Why Brunei did NOT save 231 MW during Earth Hour

(Source: Brunei Times)

So we all know that Brunei has officially participated in the Earth Hour initiative on the 27th March 2010, asking people to turn off unnecessary lightings from 8.30 to 9.30pm.

The next day, while I was reading the news, it made headlines, quoting a 231 MW 'savings'. When i first read it, i was shocked. To have a better feel of the numbers, Brunei has a total installed capacity of about 800 MW; Brunei is looking into buying 400 MW electricity from Malaysia (wow!). and to save 231 MW for a period of on hour means Brunei managed to slashed its power consumption by more than 25% in that hour. In fact, at night, as you can see from the graph, the power required is only about 480 MW. To cut 231 MW means nearly half of the nation's requirement on electricity was shut down.

Did this happen? No.

Let me try to explain this. We first have to turn to secondary school physics lessons to understand the difference between energy and power.

Electricity is a form of energy and the Joule (J) is the normal unit for energy. Power, on the other hand, is the rate of energy used, i.e. the amount of energy used per unit time, expressed as J/s, or the Watt (W).

For e.g., if your kettle is labelled 1.5 kW, and you turn it on for 6 minutes, the energy used is 1500W x (6 x 60)s = 540 000 J. [Energy = Power x Time]

Now for convenience, we can also express it this way. 1.5 kW x 0.1 h = 0.15kWh. It is still power multiplied by time, just that the unit for energy is now kWh. Your electricity bill will be charged by the amount of kWh you use.

Let me stress once again, that kWh is a unit for energy while kW is a unit for power. Power is energy/time; Energy = Power x time.

Now that we're clear, let's have a closer look at the reporting of the Earth Hour. (http://www.bt.com.bn/en/news-national/2010/03/29/brunei-saves-231mw-during-earth-hour)

(Source: Brunei Times & Department of Electrical Services)

It seems as if people have calculated the 'savings' in energy based on the difference in electrical consumption of the 27th March to the 26th March. This assumes the electricity consumption patterns is the same for both days - and that if Earth Hour did not happen, the electricity consumption would be the same.

There are a few things to tackle here:

1) First of all, you can't save 231 MW of energy. MW is not a unit of energy. In fact, it is quite clear that the difference in power consumption between the two days only ranges about 30-40 MW depending on which measurement you look at.

Another number quoted was that over that hour, we saved 38.5 MWh of energy - this is consistent with the units used and I think this number came from the Department of Electrical Services. I was wondering what mathematical gymnastics the reporters did to get 231 and stumbled across this: If we multiply 38.5 by 6 measurements, we get 231. (!!!) does it mean anything? Not really. If we did this, it's the amount of energy you would save if you do earth hour 6 times, and the units are MWh. (not MW)

You can't say you save 231 MW of energy. It's like saying I drove across 80 km/h of distance.

okay that's bad reporting out of the way - let's look at more meaty stuff.

2) 38.5 MWh saved over that hour. How did they arrive at this number. With the data given on the newspaper, I did a calculation based on the difference in the blue and red curves and integrated this to get energy. (See method 1 in the table). I got a value of 38.2 MWh, which is reassuring.

For those not familiar with integration, it is basically the summation of the 'area under the curve'. To get energy, the function of power is integrated over time. think of it as power x time = energy.

Now we have to argue whether the assumption that the energy usage for the 26th is the same for the 27th.

Earth Hour started at 8.30pm. What was interesting to me is that even by 8.00pm, there is already a difference in power level of about 20 MW between the two days. (see first 3 points of the red and blue) I then proceeded to take the average difference between the three points, and moved the blue curve down, creating the green curve.

This assumes the same trend, only with a difference determined by the first three points. What i'm saying is that if Earth Hour did not happen, the green line is what I would expect to see. (This is only a first approximation using the data available - you can argue that energy patterns for Saturday and Friday are different, but then you would have to get information for previous Saturdays to compare)

So with this assumption in hand, the difference between the green and red curves, integrated to get a number in energy, gave a savings of 13.1 MWh within that hour.

3) Interpretations. This is where things get a bit waffly. Borneo Bulletin says we made a 'big drop' during Earth Hour. How big is big?

Again, by looking at the graph, the power hovers around 450 MW at this time of the day. so in 1 hour, the total consumption is about 450 MWh.

In Section 2, I highlighted that depending on what assumptions you use, you end up with a different number.

38.5 MWh savings during that hour is quite good, about 9 % savings. What i'm saying is that even before earth hour, there is already a 4-5% 'savings'.

If you take the estimate of 13.1 MWh, we made about a 3% difference during that hour. So yes, some difference was made from all that effort, just that we have to be realistic as to how much difference we made.

I think the largest contribution of Earth Hour is still in bringing awareness to the people. But this can be a problem if people are celebrating and cheering and following blindly without knowing what they are really up for. The green movement can be too easily politicised, commercialised and abused. Please be careful.

** Thanks to Chee Hui for the discussion and checking through the above concepts **