Energy savings and CO_2 emission reduction by using geothermal heat pumps

The renewable energy will play significant role in the world primary energy consumption in the future. Geothermal energy is immense with 5 000 EJ/a of technical potential, and geothermal heat pumps (GHPs) are one of the fastest growing applications of renewable energy in the world with annual increases of 10 % and much faster in China. With high coefficient of performance (COP) up to 6, GHPs make efficiency of primary energy more than 240 % with assumed a 40 % of electricity generation efficiency, which means energy savings and CO2 emission reduction. In this paper,the geothermal resources and its utilization are talked about, and GHPs technology was introduced. Due to its high efficiency, there will be energy savings by using GHPs. There is also CO2 emission reduction because of using geothermal heat pumps, which is analyzed in the end.

Reaction Rate Characteristics of SrBr2 Hydration System for Chemical Heat Pump Cooling Mode

Here, we propose a chemical heat pump chiller with a SrBr2 hydration reaction system for utilization of waste heat. The SrBr2 hydration reaction could recover waste heat in low temperatures ranging from 373 K to 353 K, and the system showed good potential in terms of the high cooling thermal-storage density. Previous studies have given little information on the reaction characteristics of the SrBr2 hydration reaction. In this paper, we developed a measuring method for the hydration reaction equilibrium and reaction rate based on the volumetric method. We analyzed the hydration reaction rate with an unreacted-core shell model. In the experiments, the SrBr2 equilibrium temperature observed was equal to the theoretical equilibrium temperature obtained from thermodynamic databases. In addition, the hysteresis gap between the hydration and dehydration values was 2.0 K. Thus, the hysteresis effect was negligible for the chemical heat pump cooling operation. The reaction fraction of the SrBr2 hydration reached 0.7 within 20 s. By analyzing the hydration reaction rate with the unreacted-core shell model, the activation energy value was calculated to be56.6 kJ/mol. The calculation results showed good agreement with those of the experiment as the reaction fraction reached 0.7.

Mathematical model of absorption and hybrid heat pump

Recovering waste heat from industrial processes is bene ficial in order to reduce the primary energy demands and heat pumps can be used to this purpose.Absorption heat pumps are energy-saving and environment-friendly because use working fluids that do not cause ozone depletion and can reduce the global warming emissions.The hybrid heat pump processes combine the conventional vapor-compression and the absorption heat pump cycles.Studies about the simulations and modeling of hybrid heat pumps are few in literature.In this research a mathematical model for single effect absorption and hybrid heat pump is carried out with Chem Cad? 6.0.1.LiBr–H_2O is used as working fluid while electrolytic NRTL and electrolytes latent heat are used as thermodynamic model due to the better results.Binary parameters of activity coef ficients are regressed from experimental vapor pressure data while default constants are used for the solubility expressions.A design of heat pumps is developed and a new modeling of generator is analyzed.The coef ficient of performance of absorption heat pump and hybrid heat pump is equal to 0.7 and 0.83 respectively.For absorption heat pump a sensitivity analysis is carried out to evaluate the effect of temperature and pressure generator,the concentration of Li–Br solution on coef ficient of performance,cooling capacity and working fluid temperature.For hybrid heat pump,the different coef ficients of performance,the primary energy ratio,the generator heat,and the compressor power are analyzed for different values of compressor proportion.Results show that comparing the two systems the hybrid pump allows to save more primary energy,costs and carbon dioxide emissions with respect to absorption heat pump with the increasing of compressor proportion parameter.Future researches should focus on the construction of this heat pumps integrated in chemical processes as a biogas plant or trigeneration systems.

Thermodynamic Simulation of CCP in Air-Cooled Heat Pump Unit with HFCs and CO₂Trans-Critical

The exergy analysis and finite time thermodynamic methods had been employed to analyze the compound condensation process (CCP). It was based on the air-cooling heat pump unit. The cooling capacity of the chiller unit is about 1 kW, and the work refrigerant is R22/R407C/R410A/CO2. The MATLAB/SIMULINK software was employed to build the simulation model. The thermodynamic simulation model is significant for the optimization of parameters of the unit, such as condensation and evaporation temperature and mass flow of the sanitary hot water and size of hot water storage tank. The COP of the CCP of R410A system is about 3% - 5% higher than the CCP of the R22 system, while CCP of the R407C system is a little lower than the CCP of R22 system. And the CCP of CO2 trans-critical system has advantage in the hot supply mode. The simulation method provided a theoretical reference for developing the production of CCP with substitute refrigerant R407C/R410A/CO2.

