Energy saving & comfort

My name is Shinya Ogata and I work in the Environmental Section at PTM. I mainly work on computational flow dynamics, which involves the use of software to simulate heat environments.

Cooling system temperature settings

Recently there are an increasing number of offices increasing the temperature setting on their cooling systems. By increasing the temperature setting we can certainly save energy however, people are likely to start feeling the heat? One obvious answer is to use a desk fan. You soon feel cooler when a fan is blowing directly at you, but how comfortable is it?

“PMV” – an indicator of comfort
PMV, short for Predicted Mean Vote, is an index that is widely used in architecture to indicate levels of comfort. A prediction of the level of comfort is made based on data collected from experiments carried out on 1000 subjects. The index has 7 levels from -3 (very cold) to +3 (very hot), and the closer to zero the indicator is, the more comfortable it is. To work out the PMV for a certain space, 6 different conditions need to be determined: temperature, relative humidity, wind speed, mean radiant temperature, metabolic rate and amount of clothing.

Cooling system temperature settings & comfort
Let’s compare comfort levels at different temperature settings of 26°C & 28°C. The graph below shows the relationship between air temperature, air speed, and PMV. Point 1) shows the setting at 26°C with no fan, while point 2) shows the setting at 28°C with a fan. When the fan is used, the air speed is about 0.6m/s. Look at the PMV in each case, the value for point 1) is between 0 to 1, while that for point 2) is very close to 0 which indicates the most comfortable environment.

Therefore, when a fan is used and the air speed is about 0.6m/s and blowing directly at you, whether the setting is at 26°C or 28°C, you can achieve comparable levels of comfort.

Energy saving and discomfort
There is the idea that energy saving is something that creates discomfort and is something to be endured however, as I explained above, with a little ingenuity improvements in both energy saving and comfort are possible. Here, I’ve used the use of fans as an example however, there are many other possibilities that could be devised. There’s no reason why we can’t all work towards creating comfortable environments and saving energy!

Shinya Ogata

Environmental Group

Visit our website at http://www.ptmtokyo.co.jp/

2011-8-1

The Impact of Energy Saving Measures

The Energy Saving Team, formed by volunteer engineers, tried to determine the actual results and impact of energy saving measures, rather than just putting into practice a typical action list such as you may find anywhere.

I’d like to introduce some of our findings, so that anyone can refer to them, and of course to help reduce electrical power demand.

1. Energy Saving Poster

To help raise awareness of energy saving, the first thing to do was create a poster which showed easily implementable measures. We displayed this throughout the office.

2. Assessing the working environment

Firstly we thought it important to assess the working environment. For this we used the proprietary SAP software to measure, created by the Japan Sustainable Building Consortium. By gathering responses to a questionnaire posted online, we were able to make an assessment of intellectual productivity based on factors that affect the office environment, such as lighting, acoustics, heat, air, space and IT. We plan to send out this questionnaire, several times while energy saving activities are being carried out.

3. 50% reduction in lighting levels

One of the two fluorescent tubes was removed from each lighting fixture, reducing lighting levels from around 700-800Lx to about 300-400Lx. The standard for lighting levels for offices in Japan is 500-750lx, while in the UK it is 300-500lx, so lighting levels in Japan tend to be very high. So how about working in lighting levels of 300-400lx? I don’t feel it is particularly dark however, some employees occasionally use their desk lights. Actually this makes for a good set up that provides ambient lighting with some additional lighting for more involved tasks.

By making these changes, we have achieved a saving of 4kW per hour in the office.

4. Determining the A/C temperature setting

This is important however, the ambient temperature doesn’t always correspond to the temperature setting. This point was hammered home by taking temperature measurements in the working environment. So we are trying to find a temperature setting that will keep the office at about 28°C (which is still considered a little on the high side). What does it look like when we compare the temperature setting and the actual temperature measurement where people are working? It seems that the results vary in locations where the sensors or the A/C units are installed.

A textile ventilation duct on the ceiling. This was installed a few years ago to create a uniform indoor temperature.

