932 resultados para Heat pump, Solar Energy, Ambient Energy, Evaporator Collector, Collector Efficiency
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Torrefaction is a mild pyrolysis process (usually up to 300 degrees C) that changes the chemical and physical properties of biomass. This process is a possible pre-treatment prior to further processes (transport, grinding, combustion, gasification, etc) to generate energy or biofuels. In this study, three eucalyptus wood species and bark were subjected to different torrefaction conditions to determine the alterations in their structural and energy properties. The most severe treatment (280 degrees C, 5 h) causes mass losses of more than 35%, with severe damage to anatomical structure, and an increase of about 27% in the specific energy content. Bark is more sensitive to heat than wood. Energy yields are always higher than mass yields, thereby demonstrating the benefits of torrefaction in concentrating biomass energy. The overall mass loss is proposed as a relevant parameter to synthesize the effect of torrefaction conditions (temperature and duration). Accordingly, all results are summarised by analytical expressions able to predict the energy properties as a function of the overall mass loss. These expressions are intended to be used in any optimization procedure, from production in the field to the final use. (c) 2010 Elsevier Ltd. All rights reserved.
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A DC-DC step-up micro power converter for solar energy harvesting applications is presented. The circuit is based on a switched-capacitorvoltage tripler architecture with MOSFET capacitors, which results in an, area approximately eight times smaller than using MiM capacitors for the 0.131mu m CMOS technology. In order to compensate for the loss of efficiency, due to the larger parasitic capacitances, a charge reutilization scheme is employed. The circuit is self-clocked, using a phase controller designed specifically to work with an amorphous silicon solar cell, in order to obtain themaximum available power from the cell. This will be done by tracking its maximum power point (MPPT) using the fractional open circuit voltage method. Electrical simulations of the circuit, together with an equivalent electrical model of an amorphous silicon solar cell, show that the circuit can deliver apower of 1132 mu W to the load, corresponding to a maximum efficiency of 66.81%.
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In a world increasingly conscientious about environmental effects, power and energy systems are undergoing huge transformations. Electric energy produced from power plants is transmitted and distributed to end users through a power grid. The power industry performs the engineering design, installation, operation, and maintenance tasks to provide a high-quality, secure energy supply while accounting for its systems abilities to withstand uncertain events, such as weather-related outages. Competitive, deregulated electricity markets and new renewable energy sources, however, have further complicated this already complex infrastructure.Sustainable development has also been a challenge for power systems. Recently, there has been a signifi cant increase in the installation of distributed generations, mainly based on renewable resources such as wind and solar. Integrating these new generation systems leads to more complexity. Indeed, the number of generation sources greatly increases as the grid embraces numerous smaller and distributed resources. In addition, the inherent uncertainties of wind and solar energy lead to technical challenges such as forecasting, scheduling, operation, control, and risk management. In this special issue introductory article, we analyze the key areas in this field that can benefi t most from AI and intelligent systems now and in the future.We also identify new opportunities for cross-fertilization between power systems and energy markets and intelligent systems researchers.
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Trabalho Final de Mestrado para obteno do grau de Mestre em Engenharia Mecnica
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Mestrado em Engenharia Qumica - Ramo Optimizao Energtica na Indstria Qumica
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O trabalho apresentado explora o aproveitamento da energia solar para suprir as necessidades energticas, tanto eltricas como trmicas, de uma habitao tipo 3, recorrendo ao uso de coletores solares, em que o fluido de trabalho gua. As necessidades eltricas sero supridas atravs da produo de energia com recurso a um ciclo de Rankine, em que fluido de trabalho um frigorignio aquecido atravs de um permutador cujo fluido quente ser uma mistura, de gua com anticongelante, aquecida pelo coletor solar. Por outro lado, as necessidades trmicas sero satisfeitas atravs do calor libertado no ciclo de Rankine. Na instalao solar estar integrado um acumulador trmico com apoio energtico, caldeira eltrica, que funcionar nas situaes em que coletor seja insuficiente para satisfazer as necessidades trmicas. No final ser feita uma avaliao econmica para que possa atestar a viabilidade econmica do projeto, tendo em conta os seus custos totais versus as poupanas energticas que este sistema origina.
