Cut Your Cooling Bills by 50% to 90%

1 October 2008

Introduction

Electricity rate in Singapore went up by 21% from 1 October 2008 from $0.26 per kWh to $ 0.30 per kWh. It is likely that this rate will remain high because of the ever increasing higher energy consumption that has driven up the energy price. We are addicted to comfort living and working nowadays. This article will tell how one could use available gadgets in the market to get some desired cooling and to cut electricity consumption by as much as 90% at the same time.

How?

a) Cut up to 50% by reducing the space of cooling and by introducing spot cooling. Please refer to article for this method ;
b) Cut up to 90% by using ultrasonic humidifiers (UH) and fans for direct cooling. This article will concentrate on how this can be done.

Using Humidifiers in Singapore?  (added 17 December 2021)

Some doubted that Singapore,  being a tropical country with very high humidity, is not place suitable to use humidifiers for cooling.   This is quite true especially when this kind of cooling is less effective in areas of higher humidity.  Buut one can still feel the cooling because the fans will help to evaporate those mists that fell onto the face and body faster than those from other parts of the body.   This cooling is like one cleans his face with a piece of wet cloth and stand in front of a fan.     Moreover,  in a hot dry weather day,  Singapore's humidity at certain parts can be as low as 70%. 

What is Ultrasonic Humidifiers (UH)?

It is an electro-mechanical device that can generate aerosol mists, much like the steam vapour that we produce when we boil the water. UH is cheap and easily available in Supermarkets, Homefix etc. They cost around $ 80 to $ 300 per unit.

How does UH work?

UH has 3 basic components:-
a) an ultrasonic vibration unit to generate the fine mists;
b) a small mechanical fan to distribute the mists and
c) a water container


The more sophisticated ones may have various controls for the fan speed and humidity adjustments. The heart of UH is a piezo-electric transducer that looks like a 50 cts coin or a Lithium Battery cells of that size. This transducer is electronically driven to vibrate at frequencies in the range of 0.8 MHz to 1.7 MHz. When water comes into contact with the vibrating transducer, the water is immediately broken down into fine mist, about 1 to 3 micron in diameter. Unlike boiling of water, no heating is required to produce this mist and therefore, little energy is used for the operation. A medium sized UH would consume only about 50 Watts of electricity.

How Effective is the UH Cooling?

UH will not be able to cool a room to the comfort of an air-conditioning unit especially in a hot and humid environment like Singapore. However, its direct cooling effect is much better than an electric fan. This cooling feels like when we are next to a strong water stream when we are in a shower.
Normally, Singapore's ambient air temperature stays around 23 -34 oC with humidity varies from 60% in the afternoon to 100% during rainy days. One can expect UH to lower the cooling temperature by 2 to 4 0C according to the following table.


UH will work better under a high ambient temperature and low humidity environment. Further cooling effect can be achieved if a strong mechanical fan can be used to create Flash Cooling.

What are the other Advantages?

Besides saving electricity, the unit will operate quietly with very little maintenance except for the frequent topping up of water as it evaporates. For those who constantly stare at computer screens, the higher room humidity will help them keep their eyes moist to prevent “dry eye” problem. Because UH operates at ultrasonic frequencies, it should have some bacteria killing effects.

What are the Health Concerns?

UH operates in frequencies between 0.8 to 1.7 MHz. This range of frequency is known to have effect of killing germs or microbes . However, there were no evidence that commercial UH also have these effects.
UH, like all equipment, will require regular maintenance to keep the unit hygienically clean. Legionnaire's bacteria , said to be found in water systems such as cooling towers and evaporative condensers, has not been reported in UH applications.

What about People with Rheumatism?

Scientists have found that weather or temperature and humidity's variation doesn’t cause rheumatism and doesn’t damage joints but they did find that weather does affect the severity of rheumatic pain. This is because bones, tendons, muscles, and joints have different densities and expand or contract differently when exposed to drops or rises in temperature and humidity. These weather sensitive people may found it uncomfortable with this kind of cooling.

What Water to be Used?

Ordinary tap water can be used if they are soft water (contained less minerals); however, distilled water is recommended by most manufacturers. Hard water has been found to be not suitable for UH because they have bicarbonates and sulfates that will form scaling to "kill" the transducer.
Distilled water is expensive although there are other alternatives. It may be more cost effective to use ordinary tap water and have the piezo-electric transducer replaced regularly.

Getting soft water from air-conditioning units is one good alternative to save money.

What size of a UH Unit should I purchase?

There is a co-relationship between the moisture of room air and the additional moisture to be added to achieve the desired cooling effect. One could use a psychromatic chart to determine the number and the unit sizes if one wishes to cool the whole room. However, for the purpose of achieving a direct cooling and not room cooling, a medium size UH that is capable of delivering about 400 ml/hr has been used successfully.

Related Articles
1. Soft Water Supply for Ultrasonic Humidifiers
2. Repairing Ultrasonic Humidifiers