Load and Season Adapted Solar Collectors

In Sweden solar irradiation and space heating loads are unevenly distributed over the year. Domestic hot water loads may be nearly constant. Test results on solar collector performance are often reported as yearly output of a certain collector at fixed temperatures, e g 25, 50 and 75 C. These data are not suitable for dimensioning of solar systems, because the actual performance of the collector depends heavily on solar fraction and load distribution over the year.At higher latitudes it is difficult to attain high solar fractions for buildings, due to overheating in summer and small marginal output for added collector area. Solar collectors with internal reflectors offer possibilities to evade overheating problems and deliver more energy at seasons when the load is higher. There are methods for estimating the yearly angular irradiation distribution, but there is a lack of methods for describing the load and the storage in such a way as to enable optical design of season and load adapted collectors.This report describes two methods for estimation of solar system performance with relevance for season and load adaption. Results regarding attainable solar fractions as a function of collector features, load profiles, load levels and storage characteristics are reported. The first method uses monthly collector output data at fixed temperatures from the simulation program MINSUN for estimating solar fractions for different load profiles and load levels. The load level is defined as estimated yearly collector output at constant collector temperature divided be yearly load. This table may examplify the results:CollectorLoadLoadSolar Improvementtypeprofile levelfractionover flat plateFlat plateDHW 75 %59 %Load adaptedDHW 75 %66 %12 %Flat plateSpace heating 50 %22 %Load adaptedSpace heating 50 %28 %29 %The second method utilises simulations with one-hour timesteps for collectors connected to a simplified storage and a variable load. Collector output, optical and thermal losses, heat overproduction, load level and storage temperature are presented as functions of solar incidence angles. These data are suitable for optical design of load adapted solar collectors. Results for a Stockholm location indicate that a solar combisystem with a solar fraction around 30 % should have collectors that reduce heat production at solar heights above 30 degrees and have optimum efficiency for solar heights between 8 and 30 degrees.

Load Adapted Solar Thermal Combisystems - Optical Analysis and Systems Optimization

In a northern European climate a typical solar combisystem for a single family house normally saves between 10 and 30 % of the auxiliary energy needed for space heating and domestic water heating. It is considered uneconomical to dimension systems for higher energy savings. Overheating problems may also occur. One way of avoiding these problems is to use a collector that is designed so that it has a low optical efficiency in summer, when the solar elevation is high and the load is small, and a high optical efficiency in early spring and late fall when the solar elevation is low and the load is large.The study investigates the possibilities to design the system and, in particular, the collector optics, in order to match the system performance with the yearly variations of the heating load and the solar irradiation. It seems possible to design practically viable load adapted collectors, and to use them for whole roofs ( 40 m2) without causing more overheating stress on the system than with a standard 10 m2 system. The load adapted collectors collect roughly as much energy per unit area as flat plate collectors, but they may be produced at a lower cost due to lower material costs. There is an additional potential for a cost reduction since it is possible to design the load adapted collector for low stagnation temperatures making it possible to use less expensive materials. One and the same collector design is suitable for a wide range of system sizes and roof inclinations. The report contains descriptions of optimized collector designs, properties of realistic collectors, and results of calculations of system output, stagnation performance and cost performance. Appropriate computer tools for optical analysis, optimization of collectors in systems and a very fast simulation model have been developed.

Solvärmesystem för hög täckningsgrad - Load adapted concentrating collectors for high solar fractions

