Change search
Link to record
Permanent link

Direct link
BETA
Stawreberg, Lena
Alternative names
Publications (10 of 12) Show all publications
Renström, R. & Brunzell, L. (2018). En introduktion för att studenter ska utveckla egna strategier för skrivandet. In: Madelaine Johansson, Lena E. Johansson (Ed.), Studentaktiva lärande- och examinationsformer: Bidrag från universitetspedagogisk konferens 2017 (pp. 93-108). Karlstad: Karlstads universitet
Open this publication in new window or tab >>En introduktion för att studenter ska utveckla egna strategier för skrivandet
2018 (Swedish)In: Studentaktiva lärande- och examinationsformer: Bidrag från universitetspedagogisk konferens 2017 / [ed] Madelaine Johansson, Lena E. Johansson, Karlstad: Karlstads universitet, 2018, p. 93-108Chapter in book (Other academic)
Abstract [sv]

I högre utbildning är akademiskt skrivande något som studenter behöver stöd att utveckla genom hela sin utbildning. Handledningen är en central del i denna process men det finns en risk att handledaren i stället för att lyfta halvfärdiga texter i själva verket drar ner studenter eller lämnar otydliga synpunkter. Det finns även en risk att handledaren över skrivarbetet och gör det till sitt.

Vi arbetar med en handledningsmodell som vi kallar ”Direkthandledning”. Modellen ger stor frihet för förändringar och stora delar avutbildningsmiljön arbetar med liknande modeller. Drivkraften är att göra handledningen effektivare, att öka studenternas respons för lärarnas synpunkter samt ge studenterna egna strategier för sitt skrivande. Direkthandledningsmodellen används i hela utbildningen och i denna artikel presenteras introduktionen. I handledningsmodellen separeras innehåll och form. I introduktionen handleds enbart formen, hur rapporten är formaliserad, strukturerad och skriven.I direkthandledningsmodellen får studenten alltid en tydlig process och kravspecifikation på vad som förväntas. I introduktionen genomförs en individuell studie och först när studenten skrivit en inledning, metod och resultat som är i läs- och kommentarbart skick, får studenten handledning. Texten skall då följa en utskickad och kommunicerad mall och struktur. Återkopplingen utgår från kravspecifikationen. När studenten kommer till handledningen har handledare och student en diskussion kring hur arbetet är presenterat, inget annat. Under handledningen får studenten tydlig information om hur denne ligger till i förhållande till kravspecifikationen.

Modellen har lett till betydande förbättringar av responsen på synpunkter. Studenter uppger att de börjat utveckla egna strategier för sitt skrivande.

Place, publisher, year, edition, pages
Karlstad: Karlstads universitet, 2018
Series
Utveckling av undervisning och examination i högre utbildning: utgiven av Universitetspedagogiska enheten vid Karlstads universitet ; 2018:1
National Category
Educational Sciences
Identifiers
urn:nbn:se:kau:diva-72045 (URN)978-91-7063-869-5 (ISBN)978-91-7063-964-7 (ISBN)
Available from: 2019-05-15 Created: 2019-05-15 Last updated: 2019-11-07Bibliographically approved
Brunzell, L. & Renström, R. (2018). Utformning av aktiva pedagogiska möten i en kurs med flippat lärande. In: Madelaine Johansson, Lena E. Johansson (Ed.), Studentaktiva lärande- och examinationsformer: Bidrag från universitetspedagogisk konferens 2017 (pp. 21-34). Karlstad: Karlstads universitet
Open this publication in new window or tab >>Utformning av aktiva pedagogiska möten i en kurs med flippat lärande
2018 (Swedish)In: Studentaktiva lärande- och examinationsformer: Bidrag från universitetspedagogisk konferens 2017 / [ed] Madelaine Johansson, Lena E. Johansson, Karlstad: Karlstads universitet, 2018, p. 21-34Chapter in book (Other academic)
Abstract [sv]

Att använda flippat lärande i undervisningen har blivit mer och mer vanligt i högre utbildning. Studier pekar på att den formen av undervisning leder till ökad förståelse, ett ökat engagemang och motivation hos studenterna. Dock finns ett uttalat behov av ytterligare forskning inom området. I denna studie ligger fokus på hur de pedagogiska mötena i en typisk teknisk grundkurs kan utformas för att vara aktiva och främja lärandet i de högre kunskapsnivåerna. Den nya utformningen bygger på att traditionella möten med studenter såsom föreläsningar och lektioner har bytts ut mot diskussionstillfällen och laborationer. Räkneövningar finns i båda upplägg men fokus i det nya ligger i att arbeta med koncept och hur problem ställs upp. Den operativa räkningen lämnas alltid till studenterna. Resultaten blir att lärarna idag kan möta studenterna och agera som en coach i deras lärande, studenterna är mer aktiva och vi arbetar med kunskapsmål där vi analyserar, kritiskt utvärderar, utformar system och gör avvägda antaganden. Genomströmningen har ökat från mellan 40-50% till mellan 60-70% trots ett ökat krav på förståelsen i examinationen.

