Seawater Air Conditioning Research Articles

Exploring global accessibility of deep ocean water for sea water air conditioning (SWAC) process: Identifying feasibility areas depending on temperature source

Sea Water Air Conditioning (SWAC) technology is a highly efficient alternative to conventional air conditioning system using renewable marine energy to provide cooling to buildings. However, its implementation requires access to Deep Ocean Water (DOW) at 4–5 °C, thus SWAC is only viable in coastal regions. Furthermore, one of the major obstacles to its global development is the investment cost that remains high. This cost is strongly linked to the bathymetry of the installation location as it determines the length of the drawing pipeline, which accounts for the largest share of the investment cost. Knowing the temperature and bathymetry profiles will enable the establishment of the financial viability of SWAC technology in a specific location. This paper presents an analysis identifying areas of feasibility on a worldwide scale for standard SWAC implementation first. Then, it explores an alternative design with a higher drawing point for seawater at 12 °C (coupled with a High Temperature District Cooling), which reduces the cost by shortening the drawing pipeline and allows for more locations to be suitable for this technology. Additionally, the impact of the El Niño/Southern Oscillation (ENSO) is also considered since a shallower drawing point makes it more sensitive to temperature variations.

Energy performance assessment of Sea Water Air Conditioning (SWAC) as a solution toward net zero carbon emissions: A case study in French Polynesia

Sea Water Air Conditioning (SWAC) technology uses deep ocean water to cool buildings. It is a non-intermittent renewable thermal energy used directly without any transformation. It may replace other air-conditioning systems powered by electrical energy (mechanical vapor compression thermodynamic cycle) or powered by other renewable energies (solar heating and cooling systems). Despite its theoretical appeal as a solution to help achieve net-zero carbon emissions, and the existence of successful deployments, SWAC technology remains scarce worldwide mainly due to its investment cost (CAPEX). One reason for this failure to scale might be the absence of experimental data detailing energy performance of SWAC systems in real-world, commercial settings. Here is presented the performance of an existing 2.4 MW SWAC system, operated by The Brando resort on the atoll of Tetiaroa in French Polynesia. Under a tropical climate, experimental results show that the Coefficient of Performance (COP) of the SWAC system can reach 20 to 150 depending on the secondary loop length, compared with conventional vapor compression systems that peak at around 5 for the most efficient. To put this in terms of carbon emissions avoided, conventional unitary split systems running in similar hotels on neighboring islands in French Polynesia (COP around 3.5) emit some 860 Tons/year compared to the estimated 225 Tons/year emitted (approximated with the emissions factor of French Polynesia in 2019) operating the Tetiaroa SWAC.

Seawater Air-Conditioning and Ammonia District Cooling: A Solution for Warm Coastal Regions

Seawater Air-Conditioning and Ammonia District Cooling: A Solution for Warm Coastal Regions

Energy Performance Assessment of Sea Water Air Conditioning (Swac) as a Solution Toward Net Zero Carbon Emissions a Case Study in French Polynesia

Energy Performance Assessment of Sea Water Air Conditioning (Swac) as a Solution Toward Net Zero Carbon Emissions a Case Study in French Polynesia

Deep seawater cooling and desalination: Combining seawater air conditioning and desalination

• Demand for cooling and desalination is assessed in coastal cities. • Deep seawater cooling and desalination (DSCD) is described. • Synergies of combining seawater air conditioning and desalination. • Case study in Malé, Maldives, with vast potential for DSCD. • DSCD can supply 49 MW th of cooling and 1 m 3 /s of water simultaneously. In tropical climates, the energy consumed by heating, ventilation and air conditioning can exceed 50% of the total energy consumption of a building. The demand for cooling is rising steadily, driven by global warming and rapidly increasing living standards in developing economies. In addition, there is a rise in water demand due to population increase, life quality, and global warming. Coastal areas with narrow continental shelves are the perfect site for implementing Seawater Air Conditioning (SWAC), a renewable and low CO 2 emission cooling process. This article proposes the combination of SWAC and reverse osmosis (RO) desalination with the objective of providing desalinated cold water for integrated water supply and cooling services. This combination was named Deep Seawater Cooling and Desalination (DSCD). It was found that DSCD can supply 49 MWt of cooling and 1 m 3 /s of water simultaneously with an electricity consumption of 12 MWe. DSCD has several benefits compared to SWAC and RO individually, such as in how the cooling service and water supply are delivered together, reducing distribution costs. A case study was performed in Malé, Maldives. It shows that the technology has substantial potential to contribute to the sustainable development of tropical islands.