Dagens kombisolvärmesystem för enfamiljshus har i storleksordningen 10 m2 solfångare och kan täcka i runda tal 10 ? 30 % av det årliga värmebehovet. Ökar man solfångarytan för att öka solvärmetäckningsgraden uppstår det vanligtvis en överproduktion av värme sommartid viket kan orsaka problem i form av termisk utmattning av material, att material förstörs eller att säkerhetsventiler utlöses med driftsstopp som följd. Vidare förkortas glykolens livslängd radikalt och detta kan ge följdskador såsom korrosion, beläggningar i rören och t o m igensättning av systemet. Ett sätt att undvika problemen med överhettning i solvärmesystem med hög täckningsgrad är att använda lastanpassade solfångare. Med detta menas solfångare som har en verkningsgrad som är beroende av solhöjden och varierar över året. Verkningsgraden är hög när värmelasten är hög (vanligtvis sen höst, vinter och tidig vår) medan verkningsgraden är låg då värmelasten är låg (vanligtvis sen vår, sommar och tidig höst). I denna rapport visas att det är möjligt att bygga lastanpassade solfångarsystem med hög täckningsgrad för enfamiljshus med solfångarytor som täcker hela villatak (>= 40 m2), utan att den termiska påfrestningen på systemet blir större än för vanliga solvärmesystem med 10 m2 plana solfångare. Detta kan göras med samma systemkomponenter som finns i system med plana solfångare. De lastanpassade solfångarna levererar ungefär samma energimängd per m2 som plana solfångare, men de bör kunna bli billigare, på grund av lägre materialkostnad. Det finns även en potential att konstruera lastanpassade solvärmesystem med begränsad stagnationstemperatur, vilket kan möjliggöra användandet av billigare material. En och samma solfångartyp är lämplig för såväl stora som små system och för olika takvinklar. I rapporten redovisas optimerade solfångargeometrier för lastanpassade solvärmesystem, geometrier och optiska egenskaper för praktiskt möjliga solfångare samt beräkningar av förväntat årsutbyte, stagnationstemperaturer, stagnationstider och kostnader. Testresultat för två prototyper av lastanpassade solfångare presenteras. Optimeringsalgoritmer för design av optiken för lastanpassade solfångare i system samt ett ray-tracingverktyg och snabba men ändå tillräckligt noggranna simuleringsverktyg har utvecklats.

Healthcare providers balancing norms and practice : challenges and opportunities in providing contraceptive counselling to young people in Uganda - a qualitative study

BACKGROUND: Pregnancies among young women force girls to compromise education, resulting in low educational attainment with subsequent poverty and vulnerability. A pronounced focus is needed on contraceptive use, pregnancy, and unsafe abortion among young women. OBJECTIVE: This study aims to explore healthcare providers' (HCPs) perceptions and practices regarding contraceptive counselling to young people. DESIGN: We conducted 27 in-depth interviews with doctors and midwives working in seven health facilities in central Uganda. Interviews were open-ended and allowed the participant to speak freely on certain topics. We used a topic guide to cover areas topics of interest focusing on post-abortion care (PAC) but also covering contraceptive counselling. Transcripts were transcribed verbatim and data were analysed using thematic analysis. RESULTS: The main theme, HCPs' ambivalence to providing contraceptive counselling to sexually active young people is based on two sub-themes describing the challenges of contraceptive counselling: A) HCPs echo the societal norms regarding sexual practice among young people, while at the same time our findings B) highlights the opportunities resulting from providers pragmatic approach to contraceptive counselling to young women. Providers expressed a self-identified lack of skill, limited resources, and inadequate support from the health system to successfully provide appropriate services to young people. They felt frustrated with the consultations, especially when meeting young women seeking PAC. CONCLUSIONS: Despite existing policies for young people's sexual and reproductive health in Uganda, HCPs are not sufficiently equipped to provide adequate contraceptive counselling to young people. Instead, HCPs are left in between the negative influence of social norms and their pragmatic approach to address the needs of young people, especially those seeking PAC. We argue that a clear policy supported by a clear strategy with practical guidelines should be implemented alongside in-service training including value clarification and attitude transformation to equip providers to be able to better cater to young people seeking sexual and reproductive health advice.

Balancing the risk of injury to gymnasts : how effective are the counter measures?

Background—To minimise injury risk and maximise gymnastics performance, coaches, parents, and health professionals working with young gymnasts need to understand and practise safe gymnastics.

Aims—To (a) identify the various injury counter measures specific to gymnastics, (b) critically review the literature describing each injury prevention measure, and (c) assess, using available risk factor and injury data, the weight of evidence to support each of these counter measures. Specific recommendations for further research and implementation strategies to prevent injury and improve safety are also given.

Methods—The relevant literature was identified through the use of Medline (1966 to May 1998) and SPORT Discus (1975 to May 1998) searches, hand searching of journals and reference lists, and discussions with key Australian gymnastics organisations.