Place, publisher, year, edition, pages
Karlstad: Karlstads universitet, 2018
Series
Utveckling av undervisning och examination i högre utbildning: utgiven av Universitetspedagogiska enheten vid Karlstads universitet ; 2018:1
National Category
Educational Sciences
Identifiers
urn:nbn:se:kau:diva-72044 (URN)978-91-7063-869-5 (ISBN)978-91-7063-964-7 (ISBN)
Available from: 2019-05-15 Created: 2019-05-15 Last updated: 2019-11-07Bibliographically approved
Karlsson, J., Stawreberg, L. & Govindarajan, V. (2017). Material-flow analysis, energy analysis, and partial environmental-LCA of a district-heating combined heat and power plant in Sweden. Energy Journal, 144, 31-40
Open this publication in new window or tab >>Material-flow analysis, energy analysis, and partial environmental-LCA of a district-heating combined heat and power plant in Sweden
2017 (English)In: Energy Journal, ISSN 0195-6574, E-ISSN 1944-9089, Vol. 144, p. 31-40Article in journal (Refereed) Published
Abstract [en]

Combined heat and power (CHP) plants are a great improvement over waste-to-energy incineration plants supplying only heat, and power plants supplying only electricity. The primary purpose of a functioning CHP plant however, may be to provide district heating services, and thereby its main output will be heat energy. This paper is a case study commissioned by Karlskoga Energi och Miljö AB (KEMAB in short; Karlskoga Energy and Environment) in the Värmland State of south-central Sweden, and focuses on the functioning of the CHP plant owned and operated by the company. The life-cycles of the fuels used by the CHP – household/industrial waste, bio-oil, light fuel oil, wood waste, wood chips, a slaughterhouse-waste-derived product and peat to generate 202,222 MWh of heat, 119,234 MWh of steam and 28,220 MWh of electricity have been studied, and the carbon footprint calculated for year-2016. Using two sets of emissions factors for the combustion stage of the life-cycle, as part of a data uncertainty analysis, the total emissions were 44,000 tonnes carbon dioxide equivalents (CO2-eq) and 58,000 tonnes CO2-eq respectively. A quasi-realistic scenario analysis in which plastics are not available for incineration and have to be substituted with alternatives has also been carried out, and while wood waste has been suggested as the best alternative with regard to greenhouse gas (GHG) emissions, availability permitting, a combination of alternatives has been mooted as the practical option.

Place, publisher, year, edition, pages
Elsevier, 2017
Keywords
Combined Heat and Power, District Heating, MFA, LCA
National Category
Engineering and Technology
Research subject
Environmental and Energy Systems
Identifiers
urn:nbn:se:kau:diva-65302 (URN)10.1016/j.energy.2017.11.159 (DOI)000425561500004 ()
Available from: 2017-11-30 Created: 2017-11-30 Last updated: 2019-08-02Bibliographically approved
Stawreberg, L. & Nilsson, L. (2013). Potential Energy Savings Made by Using a Specific Control Strategy when Tumble Drying Small Loads. Applied Energy, 102, 484-491
Open this publication in new window or tab >>Potential Energy Savings Made by Using a Specific Control Strategy when Tumble Drying Small Loads
2013 (English)In: Applied Energy, ISSN 0306-2619, E-ISSN 1872-9118, Vol. 102, p. 484-491Article in journal (Refereed) Published
Abstract [en]

Tumble dryers manufactured today are optimised for their maximum capacity, i.e., 6–8 kg of dry load. An average washing load in ordinary households lands at between 2 and 3.5 kg dry load, which implies that the drying load is even smaller. The energy efficiency decreases with reduced drying load. The aim of this study is to establish a mathematical model for studying alternative control strategies for the venting tumble dryer in order to increase the energy efficiency of drying small loads. Two series of test runs were performed: the first series with three different drying loads was used as reference tests for validation of the mathematical model, and the second series was performed with airflow reduction. The model shows good agreement with the test runs. Two control strategies were tested using the model on the smallest drying load. By lowering the heat supply to the heater and by reducing the airflow, the energy efficiency increases by 6% in a small load drying cycle. It was not possible, however, for the investigated dryer, to reach the same energy efficiency for small loads as for the maximum drying load by using a control strategy.

