Co- and tri-generation system based on absorption refrigeration cysle: a review

ABSTRACT

Absorption refrigeration system is a heat-driven refrigeration system, which has a good application prospect in co- and tri-generation system, and is of great significance to energy conservation and emission reduction. In this paper, the combined power and cold system the combined power and cooling system and the combined cold cooling, heat, and power system based on absorption refrigeration are reviewed. Working fluid of absorption refrigeration cycle, different configurations, system performance, main application fields, and economic considerations of co- and tri-generation systems were focused in this review. This paper will be useful for the researchers to have a more comprehensive understanding of the application and development prospect of co- and tri-generation systems based on Absorption Refrigeration Cycle.     

Performance of a small-scale solar-powered adsorption cooling system

In this study, an experimental investigation on the performance of a small-scale residential-size solar-driven adsorption (silica gel-water) cooling system that was constructed at Assiut University campus, Egypt is carried out. As Assiut area is considered as hot, arid climate, field tests for performance assessment of the system operation during the summer season are performed under different environmental operating conditions. The system consists of an evacuated tube with a reflective concentration parabolic surface solar-collector field with a total area of 36 m², a silica gel-water adsorption chiller of 8 kW nominal cooling capacity, and hot and cold water thermal storage tanks of 1.8 and 1.2 m³ in volume, respectively. The results of summer season field test show that under daily solar insolation varying from 21 to 27 MJ/m², the solar collectors employed in the system had high and almost constant thermal efficiency. The daily solar-collector efficiency during the period of system operation ranged from about 50% to 78%. The adsorption chiller performance shows that the chiller average daily coefficient of performance (COP) was 0.41 with the average cooling capacity of 4.4 kW when the cooling-water and chilled-water temperatures were about 31°C and 19°C, respectively. As the chiller cooling water is cooled by the cooling tower in the hot arid area, the cooling water is at a higher temperature than the design point of the chiller. Therefore, an experiment was carried out using the city water for cooling. The results show that an enhancement in the chiller COP by 40% and the chilling power by 17% has been achieved when the city water was 27.7°C.     

Refrigeration waste heat utilization for drying applications: a review

ABSTRACT

Cold chain industry has a vast potential for waste heat recovery. It is a matter of importance for energy efficiency point of view, as global energy demand is increasing day by day. Ample amount of low-grade energy is either unutilized or underutilized. The heat rejected by a Heat pump or refrigeration system emerged as a promising solution for dehydration by utilizing low-grade waste heat despite higher investment. As compared to solar drying technology, heat pump drying evolved as a reliable method regarding better process control, energy efficiency, and quality of the product to be dried. Energy utilized through the refrigeration system’s waste/exhaust heat recovery in combination with or without renewable energy source enhances the overall efficiency of the system and also reduces the cost. This useful review investigated and compared the research findings of waste heat utilization through heat pump and from condenser of refrigeration system on laboratory, pilot as well as industrial scale for drying of various fruits, vegetables, and agro products. Various drying parameters like drying rate, moisture content, Specific Moisture Extraction Rate (SMER), Coefficient of Performance (COP), Exergy efficiency, and temperature as well as humidity conditions inside the drying chamber were also reviewed to promote the technological advancement of energy utilization by commercial cold storage waste heat recovery.     

