## 3 Definitions of Scenarios, Characteristics, and Considerations  
The technical-economic analysis was performed for three scenarios, in which functioning, economical, and marketing aspects were considered. In the definitions of the scenarios the followings were considered:  
* The thermal energy demand of the building
* Its reintegration into the centralized heat supply system of UPB by injecting a quantity of heat [3,4]. The aspects considered in the technical-economic analysis, valid for all scenarios, were the following:
* As a reference, the current heat supply of the building from a local thermal power plant, which uses natural gas, was considered. * The production of electricity resulting from photovoltaic panels, as well as from PVT, covers a part of the electrical consumption of the thermal scheme, namely the one related to ensuring the necessary heat and cold of the building [5]. * By implementing the new solution, based on renewable sources, the CO\({}_{2}\) emissions were reduced both at the level of the building frame and the analysed system, this reduction being directly proportional to the reduction of the consumption of primary resources (saved natural gas) [6]. * The value of CO\({}_{2}\) certificates related to reducing the amount of CO\({}_{2}\) by implementing the new energy supply solution were considered as revenues, or _virtual receipts_. * The share provided by UPB was considered as the value of the investment from its own funds. The difference up to the total value of the investment that the analysed solution implies is considered non-reimbursable from European funds (grants). * The calculations were performed in two ways: 1. The value of the investment was equal to the insured quota from the UPB budget. 2. The value of the investment was equal to the total investment costs assumed by the implementation of the new solution. Characteristic aspects of Scenario 1:
* By implementing the thermal energy supply solution of the building based on the integration of geothermal-solar systems, it is considered that natural gas saving is achieved both for the building \begin{table}
\begin{tabular}{l l l} \hline \hline
**Energy Consumption/Energy Production** & **UM** & **Value** \\ \hline - thermal energy production—heating & MWh & 281.00 \\ - thermal energy consumption—heating & MWh & 127.00 \\ - thermal energy consumption injection—DH & MWh & 154.00 \\ - electricity consumption for cold production & MWh & 4.43 \\ - electricity consumption for production—DHW & MWh & 0.69 \\ - electricity production from PV + PVT & MWh & 50.00 \\ - electricity consumption for building heating (related to GT-S scheme) & MWh & 42.33 \\ - electricity consumption for heat injection (related to GT-S scheme) & MWh & 51.33 \\ - total electricity consumption (related to GT-S scheme) & MWh & 93.67 \\ - reduced CO\({}_{2}\) through the GT-S scheme for the building & t/year & 31.88 \\ - reduced CO\({}_{2}\) through the GT-S scheme for the network & t/year & 32.00 \\ - building heating gas consumption & MWh/year & 138.00 \\ - combined heat power plant heating gas consumption (equivalent to injection) & MWh/year & 192.50 \\ - total gas consumption & MWh/year & 330.50 \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Consumption of thermal and electrical energy of target building and the productions related to the hybrid solution. and the centralized heat supply system of UPB (corresponding to the production of heat injected into the system). This economy is quantified economically by the _annual saving of expenses with the fuel (natural gas) saved_. * The total annual expenses include both the maintenance and operation expenses related to the solution, as well as the expenses related to the annual electricity consumption, in addition to the production provided by the photovoltaic panels. Characteristic aspects of Scenario 2:
* The virtual receipts of \"virtual sales\" of the entire amount of heat produced by the implementation of the proposed scheme were considered as income.