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Miscalculations in Ecodesigner (shipped with ArchiCAD 17)

Anonymous
Not applicable
This pertains to EcoDesigner's Operational Profiles. In my case I have a building that is only open two-days per week for 9 hours per day. When sizing the heat recovery ventilation system and defining its daily schedule, EcoDesigner shows correctly that the vent system will be operational for 936 hours for the year.

All good so far. However, when I define a corresponding Operational Profile for the building (two days per week for 9 hours per day) EcoDesigner calculates the annual hours of operation as 2,496 hours which is patently incorrect. This miscalculation overstates the usage of the building by over 200%, which translates into much higher energy consumption (kWh/cubic foot/annum) than should be the case.

The algorithm doing the calculation of operational hours per annum need to be looked into and fixed.

BTW I use kWh/cubic foot/annum because kWh/square foot/annum can sometimes be misleading. Higher ceilings (10ft-14ft) in a small, 3,000 sf community building will yield a different energy consumption profile than a 3,000 sf building with 8ft ceiling plate for the same number of occupants.

Any thoughts or perspectives on what I think are miscalculations in EcoDesigner's Operational Profiles would be much appreciated.

Thanks
15 REPLIES 15

gpowless
Booster
Don't get too out of shape.

Ecodesigner is not an energy-compliance tool. It is merely a pre-design estimation tool.

On the other hand, all energy-compliance apps are simply estimations in the first place. What we think is accuracy has little bearing on the real-world use of the building. And at the end of the day while we might come in within a few thousand watts it is nothing but a guess masked with calculations & flowery output.
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James B
Graphisoft
Graphisoft
Hi Phil,

Just checking if you've reviewed this dialogue in the Building Systems?
Technical Product Manager, Graphisoft

Anonymous
Not applicable
James B:

Thank you. Indeed YES I have indeed used the Building Systems Dialog for the heat recovery ventilation system operating hours. When I tie the HRVS to the two-day per week, 9 hours per day I get the correct 936 hours of operation. When I go to the Operational Profile and define the same two days per week, same 9 hours per day for occupancy, I get 2496 hours; an incorrect calculation which overstates the potential energy consumption.

I know that actual building use is different from simulation. However, my long years of experience in the field of simulation (system dynamics in particular) dealing with highly complex public health models, tells me that clients want credibility and accuracy. If an arithmetic error of the kind I think I've identified in EcoDesigner and that I thus far cannot explain, then the whole purpose of energy evaluation becomes pointless and frustrating exercise. Moreover the credibility of using BIM models can be seriously compromised in the eyes of clients who can quite readily detect the arithmetic errors that I think I've identified.

I'd be delighted to chat with anyone on the Graphisoft team who thinks that I'm wrong and am missing a critical aspect of the Ecodesigner model

I am also aware that Ecodesigner is not EcoDesigner Star. I was on the beta teat team for EcoDesigner* and am anxiously awaiting its release. Even so, EcoDesigner needs to be accurate even if it is not extensive in its compliance with a variety of energy evaluation systems and standards out there.

Below are some screen shots of what I'm seeing

Anonymous
Not applicable
Gpowless:

I'm concerned about the credibility of EcoDesigner in the eyes of clients. See my reply to James B. on this.

Phil
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ArchiCAD 17

Karl Ottenstein
Moderator
pallsopp42 wrote:
Below are some screen shots of what I'm seeing
Don't see your screenshots. You can attach one per post, and there is a size limitation of 256kb as I recall.. so you'll have to lower the jpeg quality, use gif, etc. Or provide links to an external photo hosting site.
One of the forum moderators   •   AC 25 USA and earlier   •   MacOS 11.6.5, iMac Pro

Anonymous
Not applicable
Karl:

Thanks - I'll reduce the file sizes later today and re-post

Phil

Anonymous
Not applicable
Karl:

per my previous note, I have - hopefully - attached two screen shots that show the large discrepancy between a 2-day-per-week; 9-hour day operational profile for the building's energy recovery ventilation system and the Operational profile of the building (occupancy, temperature ranges etc.).

Anonymous
Not applicable
And here's the other screen shot of the energy recovery ventilation system profile showing the correct 936 hours of operation per year.....

Barry Kelly
Moderator
pallsopp42 wrote:
Karl:

per my previous note, I have - hopefully - attached two screen shots that show the large discrepancy between a 2-day-per-week; 9-hour day operational profile for the building's energy recovery ventilation system and the Operational profile of the building (occupancy, temperature ranges etc.).
I don't know much about Ecodesigner but there is nothing in this operation profile that tells it that it is only for 9 hours per day.
2 x 24 x 52 = 2496
Maybe Ecodesigner doesn't allow for hourly usage in an operation profile but only daily usage.