Hazard and Effects of Pollution by Lead on Vegetable Crops

Lead (Pb) contamination of the environment is an important human health problem. Children are vulnerable to Pb toxicity; it causes damage to the central nervous system and, in some extreme cases, can cause death. Lead is widespread, especially in the urban environment, and is present in the atmosphere, soil, water and food. Pb tends to accumulate in surface soil because of its low solubility, mobility, and relative freedom from microbial degradation of this element in the soil. Lead is present in soil as a result to weathering and other pedogenic processes acting on the soil parent material; or from pollution arising caused by the anthropogenic activities; such as mining, smelting and waste disposal; or through the adoption of the unsafe and unethical agricultural practices such as using of sewage sludge, and waste water in production of vegetable crops or cultivation of vegetables near highways and industry regions. Lead concentrations are generally higher in the leafy vegetables than the other vegetables. Factors affecting lead uptake included its concentration in the soil, soil pH, soil type, organic matter content, plant species, and unsafe agriculture practices. Generally, as Pb concentration increased; dry matter yields of roots, stems and leaves as well as total yield decreased. The mechanism of growth inhibition by lead involve: a decrease in number of dividing cells, a reduction on chlorophyll synthesis, induced water stress to plants, and decreased NO ₃ ^- uptake, reduced nitrate and nitrite reductase activity, a direct effect of lead on protein synthesis, a decrease on the uptake and concentration of nutrients in plants. The strategies to minimize Pb hazard can be represented in: (a) Phytoremediation, through natural plants are able to bio-accumulate Pb in their above–ground parts, which are then harvested for removal such as, using Indian Mustard (Brassica juncea), Ragweed (Ambrosia artemisiifolia), Hemp Dogbane (Apocynum cannabium), or Poplar trees, which sequester lead in its biomass. (b) Good and ethical agricultural practices such as cultivation of vegetables crops as far from busy streets or highways and industry regions as well as nonuse of sewage sludge and waste water in cultivated soils. (c) Increasing the absorptive capacity of the soil by adding organic matter and humic acid. (d) Growing vegetable crops and cultivars with a low potential to accumulate lead, especially in soils exposed to atmospheric pollution. (e) Washing of leafy vegetables by water containing 1 % vinegar or peeling roots, tubers, and some fruits of vegetables before consumption may be an important factor in reducing the lead concentration.     

Performance of oil palm kernel shell gasification using a medium-scale downdraft gasifier

This article focused on the performance of oil palm kernel shell (PKS) gasification using a medium-scale downdraft gasifier with a feedstock capacity of 500 kg at a temperature range of 399–700°C and at a feed rate of 177 kg/h. This article is important for evaluating the reliability of PKS gasification for commercial power generation activities from biomass. The process performance was evaluated based on the syngas calorific value (CV), syngas flow rate, and its cold gas efficiency (CGE). The syngas flow rates and CVs were measured using a gas flow meter and a gas analyzer in real time. The data obtained were then analyzed to evaluate the performance of the process. The results showed that the CGE of the process was moderately high (51%) at 681°C, with a high syngas CV (4.45–4.89 MJ/Nm³) which was ideal for gas engine applications. The PKS gasification performance increased when the reactor temperature increased. Projections were made for the CGE and the syngas CV for the PKS gasification with increased reactor temperatures and it was found that these values could be increased up to 80% and 5.2 MJ/Nm^3, respectively at a reactor temperature of 900°C. In addition, the estimated power that could be generated was about 600 kW_e at a maximum operation of 500 kg/h of feed rate. Based on the analysis, a medium-scale PKS gasification is observed to be a promising process for power generation from biomass due to the favorable performance of the process.     

热电冷联供系统在海上平台的应用

文章介绍热电冷联供系统的设备组成及其设计注意事项;介绍以燃气轮机为发电机组的热电冷联供系统案例。在热电冷联供系统中配置溴化锂吸收式制冷机,可充分发挥其利用低品位能源的优势;设计热电冷联供系统前,应进行必要的经济性分析,合理确定设备配置方案和配置容量;以燃气轮机发电机组和烟气型溴化锂吸收式冷热水机组为主要设备组成的热电冷联供系统,烟气系统的设计和安装连接是关键。文章可为燃气轮机热电冷联供系统的设计和建造提供技术参考。     

APPLICATION OF A SINGLE RESERVOIR OPERATION POLICY TO A RAIN WATER CISTERN SYSTEM1

The operation policy for a single reservoir is applied to a rain water cistern system because the functions of a cistern are similar to a simple single reservoir. Since the cistern is a closed system, water loss is negligible. In this study, a dynamic programming analysis has been made to study the effects of the probable weekly rainfall and the water storage in the cistern towards the water consumption policy. The result of this study indicates that the water consumption rate should be adjusted into a lower rate when the water storage in the cistern is low and/or when the expected probable weekly rainfall is low if the owner of the cistern does not want to risk the chance of an empty cistern. The demand for a reliable method for forecasting weekly rainfall is evident in this study.     

