Analytical and comparative testing of EnergyPlus using IEA HVAC BESTEST E100–E200 test suite

The EnergyPlus building energy simulation software has been tested using the IEA HVAC BESTEST E100–E200 series of tests. The volume 1 final report for the International Energy Agency (IEA) solar heating and cooling programme task 22 building energy simulation test and diagnostic method for heating, ventilating, and air conditioning equipment models (HVAC BESTEST) was recently published in January 2002. HVAC BESTEST is a series of steady-state tests for a single-zone DX cooling system. Cases range from dry to wet coil, low to high part load, and low to high temperatures. This published test suite includes three sets of analytical solutions and results from several other simulation programs for comparison.This test suite was initially used to test EnergyPlus beginning with beta versions prior to its official public release, and it is also applied as an ongoing quality assurance test. The application of these tests proved to be very useful in several ways:

• •revealed input model shortcomings, which resulted in new user inputs being added;
• •revealed reporting errors which were fixed;
• •revealed algorithmic errors which were fixed;
• •revealed algorithmic shortcomings which were improved or eliminated through the use of more rigorous calculations for certain components;
• •in later versions, caught newly introduced bugs before public release of updates.

Overall, the application of this test suite has been extremely useful in debugging and verifying the DX cooling algorithms in EnergyPlus. This paper summarizes the difficulties encountered and the benefits gained in applying the tests.     

Control of miniature proton exchange membrane fuel cells based on fuzzy logic

A control strategy is presented in this paper which is suitable for miniature hydrogen/air proton-exchange membrane (PEM) fuel cells. The control approach is based on process modelling using fuzzy logic and tested using a PEM stack consisting of 15 cells with parallel channels on the cathode side and a meander-shaped flow-field on the anode side. The active area per cell is 8 cm². Commercially available materials are used for the bipolar plates, gas diffusion layers and the membrane-electrode assembly (MEA). It is concluded from a simple water balance model that water management at different temperatures can be achieved by controlling the air stoichiometry. This is achieved by varying the fan voltage for the air supply of the PEM stack. A control strategy of the Takagi Sugeno Kang (TSK) type, based on fuzzy logic, is presented. The TSK-type controller offers the advantage that the system output can be computed in an efficient way: the rule consequents of the controller combine the system variables in linear equations. It is shown experimentally that drying out of the membrane at high temperatures can be monitored by measuring the ac impedance of the fuel cell stack at a frequency of 1 kHz. Flooding of single cells leads to an abrupt drop of the corresponding single-cell voltage. Therefore, the fuzzy rule base consists of the ac impedance at 1 kHz and all single-cell voltages. The parameters of the fuzzy rule base are determined by plotting characteristic diagrams of the fuel cell stack at constant temperatures. The fuel cell stack can be controlled at T=60 °C up to a power level of 7.5 W. The fuel cell stack is controlled successfully even when the external electric load changes. At T=65 °C, a maximum power level of 8 W is found. A decrease of the maximum power level is observed for higher temperatures.     

Template assisted hydrothermal synthesis of CoSnO3 hollow microspheres for electrocatalytic oxygen evolution reaction

The practical complications suffered by the most recognized electrochemical energy systems, such as, water-electrolyzers and metal-air batteries reside in the half-cell oxygen evolution reaction. To resolve this problem, continuous colossal efforts are required to develop the active, affordable and sustainable electrocatalysts. Shape-tailoring of the catalysts, constructed from non-noble metals is one of the emerging strategies to augment the activity of the material toward electrochemical reactions. In the present work, we demonstrate the template-assisted hydrothermal synthesis of hierarchical CoSnO₃ hollow microspheres, constructible from the wafer-thin sheets of CoSnO₃. The hierarchical CoSnO₃ hollow microspheres possess a high specific surface area of 153.59 m²/g, and mesoporous configuration, which are the essential pre-requisites of an electrochemical system. In addition to this, the proposed CoSnO₃ hollow microspheres possess adequate electroactive surface area (793.5 cm²) and happens to be a suitable candidate for driving the oxygen evolution reaction with a low overpotential of 282 mV and Tafel slope of 96.5 mV/dec in alkaline medium. The higher turnover frequency (0.0045 s⁻¹), high specific and mass activities (2.195 mA/cm²_EASA and 28.752 mA/mg, respectively) were observed for CoSnO₃ hollow spheres. Furthermore, the chronoamperometric measurement reveals a good stability of CoSnO₃ hollow microspheres in alkaline condition, satisfying the fundamental demand of an energy system.     

