基于DeviceNet现场总线的快速热处理设备控制系统设计

介绍了一种基于DeviceNet现场总线的快速热处理设备控制系统。首先介绍了该系统的硬件构成,本控制系统采用了基于现场总线和模块化设计思想,使得该系统的能够满足快速热处理设备的加热腔的数量可任意配置,具有很好的可扩展性;然后提出了一个分层的、模块化的、可配置的软件控制系统,并对其进行了简要概述;最后设计了一个基于系统模型的温度控制器,该控制器采用了前馈控制与反馈控制相结合的方法,其中,前馈通道用来预测控制输出,从而提高了系统响应速度;反馈通道用来修正模型误差和外界干扰,从而提高了控制系统的鲁棒性和控制精度。     

Thermoeconomic analysis of a standalone solar hydrogen system with hybrid energy storage

A comprehensive thermoeconomic analysis is presented for a novel integrated solar hydrogen energy system for standalone operation. The proposed system includes a solar PVT module (photovoltaic thermal), a FC (Fuel cell) and a battery to meet the electrical load demand and domestic hot water over a year. The PVT component works as a primary energy source converting solar energy into electricity and heat. The excess electrical energy and hot water produced by PVT are consumed for producing hydrogen, which can be stored. The generated hydrogen is fed to the fuel cell to produce electricity and water to satisfy the demand. The proposed system is convenient for different seasons of the year because in all time, produced power satisfy the demand. The first and second laws of thermodynamics are used to evaluate the performance of each component and the overall system. Economic assessment of this system is also conducted considering the net present cost, and the system performance is optimized based on this parameter. The overall electrical efficiency of the system is obtained as 9% and the levelized cost of electricity is determined as $ 0.286/kWh. For a steady operation of system, integrating a battery system is convenient when solar energy is not available for a short term. When there is a longer-term shortage of solar radiation, up to 8 days, the electricity can be supplied by utilizing the hydrogen storage system.     

Energy and economic performance analysis of an open cycle solar desiccant dehumidification air-conditioning system for application in Hong Kong

In this article, a transient simulation model and the EnergyPlus were used to study the energy performance and economical feasibility for integrating a solar liquid desiccant dehumidification system with a conventional vapor compression air-conditioning system for the weather condition of Hong Kong. The vapor compression system capacity in the solar assisted air-conditioning system can be reduced to 19 kW from original 28 kW of a conventional air-conditioning system as a case study due to the solar desiccant cooling. The economical performance of the solar desiccant dehumidification system is compared with that of the conventional air-conditioning system. The results show that the energy saving potentials due to incorporation of the solar desiccant dehumidification system in a traditional air-conditioning system is significant for the hot wet weather in Hong Kong due to higher COP resulted from higher supply chilled water temperature from chiller plants. The annual operation energy savings for the hybrid system is 6760 kWh and the payback period of the hybrid system is around 7 years. The study shows that the solar assisted air-conditioning is a viable technology for utilizations in subtropical areas.     

A new solar and geothermal based integrated ammonia fuel cell system for multigeneration

In this study, a new solar and geothermal based integrated system is developed for multigeneration of electricity, fresh water, hydrogen and cooling. The system also entails a solar integrated ammonia fuel cell subsystem. Furthermore, a reverse osmosis desalination system is used for fresh water production and a proton exchange membrane based hydrogen production system is employed. Moreover, an absorption cooling system is utilized for district cooling via available system waste heat. The system designed is assessed thermodynamically through approaches of energy and exergy analyses. The overall energy efficiency is determined to be 42.3%. Also, the overall exergy efficiency is assessed, and it is found to be 21.3%. The exergy destruction rates in system components are also analysed and the absorption cooling system generator as well as geothermal flash chamber are found to have comparatively higher exergy destruction rates of 2370.2 kW and 643.3 kW, respectively. In addition, the effects of varying system parameters on the system performance are studied through a parametric analyses of the overall system and associated subsystems.     

