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Predicting the long-term thermal performance of an energy pile ground heat exchanger system requires a computationally efficient model that captures the three-dimensional features and interacting thermal boundary conditions found in such systems. We present a model that employs a response factor approach to predicting long-term thermal behaviour based on a Dynamic Thermal Network representation. This allows fully three-dimensional geometric representation of the problem and application of boundary conditions at the ground and building sub-surfaces in addition to the pipes. The model has been validated using data from long-term monitoring of a pile in Belgium excited by a combination of heating and cooling demands in a range of environmental conditions. We further demonstrate application of the model to simulated annual building energy demands and the significance of treatment of the upper surface boundary conditions. The model is shown to be capable of representing building system and environmental conditions effectively and furthermore computationally efficient enough for routine design and simulation tasks.
Simon Rees; Gust Van Lysebetten. A response factor approach to modelling long-term thermal behaviour of energy piles. Computers and Geotechnics 2020, 120, 103424 .
AMA StyleSimon Rees, Gust Van Lysebetten. A response factor approach to modelling long-term thermal behaviour of energy piles. Computers and Geotechnics. 2020; 120 ():103424.
Chicago/Turabian StyleSimon Rees; Gust Van Lysebetten. 2020. "A response factor approach to modelling long-term thermal behaviour of energy piles." Computers and Geotechnics 120, no. : 103424.
Ground thermal energy is a sustainable source that can substantially reduce our dependency on conventional fuels for heating and cooling of buildings. To exploit this source, foundation sub-structures with embedded heat exchanger pipes are employed. Diaphragm wall heat exchangers are one such form of ground heat exchangers, where part of the wall is exposed to the basement area of the building on one side, while the other side and the further depth of the wall face the surrounding ground. To assess the thermal performance of diaphragm wall heat exchangers, a model that takes the wall geometry and boundary conditions at the pipe, basement, and ground surfaces into account is required. This paper describes the development of such a model using a weighting factor approach, known as Dynamic Thermal Networks (DTN), that allows representation of the three-dimensional geometry, required boundary conditions, and heterogeneous material properties. The model is validated using data from an extended series of thermal response test measurements at two full-scale diaphragm wall heat exchanger installations in Barcelona, Spain. Validation studies are presented in terms of comparisons between the predicted and measured fluid temperatures and heat transfer rates. The model was found to predict the dynamics of thermal response over a range of operating conditions with good accuracy and using very modest computational resources.
Ida Shafagh; Simon Rees; Iñigo Urra Mardaras; Marina Curto Janó; Merche Polo Carbayo. A Model of a Diaphragm Wall Ground Heat Exchanger. Energies 2020, 13, 300 .
AMA StyleIda Shafagh, Simon Rees, Iñigo Urra Mardaras, Marina Curto Janó, Merche Polo Carbayo. A Model of a Diaphragm Wall Ground Heat Exchanger. Energies. 2020; 13 (2):300.
Chicago/Turabian StyleIda Shafagh; Simon Rees; Iñigo Urra Mardaras; Marina Curto Janó; Merche Polo Carbayo. 2020. "A Model of a Diaphragm Wall Ground Heat Exchanger." Energies 13, no. 2: 300.
Borehole heat exchangers are a key technological element of geothermal energy systems and modelling their behaviour has received much attention. The aim in the work reported here has been to produce a reference data set that can be used in analysis of large borehole heat exchanger systems and validation of models of such. A monitoring exercise to collect high frequency data from a large ground heat exchanger array consisting of 56 boreholes over 38 months since the start of operations is reported. The system is associated with a mixed-use university building that has both heating and cooling loads. Ground heat exchange was found to be dominated by rejection of heat over the monitoring period and modest seasonal increases in temperatures. The ground heat exchanger installation has been additionally characterised by analysis of thermal response test data to estimate the effective ground and grout thermal properties. The utility of the measurements as a reference data set by presenting a model validation study is furthermore demonstrated. This has highlighted some features of the data that are more significant in systems of larger scale. These reference data are being made openly available for further work on performance analysis and model validation.