关于炼化企业水资源利用的几点思考

通过对我国水资源状况及石化行业水消耗情况分析,找出我国石化企业新鲜水用量,污水排放在绝对量,吨原油、万元产值的单耗,单排等方面与国外相比较存在的差距。指出存在的主要问题是:清污分流不彻底;污污分流不健全;汽提后的净化水回用量小;新鲜水冲洗地面及作为机泵冷却水直排,导致新鲜水的浪费。同时针对以上问题提出相应的建议参考指标及对应措施。     

ADMINISTRATION OF GROUND WATER AS BOTH A RENEWABLE AND NONRENEWABLE RESOURCE1

ABSTRACT: Ground water is intended to be administered in many western states as a flow or renewable resource. In Idaho, this administration is based on the appropriation doctrine of water rights. Two generalizations may be made concerning ground water. First, water artificially discharged from an aquifer system must deplete the total resource by that amount; water consumptively pumped from a well must be derived from either increased recharge, decreased discharge or a decrease of water in storage. Second, the annual rate of recharge to a ground-water system is often only a small percentage of the total resource in storage. Ground water may be divided into flow and stock portions. In those basins where the second generalization is true, most ground water may be classified as stock. However, only the flow portion of ground water may be developed if utilization of the resource is to be enjoyed over an infinite period. Data from the Raft River Basin in Idaho indicate that the flow and stock characteristics of ground water are time dependent. The resource exhibits the characteristics of both a renewable and nonrenewable resource. As a result, present administrative techniques do not provide for effective management of the resource.     

化学需氧量测定方法的改进及研究进展

化学需氧量是综合评价水体污染程度的重要指标,是水质监测的重要水质参数。文章就国标方法的众多改进措施分类进行了探讨,包括消解方法的改进、氧化剂、替代催化剂和酸体系的研究、氯离子干扰的消除以及取样均匀性的改进,然后介绍了相关系数法、分光光度法、连续流动分析法、原子吸收法、电化学法、化学发光分析法、生物法、臭氧氧化法、光催化氧化法等COD测定替代技术,评价了各种方法的优缺点。最后指出,建立灵敏、准确、适应性强、低耗、无二次污染、性价比高COD监测分析方法是COD监测的发展趋势。     

Comparative Life Cycle Assessment of Lignocellulosic Ethanol Production: Biochemical Versus Thermochemical Conversion

Lignocellulosic biomass can be converted into ethanol through either biochemical or thermochemical conversion processes. Biochemical conversion involves hydrolysis and fermentation while thermochemical conversion involves gasification and catalytic synthesis. Even though these routes produce comparable amounts of ethanol and have similar energy efficiency at the plant level, little is known about their relative environmental performance from a life cycle perspective. Especially, the indirect impacts, i.e. emissions and resource consumption associated with the production of various process inputs, are largely neglected in previous studies. This article compiles material and energy flow data from process simulation models to develop life cycle inventory and compares the fossil fuel consumption, greenhouse gas emissions, and water consumption of both biomass-to-ethanol production processes. The results are presented in terms of contributions from feedstock, direct, indirect, and co-product credits for four representative biomass feedstocks i.e., wood chips, corn stover, waste paper, and wheat straw. To explore the potentials of the two conversion pathways, different technological scenarios are modeled, including current, 2012 and 2020 technology targets, as well as different production/co-production configurations. The modeling results suggest that biochemical conversion has slightly better performance on greenhouse gas emission and fossil fuel consumption, but that thermochemical conversion has significantly less direct, indirect, and life cycle water consumption. Also, if the thermochemical plant operates as a biorefinery with mixed alcohol co-products separated for chemicals, it has the potential to achieve better performance than biochemical pathway across all environmental impact categories considered due to higher co-product credits associated with chemicals being displaced. The results from this work serve as a starting point for developing full life cycle assessment model that facilitates effective decision-making regarding lignocellulosic ethanol production.     

Integrated energy management strategy of powertrain and cooling system for PHEV

ABSTRACT

Energy management strategy (EMS) is crucial in improving the fuel economy of plug-in hybrid electric vehicle (PHEV). Existing studies on EMS mostly manage powertrain and cooling system separately which cannot get the minimum total energy consumption. This paper aims to propose a novel EMS for a new type of dual-motor planetary-coupled PHEV, which considers cooling power demand and effect of temperature on fuel economy. Temperature-modified engine model, lithium-ion battery model, two motors, and cooling system models are established. Firstly, the separated EMS (S-EMS) is designed which manages powertrain and cooling system separately. Sequentially, after the analysis of thermal characteristics of the powertrain and cooling system, the thermal-based EMS (T-EMS) is then proposed to manage two systems coordinately. In T-EMS, cooling power demand and the charging/discharging energy of motors are calculated as equivalent fuel consumption and integrated into the object function. Besides, a fuzzy controller is also established to deicide the fuel-electricity equivalent factor with consideration of the effect of temperature and state of charge on powertrain efficiency. Finally, the hardware-in-loop experiment is carried out to validate the real-time effect of EMS under the New European Driving Cycle. The result shows that cooling power demand and temperature can significantly affect the fuel economy of the vehicle. T-EMS shows better performance in fuel economy than S-EMS. The equivalent fuel consumption of the cooling system of T-EMS decreases by 27% compared with that of S-EMS. The total equivalent fuel consumption over the entire trip of PHEV using T-EMS is reduced by 9.7%.     

