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[en] Highlights: • A CCHP system integrated with biomass gasification was optimized. • The optimization was based on life-cycle assessment. • The optimization involved energetic, economic, and environmental aspects. • The overall-performance criterion was obtained with TOPSIS. - Abstract: A multi-criteria optimization for a biomass gasification-integrated combined cooling, heating, and power (CCHP) system based on life-cycle assessment is carried out. The criteria comprise primary energy saving ratio (PESR), total cost saving ratio (TCSR), and CO2 emission reduction ratio (CERR). The overall-performance criterion, Cl, is obtained with Technique for Order of Preference by Similarity to Ideal Solutions (TOPSIS). Results show that the Cl reaches its maximum when the nominal electric output is 1572.8 kW, the biomass feedstock type is wood pellet, and the operation strategy is following the electric load (FEL). The PESR, TCSR, CERR, and Cl are 0.101, 0.271, 0.498, and 0.867, respectively. By comparing with reference systems, it is found that in FEL mode, the system is improved because of higher energy utilization efficiency and better use of economic and environmental advantages of biomass. In following the thermal load (FTL) mode, economic performance is compromised for optimal overall performance. Sensitivity analysis is carried out to find out the effect of variation of various parameters on optimization results. It is found that the variation of a single-aspect parameter could affect the system performance on all aspects. The variation of primary energy consumption per unit electricity from the grid (pecen,g) has the greatest effect on optimization results. The corresponding variation ranges of PESR, TCSR, and CERR owing to its variation are from −0.063/0.231/0.473 to 0.284/0.295/0.624 and from −0.029/0.101/0.314 to 0.194/0.123/0.379 in FEL and FTL modes.
[en] Highlights: • An innovative sorption system is proposed to reduce nitrogen oxides emission. • Nanoparticle of carbon coated aluminum plays dual roles in the beginning and end of this system. • The lowest annual required mass of composite sorbent is one quarter of that of urea solution. • Cost of sorption SCR system by using carbon coated aluminum is much lower than that of adblue. - Abstract: A novel sorption system is proposed to reduce nitrogen oxides (NOx) emission, which is regarded as an alternative solution to conventional urea selective catalytic reduction (SCR) technology. Nanoparticle, i.e. carbon coated aluminum (Al@C) plays dual roles at the beginning and end of this system. One is used to prepare novel fuel blend, which is expected to reduce NOx emission due to low fuel consumption. The other is selected for developing composite sorbent for ammonia storage reactor. NOx emission of a diesel engine is tested in terms of various fuel blends. Based on these testing results, working performance of novel sorption SCR system is evaluated. It is indicated that the lowest annual required mass of composite SrCl2 with Al@C is about 98 kg, which is one quarter of urea solution. Comparably, the highest annual required volume of urea solution is 25.6% higher than that of composite SrCl2 with Al@C. Annual required mass ranges from 98 kg to 475 kg whereas annual required volume is in the range from 243 L to 446 L. Feasibility of novel sorption SCR system is further verified, which reveals vast potentials for reducing NOx emission in terms of conversion efficiency and cost.
[en] Highlights: • A sorption thermal energy storage device for domestic heating is presented. • The new design scenario with valve-less adsorber and separate reservoir is adopted. • The newly developed composite sorbent of zeolite 13X/MgSO4/ENG-TSA is used. • The temperature lift is 65–69 °C at 25 °C adsorption and evaporating temperatures. • The impregnated MgSO4 dramatically accelerates the temperature rising rate. - Abstract: A sorption thermal energy storage (TES) device for domestic heating is presented in this article. The TES device adopts the new design scenario with valve-less adsorber and separate reservoir to eliminate the large-diameter vacuum valve for vapor flow, which decreases the cost, reduces the vapor flow resistance, and improves the system reliability. The device is charged by electric heater, which can add much flexibility to the building energy system as well as contribute to the valley filling and peak shaving from the demand side management. The newly developed composite sorbent of zeolite 13X/MgSO4/ENG-TSA (expanded natural graphite treated with sulfuric acid) with the salt mass fraction of 15% in the zeolite 13X/MgSO4 mixture is tested and used in the TES device (denoted as XM15/ENG-TSA). Experimental results show that the TES device with XM15/ENG-TSA has the energy storage density of 120.3 kWh m−3 at 250 °C charging temperature and 25–90 °C discharging temperature. The temperature lift is as high as 65–69 °C under the adsorption and evaporating temperatures of 25 °C. The impregnated MgSO4 dramatically improves the temperature rising rate during the adsorption heat recovery process, but the specific energy storage capacity of XM15/ENG-TSA is similar to that of zeolite 13X/ENG-TSA. The effect of the impregnated MgSO4 suggests that MgSO4 can be used for low-temperature TES to relieve the self-hindrance of the hydration reaction.
