![Feasibility Investigation and Preliminary Design
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![Example Two: poor design on our office – when will this system fail?
Using the original “rule of thumb” example: 60 boreholes, 5 m spacing, 100 m deep arranged in
a square
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After 5 years, it
would still just
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But after 7 years
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to total failure.](https://image.slidesharecdn.com/ciobrev1-19-3-14-140410071515-phpapp01/85/Ground-Source-Energy-System-Design-28-320.jpg)
Ground Source Energy - System Design
- 1. GROUND SOURCE ENERGY SYSTEM DESIGN FOR Chartered Institute of Building Iain Howley ( Director ) Ground Source Consult Ltd 19th March 2014
- 2. Presentation Agenda Introduction to GSC Ltd Ground Source Systems – The Drivers Brief Introduction to Ground Coupling Techniques Closed Loop: • The Differing techniques & what suits what • Getting it wrong & the consequences Open Loop: • How it works – variations in design • Design risks – The need for a skilled approach • Thermal modelling – How & Why Case Studies: Open and Closed Loop
- 3. • Directors are from a drilling background and therefore have a very strong understanding of designing & installing ground heat exchangers • Professional team headed by an IGSHPA Accredited GeoExchange Designer, Own Hydrogeologist / Groundwater & Thermal Modeller and own Drilling & Pipe Fusion Engineers etc • Specialise in the design and consultancy of commercial open and closed loop systems – consider Design & Build roles for certain clients • Completed schemes to date ranging from 5 kW to 2,200 kW Ground Source Consult Ltd
- 4. • Originally, Part L Planning & The Merton Rule • The growing desire to be green – Corporate Responsibility and desire to build, own or operate BREEAM high standard facilities • New legislation regarding code for sustainable homes leading to increasingly ultra-efficient housing development • The Renewable Heat Incentive ( RHI ) – 9.4p/kWh paid for upto 1500 full load hours of heating – Designed to accelerate ROI terms • As de-carbonisation of the grid is introduced, ground source systems become increasingly desirable Ground Source Systems – The Drivers
- 5. • Pre-design / planning advice • Full feasibility investigation • Transparent design by Certified GeoExchange Designer (CGD®) • Demonstration of sustainability, efficiency and CO2 savings • Full design responsibility • Installation management ( supervision ) by experienced engineers • Thermal groundwater modelling for open loop schemes • All Environment Agency Regulatory Engagement • Design & Build through Uponor Ltd GSC - Services
- 6. Who We Work With..
- 7. Ground Source Heat Pumps - How It Works http://www.kensaengineering.com/
- 9. When Should Ground Source Design be Considered? But please not here
- 10. Feasibility Investigation and Preliminary Design Fluid temperaturegfedcb Peak cool loadgfedcb Peak heat loadgfedcb Year 50 JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NOV DEC Fluidtemperature[ºC] 30 29 28 27 26 25 24 23 22 21 20
- 11. HORIZONTAL CLOSED LOOP – OFTEN KNOWN AS ‘SLINKY’S Used typically for domestic sites or can be used to serve larger projects such as schools where large area’s of land are available. A 50m slinky row typically services around 3-4kW of heating load
- 12. FOUNDATION PILES Piles only offer limited heat exchange capacity because they are usually shallow & in London generally drilled into low TC clay In our opinion, not enough research has been initiated into how heating and cooling via piles affects the pile itself Free Drilling ? Cheap as Chips ? No its not ! There are wider reaching implications for a piled system verses other ground coupled techniques such as impact on build programme
- 13. POND, LAKE, RIVER or OCEAN CLOSED LOOP Coiled pipe or SS plates are submerged in the water and using an existing lake or river can be a very cost effective heat exchanger system Any development considering a water feature should perhaps keep in mind the potential to use it as a source for heat exchange Used anywhere where a body of water is available. Can service both small and large systems depending on size of lake and through-flow of water
- 14. VERTICAL CLOSED LOOP ( BOREHOLES ) Used on small or large schemes
- 15. Open Loop System
- 16. Closed Loop Systems – The Rights & Wrongs
- 17. If you need more energy, you just need a bigger pipe or a larger cable The Ground Source Energy Concept – Why is this important?
- 18. Why is ground source heat different from traditional resources? • The ground is not an infinite resource • You are replacing or reducing dependency on these with a Ground Heat Exchanger
- 19. Why is this not an infinite resource? Imagine the ground heat exchanger as a Battery on Trickle Charge The Ground Source Energy Concept
- 20. Can the battery go flat? When we hook a building up to a ground heat exchanger, if the “battery” isn’t man enough for the job, the battery could go flat. To ensure this “battery” is sized correctly, the ground loop needs be properly designed by somebody who knows what they are doing.
