# Highway Microgrid Project Evaluation under Energy Transportation Integration
## 2 Highway Microgrid Evaluation System
### Index Evaluation Comotation
#### 2.2.1 Economic Index
Let the sound pressure level \(L_{P}\) generated by the intensity \(L_{w}\) at the distance noise point \(R\) be expressed as:  
\[L_{P}=L_{w}-20\lg R-11 \tag{5}\]  
For n noise sources in the new energy power station, the noise of all the receiving points is superimposed, and the equivalent value of noise can be expressed as:  
\[L_{PT}=10\lg\left(\sum_{i=1}^{n}10^{0.1L_{Pi}}\right) \tag{6}\]  
\(L_{CN}\) represents the daytime or nighttime environmental noise limits of various functional areas, and the total noise exceeding the standard cost \(C_{n}\) is expressed as:  
\[C_{n}=\sum_{i=1}^{M}(L_{PTi}-L_{CNi})\mu \tag{7}\]  
where \(\mu\) refers to the collection standard of pollution fee for excessive noise stipulated in the Regulations on the Management of the Collection Standard of Pollution Fee; \(M\) stands for the number of months for which noise exceeds the standard. The income of the highway microgrid project mainly includes the income from the selling of electricity of wind turbines and photovoltaic units and the service income from the service area of the charging station. The power generation income includes the power purchase cost saved when photovoltaic power generation is self-used and the power sale income when the surplus power is online. In addition, while waiting at the charging station in the service area, users can also choose to consume at service facilities such as supermarkets and restaurants to obtain service income [27]. 1. Microgrid sale income \[C_{\text{elec}}=\rho_{b}(E_{L,t}-E_{b,t})+\rho_{s}(E_{PV,t}-E_{L,t}+E_{b,t})\] (8) where \(\rho_{b}\), \(\rho_{s}\) are, respectively, the purchase price and the on-grid price of AC fusion microgrid; \(E_{L,t}\), \(E_{b,t}\) are, respectively, the load power consumption and purchased power of AC fusion microgrid in year \(t\). 2. Service income \[C_{Service}=\sum_{q=1}^{m}w_{q}\lambda b_{\text{av}}\beta\] (9) where \(m\) is the number of vehicles working for the charging station in the service area during the cycle; \(w_{q}\) is the number of passengers per vehicle; \(\lambda\) and \(b_{\text{av}}\) are per capita consumption probability and amount, respectively; \(\beta\) is the profit factor. The economic index of the highway microgrid project needs to forecast and analyze the profitability and return on investment of the project. The common financial evaluation index is divided into dynamic and static indices. The static index ignores the influence of time value, while the highway microgrid project has a large investment and a long life cycle, so it is not suitable to use static indicators. Therefore, this paper uses a dynamic index to evaluate the economy of the highway microgrid project [28]. 1. NPV The net present value considers the time value of funds. It can be expressed by the following formula: \[NPV(i_{0})=\sum\limits_{t=0}^{N_{S}}{(CI-CO)}_{t}(1+i_{0})^{-t}\] (10) where \(CI\) is income, \(CO\) is cost; \(i_{0}\) is discount rate; \(N_{S}\) is operation cycle. When \(NPV\geq 0\), the project is feasible; when \(NPV<0\), the project is not feasible. 2. IRR Internal rate of return (IRR) is an important index of financial evaluation, reflecting the investment utilization efficiency of a project. The larger the value of the internal rate of return, the stronger the profitability of the scheme. \[\sum\limits_{t=0}^{N_{S}}{(CI-CO)}_{t}(1+IRR)^{-t}=0\] (11)  
2.2.2. Technical Index 1. Energy use efficiency [29] \[\alpha=\frac{\sum\limits_{i=1}^{N_{N_{W}}}{\sum\limits_{t=1}^{T}[P(t)-P_{a}(t )]}}{\sum\limits_{i=1}^{N_{W}}{\sum\limits_{t=1}^{T}P(t)}}\] (12) where \(P(t)\) is the power generation output of the new energy power station; \(P_{a}(t)\) is the new energy abandoned power; \(N_{W}\) is the total number of new energy power stations. 2. Power supply reliability In this paper, power supply reliability is characterized by system power shortage expectation. It represents the accumulated amount of power lost because the output power is less than the load power requirement in the statistical period.