Session 6: HVAC Technologies -BTES

Borehole Thermal Energy Storage (BTES) Chuck Hammock, PE, LEED AP BD+C, CGD Andrews, Hammock & Powell-Consulting Engineers 10 August 2016, 1400-1530 Rhode Island Convention Center • Providence, Rhode Island

Presentation Outline and Objectives

• Provide a brief overview of multiple forms of Underground Thermal Energy Storage (UTES & TES) e.g. Borehole Thermal Energy Storage (BTES) or Aquifer Thermal Energy Storage (ATES) • Advise what applications are UTES appropriate • Learn what differentiates UTES/BTES from “normal” GroundLoop Heat Exchangers (GHX) and Geothermal Heat Pump (GHP) “architectures” • Present the initial results of ESTCP’s EW-201135 • Overwhelm you with acronyms 2

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Brief Overview of TES/UTES • Thermal Energy Storage (TES) can be: – Above ground, below ground or both – Sensible only, latent only or both – Diurnal, Seasonal or Both

• In the Underground form, UTES is: – Normally ATES or BTES …but can be.. – Hybrid UTES: Combine above ground and underground Storage (Drakes Landing) – Pit Storage:

45 Contributors, One American

(200,000 M3, 85°C, Denmark) for heat or

a cold version called Seasonal Snow Storage (SSS)

SSS- Sundvall Sweden Storage

– Abandoned Mines or Flooded natural caverns (CTES) – Energy Piles (basically a multi-purpose structural pile/BTES system) 3

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ATES and Hybrid BTES

• ATES (similar to “American” open loop Geo systems but better). In use around the world, but currently just one “cold-only” ATES system in the US

ESTCP ATES-Ft. Benning, GA

• Hybrid BTES (warm storage) at Drakes Landing near Calgary, Canada Drakes Landing, Canada 4

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BTES for non-GHP applications

Solar Thermal Application-Drakes Landing, Canada “Hybrid” with above ground thermal storage & BTES

Combined Heat & Power (CHP) plant with BTES 5

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BTES Concepts • Technology is well suited to “Geothermal Heat Pumps” (GHP) but is equally appropriate with Solar Thermal (Drakes Landing), any waste heat (e.g. CHP, Industrial processes) or “waste cool” situation • Differentiated from “American” closed loop GHX architectures due to engineered thermal storage &: – Reversing valves allowing water to flow in or out of core – Boreholes piped in series (versus all in parallel) that allow varying Delta T across each borehole – Concentric (solid & hollow) cylindrical thermal zones – Actively managed heat/cold “hybrid” component 6

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Germany’s VDI-4640 Underground Thermal Energy Storage (UTES) Guidelines

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When to consider BTES? • Above 50 Tons? There probably is a min. size threshold before BTES should be considered, due to reversing valve, etc. cost, but theoretically, three thermal zones can be created with as few as 30 boreholes, therefore 30-60 tons (typ.) • Smallest/Largest by AH&P so far: 60/336 boreholes • If smaller GHX footprint needed (due to closer borehole spacing since engineered for thermal storage not just heat extraction/dissipation). Ideally square/circular land availability, but the “cylinder” can be oval (VA’s BTES-5) • Anytime you are considering GHPs and/or have a good source of “free” heat or cold (CHPs, Solar, etc.) • Water conservation desired while retaining high EERs • All Fed. Properties. BTES (unlike ATES) is a 50 state technology 8

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BTES-1 (ESTCP/NAVFAC), Marine Base (MCLB) Albany, Georgia BTES

Reversing Valves & Adiabatic Dry-Cooler

Circular HDPE Headers/Radial Sub-Mains at BTES-1 9

Heat-Recovery Water-to-Water GHP Energy Exchange: Federal Sustainability for the Next Decade