Seawater as Renewable Energy in Air Conditioning and Plumbing Systems for Coastal Development

Seawater is deemed as renewable energy and supplemental water source in coastal development. Utilizing seawater resources in air conditioning and plumbing system involves implementation of innovative technology such as seawater air conditioning (SWAC), seawater heat pump (SWHP), landscape irrigation system, potable water and greywater recycling. The research aims to demonstrate seawater usage as water efficiency option to reduce energy consumption, save freshwater and environment. The research had adopted systematic literature review (SLR) method to analyze the application of seawater building air conditioning and plumbing system on current publications and papers, and conclude with summary of benefits and challenges.

High velocity seawater air-conditioning with thermal energy storage and its operation with intermittent renewable energies

The rapid increase in cooling demand for air-conditioning worldwide brings the need for more efficient cooling solutions based on renewable energy. Seawater air-conditioning (SWAC) can provide base-load cooling services in coastal areas utilizing deep cold seawater. This technology is suggested for inter-tropical regions where demand for cooling is high throughout the year, and it has been implemented in islands with short distances from the coast and the deep sea. This paper proposes adjustments to the conventional design of SWAC plants to reduce implementation risks and costs. The approach is named high velocity SWAC and consists of increasing the excavation depth of the seawater pump station up to 20 m below the sea level, compared to 2 to 5 m in conventional SWAC projects. This allows a twofold increase in the speed of inlet pipeline seawater and cooling load of the plant. The cooling load can be expanded twofold with only 55% capital cost and 83% project costs, compared with the costs of a new system. In addition, this article shows that high velocity SWAC plants with thermal energy storage will have an important role supporting the dissemination of intermittent renewable sources of energy in regions where SWAC is a viable cooling alternative.

Estimating the practical potential for deep ocean water extraction in the Caribbean

Deep ocean water (DOW) is a renewable alternative to the many sustainability challenges that the Caribbean faces today. DOW can provide seawater air conditioning (SWAC) for buildings and greenhouses, provide electricity through an ocean thermal energy conversion plant (OTEC), and provide nutrients for aquaculture and cosmetic industries. However, today the implementation of DOW technologies in the Caribbean is inexistent, and studies about DOW potential in the Caribbean are limited. We present a methodology for estimating the practical potential of a city while considering constraints in ocean currents, temperature, and salinity. We applied the methodology to five cities in the Caribbean and found that the average potential is about 50 m3/s per city, enough to supply more than 100% of a city’s demand for air conditioning and 60% of its demand for electricity. We also estimated the monthly availability of DOW resource, with maximum extraction potentials between December to March, and minimum values between August to October. These estimations serve as input for future feasibility and design studies on DOW technologies in the Caribbean. Given the assumptions, the found potential may be underestimated; thus, the results of this study can be considered as a minimum reference value, complementary to the maximum theoretical potential found in previous studies.

Multi-scenario model for optimal design of seawater air-conditioning systems under demand uncertainty

Seawater air conditioning (SWAC) systems use deep seawater as a cooling utility. SWAC systems are receiving increasing attention as an integral component of sustainable cooling units of lodging complexes because of the availability of seawater, the substitution of chemicals refrigerants, low achievable temperature, low environmental impact, and large potential savings in energy consumption compared to conventional air-conditioning systems. The design of these systems depends mainly on the energy demand of each hotel in each month; however, there is uncertainty in this variable, since it depends on the season of the year, being lower in months of low occupancy and higher in months of high tourist occupancy. This paper presents a multi-objective optimization with a probabilistic formulation approach for designing these systems under seasonal energy demand uncertainty. The model seeks to meet the demands of air conditioning in hotels using deep seawater considering technical aspects and seeks to minimize the total annual cost while minimizing emissions of greenhouse gases. The results show the importance of accounting uncertainty in the design of these systems. • a multi-objective multi-scenario stochastic model for the optimal design of SWAC networks is presented • SWAC systems are an environmentally friendly alternative to conventional AC systems • The flexibility in the operation of the system can compensate the uncertainty in the energy demand

Adoption of sea water air conditioning (SWAC) in the Caribbean: Individual vs regional effects

Seawater air conditioning (SWAC) is a sustainable alternative for the Caribbean's energy challenges. Despite their vast potential, current sustainability plans and renewable energy incentives in the Caribbean exclude ocean technologies, and thus, the adoption of SWAC remains limited. A multidimensional scaling analysis was performed to classify the potential market for SWAC into three clusters, and to measure similarities among the Caribbean islands. Such similarities were used to complement a system dynamics model to include the effect of cross-country word-of-mouth on SWAC adoption rates. With the improved model, this study simulated policy incentives to SWAC promotion in five countries and compared the effectiveness of country-level versus regional-level incentives. Results suggest that, by 2030, renewable air conditioning use in the Caribbean could reach 36% if the countries adopt individual policies. This percentage could increase up to 60% if they adopt a regional policy. Results suggest that the regional policies are the most effective to impulse the adoption of SWAC, which in turn contributes to attaining sustainable energy targets. Financing institutions should distribute investment among the interested countries and allocate a higher percentage in the smallest states such as Barbados or Curacao, instead of supporting only big countries such as Jamaica.