BACTERIAL LEVELS IN CISTERN WATER SYSTEMS OF NORTHERN KENTUCKY1

ABSTRACT: In rural Northern Kentucky, rainwater is commonly collected from rooftops and stored in cement block cisterns as the sole source of drinking water. Although every cistern system is unique in some aspect of design, use, or maintenance, a bacterial survey of 30 rural Northern Kentucky cistern systems suggests that coliforms and heterotrophic bacteria are common to all types of cistern storage systems. An average of 600 coliforms/ml and 3.6 ± 10⁵ heterotrophic bacteria/ml were detected in water samples from the bottoms of the cistern storage tanks. Bacterial levels in water delivered to household cold tap faucets were similar to the levels found in the storage tanks. When detected, fecal coliforms were recovered throughout the entire system including the household cold tap faucet. Current U.S. regulations for drinking water quality are discussed, with a suggestion that fecal coliform levels may be a more appropriate guideline for interpreting the water quality of individually maintained, nonchlorinated, nonpiped water supplies, such as cistern storage systems.     

余压过滤系统在工业循环水系统中的应用

砂过滤器是一种传统而高效的水处理设备,广泛应用于钢铁企业循环水系统。目前钢铁企业最常用的砂滤器是高速或中速砂过滤器。本文结合新型浅层砂过滤器的应用,对余压过滤系统技术（余压全滤、余压旁滤）应用于钢铁企业循环水系统进行了分析,并对具体的设计方法进行了详细的介绍,可供实际生产和工程建设参考。     

Grey relational analysis of an integrated cascade utilization system of geothermal water

With the drastic decrease in fossil resources and rapid deterioration of the global environment, the utilization of geothermal resources has been strongly advocated. The combination of heat, power, and cold utility generation is commonly used to increase the utilization efficiency of geothermal resources. In this study, an integrated cascade utilization system of waste geothermal water (ICUWGW) from a flash geothermal power plant in China is established to increase the utilization efficiency of geothermal water. The waste geothermal water leaving the power plant is proposed for further use in cascade for two-stage LiBr/H₂O absorption cooling, agricultural product drying, and residential bathing. Twelve candidate temperature schemes showing different inlet and outlet temperatures of every subsystem are proposed for the ICUWGW. Several criteria are selected for the evaluation and screening of the candidate schemes. Grey relational analysis incorporating analytic hierarchy process is conducted to screen the optimal temperature scheme for the ICUWGW to meet the comprehensive criteria of thermodynamics and economics. Results show that the optimal scheme features significant improvement in energy efficiency, exergy efficiency, and equivalent electricity generation efficiency compared with those of the current geothermal power plant. The investment payback time of the additional subsystems for cooling, drying, and bathing is 1.85 years. Exergy analysis is also conducted to determine the further optimization potential of the optimal ICUWGW. Sensitivity analysis of electricity price on the performance of the optimal ICUWGW is also performed.     

Research on distribution performance of desert sand for heat storage in downcomer

In this research, desert sand is used as the sensible heat storage medium, which exchanges heat with air in the downcomer to realize heat storage and heat release. The desert sand distribution uniformity has a significant impact on the heat exchange performance and efficiency between desert sand and air for the process of convection in the downcomer. Given the superiority of sensible heat storage in convective heat transfer between desert sand and air, distributors with cylinder or conical bore solid particles and homogeneity performance testing device are designed and manufactured on the basis of convection system equipped with solid particle–air downcomer. Then, the convection experiment between solid sand and air is researched. The greater the desert sand flow rate and higher the volume density, the larger the variance of regional mass flow rate and the worse the homogeneity performance. For the cylinder bore distributor, the smaller the sand particle size is, the greater affected the sand groups can be. The sand homogeneity performance is preferable with the two particle size ranges: 0.18-0.25 mm and 0.15-0.18 mm. The total sand flow rate decreases, but the uniformity improves with the increase of the air flow velocity, and the best distribution performance is achieved at an air velocity of 0.6 m/s. However, the distribution performance declines with the air flow velocity persistently increasing because the sand groups are pushed to one pipe side close to the wall. The sand groups deflect seriously with the air flow velocity increasing.     

