Denna rapport baseras på experimentella försök där det undersökts hur pelletdensiteten påverkar utsläpp av kolmonoxid (CO) och stoft vid småskalig förbränning. I en testpanna med ansluten pelletsbrännare testades tre densiteter: låg, mellan och hög. Testerna uppdelades i tre faser i form av uppstart, kontinuerlig drift och släckning. Tre repetitioner gjordes på varje fas och för varje bränsle med undantag av släckning där endast en mätning per bränsle gjordes. Resultatet visade generellt en tydlig skillnad i CO-emission. Oberoende av densitet var CO-emissionerna mycket större vid uppstart och släckning än vid kontinuerlig drift. Avseende densitet gavs ett entydigt resultat där den lägsta pelletdensiteten gav högre stoftemissioner under alla driftsförhållanden. Skillnaden mellan de två pelletssorterna av högre densitet är däremot inte signifikant. För CO-emissioner sågs vid uppstartsfasen en tydlig trend mellan minskad pelletdensitet och ökade CO-emissioner. Vid kontinuerlig drift sågs emellertid det omvända: hög densitet gav högre CO-emissioner, varvid mellandensiteten gav något lägre CO-emissioner och låg densitet gav lägst CO-emissioner. Om skillnaden är uteslutande beroende på pelletdensiteten är svårt att säga. Ytterligare försök rekommenderas för att avgöra den exakta inverkan av pelletarnas densitet.

Emissions from residential combustion appliances vary significantly depending on the firing behaviours and combustion conditions, in addition to combustion technologies and fuel quality. Although wood pellet combustion in residential heating boilers is efficient, the combustion conditions during start-up and stop phases are not optimal and produce significantly high emissions such as carbon monoxide and hydrocarbon from incomplete combustion. The emissions from the start-up and stop phases of the pellet boilers are not fully taken into account in test methods for ecolabels which primarily focus on emissions during operation on full load and part load. The objective of the thesis is to investigate the emission characteristics during realistic operation of residential wood pellet boilers in order to identify when the major part of the annual emissions occur. Emissions from four residential wood pellet boilers were measured and characterized for three operating phases (start-up, steady and stop). Emissions from realistic operation of combined solar and wood pellet heating systems was continuously measured to investigate the influence of start-up and stop phases on total annual emissions. Measured emission data from the pellet devices were used to build an emission model to predict the annual emission factors from the dynamic operation of the heating system using the simulation software TRNSYS. Start-up emissions are found to vary with ignition type, supply of air and fuel, and time to complete the phase. Stop emissions are influenced by fan operation characteristics and the cleaning routine. Start-up and stop phases under realistic operation conditions contribute 80 – 95% of annual carbon monoxide (CO) emission, 60 – 90% total hydrocarbon (TOC), 10 – 20% of nitrogen oxides (NO), and 30 – 40% particles emissions. Annual emission factors from realistic operation of tested residential heating system with a top fed wood pelt boiler can be between 190 and 400 mg/MJ for the CO emissions, between 60 and 95 mg/MJ for the NO, between 6 and 25 mg/MJ for the TOC, between 30 and 116 mg/MJ for the particulate matter and between 2x10-13 /MJ and 4x10-13 /MJ for the number of particles. If the boiler has the cleaning sequence with compressed air such as in boiler B2, annual CO emission factor can be up to 550 mg/MJ. Average CO, TOC and particles emissions under realistic annual condition were greater than the limits values of two eco labels. These results highlight the importance of start-up and stop phases in annual emission factors (especially CO and TOC). Since a large or dominating part of the annual emissions in real operation arise from the start-up and stop sequences, test methods required by the ecolabels should take these emissions into account. In this way it will encourage the boiler manufacturers to minimize annual emissions. The annual emissions of residential pellet heating system can be reduced by optimizing the number of start-ups of the pellet boiler. It is possible to reduce up to 85% of the number of start-ups by optimizing the system design and its controller such as switching of the boiler pump after it stops, using two temperature sensors for boiler ON/OFF control, optimizing of the positions of the connections to the storage tank, increasing the mixing valve temperature in the boiler circuit and decreasing the pump flow rate. For 85 % reduction of start-ups, 75 % of CO and TOC emission factors were reduced while 13% increase in NO and 15 % increase in particle emissions was observed.