National Category
Energy Systems
Research subject
Environmental and Energy Systems
Identifiers
urn:nbn:se:kau:diva-8245 (URN)10.1016/j.apenergy.2012.07.045 (DOI)000314190800054 ()
Available from: 2011-09-14 Created: 2011-09-14 Last updated: 2017-12-08Bibliographically approved
Renström, R., Berghel, J., Frodeson, S., Granström, K., Nilsson, L., Lestelius, M., . . . Stawreberg, L. (2013). The drying process from a product perspective. In: : . Paper presented at Nordic Drying Conference - NDC, Copenhagen, Danmark 5-7 juni 2013.
Open this publication in new window or tab >>The drying process from a product perspective
Show others...
2013 (English)Conference paper, Published paper (Refereed)
National Category
Energy Engineering
Research subject
Energy Technology
Identifiers
urn:nbn:se:kau:diva-29707 (URN)
Conference
Nordic Drying Conference - NDC, Copenhagen, Danmark 5-7 juni 2013
Available from: 2013-10-21 Created: 2013-10-18 Last updated: 2018-04-16Bibliographically approved
Stawreberg, L., Berghel, J. & Renström, R. (2012). Energy Losses by Air Leakage in Condensing Tumble Dryers. Applied Thermal Engineering, 37(May), 373-379
Open this publication in new window or tab >>Energy Losses by Air Leakage in Condensing Tumble Dryers
2012 (English)In: Applied Thermal Engineering, ISSN 1359-4311, E-ISSN 1873-5606, Vol. 37, no May, p. 373-379Article in journal (Refereed) Published
Abstract [en]

Tumble dryers, used for the drying of textiles, consume a considerable amount of electricity due to the large number of dryers in use. A large amount of this electricity is produced from coal, making it important to reduce the electricity use and, hence, the carbon dioxide emissions. Earlier studies made on the condensing tumble dryer have pointed out that leakage is one of the parameters affecting the electricity use for the drying process. With a view to reducing the energy use, leakage was estimated through measurements and modelling. Energy balances were used in order to verify the leakage. The energy balance showed good agreement with the results from the model and confirms that the leakage out from the dryer arises mainly between the heater and the drum where the air is hot and has low relative humidity. Large leakage at this location is detrimental for the energy efficiency of the dryer, meaning that the leakage must be reduced in order to obtain a reduced energy use. Results from the model also point out that even small changes in the size of gaps, or changes to the pressure in the internal system, result in a significant change in leakage from the dryer

Place, publisher, year, edition, pages
Elsevier, 2012
Keywords
Energy balance, Tumble dryer, Leakage, Textile, Domestic
National Category
Energy Systems
Research subject
Environmental and Energy Systems
Identifiers
urn:nbn:se:kau:diva-8246 (URN)10.1016/j.applthermaleng.2011.11.051 (DOI)000301026600045 ()
Available from: 2011-09-14 Created: 2011-09-14 Last updated: 2017-12-08Bibliographically approved
Stawreberg, L. & Wikström, F. (2011). Does the energy labelling system for domestic tumble dryers serve its purpose?. Journal of Cleaner Production, 19, 1300-1305
Open this publication in new window or tab >>Does the energy labelling system for domestic tumble dryers serve its purpose?
2011 (English)In: Journal of Cleaner Production, ISSN 0959-6526, E-ISSN 1879-1786, Vol. 19, p. 1300-1305Article in journal (Refereed) Published
National Category
Energy Systems
Research subject
Environmental and Energy Systems
Identifiers
urn:nbn:se:kau:diva-8243 (URN)10.1016/j.jclepro.2011.03.016 (DOI)000292716800003 ()
Available from: 2011-09-14 Created: 2011-09-14 Last updated: 2017-12-08Bibliographically approved
Stawreberg, L. (2011). Energy Efficiency Improvements of Tumble Dryers: -Technical Development, Laundry Habits and Energy Labelling. (Doctoral dissertation). Karlstad: Karlstad University
Open this publication in new window or tab >>Energy Efficiency Improvements of Tumble Dryers: -Technical Development, Laundry Habits and Energy Labelling
2011 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Tumble dryers are becoming more and more common in ordinary households as a complement to the washing machine. Tumble dryers offer a fast drying cycle independent on weather conditions and require small space. They do, however, considering the large number of units use a large amount of electricity. The main objective in this thesis is to identify possibilities in order to reach a reduced electricity use for domestic tumble-drying of clothes. This involves an investigation of the condensing tumble dryer in order to point out possible energy efficiency improvements. The purpose of the energy label, which indicates the energy efficiency of the tumble dryer, is also studied, whether it matches the actual laundry habits. Finally, suggestions for technical development of the tumble dryer are made in line with today’s consumer behaviour.

