# Blockchain Solution for Buildings' Multi-Energy Flexibility Trading Using Multi-Token Standards
## 3 Materials and Methods

Table 6: Cost variation per number of transactions. \begin{table}
\begin{tabular}{p{42.7 pt} p{42.7 pt} p{42.7 pt} p{42.7 pt} p{42.7 pt} p{42.7 pt}} \hline \hline
**Operation** & **Used Gas** & **Tokens (FT/NFT)** & **Transactions** & **Used Cost/Token** \\ \hline Registering as a prosumer and & & & & & \\ minting the equiv. money token & & & & & \\ Registering an ask order and & & & & & \\ minting the energy tokens & & & & & \\ Register a bid order & & & & & \\ Transfer tokens based on trade & & & & & \\ \hline \hline \end{tabular}
\end{table} 
Table 7: Cost distribution per market operation. The evaluation results are promising, showing that our solutions are effective in digitizing the heat and electricity of buildings in various feature combinations and trading scenarios with a significant cost reduction thanks to the heterogenous orders combined with processing multi-energy tokens. The batch transfer offers a decreased cost compared with transferring per energy token type and decreases the cost per transaction, making this approach suitable for working with higher volumes. Conceptualization, O.M. and T.C. ; methodology, T.C. ; software, O.M. ; validation, T.C. and O.M. ; formal analysis, O.M., I.A. and T.C. ; investigation, I.A. ; writing--original draft preparation, O.M., T.C. and I.A. ; writing--review and editing, I.A. and T.C. ; visualization, O.M. and I.A. ; funding acquisition, T.C. All authors have read and agreed to the published version of the manuscript. This research was partially funded by European Commission as part of the H2020 Framework Programme, grant number 957816 (BRIGHT) and Horizon Europe Framework Programme grant number 101103998 (DEDALUS), and by the Romanian Ministry of Education and Research, CNCS/CCCDI-UEFISCDI, project grant number PN-III-P3-3.6-H2020-2020-0031 within PNIII. Not applicable. The authors declare no conflict of interest. ## References

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