5. A/C shutdown timer

The remote controllers for recent A/C systems have a weekly timer setting. The system in our office has this function so we set the timers to shutdown at 19:00. Shortly, it was easy to see the impact. Our staff didn’t notice that the A/C units had been switched off from 19:00, and the subsequent change in temperature was slow, even though a large number of A/C units were shutdown. If it starts to feel uncomfortable people can take it upon themselves to restart the units near them, but are required to ensure they are turned off when leaving the office.

Care is needed in deciding whether to switch off the cooling during lunch, as that is just before the peak period.

6. Raising Awareness

How easy is it to grasp just how much energy you are using? Well, it’s not easy – unless you have real time power monitoring! We are a tenant so we had to get the agreement of the owner and building management company, but we were able to install meters in the risers and on the roof where the building services equipment is installed.　Energy measurement is also part of our business, but the installation of real time measurement brought new challenges, such as measuring the voltage.

We installed a display panel in the office, which is pictured below. A graph displays the real-time power monitoring data. To be easily understandable by everyone, the graph only displays demand. The expected demand based on the previous year’s monthly power demand and energy saving goals are displayed on the panel.

Additionally, fresh air temperature and humidity meters are installed, and the aim is to shutdown the A/C units and open the windows in periods when the air outside is cooler. This was actually carried out for about 2 days during July.

7. The future

Various power saving activities shall be carried out from now on. We shall also be exchanging opinions with design office colleagues, and there are also energy saving ideas which we had not previously considered.

I’ll tell you about them next time.

Shuji Imura

http://www.ptmtokyo.co.jp/

Energy Saving Tips

2011-7-26

My name is Akira Katayanagi and I'm an electrical engineer in the International Projects Group. With the recent earthquake, tsunami, the nuclear disaster at Fukushima and the impact this has had on energy supplies, it is more important than ever for everyone in Japan to make efforts at energy saving.

Energy saving
If everybody in Tokyo (population about 13,000,000) switched off lighting in unused rooms (with a 60W bulb), we would be able save about 780MW per hour.　To give you an idea of how large this figure is, it is about 16 times the equivalent power consumption for 1 professional baseball game held in Tokyo dome, or equivalent to lighting power for a single family for 160 years! It is something we should keep in mind: small scale energy saving measures by individuals lead to large scale energy savings.

As a group of engineers working at a building services consultancy, we are specialists in energy management and will be posting advice on how to save energy, and we are sure we can succeed in meeting energy saving requirements this summer.

Energy saving tips
1 Goal
It is important to set energy saving targets. The goal for this summer is a reduction of over 15%. This target value, announced by the Ministry of Economy, Trade and Industry, is calculated based on analysis of this year’s electrical power demand and supply balance.

2 Analysis
Electrical power usage varies. While saving energy is important, we want to save energy while maintaining comfort to avoid any drop in productivity, so it is important to understand the breakdown of energy consumption in order to make effective savings. Lighting, power outlets, air-conditioning, servers, server room air-conditioning etc., we need to analyze what proportion each application accounts for, and it is important to consider energy saving by first focusing on whichever section has the highest consumption.

3 Monitoring
To raise the energy saving awareness of employees, the energy consumption for each group is measured and announced in the company each week or month, and a comparison of last year’s and this year’s energy consumption helps to add a measure of satisfaction. However there are many companies that say, “energy readings are not being taken at all in any group so it’s difficult to raise monitor”, but recently there is a diverse range of metering equipment available which is comparatively cheap to install. In fact, our company had not been monitoring consumption but this month we managed to set up a hand built monitoring system.

4 Energy Saving Patrol
It is easy to take effective measures such as reducing lighting by half and setting the cooling at temperature at 28°C. However, it’s important to remember that simple things like forgetting to switch off lighting and air-conditioning while making efforts like these can still lead to disappointing results. However, this summer we have instituted an “Energy Saving Patrol”. It may sound a little funny and at first I thought, “Hey we’re not a bunch of school children… ”. The patrol simply designates members to check the situation in the office and switch off any unused lighting or air-conditioning. However, this is one of the most basic kinds of energy saving measures.

Akira Katayanagi,
International Projects Group

http://www.ptmtokyo.co.jp/