The performance of the condensing tumble dryer has been studied using a design of experiments to create a statistical model in Paper I. This model was used to find the best settings for the power supply to the heater, the internal airflow and the external airflow in order to reach a high specific moisture extraction rate (SMER) and a low leakage ratio. A low external airflow and high power supply to the heater gives the highest SMER. To reach the lowest values for the leakage ratio, a low internal airflow should be applied together with a high external airflow. The use of a statistical model gave valuable information of the performance of the existing tumble dryer. For further improving the energy efficiency of the dryer, the amount of leakage and its location was investigated in Paper IV. By studying energy and mass balances from experiments, pressure measurements and modelling, the effects of leakage on the process were evaluated. As the location of the leakage is so important for the energy efficiency, the worst-case scenario where leakage is located between the heater and the drum is used as a start point in the study. It was determined that there is a large leakage of air between the heater and the drum leading to a significant loss in energy recovery.

The drying loads used by consumers are getting smaller, often less than 3 kg dry load, while the maximum capacity of the dryers are increasing, up to 7 or 8 kg. In Paper II, tests were made with different loads in order to investigate if the energy label serves its purpose as today’s standard is set at the dryers’ maximum capacity. The results from this study show that the energy efficiency when drying a small load is significantly lower than for a large load. In order to encourage a production of tumble dryers with higher energy efficiency for small loads, where the dryer is most frequently used, the standards for the energy label should be revised. Today, manufacturers do not gain any benefits by improving the performance for partial loads.

A mathematical model over a venting tumble dryer was established in Paper III with the aim of testing different control strategies in order to improve the energy efficiency of the tumble dryer for partial loads. The ideas behind the different strategies were to minimize the heat losses during the drying process and to increase the residence time for the air in the drum and thereby increase the moisture content of the air leaving the drum. Using such a control strategy it is possible to reach an improvement of SMER by approximately 4% when drying small loads. In order to reach larger improvements, however, a more extensive product development will be necessary.

Finally, the results in this thesis points at the necessity of including not only the technical development of the tumble dryer, but also the policy tools involved and the consumers’ habits in order to reach a reduced electricity use for drying clothes in households. 

Place, publisher, year, edition, pages
Karlstad: Karlstad University, 2011. p. 56
Series
Karlstad University Studies, ISSN 1403-8099 ; 2011:43
Keywords
drying, domestic, energy efficiency, textile, energy labelling standard
National Category
Energy Systems
Research subject
Environmental and Energy Systems
Identifiers
urn:nbn:se:kau:diva-8109 (URN)978-91-7063-378-2 (ISBN)
Public defence
2011-10-04, 11D 257 (Agardhsalen), Universitetsgatan 1, Karlstad, 13:00 (Swedish)
Opponent
Supervisors
Available from: 2011-09-14 Created: 2011-08-23 Last updated: 2017-12-07Bibliographically approved
Stawreberg, L. & Nilsson, L. (2010). Modelling of Specific Moisture Extraction Rate and Leakage Ratio in a Condensing Tumble Dryer. Applied Thermal Engineering, 30, 2173-2179
Open this publication in new window or tab >>Modelling of Specific Moisture Extraction Rate and Leakage Ratio in a Condensing Tumble Dryer
2010 (English)In: Applied Thermal Engineering, ISSN 1359-4311, E-ISSN 1873-5606, Vol. 30, p. 2173-2179Article in journal (Refereed) Published
National Category
Energy Systems
Research subject
Environmental and Energy Systems
Identifiers
urn:nbn:se:kau:diva-8242 (URN)10.1016/j.applthermaleng.2010.05.030 (DOI)000280892400035 ()
Available from: 2011-09-14 Created: 2011-09-14 Last updated: 2017-12-08Bibliographically approved
Berghel, J., Renström, R. & Stawreberg, L. (2009). Integrating tumble dryer in the heating systems in block of flats. Paper presented at 4th Nordic Drying Conference. Paper presented at 4th Nordic Drying Conference.
Open this publication in new window or tab >>Integrating tumble dryer in the heating systems in block of flats
2009 (English)Conference paper, Published paper (Other (popular science, discussion, etc.))
National Category
Energy Systems
Research subject
Environmental and Energy Systems
Identifiers
urn:nbn:se:kau:diva-9852 (URN)
Conference
4th Nordic Drying Conference
Available from: 2012-02-08 Created: 2012-02-08 Last updated: 2017-12-06Bibliographically approved
Organisations

Search in DiVA

Show all publications