Low-energy-consumption temperature swing system for CO_(2) capture by combining passive radiative cooling and solar heating

Temperature-swing adsorption(TSA)is an effective technique for CO_(2) capture,but the temperature swing procedure is energy-intensive.Herein,we report a low-energy-consumption system by combining passive radiative cooling and solar heating for the uptake of CO_(2) on commercial activated carbons(CACs).During adsorption,the adsorbents are coated with a layer of hierarchically porous poly(vinylidene fluoride-co-hexafluoropropene)[P(VdF-HFP)HP],which cools the adsorbents to a low temperature under sunlight through radiative cooling.For desorption,CACs with broad absorption of the solar spectrum are exposed to light irradiation for heating.The heating and cooling processes are completely driven by solar energy.Adsorption tests under mimicked sunlight using the CACs show that the performance of this system is comparable to that of the traditional ones.Furthermore,under real sunlight irradiation,the adsorption capacity of the CACs can be well maintained after multiple cycles.The present work may inspire the development of new temperature swing procedures with little energy consumption.

Performance analysis of a novel tobacco-curing system with a solar-assisted heat pump

A novel tobacco-curing system with a solar-assisted heat pump was proposed.The proposed system has various advantages,such as reducing energy consumption and pollutant emissions and enhancing the stability of system operation.The thermal characteristics of the system under different climate conditions were analyzed,and the economic and environmental benefits of different tobacco-curing technologies were compared.Results indicated that the dehydration rate,the mass flux of exhaust air,and the heat load of the novel tobacco-curing system in different months had similar changes with the baking time,and all reached the maximum in the later stage of color fixing.Compared with the power saving rate of a heat pump tobacco-curing system,that of the novel system reached 25.9%-35.1%.The dry leaf curing cost of the novel system was only 0.86-1.06 yuan/kg,which can reduce the cost by more than 60%compared with traditional coal-burning tobacco-curing systems in China.Compared with other parts of the tobacco leaf,the top leaf had the lowest dry leaf curing cost due to its highest mass of dry leaf.The payback period and the annual CO_(2) emission reduction of the novel system were 3.0-3.7 a and 15586 kg,respectively.

Exergo-Environmental Study of a Recent Organic Solar Hybrid Heat Pump

A hybrid heat pump(compression/absorption)with an integrated thermal photovoltaic unit is studied.The considered working fluids are organic mixtures:R245fa/DMAC and R236fa/DMAC,chosen for their low Global Warming Potential.The main objective is the optimization of energy efficiency in order to minimize the environmental impact through the implementation of a sustainable strategy.It is shown that Exergy Analysis itself is a valuable tool in energy integration.Within the imposed framework of minimizing total annual costs,entropy analysis can be instrumental in determining the optimal plant concept,optimizing energy conversion and use,and improving profitability.The present results are discussed under the optimistic hope that they may help to define new energy and environmental policies.

Dynamic Model and Performance of Absorption Heat Pump in Shut-down Process

The dynamic model of LiBr absorption heat pump in shut-down process is established. The simulation results show good agreement with the experiments. The dynamic performance of high-pressure generator, low-pressure generator and heat exchanger are analyzed in detail. The proper shut-down mode of the heat pump is presented,which, in consideration of solution parameters, has a great effect on the possibility of crystallization of some components.

Experimental Evaluation of the Heat Output/Input and Coefficient of Performance Characteristics of a Chemical Heat Pump in the Periodic Operation of CaCl₂Hydration

We herein evaluate the use of a chemical heat pump (CHP) for upgrading waste heat. CaCl2 was used in the system of CHP. We evaluated the heat storage and heat releasing of CHP, and confirmed the practicality from the experimental results. The reactor module employed was an aluminum plate-tube heat exchanger with corrugated fins, and the CaCl2 powder was in the form of a packed bed. Heat storage operation and heat dissipation operation are performed at the same time and supplied to the heat demand destination. At this time, an environmental heat source can be used during the heat radiation operation, and the heat output can release more heat than the heat input during heat storage. The heat discharging and charging characteristics of the reactor module were evaluated experimentally. The coefficient of performance (COP) was calculated for the heat upgrading cycle, and the heat output in the system was determined. A COP of 1.42 and output of 650 W/L, based on the heat exchanger volume, were obtained using a 600 s change time for the heat pump.

