Impact of adaptive comfort criteria and heat waves on optimal building thermal mass control

This article investigates building thermal mass control of commercial buildings to reduce utility costs with a particular emphasis on the individual impacts of both adaptive comfort criteria and of heat waves. Recent changes in international standards on thermal comfort for indoor environments allow for adaptation to the weather development as manifested in comfort criteria prEN 15251.2005 and NPR-CR 1752.2005 relative to the non-adaptive comfort criterion ISO 7730.2003. Furthermore, since extreme weather patterns tend to occur more frequently, even in moderate climate zones, it is of interest how a building's passive thermal storage inventory responds to prolonged heat waves. The individual and compounded effects of adaptive comfort criteria and heat waves on the conventional and optimal operation of a prototypical office building are investigated for the particularly hot month of August 2003 in Freiburg, Germany. It is found that operating commercial buildings using adaptive comfort criteria strongly reduces total cooling loads and associated building systems energy consumption under conventional and building thermal mass control. In the case of conventional control, total operating cost reductions follow the cooling loads reductions closely. Conversely, the use of adaptive comfort criteria under optimal building thermal mass control leads to both lower and slightly higher absolute operating costs compared to the optimal costs for the non-adaptive ISO 7730. While heat waves strongly affect the peak cooling loads under both conventional and optimal building thermal mass control, total cooling loads, building energy consumption and costs are only weakly affected for both control modes. Passive cooling under cost-optimal control, while achieving significant total cost reductions of up to 13%, is associated with total energy penalties on the order of 1–3% relative to conventional nighttime setup control. Thus, building thermal mass control defends its cost saving potential under optimal control in the presence of adaptive comfort criteria and heat waves.     

Phase Transformations and Grain Growth in β-stabilized TiAl Alloys

Solid-state phase transformations and grain growth of an intermetallic γ-TiAl alloy were investigated in-situ using high-temperature laser scanning confocal microscopy (HTLSCM). During isothermal annealing in the single β-phase region, significant grain coarsening was observed. On cooling beneath the β-transus temperature with different rates, a CCT diagram was evaluated for the initiation of β to α phase transformation and changes in the morphology were observed.     

Einfluss von Aluminium auf die Karbidbildung im Schnellarbeitsstahl

Aluminum as an alloying element in high-speed steel was investigated for the first time during the Second World War at the Montanuniversität Leoben. At this time there was an enormous consumption or rather a shortage of molybdenum and especially of tungsten worldwide. Tungsten was not only used for the high-speed steel production but was also very much needed for the war industry. Attempts were made in order to replace these alloying elements in high-speed steels with cheaper elements. It was found that a certain percentage of tungsten and molybdenum in high-speed steel can be replaced or substituted by an aluminium content of 0.3 up to 1.4 mass-% without any loss of cutting performance. However, no detailed metallurgical investigations were carried out to explain and clarify this behaviour of aluminium. The influence of aluminium in high-speed steels is highly controversial, due to the fact that aluminium compared to tungsten and molybdenum is not a carbide-forming element, but the special properties of high-speed steels are mainly gained by the presence of carbides. Despite several works in this field, there is no clear understanding of how aluminium can affect the properties of high-speed steel. In the present work, standard and modern examination methods, such as scanning electron microscope, energy dispersive X-ray spectroscopy, and atom probe tomography, were used to investigate the effect of aluminium on the primary and secondary hardening carbides in high-speed steels. The investigations were conducted on three high-speed steel grades with varying the aluminium content only.     

Book reviews

Australian Urban Planning: New Challenges, New Agendas. Brendan Gleeson and Nicholas Low. Allen & Unwin, Sydney, 2000. ISBN 1865082384 (paperback). 273 pp.; bibliography and index. RRP $35.00.

Australian Urban Planning: New Challenges, New Agendas. Review 2.

Equity, Environment, Efficiency: Ethics and Economics in Urban Australia. Patrick Troy (ed.). Melbourne University Press, Melbourne, 2000. ISBN 0522848923 (paperback). 255pp.; bibliography and index. RRP $43.95.

Asian New Urbanism. William S. W. Lim. Select Books, Singapore, 1998. ISBN 9814022012. 250 pp.. RRP $52.00.

