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The vertical borehole heat exchangers were surrounded by the heterogeneous multilayered geological environment and groundwater flow that affected the performance of borehole plants. In this paper, the field investigation of vertical borehole ground heat exchangers in capital city Vilnius (Visoriai), Lithuania is presented. The numerical heat transfer model considering seven different geological strata was developed using the cylindrical heat sink model for vertical borehole inside by solving the soil mass and heat transfer equations with groundwater flow. The numerical multilayered ground vertical borehole heat transfer model was calculated and validated by in-situ thermal response test data. The numerical model results were also compared with the homogeneous finite difference model expressed by the temperature response functions (well known as “g-functions”). The practical realization of g-functions was designed in the Earth Energy Designer as a practical tool for geoengineers designing the vertical borehole plants. The temperature profiles at borehole wall at different heating times were presented and explored together with relative errors. The numerical model will be used as a practical tool for the Lithuanian Geological Survey under the Ministry of Environment to estimate the underground conditions for the consumption of shallow geothermal energy.

Despite increasing energy efficiency requirements, the full potential of energy efficiency is still unlocked, many buildings in the EU tend to consume more energy than predicted. Gathering data and developing models to predict occupants&rsquo, behaviour is seen as the next frontier in sustainable design. Measurements in the analysed open-space office showed accordingly 3.5 and 2.7 times lower occupancy compared to the ones given by DesignBuilder&rsquo, s and EN 16798-1. This proves that proposed occupancy patterns are only suitable for typical open-space offices. The results of the previous studies and proposed occupancy prediction models have limited applications and limited accuracies. In this paper, the hybrid differential evolution online sequential extreme learning machine (DE-OSELM) model was applied for building occupants&rsquo, presence prediction in open-space office. The model was not previously applied in this area of research. It was found that prediction using experimentally gained indoor and outdoor parameters for the whole analysed period resulted in a correlation coefficient R2 = 0.72. The best correlation was found with indoor CO2 concentration&mdash, R2 = 0.71 for the analysed period. It was concluded that a 4 week measurement period was sufficient for the prediction of the building&rsquo, s occupancy and that DE-OSELM is a fast and reliable model suitable for this purpose.

In this work, the method of radial basis function (RBF) is used for the borehole heat exchanger transfers (BHET) problems. The RBF method is an efficient mesh free technique for the numerical solution of partial differential equations. The condition number of the system of linear equations (matrix A) is large it means that the ill-conditioning of matrix A makes the numerical solution unstable. Tikhonov regularization (TR) method are presented to solve such ill-conditioned systems. In this work, generalized cross-validation (GCV) method is carried out to determine the regularization parameter ξ for the TR method that minimizes the GCV function. The some practical results of numerical experiments are presented., Šiame tyrime yra taikomas radialinių bazinių funkcijų metodas (RBF) vertikaliems kolektoriams, analizuojant šilumos perdavimo problematiką. RBF metodas yra ekonomiškas betinklis metodas sprendžiant diferencialines lygtis. Lygčių sistemos (matrica A) sąlyginis skaičius yra dažnai didelis, todėl matrica A yra silpnai sąlyginė, o gautas skaitinis sprendinys nestabilus. Tichonovo regularizacijos (TR) metodas yra taikomas šiai problemai eliminuoti, gautas apibendrintu abipusio palyginimo metodu (GCV) gaunamas regularizacijos parametras ξ TR metodui, minimizuojant GCV funkciją. Rezultatuose pateiktos kelios rekomendacijos.

The vertical borehole ground heat exchange performance is still the issue for the engineers installing vertical borehole ground plants using ground-coupled heat pumps. Besides geological and climate change challenges, they face the extraordinary heat transfer process between the circulating fluid and the ground surrounding the U-tube and interactions of vertical boreholes. This paper describes the technique to evaluate the grout, soil thermal parameters and borehole thermal resistance simultaneously using the particle swarm optimization algorithm. The reference thermal response data set from the sandbox laboratory was used for the analysis. A thermal response test (TRT) was made, including the different temperature response functions, for a few time scales. The estimates and errors of the grout, soil thermal conductivity and borehole resistivity were presented and compared with the results of the laboratory experiment and researchers. The target functions, in our case root mean square error values, were less than 0.034 for all analysis cases. The calculation algorithm was written using the Matlab 2016 program and could be easily expanded by increasing the number of target functions and evaluation algorithms. The presented TRT data analysis will increase the knowledge about the vertical borehole ground heat exchange design.

Dirbtiniai neuroniniai tinklai vis dažniau taikomi ne tik diagnostikos, finansų, kontrolės, kompiuterinės grafikos srityse, bet ir inžinerinėje geologijoje. Šiame darbe tyrinėjant Lietuvos gruntų stipruminių savybių rodiklius pirmą kartą buvo panaudotas dirbtinių neuroninių tinklų apmokymo metodas. Tyrimui pasirinktas Stabatiškės aikštelės moreninis molinis gruntas. Aikštelėje atlikti statinio zondavimo bandymai, skirti nustatyti sąlyginį gruntų stiprumą. Taip pat įvertinti gruntų skersinės bangos greičiai (Vs). Apmokant neuroninį tinklą buvo panaudotas ekstremalaus apmokymo algoritmas ELM (Extreme learning machine), optimizuojant duomenis – stochastiniai paieškos metodai, kuriais randamas globalus funkcijos minimumas ar maksimumas. Modeliuojant panaudotas diferencialinio skirtumo (DE) algoritmas. Pradiniai įvesties į modelį duomenys: koreguotas kūginis stipris (qt), šoninės trinties stipris (fs), trinties santykis (Rf), vertikalus geostatinis slėgis (σ), vertikalus efektyvus geostatinis slėgis (σ’) ir poringumo koeficientas (e), o ieškomas parametras – skersinės bangos greičiai (Vs). Atlikus modeliavimą sudaryti prognoziniai seisminių bangų greičių analogai, kurie leidžia įvertinti gruntų dinaminių savybių rodiklius neatliekant pačio seisminio bandymo.

The primary objective of this study is to identify the ground thermal properties of the local geological structure and to investigate the geological structure. The knowledge of underground thermal properties is necessary to design borehole heat exchangers (BHE) for Ground Source Heat Pumps (GSHP). Particularly for commercial GSHP, main thermal parameters should be measured on site. A thermal response test (TRT) is performed on one or more borehole heat exchangers in a pilot borehole. This borehole is a part of the borehole field. A TRT enables to collect the data to be used for ground thermal parameters calculation, i. e. the thermal conductivity and resistivity. The heat load to be injected into the BHE is predefined in advance; the resulting temperature changes of the circulating fluid and flow rate are measured. The paper presents a short description of the basic concept and theory of TRT, shortly reviews the experience of this technology. The main aim of the presented study and calculations is to start creating efficient methodology to estimate main thermal parameters (thermal conductivity and thermal resistance) in Lithuania. The most used line-source methods and the results will be presented and compared against the numerical method. Circulating fluid and borehole temperatures would be analytically calculated in order to estimate the impact on the underground temperature field.