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Trabalho Final de Mestrado para obteno do grau de Mestre em Engenharia Mecnica
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Stand alone solar powered refrigeration and water desalination, two of the most popular and sought after applications of solar energy systems, have been selected as the topic of research for the works presented in this thesis. The water desalination system based on evaporation and condensation was found to be the most suitable one to be powered by solar energy. It has been established that highoutput fast-response solar heat collectors used to achieve high rates of evaporation and reliable solar powered cooling system for faster rates of condensation are the most important factors in achieving increased outputs in solar powered desalination systems. Comprehensive reviews of Solar powered cooling/refrigeration and also water desalination techniques have been presented. In view of the fact that the Institute of Technology, Sligo has a well-established long history of research and development in the production of state of the art high-efficiency fast-response evacuated solar heat collectors it was decided to use this know how in the work described in this thesis. For this reason achieving high rates of evaporation was not a problem. It was, therefore, the question of the solar powered refrigeration that was envisaged to be used in the solar powered desalination tofacilitate rapid condensation of the evaporated water that had to be addressed first. The principles of various solar powered refrigeration techniques have also been reviewed. The first step in work on solar powered refrigeration was to successfully modify a conventional refrigerator working on Platen-Munters design to be powered by highoutput fast-response evacuated solar heat collectors. In this work, which was the first ever successful attempt in the field, temperatures as low as 19C were achieved in the icebox. A new approach in the use of photovoltaic technology to power a conventional domestic refrigerator was also attempted. This was done by modifying a conventional domestic refrigerator to be powered by photovoltaic panels in the most efficient way. In the system developed and successfully tested in this approach, the power demand has been reduced phenomenally and it is possible to achieve 48 hours of cooling power with exposure to just 7 hours of sunshine. The successful development of the first ever multi-cycle intermittent solar powered icemaker is without doubt the most exciting breakthrough in the work described in this thesis. Output of 74.3kg of ice per module with total exposure area of 2.88 m2, or 25.73kg per m2, per day is a major improvement in comparison to about 5-6kg of ice per m2 per day reported for all the single cycle intermittent systems. This system has then become the basis for the development of a new solar powered refrigeration system with even higher output, named the composite system described in this thesis. Another major breakthrough associated with the works described in this thesis is the successful development and testing of the high-output water desalination system. This system that uses a combination of the high-output fast-response evacuated solar heat collectors and the multi-cycle icemaker. The system is capable of producing a maximum of 141 litres of distilled water per day per module which has an exposure area of 3.24m2, or a production rate of 43.5 litres per m2 per day. Once again when this result is compared to the reported daily output of 5 litres of desalinated water per m per day the significance of this piece of work becomes apparent. In the presentation of many of the components and systems described in this thesis CAD parametric solid modelling has been used instead of photographs to illustrate them more clearly. The multi-cycle icemaker and the high-output desalination systems are the subject of two patent applications.
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In this article, a real-world case- study is presented with two general objectives: to give a clear and simple illustrative example of application of social multi-criteria evaluation (SMCE) in the field of rural renewable energy policies, and to help in understanding to what extent and under which circumstances solar energy is suitable for electrifying isolated farmhouses. In this sense, this study might offer public decision- makers some insight on the conditions that favour the diffusion of renewable energy, in order to help them to design more effective energy policies for rural communities.
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Estudi realitzat per avaluar la possibilitat i viabilitat dinstallaci de panells solar fotovoltaics als terrats de les comunitats de vens del Districte de lEixample de Barcelona. La seva finalitat s conscienciar a la poblaci sobre la problemtica actual del canvi climtic fent s de la ciutat com a element clau per a fomentar lestalvi de consum energtic i la reducci demissions de dixid de carboni (CO2). Els resultats obtinguts ens donen un valor aproximat de la superfcie i potncia necessria pels habitants de la ciutat de Barcelona i Catalunya, per tal de cobrir el seu consum delectricitat ds domstic amb energia solar fotovoltaica, aix com una comparativa amb els resultats obtinguts en el Districte de lEixample en les dimensions: socio-econmica, mediambiental i poltica.
