Virtaavan veden hyödyntäminen keskitetyssä lämmöntuotannossa

Tässä työssä tutkittiin uudenlaista kaukolämmön tuotantotapaa, joka perustuu lämmöntal-teenottoon jokivedestä lämpöpumpuilla. Tutkimuksessa luotiin kokonaiskuva uudenlaisen lämmöntuotannon toiminnasta, sekä selvitettiin tuotannon soveltumista Suomeen. Tuotan-non kattavuus selvitettiin laskennan avulla käymällä läpi kaikki kaukolämpöä myyvien yri-tysten kaukolämpöverkot. Verkoston kulutustietoihin yhdisteltiin jokien virtaamatietoja. Laskenta tehtiin taulukkolaskentaohjelmalla ja kohteita oli yhteensä 184. Työssä tutkittiin myös laitoksen ympäristövaikutuksia lämpövaraston, jokiekosysteemin ja hiilidioksidipäästöjen osalta. Merkittävimmät vaikutukset tulisivat Suomen ilmastossa suu-riksi muodostuvien lämpövarastojen rakentamisesta. Jokiekosysteemin kannalta laitoksen toiminnan vaikutukset osoittautuivat pääasiassa positiivisiksi. Hiilidioksidipäästöjen lasken-nassa laitos oletettiin täysin päästöttömäksi, koska sähköverkkoa tarkasteltiin vuoden 2050 näkökulmasta, jolloin sähköntuotannon oletettiin olevan päästötöntä. Laskennasta selvisi, että laitoksilla pystyttäisiin kattamaan 22,7 % kaukolämmityksen tar-peesta. Tämä tarkoittaisi noin 1,6 milj. tonnin hiilidioksidipäästöjen välttämistä vuositasolla. Laitostyypin todettiin soveltuvan paremmin vain kesänaikaisen lämmöntarpeen kattami-seen. Talviaikainen lämmöntarve olisi parempi kattaa jollakin muulla ratkaisulla.

Secagem da microalga Spirulina em camada delgada utilizando secador com bomba de calor

A Spirulina apresenta propriedades antioxidantes o que favorece seu uso como alimento funcional, fato que tem motivado a sua comercialização para a formulação de alimentos diversos e com finalidades terapêuticas. A secagem ganha importância durante produção de Spirulina, uma vez que a umidade necessária, para garantir que não ocorra degradação da biomassa desidratada durante o armazenamento, é alcançada através do conhecimento dos parâmetros que caracterizam a operação. Neste estudo foi utilizada a secagem com bomba de calor, um método alternativo, pois viabiliza a operação com temperaturas inferiores as tradicionalmente utilizadas, além de seu funcionamento ser independente das condições meteorológicas do ambiente. O trabalho experimental da secagem de Spirulina sp. foi iniciado com um estudo comparativo entre a secagem com bomba de calor (SBC) e a secagem tradicional (ST). O efeito dos diferentes métodos utilizados sob a amostra foi comparado em relação à cinética da operação e as características da microalga desidratada (cor, ficocianina, compostos fenólicos totais e atividade antioxidante total). As temperaturas do ar foram de 50 e 60ºC e a umidade absoluta da SBC foi dez vezes inferior a utilizada durante a ST. Os parâmetros que caracterizam a secagem foram influenciados pela temperatura do ar, bem como, pela baixa umidade absoluta na SBC. Os valores do tempo total da SBC foram 40% inferiores aos encontrados para a secagem ST, em ambas as temperaturas do ar. A maior preservação das características da Spirulina foi obtida na SBC e temperatura do ar de 50°C, e nesta condição os valores foram 14% (ficocianina), 60% (compostos fenólicos) e 10% (atividade antioxidante) superiores aos encontrados na mesma condição para a ST. Isto evidencia que o método de secagem é determinante na qualidade do produto desidratado. Posteriormente, foi realizado o estudo da cinética da SBC, bem como a otimização da operação de secagem e a reidratação das amostras desidratadas nas diferentes condições de secagem. O estudo foi realizado através de um planejamento fatorial 32, tendo como fatores de estudo a temperatura do ar (30, 40 e 50ºC) e a espessura da bandeja (1, 3 e 5 mm). As respostas utilizadas foram ficocianina, compostos fenólicos, atividade antioxidante total e cor da microalga desidratadas. Também foram realizadas a microscopia eletrônica de varredura (MEV) e as curvas termogravimétricas (DSC) das amostras desidratadas. A secagem apresentou um curto período de taxa constante, delimitado pela umidade crítica, sendo que, seus valores foram influenciados apenas pela temperatura do ar de secagem. O modelo Logarítmico forneceu elevados valores de R2ajust e os menores valores de soma dos erros quadráticos (SSE) e de critério informativo de Akaike (AIC). Os valores das energias de ativação para as espessuras de 1, 3 e 5 mm, foram na faixa de 20-23 kJ mol-1. A condição de operação mais adequada, para a secagem de Spirulina sp. com bomba de calor, foi obtida na temperatura do ar de 50°C e espessura da bandeja de 5 mm, com valores de ficocianina, compostos fenólicos, atividade antioxidante total e diferença de cor de 19,60 mg g-1, 1508 µgEAG g-1, 52,6% e 5,71, respectivamente. Os termogramas (DSC) evidenciaram que em 50 ºC e espessura de 5 mm, o produto apresentou maior estabilidade térmica. As amostras de Spirulina sp. desidratadas apresentaram estrutura morfológica (MEV), aparentemente, rígida e heterogênea, e os seus percentuais de reidratação corresponderam a 85-91% da umidade da microalga in natura.

