FORCE-VELOCITY RELATIONSHIP OF LEG MUSCLES ASSESSED BY MOTORIZED TREADMILL TESTS

We aimed to explore the properties of the F-V relationship of leg muscles exerting the maximum pulling F within a wide range of V set on a standard motorized treadmill. Subjects exerted maximum horizontally pulling F while walking on a treadmill set to 8 different V (1.4 - 3.3 m/s). The obtained F-V relationships proved to be linear and strong (all R \u3e 0.84), while their parameters depicting the leg muscle capacities for producing maximum F, V, and power (i.e., the maximum product of F and V) were highly reliable (0.84 \u3c ICC \u3c 0.97; 6.4 \u3c CV% \u3c 19.3). Moreover, when obtained from only the lowest and highest V the F-V relationships revealed virtually identical outcomes. We conclude that the evaluated procedure could be developed into an ecologically valid and reliable protocol for routine testing of the F, V, and P-producing capacities of leg muscles

Integration of the environmental management aspect in the optimization of the design and planning of energy systems

The increasing concerns regarding the environmental pollution derived from anthropogenic activities, such as the use of fossil fuels for power generation, has driven many interested parties to seek different alternatives, e.g. use of renewable energy sources, use of “cleaner” fuels and use of more effective technologies, in order to minimize and control the quantity of emissions that are produced during the life cycle of conventional energy sources. In addition to these alternatives, the use of an integrated procedure in which the environmental aspect will be taken into account during the design and planning of energy systems could provide a basis on which emissions reduction will be dealt with a life cycle approach. The work presented in this paper focuses on the examination of the possibilities of integrating the environmental aspects in the preliminary phase of the conventional design and planning of energy systems in conjunction with other parameters, such as financial cost, availability, capacity, location, etc. The integration of the environmental parameter to the design is carried out within a context where Eco-design concepts are applied. Due to the multi-parameter nature of the design procedure, the tools that are used are Life Cycle Analysis and Multi-criteria Analysis. The proposed optimization model examines and identifies optimum available options of the use of different energy sources and technologies for the production of electricity and/or heat by minimizing both the financial cost and the environmental impacts, with regard to a multiple objective optimization subject to a set of specific constraints. Implementation of the proposed model in the form of a case study for the island of Rhodes in Greece revealed that an optimized solution both cost and environmental-wise, would be an almost balanced participation of renewables and non-renewable energy sources in the energy mix

With district heating toward a sustainable future : System studies of district heating and cooling that interact with power, transport and industrial sectors

