For a comprehensive CIBSE TM54 assessment, the spirit of which is to capture a much more detailed and accurate picture of a building's operational energy, you should be using ApacheHVAC. This allows for a granular, plant-level modeling of building services, which is necessary to truly align with the detailed requirements of TM54. The techniques outlined in this post are useful for understanding the different components of auxiliary energy within ApacheSim but should be considered a starting point, not a substitute for the more detailed modeling required for a complete TM54 assessment.
If you're used to modelling and simulating buildings to show compliance with the Building Regulations and generating EPCs, you may not be used to the level of detail required for CIBSE TM54 assessments. One area where this is particularly evident is in the calculation of auxiliary energy consumption.
TM54 requires users to carefully consider auxiliary energy consumption and to use a detailed and accurate building model to capture it. Because you are using ApacheSim away from VE Compliance this uses the 2006 UK Compliance methodology which requires more thought on your inputs.
These options are found on the Aux Energy tab in Apache Systems and are explained further in the following FAQ: https://www.iesve.com/support/faq/pdf/A ... Method.pdf
The building level variable “Ap Sys aux + DHW/solar pumps energy” is the total sum of system energies associated with all fans pumps and controls. It is made up by the sum of 5 separate components that make up the auxiliary energy picture. I’ll go through an example for 2 zones in a test model to illustrate how that variable is calculated so that you can determine whether or not the inputs you have set are reasonable.
1. AEV (Auxiliary Energy Value)
The zone has an area of 100m2.
The AEV value is applied continuously as controlled by the highlighted profile.
The system has an AEV value of 1.002 W/m2 which is applied to all spaces served by this system.
The resulting plant energy consumption for this space is 1.002 W/m2 x 100m2 = 100.2W
2.) Ventilation SFP
As you can see in the system screenshot above, as well as having an AEV an SFP of 3.6 W/l/s has been set. In the screenshot below you can see the space has a supply rate of 80 l/s. This results in a supply fan power of 3.6 W/l/s x 80 l/s = 288W
3. Extract Ventilation SFP
This function is typically used to represent the auxiliary energy from an exhaust fan and is in addition to the previous function. It would commonly be used for modelling energy associated with an extract fan in a toilet where the extract rate exceeds the supply requirements.
This option was not used in this test case.
4. DHW Pumps Energy
This value would be expressed as a total power instead of being apportioned based on floor area. This again however has not been applied in this model.
5.) Solar hot water pumping Energy
As above this has not been applied in our model
In our test model we have two rooms, each with their own system. Room 1 uses the system above so the Total Auxiliary Energy is equal to AEV + System level SFP which gives 100.2 + 288 = 388.2W
Room 2 uses the following system with "Use SFPs" as the method so the Auxiliary Energy is just based on the system SFP which is as above, 288W
In our model only functions 1,2 (Aps Sys Aux) have any value associated with them and 3, 4 & 5 (Extract, DHW/Solar pumps
Energy) have no energy associated with them. As demonstrated above the zones will have a total of 388.2 + 288 = 676.2W of plant energy associated with it
So viewing the results in VistaPro the total “Ap Sys aux + DHW/solar pumps energy” you'll see it equals this value.
