What is air-conditioning and how is it different from other cooling technologies?
One of the clearest schemata that provides the distinction between air-conditioning and other forms of climatic control is provided by Reyner Banham in The Architecture of the Well-tempered Environment. Using the parable of a savage tribe that encountered some fallen timber at a camp-site, Banham noted that there were two ways the tribe could use the timber for environmental management – to construct a “wind-break or rain-shed” or to build a fire. Banham called the former the structural solution and the latter the power-operated solution. They are also widely known as the passive and active approaches to environmental management. In this distinction, air-conditioning, unlike building features such as brise-soleil, verandah and the adobe wall covered in earlier lectures, is the power-operated solution or the active approach to environmental management.
Air-conditioning, which is the power-operated solution for cooling and dehumidification, has two prerequisites before it could be successfully invented and widely implemented. The first revolves around scientific understanding of the relationship between energy, air temperature, volume and pressure. Charles’ and Boyles’s laws established the relationship between the air temperature, volume and pressure. The discovery of the first and second laws of thermodynamics further contributed to the understanding of the relationship between heat, energy and work done. These scientific developments were concurrent with the development of different versions of the steam engine that established the technological bases for subsequent refrigeration and air-conditioning equipment.
The second prerequisite of modern power-operated solution is a readily available supply of energy. This supply became widely available with the building of an infrastructure of electricity that started in the late nineteenth century and the subsequent electrification of many parts of the world. Air-conditioning’s dependency on not just energy but large amount of energy would later present many challenges and attract much criticisms.
Before the two prerequisites were met and the invention of air-conditioning, cooling and the attainment of comfort through the lowering of air temperature or dehumidification was not possible. Pre-air-conditioning technologies provided cooling by increasing the circulation of air. An example of such a technology is the punkah, “a large cloth fan on a frame suspended from the ceiling” that was pulled by a servant, or punkah wallah, to circulate the air. The punkah was widely used by the British in India during the nineteenth century and its use subsequently spread to the other parts of the British Empire. In this case, the supply of energy to move the punkah came from muscular power of the punkah wallah. The popularity of the punkah could be attributed to the abundant supply of cheap labour in many British colonies.
The second example, also first used in British India, is the thermantidote, which is a compound word made up of therm, a British thermal unit, and antidote. Thermantidote is essentially a contraption that combines a fan powered by human or animal muscular power with a tatty, a screen kept moist by periodic wetting. It blows moisturized air and provides evaporative cooling. An 1850 account of the thermantidote in India describes it as an enormous and cumbersome machine with fans turned by two men. It was placed in the verandah and had a projecting funnel that was fixed into the window of a house. Tatties were affixed to the sides of the thermantidotes so that the air drawn were moisturized and these tatties were kept moist by coolies who constantly drenched them (Parkes 2002 (1850), 112-3).
One of the first to apply the scientific understanding of the relationship between energy, air temperature, volume and pressure to create a mechanical refrigeration system was John Gorrie, a physician of Apalachicola, Florida. In 1840s and 1850s, he created an air-cycle refrigeration system that used steam engine to compress and expand air in order to cool and dehumidify it. Influenced by the prevalent miasmatic theories of disease transmission, Gorrie thought that heat and humidity intensified the amount of miasma, or poisonous air, produced and led to higher incidence of malaria fever. Gorrie thus intended to use the refrigeration system to improve public health and treat his patients. Later Gorrie modified the system to manufacture ice. Despite the Gorrie’s technological breakthrough, his inventions did not received any commercial backing and were not produced. It was only three to four decades later that mechanical refrigeration was used for the cooling of spaces, as we shall see.