The aim of this thesis is to identify measures which should be taken in DH systems (DHSs) in order to contribute to the development of the DHSs and other energy systems (especially transport, industrial and power sectors) toward sustainability. Four business strategies were analysed: delivering excess heat from biofuel production industry to DHSs, conversion of industrial processes to DH, integration of biofuel production in DHSs and integration of DHdriven absorption cooling technology in DHSs. Delivering excess heat from biofuel production industry to DHSs was analysed with a focus on the biofuel production costs for four biofuel production technologies. Integration of biofuel production and integration of DH-driven absorption cooling technology in DHSs were analysed with a focus on Stockholm’s DHS, using an optimisation model framework called MODEST. When the conversion of industrial processes to DH was analysed, DHSs and industrial companies in Västra Götaland, Östergötland and Jönköping counties were used as case studies; a method for heat load analysis called MeHLA was used to analyse the effects on the local DHSs. The results showed that when considering biomass an unlimited resource, by applying the abovementioned business strategies DH has a potential to reduce global fossil fuel consumption and global GHG emissions associated with power, industrial and transport sectors. DH producers may contribute to the sustainable development of the  transport sector by buying excess heat from the biofuel production industry. This business strategy results in lower biofuel production costs, which promotes development of biofuel production technologies that are not yet commercial. Moreover, introduction of large-scale biofuel production into local DHSs enables development of local biofuel supply chains; this may facilitate the introduction of biofuel in the local transport sectors and subsequently decrease gasoline and fossil diesel use. Conversion of industrial processes from fossil fuels and electricity to DH is a business strategy which would make the industry less dependent on fossil fuels and fossil fuelbased electricity. DH may also contribute to the sustainable development of the industry by buying waste heat from industrial processes, since this strategy increases the total energy efficiency of the industrial processes and reduces production costs. Furthermore, DH has a possibility to reduce fossil fuel consumption and subsequently GHG emissions in the power sector by producing electricity in biomass- or waste-fuelled CHP plants. When the marginal electricity is associated with high GHG emissions (e.g. when it is produced in coal-fired condensing power (CCP)) plants, the reduction of the marginal electricity production (due to the conversion of industrial processes from electricity to DH and due to the conversion of compression cooling to DHdriven absorption cooling) results in higher environmental benefits. On the other hand, the introduction of biofuel production into DHSs becomes less attractive from an environmental viewpoint, because the investments in biofuel production instead of in CHP production lead to lower electricity production in the DHSs. The increased DH use in industry and introduction of the biofuel production and DH-driven absorption cooling production into the DHSs lead to increased biomass use in the DHSs. Because of this, if biomass is considered a limited resource, the environmental benefits of applying these business strategies are lower or non-existent.Syftet med denna avhandling är att identifiera åtgärder som bör vidtas i FJV-system (FJVS) för att bidra till en hållbar utveckling av FJV och andra relaterade energisystem som transport, industri- och energisektorn. Fyra affärsstrategier är analyserade: att leverera överskottsvärme från produktion av biobränsle för transportsektorn, konvertering av industriella processer till FJV, integration av biobränsleproduktion för transportsektorn i FJVS och integration av FJV-driven absorptionskylteknik i FJVS. Att leverera överskottsvärme från produktion av biobränsle till transportsektorn analyserades med fokus på kostnader för fyra olika produktionstekniker. Integration av biobränsleproduktion till transportsektorn och integration av FJV-driven absorptionskylteknik i FJVS analyserades på Stockholms FJVS med optimeringsmodellen MODEST. När konvertering av industriella processer till FJV analyserades, användes FJVS och industriföretag i Västra Götaland, Östergötlands och Jönköpings län som fallstudier. Metoden MeHLA som används för analys av värmebelastning tillämpades för att analysera effekterna på de lokala FJVS. Resultaten från studierna visar att när biomassa anses vara en obegränsad resurs har FJV en potential att minska den globala konsumtionen av fossila bränslen och de globala utsläppen av växthusgaser som förknippas med transport-, industri- och energisektorn, for samtliga analyserade affärsstrategierna. FJV producenter kan bidra till en hållbar utveckling av transportsektorn genom användningen av överskottsvärme från produktion av transportbiobränsle. Den analyserade affärsstrategin ger lägre produktionskostnader för transportbiobränsle vilket främjar utvecklingen av produktionsteknik som ännu inte är kommersiell. Dessutom möjliggörs utveckling av lokala försörjningskedjor av transportbiobränsle på grund av den storskaliga produktionen av transportbiobränsle i lokala FJVS. Detta kan sedan underlätta införandet av transportbiobränsle i lokala transporter och även minska användningen av bensin och fossil diesel. Konvertering av industriella processer från fossila bränslen och el till FJV är en affärsstrategi som skulle göra FJV-branschen mindre beroende av fossila bränslen. Att använda spillvärme från industriprocesser ökar den totala energieffektiviteten i de industriella processerna och minskar produktionskostnaderna. Genom att dessutom öka FJV-användningen inom industriella produktionsprocesser och genom att konvertera eldriven kompressionskyla till FJV driven komfortabsorptionskyla, minskar säsongsvariationerna av FJV lasten, vilket leder till ett bättre utnyttjande av produktionsanläggningar för FJV. Om produktionsanläggningarna för baslast i FJVS är kraftvärmeverk, leder dessa två affärsstrategier till en ökad elproduktion i FJVS. När marginalproducerad el förknippas med höga utsläpp av växthusgaser (t.ex. när det produceras i koleldade kondenskraftverk), resulterar en minskning av den marginella elproduktionen (på grund av konvertering av industriella processer från el till FJV och på grund av konvertering eldriven kompressionskyla till FJV-driven absorptionkyla) i minskade globala emissioner av växthusgas. Om man däremot tittar på införandet av produktion av transportbiobränsle i FJVS är denna affärsstrategi mindre attraktiv ur ett miljöperspektiv. Orsaken till detta är att investering i produktion av transportbiobränsle istället för i kraftvärmeproduktion, leder till minskad elproduktion i FJVS. Den ökade FJV-användningen inom industrin och införandet av produktion av biobränsle för transportsektorn och FJV driven absorptionskylproduktion i FJVS leder till en ökad användning av biomassa i FJVS. När biomassa anses vara en begränsad resurs, är de miljömässiga fördelarna med att tillämpa dessa affärsstrategier relativt låga eller till och med obefintliga