Conditions accommodating a dominant stakeholder in the design of renewable air conditioning systems for tourism complexes

Seawater air conditioning systems use cold water from the deep ocean to provide cooling utilities to buildings. Their design, as with other renewable energy systems, involves the participation of multiple stakeholders with different preferences and objectives. A multi-objective strategy based on compromise solutions for reducing the dissatisfaction between multiple participants is presented. The dominant stakeholder is considered to have predominant participation, opinion, and weight in the final decision of the project. The presented decision-making framework allows for the resolution of conflicts and shows the effects of different criteria on the final configuration of the system. This work presents an optimal design model considering, as a case study, a touristic zone in Mexico. The results show significant differences between scenarios where all the stakeholders are considered under a condition of equality and one in which only the dominant stakeholder is considered. This decision-making approach shows flexibility and provides tolerance limits for compromise solutions that still consider the influence of the dominant stakeholder.

Technical potential and cost estimates for seawater air conditioning

In tropical climates, the energy consumed by ventilation and air conditioning can exceed 50% of the total consumption of a building. Demand for cooling is rising steadily, driven mainly by growing incomes in developing economies, and is expected to also increase with climate change. Tropical, coastal areas with narrow continental shelves are good sites for the implementation of Seawater Air Conditioning (SWAC), a renewable and low CO2 emission cooling process. This paper presents the existing SWAC projects around the world and gives details on the technology. Data on ocean temperature profiles, ocean bathymetry and world surface temperature are processed with the intent of estimating the world potential of SWAC. The results present the required distance from coast to reach seawater with a temperature of 5 °C or less. This is combined with the potential demand for air conditioning, taking into account surface air temperature and a set SWAC design for cooling from 30 to 20 °C. The pipeline length, seawater depth and capacity factor are then used to estimate the costs of SWAC projects around the world. It is concluded that the locations with the highest potential for SWAC are intertropical islands and some continental locations.

Understanding the future of Seawater Air Conditioning in the Caribbean: A simulation approach

Seawater Air Conditioning (SWAC) is a sustainable alternative for tropical islands. Despite its potential, adoption has been limited throughout the world. There is a need to understand SWAC adoption potential in the Caribbean and to identify the actions and policies that could favor its diffusion. We develop a system dynamics simulation model for SWAC adoption, and use it to simulate scenarios and incentives for SWAC in Jamaica. We found that SWAC adoption is mainly limited by the threshold capacity necessary for the first installation. To achieve full adoption by 2050, governments and investors should finance 100% of the first pipeline before 2020.

Observations of the Hawaiian Mesopelagic Boundary Community in Daytime and Nighttime Habitats Using Estimated Backscatter

The Hawaiian mesopelagic boundary community is a slope-associated assemblage of micronekton that undergoes diel migrations along the slopes of the islands, residing at greater depths during the day and moving upslope to forage in shallower water at night. The timing of these migrations may be influenced by environmental factors such as moon phase or ambient light. To investigate the movements of this community, we examined echo intensity data from acoustic Doppler current profilers (ADCPs) deployed at shallow and deep sites on the southern slope of Oahu, Hawaii. Diel changes in echo intensity (and therefore in estimated backscatter) were observed and determined to be caused, at least in part, by the horizontal migration of the mesopelagic boundary community. Generalized additive modeling (GAM) was used to assess the impact of environmental factors on the migration timing. Sunset time and lunar illumination were found to be significant factors. Movement speeds of the mesopelagic boundary community were estimated at 1.25–1.99 km h-1 (35–55 cm s-1). The location at which the migrations were observed is the future site of a seawater air conditioning system, which will cause artificial upwelling at our shallow observation site and may cause animal entrainment at the seawater intake near our deep water observation site. This study is the first to observe the diel migration of the mesopelagic boundary community on southern Oahu in both deep and shallow parts of the habitat, and it is also the first to examine migration trends over long time scales, which allows a better assessment of the effects of seasons and lunar illumination on micronekton migrations. Understanding the driving mechanisms of mesopelagic boundary community behavior will increase our ability to assess and manage coastal ecosystems in the face of increasing anthropogenic impacts.

Cool as a (sea) cucumber? Exploring public attitudes toward seawater air conditioning in Hawai‘i

Seawater air conditioning (SWAC) has the potential to reduce the energy demand for air conditioning by 75–90%. This article reports the findings of a mail survey sent to residents of the Hawaiian island of O‘ahu investigating attitudes toward SWAC and opinions of installing a system in Waikīkī. Results show that while only 55% of O‘ahu residents were previously aware of SWAC, 62% supported its development in Waikīkī and just 7% opposed. Of those familiar with the technology, support rose to 69%. However, when compared to eight other low-carbon energy options, SWAC ranked second to last. Concern exists about the potential environmental impacts of SWAC, particularly with regard to reef damage and algae production. Logistic regression analysis shows no significant difference in the likelihood of a person supporting SWAC due to their sex or level of education; although age, political affiliation, and locality do affect the likelihood of support. Those who see tourism as very important to Hawai‘i and think SWAC will benefit the tourism industry are more likely to support, along with those who have a very positive opinion of renewable energy, and those who are familiar with the technology. In contrast, high-income O‘ahu residents are less likely to support SWAC.