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Treball de recerca realitzat per alumnes d'ensenyament secundari i guardonat amb un Premi CIRIT per fomentar l'esperit cientfic del Jovent l'any 2009. Desprs d'una breu introducci sobre l'energia solar, l'estudi analitza quin s el procs de fabricaci que se segueix per fer les plaques solars fotovoltaiques policristallines i monocristallines i quin s el seu funcionament. s a dir, com s possible obtenir energia elctrica grcies a la llum del Sol. Tamb es descriuen les installacions autnomes i les connectades a la xarxa, aix com els elements que les integren. S'inclou, a ms, un punt explicant quins sn els factors que condicionen l'obtenci d'energia i els avenos ms recents en aquest camp de la tecnologia. Per finalitzar la part terica, s'analitza una installaci fotovoltaica situada a Cervera i la seva producci. Pel que fa al treball de camp, es va construir un seguidor solar.
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Tm tutkimus tehtiin osana Vapo Oy:n uuden turvetuotantotekniikan kehityst. Kihnin Aitonevalle on rakennettu uuden turvetuotantotekniikan tutkimusalue, johon kuuluu muun muassa yksi lmmittmtn kuivatuskentt sek yksi aurinkolmmll lmmitetty kuivatuskentt aurinkokerimineen ja putkistoineen. Tyn tavoitteena oli selvitt aurinkolmmll lmmitetyn kuivatuskentn tuotannon teho verrattuna lmmittmttmn kenttn. Toinen tavoite oli selvitt Aitonevan tutkimusalueella kytss olevista aurinkokerimist turpeen kuivaustarkoitukseen parhaiten soveltuva kerin. Tuotantoa uudella menetelmll tehtiin vuoden 2005 kesn ajan. Tuotantotehon ero pyrittiin selvittmn seuraamalla yksittisten turvetuotantoerien eli satokiertojen kuivumista kosteusnyttein ja toisaalta vertaamalla koko kesn aikana saatua tuotantoa. Aurinkokerimien vertailu toteutettiin energiamr- ja hytysuhdemittauksin. Lisksi kuivatuskenttien lmptiloja mitattiin kentss tapahtuvan lmmnsiirron selvittmiseksi. Mittausten perusteella havaittiin, ettlmmitetyn ja lmmittmttmn kentn vlill on tutkimuksen aikaisella kenttrakenteella 6-8 % ero satokierron aikana haihdutetussa vesimrss. Tt voidaanpit odotuksia pienempn. Kenttien lmptilamittausten perusteella osoittautui, ett kentn pintarakenne tulisi erist maaperst, koska kentn alle siirretty lmp siirtyy hviin kylmn pohjamaahan. Kytss olleista aurinkokerimist parhaaksi osoittautui katettu kumimattokerin niin hytysuhteen kuin tehokkuudenkin puolesta. Tyn aikana todettiin, ett tutkimusta kerimien ja varsinkinkenttrakenteen suhteen tulee jatkaa tulevaisuudessa ennen aurinkokerinkentn laajamittaisen kytn aloittamista.
