experience testing energyplus with the iea hvac bestest e100
Contents
1. August 2002 version 1 0 2 and December 2002 version 1 0 3 The results for the HVAC BESTEST series with the three new releases of EnergyPlus along with the analytical results and results for the last test series reported in the IEA HVAC BESTEST final report version 1 23 are presented in the charts below Although some minor changes took place in version 1 0 2 and were later reversed in version 1 0 3 the results for version 1 0 3 Build 19 are identical to those for version 1 23 Pertinent changes implemented subsequent to version 1 23 were e Reformatted and changed the hfe psychrometric function to conform with ASHRAE equations e Added hg psychrometric function as per ASHRAE equations and now use this for latent gain conversion to humidity ratio SAT Figure 7 shows the latent cooling coil loads for EnergyPlus release versions 1 0 0 023 1 0 1 012 1 0 2 008 and 1 0 3 019 CONCLUSIONS EnergyPlus Version 1 0 0 023 and subsequent versions up through the most recent release EnergyPlus 1 0 3 019 was used to model a range of HVAC equipment load specifications as specified in International Energy Agency Building Energy Simulation Test and Diagnostic Method for HVAC Equipment Models HVAC BESTEST The ability of EnergyPlus to predict zone loads cooling coil loads cooling equipment energy consumption and resulting zone environment was tested using a test suite of 14 cases which included varying internal loads and outdoor c2. SE W 7777777 F SIT EA 22 xz o 3 ee a a 4 o 2 Ss S mo FREECEREEERERE hhkkk G a W LLI N co oO cA k RRR RR RRR y y a y RRR ERR RRR RRR ERR ERR RRR 2 oO so a o O A am a oO Ss LY Toot x s NXXX NXXX AAA wwaiwwwwwwwwwwwwwwwww wwwwwwwwwawwwwwwwwwwwwwwwwwwwwwwiwwwwwwwwwiwwwwwwww WwW a gt NNNNN NNN AAA INNAN ANIN NNN ANANIN NNNNA ANANNNNNANANNY W a bn lt i 0 E3 a oOo oO lll a oo Oo t N D oo Oo lt N T z YAK sr 3191513 umy sn q15un5 la Figure 2 Compressor Plus Outdoor Fan Electricity Consumption Results for Early Versions of EnergyPlus 471 6 000 F 7ZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZSZG ZZZZZZZZZZZZZZzZzZz2 ZzZZ2Z2ZZZ2Z2ZZZZZ2Z2ZZZ2Z2Z2ZZZ2Z2Z2ZZZ2Z2ZZZZ2ZZZZZ2ZZZZZZZZ AAAAAAAANAAAAAAAAAAAAAAAA AAA AAAS rzzzzzzzzzz gt zzzzzzzzzzzzzzzzzzz2 F ZZZZZZZZZZZZZZZZZZZzZzZZzZZzZzZ Z z 2 Z22172 1712121212 23 AMANARAAARAAARARAAAAAAARARAAARARAARARAA yy y y y r i i ARRAS L n rzz zzzzz zzz z zz z z gt zzzzxz u gt xxx z x x gt x gt x gt xz3 gt ry Xz z zzzzz xx xz gt Q zzzz3 rzzzzzzzzzzzzzzzzzzzzzzz7zzzzzzz 7z zxz zzzzzzzzzz zzzzzzzzzzzzZ2z z xz zz3 YY lt iyyyyyvyyyyvyyyyvyyyyyyyyyyyyyyyyyyyyyyy3l n ESSSSSSSSssssssssssasy NANNNNNN NXN ANN NNN NNN AANA AAAA NNN
3. modeling of the simple unitary vapor compression cooling system the EnergyPlus Window Air Conditioner model was utilized No other direct expansion DX coil cooling system was available at the time that this work began but others have been added since then The Window Air Conditioner model consists of three modules for which specifications can be entered DX cooling coil indoor fan and outside air mixer The outside air quantity was set to 0 0 The DX coil model is based upon the DOE 2 1E DX coil simulation algorithms with modifications to the coil bypass factor calculations The specification calls for the unitary air conditioner to have a draw thru indoor fan The Window Air Conditioner model in early beta versions of EnergyPlus could only model a blow thru fan configuration In Version 1 Build 05 and later a draw thru configuration is also available This limitation may have affected the latent load on the cooling coil and the compressor energy consumption in the early results Round and Round 2 but other issues were also contributing errors at that point A draw thru fan was modeled in Round 3 and Round 4 The rated coefficient of performance COP required as input by the EnergyPlus DX coil model requires that the input power be the combined power for the compressor and condenser fans As such there are no separate input variables or output variables available for the compressor or condenser fan The only output variable availa
