Monday, July 30, 2012

Energy Consumption of a Desktop Computer

Some people have the habit of keeping the computer switch on for days, specially at the working place. Let's analyse the energy consumption of a desktop computer under various scenarios.

Below calculations are based on the computer I use at work place. It consumes ~70W when in operation. LCD monitor contributes 25W to it.

Assume your team size is 5 (each member has his/her own computer).

Average work hours per day = 11hrs (worst case)
Work hours per week per member = 11hrs * 5 = 55hrs
Total energy requirement per week per member = 55hrs * 70W = 3,850 Wh
Total energy requirement of all the members = 3850Wh * 5 = 19,250Wh

Scenario 1: Member "A" keeps his/her computer switch on for consecutive 2 days. (from [day1] 8AM to [day2] 5PM)

A's consumption = (33hrs  + 11hrs * 3) * 70W = 4,620Wh
Energy consumption of other members = 3,850Wh * 4 = 15,400Wh
Total consumption of all the members = 4,620Wh + 15,400Wh = 20,020Wh
Energy wastage = 20,020 - 19,250 = 770Wh (4%)

Scenario 2: Member "A" keeps his/her computer switch on for consecutive 3 days. (from [day1] 8AM to [day3] 5PM)

A's consumption = (57hrs  + 11hrs * 3) * 70W = 6,300Wh
Energy consumption of other members = 3,850Wh * 4 = 15,400Wh
Total consumption of all the members =  6,300Wh  + 15,400Wh = 21,700Wh
Energy wastage21,700 - 19,250 = 2,450Wh (13%)

Scenario 3: Members "A", "B" keep his/her computer switch on for consecutive 3 days. (from [day1] 8AM to [day3] 5PM)

(A+B)'s consumption = 2 * (57hrs  + 11hrs * 3) * 70W = 12,600Wh
Energy consumption of other members = 3,850Wh * 3 = 11,550Wh
Total consumption of all the members =    12,600Wh  + 11,550Wh = 24,150Wh
Energy wastage24,150 - 19,250 = 4,900Wh (25%)

I think you can understand these numbers. At least the percent wastage. Sadly, this is the behavior of average worker! Some workers even have the habit of keeping the computer switched on throughout the week. Monday morning switches on and Friday afternoon switches off!

There may be a requirement to keep the machine on while you are not at work. But those situations are exceptional and rather rare.

Do your bit for the country! Do your bit for the environment! Please make sure you turn off your computer when you leave the office!

Friday, May 11, 2012

Does bulk ironing save energy?

Recently one of my friends suggested that we may not be saving much energy if we iron clothes more than one at a time compared to ironing clothes separately. His argument was, unlike the old irons new steam irons might have designed to save energy by reducing the time it takes for preheating.

This sparked me to do another experiment nearly a year after to the last post :) and here it goes...

Iron I used

Make:Morphy Richards
Model:Comfigrip (40715)

Below table shows the experiment results.

From the above statistics,
for 1 piece, it consumes 0.09 kWh.
for 5 pieces, it consumes 0.28 kWh.

Below table summarizes power consumption to iron 20 pcs.

That is, if 10,000 people iron a week's clothes at once we can save 81,600 kWh of energy a year. It is equivalent to stopping release of 2907.24 kg of carbon-dioxide in to atmosphere.

Can't you still figure out how much is this 2907.24 kg?

It is equivalent to carbon-dioxide produced by a Toyota corolla (2002) when it goes 17,000 kilometers of distance a year and this is really big!

Next time please iron more than one cloth at a time. It saves you money and make the air we intake clean.


CFL Lifetime

CFL nominal rated lifetime is ~8000 hrs. But this will be affected mainly by operating voltage, manufacturing defects, exposure to voltage spikes, mechanical shock, frequency of cycling on and off, lamp orientation, and ambient operating temperature, among other factors.[1] Out of the above causes, at least "frequency of cycling on and off" and "lamp orientation" can be contrlled by the user.

I do not have much information about how "lamp orientation" will affect lifetime of CFL.

