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.

The present study examines and compares the effect of surface treatments of nano-silica using internal olefins sulphonates (IOS_20–24 and IOS_19–23), anionic surfactants. The effect of surface modification on colloidal stability, wettability alteration and oil-water interfacial tension reduction were analyzed. Silica nanoparticles were characterized using Field Emission Scanning Electron Microscope (FESEM) and integrated energy-dispersive X-ray spectroscopy (EDX) before and after surface treatment. Using Turbiscan classic, the optimal nanosilica concentration and inspection of the coated particles dispersion stability with the help of light transmission behavior through the nanofluid was carried out. The stability was found to be enhanced as the mean light transmission declined only after surfactant treatment in both IOS coated nano-silicas but IOS_19–23 O-342 coated dispersions proved to be more stable among all three. RAME-HART Goniometer was used to perform interfacial tension (IFT) and contact angle measurements. IFT was found to be reduced by 48% after the surfactant treatment in case of IOS_19–23 O-342 coated nanosilica. Both surface treatments of nanosilica and increasing silica concentration caused significant reduction and altering wettability towards more water wet. The results revealed that IOS coatings improved the efficiency of NPs dispersion in terms of altered wettability and reduced IFT that mimics their potential for EOR applications.