## 3 Blockchain-Based P2P Energy Trading Model
The money exchange layer ensures secure and transparent financial transactions between parties involved in energy trading. On the other hand, the energy exchange layer focuses on the actual energy exchange between producers and consumers. It involves listing available energy for sale by producers and selecting and purchasing energy by consumers. In this context, smart contracts govern the terms of energy transactions, including quantity, price, and timing. This layer ensures efficient and transparent energy transactions, allowing producers to monetize excess energy and consumers to access clean energy sources. Additionally, renewable energy certificates (RECs) or other verification mechanisms may be used to ensure the authenticity and sustainability of traded energy. Hence, the money exchange layer manages the financial transactions associated with P2P energy trading, while the energy exchange layer facilitates actual energy exchange between participants. These layers enable decentralized, transparent, and efficient energy trading while ensuring trust and security through blockchain technology (Figure 3). Moreover, the blockchain's decentralized nature ensures transparency and security by recording all transactions across multiple nodes in the network. This eliminates the need for intermediaries and reduces the risk of fraud. Additionally, mechanisms for consumers and producers to leave feedback and ratings, based on their experiences, can be integrated  
Figure 3: Blockchain-based P2P energy trading model. to help build trust within the P2P energy trading community. This article, introducing a new blockchain-based P2P financing mechanism for DERs, offers substantial added value to renewable energy investment and deployment. By proposing an innovative billing approach explicitly tailored to DERs, this article addresses critical shortfalls in current billing mechanisms, thus providing an opportunity to overcome the traditional barriers associated with funding DER projects, such as wasted excess energy, tariffs monopoly, and fair compensation for the time of injection of energy back to the grid. On the other hand, blockchain-based P2P energy trading can solve multidirectional billing. Today's energy billing systems are designed for unidirectional or at most bidirectional energy transactions. Thus, there is a need to develop an automatic decentralized energy trading system that can automatically collect energy consumption, offer a user-centric approach, and ensure a simple settlement for energy transactions in a multidirectional way. Furthermore, current billing systems are based on the Point-of-Delivery (PoD) concept, which means that the bill is issued per meter at a specific location where energy is delivered and not per end-user. Conversely, an aggregated bill per customer refers to a billing arrangement where multiple premises owned by the same customer are grouped together, and their energy consumption is aggregated for billing purposes. The aggregated bill per customer simplifies billing administration and can be fairer than a PoD billing in conditions where an increasing block rate billing structure is used, or demand side management (DSM) programs are applied. Moreover, the current data collection, processing, and financial settlement processes are highly inefficient and error-prone, resulting in significant time delays in value settlement and the need for costly reconciliation processes. Billing constitutes 5% to 15% of retailers' total operating costs. Blockchain technology can be the answer for an aggregated efficient, transparent, immune to tampering, and immutable billing system.