Classification of Measures for Dealing with District Heating Load Variations-A Systematic Review

The highly varying character of district heating (DH) demand results in low capacity utilization of the DH plants, as well as increased use of fossil fuels during peak demand. The aim of this study is to present an overview and a comprehensive classification of measures intended to manage these load variations. A systematic literature review was conducted based on previously defined search strings as well as inclusion and exclusion criteria. Two scientific databases were used as data sources. Based on 96 detected publications, the measures were categorized as (1) complementing DH production in heat-only boilers (HOBs), or geothermal or booster heat pumps (HPs) (usually controlled by the DH company), (2) thermal energy (TE) storage in storage units or in the network (controlled by the company), and (3) demand side measures, which can be strategic demand increase, direct demand response (DR), or indirect DR. While the company has control over direct DR (e.g., thermal storage in the thermal mass of the buildings), indirect DR is based on communication between the customer and the company, where the customer has complete control. The multi-disciplinary nature of this topic requires an interdisciplinary approach

Economic and environmental benefits of converting industrial processes to district heating

The aim of this study is to analyse the possibilities of converting production and support processes from electricity and fossil fuels to district heating in 83 manufacturing companies in three different Swedish counties. A tool for heat load analysis called Method for Heat Load Analysis (MeHLA) is used to explore how the conversions would affect the heat load duration curves in local district heating systems. Economic effects and impacts on global emissions of greenhouse gases are studied from a system perspective. The study has been conducted considering two different energy market conditions for the year 2030. The results show that there is a potential for increasing industrial district heating use in all analysed counties. When comparing all three counties, the greatest potential regarding percentage is found in Jönköping, where the district heating use in the manufacturing companies could increase by nine times (from 5 GWh to 45 GWh annually). The industrial district heating use could increase by two times (from 84 GWh to 168 GWh annually) in Östergötland and by four times (from 14 GWh to 58 GWh annually) in Västra Götaland. The conversion of the industrial production processes to district heating would lead to a district heating demand curve which is less dependent on outdoor temperature. As a result, the utilization period of the combined heat and power plants would be prolonged, which would decrease district heating production costs due to the increased income from the electricity production. In all analysed counties, the energy costs for the companies decrease after the conversions. Furthermore, the increased electricity production in the combined heat and power plants, and the decreased electricity and fossil fuel use in the industrial sector opens up a possibility for a reduction of global greenhouse gas emissions. The potential for the reduction of global greenhouse gas emissions is highly dependent on the alternative use of biomass and on the type of the marginal electricity producers. When the marginal effects from biomass use are not considered, the greenhouse gas emissions reduction is between 10 thousand tonnes of CO2eq and 58 thousand tonnes of CO2eq per year, depending on the county and the type of marginal electricity production plants. The highest reduction is achieved in Östergötland. However, considering that biomass is a limited resource, the increase of biomass use in the district heating systems may lead to a decrease of biomass use in other energy systems. If this assumption is included in the calculations, the conversion of the industrial processes to district heating still signify a  potential for reduction of greenhouse gas emissions, but this potential is considerable lower

Economic and environmental benefits of converting industrial processes to district heating

