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Harvard Geothermal Case Study

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  • 1. January 17, 2007 Ground Source Heat Pumps at Harvard LESSONS LEARNED Presented by University Operations Services: Environmental Health and Safety Facilities Maintenance Operations Green Campus Initiative 1. Part I: Are GSHPs Good for Harvard? 2. Part II: How GSHPs Work 3. Part III: Lessons Learned from Current Campus Installations 4. Questions ©2007, Harvard UOSHarvard Univeristy Operations Services: GSHPLessons Learned 1
  • 2. January 17, 2007 Are GSHPs Good for Harvard? Operations and Environmental Maintenance Aesthetic ©2007, Harvard UOS Advantages of GSHPs Environmental Benefits Use less energy than conventional HVAC systems Can significantly reduces emissions of greenhouse gasses by using “free” energy from the earth Can be more efficient than conventional heating systems Up to 44% more efficient than air source heat pumps, 72% more efficient than electrical resistance heating (Source: DOE) ©2007, Harvard UOSHarvard Univeristy Operations Services: GSHPLessons Learned 2
  • 3. January 17, 2007 Advantages of GSHPs O&M Benefits Lower energy costs than conventional air source cooling 20-50% reduction in energy bills (Source: EPA) Lower maintenance costs No equipment is exposed to weather Fewer moving parts to fail ©2007, Harvard UOS Advantages of GSHPs Aesthetic Benefits No cooling towers or other HVAC equipment on roofs No noise from HVAC equipment ©2007, Harvard UOSHarvard Univeristy Operations Services: GSHPLessons Learned 3
  • 4. January 17, 2007 GSHPs Can Be Good For Harvard Properly designed, installed, and maintained systems can be an effective alternative to conventional heating and cooling technology Appropriately scaled GSHP systems can be a successful part of Harvard’s energy portfolio ©2007, Harvard UOS Part II: How GSHPs Work ©2007, Harvard UOSHarvard Univeristy Operations Services: GSHPLessons Learned 4
  • 5. January 17, 2007 Types of GSHP Systems Closed Loop Uses the earth as the heat source and heat sink with anti-freeze additive to the loop water All existing installations at Harvard are open loop, standing column wells! Open Loop Uses a surface or Standing Column Well underground water source (lake, river, or well) as both the heat source and the heat sink ©2007, Harvard UOS Layout of a Typical Standing Column Well Installation at Harvard ©2007, Harvard UOSHarvard Univeristy Operations Services: GSHPLessons Learned 5
  • 6. January 17, 2007 Pump Electrical Wire Well Head From Heat Pump Soil To Heat Pump ~ 100’ to pump 8” Steel Casing Water Table 4” PVC Sleeve Pump 500’ to 1500’ Bed Rock Perforated Intake Area ©2007, Harvard UOS Bleed Water From Heat Pump To Heat Pump Regional Groundwater Flow Water Discharge from Formation ©2007, Harvard UOSHarvard Univeristy Operations Services: GSHPLessons Learned 6
  • 7. January 17, 2007 Understanding Bleed To raise or lower well water temperature, a portion of ne d Li lee return water can be “bled” B from the top of the well Return from Heat Pump This allows fresh water to Supply to Heat Pump enter the well column, raising or lowering the temperature of the well Bleed water must then be reused or disposed of ©2007, Harvard UOS New Water from Earth Internal refrigeration cycle generates chilled or hot water to condition the building Typical ©2007, Harvard UOS water-to-water heat pumps (30 tons each)Harvard Univeristy Operations Services: GSHPLessons Learned 7
  • 8. January 17, 2007 Harvard Well Inventory Pump Pump Depth Designed Wells Depth Capacity VFDs* (feet) to Bleed (feet) (GPM) Blackstone 2 1500 Yes 110 180 Yes QRAC 2 1500 Yes 100 180 Yes 90 Mount Auburn 3 450 - 650 Yes 100 270 Yes Radcliffe Gym 2 1500 Yes 100 160 Yes 1 Francis Ave. 2 750, 850 Yes 100 160 Yes Zero Arrow Street 3 1500 No Future Projects Byerly Hall 3 1500 Yes 100 210 Yes Weld Hill 88 500 No N/A 680 Yes (Closed Loop) ©2007, Harvard UOS * Variable Frequency Drives allow a pump to run at partial capacity, which reduces energy costs Part II: Lessons Learned from Current Campus InstallationsHarvard Univeristy Operations Services: GSHPLessons Learned 8