- 21. What if you get it wrong? You don’t want to over- stress the ground. The Ground Source Energy Concept
- 22. Who’s Designing your system ? Certified GeoExchange Designer ?? Or Somebody who has downloaded the software ?
- 23. The Ground Source “Lottery” – Poor Approach • 50 watts per metre gives a 7,000 m loop field; • Divide 7,000 m by 100 (a nice round number) to give 70 boreholes; • Arrange the boreholes 5 m apart because it says so on the internet; • Arrange the boreholes in a square because it looks tidy on the drawings; Office Building: • 350 kW peak Cooling • 150 kW peak Heating
- 24. • Assess actual peak loads and annual loads; • Investigate the feasibility and “drillability” in outline design work; • Undertake thermal analysis with in-situ thermal testing; • Determine a detailed load profile and specify heat pump; • Develop detailed design and establish system optimisation; • Produce a transparent and detailed specification; and • Experienced drilling engineers supervise the installation throughout. Ground Source Design – The Right Approach ! To avoid playing the ground source lottery altogether, you need the following to be building and site specific: Office Building: • 350 kW peak Cooling • 150 kW peak Heating
- 25. Getting it wrong !! Drilling the borefield to the previous spec would have worked. But it would have needlessly cost an extra £175k. CGD reduced borefield by 3,000m !! Over 10,000m of drilling in this proposal !!
- 26. 150 kW peak heating and 80 MWh annually 350 kW peak cooling and 200 MWh annually Our office Borehole Depth Borehole Spacing Boreholes Required Borehole Capacity (per borehole) Effective Design 100 m 8 m 60 5.8 kW Poor Design 100 m 5 m 9260 3.8 kW
- 27. 150 kW peak heating and 80 MWh annually 350 kW peak cooling and 350 MWh annually Our office Borehole Depth Borehole Spacing Boreholes Required Borehole Capacity (per borehole) Effective Design 100 m 8 m 60 5.8 kW Poor Design 100 m 5 m 92 3.8 kW Poor Design 100 m 5 m 152 2.3 kW Effective Design 100 m 12 m 92 3.8 kW Poor borehole spacing results in more boreholes being required due to interference effects. At £3,000 - £4,000 per borehole, this increases the costs significantly. 350 kW peak cooling and 200 MWh annually Greater Load Imbalance: increase annual cooling load to 350 MWh
- 28. Example Two: poor design on our office – when will this system fail? Using the original “rule of thumb” example: 60 boreholes, 5 m spacing, 100 m deep arranged in a square Fluid temperaturegfedcb Peak cool loadgfedcb Peak heat loadgfedcb Year 50 JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NOV DEC Fluidtemperature[ºC] 48 46 44 42 40 38 36 34 Peak mingfedcb Peak maxgfedcb Base mingfedcb Base maxgfedcb Year 5045403530252015105 Annualmin-maxfluidtemp.[ºC] 45 40 35 30 25 20 15 10 After 5 years, it would still just about be working at 35°C but efficiency would be unacceptably low But after 7 years the system is close to total failure.
- 29. Correct Design: our typical single home would require a 53.4 m deep borehole. Social housing Interference effects: However, with 6 terraces in a row we have 6 m spacing between boreholes (one in each front garden). Interference effects increases the required borehole length to 66.2 m per household if correctly designed. Poor design, resulting in reduced spacing between boreholes will increase the interference effect. Furthermore, without thermally enhanced grout and having used incorrect pipe diameter the required effective length increases again to 85.3 m.
- 30. Open Loop System Subject to Lengthy & Complex Environment Agency Regulatory Process
- 31. Borehole Yield Likely ? Sufficient and sustainable groundwater flow (and thermal store) in the aquifer?
- 32. Types of Open Loop System Unidirectional Reversible cooling period heating period
- 33. Borehole Construction – Critical Process
- 34. Borehole Construction: How important is experience in this? Down-hole view from 83.0 mBGL Down-hole view from 84.1 mBGL
- 36. Other Issues and Licensing Environment Agency: • Protect existing users; • Abstraction licence; and Risk Assessment • Discharge consent. Other issues: • Biofouling; and • Sand ingress. From initial feasibility report to handover of working system typically takes at least 15 months
- 37. System Design and Risk Assessment using FEFLOW • Finite-element simulation software; • 2D and 3D Simulations; • Dynamic modelling of groundwater flow and heat transport Used to simulate the groundwater flow regime and heat transport resulting from the operation of open loop ground source heat pump systems.
