Cut Air Conditioning Bills by 50%

Introduction

The advent of Technology makes home office a reality. Many people are now working from home, communicating to the outside World through Computers/Internet. Home office doesn’t necessary need lots of space but they will need air-conditioning. This article will tell how one could beat that rise in electricity rate and cut more than 50% in air conditioning bill to cool the home office.

How?

By reducing the space of cooling and by introducing spot cooling.

According to estimate, the air-conditioning bill can come to around S$850/= per year if one uses a standard HDB room for 10 hrs per day. Up to S$450/= or 50% of the bill can be saved.

Can you Explain?

In air-conditioning , about 30 to 40% of the cooling losses are through the walls and the infiltrated air that seep through door and window gaps. By moving the home office from a standard HDB room to a newly converted or partitioned smaller room, one can reduce the space of cooling and save as much as 35% and further, by using spot cooling, one can save another 18 to 20%.

What’s Spot Cooling?

Spot cooling is a term often related to temporary cooling or cooling of a specific area or equipment. Spot cooling has been used in industrial plants and factories for years. In our application, we refer to coolings directed to a room occupant.

Is Spot Cooling Comfortable?

For comfort cooling, room air should be around 25 oC @ 55% relative humidity. Air often leaves the cooling coil at around 15 oC with 100% relative humidity. As conditioned air picks up heat, it reduces its humidity; hopefully, by adjusting the thermostat, the air would reach the person at about 25 oC @ 55% relative humidity. Actual example indicates that this can be achieved when the thermostat temperature is around 28 to 29 oC, which is 3 to 4 oC differences from 25 oC. According to a rough estimate, for every degree rise in cooling air, one could save about 6-8% (derived from Psychrometric Chart) or total of about 25% energy saving for a 4 oC rise !

What about Housekeeping?

One should ensure
1) Air-conditioning system has sufficient charge of Freon. Experiments show that by undercharging Freon by 10%, it reduces cooling by 4%; however, ice would start to form at the coil when Freon level drops to 80%. According to some estimates, the cost of recharging can be recovered in a period of 3 to 4 months;
2) Air filters are often cleaned. Use disposable secondary filter if possible;
3) Evaporator and condenser are pressured-water cleaned at least once a year and chemical cleaned once every 2 years.