Rethinking Australian Citizenship. Wayne Hudson and John Kane (eds). Cambridge University Press, Cambridge, 2000. ISBN 052159670 (paperback), 052159337 9 (hardback). 274pp.; bibliography and index. RRP $34.95 (paperback), $90.00 (hardback).

Community Participation Methods in Design and Planning. Henry Sanoff. John Wiley, New York, 2000. ISBN 0471355453. 306 pp.; bibliography, additional readings and index. RRP $114.95.

Global Spin: The Corporate Assault on Environmentalism. Sharon Beder. Scribe, Melbourne, rev. edn, 2000. ISBN 090801144 (paperback). 336 pp; bibliography and index. RRP $29.95.     

A tool to evaluate the fertiliser value and the environmental impact of substrates from wastewater treatment.

Fertilisers may contain pollutants that are applied to the field together with the nutrients. Comparing fertilisers is difficult because of their different concentrations of nutrients and pollutants. In this study an already existing model was taken. It was further developed to compare nutrient fluxes (N, P, K, Ca, Mg, S, humus) and pollutants (heavy metals and pharmaceuticals) of pig and cattle slurry as well as human urine. The data used is taken from literature and, in the case of pharmaceuticals in urine, daily excretion rates were calculated. An amount of 19 m3 ha(-1) a(-1) undiluted urine can be applied, limiting factor is sulphur. Without taking over-fertilisation into account, an addition of mineral fertiliser is required to any organic fertiliser application. In general, heavy metal, antibiotic, and hormone fluxes are higher by using animal manure then urine as fertiliser. However, additional loads of other pharmaceuticals consumed by humans have to be considered. Overall, the model is a suitable tool worthwhile to be extended in aspects of hygiene, environmental impacts as for example, degradation processes as well as ecotoxicology.     

Coupled distance sensor systems for high-accuracy topography measurement: Accounting for scanning stage and systematic sensor errors

Scanning topography measurements using systems of coupled distance sensors suffer from the presence of scanning stage and systematic sensor errors. While scanning stage errors can be estimated for suitably-designed sensor systems, it is usually not possible to simultaneously estimate both scanning stage and systematic sensor errors. Additional angular scanning stage measurements can solve this problem, and potentials and limitations of such a proceeding will be assessed.It is shown that perfect topography reconstruction can be achieved in the presence of systematic sensor and certain scanning stage errors provided that the measurements are noise-free and no further systematic errors emerge. In general, the topography is reconstructed by the application of least-squares, and the uncertainty associated with the reconstructed topography is derived. Resulting topography accuracies are evaluated for different noise levels of the distance sensor and angular scanning stage measurements, and practical considerations are discussed. The gain in accuracy due to accounting for scanning stage and systematic sensor errors can be large, and high accuracies can be reached.     

Detailed observation and measurement of sewer sediment erosion under aerobic and anaerobic conditions.

A greater understanding of the erosion behaviour of sewer sediments is necessary in order to reliably estimate the amount and nature of the sewer sediments released from deposits in sewers and transported either to waste water treatment plants or discharged into the environment. Research has indicated that microbial activity in sediment can influence the physical release of sediment from in-pipe deposits. This paper reports on a series of erosion tests in which sewer sediments from different sewer networks are kept under different environmental conditions and their resistance to erosion is examined. The erosion tests are carried out under aerobic and anaerobic conditions and two temperatures, one representing ambient sewer temperatures and a lower temperature that significantly suppresses bacterial activity.     

Impact of dimension uncertainty and model calibration on sewer system assessment.

Assessments of sewer performance are usually based on a single computation of CSO (combined sewer overflow) volumes using a time series of rainfall as system loads. A shortcoming of this method is that uncertainties in knowledge of sewer system dimensions are not taken into account. Moreover, sewer models are rarely calibrated. This paper presents the impacts of database errors and model calibration on return periods of calculated CSO volumes. The impact of uncertainties is illustrated with two examples. Variability of calculated CSO volumes is estimated using Monte Carlo simulations. The results show that calculated CSO volumes vary considerably due to database errors, especially uncertain dimensions of the catchment area. Furthermore, event-based calibration of a sewer model does not result in more reliable predictions because the calibrated parameters have low portability. However, it enables removal of database errors harmonising model predictions and 'reality'.