Cooling
Content
Cooling 1. Background 2. Definition 3. Consideration a. Passive b. Active 4. Energy Efficient Cooling for Sustainability in Buildings
Background:
Malaysia is a hot-humid climate with unpredictable wind direction. This does not help its case when it comes to cooling. Malaysia experience monsoon and dry seasons all year round with its location located right next to the equator. In terms of receiving daylighting, Malaysia is the best place to harvest solar power for electricity. To achieve human comfort in the macro-climate in Malaysia is not an easy task. We cannot disregard the active mechanism entirely to achieve comfort level for sustainability for the tropical climate of Malaysia does not permit that. The two conditions that must happen at the same time to reach the comfort level are: Under shaded condition Ample wind or air movement
Ample shade and wind movement.
Thus, air movement need to be induced so that the human body can experience comfort. New fresh air too is needed in spaces inside. This will help to cause the exchange of used air and fresh air which will cause the air to move. In large spaces and more complex building, used air need to be replaced with fresh air. So, HVAC (heating, ventilation and air conditioning) system is used in order to provide fresh air to spaces that requires certain level of fresh air (eg. Hospitals, laboratories). In high rise building, wind can be collected and cause a cross-ventilation into the spaces in the building. This is because in high rise buildings, the higher you go, the velocity of wind gets higher. Thus, passive methods can be used in bringing air movement into buildings. This will helps to reduce the dependence of the building to active methods. Passive cooling has been used in many indigenous buildings and many of the methods are based on the designs that have helped our grandparents to find comfort in the places they are in.
High rise building.
A typical Malay traditional house.
Definition:
Hot-humid climate: Combination of seasonal rain and high air temperature. All year round sun shine with many rainy seasons, usually in certain months. Air temperature rises to 34°C and rain collection to rise about 2000mm/month. Humidity level is about 70-80% RH. HVAC system: HVAC (heating, ventilation, and air conditioning) is based on major subdiscipline of mechanical engineering of thermodynamics and fluid mechanics. Passive cooling: Methods used to cool a space or building without the use of mechanical system or mechanism. Active cooling: Mechanical system or mechanism used to cool a space or building. Considerations: Passive cooling: Passive methods can be adapted as well to improve the workability of the building in reducing the workload and energy used on the active system. Passive designs can be implemented to help slow down the rate of heat absorption into the building. Through this, occupants are able to enjoy the activities they do around the comfort area. Few of the considerations that involve in the passive cooling is cross-ventilation, stack effect and building layout orientation. Active cooling: Active cooling is needed in certain countries due the extreme climate conditions to cool the conditions of the spaces inside. Energy Efficient Cooling for Sustainability in Buildings: Here are the few examples of sustainable cooling mechanisms that have been introduced. District Cooling
District Cooling System (DCS) is a total integral system of both the plant itself and the air conditioning system. And DCS is a highly effective mean of both energy saving and health management. It contributes to the society as a whole by utilizing limited energy resources and space efficiently to provide a reliable service. In order to achieve a successful DCS project, it is essential to have abundant knowledge of the air-conditioning system and cutting edge technology throughout the whole project from planning till operation. DCS is a total integral system of both the plant itself and the air-con system.DCS will be expected as vital system for urban development in 21st century. Advantages: o o o o o o o Improve efficiency of energy Protect environment Save space Improve urban view Re-use the heat from exhaust system Prevent disaster Reduce manpower for operation and maintenance
Ground-Coupled Cooling System Ground-coupled heating-cooling systems (GCHCSs) exchange heat between the built environment and the subsurface using pipework buried in trenches or boreholes. If heat pumps in GCHCSs are powered by “green electricity,” they offer genuine carbon-free heating-cooling; for this reason, there has been a surge in the technology in recent years. Interference between adjoining installations is being reported, raising issues of sustainability in terms of performance, equitable sharing of natural resources, and localized ecological impacts. Using an analytical model for heat transport in porous media, sensitivity analyses have been obtained for open-loop systems in typical hydrogeological settings for urban GSHCSs in the United Kingdom, revealing that breakthrough of injected water will likely lead to significant declines in system performance in less than 25 years for well spacings less than 300 m, unless injection rates are kept below 250 m3/d. Only by cooperatively planning will adjoining landowners in urban areas achieve large-scale sustainable system designs.
