Lowcost autonomous electrical energy source

Témou mojej bakalárskej práce je nízkonákladový autonómny zdroj elektrickej energie. Pretože ponuka na trhu v oblasti fotovoltaických systémov je v súčasnosti vežmi široká, je mojou úlohou vybrať lacné a efektívne riešenie solárneho zdroja energie, ktoré bude na výstupe poskytovať tri rôzne úrovne napätia. Zameriavam sa hlavne na prehžad druhov fotovoltaických článkov, porovnanie výrobcov článkov, návrh plošných spojov, realizáciu a overenie správnej funkcie zariadenia. V tejto práci ďalej popisujem problematiku pulzných zdrojov, ktoré sú použité pre prispôsobenie výstupného napätia pre ciežovú aplikáciu. V práci je uvedené riešenie problematiky pomocou rôznych typov meničov.The aim of my bachelor’s work is a low-cost autonomous generator of electrical energy. Since the offer on the market for photovoltaic systems is now very wide, it is my task to select a cheap and effective solution for solar energy generator that will provide three different levels of voltage on the output. I focus especially on the overview of the types of photovoltaic cells and comparison of cells producers. This work also describes switching converters, which will be used for the output voltage conversion for the target system. In the work the solution by different DC/DC regulators is described.

Determination of heat transfer coefficients from the surface of the thermal manikin

Diplomová práca sa zaoberá experimentálnym stanovením súčiniteľov prestupu tepla radiáciou a konvekciou, využitím tepelného manekýna. Ťažisko práce leží v rozdelení tepel-ného toku z povrchu manekýna na radiačnú a konvektívnu zložku. Práca sa zaoberá prestu-pom tepla z povrchu nahého a oblečeného manekýna, v polohách sed a stoj. Merania prebiehali v definovanom prostredí, pri konštantnej teplote a rýchlosti vzduchu (cca 24°C a 0,05 m.s-1). Zložka radiačného tepelného toku sa potláčala poťahom so zníženou emisivitou, resp. dvojdielnym oblekom so zníženou emisivitou. K úspešnému riešeniu úlohy sa podarilo dospieť len v prípade nahého manekýna. Zmeraných bolo 34 zón, ktoré logicky reprezentujú časti ľudského tela. Potvrdili sa teoretické predpoklady prenosu tepla z povrchu tepelného manekýna a výsledky práce boli porovnané s výsledkami obdobnej experimentálnej práce. Výstupy tejto práce umožňujú vytvorenie detailných počítačových modelov tepelného prostredia, ktoré vyžadujú anatomicky špecifické, separátne hodnoty súčiniteľov prestupu tepla radiáciou a konvekciou.This thesis deals with an experimental determination of heat transfer coefficients from the surface of the thermal manikin. The main focus of the work lies on separating radiative and convective heat fluxes from the surface of the thermal manikin. Both nude and clothed, standing and seated postures were investigated respectively. The tests were conducted in a constant air temperature (cca 24°C) and a constant wind speed (cca 0,05 m.s-1) environment. The major part of the radiative heat flux was eliminated by a low emissivity coating applied to the surface of the nude thermal manikin, and in the case of clothed manikin by a low emissivity two-piece dress. Favorable results were achieved only in the case of the nude manikin measurements. The measurements were performed across 34 zones that logically represent parts of a human body. Experimental work confirms theoretical expectations in the means of a heat transfer. In addition, the results of this work were compared to results of a similar experimental work. The outcomes of this thesis provide essential information in order to create detailed computational models of a thermal environment. Such models require anatomically specific, separate values of convective and radiative heat transfer coefficients.

