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• @ Source -Energy pipe deemed sustainable for 25 year period. • Horizontal spacing of system should occur at 8 m for large scale applications. • @ Source -Energy pipe deemed sustainable for 4, 5, 6, 7, and 8 m depths. • HDPE shows negligible effects on thermal performance of system. • @ Source -Energy pipe deemed sustainable for 50 % and 75 % sewage pipe capacity. Extracting heat from a sewage pipe through a typical horizontal ground heat exchanger has recently been introduced as a renewable energy alternative to reduce fossil fuel usage. This paper presents a novel design for a ground heat exchanger that extracts heat from the surrounding soil and sewage within the pipe while simultaneously being carried to a wastewater treatment plant. This research focuses on the long-term efficiency of the system under transient conditions in a cold climate. A numerical model using COMSOL Multiphysics was developed to verify the sustainability of the system for over 25 years. The model used constant inlet fluid temperatures to evaluate heat transfer with convective pipe flow and conductive phase change within the soil. The results showed a maximum temperature change in the surrounding soil adjacent to the heat extraction system over 25 years was 0.10 °C during the heating season in Winnipeg, Manitoba. The distance at which the heat extraction system did not show an impact on temperature change of adjacent soil was determined at 4 m. Critical parameters in this evaluation were system depth, sewage level, and the high-density polyethylene pipe thermal properties. The sustainability of the system was not affected by the system depth due to thermal balancing between climatic, subsurface and sewage heat fluxes. Sustainable behavior was achieved at 50 % and 75 % of sewage pipe capacity. The effect on thermal performance from the high-density polyethylene pipe thermal properties was deemed insignificant. [ABSTRACT FROM AUTHOR]

Natural gas and electricity together accounted for 82.5% of all residential energy use in Canada in 2013 with nearly half of the average household consumption from natural gas used for heating. Energy demand is projected to grow exponentially due to population increase. In May 2015, Canada submitted its Intended Nationally Determined Contribution to the United Nations Framework Convention on Climate Change which included an economy-wide target to reduce greenhouse gas emissions by 30% below 2005 levels by 2030. As of 2016, Canada is projected to significantly miss its 2020 and 2030 climate target with the set of measures it currently has in place. The projected target for 2020 is 622 mega tons of carbon dioxide equivalent (Mt CO2 eq.) and the projected outcome is 768 Mt CO2 eq. The projected target for 2030 is 524 Mt CO2 eq. and the projected outcome is 815 Mt CO2 eq. This leads to the demand of innovative solutions to reduce fossil fuel usage and to switch to renewable energy. A recent heat extraction system has been developed that combines a typical horizontal ground heat exchanger with a sewage pipe. The heat extraction system is a hollow concrete cylinder with a helical high-density polyethylene pipe embedded within the pipe walls. The high-density polyethylene pipe has an outlet and inlet on each length of pipe which are attached to a heat pump which circulate a heat exchange fluid. As the heat exchange fluid cycles through the system, it extracts heat from the surrounding soil and sewage within the pipe while simultaneously carrying the sewage to a waste treatment plant. A heat pump uses the obtained energy to heat a building in cold weather and cool a building in hot weather. This system has not been studied under transient conditions in an extreme climate. In this study, a numerical model is developed using the finite element solver COMSOL Multiphysics to investigate heat transfer coupled with fluid flow by solving partial differential equations where temperature is the dependent variable. A soil block is initially modelled to simulate a control scenario of ground temperature in order to extract data at specific locations for specific times. Following are multiple simulations which implemented the heat extraction system with various energy demands into the soil block to compare ground temperatures at specific locations. A five year period of sustainability is demonstrated through comparison of temperature differentials of adjacent soil locations to the benchmarks established. The maximum temperature change over the five year period interpreted is 1.8 degrees centigrade at 0.1 meters adjacent to the heat extraction system for 75% energy demand of a bed and breakfast located south of Winnipeg. The system is shown to handle an energy demand of up to 6 typical residential houses in Winnipeg when the sewage temperature is kept constant. [ABSTRACT FROM AUTHOR]

Abstract Snow melting systems using geothermal energy piles are a clean technology to overcome the problems of traditional chemical-based snow melting methods. This paper aims to study the feasibility of such systems in six major cities (Calgary, Edmonton, Montreal, Ottawa, Toronto and Winnipeg) in Canada. The amount of energy, as well as the inlet temperature of a hydronic system required to warm up and keep the surface temperature of a bridge slab unit above 0 °C during a typical snowfall were determined based on a transient energy balance at the slab surface and weather conditions for each city. The coefficient of performance (COP) of the heat pump for a bridge was then derived for each city based on its specific local geological conditions and heating demands. Also, the problems related to the ground thermal imbalance due to the operation of such systems were addressed. Finally, the economic feasibility study was performed to compare costs between a snow melting system for a bridge deck using geothermal energy piles and an electricity-based heating system. It was concluded that the snow melting system using geothermal energy piles is efficient and cost effective. However, the extent of efficiency and saving varies with implementation areas. Highlights • The COP of the heat pump depends on weather conditions. • Thermal recharging shortly after snowfalls is important. • Winnipeg is the most suitable place for the geothermal pile based heating system. • Snow melting system using geothermal piles is cost effective. [ABSTRACT FROM AUTHOR]