Use of desiccant dehumidification to improve energy utilization in air-conditioning systems in Beirut

Humidity and indoor moist surrounding affect air cleanliness and protects harmful microorganisms when relative humidity is above 70%. In humid climates, the humidity issues are a major contributor to energy inefficiency in HVAC devices. The use of liquid desiccant dehumidification systems of supply air is a viable alternative to reduce the latent heat load on the HVAC system and improve efficiency. Thermal energy, at a temperature as low as 40–50°C, required for the operation of a liquid desiccant hybrid air conditioner can be efficiently obtained using a flat-plate solar collector. In this work a model of a solar-operated liquid desiccant system (using calcium Chloride) for air dehumidification is developed. The system utilizes packed beds of counter flow between an air stream and a solution of liquid desiccant for air dehumidification and solution regeneration. The desiccant system model is integrated with a solar heat source for performance evaluation at a wide range of recorded ambient conditions for Beirut city. Standard mass and energy balances are performed on the various components of the system and a computer simulation program is developed for the integrated system analysis. The desiccant system of the current study replaces a 3 TR (10.56 kW) vapour compression unit for a typical house as low latent load application, and is part of a hybrid desiccant–vapour compression system for a high latent load application, namely a small restaurant with an estimated cooling load of 11.39 TR (40 kW), including reheat. The relevant parameters of the desiccant system are optimized at peak load, and it is found out that there is an important energy saving if the ratio of the air flow rate in the regenerator to that in the dehumidifier is about 0.3 to 0.4. The COP of the desiccant unit is 0.41 for the house, and 0.45 for the restaurant. The size of the vapor compression unit of the restaurant is reduced to 8 TR when supplemented by a desiccant system. The performance is studied of the desiccant system integrated with a solar collector system and an auxiliary natural gas heater to heat the regenerator. The transient simulation of the solar desiccant system is performed for the entire cooling season. The solar fraction for the house is equal to 0.25, 0.47, and 0.68 for a collector area of 28.72, 57.44, and 86.16 m², respectively. The solar fraction for the restaurant is 0.19, 0.38, and 0.54, for the same collector areas. The life cycle savings for the house run solely on desiccant system were positive only if natural gas is available at a cheap price. For the restaurant, the economic benefit of the desiccant system is positive, because the need for reheat in the vapor compression system is eliminated. For a gas price of 0.5638 $/kg, the payback period for the restaurant turned out to be immediate if the energy is supplied solely by natural gas, and 11 years if an 86.16 m² solar collector is implemented to reduce the fuel consumption. Copyright © 2003 John Wiley & Sons, Ltd.     

发动机缸盖水路分布测试系统研制

为了全面了解发动机冷却性能,本文研制了一套冷却水套内水路分布测试系统,实验装置为设计性能优良的冷却系统、为建立设计系统数据库,以及为确定评价设计系统优劣的指标和提供实验研究的手段,研究设计了一套缸盖上水孔流量测量系统,为缸盖内流场分布的数值模拟提供更准确的边界条件并可对各缸流量分布的合理性进行评价。     

Optimal green energy management for island resorts in Malaysia

This paper proposes optimum green energy systems for electricity generation of island resorts in Malaysia. A combination of solar energy and wind energy as intermittent renewable energy sources with a fuel cell (FC) system and a battery storage energy system as a backup to the green energy system is introduced for this study. This system is eco-friendly, economical over the long-term, highly sustainable and reliable. In addition, a diesel-based energy system as a non-green system is compared with the proposed green system. National Renewable Energy Laboratory's (NREL) HOMER software is used to determine and compare the optimal configuration green energy system with the diesel-based energy system in terms of net present cost, sensitivity analysis and pollutant gas emission. The feasibility and assessment of the proposed system is evaluated by utilizing the load profile and considering the geographical condition of a village (Juara village in Tioman Island) with approximately 30 chalets located in southern Malaysia. HOMER uses two types of load profiles for each given year. The first load profile is used during the presence of tourists, and the second profile is used when the locals are the main inhabitants of the island. The optimization management for the green energy system is performed through unit sizing to find the optimum power management analysis and to perform cost analysis of the system.The potential of renewable energy as well as a diesel-based energy system to meet the power demand for such a stand-alone system is considered. Technically feasible and economically viable green energy systems as prospective plans are explored in this study.     

