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architecture-building-systems / CityEnergyAnalyst

The City Energy Analyst (CEA)
https://www.cityenergyanalyst.com/
MIT License
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Energy Demand too low TABULA Germany #3619

Open pnguyen-dh opened 5 months ago

pnguyen-dh commented 5 months ago

Describe the problem In the newest version, CEA already implements the data for Germany from TABULA. So I use this database for my simulation, I would expect the energy demand (specific heating demand) should be roughly the same as in TABULA, or maybe about 10-20% different. But after the simulation the building's energy demand are too low, I expect 150 kWh/(m2a) for single family house 1969-1978 (source), but get only about 15-65 kWh/(m2a). I would say that the simulation demand were too good to be true.

To Reproduce If you need the input/output data, I can zip it and send it. I used the standard SFH_F, SFH_NR

Expected behaviour The energy demand should be then higher? Or I actually might miss something.

Screenshots Energy End-use Intensity for District image

Thank you for your support!

ddceruti commented 5 months ago

Hi! Thanks for your feedback and using the database! Can you provide an input file to reproduce (maybe 1 or 2 synthetic buildings)? I would look into it and see if it depends on the TABULA values within the database or some other database parameter.

pnguyen-dh commented 5 months ago

inputs.zip

Hi, here is the input. I also tested the same buildings with the database from CH, and the energy demands are much higher. I also tried to look into the DE database but couldn't find anything special. Feel free to tell me if you need anything else.

ShiZhongming commented 5 months ago

Hi @pnguyen-dh

Thanks for raising this issue. It is very much appreciated as the DE Database is new and needs time to stabilise.

I have also used a random single-family house neighbourhood near Berlin.

For buildings using SFH_F, the heating demand I got was ranging from ~90 kWh/m2 - ~120 kWh/m2, which is rather similar to the reference value of TABULA at 139.5. Please note that in the graph, the heating energy demand calculated is based on a floor area equaling 0.85 X gross floor area, while energy end-use intensity equals this heating energy demand divided by 100% of the gross floor area. This could be one of the reasons that lead to the low normalised results in the graph.

For buildings using SFH_F_NR, the heating demand I got was much lower than that of TABULA, which is as what you had described.

We will need a bit more investigation over this. I am also tagging @ddceruti here. Please share your opinion on this.

Meanwhile, we would like to mention that CEA has been a tool designed for district-scale building energy simulation using simplified building geometries. We would recommend applying CEA for comparing multiple design scenarios or finding patterns when adjusting input parameters.

pnguyen-dh commented 5 months ago

HI @ShiZhongming,

Thanks for your reply. I also tried to change the Hs_ag = 1, and recalculated everything. The number for SFH_F_NR and SFH_F_AR were still too good. I would suggest that, there is some problem with the refurbishment settings, I can see that it was even better than passivhaus.

I'm working on a small project now for district labeling, so I also need to compare the average heating demand in a district, and how good is a building before and after refurbishment, for example. The energy potentials calculation is kind of on point for me. Anyway, thanks for your supporting!

ddceruti commented 5 months ago

Hi, I checked the U-Values of the whole envelope again and I could not find any discrepancies with the reported TABULA values. I found a mistake in the use_type warm water per person: 11.6 ldp instead of the 40 in CH database and 36 % of 121 ldp = 43.6 by the BDEW (https://www.bdew.de/service/daten-und-grafiken/trinkwasserverwendung-im-haushalt/). I will update this and check the database again more throughly next week. Thanks again @pnguyen-dh for your feedback and @ShiZhongming for your reply.

c0nb4 commented 1 month ago

I seem to run into the same problem, mostly for appartmentblocks. I'm looking into it, but have not found a clue yet.

ddceruti commented 2 weeks ago

I tested the newest DE database with a small bug fix and more hot water consumption (according to newest BDEW data). This did not solve the problem entirely. I tested the TMY for Berlin (from climate.onebuilding.org) with two attached homes and one single standing home. To avoid GFA problems, I set all relevant parameters to 1 and also set the monthly multipliers to 1.

Results: SFH_F (attached home) ~ 100 kWh/y and m2 SFH_F (free standing) ~ 140 kWh/y and m2

The hot water consumption is a pretty large fraction with around 25 kWh/m2 and y. This is expected, since the increase in the DE database is four fold with respect to the last version (~12 ldp vs now ~51 ldp). Here is the reference for this new value: https://www.bdew.de/service/daten-und-grafiken/trinkwasserverwendung-im-haushalt/. The reference for the setpoint is from statista for 2019 and is available in the documentation.md file

Please let me know how this newer DE database version is working for other cases and if you agree with the warmwater consumption - there are plenty of stated values ranging from 30 to 70 ldp but none seemed to be as low as 11.6 ldp.

ShiZhongming commented 1 week ago

We are revisiting demand script currently. Maybe this can change afterwards.