A Critical Review on the Use of Shallow Geothermal Energy Systems for Heating and Cooling Purposes

Abstract

The reduction of CO2 emissions has become a global concern. In this regard, the EU intends to cut CO2 emissions by 55% by 2030 compared to those of 1990. The utilization of shallow geothermal energy (SGE) in EU countries is considered the most effective measure for decarbonizing heating and cooling. SGE systems utilize heat energy collected from the earth’s crust to provide secure, clean, and ubiquitous energy. This paper provides a literature review on the use of SGE for heating and cooling purposes. The latest advances in materials, new innovative structures, and techno-economic optimization approaches have been discussed in detail. Shallow geothermal energy’s potential is first introduced, and the innovative borehole structures to improve performance and reduce installation cost is outlined. This is followed by an extensive survey of different types of conventional and thermally enhanced collectors and grouts. Attention is mainly given to the techno-economic analysis and optimization approaches. In published case studies, the least economic break-even point against fossil fuel-based heating systems occurs within 2.5 to 17 years, depending on the local geological conditions, installation efficiency, energy prices, and subsidy. Ground source heat pumps’ cost-effectiveness could be improved through market maturity, increased efficiency, cheap electricity, and good subsidy programs.

Potential of low-enthalpy geothermal energy to degrade organic contaminants of emerging concern in urban groundwater

“…In summer, groundwater has a lower temperature than the atmospheric one, thus, groundwater can be used for cooling by transferring the heat of the building to groundwater, which produces the rise of aquifer temperature. In winter, the system is reversed and groundwater is used to heat the building by transferring the groundwater heat to the building, which reduces the aquifer temperature 28 , 29 . Thus, the use of groundwater for cooling and heating induces variations of aquifer temperature 30 , 31 .…”

Improvement in Operation Efficiency of Shallow Geothermal Energy System—A Case Study in Shandong Province, China

“…T(x, y, z, t) Γ wi = 16 °C Γ wi is inected wells for heating period T(x, y, z, t) Γ wi = 26 °C Γ wi is inected wells for cooling period (4) (2) Initial conditions…”

“…SGE is used in many countries, with a rising number of installations in recent decades; SGE systems have been developed and utilized in 40 countries [3]. SGE accounts for 59.2% of directuse geothermal energy consumption per year in the world, and the total installed capacity and energy production are 77,547 MWt and 599,981 TJ, respectively [4]. According to a report by the International Energy Agency (IEA, 2021), the number of heat pumps has grown 10% per year in the last 5 years, and by 2050, geothermal energy production will reach about 100~210 TWh/y [5].…”

Combined “Renewable Energy–Thermal Energy Storage (RE–TES)” Systems: A Review

“…Hybrid ATES systems combine ATES with other renewable energy sources, such as solar thermal or geothermal energy, to increase their efficiency and overall performance [114]. Additionally, there are also shallow ATES systems that use a network of underground pipes to store heat or cold in the soil layers close to the surface [115], and deep ATES systems that store heat or cold in deeper aquifers [116]. Notably, the performance and effectiveness of solar ponds depend on the parts integrated into them, including the solar collector, the heat exchanger, and the storage system.…”