Phosphorus in rivers — ecology and management

This paper examines the nature of the risk to riverine ecosystems from artificially enhanced loads of phosphorus, considers the key sources of phosphorus enrichment and ways of controlling them, and provides a framework for developing control strategies. The aquatic plant community is the foundation for a healthy and diverse riverine ecosystem, providing food, shelter and breeding habitats for a wide range of animal species. Phosphorus enrichment in rivers can degrade the plant community by altering the competitive balance between different aquatic plant species, including both higher plants and algae. This has consequences for the whole ecosystem. To promote healthy riverine plant communities and the wide range of animal species dependent on them, phosphorus concentrations need to be reduced to as near to background levels as possible. The risk of adverse effects declines as phosphorus concentrations approach background levels, such that any incremental reduction should be seen as a positive step towards trophic restoration. Pragmatic management targets vary between 0.02 and 0.1 mg l⁻¹ soluble reactive phosphorus, depending on river type, with an interim target of 0.2 mg l⁻¹ for heavily enriched rivers. Continuous point sources of phosphorus, dominated by sewage treatment works, have a highly important influence on levels of bioavailable phosphorus in the water column through the growing season. It is important to tackle point sources comprehensively so that reductions in phosphorus concentrations are maximised during this critical time of year. Diffuse sources of phosphorus, particularly from agriculture, are a major contributor to phosphorus levels in riverine sediments, where it can be utilised by benthic algae and rooted plants. This phosphorus can also be released into the water column by a variety of processes. As point sources are brought under control, the relative contribution from diffuse sources becomes increasingly important. An integrated programme of control, involving proactive action on both point and diffuse sources, will be required in most circumstances to bring phosphorus levels in the water column and sediment down to near background levels.     

Distinct element analysis of the effect of temperature on the bulk crushing of α-lactose monohydrate

Cryogenic milling could reduce the ductility in the milling operations of semi-brittle and relatively ductile pharmaceutical particles. However, to achieve a better application of this technology, it is necessary to establish the relationship between the influence of temperature on the mechanical properties and breakage characteristics of the single particle and the bulk crushing behavior of these types of material. The focus of this paper is on the analysis of bulk crushing behavior of α-lactose monohydrate particles in response to temperature variations, based on single particle mechanical properties and side crushing strength at different temperatures and the use of distinct element analysis. The effect of temperature on the side crushing strength of the particles has been quantified by quasistatic side crushing tests. The experimental results show a significant increase in the strength of the single particles by decreasing the temperature. These results are used in the distinct element analysis to simulate the bulk crushing behavior of pharmaceutical particles as affected by the temperature. The predictions are compared with the experimental results, for which a reasonable agreement is found for the ambient temperature case. There are some differences for the case of −20°C, due to lack of reliable data for Young's modulus.     

生物滤池处理微污染水源水试验研究

通过中试试验,探讨了在春季温度较低的情况下,不同滤料介质的生物滤池对于姚江微污染水源水的处理效果。研究表明,双层生物滤料滤池能够有效地去除浊度、有机物、氨氮等污染物质,适合于传统滤池的改造。采用颗粒活性炭-石英砂滤料滤池的综合处理效果优于同类型的沸石-石英砂滤料滤池,通过加入一定量的臭氧(1.50 mg/L)可以进一步提高生物滤池的处理效果。     

Effect of fouling reduction by ozone backwashing in a microfiltration system with advanced new membrane material

The effect of ozone back washing for membrane fouling reduction was experimentally investigated in a submerged metal membrane microfiltration system. A cleaning by intermittent ozone gas backwashing was effective in recovering the permeation flux. Intermittent ozone backwashing was highly effective than the air or permeates backwashing for flux recovery. Regarding the operational parameters, the increase of ozone gas flow rate was more effective than the increase of injection time under the conditions of same ozone dose. However, the backwashing cycle was longer, the effect of flux recovery by ozone backwashing decreased. Therefore, it is favorable to operate membrane cleaning before the foulant was consolidated on membrane surface.     

In situ structure/function studies in wastewater treatment systems

As an example of the importance and the potential of in situ structure/function studies, nitrifying aggregates from different zones of a lab-scale fluidised bed reactor were analysed by microelectrode measurements of O₂ NH₄⁺, NO₂⁻, and NO₃⁻ and in situ hybridisation targeting the 16S rRNA of the nitrifying bacteria. A shift trom an ammonia oxidising to a nitrite oxidising community is present along the reactor. In the single aggregates an active nitrifying shell of about 100 gm could be related to the maximum abundance of nitrifiers in this zone. Interestingly, the main actors in this system are not representatives of the well-described genera Nitrosomonas and Nitrobacter but some other ammonia oxidisers from the beta subclass of Protcobacteria and a thus far unknown nitrite oxidising population.     

The relationship between the structure of activated sludge flocs and the sorption of hydrophobic pollutants

The relationships between the structure of minimally perturbed activated sludge flocs and the sorption of organic contaminants were studied. Sorption, settling velocity, size distributions, floc structure and EPS composition were all examined. The results show significant removal of selected halogenated hydrocarbons and polycyclic aromatic hydrocarbons by biosorption to activated sludge flocs. However, statistically significant effects on the settling or size of the flocs caused by this sorption were not observed. The addition of chromium (Cr(III)) metal ions to the biomass caused observable changes in the floc structure and decreased ruthenium red binding to the acidic polysaccharides of the floc matrix. At low concentrations (0.6 mg/1), chromium caused an increase in the sorption of organic compounds to flocs, suggesting that changes in the floc structure can be induced, which can have an impact on the sorption of pollutants to the flocs.     

Improving the electrochemical properties of carbon anodes in lithium secondary batteries

The electrochemical properties of carbon anodes in lithium secondary batteries are improved by the addition of vanadium as V₂O₅. The action of the added V₂O₅ is different from that obtained by incorporating a nonmetallic element such as nitrogen, boron, phosphorous or silicon. Because it can increase the distance between the 002 planes of the carbon and act as nucleating agent that promotes the formation of a layer-like carbon structure, V₂O₅, not only enlarges the carbon anode's reversible capacity of lithium storage but also improves the cycling behavior.