Assesment of the Thermal Environment in Vehicular Cabins

Ľudia žijúci vo vyspelých krajinách trávia väčšinu svojho života vo vnútorných prostrediach budov alebo dopravných prostriedkov. Z tohto dôvodu, záujem o výskum kvality vnútorných prostredím rastie, pričom hlavný dôraz je kladený na oblasti výskumu ľudského zdravia, produktivity a komfortu. Jedným z faktorov ovplyvňujúci kvalitu prostredí je ich tepelný aspekt, ktorý je najčastejšie popísaný teplotou vzduchu, radiačnou teplotou, vlhkosťou vzduchu a rýchlosťou prúdenia vzdu-chu. Zatiaľ čo tieto parametre je možné riadiť systémom pre vykurovanie, vetranie a klimatizáciu nezávisle na počasí, takéto zariadenia sa podieľajú na vysokej spotrebe energie a značnej uhlíkovej stope. V prostediach kabín áut a dopravných prostriedkov je riadenie parametrov tepelného prostredia komplikované z dôvodu ich asymetrickej a časovo premenlivej povahy. Táto situácia je obzvlášť kritická vo vozidlách na elektrický pohon s vlastnou batériou, kde je energia na úpravu vnútornej mikroklímy čerpaná na úkor dojazdu vozidla. Pre uvedené dôvody sa hľadajú nové, en-ergeticky účinnejšie spôsoby pre úpravu tepelných prostredí a zabezpečenia tepelného komfortu. Jedným z potenciálnych riešení sú zariadenia dodávajúce človeku teplo alebo chlad lokálne, ako napríklad vyhrievané a vetrané sedadlá a sálavé panely. Vzhľadom na to, že experimentálny výskum vnútorných prostredí je náročný s ohľadom na čas a potrebné vybavenie, trendy výskumu vplyvov takýchto zariadení na človeka smerujú k optimalizačným úlohám vo virtuálnych prostrediach pomocou modelov ľudksej termofyziológie a tepelného pocitu/komfortu. Avšak pre spoľahlivé výsledky modelovania sú potrebné presné vstupné parametre definujúce prostredie, odev, vplyv povrchov v kontakte s človekom (napríklad sedadlá) a pôsobenie systémov na lokálnu úpravu mikroklímy. Cieľom tejto dizertačnej práce je vytvorenie metodológie na hodnotenie tepelných prostredí v kabínach automobilov s ohľadom na pozíciu v sede a využitím technológii na lokálnu úpravu tepelných prostredí. Jedným z požiadavkov na takúto metodológiu je jej aplikovateľnosť vo virtuálnych ale aj reálnych prostrediach. V prípade hodnotenia reálnych prostredí, cieľom je vytvorenie demonštrátora, ktorý by bol využiteľný ako spätná väzba pre riadenie systémov pre úpravu mikroklímy na základe požadovaného tepeleného pocitu. Validita uvedenej metodológie bola demonštrovaná v typických podmienkach kabín automobilov (5–41 °C) a poznatky z tejto práce sú prenesiteľné do širokého spektra inžinierkych aplikácii. V oblasti osobnej dopravy a pracovných prostredí s vyššou tepelnou záťažou je táto metóda užitočná pre identifikáciu možných zdrojov diskomfortu. Navyše je táto metóda vhodná i pre rýchlo rastúci segment elektrických vozidiel, kde je možné sledovať tok energie potrebnej na dosiahnutie určitej úrovne komfortu a riešenie optimalizačných úloh za účelom úspory energie a predĺženie dojazdu. Obdobné aplikácie možno nájsť i v budovách a prostrediach s podobnými charakteristikami.People in developed countries spend substantial parts of their lives in indoor environments both during free time and while working. For this reason, there has been increasing interest in the quality of the indoor environment. The main emphasis of past research has been directed towards understanding the fields of human health, productivity, and comfort. One important contributor to all three fields is the thermal aspect of the environment, which is often represented by physical quantities such as air temperature, radiant temperature, air humidity, and air velocity. While weather-independent control of these parameters is possible via heating, ventilation, and air-conditioning systems (HVAC), a major limitation is that these systems are related to substantial energy consumption and carbon footprint. The complexity of thermal management is amplified in vehicular cabins because of their asymmetric and transient nature. Moreover, in electric vehicles, the available energy for microclimate management comes at the cost of driving range, and therefore, new solutions for more effective and human-centred ways of managing the indoor microclimate are sought. One of the promising ways to address these issues is via local conditioning with the vehicle seats or auxiliary radiant panels operating in synergy with an HVAC unit. At the same time, the optimization and research tasks are being shifted towards virtual investigation to mitigate the need for costly and often ethically concerning human studies. To do so, models of human thermo-physiology and thermal sensation/comfort have been developed. Yet, for their reliable applications, many factors regarding high heterogeneity, clothing, the thermal mass of the adjacent surfaces, and active seat conditioning have not been resolved. The aim of this thesis was to develop a methodology to assess human thermal sensation while in a sitting body position, including local conditioning factors such as heated and ventilated seats. A requirement of the method was applicability in both virtual and real indoor spaces. In the latter case, the focus was a thermal-sensation-driven feedback loop allowing for human-centred microclimate management. The validity of the proposed methodology was demonstrated under typical cabin conditions (5–41 °C) and the findings from this PhD project are transferable to a broad variety of engineering fields. In passenger transport and occupational environments with higher heat strain, environmental engineers can benefit from a tool to identify sources of thermal discomfort and potential hazards of fatigue. Furthermore, the methodology can be of great merit to the rapidly developing electric vehicle industry, facilitating emphasis on energy efficient microclimate management. The virtual optimization of the conditioning strategies reduce the need for human studies, allow rapid prototyping, and have great potential to bring energy savings as well as increased driving range. Finally, the know-how presented is also applicable in built environments, where similar conditions apply.

