THE GROUND SOURCE HEAT PUMP ASSOCIATION The National Energy Centre - - PDF document

THE GROUND SOURCE HEAT PUMP ASSOCIATION

The National Energy Centre • Davy Avenue • Knowlhill • Milton Keynes • MK5 8NG Tel: 01908 354545 • e-mail: info@gshp.org.uk • Fax: 01908 665577

Website: www.gshp.org.uk

Registered in England No. 1372316 VAT No. 354 3365 56

09:00 Welcome Address

Duncan Nicholson

09:05 Desk study stage and site investigation and response testing

Chair: Duncan Nicholson Recorder: Brian Stringer

Regulation of GSHP systems Jenny Thomas

In common with other forms of renewable energy, the Environment Agency wishes to encourage the sustainable use of GSHP systems. We are therefore looking to simplify regulation and require the minimum information from applicants. To achieve this, we are looking to publish good practice guidance. We do not regulate closed loop systems. Open loop systems require a groundwater investigation consent, followed by an abstraction licence, and a discharge consent. There is currently limited information available on the temperature of aquifers and in practice how they respond to changes. This, together with simple tools to enable rapid assessment of applications, covers our main research needs.

Borehole Heat Exchanger Model Development Miaomiao He

Common approaches to the simulation of Borehole Heat Exchangers (BHEs) assume heat transfer in circulating fluid and grout to be in a quasi steady state and ignore fluctuations in fluid temperature due to transport of the fluid through the loop. However, the dynamic responses of circulating fluid and BHEs have important implications for systems design under some

• circumstances. In this research project a dynamic three dimensional numerical model has been

developed by applying the finite volume method to simulate the fluid transport and transient conduction in and around the BHE. The model is being used to study short time scale dynamic behaviour, the effect on peak performance, control system interaction and develop improved simplified models.

Mitigation potential of horizontal ground coupled heat pumps for current and future climatic conditions: UK environmental modelling and experimental studies Anne Verhoef

A NERC research project started in May 2009 to calculate the mitigation potential of horizontal

• GCHPs. The team consists of soil physicists, climate modellers, building and energy

technologists, groundwater modellers and GCHP installers, from Reading and Nottingham University, BGS, CEH-Wallingford and EarthEnergy Ltd. The combined effect of environment dynamics and GCHP technical properties on long-term GCHP performance will be assessed using simulation modelling, by combining the UK Met Office land surface model, which provides key variables such as land surface temperature and soil moisture content, with equations describing the interaction between GCHP heat exchangers and the surrounding soil

09:55 Open Systems

Chair: David Whitaker Recorder: Huw Williams

Development of Finite Element thermal groundwater models Huw Williams

The presentation will cover the thermal groundwater finite element modelling (in FEFLOW) undertaken to date by LoopMaster (Europe) to investigate the suitability of each system in the dual porosity Chalk Aquifer of the London Basin. A brief discussion of modelling techniques will be given, including a review of the initial results which have lead to LoopMaster offering support for a post graduate Thesis to further develop these preliminary findings.

Sustainability assessments of GSHP Systems Martin Preene

The Presentation will briefly present work Golder Associates has recently completed in Ontaria, Canada reviewing best practice on the assessment and subsequent regulation of environmental impacts from GSHP systems

10:35 Closed loop borehole and horizontal systems

Chair: Robin Curtis Recorder: Nic Wincott

Spiral Probes as alternative to Horizontal Collector Ralf Winterling

Either probes or horizontal collector are the standard application for ground source solutions in the residential market. Probes require on average a 100 m bore hole, which could be problematic in certain ground conditions or restricted by planning, e.g. in areas of ground water

• usage. Whereas horizontal collectors require a sizable ground space which is most often not

available on the average new build plot size. To address these topics a spiral collector has been developed, requiring only a 5 m deep bore hole and significantly less ground space. The presentation will provide an overview of the spiral probe development, the design parameter and installation technique as well as monitored performance figures of a test field installation

Building Simulation Nick Kelly

The Energy Systems Research Unit (ESRU) has considerable experience in the development and use of building simulation tools. These offer a useful mathematical test bed for the design and performance analysis of a range of microgeneration technologies such as ground source heat pumps (GSHP) when integrated into buildings. This presentation will highlight the capabilities of building simulation with regards to analysing low carbon energy systems such as GSHPs and will highlight areas of potential research and development in modelling tools.

11:25 Coffee Break

11:40 Case history performance

Chair: Robin Curtis Recorder: Peter Smith

Replacing oil fired boilers by GSHP pumps in existing school buildings in Reading Rayner Mayer

There are a number of schools in Reading which are currently heated by oil fired boilers. When these come to the end of their working life, the question for both the schools and the Borough Council is whether to bypass gas heating and to consider using renewable heating systems like GSHP. The first school which is being considered is A and B blocks of Prospect

• College. One of the key issues is how to anticipate future needs when building schools for the

future funding will be used to refurbish or rebuild these blocks.

Keble College energy piles Natasha Kefford

In 2006 Arup led a DTI Partners in Innovation (PII) project into the ground storage of building

• energy. Part of this work highlighted the lack of case histories detailing the performance of

ground energy systems in England. To improve upon the lack of published data, an agreement was reached between Arup and SEEDA (South East England Development Agency) to undertake energy pile monitoring at the Sloane Robinson Building, Keble College, Oxford. This presentation summarises the findings from the first monitoring report.

