# Toward a Practical Digital Twin Platform Tailored to the Requirements of Industrial Energy Systems
## 2 State of the Art
### Barriers Impeding Digital Twin Implementation  
The distinct features of IES, which we outlined in Section 2.1, present challenges for the implementation of DTs in these systems in addition to general technical barriers. The fact that DTs are relatively scarcely addressed in the literature relating to the energy domain both gives evidence to such challenges and reinforces the underdevelopment of DTs for IES. In that regard, we see the energy domain at a similar stage as the process industry, where similar difficulties led to the fact that little research on DTs has been conducted [64]. This fact is supported by the review from [PERSON] et al. [11], where only 50 papers were retrieved for process or energy DT within a thousand research papers on DTs in general since 2010. [PERSON] et al. [65] recently presented a systematic review of barriers for DT implementation in the process industry. Such barriers are equally present in the energy domain. A summary of the most crucial barriers impeding DT development from a technical perspective is given in Table 2.  
System integration issues (B1) include interoperability issues and often problems with legacy systems. [PERSON] et al. [66] stated that such DT challenges fall into the area of IoT and IIoT. DT implementations should thus not only feature a standardized architecture but also a certain flexibility to retrofit existing infrastructure. This is especially critical for IES that feature very long lifetimes. Security issues (B2) are a barrier that is not necessarily crucial during DT development but during DT deployment. The key enabling technologies for DT must follow the current practices and updates in security and privacy regulations to resolve this barrier [66]. Performance issues (B3) cannot be solved alone by large computational capacities but include aspects of standardization and scalability. Standardization will facilitate the interoperability of new and existing supporting software [37]. Only when standardization is achieved can DT really thrive in the energy sector due to the easy exchange of information and models. Data quality issues (B5) include the lack of methodologies, low data validity or low DT maturity that results, e.g., in information resulting from DT models that are untrustworthy or incomprehensible. This is crucial in IES, where many sources of uncertainty complicate operation. Organizational issues (B4) and environmental issues (B6) feature multidisciplinary problems that also needs to be tackled from the area of business management, impeding the fast development of DTs. \begin{table}
\begin{tabular}{l l l} \hline \hline
**ID** & **Barrier Category** & **Challenges** \\ \hline B1 & System integration issues & Lack of system integration; Interoperability issues; Legacy systems \\ B2 & Security issues & Data protection; Real-time communication; Robustness \\ B3 & Performance issues & Prediction accuracy; Data volume; Scalability; Flexibility; Standardization \\ B4 & Organizational issues & Fragmented data management; Data availability; Technology investment decisions \\ B5 & Data quality issues & Data validity; Lack of methodologies and tools; Low DT maturity \\ B6 & Environmental issues & Software decisions; High-fidelity modelling; Multi-disciplinary; Heterogeneity \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Most crucial technical barriers impeding DT implementation. We endorse and apply the categories established by [PERSON] et al. [65] for the process industry and provide a summary of topics causing difficulty in the energy domain. [PERSON] et al. [11] stated that DT development in the energy sector is inherently multidisciplinary, including fields such as chemical, mechanical, electrical, civil, software engineering and data science. Additionally, DT operation should ideally be unclosed to non-technical staff and business managers. Thus, further non-technical challenges arise that have to be countervailed by a convenient DT architecture.