Geothermal loop & soil properties

[joseph-robertson]

Pull Request Description

Addresses #1202.

Connect to new HVACPlant/GeothermalLoop object: hpxmlwg/hpxml#367.
Connect to new BuildingSummary/Site/Soil object: hpxmlwg/hpxml#373.

To maintain existing behavior, the following inputs (set in hvac.rb's set_gshp_assumptions method) can be moved over to HPXML GeothermalLoop and Soil fields?

GeothermalLoop	OS-HPXML	Notes
LoopType	u_tube_spacing_type	Choices of 'as', 'b', 'c'. Always set to 'b'.
LoopConfiguration	loop_configuration	Always set to "vertical".
LoopFlow	loop_flow	Can be autosized in hvac_sizing.rb's apply_hvac_ground_loop method.
BoreholesOrTrenches/Count	num_bore_holes	Can be autosized in hvac_sizing.rb's apply_hvac_ground_loop method.
BoreholesOrTrenches/Length	bore_length	Can be autosized in hvac_sizing.rb's apply_hvac_ground_loop method.
BoreholesOrTrenches/Spacing	bore_spacing	Default to 16.4 ft.
BoreholesOrTrenches/Diameter	bore_diameter	Default to 5.0 in.
Grout/Type	grout_type	Default to "standard".
Grout/Conductivity	grout_conductivity	Default to 0.4 ("standard") or 0.8 ("thermally enhanced") Btu/h-ft-R.
Pipe/Type
Pipe/Conductivity	pipe_cond	Default to 0.23 Btu/h-ft-R.
Pipe/Diameter	pipe_size	Default to 1.25 in.
Pipe/ShankSpacing	shank_spacing	Default to u_tube_spacing + pipe_od.
extension/BorefieldConfiguration	bore_config	Default based on BoreholesOrTrenches/Count.
	design_delta_t
	frac_glycol	Changed from 0.3 to 0.2.
	pipe_od
	pipe_id

Add optional BuildResidentialHPXML measure arguments:

• geothermal_loop_configuration (required)
• geothermal_loop_borefield_configuration
• geothermal_loop_loop_flow
• geothermal_loop_boreholes_count
• geothermal_loop_boreholes_length
• geothermal_loop_boreholes_spacing
• geothermal_loop_boreholes_diameter
• geothermal_loop_grout_type
• geothermal_loop_pipe_type
• geothermal_loop_pipe_diameter

Soil	OS-HPXML	Notes
SoilType
MoistureType
Conductivity	ground_conductivity	Default to 1.0 Btu/hr-ft-F.
extension/Diffusivity	ground_diffusivity	Default to 0.0208 ft^2/hr.

Add optional BuildResidentialHPXML measure arguments:

• site_soil_and_moisture_type
• site_ground_diffusivity

New sample file (parent base-hvac-ground-to-air-heat-pump.xml):

• base-hvac-ground-to-air-heat-pump-detailed.xml

---

Questions:

• We use GroundHeatExchangerVertical. Is this only appropriate for "boreholes" (vertical) vs "trenches" (horizontal). (FYI there is GroundHeatExchangerHorizontalTrench.) If a user wants to model "trenches", do we allow it? Otherwise, we'd probably want to use the LoopConfiguration field for distinguishing between, e.g., "vertical" and "horizontal"? Are autosized LoopFlow, Count, Length valid for horizontal? Update: we want to limit use to "vertical" loop configuration.
• Currently hp_ap.u_tube_spacing_type = 'b' is hardcoded. Should this be an input (i.e., new HPXML field)? Update: GHED has 'single', 'double', 'coaxial' (in the borehole). All the hp_ap.u_tube_spacing_type choices are 'single'. We probably want to just stick with 'b' (in part because it's always been hardcoded to this and we probably don't have confidence in the other choices).
• I'm using 0.8 as the default value for "thermally enhanced" grout type. Is there a thermally enhanced default value for pipe conductivity? Update: there is not.
• Do we want to default hp_ap.frac_glycol to the HPXML file? If so, where should it go in the schema? Also, expose it as an argument? Should we change the hardcoded 0.3 to 0.2? Update: not very sensitive; let's fix this to 0.2 and not expose it as an argument.
• Do we need to put lower and upper bounds on bore_depth? The json files have g functions for bore depths ranging from 24 m to 384 m. Update: Matt says 384 m definitely sounds unlikely. We'll use 24 and 152 (see updated docs snippet above).
• Ground conductivity. 1.0 corresponds to SoilType=? and MoistureType=? Do we want to support default values for other combinations of SoilType/MoistureType? Update: Jeff has some tables of different soil types.
• I believe hvac_sizing.rb autosizes a total bore length (if bore depth not given), from which we need to divide it by the number of bore holes to get depth of each borehole. Do we still need/want to increment the bore_depth based on min and max depth values? Update: Currently adjusting number of boreholes such that bore depth is valid.
• Does it make sense for values assigned to site_ground_conductivity to populate fields of both foundation heat transfer and geothermal heat exchanger? Or should we have separate inputs? Matt: from a modeling perspective, yes it matters; from a practical standpoint, no. So we will leave this as-is for now.
• What about upper bounds on either bore_spacing or bore_diameter? Are there values for these for which the g-function value interpolation would be invalid?
• Address TODOs in docs above.

Checklist

PR Author: Check these when they're done. Not all may apply. strikethrough and check any that do not apply.

PR Reviewer: Verify each has been completed.

• Schematron validator (EPvalidator.xml) has been updated
• Sample files have been added/updated (via tasks.rb)
• Tests have been added/updated (e.g., HPXMLtoOpenStudio/tests and/or workflow/tests/hpxml_translator_test.rb)
• Documentation has been updated
• Changelog has been updated
• openstudio tasks.rb update_measures has been run
• No unexpected changes to simulation results of sample files

[joseph-robertson]

Should try approaching this from the other direction. Meaning, look at the HPXML schema and try to start to identify needs in OS-HPXML (i.e., reformat the table to have HPXML elements as the index column).

[joseph-robertson]

See spreadsheet comparing OS-HPXML defaults vs industry standard (e.g., grout conductivity, pipe diameter/conductivity).

Look at assigning grout conductivity values based on whether the type is "standard" or "thermally enhanced".

[jmaguire1]

@joseph-robertson: I was just talking to the commercial team and Matt Mitchell. Matt suggested that it might be more reasonable to assume the default pipe diameter is 1 1/4" rather than 3/4". Do you have any objection to making that change? I'd tend to yield to his expertise, plus it'd make us consistent with what commercial is doing.

[joseph-robertson]

@joseph-robertson: I was just talking to the commercial team and Matt Mitchell. Matt suggested that it might be more reasonable to assume the default pipe diameter is 1 1/4" rather than 3/4". Do you have any objection to making that change? I'd tend to yield to his expertise, plus it'd make us consistent with what commercial is doing.

Done in f53e307.

[yzhou601]

This is ready for review