The aim of this study is to analyse the possibilities of converting production and support processes from electricity and fossil fuels to district heating in 83 manufacturing companies in three different Swedish counties. A tool for heat load analysis called Method for Heat Load Analysis (MeHLA) is used to explore how the conversions would affect the heat load duration curves in local district heating systems. Economic effects and impacts on global emissions of greenhouse gases are studied from a system perspective. The study has been conducted considering two different energy market conditions for the year 2030. The results show that there is a potential for increasing industrial district heating use in all analysed counties. When comparing all three counties, the greatest potential regarding percentage is found in Jönköping, where the district heating use in the manufacturing companies could increase by nine times (from 5 GWh to 45 GWh annually). The industrial district heating use could increase by two times (from 84 GWh to 168 GWh annually) in Östergötland and by four times (from 14 GWh to 58 GWh annually) in Västra Götaland. The conversion of the industrial production processes to district heating would lead to a district heating demand curve which is less dependent on outdoor temperature. As a result, the utilization period of the combined heat and power plants would be prolonged, which would decrease district heating production costs due to the increased income from the electricity production. In all analysed counties, the energy costs for the companies decrease after the conversions. Furthermore, the increased electricity production in the combined heat and power plants, and the decreased electricity and fossil fuel use in the industrial sector opens up a possibility for a reduction of global greenhouse gas emissions. The potential for the reduction of global greenhouse gas emissions is highly dependent on the alternative use of biomass and on the type of the marginal electricity producers. When the marginal effects from biomass use are not considered, the greenhouse gas emissions reduction is between 10 thousand tonnes of CO2eq and 58 thousand tonnes of CO2eq per year, depending on the county and the type of marginal electricity production plants. The highest reduction is achieved in Östergötland. However, considering that biomass is a limited resource, the increase of biomass use in the district heating systems may lead to a decrease of biomass use in other energy systems. If this assumption is included in the calculations, the conversion of the industrial processes to district heating still signify a  potential for reduction of greenhouse gas emissions, but this potential is considerable lower

Integration of biofuel and DH production - Possibilities, potential and trade-off situations : A review

There are several barriers to increased use of biofuel in the transport sector (e.g., shortage of feedstocks, high production costs, and relatively low energy yields from standalone biofuel plants). One possible solution is integration of biofuel and district heating (DH) production. This study aims (1) to identify challenges (e.g. tradeoffs) related to integration and to suggests possible ways of dealing with these challenges, (2) to highlight factors that may influence effects on global GHG emissions from integration, (3) to highlight factors which should be considered when evaluating economic aspects related to integration. After conducting a systematic review using a prescribed and structured protocol, 38 articles were identified as relevant for this study. These articles present four different approaches for integration: delivering the excess heat from biorefineries to DH networks, utilising DH in biofuel production processes, integrating biofuel production with existing DH facilities, and building new polygeneration biofuel production facilities in DH systems (DHS).If investments in biofuel compete with combined heat and power (CHP) production, the electricity price and the premium paid for renewable electricity influence profitability in CHP plants investments and therefore even profitability in investments in biofuel production. Competition should also be considered when weighing environmental benefits (the influence on global GHG emissions). Competition can create trade-offs related to DHSs operating conditions, limited local and global biomass availability, and limited available heat sinks. To deal with these trade-offs and to avoid suboptimization, stakeholders in regional planning, investors and policymakers should cooperate.All identified studies noted that a comprehensive approach is needed to evaluate profitability aspects and effects on global GHG emissions.For instance, utilising excess heat or residues from a biofuel production process in a DHS requires consideration of alternative DH production and alternative fuels. If electricity is one of the by-products from the biofuel production, alternative electricity production should also be considered. The majority of the studies dealt with economic performance of integration. Some of the factors found to influence profitability include available heat sink, alternative DH and electricity production, expected operation patterns, energy policy and energy market conditions. The potential for reducing global greenhouse gases (GHG) emissions depends on alternative DH and electricity production but also on biomass availability and alternative biomass users