Pull Request Description

• Break out solar thermal from other fuel in Water Heater Fuel
• Consolidate "Solar Hot Water" with "Water Heater Efficiency", which now defines the params for both solar thermal (type can be None) and a normal water heater. In OS-HPXML, all solar thermal must be connected to a secondary water heater.
• Model a typical solar water heater with backup ER heating element in the tank as a solar collector (which has a tank of its own) + electric standard tank with EF 0.97 and R-6.2 jacket. The higher efficiency and insulation were used to minimize the standby loss (or UA) of the second tank, which other would consumes electricity even without backup use. A few notes to document from this experience:
  • "water_heater_standby_loss" in options_lookup is only used for combi boilers (also mentioned in OS-HPXML documentation). Changing that for tank WH does nothing.
  • "water_heater_recovery_efficiency" is 0.98 for electric tank by OS-HPXML default. Changing that value in options_lookup does not seem to override that. A test failed with an error of recovery efficiency not being higher than WH efficiency when the backup tank was assigned 0.98 for efficiency and 0.99 for recovery efficiency.
  • "water_heater_jacket_rvalue" can only go up to about R-6.2 before UA_adjusted becomes negative. And it varies by tank volume, and all sorts of variables. An 80 gal tank of EF 0.97 with a jacket r_val of 7 would already make ua_adj negative
  • Solar thermal loads can be negative or exorbitantly large. See issues Negative Solar Thermal Hot Water Load #1360 and Exorbitantly large solar thermal load #1365

This work is critical for HI integration where solar thermal is estimated to be a significant portion of Hawaii's total residential consumption and on par with rooftop solar according to our attempt to resolve the energy reporting from EIA 861/M and State Energy Data System:

More stats available in resstock-estimation companion PR

Related Pull Requests

resstock-estimation PR: https://github.com/NREL/resstock-estimation/pull/444

Related Issues

[What issue(s) is the PR addressing]

Checklist

Required:

• Add to the changelog_dev.rst file
• No unexpected regression test changes on CI (comparison artifacts have been checked)
• Update documentation (one is required)
  • Technical reference guide
  • Technical development guide

Optional (not all items may apply):

• Tests (and test files) have been updated
• Supporting resource files have been updated (related to resstock-estimation)
  • data dictionary
  • source report
  • options saturation
  • options_lookup
• openstudio tasks.rb update_measures has been run