izv. prof. Luka Perković
Amalia Lekić Brettschneider, mag. ing. petrol.
Sustainable development has several key elements: to diagnose the current state of industrial and residential systems, to include appropriate targeting of the needs for heat and power supply and targeting power generation operation. Over two million geothermal heat pumps were installed in Europe as of June 2020 (EGEC, 2020). Sweden, Germany, France and Switzerland are countries with the most installations of shallow geo-thermal heat capture systems, which accounts for 64 % of all installed capacity in Europe (Perez, 2020). Integration of PV and geothermal heat pumps can be used for cost-effective decarbonisation of the energy consumption of the household sector. Integration of heating, cooling and electricity demand with renewable electricity supply can lead to enhanced heat recovery of geothermal reservoir with the low year-to-year thermal degradation of the reservoir.
Figure 1. Scheme of the microgrid system consisting of houses, PV systems, heat pump and shallow geothermal reservoirs, DSO: Distribution System Operator
Using the RES2GEO model (Perković et al., 2021.) the analysis for a hypothetical residential microgrid has been done. Simulation time was one year with resolution of one hour. Both thermal and electricity energy balance has been calculated, and the shallow geothermal reservoir has been calculated with the separate distributed 2D finite volume analysis.
Figure 2. Schematic view of the reservoir model with coaxial borehole heat exchanger
The borehole heat exchanger was coaxial, and parameters of microgrid are: 20 houses with annual heat demand of 281 MWh, Cooling demand 30 MWh and electricity demand 81 MWh. The component parameters are: installed PV at 160 kW, heater at 80 kW and number of wells is 16 with total length of 100 m for each borehole heat exchenager. Results show that PV can be used to decarbonize electricity, and reheating of the shallow geothermal reservoir can be used as a demand response for using addional PV electricity that would be otherwise curtailed.
Figure 3. Energy balance over the period of one year: positive values are system supply, negative values are system demand; color code is: orange - PV; blue - import; green - heater; red - heat pump; purple - pump; brown - electricity demand; pink - export; grey - curtailment
To illustrate seasonal changes in reservoir temperature, where reservoir temperature is determined as an average temperature of the reservoir in the radius of 1 meter from the borehole heat exchanger, an additional simulation has been performed for the period of 20 years.
Figure 4. Reservoir temperature for the period of 20 years, as an average temperature of the reservoir in the radius of 1 meter from the borehole heat exchanger; color code blue - instantaneous temperature; red - annual average; red dotted - initial reservoir temperature
It can be seen that the instantaneous temperature oscillates with an amplitude of approximately 4 degrees Celsius. Average annual temperature drops significantly over the first five years, especially in the first year when the drop is around 2.5 degrees C.
The conclusion is that surplus of PV electricity, that otherwise cannot be exported to the system operator, can be effectively used to reheat the shallow geothermal reservoir (demand response) enabling the simultaneous decarbonization of both heat and electricity.
Literatura:
EGEC Geothermal, Available: https://www.egec.org/the-geothermal-energy-market-grows-exponentially-but-needs-the-right-market-conditions-to-thrive/. (accessed 2 December 2020)..
Pérez, R.E. European Federation of Geologists, Available: https://eurogeologists.eu/esteban-shallow-geothermal-energy-geological-energy-for-the-ecological-transition-and-its-inclusion-in-european-and-national-energy-policies/. (ac-cessed 1 December 2020)..
Perković, Luka : Integration of Photovoltaic Electricity with Shallow Geothermal Systems for Residential Microgrids: Proof of Concept and Techno-Economic Analysis with RES2GEO Model, Energies 2021, 14(7), 1923; https://doi.org/10.3390/en14071923
_________________________________________________________________________________
assoc. prof. Luka Perković
Associate professor on Faculty of Minig, Geology and Petroleum engineering, holds one course at postgraduate study. Field of research is related to energy planning and integration of renewable energy sources into energy systems.
Amalia Lekić Brettschneider, mag. ing. petrol.
PhD student and research assistant at the Faculty of Mining, Geology and Petroleum Engineering. Doctoral disseration focuses on decarbonization of energy systems with the use of the knowledge from petroleum engineering and energy planning.
E-portfolio: moodle.srce.hr/eportfolio/user/view.php?id=40334
Publons: publons.com/researcher/3979448/luka-perkovic/
Facebook: www.facebook.com/luka.perkovic
CROSBI: www.bib.irb.hr/pretraga?operators=and|Perkovi%C4%87,%20Luka%20%2824723%29|text|profile