Selvaraj S. Naicker; Simon J. Rees. Long-term high frequency monitoring of a large borehole heat exchanger array. Renewable Energy 2019, 145, 1528 -1542.
AMA StyleSelvaraj S. Naicker, Simon J. Rees. Long-term high frequency monitoring of a large borehole heat exchanger array. Renewable Energy. 2019; 145 ():1528-1542.
Chicago/Turabian StyleSelvaraj S. Naicker; Simon J. Rees. 2019. "Long-term high frequency monitoring of a large borehole heat exchanger array." Renewable Energy 145, no. : 1528-1542.
Selvaraj S. Naicker; Simon J. Rees. Performance analysis of a large geothermal heating and cooling system. Renewable Energy 2018, 122, 429 -442.
AMA StyleSelvaraj S. Naicker, Simon J. Rees. Performance analysis of a large geothermal heating and cooling system. Renewable Energy. 2018; 122 ():429-442.
Chicago/Turabian StyleSelvaraj S. Naicker; Simon J. Rees. 2018. "Performance analysis of a large geothermal heating and cooling system." Renewable Energy 122, no. : 429-442.
Simon J Rees. Closing the performance gap through better building physics. Building Services Engineering Research and Technology 2017, 38, 125 -132.
AMA StyleSimon J Rees. Closing the performance gap through better building physics. Building Services Engineering Research and Technology. 2017; 38 (2):125-132.
Chicago/Turabian StyleSimon J Rees. 2017. "Closing the performance gap through better building physics." Building Services Engineering Research and Technology 38, no. 2: 125-132.
Simon J. Rees. An extended two-dimensional borehole heat exchanger model for simulation of short and medium timescale thermal response. Renewable Energy 2015, 83, 518 -526.
AMA StyleSimon J. Rees. An extended two-dimensional borehole heat exchanger model for simulation of short and medium timescale thermal response. Renewable Energy. 2015; 83 ():518-526.
Chicago/Turabian StyleSimon J. Rees. 2015. "An extended two-dimensional borehole heat exchanger model for simulation of short and medium timescale thermal response." Renewable Energy 83, no. : 518-526.
Note: In lieu of an abstract, this is an excerpt from the first page. We have found the following error in the publishing history of this article which was recently published in Energies [1].
Simor Rees; Robin Curtis. Correction: Rees, S. and Curtis, R. National Deployment of Domestic Geothermal Heat Pump Technology: Observations on the UK Experience 1995–2013. Energies 2014, 7, 5460–5499. Energies 2014, 7, 6224 -6224.
AMA StyleSimor Rees, Robin Curtis. Correction: Rees, S. and Curtis, R. National Deployment of Domestic Geothermal Heat Pump Technology: Observations on the UK Experience 1995–2013. Energies 2014, 7, 5460–5499. Energies. 2014; 7 (9):6224-6224.
Chicago/Turabian StyleSimor Rees; Robin Curtis. 2014. "Correction: Rees, S. and Curtis, R. National Deployment of Domestic Geothermal Heat Pump Technology: Observations on the UK Experience 1995–2013. Energies 2014, 7, 5460–5499." Energies 7, no. 9: 6224-6224.
Uptake of geothermal heat pump technology in the UK and corresponding development of a domestic installation industry has progressed significantly in the last decade. This paper summarizes the growth process and reviews the research that has been specifically concerned with conditions in the UK. We discuss the driving forces behind these developments and some of the supporting policy initiatives that have been implemented. Publically funded national trials were completed to assess the performance and acceptance of the technology and validate design and installation standards. We comment on both the technical and non-technical findings of the trials and the related academic research and their relevance to standards development. A number of technical issues can be identified—some of which may be particular to the UK—and we suggest a number of research and development questions that need to be addressed further. Current national support for the technology relies solely on a tariff mechanism and it is uncertain that this will be effective enough to ensure sufficient growth to meet the national renewable heat target in 2020. A broader package of support that includes mandatory measures applied to future housing development and retrofit may be necessary to ensure long-term plans for national deployment and decarbonization of heat are achieved. Industry needs to demonstrate that efficiency standards can be assured, capital costs reduced in the medium-term and that national training schemes are effective.
