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January 17, 2007
Harvard Univeristy Operations Services: GSHP Lessons Learned 1
Ground Source Heat Pumps at Harvard
LESSONS LEARNED
Presented by University Operations Services:Environmental Health and SafetyFacilities Maintenance Operations
Green Campus Initiative
©2007, Harvard UOS
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
January 17, 2007
Harvard Univeristy Operations Services: GSHP Lessons Learned 2
©2007, Harvard UOS
Are GSHPs Good for Harvard?
Operations and MaintenanceEnvironmental
Aesthetic
©2007, Harvard UOS
Advantages of GSHPs
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)
Environmental Benefits
January 17, 2007
Harvard Univeristy Operations Services: GSHP Lessons Learned 3
©2007, Harvard UOS
Advantages of GSHPs
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
O&M Benefits
©2007, Harvard UOS
Advantages of GSHPs
No cooling towers or other HVAC equipment on roofs
No noise from HVAC equipment
Aesthetic Benefits
January 17, 2007
Harvard Univeristy Operations Services: GSHP Lessons Learned 4
©2007, Harvard UOS
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
January 17, 2007
Harvard Univeristy Operations Services: GSHP Lessons Learned 5
©2007, Harvard UOS
Types of GSHP Systems
Standing Column WellUses a surface or underground water source (lake, river, or well) as both the heat source and the heat sink
Uses the earth as the heat source and heat sink with anti-freeze additive to the loop water
Closed Loop
Open Loop
All existing installations at Harvard are open loop, standing column wells!
©2007, Harvard UOS
Layout of a Typical Standing Column Well Installation at Harvard
January 17, 2007
Harvard Univeristy Operations Services: GSHP Lessons Learned 6
©2007, Harvard UOS
Perforated Intake Area
Pump
4” PVC Sleeve
Water Table
Well HeadPump Electrical Wire
To Heat PumpFrom Heat Pump
8” Steel Casing
Soil
~ 100’ to pump
Bed Rock
500’ to 1500’
©2007, Harvard UOS
Water Discharge from Formation
Reg
iona
l Gro
undw
ater
Flo
w
From Heat Pump
To Heat Pump
Bleed Water
January 17, 2007
Harvard Univeristy Operations Services: GSHP Lessons Learned 7
©2007, Harvard UOS New Water from Earth
Bleed Line
Understanding Bleed
To raise or lower well water temperature, a portion of return water can be “bled”from the top of the well
This allows fresh water to enter the well column, raising or lowering the temperature of the well
Bleed water must then be reused or disposed of
Return from Heat Pump
Supply to Heat Pump
©2007, Harvard UOSTypical water-to-water heat pumps (30 tons each)
Internal refrigeration cycle generates chilled
or hot water to condition the building
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Harvard Univeristy Operations Services: GSHP Lessons Learned 8
©2007, Harvard UOS
Harvard Well Inventory
Yes680N/ANo50088Weld Hill (Closed Loop)
Yes210100Yes15003Byerly HallFuture Projects
No15003Zero Arrow Street
Yes160100Yes750, 85021 Francis Ave.
Yes160100Yes15002Radcliffe Gym
Yes270100Yes450 - 650390 Mount Auburn
Yes180100Yes15002QRAC
Yes180110Yes15002Blackstone
VFDs*Pump
Capacity(GPM)
Pump Depth(feet)
Designed to Bleed
Depth(feet) Wells
* Variable Frequency Drives allow a pump to run at partial capacity, which reduces energy costs
Part II: Lessons Learned from Current Campus Installations
January 17, 2007
Harvard Univeristy Operations Services: GSHP Lessons Learned 9
©2007, Harvard UOS
Design
Installation
O&M
Lessons and Recommendations
©2007, Harvard UOS
Know the condition and temperature of the groundwater
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
Design Lesson 1
Learned From: 46 Blackstone, QRAC, Radcliffe Gym
January 17, 2007
Harvard Univeristy Operations Services: GSHP Lessons Learned 10
©2007, Harvard UOS
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/ft1500’ well would cost $150,000
RecommendationsDesign Lesson 1
©2007, Harvard UOS
Install a Coupon Rack with the following Coupons:Copper
Iron
Stainless Steel
Bacteria
Ever thirty days have a authorized Chemical Company analyze the coupons
RecommendationsDesign Lesson 1
Copper Coupon
StainlessCouponIron
Coupon
January 17, 2007
Harvard Univeristy Operations Services: GSHP Lessons Learned 11
©2007, Harvard UOS
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
Understand the function of the well as a heat exchanger
Design Lesson 2
Learned at 90 Mt Auburn
©2007, Harvard UOS
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
RecommendationsDesign Lesson 2
www.bestwaterwelldriller.com
January 17, 2007
Harvard Univeristy Operations Services: GSHP Lessons Learned 12
©2007, Harvard UOS
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 StreetSpecifically designed not to bleed
Achieved by upsizing well capacity
Understand the relationship between heat exchange capacity of the well and bleed
Design Lesson 3
Learned at all projects
©2007, Harvard UOS
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 water reuse options have been identified
Disposal of bleed water introduces regulatory issues and potential added cost
RecommendationsDesign Lesson 3
www.dcs1.com
January 17, 2007
Harvard Univeristy Operations Services: GSHP Lessons Learned 13
©2007, Harvard UOS
Metering and controls are critical
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
Design Lesson 4
Learned at 90 Mt Auburn, QRAC, Radcliffe Gym, 1 Francis
©2007, Harvard UOS
RecommendationsSpecify 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!