Results—The key gymnastics injury counter measures identified in this review include coaching (physical preparation, education, spotting, and performance technique), equipment, and the health support system (medical screening, treatment, and rehabilitation). Categorisation of the type of evidence for the effectiveness of each of these counter measures in preventing injury showed that most of it is based on informal opinion/anecdotal evidence, uncontrolled data based studies, and several prospective epidemiological studies. There is no evidence from formally controlled trials or specific evaluation studies of counter measures for gymnastics.

Conclusions—Although gymnastics is a sport associated with young participants and frequent high volume, high impact training, there is a paucity of information on injury risk factors and the effectiveness of injury practices. Further controlled trials are needed to examine the extent to which injury prevention counter measures can prevent or reduce the occurrence of injury and re-injury. Particular attention should be devoted to improving training facilities, the design and testing of apparatus and personal equipment used by gymnasts, and coaching and the role of spotting in preventing injury.

Monitoring employees' email and internet use at work : balancing the interests of employers and employees.

The increased use of email and the internet in the workplace raises important legal questions for workers and employers. The purpose of this paper is to  explore some of the legal implications of use by employees of workplace email and internet systems, with particular focus on employer monitoring of the use of email and internet and its implications for employee privacy.

Multi-temporal land use mapping using remotely sensed techniques and the integration of a pollutant load model in a GIS

Estimation of nutrient load production based on multi-temporal remotely sensed land-use data for the Glenelg-Hopkins region in southwest Victoria, Australia, is discussed. Changes in land use were mapped using archived Landsat data and computerized classification techniques. Land-use
change is unparalleled in recent history, with 13% of the region transformed in the last decade. Total nitrogen and phosphorus loading were estimated using an export coefficient model. The analysis demonstrated a disturbing increase in nitrogen and phosphorus loadings from 1995 to 2002. Whilst such increases were suspected from past anecdotal and ad-hoc evidence, our modelling quantitatively estimated such increases and thus demonstrated the enormous potential of using remote sensing and GIS for monitoring land-use change and hence improve land-use management.

Balancing environmental impacts and benefits of wastewater reuse

Wastewater reuse is being widely promulgated to help address the global freshwater resource crisis. It can assist in reducing extraction of freshwater from the environment, and reuse of wastewater lessens the need for environmental discharge, which is clearly beneficial to receiving waters. But the practice itself also has the potential to be detrimental to natural and human environments: soil structure can become degraded, aquifers may be polluted, and human health may be threatened. The challenge facing natural resource managers is to identify the potential benefits and risks, and to achieve an appropriate balance. This paper describes environmental benefits and threats concomitant with the reuse of wastewater. We frequently draw upon examples from China and Australia-two countries that face particularly daunting water resource
challenges-but the principles can be.extended far beyond these geographical bounds and are applicable to
many parts of the world.

Balancing continuity and change through forms of organising

Faced with increasing environmental complexity and uncertainty, organisations have been urged to replace traditional bureaucratic structures with more flexible, responsive forms of organising. However, the emerging paradox is that exploration and experimentation, features of new forms of organising, benefit from the planning, coordinating and direction-setting mechanisms that underpin traditional forms of organising. It is therefore important to recognise the distinctive and complementary features of traditional and new forms of organising. This demands a dualities-sensitive perspective which encourages, rather than tries to resolve, a constructive tension between seemingly contradictory organising forms such as flexibility and efficiency, autonomy and control, hierarchy and networks, focus and diversification. Managing continuity and change through forms of organising becomes central to building healthy organisations.

Adaptive load shedding for mining frequent patterns from data streams

Most algorithms that focus on discovering frequent patterns from data streams assumed that the machinery is capable of managing all the incoming transactions without any delay; or without the need to drop transactions. However, this assumption is often impractical due to the inherent characteristics of data stream environments. Especially under high load conditions, there is often a shortage of system resources to process the incoming transactions. This causes unwanted latencies that in turn, affects the applicability of the data mining models produced – which often has a small window of opportunity. We propose a load shedding algorithm to address this issue. The algorithm adaptively detects overload situations and drops transactions from data streams using a probabilistic model. We tested our algorithm on both synthetic and real-life datasets to verify the feasibility of our algorithm.

WIND POWER IN MAINE: BALANCING CONSERVATION AND ENERGY PRODUCTION

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