# Autonomous Cyber-Physical Systems Enabling Smart Positive Energy Districts
## 3 Emerging Technologies Enabling Positive Energy Districts
### Blockchain  
The aim of PEDs to generate renewable energy to a higher extent than they consume prompts a need for decentralized energy management and data transactions that are both secure and economic [62]. Blockchain, a distributed ledger technology, facilitates transparent and secure recording of data and transactions, which enables households, businesses, and PEDs to directly trade excess energy with each other. This decentralized approach validates and verifies transactions, and hence eliminates intermediaries (e.g., banks or governments), reduces waste, increases transparency and accountability in energy systems, reduces transaction costs, and promotes energy efficiency through more localized energy distribution [45]. Blockchain is associated with a decentralized privacy-aware data management framework for PEDs, allowing actors to read, modify, and store data with secure, effective, and scalable outcomes [63]. The use of blockchain is critical in enabling more transparent and more efficient energy systems [64]. As a result, blockchain-based architectures have been put forward to reduce the negative effects of climate change, such CO\({}^{2}\) emissions [65]. These aim to achieve the following:  
* Promote effective integration of energy services delivered to the electricity grid by the PED;
* Support the development of a reliable certification system for energy self-sufficiency;
* Enable effective energy trading management among diverse PEDs. Blockchain facilitates peer-to-peer energy trading and provides a secure and transparent platform for monitoring energy production, consumption, and storage. In addition, smart contracts based on blockchain are able to automate energy transactions and support energy conservation (the choice and practice of using less energy), which leads to both efficient and sustainable energy use [64]. Blockchain can enable the utilization of smart grid systems that use real-time data to optimize energy production, energy storage, and energy consumption. It can improve smart grids by applying decentralized energy management and data transactions, and by addressing cybersecurity and potential challenges related to scalability and market adoption. Smart grids are affected by blockchain development in different sectors, such as smart contracts and demand response, electric vehicles, IoT technology, energy trading, financial transactions, testbed, and environmental [62]. Below, some practical PED applications that use blockchain are presented:  
* _Peer-to-Peer (P2P) Energy Trading_: Blockchain creates a secure, transparent ledger for energy transactions in local or consumer-centric marketplaces, enables smart contracts to automate buying/selling based on predefined rules, and decreases the need for intermediates [66]. * _Decentralized Energy Management_: An important potential benefit of blockchain lies in its decentralized nature and robust security features [67]. Blockchain supports autonomous coordination of distributed energy resources through smart contracts (energy storage usage during peak hours is automatically shifted to balance the PED load), dynamic pricing models based on supply and demand, and local grid stability and load balancing. Complete decentralization of energy markets can be accomplished thanks to the capability of blockchain to enable cryptocurrency-based financial transactions within the energy industry. As a result, financial transactions will no longer need to be controlled from a single location [67]. * _Energy Data Transparency and Traceability_ of energy monitoring for consumption, production, and emissions data: Blockchain ensures robust records of energy flows,provides audit trails for carbon accounting and compliance, and supports real-time verification and certification of green energy trading [66]. 4. _Secure IoT and Smart Meter Integration:_ PED monitoring relies on IoT sensors and smart meters. Blockchain provides secure data channels and identity management, prevents tampering with device data, and ensures interoperability among devices and systems.