4. to an input error a modeling inconsistency or flaw in the program logic The tests described in International Energy Agency IEA Building Energy Simulation Test and Diagnostic Method for HVAC Equipment Models HVAC BESTEST Volume 1 Cases E100 E200 Neymark amp Judkoff 2001 were performed Final comparison results for all programs that participated in the IEA project are reported in an NREL report by the same name as above but with a January 2002 publish date Neymark amp Judkoff 2002 As stated in its Introduction the IEA HVAC BESTEST report documents an analytical verification and comparative diagnostic procedure for testing the ability of whole building simulation programs to model the performance of unitary space cooling equipment that is typically modeled using manufacturer design data presented in the form of empirically derived performance maps The report also includes results from simulation programs that were used for field trials of the test procedure SUMMARY OF TEST CASES The following tests were performed as specified in the HVAC BESTEST User s Manual section 1 3 e Case E100 Base Case Mechanical System e Additional Dry Coil Test Cases Cases E110 E120 E130 E140 e Humid Zone Test Cases Cases E150 E160 E165 E170 E180 E185 E190 E195 E200 Building and 467 Base Case Building and Mechanical System Case E100 The basic test building is a rectangular 48 m single z
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7. Plus Version 1 0 3 019 December http www energyplus gov pdfs ep_v1l03_hva c_besttest pdf Neymark J and R Judkoff 2001 International Energy Agency Building Energy Simulation Test and Diagnostic Method for HVAC Equipment Models HVAC BESTEST National Renewable Energy Laboratory Golden Colorado October 2001 Neymark J and R Judkoff 2002 International Energy Agency Building Energy Simulation Test and Diagnostic Method for HVAC Equipment Models HVAC BESTEST National Renewable Energy Laboratory Golden Colorado NREL TP 550 30152 January 2002 3 000 2 500 2 000 1 500 Cooling Coil Load kWh 1 000 cn _ oO oO e Z777777 7777777777ag apa E100 E110 E120 E130 E140 E150 E160 E EnergyPlus Ver 1 23 o Analytical TUD E Analytical HTAL1 a pe a a a l L VZZ777777777777777 7 777 Z72 L LALLA N E165 E EnergyPlus Ver 101 42 Mi EnergyPlus Ver 102 08 E170 HVAC BESTEST Case k EEE KK E KE KK AKK KK EKK KKE KK KKK K KK KK KKK KKK E K EKK K K E KKE EKK KAK K K KK KE KK E KK KK EAER KEKE K K KK EE KKK KK KKK KKK k KK KKK KKE KKK KK KK KK KK KK KK KKK RKKK KKK KKK KKK KKK KKK KK KK KKK KK KK KKK KKK KKK KK KK KKK KKK KK KKK KK KKK fa KRKK KKK KK KKK KKK KK LILLE ELLE LDL CPLLLLLLLLLLLLLLLLLL LLL Ba L AL a L E180 E1685 E190 E195 E200 EnergyPlus Yer 103 19 E Analytical HTAL2 Figure 7 Latent Cool
8. Y s muanunnunnnananananannaaananuanunu SARA EXXAAAAAAAAAAAAAAARAARARRARAARARR EES mu EXANANAAAAAAAAAAR rrr AXAAAAAAAAAAN snnnnnnnnnnnn ku wwa a 2 a Perry E150 0 0000 E100 E110 E120 130 140 o Analytical TUD E Analytical HTAL1 EnergyPlus Yer 1 11 AAAA AWA WAWA TITI PETTI rr E160 ETY ETY AAAA RRR RRR RRR RRR RRRA sanns munan BSS SS aa da dia saa sai saa sa ai sa sas da sda saa di sia daa da sda sda sas da dda das daa pa sda dads dad dad ddd ddd dd ddd dd AMAAAAAAAAAAAAAAAAAAAAARARARRARRARER EERE EEE EREE EERE EEE EEE EERE EEE EEE EEE EEE EE EEE EEE EE EEE EEE EERE EERE EEE EEE TITI mus NNN NNN AAA iiIIIiIiwiwiwiiAwwAw oon mu AXNAAAAAAAAAAAAAAAAAS PTTTriit titi rrr rz EMA H KLA E165 E170 E185 E190 E195 E200 HVAC BESTEST Case E Analytical HTAL2 ClEnergyPlus Ver 1 14 Em EnergyPlus Ver 1 17 EnergyPlus Ver 1 19 EnergyPlus Beta 5 07 Hi EnergyPlus Beta 5 14 EnergyPlus Ver 1 23 Figure 6 Indoor Humidity Ratio Results for Early Versions of EnergyPlus RESULTS OF TESTING WITH SUBSEQUENT RELEASES OF ENERGYPLUS The IEA HVAC BESTEST workgroup has completed their activities and final results are recorded in a report authored and released by NREL in January 2002 Neymark amp Judkoff 2002 Since the completion of that study further capabilities and improvements have been added to EnergyPlus with new releases occurring in June 2002 version 1 0 1
