Ground-Source Bridge Deck Deicing Systems Using Energy Foundations

Abstract

Ground-source heating of bridge decks can be an alternative to the use of salts and chemicals to deice bridge decks. Energy foundations, geothermal boreholes, shallow trenches or the approach embankment can be utilized as energy storage media and heat exchange pathways to utilize the ground as a heat source. Coupling the energy foundation with a ground-source heat pump can provide higher inlet fluid temperatures and result in more effective bridge heating but at the expense of greater energy consumption and increased system complication. Circulating the fluid directly from the energy foundation to the bridge deck relies heavily on the in-situ ground temperatures. This paper outlines the operational principles and how these are related to the design parameters of bridge deck deicing systems. A series of parametric analyses was performed to investigate the bridge deck heating process. The analyses considered a variety of tube spacings, inlet fluid temperatures (i.e. ground temperatures), flow rates, wind speeds, ambient temperatures and thicknesses of concrete cover over the circulation tubes. The results serve as a benchmark to gauge the operational conditions and the energy requirements for designing ground-source bridge deck deicing systems. Ground temperatures serve as a baseline for heating of bridge decks with passive heating in the winter and this study underlines its limitations at colder environments. This can be overcome by collecting heat from the bridge deck in the summer and injecting the collected heat into the ground to raise the ground temperatures. This stored energy can be reclaimed in the winter when needed. The issues related to heat collection and ground storage are part of a broader study and fall outside the scope of this paper.

Numerical Simulation of Geothermal Heated Bridge Deck

“…In addition, the volume of rebar is relatively small and would require an extremely fine mesh, leading to a significant increase of computation time. Bowers and Olgun (2014) indicated that the effect of rebar was negligible based on their preliminary numerical analyses in COMSOL.…”

“…Additionally, it can also be used to decrease the temperature of bridge decks during concrete curing, and help minimize early age cracking. Similarly, temperature of bridge deck can be regulated to reduce the severity of heating/cooling cycles between day and night in summer (Bowers and Olgun, 2014). Liu et al (2003) conducted simulation on hydronic heating of bridge deck over a lifetime as opposed to singular storm events incorporating a groundsource heat pump.…”

“…A bridge is an integral part of highway infrastructure, and it is also critical to economy and security for a nation (Bowers and Olgun, 2014). Deterioration of the aging bridge infrastructure due to the use of salts or other chemicals for deicing bridge decks causes significant economic and engineering challenges.…”

Performance of a geothermal energy deicing system for bridge deck using a pile heat exchanger

“…Snow accumulation is typically mitigated by a combination of mechanical removal and the use of deicing salt. However, deicing salt is corrosive to steel reinforcements in the bridge structure, which may lead to alkali‐aggregate reactions in concrete as well as environmental issues …”

“…However, deicing salt is corrosive to steel reinforcements in the bridge structure, which may lead to alkali-aggregate reactions in concrete as well as environmental issues. 1 The ground could be regarded as a heat source because its temperature remains relatively constant throughout the year. 2,3 Geothermal energy can be used to build heating and ground-heat pump systems, which have been widely employed to extract geothermal energy in recent years.…”