Case Studies of Energy Saving and CO₂Reduction by Cogeneration and Heat Pump Systems

This paper describes two case studies: 1) a cogeneration system of a hospital and 2) a heat pump system installed in an aquarium that uses seawater for latent heat storage. The cogeneration system is an autonomous system that combines the generation of electrical, heating, and cooling energies in a hospital. Cogeneration systems can provide simultaneous heating and cooling. No technical obstacles were identified for implementing the cogeneration system. The average ratio between electric and thermal loads in the hospital was suitable for the cogeneration system operation. An analysis performed for a non-optimized cogeneration system predicted large potential for energy savings and CO2 reduction. The heat pump system using a low-temperature unutilized heat source is introduced on a heat source load responsive heat pump system, which combines a load variation responsive heat pump utilizing seawater with a latent heat-storage system (ice and water slurry), using nighttime electric power to level the electric power load. The experimental coefficient of performance (COP) of the proposed heat exchanger from the heat pump system, assisted by using seawater as latent heat storage for cooling, is discussed in detail.

CO_2跨临界(逆)循环的热力学分析

CO2 is a safe natrual refrigerant which had been and will be widely used in air condi-tioning and heat pump systems. The thernodynamic analysis of the CO2 transcritical cycleis presented in this paper. The result shows that the CO2 cycles offers heat recovery benefitas a heat pump system. It is possible that the COP value of CO2 cycle can compete withthose of R22 or R134a if two stage compression system or an expander system are used.

CO_2跨临界循环特性对热泵干燥系统的影响

对CO2跨临界循环的超临界放热特性和运行规律进行了分析,根据这些特性,对其应用于干燥热泵系统进行了探讨,并对蒸发温度、过热度及气体冷却器出口温度对系统除湿率的影响做出分析。研究表明CO2跨临界循环放热段存在大的温度滑移,气体冷却器出口温度低有利于系统运行,这些特点非常适合干燥系统,而且干燥系统除湿率也受到这些特性的影响,系统存在最优运行压力和最佳的蒸发温度与气体冷却器出口温度组合。

CO_2跨临界水——水热泵循环系统的实验研究

在作者设计和建立的实验台上进行了CO2 跨临界水—水热泵多种工况的循环性能实验研究 ,系统运行稳定、调节方便。实验结果表明 ,系统运行时的最大制冷 (热 )系数取决于系统的蒸发温度和气体冷却器出口温度。CO2 跨临界循环热泵较之传统工质热泵具有较大优势 ,尤其是在高温热泵领域。

CO_2跨临界双级压缩采暖热泵理论分析

分析了制约 CO2 跨临界单级循环在采暖热泵中应用的主要因素 ;研究了双级压缩回热循环的可行性 ,对其在两种不同供水温度水平下的应用进行了理论计算和分析 ,并分别和锅炉供热以及 R1 34 a热泵进行了比较 .

CO_2双螺杆压缩膨胀机在热泵空调中的应用

分析了CO2双螺杆压缩膨胀机的优势以及膨胀机和压缩机同轴连接的受力情况。通过分析可以看出,将膨胀机和压缩机做成同轴可以很好地抵消轴向力。并设计了新型的进气装置可以很好地实现CO2热泵空调系统的冬夏季转换,CO2双螺杆压缩膨胀机自身的进排气调节可以取代热泵空调中的四通阀,避免了四通阀的热短路效应和高低压间的泄漏。

CO_2跨临界热泵双级加热热水系统运行参数分析与比较

对单级加热与双级加热两种形式的CO2跨临界循环热泵热水系统进行分析对比,并对CO2跨临界循环热泵双级加热热水系统进行了运行参数的分析.发现双级加热系统有不同于单级加热系统的规律,前者更为灵活,通过增加预热器,还可适当地提高能效比.在实际应用中应根椐使用要求采用不同的热水循环系统和运行参数,使系统达到最佳状态.

