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Imagine a university campus with 9 buildings or perhaps an office complex.
Each area, only needs heating below a certain temperature, and the demand increases as the temperature falls into winter.
So the start points vary, but the total demand should always be concave, because once heat is needed, more is needed the colder it gets - you can see this illustrated idealistically.
But...
The same applies to individual buildings, or any space that is not completely uniform (when a straight line would be the ideal - the basis of degree-day calculations).
So why is it when we study large district heating systems or small pubs (we visit when we can), that we always see a pattern that is convex.
This is shown below for a large residential site that shall remain nameless.
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We see that consumption or demand has the opposite shape to the one we expect. Low use in summer is excellent (just serving domestic hot water).
When its very cold -5 Celsius demand flattens out (this is the heating failing to respond to actual demand.
The real nightmare is the transition. Heat is only just required, but consumption jumps to nearly 200kW. This is the futile cost of keeping a system warm which is not needed.
On this site total waste is approximately 50%.
No waste in summer, and none in the extremes of winter but as much as 100% waste between the two !
with kWIQly you can look for better shapes too!