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10. ad delivered to the space were being adjusted appropriately for cycling time e For the dry coil cases the reported sensible coil load was slightly higher than the reported total coil load Latent load was not available as an output variable but was calculated by subtracting the sensible from the total This error caused small negative latent loads to be calculated for the dry coil cases e Zone relative humidity was higher for many tests compared to the analytical results especially for the tests with wet coils This difference was probably due to simulating a blow thru configuration rather than the required draw thru configuration Software change requests were posted Once a new version became available the tests were rerun Round 2 EnergyPlus Beta 5 Build 014 EnergyPlus Beta 5 14 included changes to fix the following problems which were identified in HVAC BESTEST Round 1 e Reporting of cooling coil loads were corrected to account for run time during cycling operation e The methods of calculating sensible heat ratio SHR and coil bypass factor were modified to eliminate the problem where the dry coil cases reported sensible coil loads which were slightly higher than the reported total coil loads This error was causing small negative latent loads to be calculated for the dry coil cases During the second round of simulations with EnergyPlus Beta 5 14 the cooling coil error identified during the first round of si
11. alize all HVAC air nodes The following changes in results were observed e The sensible and latent coil loads improved and now track very close to the analytical results e The mean indoor temperature for Case E200 improved and now along with rest of the cases matches exactly with the analytical results e The mean indoor humidity ratio tracks the analytical values better especially for the wet coil cases For Case E120 however the 470 One what The BESTEST CDF curve versus was determined based on net total capacities of t cases or are DX Coil model that the part load curve be expressed on 11es In mos 1 results BESTEST slightly less than analytical results ires n 1 1Ca Curve Indoor fan power consumption and fan heat requires problem may have to do with the basis of the COP results changed but are still mixed the unit while the EnergyPlus the basis of gross sensible capac match analyt EnergyPlus requ CDF f lation ff indoor for the month of February of d to 0079 ize week ion o 0 inning o tial imu ini filtrat ives a mean the s warmup days overdry the zone for this case the first in there is no source of moisture to overcome the value ing 1 t the beg ing analytical Introducing infiltration for the first week of ty ratio a 1 blem and g 1 e and then turn h t is pro 10 lation conditions dur than t
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13. ble for reporting in EnergyPlus is the DX coil electricity consumption which includes compressor plus condenser fan Weather Data The typical meteorological yeat TMY weather files provided as part of the HVAC BESTEST package are not directly usable by EnergyPlus In order to 468 create an EnergyPlus compatible weather file the TMY file was first converted to BLAST format using the BLAST weather processor WIFE An EnergyPlus translator was then used to convert the weather data from the BLAST format to EnergyPlus format RESULTS OF TESTING DURING INITIAL ENERGYPLUS DEVELOPMENT HVAC BESTEST was first modeled using a beta version of EnergyPlus This section discusses issues which arose during this phase of testing Four separate rounds of official results were submitted to the IEA HVAC BESTEST group Each round of tests Is discussed below Figures 1 through 6 show selected results illustrating the issues which arose during this testing Round 1 EnergyPlus Beta 5 Build 007 During the first round of simulations several potential software errors were identified in EnergyPlus Beta Version 5 07 e Fan electrical power and fan heat were consistently low compared to the analytical results for all tests e The reported cooling coil loads were consistently too high and apparently had not been adjusted for the fraction of the time step that the equipment operated however the DX coil electricity consumption and actual lo
