another SWAC district cooling system in Mauritius. Once a layout is defined by the user, the software is used to configure, fine-tune and optimize the performance of system components (deep seawater pipes, chilled freshwater network, etc.) and operations (pumping power, maintenance, etc.) to produce a system design that would realize minimum cost of cooling.

Makai presented early results of the study at the first Caribbean deep seawater cooling conference, in Santo Domingo in November 2014, which was organized by CAF. A newly released report summarizing the findings is available from CAF upon request (see contact information below).

Makai analyzed eight locations in the Caribbean for SWAC development, and then down-selected to two sites considered to be most promising: Montego Bay in Jamaica, and Puerto Plata in the Dominican Republic.

Hotels and resorts in this region are large consumers of electrical energy, and conventional air conditioning (A/C) systems account for around 40% of the total energy consumption in such buildings. Energy costs can be very high, especially in tropical and island locations, which creates an incentive to develop lower-cost district cooling systems.

Seawater air conditioning (SWAC) is a district cooling technology that uses deep cold seawater for cooling that can be as cold as 5°C or 41°F, even in the tropics. SWAC replaces the chillers used in conventional A/C systems. Instead, cold ocean water is simply pumped through heat exchangers, which transfer the cold temperature to water in a district cooling distribution piping system that circulates through the customer buildings, dramatically reducing the electrical consumption and costs of cooling. The benefits of SWAC include:

  • Large energy savings: approaching 90% compared to conventional A/C.
  • Low, stable operating costs: almost entirely independent of volatile energy prices.
  • Proven technology: deep seawater systems have operated for over 28 years continuously.
  • Environmentally friendly: reduced greenhouse gas emissions, fuel, and water consumption.
  • Secondary uses: cold, nutrient-rich seawater is available for other applications.

SWAC systems are large renewable energy projects with capital costs, depending on project scope,  that can be in excess of $50 million USD. Makai uses its METHOD software to compare the relative economic value of district cooling systems such as SWAC versus a conventional A/C system on the basis of “levelized cost of cooling.”

METHOD has been continuously developed over 25 years, and recently  underwent a major overhaul with the help of a U.S. Navy research and development grant. Notably, the cost algorithms were upgraded and now account for 160 various costs applied across a dozen of the key construction steps for district cooling systems.

The software addresses all the major capital and operational costs for both systems and the complex interplay between the sub-system designs and operational costs. This enables an “apples-to-apples” economic comparison of district cooling versus an equivalent conventional A/C system. Other financial metrics, such as payback period and rate of return of the district cooling system, are also computed.

METHOD consists of two main components: an engineering and an economic model. The engineering model considers the physical layout, chillers, pump stations, heat exchangers, thermal storage, customer loads, proximity to cooling source, pipe sizes, lengths, flow rates, and power requirements. The economic model considers financial aspects such as cost of electricity, financing, CAPEX, and OPEX.

The economic component of the model is based on the Electric Power Research Institute’s Technical Assessment Guide (TAG), which is an economic analysis method of fairly comparing two alternative energy systems with different capital and operating costs using what is called a “levelized” or “annualized” cost of cooling.

The software is particularly useful for providing quick and cost-effective “what if” analyses to help the developer decide between possible design variations early in the project, such as evaluating whether or not to add a nearby A/C customer to the network. Users can instantly see the effect on levelized cost due to a change in the network. In the case of  SWAC systems, METHOD includes accurate costs for the offshore seawater pipes that are derived from real construction projects – this authentic cost data enables the software to calculate accurate project cost, and is something only a firm with significant offshore pipeline construction experience can offer.

ABOUT CAF: CAF—Development Bank of Latin America—is a regional multilateral development agency that promotes a model of sustainable development in Latin America and the Caribbean. CAF has co-financed these studies with the Agence Française de Développement (AFD), a financial institution and the main implementing agency for France’s official development assistance to developing countries and overseas territories. To request a copy of the report, please contact CAF: energia@caf.com

ABOUT MAKAI: Makai Ocean Engineering, Inc. is an innovative ocean engineering and design firm based in Hawaii, USA since 1973. Makai’s expertise includes submarine cable software and services, marine pipelines, Seawater Air Conditioning (SWAC), Ocean Thermal Energy Conversion (OTEC), underwater vehicles, and general marine engineering and R&D. Makai is a design engineering firm that supports project developers. Please visit www.makai.com.

Contact:
Duke J. Hartman, P.E., Vice President, Business Development;
+1 (808) 259-8871; Duke.Hartman@makai.com
Makai Ocean Engineering, Inc.; www.makai.com
Makai Research Pier
41-305 Kalanianaole Hwy
Waimanalo, Hawaii 96795 USA

 

 

About IDEA Industry News

EDITOR: Leonard Phillips, IDEA Director of Business Development, International District Energy Association (IDEA), a nonprofit association founded in 1909. len.idea@districtenergy.org; +1 508-366-9339.
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