Design Lesson 4
January 17, 2007
Harvard Univeristy Operations Services: GSHP Lessons Learned 14
©2007, Harvard UOS
Pipe had to be cut and removed in 10’
sections
Learned at 90 Mt Auburn
Site wells appropriatelyDesign Lesson 5
Well head under overhang
Well Access
©2007, Harvard UOS
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
RecommendationsDesign Lesson 5
January 17, 2007
Harvard Univeristy Operations Services: GSHP Lessons Learned 15
©2007, Harvard UOS
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
Refrigerant selection should be carefully considered
Design Lesson 6
©2007, Harvard UOS
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
RecommendationsDesign Lesson 6
January 17, 2007
Harvard Univeristy Operations Services: GSHP Lessons Learned 16
©2007, Harvard UOS
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
Learned at 90 Mt Auburn
Understand piping and balancing issuesInstall Lesson 1
©2007, Harvard UOS
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 all systems
RecommendationsInstall Lesson 1
www.nj.com
January 17, 2007
Harvard Univeristy Operations Services: GSHP Lessons Learned 17
©2007, Harvard UOS
At Blackstone, a well was short 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
Learned at Blackstone and 90 Mt Auburn
diagram
Positioning of the sleeve and return piping impact performance
Install Lesson 2
*Not to scale
©2007, Harvard UOS
Utilize an owner’s acceptance process to verify proper installation, start up, and turnover of equipment
RecommendationsInstall Lesson 2
January 17, 2007
Harvard Univeristy Operations Services: GSHP Lessons Learned 18
©2007, Harvard UOS
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
Prevent solvents from entering groundwater
Install Lesson 3
Learned at Blackstone
©2007, Harvard UOS
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
RecommendationsInstall Lesson 3
January 17, 2007
Harvard Univeristy Operations Services: GSHP Lessons Learned 19
©2007, Harvard UOS
Iron sludge from strainer at Radcliffe Gym
Plugged strainers at Radcliffe Gym caused evaporators to freeze and heat pumps to failWarranties do not cover damage caused by improper maintenance!
Maintenance starts on Day One!O&M Lesson 1
Learned at Radcliffe Gym and QRAC
©2007, Harvard UOS
Radcliffe Gym: Heat Pump Condenser
Deformation from freezing
Normal plate design
Plate deformed –Honey Comb
January 17, 2007
Harvard Univeristy Operations Services: GSHP Lessons Learned 20
©2007, Harvard UOS
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
RecommendationsO&M Lesson 1
©2007, Harvard UOS
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
Do not put bleach into wells!O&M Lesson 2
Learned at all sites
January 17, 2007
Harvard Univeristy Operations Services: GSHP Lessons Learned 21
©2007, Harvard UOS
Environmental Considerations
©2007, Harvard UOS
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
Identify and examine all permittingimplications during design
Design Lesson 7
January 17, 2007
Harvard Univeristy Operations Services: GSHP Lessons Learned 22
©2007, Harvard UOS
Consult with Harvard EH&S early in the design process
Carefully assess permit applicability and requirements
RecommendationsDesign Lesson 7
©2007, Harvard UOS
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)
Other Environmental Considerations
“The first ten feet can kill you”