14. each case The results of analytical solutions are included in the IEA NREL report Only the following parameters are varied to develop the remaining test cases e Internal sensible gains e Internal latent gains e Thermostat setpoint dry bulb e Outdoor dry bulb temperature Weather Data Four three month long January March TMY format weather files were provided with the test suite The only parameter that is different for each weather file is the ambient dry bulb temperature all other data is the same for each weather file Simulations for all cases were run for a three month period The first month of the simulation period January served as an initialization period The output results reported were for the second month of the simulation February ENERGYPLUS MODELING METHODOLOGY AND ISSUES With nearly any published test suite issues and choices arise when modeling the tests with a specific software package These issues are summarized below Building Envelope Construction The specification for the building envelope indicates that the exterior walls roof and floor are made up of one opaque layer of insulation R 100 with differing radiative properties for the interior surface and exterior surface ref Table 1 4 of Volume 1 To allow the surface radiative properties to be set at different values the exterior wall roof and floor had to be simulated as two insulation layers each with R 50 HVAC System For
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16. eveloped by another modeler The energy input ratio EIR curve required for the EnergyPlus DX Coil model is based on compressor input power plus outdoor condenser fan power but the EIR curve fit done for DOE 2 applied only to the compressor input power e Relaxed the min max limits of the performance curve independent variables cooling coll entering wet bulb and condenser entering dry bulb to allow extrapolation of cooling capacity as a function or temperature CoolCapFT and EIR as a function of temperature EIRFT outside the bounds of the equipment performance data given in the specification e The BESTEST cycling degradation factor CDF curve was determined based on net total capacities of the unit while the EnergyPlus DX Coil model requires that the part load curve be expressed on the basis of gross sensible capacities A new CDF curve was developed which was intended to be on a gross capacity basis but a later review of this curve showed an error in the derivation Further review showed that there is really little difference between net part load and gross part load so the revised curve was then removed and the original CDF curve was used e The CDF curve part load curve was applied to the indoor fan operation where previously there was no input available for this This change also required using the FAN SIMPLE ONOFF object instead of FAN SIMPLE CONSTVOLUME which has been used previously e Added one week of infiltrat
17. ing Coil Load Results for Later Versions of EnergyPlus Note the increase in latent load in version 1 0 2 008 which was later corrected in version 1 0 3 019 414
18. ion to the beginning of the Case E120 run period to prevent overdrying of the zone during the simulation warmup period See the results discussion below for more details Relevant source code changes from Version 1 0 0 011 to Version 1 0 0 023 e Standard air conditions for converting volume flow to mass flow in the indoor fan calculations were changed HVAC BESTEST specifies that the volume flow rate is for dry air at 20C EnergyPlus was using a dry bulb of 25C at the initial outdoor barometric pressure with a humidity ratio of 0 014 kg kg although the EnergyPlus documentation indicated 21C and 101325 Pa was being used EnergyPlus now calculates the initial air mass flow based on dry air at 20C at the standard barometric pressure for the specified altitude and the documentation reflects this change e The specific heat for air throughout the air side HVAC simulation was changed from a dry Cp basis to a moist Cp basis Previously a mixture of dry and moist Cp had been used for various HVAC calculations e The heat of vaporization hfg for converting a zone latent load into a load in the HVAC system was changed e A new input field was added to FAN SIMPLE ONOFF to allow a CDF curve part load curve to be applied to the indoor fan operation where previously part load adjustments could only be applied to the compressor and outdoor fan e Changed the moisture initialization to use the initial outdoor humidity ratio to initi