Optimisation and techno-economic analysis of autonomous photovoltaic–wind hybrid energy systems in comparison to single photovoltaic and wind systems

A techno-economic analysis for autonomous small scale photovoltaic–wind hybrid energy systems is undertaken for optimisation purposes in the present paper. The answer to the question whether a hybrid photovoltaic–wind or a single photovoltaic or wind system is techno-economically better is also sought. Monthly analysis of 8 year long measured hourly weather data shows that solar and wind resources vary greatly from one month to the next. The monthly combinations of these resources lead to basically three types of months: solar-biased month, wind-biased month and even month. This, in turn, leads to energy systems in which the energy contributions from photovoltaic and wind generators vary greatly. The monthly and yearly system performances simulations for different types of months show that the system performances vary greatly for varying battery storage capacities and different fractions of photovoltaic and wind energy. As well as the system performance, the optimisation process of such hybrid systems should further consist of the system cost. Therefore, the system performance results are combined with system cost data. The total system cost and the unit cost of the produced electricity (for a 20 year system lifetime) are analysed with strict reference to the yearly system performance. It is shown that an optimum combination of the hybrid photovoltaic–wind energy system provides higher system performance than either of the single systems for the same system cost for every battery storage capacity analysed in the present study. It is also shown that the magnitude of the battery storage capacity has important bearings on the system performance of single photovoltaic and wind systems. The single photovoltaic system performs better than a single wind system for 2 day storage capacity, while the single wind system performs better for 1.25 day storage capacity for the same system cost.     

An electrical modeling and fuzzy logic control of a fuel cellgeneration system

The fuel cell generation system consists of a stack, a reformer, and converters. The stack generates DC power by electrochemical reaction. For system design and analysis, it is necessary to obtain electrical models. Simplified electrical models of a fuel cell generation system for system control are proposed. Then using the electrical models, system performance of a fuel cell generation system in which power is boosted by step-up choppers is analyzed. A fuzzy controller is designed for improved system performance. Simulation and experimental results confirmed the high performance capability of the designed system     

Design, construction, performance evaluation and economic analysis of an integrated collector storage system

The design and construction of an Integrated Collector Storage (ICS) system is presented in this paper. The main advantage that such a collector system presents, with respect to conventional flat-plate collectors, is the fact that it is of a very low profile. The main disadvantage of these collectors comes from the design of the system, i.e. with the receiver of the collector being also the storage vessel, it is not possible to insulate it properly and there are significant heat losses during the night. System modelling and optimisation is carried out by the use of a computer code written for the purpose. Performance results presented are in good agreement with the predicted results, especially for the end-of-day storage temperature which is predicted to within 5.1%. The initial cost of the system presented here is 13% cheaper than the corresponding flat-plate (FP) collector of the same aperture area and storage volume. Additionally, the economic analysis of the two systems, performed with the F-Chart program, showed a yearly F-value of 0.85 for the ICS system compared to 0.83 for the FP system, a pay-back period of nine years for the ICS system, compared to 11 years for the FP system and a life cycle saving of C£330 for the ICS system compared to C£201 for the FP system.     

Self-Convectional Three-Dimensional Integrated Circuit Cooling System using Micro Flat Heat Pipe for Portable Devices

A self-convectional three-dimensional integrated circuit (3D IC) cooling system using micro flat heat pipes (MFHP) was proposed and the electrothermal behavior of the proposed structure was modeled by an equivalent circuit for simulation. Experimental measurements using the fabricated evaluation board for the 3D IC cooling system demonstrated that the temperature of the chip under test drops about 42°C due to the MFHP on the chip in steady state. The cooling performance of the proposed system is satisfactory for use as a 3D IC cooling system for mobile applications. We have applied the proposed system to the central processing unit cooler of a commercial laptop personal computer (PC). The volume of an air cooling system with conventional heat pipes for a laptop PC is about 40 times larger than that of the proposed system. However, the cooling performance of the proposed system is comparable to the original air cooler in the laptop PC both for horizontal and for vertical operation of the MFHP. The main advantage of the proposed cooler is that it is a slim, noiseless system that operates without additional cooling power consumption. The experimental results for vertical and horizontal operation of the MFHP demonstrate the possibility of the proposed self-convection MFHP architecture as a solution for the cooling system of 3D ICs that is suitable for portable devices.     

