Hi All
We have a number of clients asking us to predict energy consumption so that they can choose the best supply tariffs.
Does anyone have any experience doing this? How reliable are the results in the real world? Should a margin be added, and if so how much?
Or is there a better approach?
Wasted
Using SBEM results to choose supply tariffs
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Wasted Energy
- VE Graduate
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- Location: UK NW
Re: Using SBEM results to choose supply tariffs
Hi,
I don't think I'd use SBEM results for any study of this nature really, it's just too simplistic (although having said that the calculated loads are accepted for a BREEAM ENE credit calculation so obviously some authorities have faith in it). The limitations here are in our range of inputs (simple systems, generic thermal templates, standardised monthly solar gains etc) and this applies to a DSM such as Apache as much as an SBEM.
To get any meaningful result out you'd want to model this as an ApacheSim model entirely outwith the NCM framework so you can opt to include as much detail in your constructions, systems, thermal templates, profiles, links to SunCast, MacroFlo in the real Building model.
CIBSE started to address this in TM54 http://www.cibse.org/knowledge/cibse-tm ... ormance-of and IES also picked hti sup and joined the discussion with some faculty events and a roadshow http://blog.iesve.com/index.php/2014/10 ... mance-gap/. We are developing tools to help improve the precision and reality of models, model calibration coudl be a big topic and VE is being aligned to some of the new developments that you can already access http://www.iesve.com/software/cloud-solutions/ergon although some of this may be a massive jump from SBEM and is targeted at those who are already monitoring aspects of the real building performance so you can calibrate the model against the measured data and include this as more accurate data inputs for the simulations as well.
Beyond the software we have a wealth of experience in house and can offer a range of services in this area through our Consultancy http://www.iesve.com/consulting#building-operation
Ultimately it's up the energy modeller and client to discuss how deep you want to go but when discussing real building performance and predictions then both parties have to be fully aware and in agreement of what the results will represent and what they can influence in terms of your design decisions.
Phil
I don't think I'd use SBEM results for any study of this nature really, it's just too simplistic (although having said that the calculated loads are accepted for a BREEAM ENE credit calculation so obviously some authorities have faith in it). The limitations here are in our range of inputs (simple systems, generic thermal templates, standardised monthly solar gains etc) and this applies to a DSM such as Apache as much as an SBEM.
To get any meaningful result out you'd want to model this as an ApacheSim model entirely outwith the NCM framework so you can opt to include as much detail in your constructions, systems, thermal templates, profiles, links to SunCast, MacroFlo in the real Building model.
CIBSE started to address this in TM54 http://www.cibse.org/knowledge/cibse-tm ... ormance-of and IES also picked hti sup and joined the discussion with some faculty events and a roadshow http://blog.iesve.com/index.php/2014/10 ... mance-gap/. We are developing tools to help improve the precision and reality of models, model calibration coudl be a big topic and VE is being aligned to some of the new developments that you can already access http://www.iesve.com/software/cloud-solutions/ergon although some of this may be a massive jump from SBEM and is targeted at those who are already monitoring aspects of the real building performance so you can calibrate the model against the measured data and include this as more accurate data inputs for the simulations as well.
Beyond the software we have a wealth of experience in house and can offer a range of services in this area through our Consultancy http://www.iesve.com/consulting#building-operation
Ultimately it's up the energy modeller and client to discuss how deep you want to go but when discussing real building performance and predictions then both parties have to be fully aware and in agreement of what the results will represent and what they can influence in terms of your design decisions.
Phil
IES Worldwide Technical Support
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Complex Potential
- VE Expert
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Re: Using SBEM results to choose supply tariffs
Yep, I'd second what Phil is saying.
You should never present SBEM model outputs as indicators of true energy in use. As a general rule, SBEM and even DSM models tend to under estimate true energy consumption by a factor of about 2 or 3 due to the National Calculation Methodology.
TM54 is a good guide to setting up a bespoke model to create a more realistic estimation but make sure you caveat any results or reports to make it very clear that it is a prediction, not a guarantee and that the client publishes or uses the information at their own risk. I get very uneasy about this sort of crystal ball gazing, especially when clients start talking about tenant energy bills....
You should never present SBEM model outputs as indicators of true energy in use. As a general rule, SBEM and even DSM models tend to under estimate true energy consumption by a factor of about 2 or 3 due to the National Calculation Methodology.
TM54 is a good guide to setting up a bespoke model to create a more realistic estimation but make sure you caveat any results or reports to make it very clear that it is a prediction, not a guarantee and that the client publishes or uses the information at their own risk. I get very uneasy about this sort of crystal ball gazing, especially when clients start talking about tenant energy bills....
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Wasted Energy
- VE Graduate
- Posts: 93
- Joined: Thu Sep 10, 2015 5:58 am
- Location: UK NW
Re: Using SBEM results to choose supply tariffs
Yep.
Since the original post I've read TM54 and also the Carbon Trust publication 'Closing the Gap'
https://www.carbontrust.com/media/81361 ... design.pdf
This is not only an eye-opener in regards to the size of the gap, as CP points out, but also the limitations and strengths of different modelling methodologies, see Fig 7.
So I'm going to try a TM54 analysis using some DSM data as suggested in the TM.
Cheers
Wasted
Since the original post I've read TM54 and also the Carbon Trust publication 'Closing the Gap'
https://www.carbontrust.com/media/81361 ... design.pdf
This is not only an eye-opener in regards to the size of the gap, as CP points out, but also the limitations and strengths of different modelling methodologies, see Fig 7.
So I'm going to try a TM54 analysis using some DSM data as suggested in the TM.
Cheers
Wasted