Anomalous crystallization of hydrogenated amorphous silicon during fast heating ramps

Thermal crystallization experiments carried out using calorimetry on several a-Si:H materials with different microstructures are reported. The samples were crystallized during heating ramps at constant heating rates up to 100 K/min. Under these conditions, crystallization takes place above 700 C and progressively deviates from the standard kinetics. In particular, two crystallization processes were detected in conventional a-Si:H, which reveal an enhancement of the crystallization rate. At100 K/min, such enhancement is consistent with a diminution of the crystallization time by a factor of 7. In contrast, no systematic variation of the resulting grain size was observed. Similar behavior was also detected in polymorphous silicon and silicon nanoparticles, thus showing that it is characteristic of a variety of hydrogenated amorphous silicon materials.

Home Heating and Cooling, 2011

Every year, a typical family in the United States spends around half of its home energy budget on heating and cooling. In Iowa, that percentage can be higher, due to temperature extremes reached during the winter and summer months. Unfortunately, many of those dollars often are wasted, because conditioned air escapes through leaky ceilings, walls and foundations—or flows through inadequately insulated attics, exterior walls and basements. In addition, many heating systems and air conditioners aren’t properly maintained or are more than 10 years old and very inefficient, compared to models being sold today. As a result, it makes sense to analyze your home as a collection of systems that must work together in order to achieve peak energy savings. For example, you won’t get anywhere near the savings you’re expecting from a new furnace if your airhandling ducts are uninsulated and leak at every joint. The most energy-efficient central air-conditioning setup won’t perform to your expectations if your attic insulation is inadequate and can’t reduce solar heat gain to help keep your home cool. And planting the wrong types of trees or shrubs close to your home adversely can affect potential energy savings all year long.

Water Heating, 2011

Although there are many ways to cut you water heating bills, the all fall into two broad categories: reducing the amount of hot water you use and making your water heating system more efficient. Fortunately, there are several strategies that can help you consume less energy and save money - and still meet you hot water needs without sacrificing comfort or practicality. The booklet was designed to answer common questions about hot water systems and to provide you with the information necessary to make informed decision about a wide variety of topics, ranging from repairing hot water faucet leaks an insulation water supply pipes to installing low-flow shower heads and tuning you your existing water heather. You'll also find details on what to consider when it's time to go comparison shopping for a new water heater-including an evaluation of the alternatives to the common gas or electric storage tank unit that's found in the majority of homes in Iowa and across the country.

Influence of ohmic heating on the flow field in thin-layer electrodeposition

In thin-layer electrodeposition the dissipated electrical energy leads to a substantial heating of the ion solution. We measured the resulting temperature field by means of an infrared camera. The properties of the temperature field correspond closely with the development of the concentration field. In particular, we find that the thermal gradients at the electrodes act similar to a weak additional driving force to the convection rolls driven by concentration gradients.

Anomalous crystallization of hydrogenated amorphous silicon during fast heating ramps

Thermal crystallization experiments carried out using calorimetry on several a-Si:H materials with different microstructures are reported. The samples were crystallized during heating ramps at constant heating rates up to 100 K/min. Under these conditions, crystallization takes place above 700 C and progressively deviates from the standard kinetics. In particular, two crystallization processes were detected in conventional a-Si:H, which reveal an enhancement of the crystallization rate. At100 K/min, such enhancement is consistent with a diminution of the crystallization time by a factor of 7. In contrast, no systematic variation of the resulting grain size was observed. Similar behavior was also detected in polymorphous silicon and silicon nanoparticles, thus showing that it is characteristic of a variety of hydrogenated amorphous silicon materials

Solid phase crystallization under continuous heating: kinetic and microstructure scaling laws

The kinetics and microstructure of solid-phase crystallization under continuous heating conditions and random distribution of nuclei are analyzed. An Arrhenius temperature dependence is assumed for both nucleation and growth rates. Under these circumstances, the system has a scaling law such that the behavior of the scaled system is independent of the heating rate. Hence, the kinetics and microstructure obtained at different heating rates differ only in time and length scaling factors. Concerning the kinetics, it is shown that the extended volume evolves with time according to αex = [exp(κCt′)]m+1, where t′ is the dimensionless time. This scaled solution not only represents a significant simplification of the system description, it also provides new tools for its analysis. For instance, it has been possible to find an analytical dependence of the final average grain size on kinetic parameters. Concerning the microstructure, the existence of a length scaling factor has allowed the grain-size distribution to be numerically calculated as a function of the kinetic parameters

Avaluació de la futura gestió i utilització de la biomassa forestal mitjançant un district heating a Bellver de Cerdanya

