VRF Systems. VRF Systems versus Geothermal Systems

Transcription

1 VRF Systems VRF Systems versus Geothermal Systems

2 VRF Systems What is VRF? Variable Refrigerant Flow Variation on ductless mini split system Actually ductless multisplit system Multiple indoor evaporators (7-96 Mbtuh) Single (or up to 3 common headered) condensing unit(s) per circuit located outdoors Heat is transferred to and from space via refrigerant flow through the system

3 VRF Systems What is VRF? More complex than mini-splits Usually have multiple compressors (2 per unit) Many evaporators (up to 41 per circuit) Complex oil management system Complex (if communicable) control system Heat Pump (HP) type either heat or cool spaces 2 pipe system Heat Recovery (HR) type simultaneous heat/cool 3 pipe system

4 VRF Systems What is VRF? Term VRF refers to Ability of system to control amount of refrigerant to each zone (via electronic refrigerant valves) using variable capacity compressor(s). Each condensing unit has one digital scroll and one standard scroll compressor (multiple staged) Different capacity evaporators (7-96Mbtuh) Different configuration of evaporators Simultaneous heating and cooling of zones 3 pipe system only

5 VRF System Disadvantages Multiple compressors yield good part load efficiency but-- Only emulate on/off load matching of individual zone units Insulated HVACR copper pipes required to each zone 2 or 3 pipe systems. Expansive lengths of refrigerant tubing with massive number of joints required; ie- John Marshall Hotel(Richmond, VA) renovation of 239 guest rooms required estimated 30,000 ft. of tubing (over 5.5 miles!) And over 3,346 braze joints and 478 flare connections!

6 VRF System Disadvantages High probability of leaks; hundreds of field fabricated flare joints and several thousand brazed joints for 239 room system. No individual metering of power.

7 VRF System Disadvantages Efficiency is function of outdoor air temperature Reduces as ambient temps go up in cooling Reduces as ambient temps go down in heating DEFROST Not tied to exhaust air heat recovery Long refrigerant pipe runs (ie-john Marshall Hotel) Reduce capacity and efficiency Oil recovery cycle required

8 VRF System Disadvantages Specialized technicians required to startup, adjust, and repair systems; these technicians are typically limited in numbers and located in a Regional City. Is he and when is he going to be available to come to your jobsite when your equipment has problems and needs repairs?? Compare to vast numbers of small unitary equipment WSHP tradesman located in every city!

9 VRF System Disadvantages Complex oil management/recovery system; approximately every 6-9 hours an oil recovery cycle occurs in which all compressors are forced to full load and all electronic valves open fullyfans are reduced to minimum cfm. Cycle lasts 6-8 minutes.

10 VRF System Disadvantages Control system between outdoor and indoor units is proprietary; this means no independent controls contractor can service, or repair, or upgrade the control system-you are married to the manufacturer for the life of the system.

11 VRF System Disadvantages NO common source loop water energy exchange savings as with WSHP s. In partial or full heating seasons; WSHP units in cooling mode in interior zone heat up loop water which provides warmer water to perimeter zone units running in heating mode, and thus boiler (much lower heating efficiency) seldom runs.

12 VRF System Disadvantages What is the comfort level of air-cooled heat pump s supply air temperature in cold weather without supplemental electric heat or artificially elevated condenser pressure and temperatures? Standard 91 supply air temperature simply does not feel warm to occupants.

13 VRF versus Geothermal ClimateMaster did a simulation Comparison between VRF and GLHP on same building Found little information comparing the systems Most competitive technology to geothermal systemsnote that this is using printed unverified information in VRF pamplets. VRF versus Geothermal

14 VRF versus Geothermal ClimateMaster simulation Published in Heat Pump Centre Newsletter in 2009

15 VRF versus Geothermal Characteristics of VRF system modeled On site assembled large capacity air source heat pump with multiple evaporator coils Outdoor unit with multiple compressors with one variable speed compressor and air cooled condenser with variable speed fan Refrigerant piping at different lengths Multiple indoor units with electronic expansion valve, coil and constant speed fan Controller

16 VRF versus Geothermal Characteristics of VRF system modeled Simultaneous heating and cooling units (3 pipe) with supplemental electric heat was modeled System design and installation heavily rely on support from VRF manufacturer, as well as printed unverified/uncertified performance.

