摘要:

Because of their simplicity, ease of operation, and low cost, photovoltaic (PV) thermal systems have been constructed for commercial operation, particularly in developing countries. This work presents a new solar electric thermal energy storage system. The design is of a PV standalone with a packed bed thermal energy storage unit. The unit is intended for use as an economic storage system to supply the heating load (air space and water) with thermal energy where the gap between the main source and the load demand occurs during the night. The bed is packed with different materials that have high thermal properties. Design, savings, and operation are also discussed. The PV system is very efficient for rural areas, especially those with high insulation. The results show that the steel bed gives maximum thermal energy storage, while the pebble bed gives a minimum amount of thermal energy storage. The air mass flow rate affects the storage capacity and charging time. Also, the mathematical results of the electrical energy savings using this novel system ensure the economic point of view and show that it is more efficient for heating loads than other systems. This novel solar system consisting of PV standalone combined with a packed bed thermal storage and heating load overcomes the disadvantages of batteries.

ISSN:0090-8312    

DOI:10.1080/00908319708908906

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

Three pilot-scale continuous mix reactors of 5-L volume each were used to study the effects of retention time (18–42 hours) and initial substrate concentration (50–150 g/L) on the cell yield, lactose consumption, and maximum ethanol concentration during continuous fermentation of cheese whey using the yeast Candida psuedotropicalis. A microaeration rate of 480 mL/min and a nutrient supplement (yeast extract) concentration of 0·1% vol/vol were used. The results indicated that the dissolved oxygen concentration, temperature, cell concentration, lactose utilization rate, and ethanol concentration were affected by hydraulic retention time and initial substrate concentration. The highest cell concentration of 5·46 g/L and the highest ethanol concentration of 57·96 g/L (with a maximum ethanol yield of 99·6% from the theoretical yield) were achieved at the 42-hour hydraulic retention time and the 150 g/L initial substrate concentration, whereas the highest cell yield was observed at the 50 g/L initial substrate concentration and the 36-hour hydraulic retention time. Lactose utilizations of 98, 91, and 83% were obtained with 50, 100, and 150 g/L initial substrate concentrations at the 42-hour hydraulic retention time. A pH control system was found unnecessary.

ISSN:0090-8312    

DOI:10.1080/00908319708908907

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

In this study, a model capable of predicting the steady state performance of a fluidized bed straw gasifier at a wide range of operating conditions was developed. The model was based on the homogeneous equilibrium theory, material and energy balances, and the two-phase theory of gas-solid fluidized beds. The three equilibrium reactions (water-gas shift, methanation and oxidation reactions) were used in the model. The model is kinetic free and capable of predicting the reactor temperature and composition, higher heating value, and production rate of the produced gas.

ISSN:0090-8312    

DOI:10.1080/00908319708908908

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

The sensitivity of the kinetic-free homogeneous equilibrium model, developed for fluidized bed gasification of cereal straw, was tested under a wide range of parameters, including equivalence ratio, bed height, fluidization velocity, solid circulation coefficient, nitrogen-oxygen ratio, and fuel distribution function. The results showed that the bed temperature was sensitive to changes in all of these parameters. The composition and the higher heating value of the produced gas were only affected by the equivalence ratio and the nitrogen-oxygen ratio. The normalized gas production was mainly affected by the equivalence ratio, fluidization velocity, and nitrogen-oxygen ratio.

ISSN:0090-8312    

DOI:10.1080/00908319708908909

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

The validity of the model developed for fluidized bed gasification of biomass was tested using experimental data obtained from a 400 kWthermal, dual-distributor-type fluidized bed gasifier. The fluidized bed was operated on wheat straw at various equivalence ratios, fluidization velocities, and bed heights. Both the predicted and the experimental bed temperatures increased linearly with the increase in equivalence ratio. At higher equivalence ratios (ER > 0·25) the model predictions for gas composition and the higher heating value were in good agreement with the experimental data. However, at lower equivalence ratios (ER < 0·20) the higher heating value of gas and the mole fractions of methane were overpredicted by the model This was because of the drastic increase in tar formation at such low equivalence ratios. The model predictions were improved substantially when the tar formation was included in the model.

ISSN:0090-8312    

DOI:10.1080/00908319708908910

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

The Energy and Environmental Research Corporation (EER), in cooperation with the University of Alabama (UA) and the Mining Division of Jim Walter Resources, Inc. (JWRI), was awarded a U.S. Department of Energy (DOE) contract to retrofit an existing fire-tube boiler to burn coal-water fuel (CWF). Atomization tests were performed on an EER nozzle using JWRI CWF prior to the boiler retrofit. The tests were performed at the Atomization Spray Test Facility located in the JWRI Training Center in Brookwood, Alabama. On the basis of these tests, atomization nozzles were selected for the full-scale combustion tests. The fire-tube boiler on the UA campus was retrofitted and was successfully operated for 800 hours on CWF. The CWF was made from Blue Creek coal fines produced by JWRI, which is located 45 min from the UA campus. JWRI produced 21,295 gallons (106·5 tons) of CWF and shipped this material to the boiler, where it was burned. This article describes the CWF that was used, including reports on the stability, rheology, and particle size. This article also describes the JWRI CWF pilot plant.

ISSN:0090-8312    

DOI:10.1080/00908319708908911

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

The Energy and Environmental Research Corporation (EER), in cooperation with the University of Alabama (UA) and the Mining Division of Jim Walter Resources, Inc. (JWRI), was awarded a U.S. Department of Energy (DOE) contract to retrofit an existing fire-tube boiler to bum coal-water fuel (CWF). A fire-tube boiler on the UA campus was retrofitted, and the CWF was made from Blue Creek coal fines produced by JWRI, which is located 45 min from the UA campus. The boiler was successfully operated for 800 hours on CWF. Operating with CWF required a boiler derating of 20% and natural gas as a support fuel. This article reports on the mechanical details of the conversion of the fire-tube boiler from naturalgas to CWF. The rationale for conversion to CWF and the background on CWF atomization and combustion are given.

ISSN:0090-8312    

DOI:10.1080/00908319708908912

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor