Economic sensitivity of wood biomass utilization for greenhouse heating application

This paper presents an analysis of the impacts of technical and market changes on the economic feasibility of using wood biomass to produce heat for an average-sized greenhouse in British Columbia. A previous techno-economic analysis determined that the installation of a wood pellet or a wood residue boiler to generate 40% of the greenhouse heat demand is more economical than using a natural gas boiler alone to generate all the heat [1]. As the techno-economic analysis contained forecasted parameters, a thorough sensitivity analysis is needed for sound decision making. This paper extends the previous techno-economic study by assessing the effect of fuel price, wood biomass energy contribution, and greenhouse size changes on the net present value (NPV) when using a wood pellet or wood residue boiler with or without an electrostatic precipitator (ESP). The results indicate that the attractiveness of using wood biomass will increase if the price of fossil fuels increases more than 3% per year or carbon taxes and regulations are applied. Increasing the biomass energy contribution by 20% (to provide 60% of the total heat demand) would still be economical. The installation of a wood pellet boiler or a wood residue boiler is economical for average (7.5 ha) or large (15 ha) greenhouses.     

The impact of connate water saturation and salinity on oil recovery and CO2 storage capacity during carbonated water injection in carbonate rock

Carbonated water injection (CWI) is known as an efficient technique for both CO₂ storage and enhanced oil recovery (EOR). During CWI process, CO₂ moves from the water phase into the oil phase and results in oil swelling. This mechanism is considered as a reason for EOR. Viscous fingering leading to early breakthrough and leaving a large proportion of reservoir un-swept is known as an unfavorable phenomenon during flooding trials. Generally, instability at the interface due to disturbances in porous medium promotes viscous fingering phenomenon. Connate water makes viscous fingers longer and more irregular consisting of large number of tributaries leading to the ultimate oil recovery reduction. Therefore, higher in-situ water content can worsen this condition. Besides, this water can play as a barrier between oil and gas phases and adversely affect the gas diffusion, which results in EOR reduction. On the other hand, from gas storage point of view, it should be noted that CO₂ solubility is not the same in the water and oil phases. In this study for a specified water salinity, the effects of different connate water saturations (S_wc) on the ultimate oil recovery and CO₂ storage capacity during secondary CWI are being presented using carbonate rock samples from one of Iranian carbonate oil reservoir. The results showed higher oil recovery and CO₂ storage in the case of lower connate water saturation, as 14% reduction of S_wc resulted in 20% and 16% higher oil recovery and CO₂ storage capacity, respectively.     

Forest biomass supply logistics for a power plant using the discrete-event simulation approach

This study investigates the logistics of supplying forest biomass to a potential power plant. Due to the complexities in such a supply logistics system, a simulation model based on the framework of Integrated Biomass Supply Analysis and Logistics (IBSAL) is developed in this study to evaluate the cost of delivered forest biomass, the equilibrium moisture content, and carbon emissions from the logistics operations. The model is applied to a proposed case of 300 MW power plant in Quesnel, BC, Canada. The results show that the biomass demand of the power plant would not be met every year. The weighted average cost of delivered biomass to the gate of the power plant is about C$ 90 per dry tonne. Estimates of equilibrium moisture content of delivered biomass and CO₂ emissions resulted from the processes are also provided.     

Viscous fingering and its effect on areal sweep efficiency during waterflooding: an experimental study

Viscous fingering is one of the main challenges that could reduce areal sweep efficiency during waterflooding in oil reservoirs. A series of waterflooding experiments were carried out in a Hele-Shaw cell at ambient temperature during which areal sweep efficiency was estimated and techniques to ease the fingering problem were examined. The onset and propagation of viscous fingers were monitored as a function of both injection rate and injection/production positions. Image processing techniques were utilized to quantitatively investigate the propagation of fingers. The experimental results show that, under specific conditions, increasing the number of finger branches could improve the areal sweep efficiency, whereas growth of a single narrow finger has a negative impact on oil displacement efficiency. According to the obtained results, increasing the injection rate improves the areal sweep efficiency up to a critical rate at which viscous fingers start to grow. The impact of heterogeneity of the medium on distributing the viscous fingers was also investigated by introducing two different arrangements of fractures in the model. The results show that fractures perpendicular to the direction of flow would distribute the displacing water more uniformly, while fractures in the direction of flow would amplify the unfavorable sweep efficiency.     