English

English

해수냉난방용 판형 열교환기의 최적설계를 위한 수치적 연구

Plate heat exchanger are being applied in the field of OTEC (ocean thermal energy conversion) and SWAC (seawater air conditioning) system. This study is to analyze numerically the heat transfer and pressure drop characteristics by using solid works flow simulation in order to offer optimum design data of plate heat exchanger. Plater heat exchanger proposed in this study is four types. The geometric design parameters of plate heat exchanger are a channel space, a flow orientation, a plate array, the flowrate of working fluid and so on. The main results for numerical analysis of plate heat exchangers are summarized as follows. Heat transfer performance for the channel space of 2.4 mm shows the highest value compared to other spaces. And, the Type 4 plate heat exchanger in Table 2 is the highest performance. From the pressure drop characteristics of plate heat exchanger, the channel space of 3.2 mm shows the lowest value. And Type 1 plate heat exchanger in Table 2 is the lowest pressure drop.

Ocean thermal energy resources in Colombia

Colombia's exclusive location surrounded by the warm tropical waters of the Caribbean Sea and the eastern equatorial Pacific Ocean make it a suitable region for ocean thermal energy conversion (OTEC). These are systems that can produce significant amounts of renewable electricity. From the assessment of the temperature gradient and the bathymetric, environmental and socio-economical characteristics, the maritime area around the island of San Andres (in the northwestern Caribbean Sea) was found to be ideal for an OTEC facility since sea surface temperature varies only slightly during annual and interannual timescales. The thermal difference encountered from the surface to a depth of 1000 m is always around 22°–24 °C and cold waters are available for intake at around 450–750 m, within a short horizontal distance from the coast (less than 2.5 km). At these depths, the 20 °C thermal gradient required for OTEC operations is achieved. Furthermore, winds, waves and surface currents around the island are of relatively weak intensity. Presently, energy sources based entirely on Diesel generators are inducing negative impacts on the sustainable development of the region and on the fragile marine ecosystem. An environmentally friendly 10 MW OTEC facility could be part of future energy and water management solutions for the island. It would cover nearly 50% of total electricity demands and provide important additional advantages such as chilled soil agriculture, aquaculture, freshwater, mariculture and seawater air conditioning.

Ocean Thermal Energy for Air-conditioning: Case Study of a Green Data Center

Solar energy is the source of a temperature difference of about 20°C between the surface and ocean layers 1 km deep. This renewable source of energy occurs at 2.5 km off the coast of Mauritius and can be used for air-conditioning in data centers that operate round the clock. The engineering, economic, and environmental implications of using naturally-available cold seawater for cooling of data centers are examined. The energy requirement of cold seawater air conditioning is 94% lower than that for conventional cooling systems. However, the risk of thermal shock and increased nutrient loading due to effluent disposal should not be overlooked.

Technical and Economic Assessment of Seawater Air Conditioning in Hotels

Cold seawater air-conditioning is a process in which seawater from the deep ocean is pumped to a heat exchanger to process the cooling load of large buildings. The use of cold seawater air conditioning is most competitive in tropical islands, where air conditioning demands are high and the physical distance to cold seawater is at a minimum. This study was therefore initiated to assess the technical and economical aspect of using deep seawater to meet the air conditioning load for hotels located near the sea, having a cooling load of around 1000 tons A/C which is equivalent to 3.5 GW. Three cooling system options were chosen for study namely the Vapor compression chiller system (Option 1), Direct Seawater Air Conditioning (Option 2) and Seawater Air Conditioning using Chiller (Option 3). The conventional vapor compression system was used as a baseline to compare the other options that use cold seawater. The direct cold seawater air conditioning system consisted of a large seawater pipeline and pump to deliver cold seawater to a large heat exchanger that transfers heat directly with the building's chilled water system. The third option was similar to the second one; however, it consisted of a reversible chiller to further cool the fresh water. The technical assessment of the three options consisted of the power consumption of each system to meet the hotel cooling load. Power consumption was found to be 3500 kW, 470 kW and 1870 kW for the three options respectively. The carbon dioxide gas emissions that would be avoided were found to be 13 ton and 7 ton per day by implementing option 2 and 3 respectively compared to option 1. The economic assessment showed that option 2 had a payback period of 6.5 years while the investments costs on option 3 would be recovered in 4 years.