Seawater Air Conditioning

Transcription

1 Seawater Air Conditioning Hezi Gildor The Institute of Earth Sciences The Hebrew University of Jerusalem, Israel Acknowledgement: Yakov Nazichovski, Yossi Ashkenazy, Hezi Yizhak, Rafael Aharoni

2 Motivation Conventional air conditioning in Eilat consumes up to 40% of the total electricity use during the summer. IRENA report, 2014

3 Motivation Conventional air conditioning in Eilat consumes up to 40% of the total electricity use during the summer. Using seawater to chill a conventional AC system condenser can save up to 30% of the electricity used for AC in public buildings, depending on the seawater temperature. SWAC is restricted due to the concerns from thermal and chemical pollution. We aim to conduct an analysis of the economic viability of SWAC systems and estimate the thermal pollution.

4 Outline Introduction to SWAC; variants of SWAC. Environmental benefits and challenges. Design of SWAC systems. Preliminary analysis of feasibility for Eilat. Conclusions.

5 The technology goes by many different names basically same principle SWAC - Seawater Air Conditioning Deep Lake Water Cooling Lake Source Cooling Seawater District Cooling Water source heat pump. Makai Ocean Engineering, Inc

6 Conventional air-conditioning system A simple diagram of a heat pump's vapor-compression refrigeration cycle: 1) condenser, 2) expansion valve, 3) evaporator, 4) compressor Wikipedia A/C condensers use large amounts of electricity to compress refrigerant (~80%)

7 Conventional air-conditioning system Makai Ocean Engineering, Inc

8 Direct water cooling system Cold water is pumped to a heat exchanger, and used to chill fresh water. Without the use of heat pump. Water temperature up to 13 O C (some claims 18 O C). The main components of this basic seawater air conditioning system: (1) seawater supply pipe; (2) the pump station; (3) the heat exchanger (cooling station); (4) the chilled water distribution system; and (5) the effluent pipe. Makai Ocean Engineering, Inc

9 Seawater heat pump systems When it is too costly or impractical to supply seawater at the necessary low temperatures. Use auxiliary chillers to supplement the cooling provided by the seawater exposure. Can be used for both cooling and heating. Water provides a good heat exchange medium, as it is generally cooler than ambient air when cooling is needed, and warmer than ambient air when heating is needed.

10 Environmental benefits and impacts Reductions in electricity consumption > it reduces air pollution and greenhouse gas emission. Secondary applications for the used seawater: Aquaculture Desalination Spa In direct systems, no hazardous refrigerants. Solution available 24/7. Thermal pollution; thermal shock. Nutrient load if we use deep and relatively cold (and nutrient-rich) seawater. Suction of marine organisms into the pipes.

11 Systems around the world Toronto: 3,200,000 m 2 (46 buildings), pipe length 5000 m, 4.4 m 3 /s, T in =4 O c, T out =12 O C. Cornel: pipe length 3200 m, 2.2 m 3 /s, T in =4 O C, T out =14 O C. Hawaii: pipe length 7600 m, 2.02 m 3 /s, T in =11.7 O C, T out =18 O C.

12 Design of a SWAC system Data collection: Meteorological data (temperature, relative humidity, daily range, wind speed). Ocean data: bathymetry, temperature depth profile, current, tides, nutrients. Economical analysis: Distance to cold water. Local cost of electricity. Access to fuel. Total A/C demands. Optimizing the flow rate of sea water and chilled water. Pipes and pump station planning. Distribution system.

13 Bathymetry Eilat - characteristics

14 Eilat - characteristics Bathymetry Hydrographic characteristics: surface water vs. 200 m water St. A Biton and Gildor, 2011 Black observations (taken from NMP) Red Model

15 Eilat - characteristics Bathymetry Hydrographic characteristics: surface water vs. 200 m water

16 Eilat - characteristics Bathymetry Hydrographic characteristics Meteorological characteristics

17 Eilat - characteristics Bathymetry Hydrographic characteristics Meteorological characteristics Hotels and other consumers 48 hotels, additional 2000 rooms are planned Close to the sea Sea is relatively calm

18 U-Suits (formerly Meridian) Use ground water from 135 m, at temperature of O C Pumping flux is about 170 m 3 /h (permit allows a maximum of 200 m 3 /h) Reduces ~15% of the total electricity consumption compared to conventional AC systems

19 Conclusions SWAC is not technically complex. Systems exist around the world (Toronto, Halifax, Cornel, Bora Bora, Hawaii, ). Has the potential to save a significant amount of electricity in Eilat. Electricity is required only to run the pumps (~20%). The costs are primarily related to the initial capital expenditure. This, in turn, is related to the distance to cold water, to air and sea temperature, required A/C load, etc Auxiliary chillers will be needed. The effect of thermal pollution has yet to be studied. Various scenarios should be explored. Thank you!