Dynamic Resource Allocation for Multimedia Document Retrieval over High Speed LANs

The emergence of gigabit local area networks (G-LANs) has spurred a tremendous interest in supporting networked multimedia applications over a LAN. In this paper, we propose a mechanism for dynamically allocating network resources in asynchronous LANs. Presentation of multimedia objects with required play-out quality requires Quality of Service (QoS) guarantees by the underlying networking infrastructure. Existing asynchronous LANs, such as Ethernet, do not support the notion of QoS due to their asynchronous media access protocol. For such networks, we propose a dynamic bandwidth management scheme that uses the concept of Time Division Multiple Access (TDMA). Significant performance improvement is observed through experimental results. In particular, the transmission rates for multimedia hosts improve significantly with low jitter variations in media streams. We also propose a framework for graceful degradation of play-out quality of multimedia objects in case the LAN's total capacity is not sufficient to meet the overall demand.     

GENERALIZED EQUATION FOR AIRFLOW RESISTANCE OF BULK GRAINS WITH VARIABLE DENSITY, MOISTURE CONTENT AND FINES

The pressure drop versus airflow data for several types of grains were compiled and a grain specific generalized pressure drop versus airflow equation was developed. The equation predicted pressure drop as a function of airflow when porosity, moisture content and fine concentration were specified. The effect of properties of airflow on the resistance of bulk grain to airflow was also considered in the generalized equation. A modified Leva's equation was developed. The similarity between the grain specific equation and the modified Leva's equation led to a method for estimating the shape factor for irregularly shaped particles.     

Modeling of Vegetation Permittivity at Microwave Frequencies

When materials are to be treated with microwaves for different purposes such as drying, online moisture measurements, disinfestation, and remote sensing, thorough knowledge of the material dielectric properties becomes extremely important. Unlike for other materials, measurement of vegetation dielectric properties is very complicated due to the nature of the materials themselves. Hence, vegetation dielectric models that require fewer accurately and easily measurable physical quantities are of great importance. Therefore, dielectric models that only require the measurement of moisture content (MC) have been investigated for alfalfa, a plant material that has high commercial value in national and international markets. The models were developed by measuring the dielectric properties by using an open-ended coaxial probe at frequencies ranging from over 300 MHz to 18 GHz at 22 degC and at an MC ranging from 12% to 73% in wet basis     

Monitoring and Evaluation Scheme using the Multiple-Criteria-Decision-Making Technique: Application to Irrigation Projects

The application of monitoring and evaluation (M&E) systems to assess agricultural projects has received some attention in recent years. These systems provide valuable information for managers and decision makers by analyzing the implementation process, the progress of trends, and the long-term and short-term effectiveness of these projects. An algorithm is developed to monitor and evaluate drip and pressure irrigation projects in Iran. Different indicators are identified and the framework of an integrated evaluation system is demonstrated using an analytical hierarchy process for multiple-criteria-decision making. There is much subjective information that is quantified and normalized in order to remove any bias in evaluators’ assessment of qualitative measures or sensitivity to linguistic expressions. The application of this system to rank projects in different regions (zones) in Iran is also presented in this paper. The results have shown the significant value of such systems in providing information and input for different decision-making levels.     

EFFECT OF MATURITY AND HARVEST METHOD ON DRYING RATE OF WHEAT

Drying rates of cereals have a significant influence on the drying capacity of dryers. Drying rates are influenced by the variety and type of cereal, past history of the grain, maturity at harvest and the harvest method. The effect of the last two parameters on the drying rate of wheat was investigated by drying a single-kernel-thick layer of wheat in an experimental dryer. The laboratory results indicated that grain in the swath had a higher drying rate than grain standing in the field on a particular day of harvest. The effect of maturity or harvest date on the drying rate did not show any particular trend. In the field, the grain in the swath dried faster than grain standing in the field.     

Soil Moisture Information And Thermal Microwave Emission

This paper presents theoretical and experimental results that demonstrate the depth to which soil moisture can be directly measured using microwave radiometers. The experimental results also document the effect of uniform surface roughness on the response of thermal microwave emission to soil moisture. Experimental measurements were executed in July 1980 at the Texas A&M University Research Farm near College Station, TX. Thermal microwave emission measurements were made at 1.4, 4.9, and 10.7 GHz at both vertical and horizontal polarization at off nadir angles from 0 to 50°. It has been demonstrated that passive microwave measurements at frequencies down to 1.4 GHz can only measure soil moisture directly to very shallow soil depths, approximately 2 cm. This is due to the fact that the soil moisture dependence of the transmission coefficient across the air-soil interface predominates over the soil moisture dependence of the total energy originating within the soil volume. It also has been demonstrated that the combination of low incident angle and measurement frequency in the C-band range does not minimize the effect of surface roughness for passive microwave measurements. This result is significant in view of the fact that this combination of frequency and incident angle has been described as the optimum combination for minimizing the effect of surface roughness on the response of radar-backscatter measurements to soil moisture.