A presentation by Iain Howley MD of Ground Source Consult Ltd to the member of The Chartered Institute of Builders (CIOB) on 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/

8. Getting Started….

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
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Fluidtemperature[ºC]
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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
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Fluidtemperature[ºC]
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35
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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

35. Understanding Thermal Interference

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
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NetBuildingLoad(kW)
Time (Hour)
Design Building Loads (kW)
Cooling Load (kW)
Heating Load (kW)

39. Modelling ‘Fine-tuned with a Thorough Site Investigation
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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
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12
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Temperature(°C)
Time (days)
Recharge Borehole
Abstraction Borehole
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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
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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
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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