19. mE ro Building Simulation 2003 Eighth International IBPSA Conference Eindhoven Netherlands August 11 14 2003 EXPERIENCE TESTING ENERGYPLUS WITH THE IEA HVAC BESTEST E100 E200 SERIES Robert H Henninger Michael J Witte and Drury B Crawley GARD Analytics Inc Park Ridge Illinois USA gt U S Department of Energy Washington DC USA ABSTRACT The EnergyPlus building energy simulation software has been tested using the IEA HVAC BESTEST E100 E200 series of tests The Volume 1 final report for the International Energy Agency IEA Building Energy Simulation Test and Diagnostic Method for Heating Ventilating and Air Conditioning Equipment Models HVAC BESTEST was recently published in January 2002 HVAC BESTEST is a series of steady state tests for a single zone DX cooling system Cases range from dry to wet coil low to high part load and low to high temperatures This published test suite includes three sets of analytical solutions and results from several other simulation programs for comparison This test suite was initially used to test EnergyPlus beginning with beta versions prior to its official public release and it is also applied as an ongoing quality assurance test The application of these tests proved to be very useful in several ways e Revealed input model shortcomings which resulted in new user inputs being added e Revealed reporting errors which were fixed e Revealed algorithmic er
20. mulations was corrected to account for cycling during each time step and this brought the evaporator coil loads closer to the range of results for the other programs but the loads were still higher than they should be Another potential error was therefore identified which may have been masked by the coil problem identified in Round 1 e Although there was excellent agreement for zone total cooling load the evaporator cooling coil load was larger than the zone cooling load plus fan heat e Also the mean indoor dry bulb for Case E200 moved from 26 7C to 27 1C e The other problems identified in Round 1 still remained low fan power poor agreement in zone humidity ratio Round 3 EnergyPlus Version 1 0 0 011 The suite of HVAC BESTEST cases were simulated again using EnergyPlus Version 1 0 0 011 the first public release of Version 1 0 April 2001 which included the following changes made since Round 2 e Modified method for calculating coil outlet conditions e Changed to use of double precision throughout all of EnergyPlus This change was prompted by various issues not related to HVAC BESTEST e Added two output variables for tracking fan and compressor run time e Added an output variable for coil latent load e Added Draw Thru Fan option to Window Air Conditioner model e The name of the DX coil object was changed from COIL DX DOE2 to COIL DX BF Empirical to better represent its algorithmic basis I
21. n addition the following input file changes were made e Changed from blow thru fan to draw thru configuration e Updated the DX coil COIL DX BF Empirical object name to The following changes in results were observed 469 e Indoor fan power consumption and fan heat decreased significantly from Round 2 moving farther below the analytical results e Space cooling electricity consumption changed slightly from Round 2 and moved closer to the analytical results e Mean indoor humidity ratio decreased compared to Round 2 moving farther away from the analytical results for most of the dry coil cases and moving closer to the analytical results for the wet coil cases e Mean indoor dry bulb for Case E200 moved further out of range to 27 5C the setpoint for this case is 26 7C In general except for fan power fan heat and humidity ratio the overall EnergyPlus Version 1 0 0 011 results compared much better to the HVAC BESTEST analytical results Round 4 EnergyPlus Version 1 0 0 023 The suite of HVAC BESTEST cases was simulated again using EnergyPlus Version 1 0 0 023 a maintenance release June 2001 which included both input file and source code changes from Version 1 0 0 011 Input file changes for Round 4 e The equipment performance curves were refit from scratch using data from Table 1 6c of the HVAC BESTEST specification Previously the curve coefficients had been taken from DOE 2 input files d
