Comparison of Three DIfferent Geothermal Loopfields
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Comparison of Three DIfferent Geothermal Loopfields

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Presented at the 2011 World Energy Engineering Conference, Chicago, IL

Presented at the 2011 World Energy Engineering Conference, Chicago, IL

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Comparison of Three DIfferent Geothermal Loopfields Comparison of Three DIfferent Geothermal Loopfields Presentation Transcript

  • Comparison of Three Different Geoexchange Loopfields Daniel W. Felten, P.E., CGD World Energy Engineering Conference October 2011
  • Background ECS purchased abandoned factory in 2007. Terraclime Geothermal began business operations in 2009 Redeveloped 3rd floor (7,000 SF) for our offices Needed our first geothermal project to get The “Mill” going!!! Florence, MA
  • Geothermal Demonstration Site Design Industry standard “U-Loop” has been around for decades. It works, but… ◦ High drilling costs (150 to 200 ft of borehole per Ton) ◦ Grouting with high TC grout costly ◦ Land “hog” with 2 to 3 Tons (500 ft) every 20-25 ft ◦ Many competitors installing U-Loops Thermacouple and DX offered enticing claims with limited penetration in the market…
  • Thermacouple Claim:A Thermacouple earth energy system…allows theearth to exchange up to 5 tons of thermal energy…”
  • Reducing Drilling Requirements ◦ Kelix Thermacouple could reduce drilling depth by more than 60% (if claim true) ◦ One 306 foot Kelix can provide “up to” 5 Tons of heating/cooling
  • Earthlinked DX System Claim“Typically, the earth loops are 100 feet per ton ofcapacity.”
  • Reducing Drilling Requirements ◦ Direct Exchange (DX) uses refrigerant in copper earth loops ◦ One ton per 100 feet of borehole ◦ 3 inch diameter borehole means quicker drilling and less grouting, less disturbance
  • Final Systems Configuration 5 Tons Direct Exchange (DX) ◦ Single stage Cu ground loops ◦ Manufacturer - EarthLinked Technologies 5 Tons Water Based “U-Loop” 5 Tons Water Based Concentric Tube “Kelix Thermacouple” Outside water systems interchangeable ◦ U-Loop 2 x 500’ / Thermacouple 306’ Water Based Manufactures: Carrier & WaterFurnace Data Acquisition using Web Energy Logger (WEL)
  • Drilling U-Loop Two 500-foot boreholes, 6” diameter, 1000 feet total Bentonite sand grout HDPE Tubing 25% EtOH 2.5 days to complete 5 Tons Total $12/Ft = $12,000
  • Installing Loops Damaged U-LoopU-Loop Installation
  • Installing KELIX Thermacouple  One 306-foot borehole, 6” diameter  Geo Supergrout ◦ Cementicious TC=1.0  4” diameter outer casing  1.5 days to complete ◦ recent modifications has reduced install time to 0.5 – 1 day)  5 Tons Total  $14/Ft X 306 ft = $4,384  Plus, $5,500 materials  Total Cost = $9,884
  • Thermacouple (Casing and Head)
  • Thermacouple Field Fabrication
  • Thermacouple – Finished Wellhead
  • Drilling DX Boreholes  Five 100- foot holes, 3” diameter  Geo Supergrout  Copper Earthloops  One day to complete  $2000/Ton = $10,000
  • Smaller DX Drill Rigs
  • DX Earthloop (Earthlinked)
  • Drill Tooling and DX Earthloop Copper Earthloops
  • DX Manifolds
  • DX Exposed Manifold ManifoldsFive 100’ Earth Loops
  • DX Linesets (Interior) DX Linesets (Exterior)DX Installation (at the Mill)
  • Real Time Monitoring and DataAcquisition-Web Energy Logger (WEL) Real Time Monitoring and Data Acquisition ◦ Temps ◦ Pressures ◦ Flows ◦ Watts Performance Reporting ◦ COP/EER ◦ Troubleshooting
  • Data Acquisition & Analysis Each system is instrumented at key locations ◦ Ground Loop (temps and flows) ◦ Air Handler (temps) ◦ Geo System (temps, pressures, amps) ◦ Ambient air & earth temps Data acquired at one minute intervals (NOTE: DON’T TRY THIS AT HOME!) Systems were started up July 2009
  • http://welserver.com/WEL0201/
  • DX System Performance Summary DX Modification ProgressionCOP Heat < 3 •Original installation, R407c •Pressure Oscillations due to component sizing mismatch, refrigerant characteristicsCOP/EER Cooling •R407c changed to R22~3.3/11.3 •Flow control changedCooling capacity 5 •Glide eliminatedTons confirmed •System pressure losses remain due to distribution & volume
  • DX (Direct Exchange)
  • Mill Systems Performance Summary Water Based Systems Water Systems CommentsCarrier COP/EER •R410a Two-Stage compressor option< 6/20+ provides max performance benefit by rejecting condensing heat @ 90F into ground @ 56F operating in 1st stageWF COP/EER •R410a & Two Stage similar max benefit~6/20+ •North side building provides cooling advantage
  • Water (25% Ethanol) COP 3.5 – 4.1 (heating) 5.5 – 6.1 (cooling)(ground systems interchangeable with geothermal systems)
  • Thermacouple Cooling Performance
  • Comparative Analysis - Cooling
  • Normalizing Data - BTU vs. ∆ EWT U-Loop ◦ Initial EWT = 56 F ◦ Max EWT = 69 ◦ Delta EWT = 13 F over 72 minutes ◦ Total BTU Rejected = 93,000 BTU ◦ Rate = 6.5 Tons Kelix Thermacouple ◦ Initial EWT = 65 F ◦ Max EWT = 85 F ◦ Delta EWT = 20 F over 72 minutes ◦ Total BTU Rejected = 77,000 BTU ◦ Rate = 5.3 Tons50% greater EWT rise with 20% less BTU rejected
  • Normalizing Data
  • Capacity Evaluation Normalized to a Delta EWT = 13F(eg., how many BTUs does it take to get a 13 degree delta) ◦ U-Loop: 93,000 BTU (@ 6.6 Tons) ◦ Kelix: 35,000 BTU (@ 5.4 Tons) Thermacouple Equivalent Capacity (relative to U- Loop) = 0.376 Kelix Capacity = 0.376 X 6.6 Tons = 2.5 Tons Equivalent to 120 feet/Ton U-Loop at 152 ft/Ton Thermacouple is ~20% more efficient?
  • Is this a valid analysis? 15 minutes •These two geothermal systems rarely cycled for 72 minutes •The majority of cycles for both systems were under 15 minutes
  • It’s the ground, stupid… We can force heat into/from the ground using earthloop “improvements” The shorter the borehole, the greater the thermal gradient required The “improvements” are really about eliminating borehole resistance
  • Decreasing Borehole Resistance andIncreasing Efficiency Thermacouple ◦ Greater turbulence with lower pressure drop (reduced pumping penalty) ◦ Minimizes “cross talk” between inlet/outlet piping (PVC inner pipe) ◦ Better Grout: TC >1.0 vs 0.8 ◦ More Conductive Casing: Fiberglass vs HDPE Direct Exchange ◦ Highly conductive copper earthloop ◦ Better Grout ◦ No pumping penalty (other penalties may apply…)
  • Decreasing Borehole Resistance andIncreasing Efficiency U-Loop systems work well and are easy to install DX and Thermacouple are viable alternatives for smaller sites and/or higher drilling costs The manufacturer claims should be ignored - ground performance drives the system design Need to develop equivalent models for DX and Thermacouple
  • System Comparisons