Comparing heat flow models for interpretation of precast quadratic pile heat exchanger thermal response tests

Alberdi-Pagola, Maria; Poulsen, Søren Erbs; Loveridge, Fleur; Madsen, Søren; Jensen, Rasmus Lund

doi:10.1016/j.energy.2017.12.104

Cited by 25 publications

(23 citation statements)

References 25 publications

Supporting

Mentioning

Contrasting

Unclassified

Order By: Relevance

“…Guidance based on the The pile G-function approach with lower bounds performs similarly to the ILSM in terms of accuracy but does this from assessment of the early time transient data. It gives a slight underestimation of λ g , which is consistent with another test on smaller energy piles by Alberdi-Pagola et al [36], but most importantly gives good results from fitting to the early time, even for the region of Fo1-5. The G-function approach explicitly treats the pile and ground thermal conductivity separately and models the early time transient behavior.…”

Section: Alternative Determination Of Thermal Resistancesupporting

confidence: 89%

“…Research has been carried out to try and assess this using field data [20,34] and numerical studies [35]. Approaches have included looking at the required test duration [36] as well as whether alternative interpretation methods would be more appropriate [20]. Where a line source method is used in interpretation there is a potential for systematic overestimation of the thermal conductivity [30] and this is observed in many field studies [22,37,38].…”

Section: In-situ Characterizationmentioning

confidence: 99%

“…Where a line source method is used in interpretation there is a potential for systematic overestimation of the thermal conductivity [30] and this is observed in many field studies [22,37,38]. Much better estimates of ground and pile thermal characteristics have been obtained when numerical simulation has been used [36,39]. However, most comprehensive studies of pile TRTs where both field data and independent assessment of ground thermal properties are available have been limited to smaller diameter piles (up to approximately 450 mm in diameter), for example [20,34,36].…”

Section: In-situ Characterizationmentioning

confidence: 99%

“…Much better estimates of ground and pile thermal characteristics have been obtained when numerical simulation has been used [36,39]. However, most comprehensive studies of pile TRTs where both field data and independent assessment of ground thermal properties are available have been limited to smaller diameter piles (up to approximately 450 mm in diameter), for example [20,34,36]. There is therefore a need to extend experience to larger diameters and to provide guidance for these cases.…”

Section: In-situ Characterizationmentioning

confidence: 99%

See 3 more Smart Citations

Thermal Response Testing of Large Diameter Energy Piles

2019

Self Cite

View full text Add to dashboard Cite

Energy piles are a novel form of ground heat exchanger (GHE) used in ground source heat pump systems. However, characterizing the pile and ground thermal properties is more challenging than for traditional GHEs. Routine in-situ thermal response testing (TRT) methods assume that steady state conditions in the GHE are achieved within a few hours, whereas larger diameter energy piles may take days or even weeks, thereby incurring significant costs. Previous work on pile TRTs has focused on small diameters up to 450 mm. This paper makes the first rigorous assessment of TRT methods for larger diameter piles using field and laboratory datasets, the application of numerical and analytical modelling, and detailed consideration of costs and program. Three-dimensional numerical simulation is shown to be effective for assessing the data gathered but is too computationally expensive for routine practice. Simpler fast run time steady state analytical models are shown to be a theoretically viable tool where sufficient duration test data is available. However, a new assessment of signal to noise ratio (SNR) in real field data shows how power fluctuations cause increased uncertainty in long duration tests. It is therefore recommended to apply transient models or instead to carry out faster and more cost-effective borehole in-situ tests for ground characterization with analytical approaches for pile characterization.

show abstract

Section: Alternative Determination Of Thermal Resistancesupporting

confidence: 89%

Section: In-situ Characterizationmentioning

confidence: 99%

Section: In-situ Characterizationmentioning

confidence: 99%

Section: In-situ Characterizationmentioning

confidence: 99%

See 2 more Smart Citations

Thermal Response Testing of Large Diameter Energy Piles

2019

Self Cite

View full text Add to dashboard Cite

show abstract

“…The soil thermal conductivity λ s and volumetric heat capacity pc s at Rosborg Gymnasium were estimated in [21] by means of thermal response testing (TRT) and transient plane heat source measurements on soil samples (Figure 2b). The upper 1 m of silty sand has a thermal conductivity and volumetric heat capacity of ca.…”

Section: Study Site and Geological Settingmentioning

confidence: 99%

An Experimental and Numerical Case Study of Passive Building Cooling with Foundation Pile Heat Exchangers in Denmark

et al. 2019

Self Cite

View full text Add to dashboard Cite

Technologies for energy-efficient cooling of buildings are in high demand due to the heavy CO2 footprint of traditional air conditioning methods. The ground source heat pump system (GSHP) installed at the Rosborg Gymnasium in Vejle (Denmark) uses foundation pile heat exchangers (energy piles). Although designed for passive cooling, the GSHP is used exclusively for heating. In a five-week test during the summer of 2018, excess building heat was rejected passively to the energy piles and the ground. Measured energy efficiency ratios are 24–36 and the thermal comfort in conditioned rooms is improved significantly relative to unconditioned reference rooms. A simple model relating the available cooling power to conditioned room and ground temperatures is developed and calibrated to measured test data. Building energy simulation based estimates of the total cooling demand of the building are then compared to corresponding model calculations of the available cooling capacity. The comparison shows that passive cooling is able to meet the cooling demand of Rosborg Gymnasium except for 7–17 h per year, given that room temperatures are constrained to < 26 °C. The case study clearly demonstrates the potential for increasing thermal comfort during summer with highly efficient passive cooling by rejecting excess building heat to the ground.

show abstract

Development and testing of a novel geothermal wall system

Baralis

Barla

2021

Int J Energy Environ Eng

View full text Add to dashboard Cite

Shallow geothermal energy systems have the potential to contribute to the decarbonization of heating and cooling demands of buildings. These systems typically present drawbacks as high initial investments and occupancy of wide areas. In this study, a novel energy wall system is proposed to overcome the limitations of conventional geothermal applications in urban areas. The system is characterized by ease of installation, low initial costs and applicability to existing buildings undergoing energy retrofitting. The paper illustrates the implementation of the prototype of such a system to an existing structure in Torino (Italy). An overview of the components is given together with the interpretation of an illustrative test carried out in heating mode. The data from both heating and cooling experimental campaigns allow us to highlight the potential of the proposed technology. The results suggest that an average thermal power of about 17 W per unit area can be exchanged with the ground in heating mode, while an average of 68 W per unit area is exchanged in cooling operations. The negligible impact on the stress–strain state of the wall and the surrounding soil thermal and hygrometric regime is also testified by the results collected. These aspects are associated with a reduced probability of interferences with other installations in highly urbanized areas, easiness of installation and affordable cost.

show abstract

Comparing heat flow models for interpretation of precast quadratic pile heat exchanger thermal response tests

Cited by 25 publications

References 25 publications

Thermal Response Testing of Large Diameter Energy Piles

Thermal Response Testing of Large Diameter Energy Piles

An Experimental and Numerical Case Study of Passive Building Cooling with Foundation Pile Heat Exchangers in Denmark

Development and testing of a novel geothermal wall system

Contact Info

Product

Resources

About