Simon Rees; Robin Curtis. National Deployment of Domestic Geothermal Heat Pump Technology: Observations on the UK Experience 1995–2013. Energies 2014, 7, 5460 -5499.
AMA StyleSimon Rees, Robin Curtis. National Deployment of Domestic Geothermal Heat Pump Technology: Observations on the UK Experience 1995–2013. Energies. 2014; 7 (8):5460-5499.
Chicago/Turabian StyleSimon Rees; Robin Curtis. 2014. "National Deployment of Domestic Geothermal Heat Pump Technology: Observations on the UK Experience 1995–2013." Energies 7, no. 8: 5460-5499.
The application of hybrid or mixed-mode ventilation in severe arid climates and its integration with other passive cooling strategies is very challenging. This paper presents a systematic evaluation of the performance of various mixed-mode cooling strategies for office buildings with different levels of internal heat gain operated in four cities representative of arid climates. The results of simulations made with EnergyPlus are evaluated in terms of appropriate thermal comfort criteria and subsequently potential reductions in plant energy consumption so that the most effective strategies to mitigate the energy consumption associated with air-conditioning processes. The results show that hybrid approaches to maintaining indoor environmental conditions have the potential to save approximately half of the plant energy consumption compared to common active air-conditioning systems. Savings in plant energy due to the application of mixed-mode strategies that include low energy cooling technologies such as radiant, evaporative and ground-coupled cooling could exceed 90%. We conclude that mixed-mode cooling strategies should be able to provide satisfactory indoor environments and can result in highly efficient office building designs and so should be considered for application in arid climates.
Sherif Ezzeldin; Simon Rees. The potential for office buildings with mixed-mode ventilation and low energy cooling systems in arid climates. Energy and Buildings 2013, 65, 368 -381.
AMA StyleSherif Ezzeldin, Simon Rees. The potential for office buildings with mixed-mode ventilation and low energy cooling systems in arid climates. Energy and Buildings. 2013; 65 ():368-381.
Chicago/Turabian StyleSherif Ezzeldin; Simon Rees. 2013. "The potential for office buildings with mixed-mode ventilation and low energy cooling systems in arid climates." Energy and Buildings 65, no. : 368-381.
The Dynamic Thermal Network (DTN) approach to the modelling of transient conduction was conceived by Claesson (1999,2002,2003) as an extension of the network representation of steady-state conduction processes. The method is well suited to the simulation of building fabric components such as framed walls and thermally massive structures such as basements but can also be applied to the long timescale simulation of other conduction problems. The theoretical basis of the method and its discretized form is outlined in this paper and a new numerical procedure for the calculation of the necessary weighting factor data is presented. Such data has previously been generated for three-dimensional bodies by a heuristic process of blending analytical solutions and numerical data. The numerical approach reported here has the advantage of accommodating parametric representations of multi-dimensional geometries and allows the data to be produced in an automated fashion and so more easily incorporated into simulation tools. Enhancements to the data reduction procedure and a generalised approach to representing complex boundary conditions are also presented. The numerical procedure has been validated by a series of comparisons with analytical conduction heat transfer solutions and discretization errors were found to be acceptably small. Compared to numerical methods, calculations using the DTN method were found to be up to four orders of magnitude quicker but with comparable accuracy
Simon Rees; Denis Fan. A numerical implementation of the Dynamic Thermal Network method for long time series simulation of conduction in multi-dimensional non-homogeneous solids. International Journal of Heat and Mass Transfer 2013, 61, 475 -489.