Emissions from residential combustion appliances vary significantly depending on the firing behaviours and combustion conditions, in addition to combustion technologies and fuel quality. Although wood pellet combustion in residential heating boilers is efficient, the combustion conditions during start-up and stop phases are not optimal and produce significantly high emissions such as carbon monoxide and hydrocarbon from incomplete combustion. The emissions from the start-up and stop phases of the pellet boilers are not fully taken into account in test methods for ecolabels which primarily focus on emissions during operation on full load and part load.  The objective of the thesis is to investigate the emission characteristics during realistic operation of residential wood pellet boilers in order to identify when the major part of the annual emissions occur. Emissions from four residential wood pellet boilers were measured and characterized for three operating phases (start-up, steady and stop). Emissions from realistic operation of combined solar and wood pellet heating systems was continuously measured to investigate the influence of start-up and stop phases on total annual emissions. Measured emission data from the pellet devices were used to build an emission model to predict the annual emission factors from the dynamic operation of the heating system using the simulation software TRNSYS.  Start-up emissions are found to vary with ignition type, supply of air and fuel, and time to complete the phase. Stop emissions are influenced by fan operation characteristics and the cleaning routine. Start-up and stop phases under realistic operation conditions contribute 80 – 95% of annual carbon monoxide (CO) emission, 60 – 90% total hydrocarbon (TOC), 10 – 20% of nitrogen oxides (NO), and 30 – 40% particles emissions. Annual emission factors from realistic operation of tested residential heating system with a top fed wood pelt boiler can be between 190 and 400 mg/MJ for the CO emissions, between 60 and 95 mg/MJ for the NO, between 6 and 25 mg/MJ for the TOC, between 30 and 116 mg/MJ for the particulate matter and between 2x1013 and 4x1013 /MJ for the number of particles. If the boiler has the cleaning sequence with compressed air such as in boiler B2, annual CO emission factor can be up to 550 mg/MJ. Average CO, TOC and particles emissions under realistic annual condition were greater than the limits values of two eco labels. These results highlight the importance of start-up and stop phases in annual emission factors (especially CO and TOC). Since a large or dominating part of the annual emissions in real operation arise from the start-up and stop sequences, test methods required by the ecolabels should take these emissions into account. In this way it will encourage the boiler manufacturers to minimize annual emissions.  The annual emissions of residential pellet heating system can be reduced by optimizing the number of start-ups of the pellet boiler. It is possible to reduce up to 85% of the number of start-ups by optimizing the system design and its controller such as switching of the boiler pump after it stops, using two temperature sensors for boiler ON/OFF control, optimizing of the positions of the connections to the storage tank, increasing the mixing valve temperature in the boiler circuit and decreasing the pump flow rate. For 85 % reduction of start-ups, 75 % of CO and TOC emission factors were reduced while 13% increase in NO and 15 % increase in particle emissions was observed.

