Solar powered air conditioning[edit | edit source]

Solar powered air conditioning was discussed some time in the 1980s in Popular Science magazine. A dehumidifierW featuring some kind of desiccant (water absorbing material) removes moisture from the air. The air is then passed by water, which evaporates, cooling the air and restoring moisture. The desiccant is then exposed to the sun, drying it and enabling it to be used again. (For example, it may be in the form of a rotating wheel, half in the air stream, half drying at any one time.)

This assumes that when the moisture is first absorbed by the desiccant, the latent heat of vaporisation is released into the desiccant rather than into the air. The desiccant is also not cooled down afterwards, but actually heated up by drying it in the sun. So the dried desiccant would act as a heat source. Is it possible to surmount these problems? Have such systems been built - or can they be? If so, how cost-effective are they?[expansion needed]

Energy use[edit | edit source]

Air conditioners are one of the most intensive users of electricity - although they do not need to be operated all day, nor all year, in most climates.

The need for air conditioning can be greatly reduced through building design, notably passive solarW and good insulation. See Alternative building

Counteracting heat from appliances[edit | edit source]

Extra energy is used when using heat-producing appliances in an air conditioned room or building. There is not only the energy used by the appliance, but a greater amount of energy to remove the heat from that appliance. Wikipedia:Air conditioning#Energy use states:

It should be noted that in a thermodynamically closed systemW, any energy input into the system that is being maintained at a set temperature (which is a standard mode of operation for modern air conditioners) requires that the energy removal rate from the air conditioner increase. This increase has the effect that for each unit of energy input into the system (say to power a lightbulb in the closed system) requires the air conditioner to remove that energy. In order to do that the air conditioner must increase its consumption by the inverse of its efficiency times the input unit of energy. As an example presume that inside the closed system a 100 Watt light bulb is activated, and the air conditioner has an efficiency of 50%. The air conditioners energy consumption will increase by 200 Watts to compensate for this, thus making the 100W light bulb utilise a total of 300W of energy.

Peak load[edit | edit source]

Air conditioners being turned on during the hottest days of summer account for the highest peak loads experienced by many cities' electricity infrastructure.[verification needed] Thus much extra capacity needs to be built into the generating equipment, at the expense of many millions of dollars, and it is then only used for a few days per year.

Suggested solutions:

  • Ban air conditioners. This could lead to heat stroke and even death by elderly and susceptible people during a heat wave.
  • Peak pricing: charging a higher price for electricity during certain hours of the day in summer. This requires specialized meters to measure the eletricity used in different time periods (similar to off-peak hot water heaters). This has the advantage of not restricting use when needed, but discouraging wastefulness.
  • Rely more on solar energy, which provides most power at the time when air conditioning is most needed.
  • Encourage retrofitting of cooling, energy-saving design features such as awnings, insulation, and roof ventilation.
  • Re-use cooled air by integrating an Air decohesion processor (ADP) into the system. This low-energy consuming device cleans used and already cooled/(heated) air, leaving the temperature at the desired level and destroying unwanted substances.

Quieter operation[edit | edit source]

Using a diffuserW which sends air along the ceiling results in the same spread of air for less discharge velocity - meaning a smaller fan and less noise (and we might guess it would give a very slight saving in power usage - unless the air is heated by contact with the ceiling, in certain circumstances[expansion needed]).

Wikipedia:Coandă effect#Air conditioning states:

In air conditioning the Coandă effect is exploited to increase the throw of a ceiling mounted diffuserW. Because the Coandă effect causes air discharged from the diffuser to "stick" to the ceiling, it travels further before dropping for the same discharge velocity than it would if the diffuser was mounted in free air, without the neighbouring ceiling. Lower discharge velocity means lower noise levels and, in the case of variable air volume (VAV) air conditioning systems, permits greater turn-down ratios. Linear diffusers and slot diffusers that present a greater length of contact with the ceiling exhibit greater Coandă effect.

Reverse cycle air conditioners[edit | edit source]

Reverse cycle air conditionersW can also be operated as a highly efficient heater. As they are a heat pump rather than a heat generator, they can bring more heat energy into a room or building than the energy consumed by the appliance. Do reverse cycle air conditioners have a different name? (Also asked here.)