Friday, 12 July 2013

Potential energy saving in Schools

Energy bills are going up for schools just as they are for us at home. If there are savings to be made then that could mean more money for useful things like books or educational trips for school pupils. But how can you determine where there are savings to be made? There is a surprising amount of useful information even in half hourly meter readings: it is becoming more and more common to monitor use at at this level with AMR (automatic meter reading) systems. My friend Julia Sonander from Letchworth met with Hertfordshire County Council to discuss how to reduce energy use in community buildings. They decided to focus on schools and Julia has analysed one year’s worth of gas AMR data from 13 schools. She found a huge range in gas consumption per pupil between schools and some interesting patterns of use through the year and through the day.

I’m not going to name the schools concerned because this data is not publically available, but I can show you patterns from the charts.

The average gas usage over the year was 1000 kWh/pupil but this ranged from just 100 kWh/pupil to over 2500 kWh/pupil. In fact, for the two lowest users Julia suspects the AMR is not working correctly so let’s say the range is 500 to 2500 kWh/pupil. That is still a factor of five difference. Some of that difference is due to the varying heat leakiness of the school buildings but not all.

Since gas is used mainly for heating and there is little heating demand in summer, plus most schools are closed for August, you would expect very little gas use in the summer time. However, that does not always happen. Here is a one school which shuts down successfully in the summer, and another which does not.
This school uses hardly any gas in July/August.

This school used a good deal of gas in July/August – about half as much as in April.
Also, most schools are not used much at weekends so they should need much less heating then. Julia looked at a month which included a half term holiday as well as showing the weekday/weekend pattern. Here are two profiles: one shows the holiday and the weekends very clearly. The other does not. The second chart shows about 1600 kWh/day use during the half term week. 1600*5 days * 3.5p/kWh comes to £280. Maybe there was something going on at the school which needed heat – but did it really need heat through the whole school?
This school uses less gas at weekends and during half term.

This school usually uses less gas at weekends but there is no reduction in half term.

Finally, here are some sample days: one weekday and a Sunday in each case. The first school uses very little gas use overnight or on Sunday.

The next chart shows a school (the third highest user) heating 24 hours on the weekday. On Sunday it used less but only during the daytime. 

This school shuts down overnight but comes on with heating at one or two in the morning, which can’t possibly be needed. Even on Sunday, it has heating during the early morning and then shuts down for the rest of the day.

These charts show how gas savings could be achieved with better control of heating in the schools monitored, even with basic programmable timers. The requirements are quite simple and could save most schools hundreds if not thousands of pounds each year.

  • Separate timers for weekdays and weekends.
  • Shut off in the late afternoon until the next day – but with an override for a few hours in case there is an event on.
  • Avoid coming on unnecessarily early in the morning (ideally with an optimum start system that gauges how long it will take to warm up the premises depending on the weather.
  • Adjust the controls during the holidays.

Julia wrote a report with her findings and sent it to each school, but she got no response at all from 11 of the 13. Only one school was enthusiastic and receptive to her recommendations. She went to visit them to discuss possibilites.  As well as adjustments to the heating controls she suggested an activity for the school’s eco club to see how temperatures vary across the school on a day when the heating is on. If there are any areas that are warmer than needed then the thermostatic radiator valves could be lowered in those rooms. There are lots of other ways that schools can save energy too. There are useful resources for this on the Ecoschools website.

Julia points out that even though there are useful money savings to be made it is hard to find the person responsible to contact in each school. As with any tool, monitoring with AMR has a cost and it is only worthwhile if it is used rather than ignored.

Julia only looked at gas use, because it turned out the AMR had not been working properly for electricity in most of the schools. A similar analysis could reveal interesting patterns and savings in electricity use. Also these simple methods can be applied to offices and shops and many other commercial and public buildings.

1 comment:

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