Efeitos do extrato de Rhynchelytrum Repens em modelo murino de obesidade e hiperglicemia induzidas por dieta hiperlipídica

Dissertação (mestrado)—Universidade de Brasília, Programa de Pós-Graduação em Ciências da Saúde, 2015.

Sviluppo di un modello Simulink per la gestione termica di un veicolo elettrico a batteria

Obiettivo di questo progetto di tesi è la realizzazione di un modello per la gestione termica di un veicolo elettrico a batteria: l’elettrificazione in ambito automotive richiede un approfondito studio delle problematiche termiche allo scopo di incrementare l’efficienza del veicolo, le performance e la vita della batteria. In particolare, l’oggetto di ricerca consiste nella modellazione di una pompa di calore. Partendo dalla definizione dei requisiti e degli obiettivi del sistema di gestione termica, ogni componente della pompa di calore viene analizzato modellato e connesso all’intero sistema. La modellazione è stata affrontata mediante l’utilizzo dell’ambiente MATLAB/Simulink. Il primo passo è stato avanzato nell’analisi del ciclo termodinamico ideale, analizzando il comportamento di vari fluidi frigorigeni, la funzionalità dei singoli componenti e l’interazione di quest’ultimi al variare delle condizioni di funzionamento, principalmente potenze scambiate, pressioni, temperature e portata massica di refrigerante. Il principale lavoro di simulazione è legato alla realizzazione di un modello configurabile dell’intero apparato di gestione termica della batteria per un veicolo elettrico. Per mezzo dello studio delle relazioni termodinamiche dei componenti principali del ciclo frigorifero sono state valutate tutte le grandezze che variano durante le trasformazioni che compie il fluido refrigerante all’interno del ciclo frigorifero. L’attività di validazione del modello implementato è stata svolta mediante il confronto tra le condizioni del fluido refrigerante determinate mediante le relazioni termodinamiche e quelle ottenute valutando le trasformazioni sui diagrammi di stato dei fluidi frigorigeni trattati. Il modello implementato è da ritenersi primordiale nel contesto legato alla modellazione e controllo dei sistemi di gestione termica per i sistemi propulsivi dei veicoli elettrici a batteria.

Hitsausmenetelmät ja niiden kehittämismahdollisuudet painelaitteiden valmistuksessa

Työn tavoitteena oli painelaitteiden hitsaustuotannon kehittäminen. Keinoina olivat käytössä olevien hitsausprosessienkehittäminen tai niiden käytön tehostaminen ja mahdollisesti muiden hitsausprosessien, kuten plasma-, laser- tai hybridihitsauksen, käyttöönotto. Työn teoriaosassa käsiteltiin painelaitteiden valmistuksessa käytettävät hitsausprosessit ja niiden kehittämiskeinot, hitsauskustannuksen muodostuminen sekä miten näihin kustannuksiin voidaan vaikuttaa. Lisäksi tarkasteltiin painelaitteiden valmistuksessa käytettävien materiaalien hitsattavuutta ja laadunvarmistusta. Tutkimusosuudessa käytiin läpi valmistuksen nykytila ja tehtiin tuotannon analysointi kehittämiskohteeksi valitulle lämmönsiirtimelle. Kehitysehdotuksenatuotannon tehostamiseksi ehdotettiin MAG-täytelanka- ja jauhekaarihitsauksen käytön lisäämistä. Lisäksi ehdotettiin juurituen käyttöä ja hitsauksen mekanisoinnin lisäämistä. Plasma- tai hybridihitsauksen käytöllä todettiin pystyttävän lyhentämään läpimenoaikoja. Ennen laitteistohankintojen tekoa täytyy tehdä lisäselvityksiä soveltuvuuden ja kannattavuuden varmistamiseksi.

