Abstract
Geothermal energy is a form of renewable energy, which offers carbon-free solutions for heating and cooling spaces. This study evaluates the use of renewable asphalt heat energy in frozen ground conditions. Asphalt heat energy can be harnessed using a low-energy network, heat collection pipes and heat pumps. This study measured temperatures under the asphalt layer during a three-year period between 2014 and 2017. Measurements were made using a distributed temperature sensing method based on light scattering. Temperatures taken at four different depths under the asphalt (0.5 m, 1.0 m, 3.0 m and 10 m) are presented here. These temperatures are compared with that detected at the depth at which the temperature remains constant all year round. The temperature difference curve between 0.5 m depth and the constant soil temperature depth indicates that from April to October the soil at 0.5 m depth is warming and the temperature difference is positive, even as much as 18 °C. Instead, at the 3.0 m depth, the difference curve is smoother and it varies only from −5 to +5 °C. It is positive from June to November. The surface layer (0 m–1.0 m) is suitable for harvesting heat that can be stored in a deeper (1.5 m–3.0 m) purpose-built storage or in a bedrock heat battery. The calculated heat capacities indicate that asphalt energy, because of high temperatures, is a noteworthy renewable energy source.
Highlights
It is commonly accepted that climate change and global warming are serious issues that can be addressed by reducing greenhouse gas (GHG) emissions
The temperatures at a depth of 0.5 m (Figure 3) under the asphalt layer are very promising for heat collection from May until as late in the year as September
A purpose-designed storage deeper under the asphalt, or a bedrock heat battery, could act as a seasonal thermal energy storage (STES). It would be loaded by the asphalt energy during the summer and the heat would be exploited at cooler times of the year
Summary
It is commonly accepted that climate change and global warming are serious issues that can be addressed by reducing greenhouse gas (GHG) emissions. According to Shrestha et al [1], technological innovations and research to develop new solutions are essential to limit global warming. This is true in developing countries, where there is still much to do. In Finland geothermal energy systems have been a popular heat source for new single family-houses in recent years. Heat pump systems most commonly use the bedrock, the ground and the air as a heat source. People are prepared to invest in renewable sources, driven by the desire to cut their electricity and heating bills. Finland will abandon the burning of coal for energy by 2030. The aim is for at least 38% of the energy used to come from renewables
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