A review on energy piles design, sizing and modelling

Fadejev, Jevgeni; Simson, Raimo; Kurnitski, Jarek; Haghighat, Fariborz

doi:10.1016/j.energy.2017.01.097

Cited by 130 publications

(80 citation statements)

References 41 publications

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“…Using directly the pipes' outlet temperature induces a 54% overestimation of the heat flux, while the exact ground surface temperature above the piles reduces the error to 0.03%.2 of 17 approximations, such as infinitely extended line sources and a constant heat flux inside an infinite and homogeneous medium. These could be extended in several ways though [12,15,16], from analytical g-functions [17] to superposition of thermal response functions (the so-called Hellström approach) [18,19]. Unfortunately, unavoidable approximations (such as constant wall temperatures) still limit the predictive power of these models [10,12].Numerical computations can instead relax many assumptions that are generally needed to solve analytical models [20,21].…”

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confidence: 99%

“…These could be extended in several ways though [12,15,16], from analytical g-functions [17] to superposition of thermal response functions (the so-called Hellström approach) [18,19]. Unfortunately, unavoidable approximations (such as constant wall temperatures) still limit the predictive power of these models [10,12].Numerical computations can instead relax many assumptions that are generally needed to solve analytical models [20,21]. The geometry in particular can be more complex, accounting for finite lengths, thermal interaction of the heat exchangers, multilayer soil [22] and inclusion of the ground water flow [23,24].…”

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confidence: 99%

“…Finally, thermomechanical effects that are induced on the heat exchanger constitute an emergent and promising field of investigation [47,48]. Experimental research is very active as well, on each and every level, providing empirical support and validation to both analytical and numerical models [10,49].Despite a number of encouraging results, even in the numerical modelling of GHE a number of issues still need to be addressed [10,12,50]. In this paper we are mostly concerned with the assessment of variable ground surface temperatures.…”

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confidence: 99%

“…In the case of energy piles, this is generally described as the surface temperature of the building floor slab, which is assumed to coincide with the indoor air temperature. The soil region surrounding the building floor slab is exposed to outdoor air temperature, which unfortunately cannot be modelled in TRNSYS nor IDA-ICE due to lack of implementation [12,27]. Hypothetically, heat transfer in the soil region surrounding the building should affect the soil temperature development underneath, altering the heat transfer between the energy piles and, ultimately, their thermal yield.…”

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confidence: 99%

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Energy Pile Field Simulation in Large Buildings: Validation of Surface Boundary Assumptions

Ferrantelli

Fadejev

Kurnitski

2019

Preprint

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As the energy efficiency demands for future buildings become increasingly stringent, preliminary assessments of energy consumption are mandatory. These are possible only through numerical simulations, whose reliability crucially depends on boundary conditions. We therefore investigate their role in numerical estimates for the usage of geothermal energy, performing annual simulations of transient heat transfer for a building employing a geothermal heat pump plant and energy piles. Starting from actual measurements, we solve the heat equations in 2D and 3D using COMSOL Multiphysics and IDA-ICE, and discover a negligible impact of the multiregional ground surface boundary conditions. Moreover, we verify that the thermal mass of the soil medium induces a small vertical temperature gradient on the piles surface. We also find a roughly constant temperature on each horizontal cross-section, with nearly identical values if the average temperature is integrated over the full plane or evaluated at one single point. Calculating the yearly heating need for an entire building we then show that the chosen upper boundary condition affects the energy balance dramatically. Using directly the pipes’ outlet temperature induces a 54% overestimation of the heat flux, while the exact ground surface temperature above the piles reduces the error to 0.03%.

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Energy Pile Field Simulation in Large Buildings: Validation of Surface Boundary Assumptions

Ferrantelli

Fadejev

Kurnitski

2019

Preprint

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“…The significant advantage of using energy piles over borehole systems is that they require no additional structural or hydraulic measures because they are installed within elements that are already needed for structure [2]. Energy piles utilize renewable geothermal energy for buildings heating and cooling purposes and need proper design and sizing in order to end up with high plant efficiency [3].…”

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Uniform Fractional Factorial Design Tables for Energy Piles With Maximum Thermal Conductance

Ahmed¹,

Al‐Khawaja²,

Suleiman³

2017

WIT Transactions on Ecology and the Environment

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Energy Piles are the heat exchangers of Ground Source Heat Pumps (GSHP) that transfer the buildings heat to the lower temperature shallow ground reducing the energy consumption in the cooling of buildings. These piles are designed with main objective of lowest thermal resistance. In this paper, nine factors influencing the thermal resistance of the energy pile are defined and statistically evaluated. These nine factors are; number of tubes, pile diameter, tube diameter, tube thickness, tube location, pile conductivity, tube conductivity, soil conductivity, and water flow rate. The thermal resistance of the energy pile is calculated using the line source analytical model. The significance of these factors is evaluated using fractional factorial uniform design tables. The results show significant decrease in the pile thermal resistivity with the increase of the tube diameter, number of tubes, water flow rate, and tube and pile thermal conductivities. On the other hand, decrease of the tube thickness, and pile diameter slightly decrease the pile thermal resistivity. Furthermore, the tubes located near the piles outer surface show significant decrease in the pile thermal resistivity. Also, the soil thermal conductivity has shown insignificant effects on the pile thermal resistivity.

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Underground energy storage utilizing concrete building foundation: Experimental and numerical approach

Mousa

Bayomy

Wang³

et al. 2020

Int J Energy Res

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Space heating and cooling represent 63% of total building energy demand. In the present study, the concept of concrete foundation piles was used as an underground storage medium. This system requires no additional drilling costs or space, unlike conventional boreholes. A laboratory-scaled experiment facility was designed to experimentally investigate the thermal response of a concrete pile during the charging and discharging processes. The amount of energy stored and released during each process was evaluated. A flow rate parametric study was also conducted to explore the effect of the laminar and turbulent flow behavior. In order to complement the experimental study, an extensive CFD model was developed and compared with the experimental data. There was good agreement between the numerical and experimental results for each process at different flow rates. The results revealed that increasing the flow rate increases not only the heat rejection and extraction but also the storage efficiency.

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A review on energy piles design, sizing and modelling

Cited by 130 publications

References 41 publications

Energy Pile Field Simulation in Large Buildings: Validation of Surface Boundary Assumptions

Energy Pile Field Simulation in Large Buildings: Validation of Surface Boundary Assumptions

Uniform Fractional Factorial Design Tables for Energy Piles With Maximum Thermal Conductance

Underground energy storage utilizing concrete building foundation: Experimental and numerical approach

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