Phoenix Convention Center • Phoenix, Arizona

Underground Thermal Energy Storage (UTES)

Energy Technologies HVAC Technologies

Chuck Hammock PE, LEED BD+C, CGDAndrews Hammock & Powell, Inc.-Consulting Engineers

August 12, 2015

Energy Exchange: Federal Sustainability for the Next Decade

• “Direct-Use” (American) Geothermal Heat Pumps (GHP) Architecture vs. Geothermal designed for true Thermal Storage (typically only done outside the US)

• UTES: Underground Thermal Energy Storage can store heat or cold, diurnally or seasonally– Aquifer Thermal Energy Storage (ATES) Systems– Borehole Thermal Energy Storage (BTES) Systems– UTES increases the efficiency of traditional (US style) GHP

systems

• ESTCP UTES Projects• Layered Thermal

Conductivity Testing (LTCT) • Distributed Temperature

Sensing (DTS)

Presentation Outline

Energy Exchange: Federal Sustainability for the Next Decade

• “Direct Use”: Typical American closed loop piped in a grid with parallel flow or is a one-way open loop that can’t capture waste heat/cold

• With UTES, Geology is still used at heat sink & heat source, but BTES/ATES is optimized to deliberately store cold or hot.

• Closed loop UTES (BTES) boreholes generally piped as 3-6 boreholes in series for deliberate thermal stratification or zones (bull's-eye)

• Open Loop UTES (ATES) or BTES has the capability to reverse the flow to “charge” or “discharge” its stored thermal resource

Primary Differences of “Direct Use” Geothermal Vs. UTES Geothermal

Energy Exchange: Federal Sustainability for the Next Decade

Germany’s VDI-4640 Guidelines

Underground Thermal Energy Storage Guidelines

Energy Exchange: Federal Sustainability for the Next Decade

• Cooling Dominated Buildings: Capturing the “cold” of winter and storing it in underground formations or aquifers and “harvesting” it in summer to cool the building

• Heating Dominated Buildings: Capturing the “hot” of summer and storing it in underground formations or aquifers and “harvesting” it in winter to heat the building

• Balanced Buildings: Do Both, especially with ATES• Diurnal Load Variation? Do Diurnal Storage• Seasonal Load Variation? Do Seasonal Storage. In

reality most building obviously have both conditions

Building Thermal Characteristics

Energy Exchange: Federal Sustainability for the Next Decade© 2015 by AH&P- Cannot be used without permission

Energy Exchange: Federal Sustainability for the Next Decade

Approximate Groundwater Temperature Isotherms

Energy Exchange: Federal Sustainability for the Next Decade

Aerial View of the Ft. Benning Building/ATES Site

Energy Exchange: Federal Sustainability for the Next Decade

Section/Detail of ATES Extraction and Injection Well

Monitoring Well Piping

Intake Filter Screen with “Gravel” Pack

Submersible Pump

Injection Valve

© 2015 by AH&P/IFT- Cannot be used without permission

Natural Gamma Radiation: CPS

Confining Clay Layer

Energy Exchange: Federal Sustainability for the Next Decade

Adiabatic Dry Cooler for BTES/ATES

Adiabatic Dry-Cooler with: Evaporative Cooling Pads @ Coil Inlets. 18 Compartmentalized ECM Fans. (360 to 1 turndown), Modbus Interface

Application Heat Reject. COP

AirCooledDX 100

BTES Max 1616

BTES Winter 200-1600

BTES Yr. Ave 200-300

Annual Water Reduction

BTES 80-100%

Energy Exchange: Federal Sustainability for the Next Decade© 2015 by AH&P- Cannot be used without permission

Energy Exchange: Federal Sustainability for the Next Decade

Energy Exchange: Federal Sustainability for the Next Decade

13 Dec 2014 Google Earth Image

Satellite Imagery of MCLB BTES System Under Construction

13 2

Energy Exchange: Federal Sustainability for the Next Decade

BTES Construction Activities

The two 30’ high “mountains” in the woods/distance are actually the 20,000+ yd3 of earth temporarily removed for the BTES

Installation

BTES: Outer Circular Headers(foreground), Radial Sub-mains (center)

BTES Reversing Valves

Energy Exchange: Federal Sustainability for the Next Decade

Modular Heat Recovery Chiller

Energy Exchange: Federal Sustainability for the Next Decade

Layered Thermal Conductivity Test (LTCT) or Distributed Thermal Response Test (DTRT)

• Possibly first ever conducted in US

• Marines Corps Logistics Base, Albany GA (MCLB)

• 110 m u-bend borehole heat exchanger adjacent to BTES

• A 72 hours LTCT was conducted between May 12 and 14, 2015 and heat pulse tracked via DTS. Layer-by-layer K values measured

Energy Exchange: Federal Sustainability for the Next Decade

Layered Thermal Condutivity Test (LTCT)Downhole Temperatures

Bottom of the U-Bend(Axis of Symmetry)

Inlet Water into the U-Bend (surface)

Outlet water from the U-bend (surface)

Possible Groundwater Flow

This contour diagram shows the fluid temperature along the whole heat exchanger over the time observed. Right high side is after elements de-energized

Energy Exchange: Federal Sustainability for the Next Decade

Sections 1 and 4present the highest thermal conductivity.

Temperature profiles during thermal recovery indicate possible presence of groundwaterflow in region 4

Borehole resistance is”low” considering the large borehole diameter

2,28

1,67

1,58

2,24

1,86

1,67

1,59

1,61

1,88

0,070

0,11

0,12

0,07

0,10

0,11

0,12

0,11

0,09

1

2

3

4

5

6

7

8

9

Thermal conductivity [W/mK] Borehole resistance [K/(W/m)]

Summary: LTCT Results

Energy Exchange: Federal Sustainability for the Next Decade

Distributed Temperature Sensing (DTS)

Show BTES DTS Video (time permitting)

Energy Exchange: Federal Sustainability for the Next Decade

• Allows you to take same basic open or closed loop GEO that has been used for years and increase its efficiency, if properly modeled/engineered

• Via Cold Capture or Hot Capture, allows Geo to move beyond energy efficiency to a truly renewable architecture.

• Can eliminate cooling tower water usage, which general far exceeds domestic water use (3-6M gal)

• Proven technology used outside of the US for decades. Beyond superior source/sink, real storage

• “Direct chilled water” UTES systems, in the right climate(<52ºF ground temp), can reduce cooling KWH by 85%

Why use ATES or BTES vs. Standard Open and Closed Loop GEO at Federal

Facilities??

Energy Exchange: Federal Sustainability for the Next Decade22

• Utilize GHPs with UTES, when you need to reduce KWH/KWD/Energy $’s/Water/On-site Emissions

• BTES is 50 state tech, ATES is aquifer dependent• GHPs/UTES can serve a building via small unitary

(water-to-air) GHPs or central chilled/hot water• Space HW heat most eff. if low temp./heat recovery• Optimized if domestic/process HW loads present• Must do TCTs, hourly building & GHX modeling• Requires Const. Mgmt: Submit. Reviews, grout test,

ASTM pressure testing, 4+FPS flush/purge, etc.

Application Considerations at Federal Facilities

Energy Exchange: Federal Sustainability for the Next Decade

Chuck Hammock, PE, LEED BD+C, CGD -Andrews, Hammock & Powell, Inc.-Consulting Engineers-Macon, GA-478-405-8301, Ext. 6362chammock@ahpengr.com

Questions and Answers!