# Day-Ahead Dispatch Model of Electro-Thermal Integrated Energy System with Power to Gas Function
## 4 Simulation Results  
### Example Data  
Figure 4 shows the one-line diagram of an integrated system of a six-bus electric power system and a six-node district heating system, which is used in this study. The heat source of a district heating system is provided by a gas cogeneration unit. In comparison, in a wind farm, the electricity infrastructure has two generators at B81, B82 and B86. The typical output of wind power and daily electric and thermal loads are shown in Figure 5. It represents the basic trend and fluctuation of wind power output, thermal load and electrical load in a day during the winter heating period in China. It can be seen from the diagram that heat and electrical loads have opposite peaks, this is because the ambient temperature is high in the daytime and low in the nighttime. The wind power and electric loads also have opposite peaks pertaining to high wind penetration. Such settings are consistent with those of electric power systems. In order to verify the advantages of the proposed model in improving energy efficiency and energy saving and emission reduction, the day-ahead dispatch model will be simulated in two different operating modes which is conventional in Chinese northern heating periods. The system information with detailed data is provided in [18]. 1. Mode 1: Separate Generation of Heat and Power  
In other words, the gas boilers supply the consumers' heat demand, the wind farm and thermal units supply the consumers' electricity demand. When the integrated network is added to the P2G link, hydrogen produced by the abandoned wind power is injected into the gas network by the hydrogen storage devices. The electric output, heating output and coal consumption should be recorded in two cases of the integrated system with P2G and without P2G. Figure 4: Configuration of the six-bus and six-node integration system. Figure 5: Daily profile for wind power, electric and thermal loads. Based on the results of simulate, the integrated system with HCNG of two modes are analyzed in three aspects:  
1. Heat Addition  
In the utilization of HCNG, the heat addition supplied by hydrogen of Mode 2 is slightly higher than Mode 1 in Figures 6b and 7b. The reason for this is that the power generation of the CHPs cannot be dispatched when they are heating the users based on the principle of pricing electricity based on heat amount. At the same time, the grid capacity of wind power is reduced and the abandoned wind power is increased. Then, through the wind power electrolysis, the amount of hydrogen added to the gas network during each period of time is also increased. 2. Coal Consumption  
For the same mode, the coal consumption of the supply system with P2G is obviously lower in Figure 8 and Table 1. It is shown that the form of energy supply with HCNG is more energy efficient than the form of energy supply with the traditional gas network. The data released by the National Energy Administration shows that the Chinese electricity of abandoned wind electricity in the first half of 2015 was 17 billion 500 million KWh [19; 20]. According to the related literature, the transformation efficiency of wind to hydrogen currently does not exceed 40% [21; 22; 23; 24; 25]. If all of the abandoned wind electricity is used to produce hydrogen, it will get 1 billion 958 million m\({}^{3}\) of hydrogen, which can be converted to 5 billion 414 million m\({}^{3}\) natural gas on an equal heat basis. At the same time, it will also reduce 10 million 210 thousand tons of the carbon dioxide of the combustion emission produced by the same volume of natural gas and save 65 million 740 thousand tons of the standard coal. 3. Energy Utilization  
For the traditional power and heat independent production system, the random fluctuation of wind power causes the grid capacity of wind power to be limited. For the combined power and heat system, the operation principle of the CHP units can also lead to the insufficient capacity of wind power.