[en] Highlights: • Study on boundary conditions of five kinds of adsorption heat pumps is presented. • Feasibility and economic studies under various working conditions were made. • Suggested ranges of driving and cooling temperatures are given for economic use. - Abstract: The objectives of this paper are to analyze adsorption heat pump (AHP) systems using different working pairs such as silica gel/water, zeolite/water, SAPO-34/water, FAPO-34/water and activated carbon/ammonia, and to carry out their boundary conditions. According to the Clapeyron diagram, adsorption equilibrium equations and energy balance equations, feasibility and economic studies under various working conditions are made. Silica gel/water, SAPO-34/water and FAPO-34/water AHPs can feasibly operate for space heating and domestic hot water. Beyond that, zeolite/water and activated carbon/ammonia AHPs can even feasibly operate for heating network or industrial heating/preheating. However, ranges of economic operation are much stricter than that of feasible operation. Silica gel/water, SAPO-34/water and FAPO-34/water AHPs are not convenient for cold winter except zeolite/water and activated carbon/ammonia AHPs. Activated carbon/ammonia AHP even can economically operate in the cold winter with −15 °C ambient temperature. Floor heating is the most convenient technique for silica gel/water, SAPO-34/water and FAPO-34/water AHPs. Zeolite/water and activated carbon/ammonia AHPs require more than 130 °C and more than 140 °C driving source for economic use, respectively. The sequence according to the value of COPH is as follows: silica gel/water, FAPO-34/water, SAPO-34/water, zeolite/water and activated carbon/ammonia AHPs.
[en] Highlights: • Solid sorption heat pipe (SSHP) with composite NaBr-NH_3 is proposed for continuous heat transfer. • Both vertical and horizontal SSHPs are investigated. • SSHP features non-isothermal heat transfer performance at sorbent and condenser sections. • The highest radial heat flux in vertical and horizontal SSHPs is 22.1 and 12.4 kW/m"2, respectively. • Both SSHPs have axial heat flux higher than 400 kW/m"2. - Abstract: A novel type solid sorption heat pipe (SSHP) is developed for continuous heat transfer. In contrast to conventional heat pipe (HP), SSHP utilizes the composite sorbent-sorbate as working media to replace the wick structure inside HP. Such a technology is expected to alleviate the heat transfer limits of conventional HP. NaBr is chosen as the sorbent, and the expanded natural graphite treated with sulfuric acid serves as the matrix. A certain molar amount of the sorbate (NH_3) is complexed with the composite sorbent. The desorption, condensation and chemisorption processes of NaBr-NH_3 working pairs are investigated for both vertical and horizontal placed SSHP. The results show that the desorption process of NaBr-NH_3 solid-gas reaction can be carried out while the heating temperature reaches up to 60 °C or above. The highest radial heat flux in both vertical and horizontal placed SSHP is around 22.1 and 12.4 kW/m"2, respectively, while the axial heat flux for both SSHPs is not less than 400 kW/m"2. It can be concluded that the SSHP is characterized by the non-isothermal heat transfer performance and verified to be available for continuous heat transfer. The vertical SSHP has a better overall heat transfer performance than horizontal SSHP under the same condition and NaBr-NH_3 working pairs applied in SSHP is suitable for low-grade thermal energy transfer above 60 °C.
[en] Highlights: • A small-scale pumpless Organic Rankine Cycle (ORC) system is established. • The maximum power output is 232 W when the hot water inlet temperature is 95 °C. • The highest energy and exergy efficiency are 2.4% and 13.7%. • Pumpless ORC may become one alternative solution to low grade heat utilization. - Abstract: A small-scale pumpless Organic Rankine Cycle (ORC) system driven by the low temperature heat source is established to investigate the overall performance. Hot water temperature from 75 °C to 95 °C is adopted for performance analysis whereas the environmental temperature is about 25 °C. Refrigerant R245fa is selected as working fluid, and scroll expander is employed for power generation. One worth noting fact is that pumpless ORC system shows great potential for low temperature heat recovery. Experimental results indicate that the maximum power output is 232 W, which is obtained at 95 °C hot water inlet temperature. Correspondingly, the average power output is 204 W which is lasted for 6.6 min, revealing the high stability for power generation. For different hot water inlet temperature, the highest energy and exergy efficiency of the system are 2.4% and 13.7%. Besides, performance of novel pumpless ORC system is compared with that of our previous prototype. It shows a remarkable improvement in terms of power output, energy efficiency and exergy efficiency. Power generation process is able to keep constant for 95% of the cycle time. As a result, pumpless ORC may become an alternative solution to low grade heat utilization when compared with conventional small-scale ORC.
[en] Highlights: • Resorption cycle is proposed for the air conditioners (ACs) of electric vehicles (EVs). • Intermittent working modes of the cycle won’t consume the electricity of on-board batteries. • Resorption working pair of CaCl2-NH4Cl-NH3 has reasonable energy density and high COP. • Energy consumption of resorption AC is reasonable if compared with conventional AC of EVs. - Abstract: Conventional compression type air conditioners (ACs) consume a large part of the electricity of batteries on-board of electric vehicles, and that will make the cruising mileage shorter. Sorption and resorption cycles, which are intermittent, may solve this question by the energy storage phases. Both sorption and resorption cycles are analyzed and compared, and both of them have simpler structure if compared with conventional AC for that only two heat exchangers are required. The equilibrium performance analysis shows that resorption working pairs has higher energy density and coefficient of performance (COP) than that of sorption working pairs when the high temperature salt of resorption cycle is same with the halide of sorption cycle. The experimental Clapeyron curves are studied, and CaCl2-NH4Cl-NH3 has best performance. Compared with MnCl2-CaCl2-NH3 and MnCl2-NH4Cl-NH3, the energy density and COP of CaCl2-NH4Cl-NH3 improves by 160% and 35% at least, respectively. The performance of CaCl2-NH4Cl-NH3 is also compared with that of CaCl2-NH3. They have similar smallest energy density, and CaCl2-NH4Cl-NH3 has higher COP if consider the working conditions in the whole year. The energy required for the electric car with a resorption AC is 0.23–0.265 kWh/km, which is acceptable if compared with the results of conventional AC.
