The energy consumed within our Domestic Hot Water Services (DHWS) is all too often overlooked. In my opinion we typically fail to see it for the opportunity it is. All too often we believe its energy consumption….
“Is, what it is”………….My god I hate that expression.
Modern buildings can tell us the energy consumed by our DHWS but because the energy consumed is usually less than that of our heating system. We are guilty of ignoring it. In my view DHWS is the poor relation to building heating costs and this is an oversight.
When I worked for a Local Authority, I had a long running argument with one of the Swimming Pool managers. The swimming pool had a 3000ltr DHWS Storage tank.
During an Energy audit I asked the question of how many showers were taken at the swimming pool. Following some time, the swimming pool manager returned to me with the answer of………
“Well Jeremy we have given this a lot of thought and based on the number of swims sold and the amount of club swimming that goes on we think a number of 300 showers per day is a good average”
During my audit I had noted that the hot water storage tank was set to 70c. Armed with these two facts I could now make the challenge and promptly suggested that the set point of the storage tank was reduced to 60c. My suggestion was meant with a glazed look and the words….
“No, we can’t do that Jeremy, Legionella”
This is the typical, get out of jail card answer I have encountered before. Said by the same people who used to say that turning the lights off actually cost more than leaving them on.
Remember those guys?????
To avoid the risk of legionella you either need to ensure that your hot water is stored at above 65c or your tank is turned over at least once a day. Well lets’ do the maths.
300 showers a day multiplied by 5 minutes per shower at a flow rate of 10 ltrs per minute = 15,000 ltrs hot water consumed every day. Which means the storage tank was turning over 5 times a day.
Here was a clear and present opportunity to reduce the set point significantly and achieve an energy saving. Reducing the set point to 60c would have saved just shy of £2,000 per annum.
The beauty of this solution is it required no investment, no training. Just a simple amendment to the controls. 5 minutes work, tops. Satisfied I had done my maths correctly. I took my recommendation to the swimming pool manager who said….
“No, we can’t do that Jeremy, Legionella”
You can imagine my frustration. But I took solace in the fact that there are two definitions of the word crazy. The first. Continually doing the same thing and expecting a different result. The second.. Refusing to acknowledge or take action despite being presented with an over whelming reason for doing so.
Clearly, I was selling crazy!!
At this juncture I will say that I also firmly believe the word “Moron” is incredibly underused. Anyway, that boat has long sailed. So why is DHWS overlooked? Why are we missing these energy saving opportunities
Are we all moron's?
Well one reason for this is that we fail to recognise the relationship between our water consumption and our energy consumption. The reason for this is that Water consumption has long been the poor relation to energy.
Buildings with high levels of water usage may well have high levels of DHWS use and as such will most likely represent some low hanging energy savings.
Time for another example the image below represents the power consumed by a 12kw immersion heater used to heat hot water storage tanks to supply hot water to sinks and basins in rooms in a guest house I recently audited.
Why is the immersion firing 24hrs day? The system supplies hot water to sinks in rooms and sinks in the kitchen. Is the guest house entertaining the personal hygiene fetish annual convention? The data is actually suggesting that the pipe work that serves the system is not lagged.
This means, hot water is coming back significantly colder than it is going out. Even when no one is using it. This is the benefit of being able to provide visible data at an incredibly granular level.
Remember Energy Blog No 2 on the importance of having visible data?
Speaking of personal hygiene. Something else that bothers me about domestic hot water systems is why we need to provide hot water in public toilets? I appreciate it relates to health and safety legislation. However, that particular legislation was passed long before hand sanitising lotion was developed.
When you use a public toilet, you may use the hot water, you may not. You then use a hand dryer to dry your hands. Why can’t public conveniences provide hand sanitation points and save on both the water and the hand dryer consumption.
If hand sanitisers are good enough in our hospital wards, then surely they are good enough in our public conveniences. Whilst the naysayers will remind me that…
“People like to wash their hands, Jeremy”
I would like to remind them that we are clearly at the dawn of a climate emergency, so can we please stop acting crazy and stop wasting energy when we have clearly identified alternative solutions.
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