- 38. Building & Calibrating the Model for Your Open Loop System 0 100 200 300 400 500 600 700 800 900 1000 0 200 400 600 800 1,000 1,200 1,400 1,600 1,800 2,000 2,200 2,400 2,600 2,800 3,000 3,200 3,400 3,600 3,800 4,000 4,200 4,400 4,600 4,800 5,000 5,200 5,400 5,600 5,800 6,000 6,200 6,400 6,600 6,800 7,000 7,200 7,400 7,600 7,800 8,000 8,200 8,400 8,600 NetBuildingLoad(kW) Time (Hour) Design Building Loads (kW) Cooling Load (kW) Heating Load (kW)
- 39. Modelling ‘Fine-tuned with a Thorough Site Investigation 29 30 31 32 33 34 35 36 37 38 39 5 10 15 20 25 30 35 40 GroundwaterLevel(mOD) Time (days) BH1 - Modelled Head BH1 - Observed Head BH2 - Modelled Head BH2 - Observed Head
- 40. Site Investigation and Conceptual Model Numerical Model Open Loop Design
- 41. Risk Assessment Modelling • Derogation of the environment or other protected rights:
- 42. Open Loop Design Modelling One: • How Efficiency/Sustainability is affected by horizontal separation of the boreholes: Large Borehole Separation Small Borehole Separation 10 12 14 16 18 20 22 24 0 100 200 300 400 500 600 700 800 Temperature(°C) Time (days) Recharge Borehole Abstraction Borehole 10 12 14 16 18 20 22 24 0 100 200 300 400 500 600 700 800 Temperature(°C) Time (days) Recharge Borehole Abstraction Borehole
- 43. Investigate How Efficiency and Sustainability are affected by plant (e.g. dry air cooler): 8 9 10 11 12 13 14 0 50 100 150 200 250 300 350 400 GroundwaterTemperature(°C) Model Time (Day) Abstraction BH1 Recharge BH2 Abstraction BH3 Recharge BH4 Open Loop Design Modelling Two:
- 44. Open Loop Design Modelling Three: Groundwater Gradient: Maximum Mean Minimum 11.5 12.0 12.5 13.0 13.5 14.0 14.5 15.0 15.5 0 200 400 600 800 1000 1200 GroundwaterTemperature(°C) Model Time (Day) Minmum Gradient Recharge BH Minmum Gradient Abstraction BH Mean Gradient Recharge BH Mean Gradient Abstraction BH Maximum Gradient Recharge BH Maximum Gradient Abstraction BH
- 45. Modelled Scenarios: Flow Mechanism – Long Term FM: Fracture model EPM: Equivalent Porous Medium model 0 1,000 2,000 3,000 4,000 5,000 6,000 7,000 GroundwaterTemperature(°C) Model Time (Day) EPM Abstraction BH EPM Recharge BH FM Abstraction BH FM Recharge BH 12.5 13.5 14.5 11.5 10.5 11.0 12.0 13.0 14.0 15.0 Abstraction temperature is critical for direct distribution chilled beam systems
- 46. A FEW CASE STUDIES ……..
- 47. CASE STUDY 1: LARGE CLOSED LOOP SYSTEM LMB CAMBRIDGE – Background to New Build The birthplaces of molecular biology, notably the sequencing of DNA. LMB has attracted 9 Nobel prizes shared amongst 13 LMB scientists. Designed by RMJM architects Main contractor BAM Construction Start date: Summer 2008 Main contract: April 2009 Completion date: due in 2012 Whole project value of £200 million The total area will be 27,000m2 of fully air-conditioned space. All heavy plant servicing the building is housed in the four stainless steel- clad towers linked to the building. This removes weight and sources of vibration from the laboratory itself, allowing a more lightweight construction.
- 48. CASE STUDY 1: LARGE CLOSED LOOP SYSTEM LMB CAMBRIDGE – GSHP Details • 1,600 Kw Peak Cooling • 170 Boreholes • 152 Metres Deep • Approximate borefield size 150 m x 45 m
- 49. CASE STUDY 2: LARGE OPEN LOOP RIVER ISLAND Headquarters – Background to Refurbishment Driver: Corporate Social Responsibility Policy for the Environment M&E Engineers: CJ Design Partnership Limited Office and design studio Refurbishment with a total project value of £2 million Start date: May 2007 Completion date: December 2009
- 50. CASE STUDY 2: LARGE OPEN LOOP RIVER ISLAND Headquarters – GSHP Details 1,400 Kw Peak Cooling Serviced by: 6 Boreholes • 3 Abstraction • 3 Recharge Each 130 Metres Deep Collectively abstracting and continually recharging 60 l/s to and from the Chalk Aquifer approximately 70 m below ground level
- 51. Thanks for listening Iain Howley Design, Installation Management and Consultancy Services for Commercial Ground Source Heating & Cooling Projects Unit 5, Hope & Aldridge Business Park · Weddington Road Nuneaton · Warwickshire · CV10 0HF Tel: 024 76 629762 l Email: info@gscltd.co.uk l Web: www.gscltd.co.uk