Energy and exergy analysis of fossil plant and heat pump building heating system at two different dead-state temperatures (original) (raw)
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Renewable Energy, 2010
The energy and exergy flow for a space heating systems of a typical residential building of natural ventilation system with different heat generation plants have been modeled and compared. The aim of this comparison is to demonstrate which system leads to an efficient conversion and supply of energy/ exergy within a building system. The analysis of a fossil plant heating system has been done with a typical building simulation software IDA-ICE. A zone model of a building with natural ventilation is considered and heat is being supplied by condensing boiler. The same zone model is applied for other cases of building heating systems where power generation plants are considered as ground and air source heat pumps at different operating conditions. Since there is no inbuilt simulation model for heat pumps in IDA-ICE, different COP curves of the earlier studies of heat pumps are taken into account for the evaluation of the heat pump input and output energy. The outcome of the energy and exergy flow analysis revealed that the ground source heat pump heating system is better than air source heat pump or conventional heating system. The realistic and efficient system in this study ''ground source heat pump with condenser inlet temperature 30 C and varying evaporator inlet temperature'' has roughly 25% less demand of absolute primary energy and exergy whereas about 50% high overall primary coefficient of performance and overall primary exergy efficiency than base case (conventional system). The consequence of low absolute energy and exergy demands and high efficiencies lead to a sustainable building heating system.
Exergy analysis of a hybrid ground-source heat pump system
Applied Energy
In contrast to energy analysis, the analysis of exergy allows the evaluation of the quality of different energy flows and enables a comprehensive assessment of inefficiencies within a system and its individual components by accounting for exergy consumption. While exergy analysis methods have been applied to a variety of conventional and renewable energy supply systems, there is still a lack of knowledge regarding the exergy flows and exergy efficiency of hybrid ground-source heat pump systems with a supplementary boiler. In this study, we develop a thermodynamic model for each subsystem in a hybrid heating and cooling system of an existing building by applying the concept of cool and warm exergy. A comparison of the exergy consumption of the hybrid system in heating and cooling reveals that there are significant differences regarding the components that attribute most to the overall exergy consumption in the system. Due to these differences the true exergy performance of the system in heating mode (~30%) is twice as high as for cooling mode (~15%), while the natural exergy performance is considerably better in cooling mode (~26% to ~3%). Potential measures to enhance the exergy performance based on changes in the operational settings of the system and the improvement of the building envelope were found to have a more significant effect on heating performance than on cooling performance. In general, measures that affect the amount of thermal energy delivered by the system appear to be more effective than changes to the operational settings of energy supply systems.
Abstract-Energy and Exergy Analyses of Ground Source Heat Pump System in a Hotel
One of the most fundamental requirements and the driving force of the economic and social development of countries is energy. Energy sources must be reliable, continuous, clean and cheap. There have been intensive efforts for establishing a bridge between the energy demand and alternative energy sources in recent years. The increasing need for energy in tourism causes the increase in the cost of energy expenditures. For this reason, tourism operators benefit from alternative energy sources in order to reduce energy cost as well as energy saving. In this study, it is aimed to analyse the energy and exergy efficiencies of a ground source heat pump (GSHP) system. These analyses generated some compelling results as expected because of the use of environmentally friendly energy sources. In numerical calculations and graphics EES (Equation Engineering Solver) software are used. The results show that the COP of GSHP system is 3.683 while the exergy efficiency is 66.49%. Additionally, parametric studies, including the thermodynamic performance of the system and its components, have been conducted by the change in some operating conditions, as variety of the ambient temperature changes from 290 K to 330 K.
Advanced exergetic analysis of a heat pump providing space heating in built environment
Energetika, 2017
In addition to conventional exergy-based methods, advanced exergetic analyses consider the interactions among components of the energy-conversion system and the real potential for improving each system component. The paper demonstrates the results of application of a detailed advanced exergetic analysis to a wastewater source heat pump providing space heating in the built environment. In order to determine thermodynamic parameters of the refrigeration vapour compression cycle in different operating modes, the simulation model has been used. The analysis includes splitting the exergy destruction within each component of a heat pump into unavoidable, avoidable, endogenous and exogenous parts as well as detailed splitting of the avoidable exogenous exergy destruction. Besides, variabilities of heating demands of a building within both the chosen heating season and also from year to year are taken into account. Distribution of the split exergy destructions during different periods of time is also presented for the analysed cases of the heat pump and built environment. It is shown that in the investigated system only about 50% of the total annual destruction in components of the heat pump can be avoided. About 30…40% of this avoidable thermodynamic inefficiency is caused by interactions among components. Based on the applied advanced exergetic analysis it is possible to receive more precise and useful information for better understanding and improving the design and operation of the analysed energy-conversion system.