12:20 Lunch 13:00 Swedish Perspective on GSHP Research Goran Hellstrom 13:10 Geothermal Piles – Codes of Practice

Chair: Tony Amis Recorder: John Patch

Knightsbridge Palace Hotel Tony Amis

The proposal is to undertake a conductivity trial of a loop installed within a diaphragm wall panel at Knightsbridge palace Hotel before excavation and then again once excavation is completed to ascertain the effects on overall conductivity values by the removal of soil from

• ne face.

NHBC - Energy piles for houses Duncan Nicholson

NHBC guide on piling has been written. It includes a section on energy pile for houses. This considers the code for Sustainable Homes future requirements for zero carbon emissions. In addition specification for energy piles are discussed.

Geotechnical Design of Heat Exchanger Piles Herve Peron

There is currently a lack of established calculation method for the geotechnical design of heat exchanger piles, although the technology is experiencing a fast expansion. Instead of quantifying the effects of temperature changes on the static behaviour of heat exchanger piles, the common geotechnical practice is to apply a large overall security factor. This is done in

• rder to be on the side of safety with respect to thermal effects. The few existing in situ

experiments show that applying a thermal load induces a significant change in the stress-strain state of a pile. This talk presents a geotechnical numerical design method, based on the load transfer approach, which assesses the main effects of temperature changes on pile behaviour. The method is validated on the basis of two in situ measurements of the loads and deformations experienced by heat exchanger test piles. The occurrence of critical design situations is further discussed. Some conclusions are formulated on concrete failure and the full mobilization of the pile shaft friction and base resistance during the operation of the heat exchange system.

13:55 Geothermal piles – Design & Modelling

As above

Performance of Ground Energy Systems Installed in Foundations William Powrie

Research ongoing at the University of Southampton aims to address areas of uncertainty regarding the thermal behaviour of ground energy systems installed in foundations. These uncertainties include the consequences of real ground conditions including the influence of stratification, geological variability, moisture migration and groundwater flow. The research also aims to consider the long term behaviour, especially interactions between adjacent

• developments. This presentation will consider the limitations of current design theory, the

importance of energy pile aspect ratios, initial numerical simulations of the performance of ground energy systems and plans for future research.

Foundation Heat Exchanger Research Simon Rees

Where domestic heating and cooling loads are modest it has been demonstrated that ground source heat pump systems can operate successfully using heat exchangers incorporated into foundation excavations. This configuration is very advantageous in terms of capital cost. Although prototype Foundation Heat Exchanger designs exist no suitable design or simulation tools are available. De Montfort University is working with Oklahoma State University and Oak Ridge National Lab to develop a detailed simulation tool for such systems. The model is being validated using data collected from low energy homes in Tennessee.

Selection of material used for thermopiles for recycling heat within a building Gautami Patel

Tests using thermocouple embedded in concrete cubes and embedded in the circulating liquids in the model thermopiles were used to identify the most suitable concrete mix and circulating fluid for energy piles. Three concrete mix designs were prepared for comparison. The sample cement mix contained a) 100% Portland cement b) Portland cement and pulverised fly ash and 3) Portland cement and ground granulated blast furnace slag. Water, glycol solution and a saline solution were tested for their thermal properties on each sample concrete mix. Temperature recordings were taken until equilibrium was achieved and data was analysed giving concluding remarks and recommendations.

14:35 Coffee Break

14:50 Geothermal Pile – Monitoring

As above

Some Geotechnical Aspects of Energy Piles Kenichi Soga

The presentation will discuss some geotechnical considerations needed to design energy piles in order to ensure that the structural performance is preserved. The discussion is based on data interpretation of several case histories in Europe. The current understanding of the problem and future research needs will be presented

Monitoring of the ground temperature and performance of a ground source heat pump system with piled foundation heat exchangers for a residential building over two heating seasons Chris Wood

As the heat loads of modern residential buildings are continually reducing, it is now considered that the use of residential energy piles could provide the necessary heat requirement. A test plot of 72m2 (ground floor area) was produced with 21 x 10m deep concrete piles, with a single U-tube pipe in each and a heat rejection facility was utilised to provide a load comparable to that of a modern 4 bedroom detached dwelling. Testing of the energy piles has been conducted over two heating seasons of 2007/2008 and 2008/2009. The ground temperature and heat pump performance has been monitored and analysed over this period.

US Research in to Energy Piles Richard Fragaszy

In this presentation I will describe two recently started research projects on energy piles funded by the US National Science Foundation (NSF). One project being carried out at Virginia Tech will include full scale field tests of isolated energy piles. The other project at the University of Colorado will include centrifuge tests of model energy piles to explore the effects of thermal effects of the energy pile on soil-pile interaction. Both projects will include a modelling component.

Research on The Long Term Monitoring Performance of Energy Pile Echo Ouyang

As a part of GSHP solution, energy pile has been considered as an economic solution by adding a small premium overall construction cost to enable geothermal energy extraction. However, there is very limited information available regarding the influence of heating and cooling cycles on the geotechnical performance of piled foundations. A long term energy pile monitoring programme has been set up at Bankside, London in 2009. It was motivated by the recent investigation from an energy pile load test at Lambeth College. This presentation will explain the details of project set-up, research interests and future prospects.

16:00 Ground Source Heat Pump Association

T and SC - Design Guide & Training Andy Howley

Introduction to work being carried out by GSHPA Standards committee

16:10 Seminar Closing Address

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