# Autonomous Cyber-Physical Systems Enabling Smart Positive Energy Districts
## 3 Emerging Technologies Enabling Positive Energy Districts
### Blockchain
Smart meters send real-time data to the blockchain for secure and auditable energy billing. 5. _Carbon Credit and Emissions Trading:_ Carbon credits are generated by producing clean energy and reducing emissions. They are used to weight emissions from various sources, are often issued by governments or international organizations, and can be traded on carbon markets. One carbon credit is equivalent to 1000 kg of carbon dioxide. The difference the carbon emissions allowed and those actually emitted is called carbon credit [68]. Blockchain supplies tokenized traceable unchallengeable carbon credits, facilitates transparent and automated trading of credits, and verifies emission reductions in real-time (via IoT sensors and blockchain logging). 6. _Tokenization of Energy Assets:_ A considerable barrier in the energy sector is the financial strain caused by rising electricity costs. Blockchain allows fractional ownership of e.g., solar farms and battery storage by the use of tokens that correspond to shares in energy-producing assets, hence enabling micro-investments by citizens [69]. Residents invest a certain amount into, e.g., a solar farm and receive dividends or energy credits proportional to their stake
7. _Resilience and Disaster Recovery:_ Ensuring energy services during grid outages or cyberattacks. Blockchain supports off-grid P2P networks for energy resilience, maintains decentralized records for continuity in outages, and can automate fallback energy sharing strategies. In the event of a grid failure, the local PED automatically shifts to a backup mode, with blockchain coordinating energy distribution from batteries and microgrids. 4 Challenges and Potential Solutions in Utilizing Emerging Technologies in Positive Energy Districts  
PED project challenges and barriers differ according to the development stage they are in [70]. The complex planning stage of existing urban refurbishment is, however, the most crucial. Practical PED experience is primarily based on recently built districts or planned future districts. However, considering that 85% of the buildings in the EU were constructed before year 2000 and that 75% of them display poor energy performance [71], the challenges will mainly be to refurbish existing buildings and regions to the standards of PEDs. The main challenges associated with the integration of PEDs in urban areas include the following [17]:  
* Lack of accepted methods for assessing energy balances;
* Difficult to integrate renewable energy systems into redundant and old-fashioned urban infrastructures;
* Multi-stakeholder collaboration needed in order to secure local acceptance and safeguard reasonable development processes. Other challenges, but also opportunities, can be found in data analysis, interoperability, business models, management, and data security. There are several barriers and challenges associated with the transition to renewable energy systems, including high initial expenses, and political and societal barriers [64]. As [PERSON] et al. [2] argue, the novelty, adaptability, and complicated nature of PEDs has led to numerous interpretations and definitions. This, in turn, has initiated challenges regarding implementation, evaluation, comparison, and replication of PEDs. They identified \"_seven interacting challenges: governance, incentive, social, process, market, technology and context_\" [2]. In this study, we mainly look at the challenges from a technological point of view, but as [PERSON] et al. [2] emphasize, a deeper cross-disciplinary understanding of the challenges is needed due to the complexity of developing PEDs. Hence, we also present other key barriers that may influence technical challenges. In the following subsections, challenges and potential solutions in using emerging technologies in PEDs are proposed.