US Supermarket Modeling Activities

Transcription

1 New Supermarket Modules for EnergyPlus Van D. Baxter Building Technologies Integration Program Oak Ridge National Laboratory IEA Annex 31 Workshop Zurich, Switzerland May 19, 2008 Managed by UT-Battelle

2 US Supermarket Modeling Activities Available tools include simple spreadsheets (ORNL/Annex 26); bin-type (Foster-Miller); detailed hourly (DOE2.2R, EPRI SST) EnergyPlus code is most recent Hourly whole building simulation tool (building & HVAC/R system together) DOE s preferred model download site follows Source code available (not for distribution) but requires a collaborative developer license $250 for academic, research, not-for-profit institutes $1000-$2500 for commercial development and distribution rights Expansion of supermarket refrigeration module underway 2 Managed by UT-Battelle

3 EnergyPlus Code E+ based on simultaneous solution of building (surface and zone air heat balance mgrs) and systems (bldg systems simulation mgr) refrigeration module is one of >60 individual system simulation modules 3 Managed by UT-Battelle

4 Energy Plus Refrigeration Module Original module Refrigerated Case Equipment Conventional DX compressor rack system with up to six refrigerated cases (or case lineups) Air-cooled condenser only originally evaporative and water-cooled condenser options added last year Simulates condenser heat recovery to air (shown below) or water Capacity based on user-selected fraction of total condenser heat rejection (30% maximum) 4 Managed by UT-Battelle

5 Energy Plus Refrigeration Module Compressor rack energy computation Calculate compressor rack energy based on total case evaporator load and compressor COP Compressor Rack:RefrigeratedCase object within E+ 5 Managed by UT-Battelle

6 Energy Plus Refrigeration Module Compressor rack energy computation, cont d. Temperature used for COP function depends on location Indoor (self-contained) ID dry bulb Water-cooled function of return water temp from plant loop heat rejection system (e.g. cooling tower) Outdoor, dry condenser OD dry bulb Outdoor, evaporative condenser function of effectiveness of evaporative condenser Rack energy computation 6 Managed by UT-Battelle

7 Energy Plus Refrigeration Module Energy Plus Refrigeration Module Condenser fan energy computation Function of effective condenser air temperature (ftemp) and design fan power ftemp is optional user choice; if no ftemp is specified then fan power = design fan power whenever system is rejecting heat For air-cooled condensers only effective temperature used is same as for compressor power ftemp function 7 Managed by UT-Battelle

8 Energy Plus Refrigeration Module Case load Case:Refrigerated object in E+ Based on mfr rated data performance curves for latent case credits and defrost heat load used to determine load at off-design Case lighting, fan, anti-sweat heater power based on nominal power, schedules, and control type Model accounts for sensible and latent case credits and their impact on zone temp and RH 8 Managed by UT-Battelle

9 Energy Plus Refrigeration Module Energy Plus Refrigeration Module Case load Case:Refrigerated object in E+ 9 Managed by UT-Battelle

10 Energy Plus Refrigeration Module Expansion Objective Enhance E+ refrigeration module by adding/extending capabilities Planned additional capabilities Completed Evaporative condenser and water-cooled (WC) condenser w/cooling tower (evap or dry) Evaporative condenser included in April 2007 E+ release (ver 2.0) WC condenser included in October 2007 release (ver 2.1) WC condenser capability facilitates coupling of water-source heat pumps to condenser water loop for heat recovery In process Detailed refrigeration loop and component option (planned for October 2008 release) Secondary loop system model(s) (October 2009 release) 10 Managed by UT-Battelle

11 Energy Plus Refrigeration Module Expansion, cont d. Evaporative condenser model Simplified effectiveness algorithm Accounts for evaporation (make up water), sump pump power, freeze protection heater as well as condenser fan Pump power user input or calculated as W/W of total rated refrigeration capacity of system Electric basin heater activated if OD air falls below set temperature capacity is user input with 200 W/K default User-specified availability schedule to shut off evaporative operation during very cold weather Defaults to air-cooled operation 11 Managed by UT-Battelle

12 Energy Plus Refrigeration Module Expansion, cont d. Water-cooled condenser model Requires that a water loop be defined per the standard E+ approach Water loop must contain at least a pump and one or more devices to remove refrigeration condenser heat (see example below) Cooling tower and water storage tank are acceptable heat sinks Can also add water source heat pumps to loop to recover condenser heat for space heating Means larger cooling tower capacity necessary to handle additional heat rejection from heat pumps in summer if used for space cooling 12 Managed by UT-Battelle

13 Energy Plus Refrigeration Module Expansion, cont d. Detailed refrigeration model option Compressors modeled based on mfr data for power, capacity, refrigerant flow Multiple compressors per rack with individual units cycled on/off as case load dictates need Desuperheater heat recovery capacity calculated instead of constant fraction as now Expect to have coding and draft documentation completed by August to meet October 2008 E+ release deadline Secondary loop system model Work not yet begun Approach expected to be similar to that used by CyberMart Planned for October 2009 E+ release 13 Managed by UT-Battelle

14 Benchmarking Data Sources Task 3, 4 use model validation/calibration Detailed monitored data from present and past field tests (detailed refrigeration system, not much on rest of bldg) Boston, (Annex 26) Southern CA, (courtesy CEC & Safeway) WalMart experimental stores (ORNL & NREL monitoring), 2005 to present 14 Managed by UT-Battelle