Alternative plant protein sources for pigs and chickens in the tropics – nutritional value and constraints: a review

In the tropics, a large number of smallholder farms contribute significantly to food security by raising pigs and poultry for domestic consumption and for sale on local markets. The high cost and, sometimes, the lack of availability of commercial protein supplements is one of the main limitations to efficient animal production by smallholders. Locally-grown forages and grain legumes offer ecological benefits such as nitrogen fixation, soil improvement, and erosion control which contribute to improve cropping efficiency. Besides these agronomical assets, they can be used as animal feeds in mixed farming systems. In this paper we review options to include locally-grown forages and grain legumes as alternative protein sources in the diets of pigs and poultry in order to reduce farmers’ dependence on externally-purchased protein concentrates. The potential nutritive value of a wide range of forages and grain legumes is presented and discussed. The influence of dietary fibre and plant secondary metabolites contents and their antinutritive consequences on feed intake, digestive processes and animal performances are considered according to the varying composition in those compounds of the different plant species and cultivars covered in this review. Finally, methods to overcome the antinutritive attributes of the plant secondary metabolites using heat, chemical or biological treatment are reviewed regarding their efficiency and their suitability in low input farming systems.

A finite element approach to modelling the hydrological regime in horizontal subsurface flow constructed wetlands for wastewater treatment

A Finite Element Analysis (FEA) model is used to explore the relationship between clogging and hydraulics that occurs in Horizontal Subsurface Flow Treatment Wetlands (HSSF TWs) in the United Kingdom (UK). Clogging is assumed to be caused by particle transport and an existing single collector efficiency model is implemented to describe this behaviour. The flow model was validated against HSSF TW survey results obtained from the literature. The model successfully simulated the influence of overland flow on hydrodynamics, and the interaction between vertical flow through the low permeability surface layer and the horizontal flow of the saturated water table. The clogging model described the development of clogging within the system but under-predicted the extent of clogging which occurred over 15 years. This is because important clogging mechanisms were not considered by the model, such as biomass growth and vegetation establishment. The model showed the usefulness of FEA for linking hydraulic and clogging phenomenon in HSSF TWs and could be extended to include treatment processes. © 2011 Springer Science+Business Media B.V.

Design and implementation of a synchronous interleaved boost converter for fuel cell-powered catamaran

The present work describes the different stages of design, implementation, and validation procedures for an interleaved DC-DC boost converter intended for the 2022 Futura, a fuel cell-powered racing catamaran developed by the UniBoAT team. The main goal of the entire design has been the significant reduction of the weight of the converter by removing heat sinks and reducing component size while increasing its efficiency by adopting high-end power switches and the interleaved architecture operated with a synchronous control strategy. The obtained converter has been integrated into the structure containing the fuel cell stack obtaining a fully integrated system. The realized device has been based on an interleaved architecture with six phases controlled digitally through the average current mode control. The design has been validated through simulations carried out using the software LT-Spice, whereas experimental validations have been performed by means of laboratory bench tests and on-field tests. Detailed thermal and efficiency analyses are provided with the bench tests under the two synchronous and non-synchronous operating modes and with the adoption of the phase shedding technique. The prototype implementation and its performance in real operating conditions are also discussed. Eventually, it is underlined as the designed converter can be used in other applications requiring a voltage-controlled boost converter.

Heat losses and thermal performance of commercial combined solar and pellet heating systems

Various pellet heating systems are marketed in Sweden, some of them in combination with a solar heating system. Several types of pellet heating units are available and can be used for a combined system. This article compares four typical combined solar and pellet heating systems: System 1 and 2 two with a pellet stove, system 3 with a store integrated pellet burner and system 4 with a pellet boiler. The lower efficiency of pellet heaters compared to oil or gas heaters increases the primary energy demand. Consequently heat losses of the various systems have been studied. The systems have been modeled in TRNSYS and simulated with parameters identified from measurements. For almost all systems the flue gas losses are the main heat losses except for system 3 where store heat losses prevail. Relevant are also the heat losses of the burner and the boiler to the ambient. Significant leakage losses are noticed for system 3 and 4. For buildings with an open internal design system 1 is the most efficient solution. Other buildings should preferably apply system 3. The right choice of the system depends also on whether the heater is placed inside or outside of the heated are. A large potential for system optimization exist for all studied systems, which when applied could alter the relative merits of the different system types.