CO_2跨临界水源热泵两级供热系统理论比较

在供热系统中 ,需要的水温较高时 ,由于回水温度高而导致CO2 跨临界水源热泵能效比下降。如果降低回水温度 ,就要求不同温度的热水分级利用。CO2 跨临界水源热泵两级供热系统可以实现能量的分级利用。分析对比了 3种形式的CO2 跨临界水源热泵两级供热系统 ,发现它们各有特点 ,可根据不同的使用要求采用适宜的两级系统。

燃气机驱动CO_2跨临界循环热泵系统

以天然气为能源 ,以CO2 为工质的燃气机驱动CO2 跨临界循环热泵系统可以最大限度地降低总有效温室效应指数 ,提高一次能源利用率 ,减小对环境的污染 ,而且其运行费用也低于普通电动热泵 。

Dynamic analysis of heat extraction rate by supercritical carbon dioxide in fractured rock mass based on a thermal-hydraulic-mechanics coupled model

Heat production from geothermal reservoirs is a typical heat transfer process involving a cold working fluid contacting a hot rock formation.Compared to the thermal-physical characteristics of water,supercritical CO_(2)(scCO_(2))has a higher heat storage capacity over a wide temperature-pressure range and may be favored as a heat transfer fluid.Singularly characteristic of scCO_(2)-based heat extraction is that the hydraulic-thermal properties of the scCO_(2) vary dramatically and dynamically with the spatial pressure gradient during unsteady-state flow along fracture.This highly nonlinear behavior presents a challenge in the accurate estimation of heat extraction efficiency in scCO_(2)-based EGS.In this paper,a thermal-h ydraulic-mechanical(THM)coupled model is developed by considering deformation of the fractured reservoir,non-Darcy flow and the varying thermal-physical properties of scCO_(2).The proposed model is validated by matching the modeling temperature distribution with published data.The results show that during continuous injection of scCO_(2),the fracture first widens and then narrows,ultimately reopening over the long term.The sequential fracture deformation behaviors are in response to the combined impacts of mechanical compression and thermally-induced deformation.By controlling the injection parameters of the scCO_(2),it is found that the heat extraction rate is positively correlated to its pore pressure or mass flow rate.The heat extraction rate can be significantly enhanced,when the inlet temperature of scCO_(2) is below its critical temperature.As a result,the heat increment recovered per unit mass of scCO_(2) decreases as the hot rock is gradually cooled.Meanwhile,the heat increment recovered per unit mass of scCO_(2) decreases by increasing the inlet temperature of scCO_(2) or its mass flow rate,but increases as the outlet pressure rises.Furthermore,multi-linear regression indicates that controlling the inlet temperature of the scCO_(2) can significantly improve the thermodynamic efficiency of heat extraction.

Simultaneous CO_(2) capture and thermochemical heat storage by modified carbide slag in coupled calcium looping and CaO/Ca(OH)2 cycles

The simultaneous CO_(2) capture and heat storage performances of the modified carbide slag with byproduct of biodiesel were investigated in the process coupled calcium looping and CaO/Ca(OH)2 thermochemical heat storage using air as the heat transfer fluid.The modified carbide slag with by-product of biodiesel exhibits superior CO_(2) capture and heat storage capacities in the coupled calcium looping and heat storage cycles.The hydration conversion and heat storage density of the modified carbide slag after 30 heat storage cycles are 0.65 mol·mol^(-1) and 1.14 GJ·t^(-1),respectively,which are 1.6 times as high as those of calcined carbide slag.The negative effect of CO_(2) in air as the heat storage fluid on the heat storage capacity of the modified carbide slag is overcome by introducing CO_(2) capture cycles.In addition,the CO_(2) capture reactivity of the modified carbide slag after the multiple calcium looping cycles is enhanced by the introduction of heat storage cycles.By introducing 10 heat storage cycles after the 10th and 15th CO_(2) capture cycles,the CO_(2) capture capacities of the modified carbide slag are subsequently improved by 32%and 43%,respectively.The porous and loose structure of modified carbide slag reduces the diffusion resistances of CO_(2) and steam in the material in the coupled process.The formed CaCO_(3)in the modified carbide slag as a result of air as the heat transfer fluid in heat storage cycles decomposes to regenerate CaO in calcium looping cycles,which improves heat storage capacity.Therefore,the modified carbide slag with by-product of biodiesel seems promising in the coupled calcium looping and CaO/Ca(OH)_(2) heat storage cycles.