| With the development of social society and the improvement of living standards, the energy demand in China sharply increases and the gap between energy consumption and energy production becomes even larger. Moreover, the coal-dominated energy structure in China has a seriously harmful influence on environment. Building energy consumption plays a significant role in the total energy consumption. The traditional stand-alone production of cooling, heating and power mode is insufficient, whereas the distributed combined cooling, heating and power(CCHP) realizes the cascade utilization of energy and reduces the long distance transportation. Therefore, the CCHP system is sufficient, economic and environmentally friendly to relieve the electric power supply, and it is apt to balance the energy between different seasons, which is beneficial to the energy safety.Based on the ground source heat pump(GSHP) and thermal energy storage(TES), three kinds of CCHP systems are put forward and studied in this paper. The theoretical analysis, numerical simulation and experimental study are used to design the CCHP system and analyze the operational performances. Furthermore, the hourly operation strategies of the CCHP system under different heating or cooling loads are also investigated. On the basis of the GSHP, TES, and the paralleling operation of the generator and the public electric supply network, an experimental system is established. The operational performance of the ground heat exchangers and the GSHPs are measures and compared. Finally, the economic and environmental performances of the CCHP system are evaluated based on the actual operation data ascribed from a real CCHP system. The research contents are closely integrated with the practical work of the author, and the main conclusions of this paper can be drawn as follows:(1) The TES technology can effectively reduce the installed capacity under the rated design condition. Taken the CCHP system based on GSHP, TES and the paralleling operation mode of generator and public electric network as an example, TES not only reduces by 15.27% of the total installed cooling capacity and 37.54% of the total installed heating capacity of the CCHP system, but also evidently decreases the operation cost about 6.48×104 Yuan per year to achieve a good economic benefit.(2) The basic electric load is satisfied by the internal combustion engine and the insufficient is met by the public electric network, which reduces the installed capacity of the internal combustion engine and leads to an efficient operation of the CCHP system.(3) The operation strategy should be oriented with the hourly system load due to the transient variation of the outdoor climate parameters, and the optimal hourly operation strategy has been obtained. When the system load is lower than the rated load, the thermal energy released by the storage tank should be used to offset the insufficient section of the cooling or heating load.(4) For the system load lower than the installed capacity, the thermal energy released by the storage tank should be used as soon as possible in order to reduce the thermal energy loss during the storage period. Moreover, when the system load is much lower than the installed capacity, the thermal energy released by the storage tank can totally meet the cooling or heating load demand.(5) As a result of the difference of the installation location and the long-term operation under part loads, the operation status of the ground heat exchangers are different from each other. The circulating water temperature for the ground side tends to increase after restarting, which is because of the accumulation of the thermal heat. The maximal supply temperature of the circulating water for the ground side is no more than 30℃, which suggests that the heat dissipation performance of the ground heat exchanger is superior to the cooling tower.(6) During the operation under the working condition of cooling and heating, the CCHP system can be adjusted in order to meet the cooling or heating load of the building. The thermal energy released by the storage tank is used to compensate the other equipment while the load reaches or approaches the rated design conditions. Moreover, for the initial and later stage of the cooling and heating seasons, the thermal energy released by the storage tank should be used as soon as possible to reduce the thermal loss, thereby decreasing the operational cost of the CCHP system. The COP of the GSHP under the thermal energy storage in winter is about 2.78, which is lower than the design value of 3.49. The COP of the GSHP in summer is about 6.60, which is 0.3 higher than that under the thermal storage.(7) The TES can be popularized in engineering applications for the places where the step tariff is implemented. According to the statistical data, the annual electricity energy production of the CCHP system is about 4.67×106 kW?h, which can replace 1630 tons of the standard coal and save 121 tons of the standard coal if the standard coal consumption of the thermal power generating unit is 310g/kW?h and the power transmission loss is 8%.(8) The exhaust heat recovered reaches 1.04×107 MJ for heating. The CCHP can save 667 tons of the standard coal. The natural gas consumed by the CCHP system amounts to 1.20×106 m3, which can replace 1883 tons of the standard coal. Moreover, one ton of the smoke dust, 2000 tons of the CO2, and 32 tons of the SO2 will be reduced to discharge. |
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