AMA StyleSimon Rees, Denis Fan. A numerical implementation of the Dynamic Thermal Network method for long time series simulation of conduction in multi-dimensional non-homogeneous solids. International Journal of Heat and Mass Transfer. 2013; 61 ():475-489.
Chicago/Turabian StyleSimon Rees; Denis Fan. 2013. "A numerical implementation of the Dynamic Thermal Network method for long time series simulation of conduction in multi-dimensional non-homogeneous solids." International Journal of Heat and Mass Transfer 61, no. : 475-489.
Common approaches to the simulation of borehole heat exchangers assume heat transfer within the circulating fluid and grout to be in a quasi-steady state and ignore axial conduction heat transfer. This paper presents a numerical model that is three-dimensional, includes explicit representations of the circulating fluid and other borehole components, and so allows calculation of dynamic behaviours over short and long timescales. The model is formulated using a finite volume approach using multi-block meshes to represent the ground, pipes, fluid and grout in a geometrically correct manner. Validation and verification exercises are presented that use both short timescale data to identify transport delay effects, and long timescale data to examine the modelling of seasonal heat transfer and show the model is capable of predicting outlet temperatures and heat transfer rates accurately. At long timescales borehole heat transfer seems well characterized by the mean fluid and borehole wall temperature if the fluid circulating velocity is reasonably high but at lower flow rates this is not the case. Study of the short timescale dynamics has shown that nonlinearities in the temperature and heat flux profiles are noticeable over the whole velocity range of practical interest. The importance of representing the thermal mass of the grout and the dynamic variations in temperature gradient as well as the fluid transport within the borehole has been highlighted. Implications for simplified modelling approaches are also discussed.
Simon J. Rees; Miaomiao He. A three-dimensional numerical model of borehole heat exchanger heat transfer and fluid flow. Geothermics 2013, 46, 1 -13.
AMA StyleSimon J. Rees, Miaomiao He. A three-dimensional numerical model of borehole heat exchanger heat transfer and fluid flow. Geothermics. 2013; 46 ():1-13.
Chicago/Turabian StyleSimon J. Rees; Miaomiao He. 2013. "A three-dimensional numerical model of borehole heat exchanger heat transfer and fluid flow." Geothermics 46, no. : 1-13.
Foundation Heat Exchangers (FHX) are a novel form of ground heat exchanger for residential applications. The recently developed dynamic thermal network approach has been applied to formulate a model of the FHX that includes the basement, pipes and adjacent ground. This response factor approach allows complex three-dimensional geometries, such as this, to be represented and simulated efficiently. The formulation of the method and its application to the FHX is described along with a numerical procedure to calculate the required weighting factor series. An improved method of calculating these data and reducing it to a compact form is presented. Some modification of the original method has also been necessary to implement the boundary conditions associated with the heat exchanger pipes and ground surface. Data from an installation at an experimental house have been used to validate the model.
Denis Fan; Simon Rees; Jeffrey Spitler. A dynamic thermal network approach to the modelling of Foundation Heat Exchangers. Journal of Building Performance Simulation 2013, 6, 81 -97.
AMA StyleDenis Fan, Simon Rees, Jeffrey Spitler. A dynamic thermal network approach to the modelling of Foundation Heat Exchangers. Journal of Building Performance Simulation. 2013; 6 (2):81-97.
Chicago/Turabian StyleDenis Fan; Simon Rees; Jeffrey Spitler. 2013. "A dynamic thermal network approach to the modelling of Foundation Heat Exchangers." Journal of Building Performance Simulation 6, no. 2: 81-97.
Simon Rees; Philip Haves. An experimental study of air flow and temperature distribution in a room with displacement ventilation and a chilled ceiling. Building and Environment 2013, 59, 358 -368.
AMA StyleSimon Rees, Philip Haves. An experimental study of air flow and temperature distribution in a room with displacement ventilation and a chilled ceiling. Building and Environment. 2013; 59 ():358-368.