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Tehokkaimpia keinoja vhent rakennusten lmmitysenergian kulutusta ja lmmityksen aiheuttavia hiilidioksidi- ja happamoitavia pstj on tiukentaa rakentamismrysten lmmneristysvaatimuksia. Hyvin lmmneristetyiss, tiiveiss ja ilmanvaihdoltaan optimoiduissa taloissa on pienet lmphvit. Nin ymprist kuormittava vaikutus saadaan paljon vhemmksi kuin nykynormien mukaisissa asuinrakennuksissa. Johtumislmphvi pienenee suoraan eristekerroksia paksuntamalla ja siihen on helpointa vaikuttaa. Mit suurempiin eristepaksuuksiin mennn sen suuremmaksi tulee konvektion osuus kokonaislmphvist. Tulevaisuudessa parempia ratkaisuja haetaan erityisesti konvektiosta ja steilyst aiheutuvien lmphviiden pienentmiseksi. Eristeen osastointi ilmanpitvill, vesihyry diffuusisesti lpisevill pystysuuntaisilla konvektiokatkoilla vhent tehokkaasti paksun seineristeen kuljettumis-ilmavirtauksia. Katkoina kytetn erilaisia kalvoja ja rakennuspapereita, joilla on pieni emissiviteetti. Katkojen merkitys kasvaa, kun mennn uusien normien mukaisiin eristepaksuuksiin. Lmmneriste voidaan toteuttaa mys kokoamalla ohuita kalvoja paketiksi, jotka jakavat ilmatilan ja siis eristeelle varatun paksuuden suljettuihin ilmavleihin. Kun kalvoiksi valitaan pieniemissiviteettisi pintoja, saadaan steilylmmnsiirto lhes eliminoiduksi. Tllaisen ilmatilan lmmnjohtumisluku lhestyy paikallaan pysyvn ilman lmmnjohtumislukua, l = 0,025 W/Km, eli tll rakennesysteemill on mahdollista toteuttaa ohuempia rakenteita kuin perinteisill eristeill. Hygroskooppisen massan kytt sisilman kosteutta tasaavana rakenteena voi olla tulevaisuutta. Kehitysty tuottaa uusia, kosteusteknisesti toimivia sovelluksia. Toisaalta palomrykset tulevat kehitystyt vastaan. Hygroskooppinen pintamateriaali on kevyt (pieni tiheys) ja paloteknisesti arka. Suoraa shklmmityst ei voida pit ympristystvllisen. Sen jalostusketju on pitk ja monivaiheinen. Mill peruspolttoaineella shk tuotetaan, vaikuttaa asiaan luonnollisestikin. Suoraa shklmmityst voidaan suositella vain yksinisen ihmisen taloudessa lmmitysmuotona taloudellisista syist. Halvan polttoaineen sstll ei voida maksaa suuria laiteinvestointeja. Aurinkoenergian hyv hydyntminen edellytt hyv st, joka kytkee lmmityksen pois plt silloin, kun aurinko lmmitt. Auringon hetkelliset steilytehot ovat suuria verrattuna rakenteen lmphviihin ja huonetilojen lmmntarpeeseen. Ratkaisu aurinkoenergian hetkellisyyteen ja paikallisuuteen on energian siirtminen lmmntarpeen mukaan rakennuksen eri osiin ja sen varastoiminen pivtasolla. Kun varastoivasta massasta ei ole suoraa yhteytt ulos, voidaan kerjeristeelt saatu lmp kytt hvittmsti huonetilojen lmmittmiseen. Vaikka lmmitysenergian kytss pstn 30 % vhennyksiin uudisrakennusten osalta, ei kokonaisenergian kytt merkittvsti pienene, jos talousshkn kulutus pysyy vakiona. Sama ptee mys CO2 -pstihin. Saavutettava etu lmmitys-energian kulutuksessa voidaan hukata yh suurenevaksi talousshkn kytksi, mik olisi erityisen huono asia ympristn kannalta.
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The conversion of solar energy into more useful forms of energy, such as chemical fuels or electricity, is one of the central problems facing modern science. Progress in photochemistry and chemical synthesis has led to a point where light energy conversion by means of artificial molecular devices can be rationally attempted. In this article, a general approach towards this challenging goal is presented.
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The main purpose of this thesis is to measure and evaluate how accurately the current energy saving calculation in ABBs new variable speed drive ACS850 works. The main topic of this thesis is energy-efficiency parameters. At the beginning of this thesis centrifugal pump, squirrel cage motor and variable speed drive, including some equations related to them, are being introduced. Also methods of throttling control and variable speed drive control of centrifugal pumps are being introduced. These subjects are introduced because the energy saving calculation in ACS850 is related to the centrifugal pumps usually driven by squirrel cage motors. The theory also includes short section about specific energy of pumping. Before measurements the current energy saving calculation of ACS850 is being introduced and analyzed. The measurements part includes introduction of measuring equipment, measurement results, summary and analysis of the measurements. At the end of this thesis a proposal for an improvement to the current energy saving calculation is being introduced and few proposals are made for new energy-efficiency parameters, which could be added to variable speed drives. At the end are also thoughts