IMPLEMENTATION OF AN OPTIMIZATION MODEL FOR OPERATION OF A METROPOLITAN RESERVOIR SYSTEM1

ABSTRACT: A deterministic dynamic programming optimization model with a refining sectioning search procedure is developed and implemented to find least cost withdrawal and release patterns for water supple from a multiple reservoir system serving a metropolitan area. Applications are made to teh four reservoir system operated by the city of Dallas, Texas. A realistic cost structure, including nonlinear power consumption, block rate unit power costs, and flow dependent power consumption for intracity water distribution, is utilized. Applications are made to find least cost operating patterns and, as well, by inclusion of a water loss penalty function, supply patterns which will reduce evaporation water losses for the Dallas system.     

Quantifying the Impact of Renewable Energy Futures on Cooling Water Use

This article presents an empirically based model, WiCTS ( Wi thdrawal and C onsumption for T hermoelectric S ystems), to estimate regional water withdrawals and consumption implied by any electricity generation portfolio. WiTCS uses water use rates, developed at the substate level, to predict water use by scaling the rates with predicted energy generation. The capability of WiCTS is demonstrated by assessing the impact of renewable electricity generation scenarios on water use in the United States (U.S.) through 2050. The energy generation scenarios are taken from the Renewable Energy Futures Study performed by the U.S. National Renewable Energy Laboratory of the U.S. Department of Energy. Results indicate reductions in water use are achieved under these renewable energy scenarios. The analysis further explores the impact of two modifications to the modeling framework. The first modification presumes geothermal and concentrated solar power generation technologies employ water‐intensive cooling systems vs. cooling technology that requires no water. The second modification presumes all water‐intensive cooling technologies use closed cycle cooling (as opposed to once‐through cooling) technologies by 2050. Results based on one of the renewable generation scenarios indicate water use increases by over 20% under the first modification, and water consumption increases by approximately 40% while water withdrawals decrease by over 85% under the second modification.     

Experimental energy and exergy analyses of a discharging heat exchanger for a small hot-oil domestic storage tank

Experiments are described to investigate the thermal performance of a discharging heat exchanger for a small storage tank filled with oil. Experimental results are presented in terms of the discharging energy rates (power) and the discharging exergy rates for low (~4 ml/s) and high discharging flow rates (~8 ml/s). Water heating energy rates, which are respectively maximized at approximately 600 W and 1200 W at low and high flow-rate discharging, are found to be higher than the discharging energy rates, which are respectively maximized at 450 W and 900 W. These results indicate that the energy rates do not accurately evaluate the thermal performance of the discharging heat exchanger since the energy heating rate of the water is greater than that for the oil that heats it, which is thermodynamically inconsistent. The energy rates should thus be used with caution when the thermal performance of the heat exchanger is evaluated. Water heating exergy rates, which are respectively maximized at approximately 45 W and 130 W at low and high flow-rate discharging, are generally smaller than the discharging exergy rates, which are respectively maximized at 65 W and 170 W. Exergy rate results are thus more consistent in the physical process of water heating, and an exergy factor is suggested as a proper measure for evaluating the performance of the discharging heat exchanger. The maximum value of the exergy factor is found to increase from 0.15 at low flow rates to a maximum value of approximately 0.19 at high flow rates. This implies that to extract more energy from a storage tank to a discharging heat exchanger, the flow rate has to be high, which is consistent with the physical process of heating water faster to higher temperatures. The exergy factor can thus be used as a design parameter for discharging heat exchangers.     

Dynamic characteristics of cool thermal energy storage systems—a review

Cool thermal energy storage (CTES) plays a significant role in conserving available energy, improving its utilization, and correcting the mismatch that occurs between the supply and demand of energy. It has been employed in many applications, for example, cool storage systems for air-conditioning and natural cooling of energy-efficient building. CTES is widely used in various industrial applications such as food and pharmacy processing, where large short duration loads are often required. This paper presents a review on CTES systems and characteristics. The dynamic characteristics of chilled water storage system, coil pipe cool storage system, packed bed cool storage system, gas hydrate cool storage system, and ice slurry cool storage system are analyzed and discussed. The applications of CTES system are summarized.