  • 9. January 17, 2007 Lessons and Recommendations Design Installation O&M ©2007, Harvard UOS Design Know the condition and temperature Lesson 1 of the groundwater Learned From: 46 Blackstone, QRAC, Radcliffe Gym Heat pumps and piping were not designed for brackish water Ground water at the Blackstone site is 64 degrees not 55 degrees as predicted by the project engineer Well water heats up quickly and can reach more than 90 degrees during peak summer periods Dramatically affected bleed rate and disposal strategy A geotechnical engineer may not be able to accurately predict groundwater conditions ©2007, Harvard UOSHarvard Univeristy Operations Services: GSHPLessons Learned 9
  • 10. January 17, 2007 Design Lesson 1 Recommendations Identify local water conditions before making piping and heat pump selections All Harvard wells installed at 1500’ have brackish water All Harvard wells have some level of iron in the water Native water temperature is only know for the Blackstone site (64 degrees) Consider phasing construction so that wells are completed before pipe and equipment selection or drill a test well Average cost to drill a well is ~$100/ft 1500’ well would cost $150,000 ©2007, Harvard UOS Design Lesson 1 Recommendations Install a Coupon Rack with the following Coupons: Copper Iron Copper Stainless Steel Coupon Bacteria Stainless Iron Coupon Coupon Ever thirty days have a authorized Chemical Company analyze the coupons ©2007, Harvard UOSHarvard Univeristy Operations Services: GSHPLessons Learned 10
  • 11. January 17, 2007 Design Understand the function of the Lesson 2 well as a heat exchanger Learned at 90 Mt Auburn Wells were designed to be 1500’ each Drilling stopped at approximately 550’ once water flow rate was sufficient Many well drillers are accustomed to drilling extraction wells, where only flow rate is important ©2007, Harvard UOS Design Lesson 2 Recommendations Do not short drill! Short drilling reduces the heat exchange capacity of the well ▫ Likely to necessitate more frequent bleeding ▫ Reduces the overall output capacity of the system ▫ 90 Mt Auburn bled all summer long www.bestwaterwelldriller.com ©2007, Harvard UOSHarvard Univeristy Operations Services: GSHPLessons Learned 11
  • 12. January 17, 2007 Design Understand the relationship between heat Lesson 3 exchange capacity of the well and bleed Learned at all projects 46 Blackstone (bleeds more than designed) Native water temperature was 9 degrees higher than expected ▫ Set points for bleed had to be raised to avoid continuous bleed ▫ Bleed is still double the design volume ▫ Warmer water reduced efficiency of the heat pumps 2 Arrow Street Specifically designed not to bleed Achieved by upsizing well capacity ©2007, Harvard UOS Design Lesson 3 Recommendations Design your system for zero bleed Include in construction specifications and enforce the requirement! Preferred strategy is to upsize heat exchange capacity of the well field (drill an extra well) Due to salinity at 1500’ depth, no bleed www.dcs1.com water reuse options have been identified Disposal of bleed water introduces regulatory issues and potential added cost ©2007, Harvard UOSHarvard Univeristy Operations Services: GSHPLessons Learned 12
  • 13. January 17, 2007 Design Lesson 4 Metering and controls are critical Learned at 90 Mt Auburn, QRAC, Radcliffe Gym, 1 Francis Without metering, well performance and bleed rate is unknown Without monitoring well water supply and return flows, it is possible to draw the water level below the pump At 90 Mt Auburn one pump was destroyed and needed to be replaced at a cost of $9K ©2007, Harvard UOS Design Lesson 4 Recommendations Specify and install adequate well monitoring and controls Flow rate and temperature on supply/return and bleed Integrate with building automation controls Provides capability to diagnose problems, trend well performance, and collect compliance data Resist temptation to eliminate controls and metering during Value Engineering! ©2007, Harvard UOSHarvard Univeristy Operations Services: GSHPLessons Learned 13
  • 14. January 17, 2007 Design Lesson 5 Site wells appropriately Learned at 90 Mt Auburn Well head under overhang Pipe had to be cut and removed in 10’ sections Well Access ©2007, Harvard UOS Design Lesson 5 Recommendations Allow for future access to wells for maintenance and repairs Consider well spacing when reviewing the site plan Thermal interactions between closely spaced wells can reduce efficiency ©2007, Harvard UOSHarvard Univeristy Operations Services: GSHPLessons Learned 14