The curing of flue-cured tobacco (Nicotiana tabacum L.) is an energy intensive process and represents a significant portion of the overall cost of production. Given the goal of the industry to reduce the environmental footprint of tobacco production and the energy demand of curing, attention has been directed to explore options for the use of renewable fuels for heating tobacco barns. A two-year study conducted at the Virginia Tech Southern Piedmont Center evaluated the effectiveness and cost of curing flue-cured tobacco with a wood pellet burner. Additionally, field studies were conducted to evaluate the feasibility of on-farm production of biomass fuel crops as well as on-farm manufacture of biomass fuel pellets. The first time use of a wood pellet burner with an air-to-air heat exchanger in a bulk curing barn proved to be a viable alternative to a conventional propane fueled burner. Curing cost averaged $0.05 with the pellet burner compared to $0.04 per kilogram of tobacco with the propane burner. The increase in cost was offset by a 90 percent reduction of CO2 emissions with the use of wood pellets. The use of low lignin grass varieties did have an impact on biomass pellet properties. Pellet testing revealed high ash and chloride levels which could be problematic using a high efficiency wood pellet burner. Full maturity harvest of annual grasses fertilized with 112 kg per ha N resulted in higher yields. However, fertilizing for maximum yield would increase the CO2 footprint for biomass fuel pellet production. / Master of Science / Curing flue-cured tobacco (Nicotiana tabacum L.) is an energy intensive process consuming large quantities of both propane and electricity and represents the second highest overall production cost. The tobacco as a whole has a goal to reduce the environmental footprint of tobacco production and the energy demand of curing. In order to produce the crop more sustainably, attention has been directed to explore options for the use of renewable fuels for heating tobacco barns. Currently utilizing renewable fuels is limited to a small number of wood-fired hot water boiler systems. A two-year study conducted at the Virginia Tech Southern Piedmont Center evaluated the effectiveness and cost of curing flue-cured tobacco with a wood pellet burner. Additionally, field studies were conducted to evaluate the feasibility of on-farm production of biomass fuel crops as well as on-farm manufacture of biomass fuel pellets. The first time use of a wood pellet burner with an air-to-air heat exchanger in a bulk curing barn proved to be a viable alternative to a conventional propane fueled burner. The wood pellet burner with air-to-air heat exchanger was compared to a high efficiency prototype propane burner. Curing cost averaged $0.05 with the pellet burner compared to $0.04 per kilogram of tobacco with the propane burner. The increase in cost was offset by a 90 percent reduction of CO₂ emissions with the use of wood pellets. Curing cost with the wood pellet burner is expected to be lower than that of a more traditional propane burner and curing barn. The use of low lignin grass varieties did have an impact on biomass pellet properties, however more replications testing on-farm produced pellets is necessary in order strengthen the validity of these results. Pellet testing revealed high ash and chloride levels in on-farm produced biomass pellets which could be problematic using a high efficiency wood pellet burner, but may be less precarious if paired with a more rudimentary burner. Full maturity harvest of summer annual grasses fertilized with 112 kg per ha N resulted in higher yields. However, fertilizing for maximum yield would increase the CO₂ footprint for biomass fuel pellet production. Based on these results, purchasing commercially made, readily available wood pellets is the best alternative to using a renewable fuel to cure flue-cured tobacco. This practice would allow growers to incrementally adopt the use of a renewable fuel while providing comparable operation ease as traditional propane burners.

Företaget TräEnergi Teknik AB säljer pelletskaminer. Försäljningen av produkten går inte så bra, men ägaren Carl-Axel Fagerström tycker att produkten borde vara efterfrågad av kunderna eftersom den är både miljövänlig och prisvärd. I denna rapport undersöks hur företaget kan ändra sina marknadsföringsstrategier för att nå ut till potentiella köpare. En enkätundersökning har gjorts hos återförsäljare för att ta reda på slutkundernas behov och önskemål. Ur undersökningen framgick att även om kunden är miljömedveten går priset alltid före. Det visade sig dessutom att kunderna de senaste åren börjat leta efter nya alternativ på grund av de kalla vintrarna och högre elpriserna. Vad gäller marknadsföring tyckte återförsäljarna att mässor, webbsidor, TV-reklam och annons i facktidningar är de bästa kanalerna. Kundernas kännedom om pelletskaminer varierar, att de väljs bort till fördel för värmepumpar handlar ofta om okunskap om produkten. Samtliga av respondenterna anser att det finns en potential i framtiden inom marknaden. För att Träenergi Teknik ska lyckas nå ut till den tilltänkta målgruppen krävs utvecklad marknadsföringsstrategi, detta kan göras genom att mer ingående arbeta mer med kanalstrategi. / The company TräEnergi Teknik AB sells wood/pellet stoves. Sales is not to good however, the owner Carl-Axel Fagerström thinks that the product ought to be more in demand since it is both environmental friendly and worth its price. This study will show how the company can change its market strategies to better reach the market and the potential customers. A survey was conducted among retailers to find out about the customers’ demands and requirements. The results of the survey showed that even though the customer is environmentally conscious, the price is always the decisive factor. The survey also showed that customers in recent years have started to look for new heating solutions due to the hard winters and higher electricity prices. Regarding how to market the product the retailers suggested fairs, web pages, TV commercials and advertizing as the best channels to do so. The customers’ knowledge of pellet stoves varies and the fact that heat pumps are chosen over pellet stoves most likely has to do with the lack of knowledge regarding pellet stoves. All the respondents think there is potential for a future market and to be able to reach their target group, TräEnergi Teknik needs a defined market strategy. This thesis will show that the best strategy is channel differentiation through retailers.

