Energy use in Denmark

This paper reviews the evolution of energy use in Denmark since the early 1970s, in order to shed light on the future path of energy use in Denmark, with particular emphasis on the role of energy efficiency. Improvements in end-use energy efficiency reduced primary energy requirements in Denmark by 22% between 1972 and 1988. This change accounts for two-thirds of the decline in the ratio of energy use to gross domestic product that occurred during this time: the rest of the decline was caused by changes in the mix of goods and services produced and consumed by the Danes. Total energy savings achieved between 1972 and 1988 in Denmark ranked among the highest measured in any major OECD country. Overall, most of the energy savings in Denmark were brought about through improvements in technology. Short-term changes in consumer behaviour were significant in reducing energy needs for space heating and transport. An important stimulus for improved efficiency was higher energy prices, led in no small part by significant taxes imposed on small consumers of heating oil, electricity and motor fuels.     

EVALUATION OF GREAT LAKES NET BASIN SUPPLY FORECASTS1

ABSTRACT: Evaluation of the Great Lakes Environmental Research Laboratory's (GLERL's) physically-based monthly net basin supply forecast method reveals component errors and the effects of model improvements for use on the Laurentian Great Lakes. While designed for probabilistic outlooks, it is assessed for giving deterministic outlooks along with other net basin supply forecast methods of the U.S. Army Corps of Engineers and Environment Canada, and with a stochastic approach commissioned by the Corps. The methods are compared to a simple clima-tological forecast and to actual time series of net basin supplies. Aetual net basin supplies are currently determined by estimating all components directly, instead of as water-balance residuals. This is judged more accurate and appropriate for both forecasting and simulation. GLERL's physically-based method forecasts component supplies while the other methods are based on residual supplies. These other methods should be rederived to be based on component supplies. For each of these other methods, differences between their outlooks and residual supplies are used as error estimates for the rederived methods and component supplies. The evaluations are made over a recent period of record high levels followed by a record drought. Net basin supply outlooks are better than climatology, and GLERL's physically-based method performs best with regard to either component or residual net basin supplies. Until advances are made in long-range climate outlooks, deterministic supply outlooks cannot be improved significantly.     

SEDIMENT TRANSPORT AND CHANNEL MORPHOLOGY OF SMALL,FORESTED STREAMS1

This paper reviews sediment transport and channel morphology in small, forested streams in the Pacific Northwest region of North America to assess current knowledge of channel stability and morphology relevant to riparian management practices around small streams. Small channels are defined as ones in which morphology and hydraulics may be significantly influenced by individual clasts or wood materials in the channel. Such channels are headwater channels in close proximity to sediment sources, so they reflect a mix of hillslope and channel processes. Sediment inputs are derived directly from adjacent hillslopes and from the channel banks. Morphologically significant sediments move mainly as bed load, mainly at low intensity, and there is no standard method for measurement. The larger clastic and woody elements in the channel form persistent structures that trap significant volumes of sediment, reducing sediment transport in the short term and substantially increasing channel stability. The presence of such structures makes modeling of sediment flux in these channels — a potential substitute for measurement — difficult. Channel morphology is discussed, with some emphasis on wood related features. The problem of classifying small channels is reviewed, and it is recognized that useful classifications are purpose oriented. Reach scale and channel unit scale morphologies are categorized. A “disturbance cascade” is introduced to focus attention on sediment transfers through the slope channel system and to identify management practices that affect sediment dynamics and consequent channel morphology. Gaps in knowledge, errors, and uncertainties have been identified for future research.     

Application of powdered activated carbon coating to fabrics in a hybrid filter to enhance mercury removal

Elemental mercury(Hg0) is predominant constituent of flue gas emitted from coal-fired power plants. Adsorption has been considered the best available technology for removal of Hg0 from flue gas. However, adsorbent injection increases the amount of ash generated. In the present study, powdered activated carbon(PAC) was coated on polytetrafluoroethylene/glass fiber filters to increase Hg0 removal while concurrently reducing the amount of ash generated. The optimal PAC coating rate was determined in laboratory experiments to ensure better Hg0 removal with low pressure drop. When PAC of particle size less than 45 μm was used, and the areal density was 50 g/m2, the pressure drop remained under 30 Pa while the Hg0 removal efficiency increased to 15.8% from4.3%. The Hg0 removal efficiency also increased with decrease in filtration velocity. The optimal PAC coating rate was applied on a hybrid filter(HF), which was combined with a bag filter and an electrostatic precipitator in a single chamber. Originally designed to remove fine particulates matter, it was retrofitted to the flue gas control device for simultaneous Hg0 removal. By employing the PAC coating, the Hg removal efficiency of the HF increased to 79.79% from 66.35%. Also, a temporary reduction in Hg removal was seen but this was resolved following a cleaning cycle in which the dust layer was removed.     

