Energy Efficiency: Picking up the watermelons (and why it hurts if you don’t)

16 Jan 2015 by Peter

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You’ll often hear people in the energy efficiency game talk about “the low hanging fruit” – you know, the really obvious energy savings that apparently always get picked up first.  Well, the subject of this blog post simply couldn’t hang any lower – it’s the watermelon of energy saving opportunities.

In the past we’ve discussed on this blog the issue of buildings not being properly tuned for public holidays, often with the result that parts of the building, the automated parts, will fire up even though the building is empty with a resulting waste of energy and money.

When we think about the different types of efficiency issues and opportunities that exist within our buildings, this type can broadly be placed in the “operational” bucket, by which we mean savings that can be achieved by tweaking or tuning the existing building systems.  In the example above, that would be updating the schedule on the HVAC controller to include public holidays.

There are a couple of other buckets into which we can categorise energy efficiency opportunities as well 1) the “building upgrade” bucket, meaning you’re investing in new technology such as LED lights, solar or a chilled beam HVAC system, and 2) the “behavioural change” bucket, where energy savings are achieved simply (and I use that term loosely) by encouraging building occupants to alter their behavior in such a way as to reduce energy consumption, an example being turning off lights in meeting rooms when people are finished with them.

So when we consider the operational own-goal of firing up your building unnecessarily on a public holiday, it’s worthwhile considering this in the context of other energy saving initiatives a building owner might be spending money on and how the energy waste/savings stack up.

To illustrate what I mean, let’s have a look at some real data. The profile chart below shows the electricity demand for one of our customer sites, a medium sized office building in Sydney, over Christmas week 2014. Remember that Christmas Day fell on a Thursday and Boxing Day, also a public holiday, on the Friday.

weekly profile chart

The first thing you notice is the building was using significant amounts of electricity during those two public holidays. Given the building was empty during that period, you would expect energy use to mirror that of a typical non-working day (Saturday and Sunday, for those struggling to keep up).  As I’ve already made reference to in the introduction, the cause in this case is the automated HVAC system behaving as though those were two normal working days. Why? Because nobody remembered to tell it any different.


Let’s dive a little deeper into those numbers. The average daily consumption for this building on a typical non-working day during 2014 was around 900 kWh. The average daily consumption for each of the 10 public holidays* for the year, including the two days shown here, was 1,900 kWh meaning that on a typical public holiday the building uses an additional 1000 kWh. Across the 10 public holidays in 2014 this amounts to 10 MWh of wasted energy for the year.

To put that in context, the building has a 20 kW solar PV array that on average generates around 84 kWh of electricity each day, or 30.8 MWh during calendar year 2014 (we know this because we’re monitoring it).  At the time of writing that systems costs around $25,000 to install. When we look at it in those terms, around 33% of the total annual generation from that solar array has been wasted on just 10 days of operational carelessness. See chart below.  To think of it another way, by failing to act on a simple operational efficiency opportunity that would require an hour or two of time from a skilled technician, you’ve indirectly increased the payback period on a significant solar investment by 1/3.

solar pie

Graphic: Around 1/3 of annual solar generation is wasted

Wrap up

Whilst investing in building upgrades and onsite generation is great, and clearly there is an important contribution that these projects can make, doing so in the absence of basic operational discipline is pure madness.  It’s akin to handing over your hard earned cash to your local gym so you can slog out the kms on their treadmill, then stopping at MacDonalds on the way home for a supersized calorie hit.

Despite it seeming so obvious, many buildings are still wasting large amounts of energy and money for the dumbest of reasons. With the right tools and skills, these issues are easy to detect and easy to fix, so please, pick up those watermelons everyone.

* http://www.industrialrelations.nsw.gov.au/oirwww/NSW_public_holidays/NSW_Public_Holidays_2014-2016.page


One response to “Energy Efficiency: Picking up the watermelons (and why it hurts if you don’t)”

  1. Jamie Press says:

    This is a great piece. I dropped by the work office during the Christmas break and was gob-smacked the air con was blasting away in our office at an ice 22 degrees C.

    It only occurred to me then that every work day regardless of office shut down/public holiday, the A/C is running and cash is being burnt.

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