Aquifer cooling Also known as Geothermal Heating and Cooling Systems provide space conditioning -- heating, cooling, and humidity control. They may also provide water heating -- either to supplement or replace conventional water heaters. Geothermal Heating and Cooling
Systems work by moving heat, rather than by converting chemical energy to heat like in a furnace. Every Geothermal Heating and Cooling Systems has three major subsystems or parts: a geothermal heat pump to move heat between the building and the fluid in the earth connection, an earth connection for transferring heat between its fluid and the earth, and a distribution subsystem for delivering heating or cooling to the building. Each system may also have a desuperheater to supplement the building's water heater, or a fulldemand water heater to meet all of the building's hot water needs. There are four (4) types of loops or system of the ground coupled cooling. The horizontal, vertical, slinky, and pond loops. The horizontal loop is generally most cost-effective for small installations, particularly for new construction where sufficient land area is available. These installations involve burying pipe in trenches dug with back-hoes or chain trenchers. Up to six pipes, usually in parallel connections, are buried in each trench, with minimum separations of a foot between pipes and ten to fifteen feet between trenches.
Horizontal Loop
Vertical loop is preferred in many situations. For example, most large commercial buildings and schools use vertical loops because the land area required for horizontal loops would be prohibitive. Vertical loops are also used where the soil is too shallow for trenching. Vertical loops also minimize the disturbance to existing landscaping. For vertical closed loop systems, a U-tube (more rarely, two U-tubes) is installed in a well drilled 100 to 400 feet deep. Because conditions in the ground may vary greatly, loop lengths can range from 130 to 300 feet per ton of heat exchange. Multiple drill holes are required for most installations, where the pipes are generally joined in parallel or series-parallel configurations. A vertical loop well field, being used for the Finger Lakes Institute, consists of 20 wells, drilled to a depth of 100’. There are 5 (clusters) of 4 wells spaced approximately 12 feet on center, The depth and number of wells was determined by the estimated heat and cooling load required maintain a comfortable environment for the occupants.
Vertical Loop
Slinkly loop is used to increase the heat exchange per foot of trench, but require more pipe per ton of capacity. Two-pipe systems may require 200 to 300 feet of trench per ton of nominal heat exchange capacity. The trench length decreases as the number of pipes in the trench increases -- or as Slinky coil overlap increases. (Illustration below shows a slinky coil in a pond)
Slinkly Loop
Pond loop is is deep enough and with enough flow, closed loop coils can be placed on the pond bottom. Fluid is pumped just as for a conventional closed loop ground system where conditions are suitable, the economics are very attractive, and no aquatic system impacts have been shown.
Background:
Malaysia is a hot-humid climate with unpredictable wind direction. This does not help its case when it comes to cooling. Malaysia experience monsoon and dry seasons all year round with its location located right next to the equator. In terms of receiving daylighting, Malaysia is the best place to harvest solar power for electricity. To achieve human comfort in the macro-climate in Malaysia is not an easy task. We cannot disregard the active mechanism entirely to achieve comfort level for sustainability for the tropical climate of Malaysia does not permit that. The two conditions that must happen at the same time to reach the comfort level are: Under shaded condition Ample wind or air movement
Ample shade and wind movement.
Thus, air movement need to be induced so that the human body can experience comfort. New fresh air too is needed in spaces inside. This will help to cause the exchange of used air and fresh air which will cause the air to move. In large spaces and more complex building, used air need to be replaced with fresh air. So, HVAC (heating, ventilation and air conditioning) system is used in order to provide fresh air to spaces that requires certain level of fresh air (eg. Hospitals, laboratories). In high rise building, wind can be collected and cause a cross-ventilation into the spaces in the building. This is because in high rise buildings, the higher you go, the velocity of wind gets higher. Thus, passive methods can be used in bringing air movement into buildings. This will helps to reduce the dependence of the building to active methods. Passive cooling has been used in many indigenous buildings and many of the methods are based on the designs that have helped our grandparents to find comfort in the places they are in.
High rise building.
A typical Malay traditional house.
