Seasonal Thermal Energy Storage Applications for District Energy Systems

Transcription

1 Seasonal Thermal Energy Storage Applications for District Energy Systems Presented to by Mark A. Worthington Underground Energy, LLC 2010 Underground Energy, LLC

2 Outline Seasonal Thermal Energy Storage The UTES Concept Borehole Thermal Energy Storage (BTES) Aquifer Thermal Energy Storage (ATES)»The Dutch Experience Traditional Uses of Geothermal Temperature Stability District Energy System UTES Applications Opportunities for Seasonal Storage ATES-Based District Energy Systems in Europe Project Components and Phasing Permitting Economics Summary & Conclusions

3 Seasonal Thermal Energy Storage Ice house in Boxborough, MA Ice storage in Iran Concept: Generate cold or hot water during cold or hot weather Inject the water into a borehole array (BTES) or an aquifer (ATES) for seasonal thermal energy storage Recover stored hot or cold water and use it to heat or cool buildings

4 The Preferred Energy Storage Medium?

5 Borehole Thermal Energy Storage (BTES) Summer Winter Closed loop Radial array configuration may use multiple arrays Seasonal reversal of flow within the loop Small footprint on storage site

6 Seasonal thermal energy storage enabled by: High heat capacity of (ground)water Dynamics of fluid flow in porous media Low ΔT, low advection Hydraulic modeling and management of aquifer Open loop with separate warm and cold stores Seasonal reversal of warm and cold withdrawal / injection Hydraulically balanced Thermally balanced Aquifer Thermal Energy Storage (ATES) Summer Winter

7 ATES for Cooling Chilled Water Loop ΔT ~ 12 F Ambient Groundwater 50 F Warm Store ~53 F (EWT) Cold Store ~ 41 F (IWT)

8 ATES Technical Requirements A suitable temperate climate with seasonally variable thermal loads An Aquifer! High transmissivity (T = Kb) Reasonable depth / thickness Reasonable hydraulic gradient (dh/dx 10-3 ) Acceptable water quality Space for cold and warm store areas Favorable regulatory climate Practitioner team with appropriate experience and skill set

9 No. ATES Projects ATES Growth in The Netherlands 900 ATES Projects in The Netherlands Typical project thermal capacity: 1 MW (285 ton, 3.4 MBTU) (400 gpm through HEX, 18 F ΔT) Source: National Bureau of Statistics

10 Isn t this just geothermal? No. The difference is energy storage High-Temp Geothermal = Energy Production Low-Temp Geothermal = Energy Conservation GeoExchange = Conventional GSHP Applications UTES = Underground Thermal Energy Storage How does this apply to District Energy systems? Underground thermal energy storage is an enabling technology for district energy providers and consumers!

11 USA Geothermal Resources High-Temperature Geothermal Geothermal Gradient Map Low-Temperature Geothermal Shallow Groundwater Temperatures

12 Components of a Conventional Ground-Source Heat Pump System Interior HVAC Heat Pump Ground Loop Ideally, the ground exchange loop increases the efficiency of the heat pump

13 Low-Temp Geothermal = Temperature Stability?

14 US Geothermal Design Practice Adequate separation is required to prevent short and long term heat storage effects in loop fields. This is especially true when with clay and impermeable rocks are present. Water movement will be minimal and heat will be significant in typical commercial /institutional buildings if the bores are located less than 20 feet apart. GchpCalc V 4 Instruction Manual, p. 11

15 Ground Heat Exchanger Design Practice USA The GHX is used as a radiator Excess heat or cold is simply conducted and advected away thermal balance is NOT automatically ensured Europe GHX is used as a thermal battery Excess heat or cold stored seasonally, thermal balance easily achieved through a combination of design and operation parameters

16 UTES Opportunities for District Energy Applications Store at production site Store excess production Recapture thermal production losses Store at consumer site Storage can be managed by the consumer or the producer with the expense comes the benefit Excellent opportunity to transition a large consumer into District Energy CHP Production Recovered waste heat to UTES CHP Consumption Production Losses Energy Input Steam Delivery Chilled Water Delivery Excess Production stored in UTES Excess Delivery stored in UTES