Highly siliceous MCM-48 from rice husk ash for CO2 adsorption

Mesoporous MCM-48 silica was synthesized using a cationic-neutral surfactant mixture as the structure-directing template and rice husk ash (RHA) as the silica source. The MCM-48 samples were characterized by X-ray powder diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), N₂ physisorption and SEM. X-ray diffraction pattern of the resulting MCM-48 revealed typical pattern of cubic Ia3d mesophase. BET results showed the MCM-48 to have a surface area of 1024 m²/g and FT-IR revealed a silanol functional group at about 3460 cm⁻¹. Breakthrough experiments in the presence of MCM-48 were also carried out to test the material's CO₂ adsorption capacity. The breakthrough time for CO₂ was found to decrease as the temperature increased from 298 K to 348 K. The steep slopes observed shows the CO₂ adsorption occurred very quickly, with only a minimal mass transfer effect and very fast kinetics. In addition, amine grafted MCM-48, APTS-MCM-48 (RHA), was prepared with the 3-aminopropyltriethoxysilane (APTS) to investigate the effect of amine functional group in CO₂ separation. An order of magnitude higher CO₂ adsorption capacity was obtained in the presence of APTS-MCM-48 (RHA) compared to that with MCM-48 (RHA). These results suggest that MCM-48 synthesized from rice husk ash could be usefully applied for CO₂ removal.     

Predicting Debris Yield From Burned Watersheds: Comparison of Statistical and Artificial Neural Network Models1

Abstract: Alluvial fans in southern California are continuously being developed for residential, industrial, commercial, and agricultural purposes. Development and alteration of alluvial fans often require consideration of mud and debris flows from burned mountain watersheds. Accurate prediction of sediment (hyper‐concentrated sediment or debris) yield is essential for the design, operation, and maintenance of debris basins to safeguard properly the general population. This paper presents results based on a statistical model and Artificial Neural Network (ANN) models. The models predict sediment yield caused by storms following wildfire events in burned mountainous watersheds. Both sediment yield prediction models have been developed for use in relatively small watersheds (50‐800 ha) in the greater Los Angeles area. The statistical model was developed using multiple regression analysis on sediment yield data collected from 1938 to 1983. Following the multiple regression analysis, a method for multi‐sequence sediment yield prediction under burned watershed conditions was developed. The statistical model was then calibrated based on 17 years of sediment yield, fire, and precipitation data collected between 1984 and 2000. The present study also evaluated ANN models created to predict the sediment yields. The training of the ANN models utilized single storm event data generated for the 17‐year period between 1984 and 2000 as the training input data. Training patterns and neural network architectures were varied to further study the ANN performance. Results from these models were compared with the available field data obtained from several debris basins within Los Angeles County. Both predictive models were then applied for hind‐casting the sediment prediction of several post 2000 events. Both the statistical and ANN models yield remarkably consistent results when compared with the measured field data. The results show that these models are very useful tools for predicting sediment yield sequences. The results can be used for scheduling cleanout operation of debris basins. It can be of great help in the planning of emergency response for burned areas to minimize the damage to properties and lives.     

Spatial and temporal variations in NO2 distributions over Beijing,China measured by imaging differential optical absorption spectroscopy

During the CAREBEIJING campaign in 2006, imaging differential optical absorption spectroscopy (I-DOAS) measurements were made from 08:00 to 16:00 on September 9 and 10 over Beijing, China. Detailed images of the near-surface NO₂ differential slant column density (DSCD) distribution over Beijing were obtained. Images with less than a 30-min temporal resolution showed both horizontal and vertical variations in NO₂ distributions. For DSCD to mixing ratio conversion, path length along the lines of I-DOAS lines of sight was estimated using the light-extinction coefficient and Ångstrom exponent data obtained by a transmissometer and a sunphotometer, respectively. Mixing ratios measured by an in-situ NO₂ analyzer were compared with those estimated by the I-DOAS instrument. The obtained temporal and spatial variations in NO₂ distributions measured by I-DOAS for the two days are interpreted with consideration of the locations of the major NO_x sources and local wind conditions. I-DOAS measurements have been applied in this study for estimating NO₂ distribution over an urban area with multiple and distributed emission sources. Results are obtained for estimated temporal and spatial NO₂ distributions over the urban atmosphere; demonstrating the capability of the I-DOAS technique. We discuss in this paper the use of I-DOAS measurements to estimate the NO₂ distribution over an urban area with multiple distributed emission sources.     

