Analyzing the Effect of Soiling on the Performance of a Photovoltaic System of Different Module Technologies in Kalkbult, South Africa

The fact that most of the large scale solar PV plants are built in arid and semi-arid areas where land availability and solar radiation is high, it is expected the performance of the PV plants in such locations will be affected significantly due to high cell temperature as well as due to soiling. Therefore, it is essential to study how the different PV module technologies will perform in such geographical locations to ensure a consistent and reliable power delivery over the lifetime of the PV power plants. As soiling is strongly dependent on the climatic conditions of a particular location a test station, consisted of about 24 PV modules and a well-equipped weather station, was built within the fences of Scatec’s 75 MW Kalkbult solar PV plant in South Africa. This study was performed to a better understand the effect of soiling by comparing the relative power generation by the cleaned modules to the un-cleaned modules. Such knowledge can enable more quantitative evaluations of the cleaning strategies that are going to be implemented in bigger solar PV power plants. The data collected and recorded from the test station has been analyzed at IFE, Norway using a MatLab script written for this thesis project. This thesis work has been done at IFE, Norway in collaboration with Stellenbosch University in South Africa and Scatec Solar a Norwegian independent power producer company. Generally for the polycrystalline modules it is found that the average temperature corrected efficiency during the period of the experiment has been 15.00±0.08 % and for the thin film-CdTe with ARC is 11.52% and for the thin film without ARC is about 11.13% with standard uncertainty of ±0.01 %. Besides, by comparing the initial relative average efficiency of the polycrystalline-Si modules when all the modules have been cleaned for the first time and the final relative efficiency; after the last cleaning schedule which is when all the reference modules E, F, G, and H have been cleaned for the last time it is found that poly3 performs 2 % and 3 % better than poly1 and poly16 respectively, poly13 performs 1 % better than poly15 as well as poly5 and poly12 performs 1 % and 2 % better than poly10 respectively. Besides, poly5 and poly12 performs a 9 % and 11 % better than poly7. Furthermore, there is no change in performance between poly6 and poly9 as well as poly4 and poly15. However, the increase in performance of poly3 to poly1, poly13 to poly15 as well as poly5 and poly12 to poly10 is insignificant. In addition, it is found that TF22 perform 7% better than the reference un-cleaned module TF24 and similarly; TF21 performs 7% higher than TF23. Furthermore, modules with ARC glass (TF17, TF18, TF19, and TF20) shows that cleaning the modules with only distilled water (TF19) or dry-cleaned after cleaned with distilled water(TF20) decreases the performance of the modules by 5 % and 4 % comparing to its respective reference uncleanedmodules TF17 and TF18 respectively.

Rapport från/Report from IEA Task-14 mötet/meeting on solar heating system, Hameln Tyskland/Germany August 1992

Participation as observer at the meeting of Task 14 of IEA's Solar Heating and Cooling Projects held in Hameln, Germany has led to greater understanding of interesting developments underway in several countries. This will be of use during the development of small scale systems suitable for Swedish conditions. A summary of the work carried out by the working groups within Task 14 is given, with emphasis on the Domestic Hot Water group. Experiences of low-flow systems from several countries are related, and the conclusion is drawn that the maximum theoretical possible increase in performance of 20% has not been achieved due to poor heat exchangers and poor stratification in the storage tanks. Positive developments in connecting tubes and pumps is noted. Further participation as observer in Task 14 meetings is desired, and is looked on favourably by the members of the group. Another conclusion is that SERC should carry on with work on Swedish storage tanks, with emphasis on better stratification and heat exchangers, and possible modelling of system components. Finally a German Do-it-Vourself kit is described and judged in comparison with prefabricated models and Swedish Do-it-Yourself kits.

Provningsmetod för integrerade sol-biosystem : Årsverkningsgrad genom korttidsmätning

Test method for integrated solar- biomass systems - Long term prediction trough short term measurementsSP Technical Research Institute of Sweden and SERC, Dalarna University have in cooperation developed a test method for integrated solar and biomass systems. The test method is performed under six days including two summer days, two winter days and two spring/autumn days true to real weather conditions and loads for a single family house. The aim of the test method is to get information about a Combisystem’s annual performance and operation throughout a short term test. Seven different solar Combisystems have been tested within the project together with a pellet boiler without solar collectors. In addition to that a comparative testing has been performed at the two laboratories at SP and at SERC on the same Combisystem. The test method developed within the project has been proved to withstand the aim of the project, which is to be able to compare the performance between the systems. The test method is also suitable for identification of possible operation problems so they can be taken care of and consequently improves the system.The project and the system testing reveal that it is in general favorable to combine biomass pellets with solar heating. Pellet boilers has normally a low performance during the summer period but combined with a solar collector the boiler can be switch off during this period. There are however big differences in performance between the tested. The efficiency of the pellet boiler is highly dependent of the operating conditions and elements like heat losses from the system, system configuration and control strategy have great influence of the performance of the system and the emissions. On the other hand, the performance and the size of the solar collectors have a minor effect on the overall system performance. There is obviously a big potential for improvement of the system´s performance and the developed test method is an essential way to implement this perfection.