Environmental control system of aircraft cabin

V tejto rešeršnej práci sú spracované dostupné informácie o klimatizačných systémoch súčasných dopravných lietadiel, ktoré komplexne riešia úpravu mikroklímy kabín, do podoby prijateľnej a komfortnej pre ľudský organizmus (ECS – environmental control system). Uvádzajú sa dôvody zavedenia ECS a konkrétne požiadavky na mikroklímu kabín s ohľadom na bezpečný pobyt človeka v rôznych letových režimoch. Práca obsahuje popis jednotlivých podsystémov ECS. Vysvetľuje ich funkciu, termomechanický princíp fungovania, rôzne možnosti technického prevedenia ECS a jeho celkovú funkciu. Ďalej sú načrtnuté názorné schémy rozloženia ECS na palube lietadla. Uvedené sú i niektoré prípady negatívneho vplyvu ECS na ostatné systémy lietadla. Súčasne sa odhaľujú technické obmedzenia ECS, ktoré by mohli byť v budúcnosti, zavedením nových technológií, prekonané. Na záver sa zdôrazňuje potreba správnej funkcie ECS.In this research work available information about air-conditioning systems of actual airliners are processed. These systems solve in complexity aircraft cabin microclimate modification into form comfortable and acceptable for the human body (ECS – enviromental control system). The work also covers ECS subsystems description. It explains their function, thermalmechanical principle, different possibilities of their realization and overall ECS function. Examples of ECS negative impact on other aircraft systems are also mentioned. Afterwards, real schemes of ECS built on board are sketched. The paper also presents reasons of ECS introduction, concrete requirements to cabin microclimate out of consideration to safe stay of human bean on board in different flight procedures. Simultaneously technical obstacles and limitations of ECS are shown. In conclusion need of correct ECS function is highlighted.

Measurement of airflow and pressure characteristics of a fan built in a car ventilation system

The aim of this study was to identify a set of operating points of a fan built in ventilation system of our test car. These operating points are given by the fan pressure characteristics and are defined by a pressure drop of the HVAC system (air ducts and vents) and volumetric flow rate of ventilation air. To cover a wide range of pressure drops situations, four cases of vent flaps setup were examined: (1) all vents opened, (2) only central vents closed (3) only central vents opened and (4) all vents closed. To cover a different volumetric flows, the each case was measured at least for four different speeds of fan defined by the fan voltage. It was observed that the pressure difference of the fan is proportional to the fan voltage and strongly depends on the throttling of the air distribution system by the settings of the vents flaps. In case of our test car we identified correlations between volumetric flow rate of ventilation air, fan pressure difference and fan voltage. These correlations will facilitate and reduce time costs of the following experiments with this test car

Airflow Measurement of the Car HVAC Unit Using Hot-wire Anemometry

Thermal environment in a vehicular cabin significantly influence drivers’ fatigue and passengers’ thermal comfort. This environment is traditionally managed by HVAC cabin system that distributes air and modifies its properties. In order to simulate cabin thermal behaviour, amount of the air led through car vents must be determined. The aim of this study was to develop methodology to measure airflow from the vents, and consequently calculate corresponding air distribution coefficients. Three climatic cases were selected to match European winter, summer, and spring / fall conditions. Experiments were conducted on a test vehicle in a climatic chamber. The car HVAC system was set to automatic control mode, and the measurements were executed after the system stabilisation—each case was independently measured three times. To be able to evaluate precision of the method, the airflow was determined at the system inlet (HVAC suction) and outlet (each vent), and the total airflow values were compared. The airflow was calculated by determining a mean value of the air velocity multiplied by an area of inlet / outlet cross-section. Hot-wire anemometry was involved to measure the air velocity. Regarding the summer case, total airflow entering the cabin was around 57 l s-1 with 60 % of the air entering the cabin through dashboard vents; no air was supplied to the feet compartment. The remaining cases had the same total airflow of around 42 l s-1, and the air distribution was focused mainly on feet and windows. The inlet and outlet airflow values show a good match with a maximum mass differential of 8.3 %