Chicago/Turabian StyleSimon Rees; Philip Haves. 2013. "An experimental study of air flow and temperature distribution in a room with displacement ventilation and a chilled ceiling." Building and Environment 59, no. : 358-368.
Simon J. Rees; Joseph Walkenhorst. Large-Scale Credit Risk Loss Simulation. GPU Computing Gems Jade Edition 2012, 323 -335.
AMA StyleSimon J. Rees, Joseph Walkenhorst. Large-Scale Credit Risk Loss Simulation. GPU Computing Gems Jade Edition. 2012; ():323-335.
Chicago/Turabian StyleSimon J. Rees; Joseph Walkenhorst. 2012. "Large-Scale Credit Risk Loss Simulation." GPU Computing Gems Jade Edition , no. : 323-335.
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 around the loop. However, in domestic ground source heat pump (GSHP) systems, the heat pump and circulating pumps switch on and off during a given hour; therefore, the effect of the thermal mass of the circulating fluid and the dynamics of fluid transport through the loop has important implications for system design. This may also be important in commercial systems that are used intermittently. This article presents transient simulation of a domestic GSHP system with a single BHE using a dynamic three-dimensional (3D) numerical BHE model. The results show that delayed response associated with the transit of fluid along the pipe loop is of some significance in moderating swings in temperature during heat pump operation. In addition, when 3D effects are considered, a lower heat transfer rate is predicted during steady operations. These effects could be important when considering heat exchanger design and system control. The results will be used to develop refined two-dimensional models.
Miaomiao He; Simon Rees; Li Shao. Simulation of a domestic ground source heat pump system using a three-dimensional numerical borehole heat exchanger model. Journal of Building Performance Simulation 2011, 4, 141 -155.
AMA StyleMiaomiao He, Simon Rees, Li Shao. Simulation of a domestic ground source heat pump system using a three-dimensional numerical borehole heat exchanger model. Journal of Building Performance Simulation. 2011; 4 (2):141-155.
Chicago/Turabian StyleMiaomiao He; Simon Rees; Li Shao. 2011. "Simulation of a domestic ground source heat pump system using a three-dimensional numerical borehole heat exchanger model." Journal of Building Performance Simulation 4, no. 2: 141-155.
Results are presented from a monitoring study of the performance of a sample of UK domestic PV systems. Five-minute average climatic and performance data was recorded for 27 PV systems at two sites for up to 2 years of operation. On average, the annual energy losses due to faults were 3.6% (Site A, first year of operation), 6.6% (Site A, second year of operation) and 18.9% (Site B, first year of operation). Simple empirical models are constructed to describe the performance of the PV systems under ‘normal operation’ (when no faults occur). New analysis techniques are developed which estimate the energy losses of four different fault categories: sustained zero efficiency faults; brief zero efficiency faults; shading; and non-zero efficiency non-shading faults. The results demonstrate that faults have the potential to cause significant energy losses in domestic PV systems. The benefits of applying the data analysis techniques described in this work to PV system clusters and other urban micro-generation technologies are discussed.
S.K. Firth; K.J. Lomas; Simon Rees. A simple model of PV system performance and its use in fault detection. Solar Energy 2010, 84, 624 -635.
AMA StyleS.K. Firth, K.J. Lomas, Simon Rees. A simple model of PV system performance and its use in fault detection. Solar Energy. 2010; 84 (4):624-635.
Chicago/Turabian StyleS.K. Firth; K.J. Lomas; Simon Rees. 2010. "A simple model of PV system performance and its use in fault detection." Solar Energy 84, no. 4: 624-635.
John R. Lister; John M. Rallison; Simon J. Rees. The nonlinear dynamics of pendent drops on a thin film coating the underside of a ceiling. Journal of Fluid Mechanics 2010, 647, 239 .
AMA StyleJohn R. Lister, John M. Rallison, Simon J. Rees. The nonlinear dynamics of pendent drops on a thin film coating the underside of a ceiling. Journal of Fluid Mechanics. 2010; 647 ():239.
