Geothermal Systems: Harnessing Earth s Energy

Transcription

1 Geothermal Systems: Harnessing Earth s Energy 4 November 2014 Ground Source Heating and Cooling What is It? How does it Work? What makes it Unique? Why all systems are not Equal? 1

2 Building Owner Expectations Simplicity Control of utility bills Low maintenance Greater comfort Efficiency Environmentally Green What Comprises a Ground Source Heating and Cooling System? Bore field Fluid Circulating Pumps Water source heat pump The rest is a standard heating cooling system 2

3 Why are Ground Source Systems Efficient? Energy recycling Ground source systems are Energy Recycling Systems In the summer heat is rejected to the ground In the winter heat is absorbed from the ground At peak conditions the ground temperature is warmer than the air temp in the winter and cooler than the air temp in the summer Heat recovery The connecting energy loop in the building allows for energy recovery Where one space is in heating another is in cooling, this allows spaces to Share Energy Low supporting system power requirements Fluid circulation energy is very low with well designed systems Recycled Energy Ground Source Bore Field Thermal Conductivity 3

4 Glencoe Central School Heat Rejection vs. Building Load How Heat Pumps Work 1 kw electricity 4-5 kw Heat Delivered 3-4 kw of Energy moved from the Earth 4

5 A Bore Field Is a combination of ground loops tied together to make a heat exchanger HDPE SDR 11 UNI LOOP 18 MIN Thermally enhanced grout 5

6 10/23/2014 Before After 6

7 Mechanical System Selection Provide an economic evaluation of prospective systems Look at energy efficiency Look at system maintenance/complexity First Cost and Life Cycle Cost of the potential solutions Analysis tool compares 7 different systems with identical loads and appropriate system inputs. 7

8 Projected operating cost 8

9 Mechanical System Considerations Ground Source No exposed equipment Simple system Easy to maintain Energy efficient Lowest life cycle cost Tax / depreciation advantages Utility support considerations No gas required Traditional Systems VAV and Single Zone Exposed condensing units on ground or roof Digital controls required for VAV Electric reheat or hydronic heating and cooling Maintenance is done by a more qualified individual Higher life cycle cost Higher operating cost Gas may be required 10/23/2014Ground Source Energy Expectations How do facilities compare? What kind of results can be expected? How consistent are the results? 9

10 Glencoe Central School Misner Auditorium Glencoe Central School Classroom Wing

11 Glencoe Central School Classroom Wing Summary of Mechanical Equipment Assessment Central School Mechanical Equipment Surveyed and Documented History of Performance and Repairs Reviewed with District Staff Equipment Categorized by Type, Life Expectancy & Age Color-Coded Floor Plans Equipment Type and Age Chart 11

12 Central School First Floor Plan Glencoe Central School Annual energy usage Kbtu/sq ft/yr Projected usage Under 24 Kbtu/sq ft/yr 12

13 Payback of Increased First Cost for Geothermal System Full Building System Energy Use Payback based Payback based on Energy Energy & Operation Current System: 88 kbtu/sf/yr Pipe System: 43.7 kbtu/sf/yr none none Geothermal System: 22.5 kbtu/sf/yr 6.6 years 3.3 years Advantages of Geothermal System Simultaneous Heating / Cooling to Building Zones Improved Thermal Comfort Improved Educational Environment Improved Energy Efficiency of System As shown on Payback Summary Improved Operational / Maintenance of System Improved Life Span of Equipment 13

14 Central School First Floor Plan Heat Pumps in a Closet 14

15 Vertical Unit Ventilator Reduced Equipment in Mechanical Room 15

16 Schedule Considerations for Implementation Time Frame for Well Field Installation Impact on Availability of Play Fields Time Frame for Building Work Single Summer Project? Two-Summer Project? When should work be authorized for Summer construction? Lead Time for Design Optimum Time for Contract Award Lead Time for Award Phasing of Well Field 16

17 Glencoe SD 35 Project Summary School dating back to the 1920 s enters 21st Century with a bright future ahead. Aging Mechanical Systems Replaced Building-Wide Geothermal System Chosen vs. Conventional Systems Simultaneous Heating / Cooling to Building Zones Improved Thermal Comfort Improved Educational Environment Improved Energy Efficiency of System Improved Operational / Maintenance of System Improved Life Span of Equipment Very Cost-Effective compared to Convention System Replacement 17

18 Achieving High Performance Not all ground source systems are created equally. Experience matters. Understanding how building energy is moved throughout the system Ground loop design Building system optimization Understanding project budget Selecting a Geothermal Design Professional Your system should not be the First Engineer should characterize the load Cooling Dominated, Heating Dominated or Balanced Knows the limitations presented by your Site Drilling conditions Thermal Conductivity Design Implementation Ability to compare multiple systems to best fit the application Distributed heat pumps VAV system Variable Refrigerant flow ENGINEERING 18

19 Conclusions Geothermal solutions offer low first cost solutions to energy efficiency. Using a system where energy is recycled will result in substantial primary source energy savings. It does not take sophisticated control systems to provide superior comfort and energy efficiency. Control of lighting and plug loads represents a MAJOR area for system load rightsizing. Ventilation presents an opportunity for space humidity control if properly managed. Apply sound thermodynamics and system design principals before increasing control complexity. An improperly designed system will never be fixed with controls. Geothermal Systems: Harnessing Earth s Energy Colin Marshall, Principal, GreenAssociates, Inc. cmarsh@greenassociates.com Kirk Mescher, Principal, CM Engineering kirk@cmeng.com Jeff Chamberlain, Principal, Engineering Group, LLC jeff@2010engineering.com 19

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