Skip to main page content
U.S. flag

An official website of the United States government

Dot gov

The .gov means it’s official.
Federal government websites often end in .gov or .mil. Before sharing sensitive information, make sure you’re on a federal government site.

Https

The site is secure.
The https:// ensures that you are connecting to the official website and that any information you provide is encrypted and transmitted securely.

Access keys NCBI Homepage MyNCBI Homepage Main Content Main Navigation
. 2021 Oct 23;21(21):7027.
doi: 10.3390/s21217027.

Inquiry into the Temperature Changes of Rock Massif Used in Energy Production in Relation to Season

Martin Klempa  1 , Jan Latal  2 , Barbora Grafova  3 , Michal Matloch Porzer  1 , Mojmir Vrtek  4 , Antonin Kunz  1 , Petr Siska  2
Affiliations

Inquiry into the Temperature Changes of Rock Massif Used in Energy Production in Relation to Season

Martin Klempa et al. Sensors (Basel). .

Abstract

This research was undertaken to perform and evaluate the temperature measurement in the ground utilized as an energy source with the goal to determine whether significant temperature variations occur in the subsurface during the heating season. The research infrastructure situated on our University campus was used to assess any variations. The observations were made at the so called "Small Research Polygon" that consists of 8 monitoring boreholes (Borehole Heat Exchangers) situated around a borehole used as an energy source. During the heating season, a series of monthly measurements are made in the monitoring boreholes using a distributed temperature system (DTS). Raman back-scattered light is analysed using Optical Frequency Time Domain Reflectometry (OTDR). Our results indicate that no noticeable changes in temperature occur during the heating season. We have observed an influence of long-term variations of the atmospheric conditions up to the depth of a conventional BHE (≈100 m). The resulting uncertainty in related design input parameters (ground thermal conductivity) was evaluated by using a heat production simulation. Production data during one heating season at our research facilities were evaluated against the design of the system. It is possible to construct smaller geothermal installations with appropriate BHE design that will have a minimal impact on the temperature of the surrounding rock mass and the system performance.

Keywords: Raman-OTDR (DTS); borehole heat exchanger; ground source heat pump; ground temperature field; ground thermal conductivity; temperature measurement.

PubMed Disclaimer

Conflict of interest statement

The authors declare no conflict of interest. The funders had no role in the design of the study; in the collection, analyses, or interpretation of data; in the writing of the manuscript, or in the decision to publish the results.

Figures

Figure 1
Figure 1
Location of boreholes in the Small Research Polygon geothermal station.
Figure 2
Figure 2
The structure of rock environment at Small Research Polygon according to the temperature influences of individual zones [35].
Figure 3
Figure 3
Development of temperature changes in energetically utilized operational borehole A0 during one heating season.
Figure 4
Figure 4
Time detail of the temperature change course in the A0 borehole with the lowest temperatures.
Figure 5
Figure 5
Graph of temperature changes with the depth at chosen monitoring borehole B0 and B2 of the Small Research Polygon.
Figure 6
Figure 6
Graph of temperature changes with the depth at chosen monitoring borehole C1 and D of the Small Research Polygon.
Figure 7
Figure 7
Graph of temperature changes with the depth at chosen monitoring borehole E2 and E3 of the Small Research Polygon.
Figure 8
Figure 8
Graph of temperature changes with the depth at chosen monitoring borehole F1 and G0 of the Small Research Polygon.
Figure 9
Figure 9
Temperatures of the fluid at the outlet of BHE A0 as predicted with EED software during the design (solid line) and measured during production (red dot).
Figure 10
Figure 10
Mean of the fluid temperatures at the inlet and outlet of the BHE at the end of each month during the simulation period of 10 years. Each curve is representing a simulation at certain thermal conductivity of the ground while the other simulation parameters remain constant.
Figure 11
Figure 11
Average of measurements in boreholes in relation to seasons.
Figure 12
Figure 12
Neutral zone in the depth of approx. 38 m.
See this image and copyright information in PMC

References

    1. Bujok P., Grycz D., Klempa M., Kunz A., Porzer M., Pytlik A., Rozehnal Z., Vojčinák P. Assessment of the influence of shortening the duration of TRT (thermal response test) on the precision of measured values. Energy. 2014;64:120–129. doi: 10.1016/j.energy.2013.11.079. - DOI
    1. Lazzari S., Priarone A., Zanchini E. Long-term performance of BHE (borehole heat exchanger) fields with negligible groundwater movement. Energy. 2010;35:4966–4974. doi: 10.1016/j.energy.2010.08.028. - DOI
    1. EGEC . Geothermal Market Report 2016. 6th ed. European Geothermal Energy Council; Brussels, Belgium: 2017.
    1. Bujok P. Metodika Projektování a Instalace Vrtaných Tepelných Výměníků Pro různě Velké systémy na Základě Stanovených Fyzikálních Vlastností Horninového Masivu. 2015. Project TA č. 01020932. (In Czech)
    1. Giordano N., Comina C., Mandrone G., Cagni A. Borehole thermal energy storage (BTES). First results from the injection phase of a living lab in Torino (NW Italy) Renew. Energy. 2016;86:993–1008. doi: 10.1016/j.renene.2015.08.052. - DOI

LinkOut - more resources