Results of summer time energy saving - part 2

This is Hokuto Nakamura from the Environmental group.
Following on from Shuji Imura, I’m going to evaluate the energy saving measures we took over the summer, based on the data.

Areas covered
1) Real time monitoring
2) Air-conditioner tuning
3) Lighting/office equipment

1) Real time monitoring



Monitoring panel

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

We set up a monitoring panel to help with the implementation and evaluation of our energy saving ideas.

 

 Peak power consumption
The importance of understanding peak power this summer was commonly acknowledged in Japan however, when the peak occurs is not so clear as electricity is invisible. Based on experience our engineers were able to make a reasonable guess however, it is difficult to judge accurately to within two hours. This time we were able, by real time monitoring of power usage, to take action such as switching off lights before peak power usage was reached.
Our peak power usage this summer occurred at 11:30am on August 12th at 38.3kW (35% lower than the previous year). This shows the results of the effort put into saving energy this summer, and while it is not a result of the monitoring, it puts a numerical value on the power saving activities carried out and there is a connection to the improved awareness of energy saving.

*Assumed values based on meter reading and outdoor temperature changes.

 Energy saving activities utilising monitoringNext, we opened windows to successfully monitor the outside air temperature and humidity (only for a couple of days). On July 21st 2011, a large typhoon hit Tokyo and the surrounding region. On the days before and after (21st, 22nd) it was obvious that the outdoor air temperature was rapidly dropping, so we shut down as many of the air conditioners as possible and tried to cool the office by opening the windows. The indoor temperature tended to be higher than on the 20th when the cooling system was operated as usual however, there was a 25% reduction in electric power usually required for one day’s cooling. It is difficult to forecast, but it was possible this time with the monitoring system we set up. This will be especially useful in April and may when the temperature is not so high.

Period of fresh air cooling in 2011

 

2) Air-conditioner tuning

Imura-san (who wrote the previous blog post) led efforts to review all air conditioner remote controller settings. There were two main improvements.
   (1) Setting the weekly timer to switch off at 19:00, with the option to turn them back on.
   (2) Based on a review of temperature settings and temperature sensors which were 27°C it was decided to put them at 28°C.

I’m not going to go into all the details here, but here is a month by month comparison of last year’s metering data and data gathered this year.

Comparison or air conditioning power

 

Compared to 2010, we achieved an energy saving of about 34% for air conditioning. This value came as quite a surprise to our engineers and gave serious pause for thought about our previous lack of consideration. The results of monitoring showed that about 2% of cooling came from fresh air, shutting down the air conditioners at 19:00 accounted for a reduction in power consumption of about 10%, and the review of temperature settings gave us a 22% reduction. If fresh air cooling is about 2% and shutting down the air conditioning gives a power reduction of 10%, then the change in temperature setting gives a reduction of about 22%. It is easy to get complacent about controlling air conditioner settings, so everyone needs to consider it carefully.

3) Lighting /office equipment power

Lighting
 One way of saving on lighting power was to reduce the number of lighting fixtures in use. However, you need to be careful how you do this or you might well end up using more power. Our approach was that if you didn’t miss one of the light units when turned off, then it was deemed a waste of energy and disabled. By using illuminometers and asking staff how they felt about the light levels, we were able to select which units to disable and determine the best arrangement. Maeyama-san will go into the details in another post.
About 100 fluorescent lighting tubes were removed (about half ), so using the following rough calculation:

 40　[W]   ×   100　[units]   =　4,000 [W]   →　4.0[kW]

 The above calculation gives us a saving of about 4.0kW. Prior to disabling some light units, lighting power was about 9.0kW, which is an energy saving of about 45%.

 Office equipment power  Reducing the brightness of desktop displays is one good way of saving power with office equipment. The graph below shows our results. Normally it is possible to save about 10W by reducing the brightness from the display default. This also has a beneficial impact on air conditioning power consumption as less heat is given off. However, it shouldn’t be reduced to the extent that it causes eye strain.

The following calculation shows the power saving for 40 people in the office

10　[W]  ×  40　[persons]   =　400 [W]  or  0.4[kW]

 On top of this saving of around 0.4kW we made a real effort to switch off monitors when not in use. Compared to 2010, we achieved a 32% reduction in power consumption. The savings were from 25% lighting and 7% office equipment.

Conclusions In comparison with last summer, this year we achieved energy savings of 34% (over a period of 2 months). The figure below shows a breakdown of power saving, and it is clear that lighting (38%) and air-conditioning adjustments (33%) make up a large portion of savings.

Breakdown of power reductions

 As a result of our efforts we achieved a reduction of 35%, and the amount of power saving between August and September was 34%, so while this is commendable, I think our previous power usage calls for serious reflection. We need to look further into ideas (such as heat stored in the building structure etc.) that we didn’t put into practice this time, and we also need to think about energy saving during the winter. I’d be happy to hear from anyone who would like to put these energy saving ideas to the test.