Definition:
Hot-humid climate: Combination of seasonal rain and high air temperature. All year round sun shine with many rainy seasons, usually in certain months. Air temperature rises to 34°C and rain collection to rise about 2000mm/month. Humidity level is about 70-80% RH. HVAC system: HVAC (heating, ventilation, and air conditioning) is based on major subdiscipline of mechanical engineering of thermodynamics and fluid mechanics. Passive cooling: Methods used to cool a space or building without the use of mechanical system or mechanism. Active cooling: Mechanical system or mechanism used to cool a space or building. Considerations: Passive cooling: Passive methods can be adapted as well to improve the workability of the building in reducing the workload and energy used on the active system. Passive designs can be implemented to help slow down the rate of heat absorption into the building. Through this, occupants are able to enjoy the activities they do around the comfort area. Few of the considerations that involve in the passive cooling is cross-ventilation, stack effect and building layout orientation. Active cooling: Active cooling is needed in certain countries due the extreme climate conditions to cool the conditions of the spaces inside. Energy Efficient Cooling for Sustainability in Buildings: Here are the few examples of sustainable cooling mechanisms that have been introduced. District Cooling
District Cooling System (DCS) is a total integral system of both the plant itself and the air conditioning system. And DCS is a highly effective mean of both energy saving and health management. It contributes to the society as a whole by utilizing limited energy resources and space efficiently to provide a reliable service. In order to achieve a successful DCS project, it is essential to have abundant knowledge of the air-conditioning system and cutting edge technology throughout the whole project from planning till operation. DCS is a total integral system of both the plant itself and the air-con system.DCS will be expected as vital system for urban development in 21st century. Advantages: o o o o o o o Improve efficiency of energy Protect environment Save space Improve urban view Re-use the heat from exhaust system Prevent disaster Reduce manpower for operation and maintenance
Ground-Coupled Cooling System Ground-coupled heating-cooling systems (GCHCSs) exchange heat between the built environment and the subsurface using pipework buried in trenches or boreholes. If heat pumps in GCHCSs are powered by “green electricity,” they offer genuine carbon-free heating-cooling; for this reason, there has been a surge in the technology in recent years. Interference between adjoining installations is being reported, raising issues of sustainability in terms of performance, equitable sharing of natural resources, and localized ecological impacts. Using an analytical model for heat transport in porous media, sensitivity analyses have been obtained for open-loop systems in typical hydrogeological settings for urban GSHCSs in the United Kingdom, revealing that breakthrough of injected water will likely lead to significant declines in system performance in less than 25 years for well spacings less than 300 m, unless injection rates are kept below 250 m3/d. Only by cooperatively planning will adjoining landowners in urban areas achieve large-scale sustainable system designs.
Aquifer cooling Also known as Geothermal Heating and Cooling Systems provide space conditioning -- heating, cooling, and humidity control. They may also provide water heating -- either to supplement or replace conventional water heaters. Geothermal Heating and Cooling
Systems work by moving heat, rather than by converting chemical energy to heat like in a furnace. Every Geothermal Heating and Cooling Systems has three major subsystems or parts: a geothermal heat pump to move heat between the building and the fluid in the earth connection, an earth connection for transferring heat between its fluid and the earth, and a distribution subsystem for delivering heating or cooling to the building. Each system may also have a desuperheater to supplement the building's water heater, or a fulldemand water heater to meet all of the building's hot water needs. There are four (4) types of loops or system of the ground coupled cooling. The horizontal, vertical, slinky, and pond loops. The horizontal loop is generally most cost-effective for small installations, particularly for new construction where sufficient land area is available. These installations involve burying pipe in trenches dug with back-hoes or chain trenchers. Up to six pipes, usually in parallel connections, are buried in each trench, with minimum separations of a foot between pipes and ten to fifteen feet between trenches.
Horizontal Loop
Vertical loop is preferred in many situations. For example, most large commercial buildings and schools use vertical loops because the land area required for horizontal loops would be prohibitive. Vertical loops are also used where the soil is too shallow for trenching. Vertical loops also minimize the disturbance to existing landscaping. For vertical closed loop systems, a U-tube (more rarely, two U-tubes) is installed in a well drilled 100 to 400 feet deep. Because conditions in the ground may vary greatly, loop lengths can range from 130 to 300 feet per ton of heat exchange. Multiple drill holes are required for most installations, where the pipes are generally joined in parallel or series-parallel configurations. A vertical loop well field, being used for the Finger Lakes Institute, consists of 20 wells, drilled to a depth of 100’. There are 5 (clusters) of 4 wells spaced approximately 12 feet on center, The depth and number of wells was determined by the estimated heat and cooling load required maintain a comfortable environment for the occupants.
Vertical Loop
Slinkly loop is used to increase the heat exchange per foot of trench, but require more pipe per ton of capacity. Two-pipe systems may require 200 to 300 feet of trench per ton of nominal heat exchange capacity. The trench length decreases as the number of pipes in the trench increases -- or as Slinky coil overlap increases. (Illustration below shows a slinky coil in a pond)
Slinkly Loop
Pond loop is is deep enough and with enough flow, closed loop coils can be placed on the pond bottom. Fluid is pumped just as for a conventional closed loop ground system where conditions are suitable, the economics are very attractive, and no aquatic system impacts have been shown.
