Evaporative Cooling System Design | Passive Low Energy Systems
An overview of evaporative cooling systems
Evaporative cooling systems uses evaporation as a cooling method in cooling the surrounding air by adding moisture in the air hence increasing humidity. It is a low energy passive system. The following sections are categorized into sections stating the required conditions, implementation considerations and other issues. Case studies are listed as reference to discuss on how these systems are implemented and the implication they have on architecture design.
Climate: Evaporative cooling systems are suitable in any dry climate, especially cool and dry climates. For example, it can be used in high altitude regions. A dry environment is needed for evaporative cooling due to higher evaporation rates. The evaporation process would absorb heat and create coolness in the surrounding.
Areas with cooler temperatures are also preferred, as the gap between the environmental ambient temperature and human comfort range is smaller as compared to a hot and dry environment. This would translate into energy saved due to a lower cooling load.
Application: Evaporative cooling systems are suitable for residential, industrial and commercial buildings; especially in areas with big open spaces that encourages air circulation. Integration of evaporative cooling systems with other active systems are dependent on site conditions. Filters to purify polluted air, humidifiers to maintain the humidity or other active systems can be installed in tandem with evaporative cooling.
Architectural design: Architectural aesthetics may be affected upon the introduction of the passive downdraft evaporative cooling towers due to the exposed shafts. The introduction of underground evaporative cooling shafts would also affect the spatial planning of underground spaces. In addition, the provision of water bodies has to be taken into consideration with the overall building design.
Cost: Initial building cost is generally higher, as there is a need to construct addition structure and the equipment needed is usually more costly as compared to the conventional cooling systems. However, the advantages are that it reduces operational cost significantly.
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Issues in Evaporative Cooling Systems
Human comfort: There is a need for an integration of passive and active design to ensure human thermal comfort levels are met. Evaporative cooling is a passive process where it acts as a pre- conditioner to cool the air before using mechanical means to maintain humidity level.
Energy consumption: The systems has higher embodied energy due to the construction of infrastructure, but generally energy consumption will be greatly reduced in the range of 25% - 70%, depending on the individual evaporative cooling system setup.
Integration:The energy consumption of the system can be further reduced with the help of other systems. For example, evaporative cooling systems can be integrated with solar chimneys to enhance air-flow or incorporate renewable energy supply to further reduce energy consumption.
Case study: Torrent Research Centre, Ahmedabad, India
A passive downdraft evaporative cooling (PDEC) system is selected. Vertical shafts acts as a cooling tower with smaller exhaust shafts. These are placed at strategic locations. Mircronisers installed at the top of the cooling towers react automatically to temperature & humidity conditions to produce a fine mist that cool the air.This causes the air to sink and flows into the corridors and hopper windows. The system operates differently in different seasons. They are as follows:
& dry season( March to June) – Evaporative cooling through PDEC systems
2) Warm & Humid Season( July to September) – Mechanical Ventilation through ceiling fans
3) Cold & Dry Season(October to February) – Minimize Ventilation through adjustment of openings
4) Air-conditioning for selected areas
An active system is integrated with the passive design. The operation of the motorized dampers and exhaust fans is used to induce ventilation so that a consistent comfortable environment can be provided.
The resultant architectural form dominated by the ventilation towers with shading devices to articulate the facade.
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