harvard geothermal case study

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


©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


©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


©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


©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


©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


©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

January 17, 2007


©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


©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


©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


Copper Coupon

StainlessCouponIron

Coupon

January 17, 2007


©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


www.bestwaterwelldriller.com

January 17, 2007


©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


www.dcs1.com

January 17, 2007


©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


©2007, Harvard UOS

Pipe had to be cut and removed in 10’

sections


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


January 17, 2007


©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


January 17, 2007


©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


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


©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


January 17, 2007


©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


January 17, 2007


©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


©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


©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


©2007, Harvard UOS

Consult with Harvard EH&S early in the design process

Carefully assess permit applicability and requirements


©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”

harvard geothermal case study

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