Use of TRNSYS for modelling and simulation of a hybrid pv–thermal solar system for Cyprus

This paper deals with the modelling and simulation of a hybrid photovoltaic–thermal (PV/T) solar energy system. This is a combined system consisting of a normal PV panel at the back of which a heat exchanger with fins is embedded. The advantage of this type of system is that the PV panel operates at a lower temperature, thus more efficiently, and also hot water is produced at the same time as electricity. The PV system consists of a series of PV panels, a battery bank and an inverter whereas the thermal system consists of a hot water storage cylinder, a pump and a differential thermostat. The system is modelled using TRNSYS, which is a transient simulation program and typical meteorological year (TMY) conditions for Nicosia, Cyprus. The main component of the TRNSYS deck file constructed for this purpose is Type 49, accompanied by other additional components required for the model. The results show that the optimum water flow rate of the system is 25 l/h. The hybrid system increases the mean annual efficiency of the PV solar system from 2.8% to 7.7% and in addition covers 49% of the hot water needs of a house, thus increasing the mean annual efficiency of the system to 31.7%. The life cycle savings of the system is Cy£790.00 and the pay-back time is 4.6 years.     

Thermal design of a roof-mounted CLFR collection system for a desert absorption chiller

The paper presents a mathematical model for the thermal design of a new solar energy collection system adopted to drive an absorption chiller for air-conditioning a modern desert home. The collection system employs roof-mounted, retractable compact linear Fresnel mirrors. The conceptual design is described, and the mathematical model is presented. A hypothetical, two-floor home located in a typical desert site is employed for demonstration. The performance of the proposed solar collection system is evaluated employing a mathematical model presented here. Investigations are conducted to assess the effect of various design parameters on system efficiency. It is concluded that it is feasible to carry the entire house cooling loads employing only solar power collected with the proposed roof-mounted system, even though the house is located in an exceptionally hot desert environment. Moreover, the proposed system may require less roof space than a Photovoltaic-based system when correct conditions are present.     

Simulation and optimization of a LiBr solar absorption cooling system with evacuated tube collectors

Solar radiation is a clean form of energy, which is required for almost all natural processes on earth. Solar-powered air-conditioning has many advantages when compared to a conventional electrical system. This paper presents a solar cooling system that has been designed for Malaysia and similar tropical regions using evacuated tube solar collectors and LiBr absorption unit. The modeling and simulation of the absorption solar cooling system is carried out with TRNSYS program. The typical meteorological year file containing the weather parameters for Malaysia is used to simulate the system. The results presented show that the system is in phase with the weather, i.e. the cooling demand is large during periods that the solar radiation is high. In order to achieve continuous operation and increase the reliability of the system, a 0.8 m³ hot water storage tank is essential. The optimum system for Malaysia's climate for a 3.5 kW (1 refrigeration ton) system consists of 35 m² evacuated tubes solar collector sloped at 20°.     

Multivariable control algorithm for laboratory experiments in wind energy conversion

Advanced experimentation with wind energy conversion systems is described. The real time multivariable control of a wind turbine is designed for investigation of theoretical concepts and their physical implementation. The control system includes a speed controller and a disturbance estimator for enhanced robustness of the control system. In order to provide students with deeper understanding of wind energy and energy extraction, a maximum power point tracking algorithm is developed and integrated into the control system. The multivariable control system is implemented in a small wind turbine laboratory system. A power electronic interface is based on two DC–DC converters: a buck converter for control of the speed and a boost converter controlling the load voltage. Experimental results demonstrate effectiveness of the multivariable control system for a wind turbine providing maximum power extraction. The experiment can be reconfigured for teaching various control concepts to both undergraduate and graduate students.     

