Add unmet water heater loads EMS program #1502
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jmaguire1
changed the title
…d on some discussions with Joe. Still need to connect the EMS sensor for WH outlet temperature.
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Right now, this method calculates:
Unmet shower energy I feel is the most complete metric, since it accounts for how far off from the desired temperature you are. However, no one really has a sense for if say 2 kWh of unmet showers is too many, so this way you can calculate the % of shower time where loads are unmet. We could also add metrics related to ALL hot water usage, or all fixtures. We'd want to account for the different desired delivered temperature for appliances, but it wouldn't be hard to add metrics like Unmet Energy for all fixtures. |
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@shorowit: I just did a major refactor of this, no more duplicate code. Thanks for the suggestions. It'd be good to know if you think this is a decent way to organize things at a minimum if/when you have a chance to take a look, we're looking to use this with the 120 V HPWH relatively soon. |
…ore merge conflicts.
… loads program). We could potentially have other unmet loads in the future in this program, and outputs are already pretty explicitly labeled as shower related.
…o unmet_wh_loads
…o unmet_wh_loads
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One thing I did realize after trying to use this in OCHRE: without having the shower max flow rate somewhere in HPXML or an unnormalized schedule, it's hard to do the equivalent comfort calculations. I could see shower max gpm being an HPXML extension or switching to an unnormalized schedule (unnormalized is probably easier), but I think I can address this in a follow up after I get at least some of the 120V HPWH capabilities in. Other than that, this is finally ready for review @shorowit. Thanks Joe for helping me figure out some of the more complicated multiple WH cases. |
…o unmet_wh_loads # Conflicts: # BuildResidentialScheduleFile/measure.xml # HPXMLtoOpenStudio/measure.rb # HPXMLtoOpenStudio/measure.xml # HPXMLtoOpenStudio/resources/data/unavailable_periods.csv # HPXMLtoOpenStudio/resources/hotwater_appliances.rb # workflow/tests/base_results/results_simulations_misc.csv
…o unmet_wh_loads # Conflicts: # HPXMLtoOpenStudio/measure.xml # workflow/tests/base_results/results_simulations_misc.csv # workflow/tests/util.rb
| hot_water_fixtures,1,1,0,0 | ||
| hot_water_showers,1,1,0,0 |
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Currently showers are a subset of fixtures, which may be confusing to a user. Should we bite the bullet and replace fixtures with sinks and baths? What are the ramifications? Probably a breaking change for outputs (e.g., hot water gallons).
docs/source/workflow_outputs.rst
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| Annual Unmet Loads | ||
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| Annual unmet loads are listed below. | ||
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| ======================================== ===== | ||
| Type Notes | ||
| ======================================== ===== | ||
| Unmet Loads: Hot Water Shower Energy (J) TODO | ||
| Unmet Loads: Hot Water Shower Time (hr) TODO | ||
| ======================================== ===== | ||
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| TODO |
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What if we combine these with the above Annual Unmet Hours like so:
Unmet Hours: Showers (hr)Unmet Hours: Showers (%)
Also document that this only accounts for a storage water heater running out of water and occupant discomfort. It does not account for temperature drop due to a distribution system or a tankless water heater's minimum firing rate. Using simple schedules (rather than detailed/stochastic schedules) may under-represent these values.
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What should we report for timeseries, just Unmet Hours: Showers (hr)?
Also, seems like if we're no longer reporting unmet loads in kBtu, then we'd no longer need to use shower peak flow in the EMS program? If not, this should simplify down to just comparing Use Side temperature to Mixed temperature during shower draws.
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Good point, yes the % output would only make sense as an annual output.
Second question is for @jmaguire1.
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Just the hours in the timeseries makes a lot of sense.
If we drop the energy metric, and just track hours of unmet loads, then we could drop the flow rate. The original intent with including flow rate and calculating energy, rather than just hours, was that we might want to account for difference between a shower that's just below setpoint and one that's like 30F below setpoint, or a small amount of flow vs. multiple showers at the same time being below setpoint. I've been proposing energy as the more important metric for a few years now, but the problem (as we discussed) is no one has any context of what 1 kWh of unmet showers means.
All that being said: I'm OK with dropping energy and trying to just report unmet hours of showering, in which case I think it's fine to drop max flow rate from the EMS program. There's no real standard way to report this, and there's advantages to hours in terms of being more intuitive.
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Sounds good @jmaguire1. I've gone ahead and pulled the peak flow stuff out of the EMS program.
tasks.rb
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| water_heating_system.heating_capacity = 5000 if water_heating_system.water_heater_type == HPXML::WaterHeaterTypeStorage | ||
| water_heating_system.temperature = 100.0 if [HPXML::WaterHeaterTypeHeatPump, HPXML::WaterHeaterTypeTankless].include?(water_heating_system.water_heater_type) |
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This is kind of weird, the HPWH/tankless systems are not actually undersized, they just have their setpoint artificially lowered to result in unmet showers. At least for storage/HPWH, can't we just set a small tank volume instead? Maybe we don't need all the sample files. We can probably remove the tankless one, for example.
(Also, hopefully at some point in the future, we'll allow optional capacity inputs for HPWHs and tankless systems.)
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I tried instead reducing tank volume (e.g., to 1 gal). Water Heater Use Side Outlet Temperature doesn't appear to drop (even when using stochastic schedules).
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Definitely a little surprised, but I know we do have some code that scale the max flow rate to ensure that you never draw out more than the whole tank volume in an hour
I think this means the water heater might be reducing the flow rate through it with stochastic schedules if you try to specify like 2 gal/min, the WH might only see lower flow rate. E+ will throw an error if you have a flow rate on the use side larger than the tank volume/hour, so we do need this code. If reducing the tank volume and heater capacity doesn't give you unmet loads, I'm not sure that there's a better way to do this without reducing the setpoint.
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Hmm, I'm definitely confused here. The code you are referencing above is in the apply_solar_thermal method. Looks like storage_tank.setUseSideDesignFlowRate(UnitConversions.convert(storage_volume, 'gal', 'm^3') / 60.1) is used only for stratified tanks, not mixed. I'm seeing that use side outlet temperature doesn't drop for an HPXML file with storage water heater (i.e., mixed w/autosized use side design flow rate).
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Here is 40 gal vs 1 gal:
| @@ -34,6 +34,7 @@ __New Features__ | |||
| - **Breaking change**: Disaggregates "Walls" into "Above Grade Walls" and "Below Grade Walls" in results_design_load_details.csv output file. | |||
| - Updates `openei_rates.zip` with the latest residential utility rates from the [OpenEI U.S. Utility Rate database](https://apps.openei.org/USURDB/). | |||
| - Adds a warning if the sum of supply/return duct leakage to outside values is very high. | |||
| - Adds metrics for unmet hot water loads. | |||
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Need a better description.
Pull Request Description
Add an EMS program for calculating unmet water heating loads. Focus is on unmet showers, but we can also calculate this for each end use if we wanted to. Addresses #1170.
Checklist
PR Author: Check these when they're done. Not all may apply.
strikethroughand check any that do not apply.PR Reviewer: Verify each has been completed.
Schematron validator (EPvalidator.xml) has been updatedtasks.rb)HPXMLtoOpenStudio/testsand/orworkflow/tests/hpxml_translator_test.rb)openstudio tasks.rb update_measureshas been run