Applied Energy, 2009
This paper presents a comprehensive exergy analysis of three circuits and whole system of a ground-source heat pump (GSHP) for both building heating and cooling modes. The purpose is to search out the key potential energy saving components. The analytical formulae of exergy loss, exergy efficiency, exergy loss ratio, exergy loss coefficient and thermodynamic perfect degree are derived, respectively. The results show that these exergy indexes should be used integratively, and in the whole system the location of maximum exergy loss ratio is the compressor, while the location of minimum exergy efficiency and thermodynamic perfect degree is the ground heat exchanger, so that the compressor and the ground heat exchanger should be primarily improved. The results also indicate that the exergy loss of a GSHP system for building heating mode is bigger than that of cooling mode, and the exergy efficiency of a whole GSHP system is obviously lower than those of its components for both building heating and cooling modes. Therefore, a comprehensive exergy analysis of a GSHP should be paid more attention to. The results may provide guidelines for the design and optimization of GSHP systems.
Application of Exergy Analysis to Heat-Pump System Evaluation with Actual Operating Data
2015
The exergy analysis based on actual operating data of a heat pump system is carried out in this study. After making the variable-frequency transformation of compressor and water pumps together with the temperature adjustment of child water, the exergy efficiency of the system increases from 26.4% to 33.8%; the net power consumption rate per unit exergy output rate, the rate of exergy consumed in the refrigeration cycle per unit exergy output rate, and the rate of exergy consumed in the chilled water circuit per unit exergy output rate decrease by 27.6%, 29.1%, and 72.1%, respectively.
Exergy Analysis of a Ground Source Heat Pump System for Cold Climatic Condition of Sivas, Turkey
Transactions of Famena, 2021
In the present study, exergy analysis of a ground source heat pump (GSHP) is performed. For this purpose, a horizontal type GSHP test system is installed at Sivas Cumhuriyet University in Sivas Province. GSHP system consists of three main circuits. These are the ground heat exchanger (GHE), the heat pump (HP) and the heating circuit. The temperatures and pressures are measured at the various points of the system. Besides, the mass flow rate of the working fluid circulating in the GHE, heat pump and heat circuit are measured. In addition, power consumption of the compressor and the pumps are measured. Measured data were recorded every minute. The test data used in the calculations are related to the coldest day, December 18, 2016. Exergy loss, exergy efficiency, exergy loss ratio and thermodynamic perfect degree for each element of the system are computed. Exergy efficiency and thermodynamic perfect degree of the system are calculated as 0.27 and 0.86 respectively.
Energy Procedia, 2017
District heating networks are commonly addressed in the literature as one of the most effective solutions for decreasing the greenhouse gas emissions from the building sector. These systems require high investments which are returned through the heat sales. Due to the changed climate conditions and building renovation policies, heat demand in the future could decrease, prolonging the investment return period. The main scope of this paper is to assess the feasibility of using the heat demand-outdoor temperature function for heat demand forecast. The district of Alvalade, located in Lisbon (Portugal), was used as a case study. The district is consisted of 665 buildings that vary in both construction period and typology. Three weather scenarios (low, medium, high) and three district renovation scenarios were developed (shallow, intermediate, deep). To estimate the error, obtained heat demand values were compared with results from a dynamic heat demand model, previously developed and validated by the authors. The results showed that when only weather change is considered, the margin of error could be acceptable for some applications (the error in annual demand was lower than 20% for all weather scenarios considered). However, after introducing renovation scenarios, the error value increased up to 59.5% (depending on the weather and renovation scenarios combination considered). The value of slope coefficient increased on average within the range of 3.8% up to 8% per decade, that corresponds to the decrease in the number of heating hours of 22-139h during the heating season (depending on the combination of weather and renovation scenarios considered). On the other hand, function intercept increased for 7.8-12.7% per decade (depending on the coupled scenarios). The values suggested could be used to modify the function parameters for the scenarios considered, and improve the accuracy of heat demand estimations.
Exergy Analysis of Building Heating with a Groundwater Source Heat Pump
Proceedings of the 51st International HVAC&R Congress and Exhibition, 2020
The paper presents an exergy analysis of the groundwater heat pump operation for theneeds of building heat-ing. The analysis was conducted on a monthly basis, given the dependence of exergy on the changing state of the envi-ronment. Changes inheating coefficient and exergy efficiencyof thegeothermal heat pumpheating systemdepending onthe influentialparameters wereanalyzed: groundwater temperature fromthe pumping well, changes in the ground-water temperature on the heat pump evaporatorand water temperature inthe heating system.The obtained results provide insight into thermodynamic indicators of heat pump operation depending on the groundwater temperature and the operation mode of the building heating system. The conducted analysis provides guidelines for the design and opti-mization of heat pumps that work with groundwater as a heat source.
Performances of heat pump systems as users of renewable energy for building heating/cooling
WSEAS Transactions on Heat and Mass Transfer
The heat pumps are alternative heating/cooling systems more energy efficiency and unless pollutant in comparison with classical systems (liquid or gas fuel boiler). A large number of heat pump systems have been used in residential and commercial buildings throughout the world due to the attractive advantages of high energy and environmental performances. This paper presents the economic, energy and environmental performance criteria which show the opportunity to implement a heat pump in a heating/cooling system. A computational model of annual energy consumption for an air-to-water heat pump based on the degreeday method and the bin method implemented in a computer program is developed. In addition, from a case study a comparative economical analysis of heating solutions for a building is performed and the energy and economic advantages of building heating solution with a water-to-water heat pump are reported. Finally, the renewable energy sources contribution from heat pump sales ...