17 VRF versus Geothermal Challenges in Modeling VRF Systems Cooling / heating capacity and efficiency are affected by many factors Indoor and outdoor air temperatures (DB and WB) Defrosting operation Part-load condition Refrigeration system configuration Ratio of total indoor unit capacity to outdoor unit capacity

18 VRF versus Geothermal Challenges in Modeling VRF Systems Refrigerant pipeline layout (total length and level difference) Modeling heat recovery operationsimultaneous heating and cooling Account for performance loss from Oil return operation

19 VRF versus Geothermal Few tools available for VRF simulation Trace 700 VRFZ functions developed for DOE-2.1E are used in EnergyPro Rough approach for modeling heat recovery Account for impacts of outdoor air temperature, part load condition, defrost, and refrigerant line layout based on performance data/curves from VRF manufactures.

20 VRF versus Geothermal Comparison between VRF and GLHP One Building 360 sm office building at Chicago, IL Two systems VRF with supplemental electric heater Mitsubishi VRFZ system PURY-P126TGMU Simulated with DOE-2.1E and VRFZ function GLHP ClimateMaster TS036 water-to-air heat pump with ECM fan Simulated with equest and ClimateMaster performance data library

21 VRF versus Geothermal Capacities and efficiencies of systems--rated VRF Cooling EER at 33 C Heating COP at 3 C GSHP Actual Cooling EER at 25 C EFT Heating COP at 0 C EFT

22 Comparison between VRF and GLHP Two VRF scenarios HR mode with 25 ft (7.6 m)refrigerant line HR mode with 574 ft (175 m)refrigerant line Four energy use categories Space heating Space cooling Pump power Fan power

23 VRF versus Geothermal Impact of outdoor air temperature on VRF cool/heat capacity

24 VRF versus Geothermal Effect of outdoor air temperature on VRF capacity

25 VRF versus Geothermal Effect of entering fluid temperature on GSHP capacity

26 VRF versus Geothermal Effect of fluid temperature on GSHP efficiency

27 VRF versus Geothermal Impact of part load ratio on VRF cooling/heating efficiency

28 VRF versus Geothermal Effect of part load ratio on GSHP performance

29 VRF versus Geothermal Impact of refrigerant line length on VRF cool/heat capacity

30 VRF versus Geothermal Annual electric consumption comparison Short pipe length

31 VRF versus Geothermal Annual electricity consumption comparison VRF 29-36% more!

32 VRF versus Geothermal Let s look at actual examples of energy consumption of 3 nearly identical 70,000 sq. ft. Elementary Schools in Kentucky as recently presented at public forum at the High Performance School Seminar in Bowling Green, KY on March 22, These 3 schools were designed and constructed for purpose of comparing VRV to Water Source Heat Pumps/GLHP applications

33 VRF versus Geothermal Energy Results- System KBTU/SF Energy Cost VRF 32 $72,100 GEO $32,900 GEO2 7.5 $17,300

34 VRF versus Geothermal Mr. Jeremy Smith, Principal, CMTA in Lexington (offices in Louisville and Paducah) presented the data. The geothermal units are on single unit pumps to individual wells. Energy cost is based on KWH only; no demand. Unit performance and data collected over past 4 months and extrapolated for annual amounts. GEO2 presently being studied regarding controls to obtain lower KWH.

35 VRF versus Geothermal A well known engineer of integrity(does followup verification) in Paducah, KY has been analyzing performance of VRV vrs WSHP-GLHP; from his study he determines VRV operating at around 9.5 actual EER while WSHP-GLHP operating around EER; he is convinced that GSHP at least 30%+ more efficient.

36 Geothermal vs. VRF Comparison ASHRAE Headquarters Building

37 ASHRAE Headquarters Building

38 VRF versus Geothermal - ASHRAE HQ Building ASHRAE Recently released actual energy consumption of VRF vs ClimateMaster GSHP system in their Atlanta, GA headquarters and the data (VRF floor 1; GSHP floor 2) reveals significant savings of GSHP s.

39 Building Specifics Square footage of floor 1-18,510 sq. ft. Square footage of floor 2-15,290 sq. ft. Set point for each level - 68ºF Heating, 74ºF Cooling

40 Building Specifics Heating / cooling area for GSHPs 15,558 sq. ft. All zones on floor 2 and a corridor zone on floor 1 Heating / cooling area for VRF 18,226 sq. ft. All zones on floor 1 (minus corridor zone) and the learning center

41 Building Specifics Loads for GSHP system Heating: kbtu/hr Cooling: kbtu/hr All zones on floor 2 and a corridor zone on floor 1 Loads for VRF system Heating: kbtu/hr Cooling: kbtu/hr All zones on floor 1 (minus corridor zone) and the learning center