17 ATES for District Energy Systems ATES scales well, therefore large thermal energy users will realize greatest cost and efficiency benefits Seasonal storage aspect of ATES enables base and peak thermal loads to be met more efficiently, and ATES application is flexible to accommodate numerous configuration options Often used for cooling only (no heat pumps) Well suited for campus district energy systems with room for separate cold and warm store areas Innovative and efficient means of meeting sustainability and emission reduction targets

18 ATES Based District Heating & Cooling Systems in The Netherlands Wavin industrial park Hardenberg (5.0 MW) The Resident office park - The Hague (3.0 MW) Schalkwijk housing project Haarlem (1.5 MW) Chassee mixed development Breda (4.0 MW) Eastern Trade Wharf mixed developm. Amsterdam (4.0 MW) University Campus Eindhoven (20 MW) Spoorwijk housing project I The Hague (1.2 MW) University Campus Utrecht (3.5 MW) Mahler 4 mixed development Amsterdam (6.5 MW) Philips High-Tech Campus Eindhoven (10 MW) City centre mixed development Arnhem (construction stage, 3.8 MW) Shell Campus Amsterdam (construction stage, 15 MW ) University hospital Nijmegen (construction stage, 15 MW) Spoorwijk housing project II The Hague (0.9 MW) Overheem housing project Zoetermeer (1.3 MW) Eastern Dock Island mixed dev. Amsterdam (constr. stage, 7.0 MW)

19 Mixed Development Amsterdam (NL) Cooling capacity: 4,000 kw Operational since: 2001

20 Major data ATES system OHK project Aquifer depth m No. of wells 2 x 2 Heating capacity Heat delivered Cooling capacity Cold delivered Max. flow rate kw MWh/y kw MWh/y 500 m³/h Courtesy of

21 UTES Project Components Design & Permitting District Energy Implementation Commissioning, O&M Construction A well-implemented UTES system can add or extract heat at nearly any point in a thermal distribution system, and can be used in conjunction with heat pumps, air handling units, heat exchangers, chillers, solar collectors, or with any other innovative approach to HVAC delivery or energy reclamation.

22 ATES Project Phasing Phase I Desktop Feasibility Study Non-intrusive, look for fatal flaws Preliminary cost estimate Phase II Pre-Design Work Hydrogeologic characterization Thermal and hydraulic modeling of well field Detail Design Well and equipment specifications Integration with MEP systems Detailed cost estimate Construction Commissioning Operation, Maintenance & Monitoring

23 ATES Permitting Regulations Underground Injection Control (40 CFR Part 144)»Temperature is only regulated parameter»registration, not a permit Water Management Act»Expect waiver for nonconsumptive use Wetlands Protection Act (?) State superfund if contamination is present (?) Impacts and Recommended Mitigation: Thermal use modest ΔT Hydrologic (wetlands) site warm store closest to wetlands Displacement of Existing Groundwater Contaminant Plumes site cold and warm wells on same streamline

24 ATES System Economics Expected Project Economics $1M to $2M typical expected project value Estimate 5-7 year simple payback Financial incentives (commercial systems)» 10% geothermal property tax credit» Accelerated depreciation (5-year MACR) Energy Savings with ATES System Cooling:» 60-80% saving on electricity consumption for chilling» 80-90% reduction of electrical peak for chilling Heating:» 20-30% saving on primary energy consumption for heating

25 Geothermal Technology Summary

26 Conclusions Seasonal thermal energy storage technology can significantly increase the efficiency of geothermal heating and cooling systems. UTES can be an enabling technology for district energy providers and consumers. ATES is the seasonal thermal energy storage application best suited to district energy systems because it becomes more cost efficient with the scale of the system. ATES is an innovative green technology that can significantly reduce operating and life-cycle costs, save energy, reduce CO 2 emissions, and reduce dependency on fossil fuels, all with minimal environmental impact. District energy systems that overlie a transmissive aquifer should consider ATES when planning expansion of a chilled water loop. We anticipate that ATES projects in the US will be economically attractive and that adaptation of the technology will follow a similar trend as has been observed in Northern Europe.

27 Thank You!