Electrostatic enhancement of collection efficiency of the fibrous filter pretreated with ionic surfactants

A study of the electrostatic enhancement of collection efficiency of filters pretreated with ionic surfactants has been carried out in controlled conditions with monodisperse aerosols. Cationic surfactant (dimethyl dioctadecylammonium bromide [DDAB]) and anionic surfactant (sodium oleate [SO]) were used to pretreat polypropylene fibrous filters as the positively and negatively charged filters, respectively. The effects of aerosol size, aerosol charge state, face velocity, aerosol type, and relative humidity (RH) were considered to elucidate their influence on the aerosol penetration. Results indicate that penetration through surfactant-pretreated filters was lower than that through untreated filters, and pretreatment of the filter with surfactant was observed not to affect the structure of the filter. The electrofieldmeter direct-measured the very clear electric field of filter when treating ionic surfactants. The results proved that pretreatment with surfactant caused filters to become charged. Comparing penetration through surfactant-pretreated filters with that through untreated filters with neutral aerosol, the penetration reduction factor of the surfactant-pretreated filters was in the range 1.3-2.2. Comparing aerosol penetration through the surfactant-pretreated filters with singly charged aerosol with that through untreated filters with uncharged aerosol indicates that the former decreases by a factor of 1.8-48.8. The surface fiber charges of the DDAB- and SO-pretreated filters were calculated to be 2.02 x 1(-10) C/m and -1.53 x 10(-1) degrees C/m. Moreover, the aerosol penetrations through the surfactant-pretreated filters increased with the face velocity. Surfactant-pretreated filters performed better against solid aerosol than against liquid aerosol. RH has no effect on aerosol penetration through the surfactant-pretreated filters. Regression equations for Coulombic and dielectrophoretic single-fiber efficiencies in terms of the dimensionless parameters could be fitted by the experimental measurements of surfactant-pretreated filters in this work.     

Sex in the tropics: reproduction of<Emphasis Type="Italic"> Chthamalus malayensis</Emphasis> Pilsbury (Class Cirripedia) at the equator

The reproduction of a key intertidal space occupier, the barnacle, Chthamalus malayensis, was examined over a 13-month period. The reproductive cycle of C. malayensis was studied at three shores (Singapore, east and west coast of Malaysia) near the centre of its geographical range. Testes, vesiculae seminales, ovaries and embryos were scored for their stages of development. Although, in general, C. malayensis contained gonads throughout the year, the timing and level of peak development varied between the three shores. Embryos were present throughout the year in west Malaysia but were absent for 4–5 months in east Malaysia (June–August and October) and Singapore (February, April and August). Variations in the reproductive cycles and brooding were not clearly linked to the timing of monsoons. The lack of seasonal peaks in breeding may be attributed to the relatively constant climatic conditions experienced near the equator.Communicated by M. S. Johnson, Crawley     

GENERATING DESIGN HYDROGRAPHS BY DEM ASSISTED GEOMORPHIC RUNOFF SIMULATION: A CASE STUDY1

ABSTRACT: The geomorphic instantaneous unit hydrograph (GIUH) may be one of the most successful methodologies for predicting flow characteristics in ungauged watersheds. However, one difficulty in applying the GIUH model is determination of travel time, and the other difficulty is the large amount of geomorphologic information required in the study watershed. Recently, using the kinematic-wave theory Lee and Yen (1997) have analytically determined the travel times for overland and channel flows in watersheds. The limitation of using an empirical velocity equation to estimate the runoff travel time for a specified watershed is then relaxed. To simplify the time-consuming work involved in geomorphic parameter measurement on topographic maps, the GIUH model is linked with geographic information systems to obtain geomorphic parameters from digital elevation models. In this paper, a case study performed for peak flow analysis in an ungauged watershed is presented. The geomorphic characteristics of the study watershed were analyzed using a digital elevation model and were used to construct the runoff simulation model. The design storm was then applied to the geomorphic runoff simulation model to obtain the design hydrograph. The analytical procedures proposed in this study can provide a convenient way for hydrologists to estimate hydrograph characteristics based on limited hydrologic information.