Abstract According to the EU’s strategy and the corresponding Finnish national strategy on waste materials, all kinds of waste must be utilised primarily as material (reuse, recycling) and secondarily as energy, and at the lowest level of waste hierarchy is their disposal using environmentally friendly methods. Today material efficiency is an essential topic in promoting sustainable use of natural resources, industrial by-products and waste material. The present goal proposed by the EU sets the target for the total proportion of renewable energy as high as 38% by 2020 in Finland. Up to 20 million tonnes of waste wood biomass per year are left unused in Finland, mainly in the forests during forestry operations, because supply and demand do not meet. As a consequence of high heat energy prices, the looming threat of climate change, the greenhouse effect and global as well as national demands to considerably increase the proportion of renewable energy, Finland currently has a tremendous interest in increasing decentralised pellet production alongside of large-scale factories. The aim of this thesis is to promote the development of eco-, material- and cost-efficient Nordic wood-based pellet production and utilisation of pellet bio-ash by means of chemical research. Using Finnish wood (sawdust and shavings) as a model raw material, the total functionality of a pilot-scale pellet facility combined with an extensive chemical toolbox was tested in this study to promote development of an eco-, material- and cost-efficient wood-based pellet production chain. The chemical toolbox includes measurements of moisture content, density, heat value, mechanical durability and particle size distribution, TG analysis and elementary analysis, as well as new applications for pellet biodegradation using BOD OxiTop equipment and optical microscopic staining methods. To improve the quality of pellets, considering the profitability of production and occupational safety factors (wood dust exposure, fire and explosion risk), it is profitable to use different binding agents, especially industrial by-products and locally utilisable residuals. Thus, lignosulphonate, residual potato flour and potato peel residue were used and tested as model adhesive binding agents. The results showed that binding agents increased the quality of pellets and changed their inorganic characteristics, but did not have a significant effect on their calorimetric heat values. Lignosulphonate even increased the rate of production. To characterise different starch-containing binding agents, a new specific optical microscopic staining method was developed and tested, and the initial results are presented in this thesis. Wood pellet ash has potential as a liming agent, in soil remediation, as a soil fertilizer, and in granulated form, in new applications such as road construction and waste water purification. Valuable information about raw materials, binding agents and the pelletizing process is necessary when developing good-quality pellets—a prime biofuel—from non-utilised low-value and/or moist biomass that has undergone a cost-efficient drying process. This way pellet production will have more essential importance in energy policy, especially in the European forest belt. / Tiivistelmä Vallitsevan