[en] Highlights: • A novel self-adaptive sorption system is proposed to reduce nitrogen oxides emission. • Annual required mass of composite sorbents for the novel system ranges from 143 kg to 246 kg. • Annual required volume of composite sorbents is in the range from 358 L to 615 L. • Cost of sorption SCR system by using most composite sorbents is much lower than that of adblue. - Abstract: A novel self-adaptive sorption system is proposed and analyzed, which is considered as an alternative solution to reduce nitrogen oxides emission. Compared with conventional selective catalytic reduction technology, urea solution tank is replaced with sorption reactor for ammonia storage. Composite sorbents are developed with expanded natural graphite treated with sulfuric acid as the matrix. Different sorption working pairs are selected for evaluating working performance of novel system based on testing nitrogen oxides emission of a diesel engine. It is indicated that for operation mode 8, the highest required mass of urea solution per hour could reach 1.9 kg, which is 2.32 times higher than that of composite ammonium chloride. For different composite sorbents, annual required mass ranges from 143 kg to 246 kg and 81 kg to 140 kg in terms of mode 8 and 6 whereas annual required volume is in the range from 358 L to 615 L and 204 L to 350 L, respectively. Cost of novel sorption system by using composite sorbents is generally lower than that of conventional system by using urea solution. It analyzes the feasibility of novel self-adaptive sorption system, which reveals great potential for reducing nitrogen oxides emission.
[en] Highlights: • A promising modular sorption thermal cell is analyzed for combined cold and heat storage. • Permeability of novel composite sorbent is further improved by adding carbon coated nickel. • Sorption rate of novel sorbent is accelerated based on heat and mass transfer enhancement. • Sorption thermal cell of novel composite sorbent has great potentials for scaling applications. - Abstract: Novel composite strontium chloride is developed with expanded natural graphite and carbon coated nickel as the additives. It is indicated that expanded natural graphite and carbon coated nickel are conducive to heat and mass transfer performance, which result in improved sorption characteristic. For composite sorbents with carbon coated nickel, thermal conductivity and permeability range from 0.57 W · m−1 K−1 to 1.93 W m−1 K−1 and from 2.98 × 10−10 m2 to 2.71 × 10−13 m2. Novel composite strontium chloride with carbon coated metal enjoys the faster desorption and sorption reaction rate than that without carbon coated metal. For different evaporation temperatures, sorption quantity of novel composite strontium chloride ranges from 0.28 kg kg−1 to 0.7 kg kg−1. Based on testing results of sorbents with carbon coated nickel, a promising sorption thermal cell is developed and analyzed for combined cold and heat storage, which greatly enhances the versatility and working reliability. Under different working conditions, cold and heat density range from 384 kJ kg−1 to 811 kJ kg−1 and 549 kJ kg−1 to 1648 kJ kg−1. Modular sorption thermal cell could be flexible connected to sorption battery for scaling applications, which reveals great potentials for renewable energy utilization and waste heat recovery.
[en] Highlights: • A cross-flow dew point evaporative cooler prototype is investigated. • The performance of a practical evaporative cooling system is tested and analyzed. • A mathematical model is developed for the cross-flow dew point evaporative cooler. • The coupled dehumidification and cooling process is simulated. - Abstract: This paper investigates the cooling potential of a cross-flow dew point evaporative cooler under various conditions. Preliminary study reveals that the dew point evaporative cooler’s performance does not approach its designed capacity when the ambient humidity goes beyond the thermal comfort zone. To address this problem, an air dehumidification process is proposed before the evaporative cooling takes place. It is observed that the cross-flow cooler is able to achieve improved cooling effectiveness when an appropriate inlet air humidity condition is realized. The influence of different dehumidification levels on its cooling capacity and efficiency is subsequently analyzed. Additionally, a mathematical model is developed to predict the cooler performance. Key findings from this study are: (1) The maximum discrepancy between the simulation results and experimental data is within ±3.0%; (2) the overall wet bulb and dew point effectiveness of the cross-flow cooler can reach 1.25 and 0.85 for cooling of the supply air with moderate humidity; (3) the respective wet bulb effectiveness, cooling capacity and COP of the cross-flow system are 0.86, 2.2 kW and 4.6 under humid ambient air condition; and (4) the dehumidification of the supply air enables the cooling capacity and energy efficiency to be improved by 70–135%.