But according to, if you frequently on/off CFL its lifespan can be reduced to close to that of incandescent light. suggests if you leave the room for less than 15 minutes, better to switch on the CFL. In other words, switch off CFL when you are out for more than 15 minutes. Therefore, using CFLs in bathroom may not be a wise idea becasue, though it gives a reduced light bill, CFL replecement cost will tradeoff the benefits you get from a reduced light bill.

Next time, wait 15 mins before turning it off again... :)

Monday, March 28, 2011

Spin drying of clothes

After washing/rinsing clothes in the washing machine we normally spin dry the clothes for our convenience so that we can fold and put clothes back in the wardrobe quickly.

Does spin drying really necessary in a country like Sri Lanka? I don't think so!

We have abundant solar thermal heat for drying clothes rather than just letting it spin in the machine (and later quick drying).

Why should we opted to less convenient drying method (drying under the sun)? Here is why...
  1. Durability of clothes - when you spin dry clothes it becomes shrink, less soft and fade (sometimes you may have experienced these).
  2. Durability of machine
  3. Energy saving - please see below for my experiment results
But drying under sun may not always be applicable. But it must be used whereever/whenever it is possible.

See below for my experiment results on spin drying and as you can see, the experiment results is a proof for 3rd point I mentioned above.

Washer make/model:LG/WF-S6061PC 6.0 kg
Power factor:0.56
Weight of clothes:2.0 kg [though the machine is 6.0 kg capable, 2.0 kg filled almost ~80% of tumbler :D]
Energy consumed for wash/rinse cycle:0.03 kWh
Energy consumed for Spinning:0.01 kWh

From the above facts 1/4th of total energy is used for spinning.

Please do dry clothes under Sun!

Wednesday, February 2, 2011

Blog Template changed

I changed the blog template to a more lighter one to save energy.

I did so based on the assumption that most of computer screens of this blog's audience have LCD screens. It is because LCD screen uses less energy when the screen displays light colors.

Friday, January 28, 2011

Health hazard of CFL bulbs

CFL bulbs are as safe as incandescent bulbs unless the bulb is not broken. Once it is broken it has to be handled with great care. Never throw it in the trash. It has to be recycled.

CFL contains a neurotoxin called mercury (5 mg) in vapor form for its operation. It is this mercury vapor which causes health problems.

Environment Protection Agency of USA has issued a set of instructions as to how to Clean up a broken CFL. Here is a summarized version:

1. Have people and pets leave the room.
2. Open windows/doors for 5-10 minutes.
3. Collect broken glass and visible powder to a sealable container.
4. Place the container outside and dispose properly.
5. If practical, keep the windows/doors opened for several hours

Cleaning Up a Broken CFL

image copyright -

Tuesday, November 23, 2010

Standby Power

Standby power, Vampire power, Vampire draw, Phantom load or Leaking electricity

Everything above speaks the same. It is about the energy we "used to" waste just because of our negligence and/or unawareness. This is the power consumed by an electronic equipment while it is "sleeping", i.e., when the equipment is put on to Standby mode.

Standby mode:
Todays electronic appliances have a feature called standby mode. You don't have to unplug the equipment from mains supply to switch it off (?) for the sake of convenience. You can use the remote control to put it on Standby mode so that you do not have to plug it again when you have to switch on the equipment next time.

What is the difference between Standby mode and Switching off?
Standby mode puts the appliance to sleep but it is listening to commands sent by the remote controller. "Listening circuitry" in the appliance is not sleeping. For this listening, certain amount of power is consumed. Power consumed for this "listening" depends on the appliance. This may be varied between 1W and 15W.
By switching off (un-plugging from the wall socket) an appliance you can switch off the "listener" as well.

Therefore, by turning off an appliance we can make sure that it does not draw power!

Standby Power Summary Table page has summarized some of the power consumptions of various appliances. Please take a closer look at this table. You can find how much power being wasted at your home/work place.

Next time please switch off your appliance when not in use and help save the world!