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As a means to adjust the temperature of the thermal zones in buildings, building thermal mass is regarded as one of the essential sources of energy flexibility. It is still challenging to quantify the energy flexibility of passive thermal mass, making it oppugning to use thermal mass for buildings’ demand response (DR). A method to accurately quantify the energy flexibility from heating, ventilation, and air conditioning systems (HVAC) is important for buildings to participate in DR projects. This paper proposes a novel data-driven model to quantify HVAC’s electrical demand under dynamic global temperature adjustment. The Markov chain is first used to implement an effective sampling method to produce a global temperature resetting schedule representing different temperature resetting. Next, EnergyPlus evaluates the HVAC electrical demand under the various temperature reset scenarios. In the end, the LightGBM algorithm is used to develop the data-driven model. Having validated the proposed model, the case study was conducted in a DOE reference office building for EnergyPlus. Results demonstrate that the Markov chain outperforms the probabilistic method when sampling temperature setpoint schedules. In the future, the proposed data-driven model can be used to evaluate the flexibility capacity of an energy management system in grid-integrated buildings.

The global utilization of RES, particularly geothermal energy, is rising and the inefficient nature of geothermal cycles necessitates recovering lost heat. This research proposes a combined power generation cycle that simulates integrating a trans-critical CO2 cycle with a single flash geothermal cycle, utilizing the engineering equation solver. The study contrasts the system's performance between two operating states: "Without Economizer" and "With Economizer". The investigation analyzes the impact of an economizer on key output parameters, including energy efficiency, exergy efficiency, and net power output. In the "With Economizer" operating state, the net power output experiences a noticeable increase from 201.5 kW to 204.7 kW, resulting in a 1.58% enhancement in the performance of the "With Economizer" system. The energy efficiency metric demonstrates a corresponding improvement, rising by 1.55% from 3.28% in the "Without Economizer" system to 3.331% in the "With Economizer" system, aligning with the principles of the First law of thermodynamics. Furthermore, the energy efficiency, expressed as a percentage of energy units, shows an increase from 16.3% in the "Without Economizer" system to 16.56% in the "With Economizer" system, representing a 1.595% improvement based on the Second law of thermodynamics or exergy. Regarding cost analysis, the study identifies the optimal separator pressure value for the system without an economizer, equivalent to 23. This configuration achieves a total cost rate of 01 $ per GJ. Conversely, in the system with an economizer, the optimal pressure value for the production cost rate is 322.4 kPa, resulting in a cost rate of 23.57 $ per GJ. [ABSTRACT FROM AUTHOR]

At temperatures below 60 °C, the best way to use geothermal sources for heating is to use heat pumps. A heat pump can provide air conditioning for a residential, commercial, etc., all year round by heating in winter and cooling in summer using a low temperature source. Also, a heat pump can be used for water distillation through evaporation. The ground source heat pump with a high COP and low temperature thermal energy sources is one of the best technologies for using RES. In the present study, the effects of changing ambient temperature and soil temperature on a heat pump's overall COP and energy efficiency are investigated using a simulated geothermal heat pump with an economizer. The system's thermodynamic simulation is first performed in the engineering equation solver software for R134a and R513a working fluids. The exergy destruction of different components for both working fluids was calculated and displayed as a figure. The COP of the heat pump for R134a working fluid is equal to 3.916, equal to 3.729 for R513a working fluid, which indicates that R134a fluid has about 5% better performance. The COP of the system for R134a working fluid is equal to 3.662, which is equal to 3.504 for R513a working fluid, which indicates that R134a fluid has about 4.5% better performance. [ABSTRACT FROM AUTHOR]