Genetic Heteroscedasticity for Domestic Animal Traits

Animal traits differ not only in mean, but also in variation around the mean. For instance, one sire’s daughter group may be very homogeneous, while another sire’s daughters are much more heterogeneous in performance. The difference in residual variance can partially be explained by genetic differences. Models for such genetic heterogeneity of environmental variance include genetic effects for the mean and residual variance, and a correlation between the genetic effects for the mean and residual variance to measure how the residual variance might vary with the mean. The aim of this thesis was to develop a method based on double hierarchical generalized linear models for estimating genetic heteroscedasticity, and to apply it on four traits in two domestic animal species; teat count and litter size in pigs, and milk production and somatic cell count in dairy cows. The method developed is fast and has been implemented in software that is widely used in animal breeding, which makes it convenient to use. It is based on an approximation of double hierarchical generalized linear models by normal distributions. When having repeated observations on individuals or genetic groups, the estimates were found to be unbiased. For the traits studied, the estimated heritability values for the mean and the residual variance, and the genetic coefficients of variation, were found in the usual ranges reported. The genetic correlation between mean and residual variance was estimated for the pig traits only, and was found to be favorable for litter size, but unfavorable for teat count.

Homosocialitetens kraft : hur unga män ”gör” maskulinitet i grupp och individuellt

The power of homosociality: how young men “do” masculinity in groups and individually Using young men’s narratives, about other men, friends, dates and girlfriends, this article discusses the following questions: Can the interpretation – the understanding of young men’s collective presentations of masculinity as a surface that hides a more complex masculinity – undermine how we interpret young men’s talk about and interaction with other men, as well as with women? Can this disassembling understanding have an impact on how young men interpret and relive the interactions with other men, as well as with women? Can this disassembling of the homosocially created masculinity from the more individually created masculinity shape secondary gains for the young men, such as e.g. a more flexible and stretchable arena of responsibility, as well as more flexible space of acting? Thomas Johansson, Professor of Social Work social work, states that if we only focus the homosocially created masculinity, this will reshape a less nuanced picture of young men’s way of doing masculinity (Johansson 2005). Thus, young men’s vulnerability and difficulties remain hidden. However, this disassembling of the homosocially created masculinity from the more individually based doings of masculinity could possibly also give secondary gains, such as e.g. a more flexible and stretchable field of responsibility, as well as more flexible space of acting. This article shows that using a fragmentised and situated masculinity, as a way of understanding the complexity and the ambivalence in young men’s project of doing masculinity, makes evident – on the one hand – the vulnerability in young men’s process of doing masculinity. On the other hand, however, this view also makes it possible for young men to avoid responsibility for their actions. Instead the situated context – e.g. if in a peer group or alone, and what kind of relations the young man has – will be significant for how the act will be interpreted. The empirical material consists of six individual interviews and one group interview with four men. The age span of the participants is 16 to 24 years old. The overall theme for the discussions is heterosexual practice and relations.

Gränsdragning mellan arbete & fritid : Närvaro i sin frånvaro

Vårt syfte med denna studie är att ämna beskriva vilken betydelse det gränslösa arbetet får för chefsrollen, utifrån de förändringar som sker i dagens arbetsliv samt hur gränsdragningen mellan arbete och fritid hanteras. Vi valde att utföra vår studie i form av kvalitativa intervjuer, där vi intervjuade sex medarbetare inom en offentlig organisation i Dalarna, Sverige. Det resultat vi erhöll analyserades utifrån tidigare forskning och teorier. Resultaten i vår studie visar att cheferna direkt eller indirekt påverkas av förändringar som sker i arbetslivet och att det även är något som påverkar hur cheferna hanterar gränsdragningen mellan arbete och fritid. Studiens resultat visar vidare att cheferna menar att dessa förändringar bidrar till att förändra deras sätt att agera i chefsrollen och att det ställer andra krav på deras kompetenser. Resultatet visar också att kraven i arbetet måste vara rimliga, för att skapa balans mellan arbets- och privatliv och att det i första hand inte är de kvantitativa faktorerna i förhållande till arbetet som skapar en upplevelse av gränslöshet. Med kvantitativa faktorer menar vi de faktorer som traditionellt beskrivs som mer konkreta faktorer i arbetet, exempelvis arbetets utformning, arbetstiden, tillgängligheten eller antalet arbetsuppgifter att utföra. Istället belyser resultatet att en emotionell känsla av stress kan uppstå i relation till den egna upplevelsen av en känslig situation i arbetet eller när den egna kompetensen inte räcker till i arbetsutförandet och att det kan skapa en otydlig gräns mellan arbetstid och fritid.