  • 15. January 17, 2007 Design Refrigerant selection should be Lesson 6 carefully considered R-410A, the environmentally preferable refrigerant, has a smaller working range than conventional R-22 (which is being phased out) Heat pumps operating with R-410A can handle water up to 95 degrees before shutting down Heat pumps operating with R-22 can handle water up to 105 degrees ©2007, Harvard UOS Design Lesson 6 Recommendations Avoid R-22 refrigerant, if possible 2010 no new equipment manufactured with R-22 2020 no new R-22 will be produced Warmer condenser water reduces heat pump efficiency ©2007, Harvard UOSHarvard Univeristy Operations Services: GSHPLessons Learned 15
  • 16. January 17, 2007 Install Lesson 1 Understand piping and balancing issues Learned at 90 Mt Auburn Poorly designed pipe runs prevented water from returning evenly to the three wells This imbalance in water flow reduced the design capacity from 150 to 120 tons Ongoing problems have prevented full commissioning of the building ©2007, Harvard UOS Install Lesson 1 Recommendations Insist on Coordination Drawings prior to layout and installation of piping Develop an owner’s acceptance process to ensure proper balancing and full commissioning of www.nj.com all systems ©2007, Harvard UOSHarvard Univeristy Operations Services: GSHPLessons Learned 16
  • 17. January 17, 2007 Install Positioning of the sleeve and return piping Lesson 2 impact performance Learned at Blackstone and 90 Mt Auburn At Blackstone, a well was short diagram cycling because the sleeve was installed below the water level Return water was entering the supply feed At 90 Mt Auburn, return water pipe was incorrectly installed above the water level and had to be repositioned ©2007, Harvard UOS *Not to scale Install Lesson 2 Recommendations Utilize an owner’s acceptance process to verify proper installation, start up, and turnover of equipment ©2007, Harvard UOSHarvard Univeristy Operations Services: GSHPLessons Learned 17
  • 18. January 17, 2007 Install Prevent solvents from entering Lesson 3 groundwater Learned at Blackstone Ensure that adhesives on PVC well piping are fully cured so that VOCs (from solvents) are not introduced into groundwater Most well drillers do not allow proper curing of adhesives before installing PVC well pipe ©2007, Harvard UOS Install Lesson 3 Recommendations Ensure construction specifications require PVC adhesives to be fully cured before the pipe enters the well (or use alternative joining method) Monitor pipe joining process in field to ensure compliance with specifications ©2007, Harvard UOSHarvard Univeristy Operations Services: GSHPLessons Learned 18
  • 19. January 17, 2007 O&M Lesson 1 Maintenance starts on Day One! Learned at Radcliffe Gym and QRAC Plugged strainers at Radcliffe Gym caused evaporators to freeze and heat pumps to fail Warranties do not cover damage caused by improper maintenance! Iron sludge from strainer at Radcliffe Gym ©2007, Harvard UOS Radcliffe Gym: Heat Pump Condenser Normal plate design Plate deformed – Honey Comb Deformation from freezing ©2007, Harvard UOSHarvard Univeristy Operations Services: GSHPLessons Learned 19
  • 20. January 17, 2007 O&M Lesson 1 Recommendations Have a preventative maintenance plan in place before your system comes online Clean strainers frequently, especially during the first months of operation Require installing contractor or manufacturer to train Harvard building operations team on primary equipment prior to start up ©2007, Harvard UOS O&M Lesson 2 Do not put bleach into wells! Learned at all sites Many well consultants recommend periodically adding bleach directly to well water to sterilize the well This may be harmful to groundwater supply Bleach poured into the well can enter the aquifer ©2007, Harvard UOSHarvard Univeristy Operations Services: GSHPLessons Learned 20
  • 21. January 17, 2007 Environmental Considerations ©2007, Harvard UOS Design Identify and examine all permitting Lesson 7 implications during design Regulatory processes for GSHP systems are not well defined or developed Re-injection of groundwater may require a permit from DEP MWRA is currently reviewing bleed water discharge to its system ©2007, Harvard UOSHarvard Univeristy Operations Services: GSHPLessons Learned 21
  • 22. January 17, 2007 Design Lesson 7 Recommendations Consult with Harvard EH&S early in the design process Carefully assess permit applicability and requirements ©2007, Harvard UOS Other Environmental Considerations “The first ten feet can kill you” Drilling into urban fill (8-30’) in the Boston area can uncover historical soil or groundwater contamination Re-use displaced soil from well on-site whenever possible Carefully review any recommended additives (e.g. bleach) ©2007, Harvard UOSHarvard Univeristy Operations Services: GSHPLessons Learned 22