Chicago/Turabian StyleJohn R. Lister; John M. Rallison; Simon J. Rees. 2010. "The nonlinear dynamics of pendent drops on a thin film coating the underside of a ceiling." Journal of Fluid Mechanics 647, no. : 239.
Rising buoyant plumes from a point heat source in a naturally ventilated enclosure have been investigated using large-eddy simulation (LES). The aim of the work is to assess the performance and the accuracy of LES for modelling buoyancy-driven displacement ventilation of an enclosure and to shed more light on the transitional behaviour of the plume and the coherent structures involved. The Smagorinsky sub-grid scale model is used for the unresolved small-scale turbulence. The Rayleigh number, Ra is chosen to be in the range where spatial transition from laminar to turbulent flow takes place (Ra = 1.5 × 109). The plume properties (source strength and rate of spread) as well as the ventilation properties (stratification height and temperature of stratified layer) estimated using the theory of Linden et al. are found to agree reasonably well with the LES results. The variation of the plume width with height indicates a linear variation of the entrainment coefficient rather than a constant value used by Linden et al. for a fully turbulent thermal plume. Flow visualisation revealed the nature of the large-scale coherent structures involved in the transition to turbulence in the plume. The most excited modes observed in the velocity, pressure and temperature fields spectra correspond to Strouhal number in the range 0.3 ≤ St ≤ 0.55 which is in agreement with those observed by Zhou et al. for a turbulent forced plume. Excited modes less than thisvalue (St = 0.2) were observed and may be due to low-frequency motions felt throughout the flow.
Ibrahim E. Abdalla; Malcolm J. Cook; Simon J. Rees; Zhiyin Yang. Large-eddy simulation of buoyancy-driven natural ventilation in an enclosure with a point heat source. International Journal of Computational Fluid Dynamics 2007, 21, 231 -245.
AMA StyleIbrahim E. Abdalla, Malcolm J. Cook, Simon J. Rees, Zhiyin Yang. Large-eddy simulation of buoyancy-driven natural ventilation in an enclosure with a point heat source. International Journal of Computational Fluid Dynamics. 2007; 21 (5-6):231-245.
Chicago/Turabian StyleIbrahim E. Abdalla; Malcolm J. Cook; Simon J. Rees; Zhiyin Yang. 2007. "Large-eddy simulation of buoyancy-driven natural ventilation in an enclosure with a point heat source." International Journal of Computational Fluid Dynamics 21, no. 5-6: 231-245.
Xiaobing Liu; Simon Rees; Jeffrey D. Spitler. Modeling snow melting on heated pavement surfaces. Part II: Experimental validation. Applied Thermal Engineering 2007, 27, 1125 -1131.
AMA StyleXiaobing Liu, Simon Rees, Jeffrey D. Spitler. Modeling snow melting on heated pavement surfaces. Part II: Experimental validation. Applied Thermal Engineering. 2007; 27 (5-6):1125-1131.
Chicago/Turabian StyleXiaobing Liu; Simon Rees; Jeffrey D. Spitler. 2007. "Modeling snow melting on heated pavement surfaces. Part II: Experimental validation." Applied Thermal Engineering 27, no. 5-6: 1125-1131.
Xiaobing Liu; Simon Rees; Jeffrey D. Spitler. Modeling snow melting on heated pavement surfaces. Part I: Model development. Applied Thermal Engineering 2007, 27, 1115 -1124.
AMA StyleXiaobing Liu, Simon Rees, Jeffrey D. Spitler. Modeling snow melting on heated pavement surfaces. Part I: Model development. Applied Thermal Engineering. 2007; 27 (5-6):1115-1124.
Chicago/Turabian StyleXiaobing Liu; Simon Rees; Jeffrey D. Spitler. 2007. "Modeling snow melting on heated pavement surfaces. Part I: Model development." Applied Thermal Engineering 27, no. 5-6: 1115-1124.