Deep Lake Water Cooling

A.CHIDAMBARAM107CH030

CHEMICAL ENGINEERING

Title

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`INTRODUCTION`

A method to provide air conditioning to buildings by taking advantage of an available water source(usually deep cold water from a lake or ocean).

Deep lake water air conditioning is technically and economically feasible and it can be used for Resorts, Residential complexes, Commercial Buildings or other Institutions that have a access to a large quantity of cold water.

There are currently five institutions that utilize this technology and two projects are in progress.

1986: Halifax, Nova Scotia 1986: Nelha, Hawaii 1995: City of Stockholm, Sweden 2000: Cornell University 2003: City of Toronto 2007: Intercontinental Bora Bora In progress: Market street and City of

Honolulu In progress: Kingdom of Bahrain

The AC of Tomorrow : Tapping Deep water for cooling

Conventional Air Conditioners

Conventional air conditioning is expensive to operate due to large electrical power requirements. Cooling is done using a simple refrigeration cycle. The process uses evaporative cooling of a gas to transfer heat.

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Simple illustration of the process :

1. An AC powered compressor compresses gas resulting in the generation of heat.

2. The gas (shown as red in the figure) runs through a set of coils for heat dissipation and condenses into a liquid.

3. The liquid passes through an expansion valve quickly evaporating into cold low-pressure gas.

4. The cold gas (shown as blue in the figure) runs through a set of coils for heat absorption cooling down the air inside a building.

Complete setup for a building

Deep Lake Water Cooling

Along many lake shorelines and ocean coastlines, there is reasonable access to naturally cold water that is as cold or colder than the water used in conventional air conditioning systems. If this water can be tapped, then the significant power for operating mechanical chillers can be eliminated. The process is very similar to using chillers in conventional AC systems. The only difference is that the cold temperature is not achieved by evaporation of a liquid into a gas. Rather, it is retrieved from a natural cold water source - from a deep ocean or lake

Water is most dense at 3.98 °C (39.16 °F) at standard atmospheric pressure. Thus as water cools below 3.98 °C it decreases in density and will rise. As the temperature climbs above 3.98 °C, water density also decreases and causes the water to rise, which is why lakes are warmer on the surface during the summer. The combination of these two effects means that the bottom of most deep bodies of water located well away from the equatorial regions is at a constant 3.98 °C. The existence of the deep-water sink results from natural climatic processes where water is cooled at the poles, becomes dense, and sinks into the deep ocean. Temperatures of 8°C or colder can be reached at 700 m depth within the tropical zone, 4°C or colder at 1000 m. At depths exceeding 700 meters, these temperatures are equivalent to chill water temperatures required for space cooling.

Basic process :

MAIN COMPONENTS :

1. A Lake/Sea water open loop supply system which pumps deep cold water through a heat exchanger and returns the warm water through a shallow outfall.

2. Fresh water closed loop system pumps warm water through the cooling station heat exchanger and distributes the cooled water among commercial, residential and institutions for air conditioning.

3. A heat exchanger (cooling station) transfers heat from the fresh water distribution loop resulting in cold water for air conditioning purposes.

Auxiliary ChillersIn some cases, it may be either too costly or impractical to supply coldwater at the necessary low temperatures to maintain minimum temperatures in the chilled water loop. The distance offshore to reach sufficiently cold water might be prohibitive or the bottom depth may simply not be available.

With the condenser kept cool, the auxiliary chiller can operate at an extremely high efficiency – as high as double that of a conventional chiller.

Environmental Benefits

Renewable energy source Energy efficient - saves more than 90% of the

energy required for conventional air conditioning Decreased reliance on the use of fossil fuels• reduced air pollution• reduced acid rain• reduced impact on global warming• reduced ecological impacts of resource extraction No use of ozone-depleting chlorofluorocarbons

(CFCs) Cold sea/lake water availability for secondary

applications Cost are nearly independent of future energy price

increase Short economic payback period

Economic Viability

Each location has unique opportunities as well as problems. The main factors influencing the economic viability of a specific location include: 1.The distance offshore to cold water.  2.The size of the air conditioning load.3.The local cost of electricity:  A high cost of electricity makes conventional AC more costly and deep water cooling, in comparison, more attractive.

Aerial view of Lake Ontario, Enwave Corporation

Comparison

Illustration of five DLWC scenarios of varying sizes

REFERENCES

Lenore Newman, Yuill Herbert, “The use of deep water cooling: Two Canadian examples”, Renewable Energy 34 (2009) 727-730.

Deep Lake Water Cooling-Wikipedia Stephen K. Oney, Christopher M. Looney, “Seawater

District Cooling And Lake Source District Cooling”, OCEES International, Inc.

SWAC – Sea Water Air Conditioning, Makai Ocean Engineering.

Boyce F, Hamblin P, Harvey L, Scherzer W, McCrimmon R. Response of the thermal structure of Lake Ontario to deep cooling water withdrawals and to global warming. J Great Lake Res 1993; 19(3):603–16.

THANK YOU!!

Any questions