BTES-2/3/4 (NAVFAC); BTES-5 (VA) 66 Ton BTES

BTES-2 MCLB Albany GA

183 Ton BTES

BTES-3 MCLB Albany GA

56 Ton BTES

BTES-4 MCLB Albany GA “Oval” BTES-5 BTES-5 VA Perry Point, MD 10

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BTES-1 has a 2.6 km fiber optic based Distributed Temperature Sensing (DTS) system with 1300 underground temperature points

Rack Mounted DTS Computer

DTS Distance/Sampling Temperature Accuracy Table

4” dia./225’ long DTS Well (Typ. for 9)

BTES-1 Temperature Readings Energy Exchange: Federal Sustainability for the Next Decade

BTES-1 with true Energy-Water-Nexus control Combining BTES with Adiabatic Dry-Coolers provides a virtual Energy-Water-Nexus “slider bar” to reduce/eliminate the copious water consumption generally associated with traditional cooling towers while still exceeding water-cooled EERs Moderate Water/ Lowest KWH-KWD

No Water/ Moderate KWH-KWD

Adiabatic Dry-Cooler 12

Application

Heat Reject. COP

Air-Cooled-DX

100

BTES Max

1616

BTES Winter

200-1600

BTES Yr. Ave

200-400

Annual Water Reduction

Virtual Energy-Water BTES 80-100% Nexus Slider-Bar Close-up of hydrophilic evaporative cooling pad/gutter at adiabatic dry-cooler coil inlet Energy Exchange: Federal Sustainability for the Next Decade

Temperature Plots of BTES Entering and Leaving Water & Charging/Discharging Modes • In the next few slides, the blue line represents: – The water at the perimeter of the BTES – If the system is being “charged with cold”, this is the temperature leaving the outer boreholes. If the system is “discharging its cold”, this represents the warmer water entering at the outer borehole

• Conversely, the green line represents the water at the core of the BTES that is entering the core during “charging” and leaving the core during “discharging” Red shading represents “cold discharging” or heat going into the BTES (typical)

Sample plot of water temperatures during cold discharging-only mode in early fall Energy Exchange: Federal Sustainability for the Next Decade

Temperature Plots of BTES Entering and Leaving Water & Charging/Discharging Modes (continued)

Sample plot of water temperatures during DIURNAL STORAGE times in late fall (“cold-discharging” during the day & “cold-charging” at night) Blue shading represents “charging”, (cold storage) or heat being removed from the BTES (typical)

Sample plot of water temperatures during continuous (24 hr/day) “cold charging” SEASONAL STORAGE mode in winter Energy Exchange: Federal Sustainability for the Next Decade

Temperature Plots of Inner, Middle and Outer Borehole Delta T’s

Sample plot of water temperatures differentials across three boreholes in series charging the BTES in late fall with “cold”. The teal line is the delta T across the inner borehole, the green the middle borehole and the blue the outer borehole. The most heat transfer is occurring exactly where it is needed ….at the core of the BTES Energy Exchange: Federal Sustainability for the Next Decade

ESTCP’s EW-201135 (BTES-1) 11 month results MCLB Albany ( as of 30 June 2016)

• KBTUs/Ft2 are down 48.1% even when this highly coolingdominate building experienced a 14% increase in Cool. Deg. Days (CDD) and room temps kept 1°F colder. Combined annual elec., gas, water & maint. savings are $169k/year • On-site gas consumption & emissions eliminated. • So far, evaporative water consumption is zero…a reduction of 5.1M gallons/yr., though we may chose to consume up to 1M gallons (20% of baseline per the ESTCP Demo Plan) to lower KWH/KWD further • Current payback on $1.8M BTES cost is 10.7 years • “Technology Transfer”: A+ with 4 more BTES system currently under design and scheduled to bid in late 2016 16

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Session 6: HVAC Technologies -BTES

Questions and Answers Chuck Hammock, PE, LEED AP BD+C, CGD Andrews, Hammock & Powell, Inc. Consulting Engineers 250 Charter Lane Macon, GA 31210 [email protected] 478-405-8301, Ext. 6362 Skype: chuck.hammock.ahp 17

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