EU:n sekä Suomen kansallisen lainsäädännön mukaan kaikenlainen jäte täytyy hyödyntää ensisijaisesti materiaalina (uudelleenkäyttö, kierrätys), toissijaisesti energiana ja jätehierarkiassa alimpana tasona on sen hävittäminen ympäristöystävällisin keinoin. Materiaalitehokkuus on nykyään välttämätön aihe edistettäessä luonnonvarojen, teollisuuden sivutuotteiden ja jätemateriaalien kestävää käyttöä. EU-strategian mukainen tavoite uusiutuvan energian osuudelle kaikesta energiantuotannosta Suomessa on 38 % vuoteen 2020 mennessä. Jopa 20 miljoonaa tonnia jätepuubiomassaa vuodessa jää käyttämättä Suomessa lähinnä metsänharvennustöiden yhteydessä, koska kysyntä ja tarjonta eivät kohtaa. Seurauksena korkeista lämpöenergiahinnoista, uhkaavasta ilmastonmuutoksesta, kasvihuoneilmiöstä sekä globaalisista ja kansallisista vaatimuksista lisätä uusiutuvan energian osuutta, Suomessa on viime aikoina noussut voimakas kiinnostus lisätä hajautettua pellettituotantoa suurten pellettilaitosten rinnalle. Väitöskirjan tarkoituksena on edistää ja kehittää pohjoismaista eko- ja kustannustehokasta puupellettituotantoa ja pellettibiotuhkan hyötykäyttöä kemiallisen tutkimuksen avulla. Käyttäen suomalaista puuta (sahanpurua ja kutterinlastua) malliraaka-aineina, tässä tutkimuksessa testattiin pilot-mittakaavan pellettilaitoksen toimivuutta yhdistettynä laajaan kemialliseen ”työpakettiin”, edistämään tulevaisuuden eko-, materiaali- ja kustannustehokkaan pellettituotantoketjun kehittämistä. Kemiallinen työpaketti sisältää kosteuden, tiheyden, lämpöarvon, mekaanisen kestävyyden ja partikkelikokojakauman määritykset, TG- ja alkuaineanalyysin, kuten myös uudet sovellukset pellettien ja niiden sideaineiden biohajoavuuden määrittämiseksi BOD OxiTop -laitteistoilla sekä optisen mikroskooppivärjäysmenetelmän. Pellettien laadun kohottamiseksi, ottaen huomioon myös tuotannon kannattavuuden ja työterveydelliset ongelmat (puupölylle altistuminen, tulipalo- ja räjähdysvaara), on perusteltua käyttää sideaineita, erityisesti teollisuuden sivutuotteita ja paikallisesti hyödynnettävissä olevia jätemateriaaleja. Täten lignosulfonaattia, jäteperunajauhoa ja perunankuorijätettä käytettiin ja testattiin liimaavina mallisideaineina. Tulokset osoittivat, että sideaineet nostivat pellettien laatua ja muuttivat niiden epäorgaanisia ominaisuuksia, mutta niillä ei ollut merkittävää vaikutusta määritettyihin lämpöarvoihin. Lignosulfonaatti lisäsi selvästi pelletoinnin tuotantonopeutta. Työssä kehitettiin pelleteille uusi spesifinen optinen mikroskooppivärjäysmenetelmä erilaisten tärkkelystä sisältävien sideaineiden karakterisointiin ja ensimmäiset tulokset on esitetty tässä väitöskirjassa. Puupellettituhka on potentiaalinen kalkitus- ja maanparannusaineena, lannoitteena sekä rakeistettuna uusissa sovelluksissa, kuten tierakentamisessa ja jäteveden puhdistuksessa. Arvokas informaatio raaka-aineista, sideaineista sekä pelletöintiprosessista on välttämätöntä kehitettäessä tulevaisuudessa hyvälaatuisia pellettejä, ”priimaa” biopolttoainetta, hyödyntämättömästä huonolaatuisesta ja/tai kosteasta biomassasta, joka on ennen pelletointia käynyt läpi kustannustehokkaan kuivausprosessin. Täten voidaan olennaisesti lisätä pellettituotannon merkitystä energiapolitiikassa, erityisesti Euroopan metsävyöhykkeellä.

