# Energy Trading with Electric Vehicles in Smart Campus Parking Lots
## 3 Proposed Market Mechanism  
There are two main parts that are needed in order to enable energy trading in a smart parking lot: a physical energy network and a virtual energy market platform [13]. The physical energy network is required for energy transfer among electric vehicles and the parking lot operator, while the virtual energy market platform is needed to enable a local energy market for energy selling and buying. Communication networks are used to exchange information among different components of the smart parking lot. Figure 2 shows an overview of the proposed energy trading system in a smart parking lot. The main components are input data, collecting bids, auction, declare and notification, energy exchange, and settlement. We assume that each charging station is capable of collecting information regarding the vehicles' arrival time, departure time, and participation in the energy trading market. The parking lot control center monitors the status of all charging stations and coordinates the charging (parking lot-to-vehicles (PL2V)) and discharging (vehicles-to-parking lot (V2 PL)) operations of each station. Different wired/wireless communication technologies could be used for communication between the parking lot control center (PLCC) and charging stations. Table 1 shows an overview of the proposed energy trading in a smart parking lot. \begin{table}
\begin{tabular}{c c} \hline \hline  & **Characteristic** \\ \hline Smart Parking Lot & PL2V and V2 PL \\ Energy Trading Objective & Profit maximization for PLCC \\ Scale & Single parking lot, multiple parking lots \\ Control Type & Centralized solution, decentralized solution \\ Price Model & Time of use (TOU), real-time price (RTP) \\ \hline \hline \end{tabular} PLCC: parking lot control center; PL2V: Parking Lot-to-Vehicles; V2 PL: Vehicles-to-Parking Lot.  
\end{table} 
Table 1: Overview of proposed smart parking lot characteristics. Figure 3 shows the system model of a smart parking lot. The PLCC is responsible for managing the charging of parked electric vehicles based on their status data (arrival time, departure time, state of charge (SOC)). We classified electric vehicles into three different types: seller electric vehicles (SEVs) with an excess of energy in the battery, buyer electric vehicles (BEVs) with lack of energy in the battery, and idle electric vehicles (IEVs). * Seller electric vehicles (SEVs) denoted SEVi, i = 1, 2,..., N. SEVs have extra power and represent energy providers. * Buyer electric vehicles (BEVs) denoted SEVj, j = 1, 2,..., K. BEVs demand power for charging and represent energy consumers. * Idle electric vehicles (IEVs) do not participate in any energy trading activities. In this work, the market mechanism for the smart parking lot was implemented based on the Knapsack Algorithm (KPA) [14] and deployed in the PLCC. The main objective of the PLCC is to coordinate the energy trading among SEVs, BEVs, and PLCC. Each SEV can submit an energy request \(\mathrm{R_{SEVi}}\) for selling energy at time t. \(\mathrm{R_{SEVi}}\) is represented by (\(\mathrm{SEV_{ID}}\), \(\mathrm{SEV_{SA}}\), \(\mathrm{SEV_{SP}}\)) where \(\mathrm{SEV_{ID}}\), \(\mathrm{SEV_{SA}}\), \(\mathrm{SEV_{SP}}\) are the vehicle identification, the amount of energy to be exchanged, and the suggested price of energy, respectively. Also, BEVs request the amount of energy for charging from the PLCC. Each BEV can submit an energy demand request (\(\mathrm{R_{BEVi}}\)) at time t. \(\mathrm{R_{BEVi}}\) is represented by (\(\mathrm{BEV_{ID}}\), \(\mathrm{BEV_{BA}}\), \(\mathrm{BEV_{BP}}\)) where \(\mathrm{BEV_{ID}}\), \(\mathrm{BEV_{BA}}\), \(\mathrm{BEV_{BP}}\) are the vehicle identification, the amount of demand energy for charging, and the offered price of energy, respectively. The PLCC gathers all offer/demand requests and selects a set of electric vehicles to trade with. The main objective of PLCC is to maximize the total profit as  
Figure 2: Overview of the proposed energy trading system in a smart parking lot.