Report on IEA Task-14 activities on solar collector systems conference in Rome, 25-29 Jan. 1993

The memebers of IEA (International Energy Agency) Task 14 (Advaced Active Solar Systems) met in Rome during January 1993. The latest developments in several countries were presented and discussed during this meeting. This report describes briefly the recent work carried out on small scale systems in the Domestic Hot Water (DHW) working group of Task 14, as reported by the representatives from Canada, Denmark, Germany, Holland and Switzerland. Klaus Lorenz, SERC, attended the meeting as observer and presented our work on small-tube heat exchangers. Several participants expressed their interest. A summary of his presentation is included in this report.

Gas-filled, flat plate solar collectors

This work treats the thermal and mechanical performances of gas-filled, flat plate solar collectors in order to achieve a better performance than that of air filled collectors. The gases examined are argon, krypton and xenon which all have lower thermal conductivity than air. The absorber is formed as a tray connected to the glass. The pressure of the gas inside is near to the ambient and since the gas volume will vary as the temperature changes, there are potential risks for fatigue in the material. One heat transfer model and one mechanical model were built. The mechanical model gave stresses and information on the movements. The factors of safety were calculated from the stresses, and the movements were used as input for the heat transfer model where the thermal performance was calculated. It is shown that gas-filled, flat plate solar collectors can be designed to achieve good thermal performance at a competitive cost. The best yield is achieved with a xenon gas filling together with a normal thick absorber, where normal thick means a 0.25 mm copper absorber. However, a great deal of energy is needed to produce the xenon gas, and if this aspect is taken into account, the krypton filling is better. Good thermal performance can also be achieved using less material; a collector with a 0.1 mm thick copper absorber and the third best gas, which is argon, still gives a better operating performance than a common, commercially produced, air filled collector with a 0.25 mm absorber. When manufacturing gas-filled flat plate solar collectors, one way of decreasing the total material costs significantly, is by changing absorber material from copper to aluminium. Best yield per monetary outlay is given by a thin (0.3 mm) alu-minium absorber with an argon filling. A high factor of safety is achieved with thin absorbers, large absorber areas, rectangular constructions with long tubes and short distances between glass and absorber. The latter will also give a thin layer of gas which gives good thermal performance. The only doubtii ful construction is an argon filled collector with a normal thick (> 0.50 mm) aluminium absorber. In general, an assessment of the stresses for the proposed construction together with appropriate tests are recommended before manufacturing, since it is hard to predict the factor of safety; if one part is reinforced, some other parts can experience more stress and the factor of safety actually drops.

Electrical Evaluation of a Low Concentrating PVT Collector Based on Performance Ratio

Photovoltaic Thermal/Hybrid collectors are an emerging technology that combines PV and solar thermal collectors by producing heat and electricity simultaneously. In this paper, the electrical performance evaluation of a low concentrating PVT collector was done through two testing parts: power comparison and performance ratio testing. For the performance ratio testing, it is required to identify and measure the factors affecting the performance ratio on a low concentrating PVT collector. Factors such as PV cell configuration, collector acceptance angle, flow rate, tracking the sun, temperature dependence and diffuse to irradiance ratio. Solarus low concentrating PVT collector V12 was tested at Dalarna University in Sweden using the electrical equipment at the solar laboratory. The PV testing has showed differences between the two receivers. Back2 was producing 1.8 energy output more than Back1 throughout the day. Front1 and Front2 were almost the same output performance. Performance tests showed that the cell configuration for Receiver2 with cells grouping (6- 32-32-6) has proved to have a better performance ratio when to it comes to minimizing the shading effect leading to more output power throughout the day because of lowering the mismatch losses. Different factors were measured and presented in this thesis in chapter 5. With the current design, it has been obtained a peak power at STC of 107W per receiver. The solar cells have an electrical efficiency of approximately 19% while the maximum measured electrical efficiency for the collector was approximately 18 % per active cell area, in addition to a temperature coefficient of -0.53%/ ËšC. Finally a recommendation was done to help Solarus AB to know how much the electrical performance is affected during variable ambient condition and be able to use the results for analyzing and introducing new modification if needed.