Borehole heat exchangers (BHEs) are used for transforming a rock mass into an underground heat storage. Usually, their depth does not exceed 200[Formula: see text]m, but some extend to a depth of almost 3000[Formula: see text]m. Underground heat storages can operate as part of heating and cooling systems, often economically. In winter they extract heat from the rock mass for space heating, while in summer the cooled rock mass is used for air conditioning. The heat extracted from buildings via air conditioning is transferred into the rock mass, thereby regenerating its condition for winter time. Deep borehole exchangers also may operate only in the heating mode. Then, the rock resource conditions are regenerated via heat transfer through neighboring rocks. If a groundwater flow is present, the heat can also be removed and the source conditions regenerated through convection. Here, an overview of the use and operation of deep BHEs around the world is provided. Special emphasis is placed on the Carpathians, where numerous analyses of geothermal heat use have been performed since 1999. Examples of calculations for old oil and gas wells as well as negative exploration boreholes are given. Such analyses have been performed for boreholes in Poland and the Ukraine. However, little research has been published on this subject to date, for reasons described herein.

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Research on borehole heat exchangers is described on the development of a method for the determination, based on thermal response tests, of the effective thermal conductivity and the thermal resistivity for borehole heat exchangers. This advance is important, because underground thermal energy storage increasingly consists of systems with a large number of borehole heat exchangers, and their effective thermal conductivities and thermal resistivities are significant parameters in the performance of the system (whether it contains a single borehole or a field of boreholes). Borehole thermal energy storages provide a particularly beneficial method for using ground energy as a clean thermal energy supply. This benefit is especially relevant in cities with significant smog in winter. Here, the authors describe, in detail, the development of a formula that is a basis for the thermal response test that is derived from Fourier’s Law, utilizing a new way of describing the basic parameters of the thermal response test, i.e., the effective thermal conductivity and the thermal resistivity. The new method is based on the resistivity equation, for which a solution giving a linear regression with zero directional coefficient is found. Experimental tests were performed and analyzed in support of the theory, with an emphasis on the interpretation differences that stem from the scope of the test.

The paper deals with the possible use of existing oil wells for geothermal energy production. A mathematical model, describing the process of exploitation of a borehole heat exchanger, has been worked out. It was used for determining energy efficiency, employing the main parameter, i.e., flow of produced heat energy. The results of simulation of borehole heat exchanger operation in deep conditions of Iwonicz Zdrój field’s depleted deposits (Polish Carpathians) are presented. A considerable part of oil deposits in the Carpathian region—a cradle of the world’s oil industry—are to be decommissioned. Owing to the high density of population, the wells are planned to be adapted for borehole heat exchangers for clean energy production for local purposes. The decommissioning costs will be avoided.

The development of techniques and technologies thanks to which parameters of the ground medium can be modified makes specialists look for new recipes of geopolymers -binders for the reinforcing and sealing of unstable and permeable grounds. The sealing slurries are expected to meet a number of strict requirements, therefore it is important to find new admixtures and additives which could modify the fresh and hardened slurry. Special attention has been recently paid to the fluid ash -a by-product of the combustion of hard coals. However, the use of this additive is associated with the application of appropriate superplastifier.Laboratory analyses of rheological parameters of fresh sealing slurries and the ways of improving their liquidity by a properly selected third-generation superplastifier are presented in the paper. The slurries were based on Portland cement CEM I, milled granulated large-furnace slag and fly ash from fluidized-bed combustion of hard coal. Keywords: Cement slurry, Fluid ash, GeopolymersRozwój technik i technologii modyfikacji parametrów ośrodka gruntowego wymusza ciągłe poszukiwanie nowych receptur geopolimerów używanych jako spoiwa do wzmacniania i uszczelniania gruntów niestabilnych i przepuszczalnych. Wychodząc naprzeciw oczekiwaniom spełnienia przez zaczyn uszczelniający szereg rygorystycznych wymagań należy poszukiwać nowych domieszek i dodatków modyfikujących jego parametry w stanie świeżym i stwardniałym. Szczególne znaczenie w ostatnich czasach nabiera wzbogacenie receptur o dodatek popiołów fluidalnych ze spalania węgli kamiennych. Aplikacja tego dodatku wymaga jednak uplastycznienia zaczynu uszczelniającego właściwym superplastyfikatorem.W artykule przedstawiono badania laboratoryjne parametrów reologicznych świeżych zaczynów uszczelniających, w aspekcie poprawy ich płynności przez doświadczalne dobranie superplastyfikatora trzeciej generacji. Zaczyny sporządzono w oparciu o cement portlandzki CEM I, mielony granulowany żużel wielkopiecowy oraz popiół lotny z fluidalnego spalania węgla kamiennego.Słowa kluczowe: zaczyn uszczelniający, popiół fluidalny, geopolimery