Impact of measurable physical phenomena on contact thermal comfort

Cabin HVAC (Heating Ventilation and Air-conditioning) systems have become an essential part of personal vehicles as demands for comfortable transport are still rising. In fact, 85 % of the car trips in Europe are shorter than 18 km and last only up to 30 minutes. Under such conditions, the HVAC unit cannot often ensure desired cabin environment and passengers are prone to experience thermal stress. For this reason, additional comfort systems, such as heated or ventilated seats, are available on the market. However, there is no straightforward method to evaluate thermal comfort at the contact surfaces nowadays. The aim of this work is to summarise information about heated and ventilated seats. These technologies use electrical heating and fan driven air to contact area in order to achieve enhanced comfort. It is also expected, that such measures may contribute to lower energy consumption. Yet, in real conditions it is almost impossible to measure the airflow through the ventilated seat directly. Therefore, there is a need for an approach that would correlate measurable physical phenomena with thermal comfort. For this reason, a method that exploits a measurement of temperatures and humidity at the contact area is proposed. Preliminary results that correlate comfort with measurable physical phenomena are demonstrated

Optimalization and methods of internal resistance measurement of the lead acid battery cell

Témou diplomovej práce je optimalizácia a metódy merania vnútorného odporu oloveného akumulátoru. Práca sa najprv zameriava na delenie, rozbor vlastností olovených akumulátorov, konštrukciu a negatívne javy. Následne je spracovaná metóda merania vnútorného odporu experimentálneho článku s praktickým návrhom meracieho pracoviska. V práci sa vykonáva frekvenčná analýza impedancie nabitého a vybitého článku. Následne sú spracované grafické znázornenia vnútorného odporu pre rôzne veľkosti amplitúd, pre rôzne druhy signálov a rôzne veľkosti frekvencií striedavého prúdu. Výsledkom práce je porovnanie jednotlivých grafických závislostí vybíjacích a nabíjacích charakteristík článku a stanovenie optimálnej ampitúdy, tvaru a veľkosti frekvencie striedavého prúdu, kedy je vnútorný odpor vyhodnocovaný správne.The aim of this master´s thesis is optimalization and methods of measuring the internal resistance of lead acid accumulator. First focus is on the analysis of properties of lead acid accumulators, their construction and negative effects. After that a method of measuring the internal resistance of experimental accumulator is processed. In this thesis practical design of measuring workplace is completed. The frequency analysis of impedance of charging and discharging accumulator is performed. After that the graph of internal resistance for various amplitude intensities, for various signal forms and also for various size of frequencies of alternating current are processed. The result of this thesis is a comparison of graphic works addictions charging and discharging characteristics of lead acid accumulator and determination of optimal amplitude, form and intensity of frequency of alternating current in point when internal resistance is evaluated correctly.

Airflow Measurement of the Car HVAC Unit Using Hot-wire Anemometry

Thermal environment in a vehicular cabin significantly influence drivers’ fatigue and passengers’ thermal comfort. This environment is traditionally managed by HVAC cabin system that distributes air and modifies its properties. In order to simulate cabin thermal behaviour, amount of the air led through car vents must be determined. The aim of this study was to develop methodology to measure airflow from the vents, and consequently calculate corresponding air distribution coefficients. Three climatic cases were selected to match European winter, summer, and spring / fall conditions. Experiments were conducted on a test vehicle in a climatic chamber. The car HVAC system was set to automatic control mode, and the measurements were executed after the system stabilisation—each case was independently measured three times. To be able to evaluate precision of the method, the airflow was determined at the system inlet (HVAC suction) and outlet (each vent), and the total airflow values were compared. The airflow was calculated by determining a mean value of the air velocity multiplied by an area of inlet / outlet cross-section. Hot-wire anemometry was involved to measure the air velocity. Regarding the summer case, total airflow entering the cabin was around 57 l s-1 with 60 % of the air entering the cabin through dashboard vents; no air was supplied to the feet compartment. The remaining cases had the same total airflow of around 42 l s-1, and the air distribution was focused mainly on feet and windows. The inlet and outlet airflow values show a good match with a maximum mass differential of 8.3 %

Measurement of airflow and pressure characteristics of a fan built in a car ventilation system

The aim of this study was to identify a set of operating points of a fan built in ventilation system of our test car. These operating points are given by the fan pressure characteristics and are defined by a pressure drop of the HVAC system (air ducts and vents) and volumetric flow rate of ventilation air. To cover a wide range of pressure drops situations, four cases of vent flaps setup were examined: (1) all vents opened, (2) only central vents closed (3) only central vents opened and (4) all vents closed. To cover a different volumetric flows, the each case was measured at least for four different speeds of fan defined by the fan voltage. It was observed that the pressure difference of the fan is proportional to the fan voltage and strongly depends on the throttling of the air distribution system by the settings of the vents flaps. In case of our test car we identified correlations between volumetric flow rate of ventilation air, fan pressure difference and fan voltage. These correlations will facilitate and reduce time costs of the following experiments with this test car