22. onditions The results predicted by EnergyPlus for 14 different cases were compared to results from 7 other whole building energy simulation programs that participated in an International Energy Agency IEA project which concluded in January 2002 Comparisons were also made with the results from three analytical solutions EnergyPlus results generally agreed to within 1 of the analytical results except for the mean zone humidity ratio which agreed to within 3 for high SHR cases but was within 0 20 for low SHR cases For more detailed results and discussion see the EnergyPlus testing report for HVAC BESTEST E100 to E200 Henninger and Witte 2002 The HVAC BESTEST suite is a very valuable testing tool which provides excellent benchmarks for testing HVAC system and equipment algorithms versus the results of other international building simulation programs As discussed above HVAC BESTEST allowed the developers of EnergyPlus to identify errors in algorithms and improve simulation accuracy Acknowledgment This work was supported by the Assistant Secretary for Energy Efficiency and Renewable Energy Office of Building Technology State and Community Programs Office of Building Research and Standards of the U S Department of Energy Drury Crawley program manager REFERENCES EnergyPlus 2003 www energyplus gov Henninger R H and M J Witte 2002 EnergyPlus Testing with HVAC BESTEST 3 500 Part 1 Tests E100 to E200 Energy
23. one 8 m wide x 6 m long x 2 7 m high with no interior partitions and no windows The building is intended as a near adiabatic cell with cooling load driven by user specified internal gains For further details refer to Section 1 3 2 1 of the HVAC BESTEST User s Manual The mechanical system is a simple unitary vapor compression cooling system with air cooled condenser and indoor evaporator coil 100 convective air system no outside air or exhaust air single speed draw through air distribution fan indoor and outdoor fans cycle on off with compressor no cylinder unloading no hot gas bypass crankcase heater and other auxiliary energy are 0 There is a non proportional type thermostat heat always off cooling on if zone air temperature gt 22 2 C and heat extraction rate is assumed to equal the maximum capacity of the equipment for the hour s environmental conditions For further specifications and equipment s full load and part load performance specifications see Section 1 3 2 2 and Tables 1 6 in the HVAC BESTEST User s Manual Dry Zone and Wet Zone Series Cases E110 E200 The 13 other cases represent a set of fundamental mechanical equipment tests These cases test a program s ability to model unitary space cooling equipment performance under controlled load and weather conditions Given the underlying physical assumptions in the case definitions there is a mathematically provable and deterministic solution for
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25. rors which were fixed e Revealed algorithmic shortcomings which were improved or eliminated through the use of more rigorous calculations for certain components e In later versions caught newly introduced bugs before public release of updates Overall the application of this test suite has been extremely useful in debugging and verifying the DX cooling algorithms in EnergyPlus This paper summarizes the difficulties encountered and the benefits gained in applying the tests INTRODUCTION The International Energy Agency IEA HVAC BESTEST contains a set of analytical tests as well as a set of comparative results from seven other whole building simulation programs that participated in the IEA project Analytical tests compare a program s results to mathematical solutions for simple cases This is an excellent method to use for assessing the accuracy of results since there is only one solution for the case analyzed given the boundary conditions Comparative tests compare a program to itself or to other simulation programs Both types of testing accomplish results on two different levels both validation and debugging Validation is accomplished when the results of the test program compare favorably with the analytical results Debugging is accomplished when the results for certain cases do not compare favorably with the analytical results and then through systematic checking it is determined that the source of the difference is due
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