Barry.

One of the forum moderators.
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Anonymous
Not applicable
Barry:

I set the hours of operation per day as 9 and the number of days of operations as 2 for the whole year (9x2x52 = 936). Nothin particularly extraordinary about this

The screen shot show Wednesdays and Sundays for 9 hours each day.

My Operational Profile containing the temperature ranges, occupancy, equipment loads etc is also set to 9 hours per day for only Two days per week - Wednesdays and Sundays.

I've attached a screen shot of the daily schedule to address your point.

Hope this clarifies the situation for you. 9hrs x 2 days per week x 52 weeks = 936 hours of operation.

Phil

Anonymous
Not applicable
Barry:

Totally different topic - Perth WA. What a fantastic city that is. My best man at our wedding whom I've known for very many years - Steve Brown - lives in Perth - the Shenton Park area. He's an architect whom I've been trying from time to time to persuade to switch from Autocad to ArchiCAD.

Phil

Barry Kelly
Moderator
Your kidding - Steve Brown from Shenton Park!
Never heard of him.

As I say I don't know a lot about Ecodesigner but I think your calculation might still work out.
I'm not sure why it shows the 2496 hours usage.
There is a 24 hour time span but you are setting the min/max temperatures as well as lighting etc. for only a 9 hour period.
So my guess is it will calculate that correctly and ignore the rest of the day.

The only way to check for sure is to run your calculation based on what you have set up.
Then change it to say 12 hours in the day and see if the calcs increase.

Barry.

One of the forum moderators.
Versions 6.5 to 25
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Anonymous
Not applicable
Barry:

Thanks - as I've always joked with Steve Brown that he's well known in concentric circles (an old Goon show reference).

But to EcoDesigner. Per your suggestion, I tried a few different daily schedules to see what the internal algorithms produce as far as hours of operation per annum. No change. The calculations assume a 24 hour occupancy.

Somehow I think there's an errant algorithm in the portion of the code behind the Operational dialogue that is producing the wrong hours of operation per annum.

Best

Phil

Anonymous
Not applicable
pallsopp42 wrote:
But to EcoDesigner. Per your suggestion, I tried a few different daily schedules to see what the internal algorithms produce as far as hours of operation per annum. No change. The calculations assume a 24 hour occupancy.
This is not correct.

If you create two different daily schedules (one with no temperature range and one with specified low and high temperatures) and properly assign them to the thermal blocks - the calculations will differ and, no, calculations do not assume 24 hours of operation.

What you are struggling with is the fact that EcoDesigner shows 2000+ hours of operation (poor wording, I agree), but think about this number as a NUMBER OF DAYS your operational profile is in effect, not the number of hours that your systems are running.

The number of hours your systems are running are dependent on many factors within operations profile (temperature control, occupancy, if you have bodyheat turned on, lighting heat emissions, equipment, etc.) as well as outside factors like solar gain and heat transfer between blocks.

Basically, what you are referring to as a bug does not appear to be one in my opinion.

Anonymous
Not applicable
EcoBoger:

Well, I guess we have to differ. I think there may be a bug.

When a completed operational profile (occupied with systems running and thermal blocks properly allocated) is defined as 960 hours a year yet another calculation in the same application (Ecodesigner) sets the hours of operation per annum as 2496 for that same daily operational profile, then there is something seriously amiss. The number is defined in EcoDesigner as the number of hours per annum NOT the number of days the operational profile is in effect as you suggest.

Hours of operation: 2 days per week at 9 hours per day for 52 weeks per year = 936 hours of operation.

If it is not a bug, would you - or someone - please explain to me why the defined hours of operation (936 hours per annum) calculate out to be 2496 hours within the same application and for the same operational profile??

I continue to be very curious about this and the discrepancy makes no logical sense based on the information I have and the feedback thus far.

If I'm off base then perhaps I'm misinterpreting nomenclature within EcoDesigner e.g. "Days of Operation." If this IS the case, then EcoDesigner needs to make it crystal clear to users how it is interpreting the operational profiles. Thus, when a 936 hours per annum of operation turns into 2496 hours of operation for the same profile, this difference needs to be explained as well as how calculations of energy usage are not being compromised by this apparent discrepancy.

Thanks

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