Ce travail porte sur l’étude et le développement d’un système innovant de ventilation et de chauffage au bois dans les habitations à basse consommation d’énergie, qui sont appelées à devenir la référence constructive en France dès 2015. Dans ces habitations fortement isolées et particulièrement étanches à l’air, les besoins de chauffage sont très faibles et peuvent être couverts par une source de chaleur d’origine renouvelable, telle que le bois énergie. En outre, l’utilisation d’une ventilation performante s’impose comme étant un critère essentiel pour assurer la bonne qualité de l’air intérieur et peut même devenir l’unique vecteur de chauffage en apportant l’appoint de chaleur sur l’air insufflé dans les différentes pièces de l’habitation. Le système présenté dans cette étude propose ainsi de combiner les avantages d’un appareil de chauffage au bois de petite puissance, ici un poêle à granulés de bois, et ceux d’une ventilation à récupération de chaleur sur l’air extrait, grâce à un conduit échangeur intégré à la cheminée du poêle et relié au réseau de soufflage de la ventilation. Développé en partenariat avec l’industriel POUJOULAT, spécialisé dans la fabrication de conduits de cheminée métalliques, ce conduit échangeur permet de récupérer sur l’air neuf une partie de la chaleur initialement perdue par les fumées et de la distribuer dans toutes des zones de vie de l’habitation, même les plus éloignées de l’appareil au bois. Après avoir défini la configuration de couplage à adopter pour assurer le bon fonctionnement de l’ensemble et garantir à la fois la sécurité et le confort des occupants, les performances de plusieurs prototypes de conduit échangeur sont caractérisées expérimentalement. Les résultats obtenus lors des essais en laboratoire permettent alors d’orienter l’évolution des prochains prototypes et de souligner la nécessité de travailler avec un poêle à granulés de bois dont le cycle de combustion est étanche. Un modèle mathématique est également développé pour prédire les performances du dernier prototype de conduit échangeur à triple paroi non isolé sur sa surface extérieure et sa validation est obtenue suite au bon accord entre les résultats calculés et ceux mesurés lors des essais. L’ensemble du système combiné est ensuite installé dans deux habitations à basse consommation d’énergie situées près de Poitiers. L’exploitation des températures et des consommations recueillies pendant la première saison de chauffe montre la bonne tenue du système combiné, ses limites, ainsi que ses conditions d’appropriation par les occupants, dont le comportement apparaît jouer un rôle prédominant dans la réduction des consommations énergétiques. / This work is devoted to the study and development of an innovative wood-based air-heating system for energy-efficient dwellings, which are expected to become the building reference in France from 2015 onwards. As these kinds of homes are highly insulated and particularly airtight, heating requirements are very low and may be covered by a renewable energy source, such as wood energy. In addition, efficient ventilation is absolutely required to ensure indoor air quality and may even sometimes be use as the only way to provide heat into the various rooms of the house. In this context, the system presented in this study aims to combine advantages of a low power wood-burning appliance, as a wood-pellet stove, and those of a mechanical ventilation heat-recovery unit, thanks to a heat exchanger integrated into the chimney of the pellet stove and connected to the ventilation air supply network. Developed in partnership with POUJOULAT, a metallic chimneys manufacturer, this new heat exchanger recovers a part of the heat from flue gases and enables to warm up the fresh air distributed in each living zone of the house, even the most remote of the wood heating device. After defining the best coupling configuration to ensure the proper behaviour of the system, as well as both safety and comfort of the occupants, performances of several heat exchanger prototypes are characterized experimentally. The results from tests in laboratory are then used to guide prototypes development and they highlight the need to work with a room-sealed wood-pellet stove. Moreover, a mathematical model is developed to predict the performances of the latest prototype of triple concentric tube heat exchanger with no insulation at the outer surface. Then, the model validation is obtained following the good agreement between calculated results and those measured during the laboratory tests. The combined system is then installed in two energy-efficient dwellings near Poitiers. Operating temperatures and energy consumptions collected during the first heating season show the good reliability of the combined system, its limitations and its conditions of acceptance by the occupants, whose behaviour is pointed out as a major factor in reducing energy consumptions.

Diplomová práce je rozdělena na tří částí. První částí je analýza tématu, cílů a způsobů řešení, která obsahuje i teoretickou část. Druhá část je aplikace tématu na řešeném objektu včetně podrobného výpočtu a návrhu otopné soustavy, přípravy teplé vody, dvou variant alternativních zdrojů tepla a jejich porovnání, které vede k výběru lepšího zdroje tepla. Třetí část je projekt a obsahuje technickou zprávu vybrané varianty a projektovou dokumentaci, která obsahuje všechny potřebné výkresy.