Evaluation of the performance of combined cooling,heating, and power systems with dual power generation units

The benefits of using a combined cooling, heating, and power system with dual power generation units (D-CCHP) is examined in nine different U.S. locations. One power generation unit (PGU) is operated at base load while the other is operated following the electric load. The waste heat from both PGUs is used for heating and for cooling via an absorption chiller. The D-CCHP configuration is studied for a restaurant benchmark building, and its performance is quantified in terms of operational cost, primary energy consumption (PEC), and carbon dioxide emissions (CDE). Cost spark spread, PEC spark spread, and CDE spark spread are examined as performance indicators for the D-CCHP system. D-CCHP system performance correlates well with spark spreads, with higher spark spreads signifying greater savings through implementation of a D-CCHP system. A new parameter, thermal difference, is introduced to investigate the relative performance of a D-CCHP system compared to a dual PGU combined heat and power system (D-CHP). Thermal difference, together with spark spread, can explain the variation in savings of a D-CCHP system over a D-CHP system for each location. The effect of carbon credits on operational cost savings with respect to the reference case is shown for selected locations.     

Feasibility study on novel hybrid ground coupled heat pump system with nocturnal cooling radiator for cooling load dominated buildings

When the ground coupled heat pump (GCHP) system is utilized for air conditioning in cooling load dominated buildings, the heat rejected into ground will accumulate around the ground heat exchangers (GHE) and results in system performance degradation. A novel hybrid ground coupled heat pump (HGCHP) system with nocturnal cooling radiator (NCR) works as supplemental heat rejecter is proposed in this paper to resolve this problem. The practical analytical model of NCR and novel HGCHP system are established. The computer program based on established model is developed to simulate the system operation performance. The novel HGCHP system is designed and simulated for a sample building located in Hong Kong, and a simple life cycle cost comparisons are carried out between this system and conventional GCHP system. The results indicate that it is feasible to use NCR serves as supplemental heat rejecter of the novel HGCHP system for cooling load dominated buildings even those located in humid subtropical climate areas. This novel HGCHP system provides a new valuable choice for air conditioning in cooling load dominated buildings, and it is especially suitable for buildings with limited surface land areas.     

Hybrid feedforward and feedback controller design for nuclear steamgenerators over wide range operation using genetic algorithm

In this paper, a simplified model with a lower order is first developed for a nuclear steam generator system and verified against realistic environments. Based on this simplified model, a hybrid multi-input and multi-out (MIMO) control system, consisting of feedforward control (FFC) and feedback control (PEC), is designed for wide range conditions by using the genetic algorithm (GA) technique. The FFC control, obtained by the GA optimization method, injects an a priori command input into the system to achieve an optimal performance for the designed system, while the GA-based FBC control provides the necessary compensation for any disturbances or uncertainties in a real steam generator. The FBC control is an optimal design of a PI-based control system which would be more acceptable for industrial practices and nuclear power plant control system upgrades. The designed hybrid MIMO FFC/FBC control system is first applied to the simplified model and then to a more complicated model with a higher order which is used as a substitute of the real system to test the efficacy of the designed control system. Results from computer simulations show that the designed GA-based hybrid MIMO FFC/FBC control can achieve good responses and robust performances. Hence, it can be considered as a viable alternative to the current control system upgrades     

Combining simulation techniques and design expertise in a renewable energy system design package, RESSAD

Computer simulation is an increasingly popular tool for determining the most suitable renewable energy system type, design and control for an isolated community or homestead. However for the user without any expertise in system design, the complicated process of system component and control selection using computer simulation takes on a trial and error approach. Our renewable energy system design package, RESSAD, has been developed to simulate a wide range of renewable power supply systems, and to go beyond system simulation, by combining design expertise with the simulation model. The knowledge of the system designer is incorporated into the package through a range of analysis tools that assist in the selection process, without removing or restricting individual choices. The system selection process is analysed from the early stages of renewable resource assessment to the final evaluation of the results from a simulation of the chosen system. The approach of the RESSAD package in this selection process is described and its use is illustrated by two case studies in Western Australia.