42 ClimateMaster Geothermal System Packaged Units Technical Office - Model # TTH038AGD28ULPS (Qty 2) Technical Office - Model # TTH038AGD28URPS (Qty 1) Publishing Office - Model # TTH038AGD28URPS (Qty 2) Pre-function Area - Model # TTH038AGD28ULPS (Qty 1) Pre- function Area / Stair #1 - Model # TTH026AGD28ULPS (Qty 1) Executive Conference Room - Model # TTH026AGD28ULPS (Qty 1) Publishing Office - Model # TTH026AGD28URPS (Qty 2) Break Room - Model # TTH026AGD28ULWS (Qty 1) Library - Model # TTH026AGD28URWS (Qty 1) Stair #2 - Model # TRC09AGSDXSVHRA (Qty 2)

43 Geothermal Loop Vertical closed-loop 12 bores at 400 feet deep with 1.25 HDPE Boreholes on 25 foot centers with bore field directly adjacent to the east side of the building Thermally enhanced grout Standard 2-pipe building loop with VFD pump

44 Daikin VRV III 3-pipe System Outdoor Units: 1st Floor Office area Model # REYQ168PTJU (REMQ96PTJU + REMQ72PTJU) Learning Center Model # REYQ168PTJU (REMQ96PTJU + REMQ72PTJU) Computer Room Model # RZQ36MVJU Vestibule Model # RXYMQ48MVJU Computer Room Model # RZQ36MVJU Branch Selector Boxes: Model # BSVQ36/60PVJU Fan Coil Units: 1st Floor Office area - Model # FXMQ30MVJU (Qty 2), FXMQ36MVJU (Qty 2), FXSQ18MVJU (Qty 2), FXSQ12MVJU(09) (Qty 2), FXSQ24MVJU Learning Center Model # FXMQ30MVJU, FXSQ18MVJU (Qty 4), FXSQ12MVJU (09) (Qty 6), FXMQ48MVJU, FXAQ07MVJU, FXSQ12MVJU Computer Room Model # FHQ36MVJU Vestibule Model # FXMQ48MVJU Computer Room Model # FHQ36MVJU

45 1st Level Floor Plan 812 sq. ft. 881 sq. ft sq. ft.

46 2nd Level Floor Plan

47 2010 Measured Power Usage 9,000.0 Geo HP vs VRF 2010 System Power (kwh) 8, , , , ,000.0 Geo HP VRF 3, , , Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec

48 2010 Ground Loop Temperature Average Ground loop temperature by Month Supply & Return Water Temperature Mar Apr May June July Aug Aept Oct Nov Dec Return WT Supply WT Outdoor Air Temp

49 2010 System Efficiency 2010 Energy usage for GSHPs 32,671.3 kwh Heating / cooling area for GSHPs 15,558 sq. ft. GSHP = 2.1 kwh / sq. ft Energy usage for VRF 60,061.1 kwh Heating / cooling area for VRF 18,226 sq. ft. VRF = 3.3 kwh / sq. ft. VRF consumed 57% higher yearly kw/sq. ft in ( )/2.1* 100 = 57%

50 2011 Measured Power Usage 8000 Geo HP vs VRF 2011 System Power (kwh) Geo HP VRF Jan Feb Mar Apr May June July August September October November December

51 2011 Ground Loop Temperature

52 2011 System Efficiency 2011 Energy usage for GSHPs 26,286.0 kwh Heating / cooling area for GSHPs 15,558 sq. ft. GSHP = 1.69 kwh / sq. ft Energy usage for VRF 56,568.1 kwh Heating / cooling area for VRF 18,226 sq. ft. VRF = 3.10 kwh / sq. ft. VRF consumed 84% higher annual kwh/sq. ft. in 2011 ( )/1.69* 100 = 84%

53 2012 Measured Power Usage 6000 Geo HP vs VRF 2012 System Power (kwh) Geo HP VRF January February March April May June July August September October November December

54 2012 Ground Loop Temperature Average Ground loop temperature by Month Supply & Return Water Temperature Jan Feb Mar Apr May June July Return WT Supply WT Outdoor Air Temp

55 2012 System Efficiency 2012 Energy usage for GSHPs 15, kwh (Jan July) Heating / cooling area for GSHPs 15,558 sq. ft. GSHP = 0.98 kwh / sq. ft Energy usage for VRF 28, kwh (Jan July) Heating / cooling area for VRF 18,226 sq. ft. VRF = 1.57 kwh / sq. ft. VRF consumed 75% higher annual kwh/sq. ft. in 2012 ( )/0.98* 100 = 59%

56 VRF versus Geothermal Summary VRF/VRV in reality consumes considerably higher energy consumption compared to printed exuberant high efficiencies touted for years that have driven their significant sales. Higher maintenance and service costs are anticipated.