Analysis of fuel economy of small energy complex schemes based on gas turbine and wind-driven power plants

Here the energy complex is considered, representing a combination of gas turbine and wind power plants. The combination of plants that operate on different types of fuel (renewable and organic) reduces fuel consumption in a gas turbine installation. Four schemes are described and a comparative analysis of the fuel economy of each scheme is compared with the separate production of electric energy at a conventional thermal power station. For this, a mathematical model for calculating the energy characteristics was developed. The analysis revealed that the energy complex, including a gas turbine without regeneration, a current converter, and a peak boiler, has the greatest cost-effectiveness.

. The diagram of the energy complex using wind energy for heating air in front of the gas turbine combustion chamber. 1gas-turbine compressor; 2regenerative heat exchanger; 3electric heaters for air; 4combustion can; 5gas turbine; 6electric power generator; 7chimney slide valve; 8exhaustheat boiler; 9peak boiler; 10network pump; 11wind-driven power-plant.

Figure 2.
The diagram of an energy complex using WDPP to supply electricity to consumers. 1gas-turbine compressor; 2regenerative heat exchanger; 3combustion can; 4gas turbine; 5chimney slide valve; 6electric power generator; 7exhaust-heat boiler; 8peak boiler; 9network pump; 10wind-driven power-plant; 11current converter. Figure 3. The diagram of an energy complex with electric batteries. 1gas-turbine compressor; 2regenerative heat exchanger; 3combustion can; 4gas turbine; 5chimney slide valve; 6electric power generator; 7exhaust-heat boiler; 8peak boiler; 9network pump; 10wind-driven power-plant; 11electrical accumulator; 12current converter 1gas-turbine compressor; 2combustion can; 3gas turbine; 4electric power generator; 5wind-driven power-plant, 6current converter; 7exhaust-heat boiler; 8peak boiler; 9network pump The difference between scheme 4 and those discussed above is the use of GTU without regenerative air heating. Reducing the heat load of the consumer (in the summer) leads to a partial emission of combustion products after gas turbine without utilization in a exhaust-heat boiler. The WDPP works in parallel with the GTU analogous to scheme 2.
Despite the knownness of these schemes, no comparative analysis of their fuel efficiency was reported in the literature. Moreover, it is necessary to develop a mathematical model of the energy complex functioning to assess their quantitative parameters, which was the subject of the current study.
The thermal economic efficiency of schemes for a given electrical and thermal load of the consumer can be determined from the amount of fuel consumption by the energy complex or relative fuel economy. The latter is determined in comparison with the separate production of electric energy at a conventional thermal power station (CTPS) and a local boiler house, taking into account the losses during the transportation of electricity.
The expression of relative fuel economy will be as follows, % . . . .
where .. , BBannual fuel consumption of GTU and PB, KgCE/year. In the considered schemes, wind power generation varies depending on the wind speed in the daily and annual periods. Therefore, the gas turbine provides the required daily production of electrical energy. The daily electric power generation of wind turbines in the j-month is determined based on hourly multi-year wind speeds and characteristics of the wind-driven power plant, kWh/day. In the diagrams (Fig. 1,2,3), the regenerator is switched off in winter to maximize the displacement of the heat load of the peak boiler. With a decrease in the load during the summer period, the GTU was calculated with a regenerator. Electric efficiency factor, fuel consumption, and the amount of utilized heat of GTU were determined from the calculation of the thermodynamic cycle performed in [3]. The calculations of the considered schemes were performed with the following initial data: the nominal electrical power of the WDPP is 1000 kW, the maximum power of the consumer is 5000 kW, the estimated thermal load of the consumer is 17500 kW, the location is the Middle Volga region. The daily consumption of electric energy for the annual period varied in the range of 61500-76800 kWh/day. As battery devices in scheme 3, we considered lithium-ion batteries with an electrical efficiency . batt  = 0.9, discharge depth  = 0.2, and current сonverter efficiency factor CC  = 0.95 [4,5]. The calculation results of the energy characteristics of energy complexes are given in tables 1,2.  According to the analysis of the results shown in tables 1 and 2, in some months the amount of generated heat energy by the exhaust-heat boiler of GTU exceeds the load of consumers. In this case, gas turbines operate with a partial release of combustion products without utilization. Based on the calculations of the scheme options daily parameters, we determined the monthly and annual characteristics of energy flows and fuel consumption. Fuel consumptions of gas turbines, PBs, and energy complex are given in table 3. The difference between the obtained costs of the considered options does not exceed 3%, which reveals their almost similar fuel economy. The efficiency of energy complex schemes comparing with a separate power supply scheme was determined using combined cycle gas turbine (CCGT) and steam turbine (STP) plants at conventional thermal power station (CTPS) with an efficiency factor of 0.55 and 0.4, an electric power transport efficiency factor of 0.9, a local boiler house efficiency factor of 0.92. The calculations according to expressions (1) and (2) are shown in table 4. According to the obtained results, the greatest relative fuel economy (6.2-18.1%) is achieved for scheme 4. It includes a GTU without regeneration and a wind turbine with a current converter, working