En aquest article es pretén explicar breument la viabilitat de la futura gestió i utilització de la biomassa forestal de Bellver de Cerdanya mitjançant un district heating al futur barri del Pla de Tomet. Les particularitats per les quals aquest poble és ideal per a aquest projecte són que l'ajuntament és propietari de gairebé un 90% dels boscos situats en aquest municipi; i que alhora ja ha realitzat diverses instal·lacions que utilitzen la biomassa forestal per a calefacció i ACS. La situació econòmica de la comarca és bastant complicada, ja que s'ha basat en el sector turístic i la construcció, però ambdós no passen pel millor moment. El projecte serviria per donar un valor a la biomassa forestal que fins ara no s'ha donat, i alhora s'intenta buscar nous inputs econòmics per a la Cerdanya. En aquest treball també s'analitza quins haurien de ser els futurs tractaments que s'haurien d'aplicar a la forest, tenint en compte les activitats que es realitzen actualment, i evitant en tot moment possibles efectes negatius, com podria ser la sobreexplotació. També es dedica una part del projecte a explicar els sistemes per obtenir i gestionar de forma correcta la biomassa. A continuació es tracta la part més tècnica, realitzant una estimació del possible futur consum energètic del barri del Pla de Tomet, encara no construït; i decidint quins sistema de calderes seria el més adequat, el tipus d’emmagatzematge més apropiat i els passos a seguir per millorar el rendiment del procés de la gestió i extracció de la biomassa. Seguint tots aquests passos s'arriba a la conclusió que aprofitar la biomassa forestal és millor solució que utilitzar combustibles fòssils. A part dels obvis beneficis medi ambientals, també és millor a nivell econòmic, tant pels futurs veïns com per l'ajuntament.

Effect of Oven Heating Time of Asphaltic Concrete on Marshall Stability, MLR-82-02, 1982

It has been observed in the Laboratory that an increase in oven heating time of relatively short duration between mixing and compaction of asphaltic concrete hot mixes can have an effect on the Marshall stability results obtained. The purpose of this short investigation is to determine the effect of oven heating time on the density and stability of hot mixes.

Effect of heating oxyhemoglobin and methemoglobin on microsomes oxidation.

Hemoglobin (Hb) has been proposed to be a major pro-oxidant in raw and cooked meats. To understand the mechanisms and differentiate between the pro-oxidant and antioxidant potential of oxyhemoglobin (OxyHb) and methemoglobin (MetHb), their pro-oxidant activity, protein solubility, radical scavenging capacity, iron content and contribution of non-chelatable iron on lipid oxidation were determined as a function of thermal treatments. The ability of native OxyHb and MetHb to promote lipid oxidation was similar and higher than their corresponding OxyHb or MetHb heated at 68 and 90 degrees C but not different from those at 45 degrees C. The pro-oxidant activity of MetHb heated at 68 and 90 degrees C were similar whereas the pro-oxidant activity of OxyHb heated at 68 degrees C was higher than that heated at 90 degrees C. The decreased pro-oxidant activity of heat-denatured Hb was associated with a decrease in the solubility of heme iron while free iron showed little impact on the lipid oxidation.

Life cycle costs in heating, ventilation and air-conditioning systems with drive

Energy consumption and energy efficiency have become an issue. Energy consumption is rising all over the world and because of that, and the climate change, energy is becoming more and more expensive. Buildings are major consumers of energy, and inside the buildings the major consumers are heating, ventilation and air-conditioning systems. They usually run at constant speed without efficient control. In most cases HVAC equipment is also oversized. Traditionally heating, ventilation and air-conditioning systems have been sized to meet conditions that rarely occur. The theory part in this thesis represents the basics of life cycle costs and calculations for the whole life cycle of a system. It also represents HVAC systems, equipment, systems controls and ways to save energy in these systems. The empirical part of this thesis represents life cycle cost calculations for HVAC systems. With these calculations it is possible to compute costs for the whole life cycle for the wanted variables. Life cycle costs make it possible to compare which variable causes most of the costs from the whole life point of view. Life cycle costs were studied through two real life cases which were focused on two different kinds of HVAC systems. In both of these cases the renovations were already made, so that the comparison between the old and the new, now existing system would be easier. The study indicates that energy can be saved in HVAC systems by using variable speed drive as a control method.

House heating in Finland and Russia

Achievement of house heating efficiency is one of key questions in building construction field. Finland and nothern part of Russia have similar climate conditions that gives a reason for comparation of their house heating approaches. In this work main questions concerned to house heating energy efficiency are studied, building norms and standards of Russia and Finland are studied and compared from heat storage efficiency point of view, review of statistics is done, some different factors influencing house heating energy efficiency are derived.

Feasibility Study and Market Review of Small Scale Bioenergy Heating Plants in North-West Russia

The paper is focused on feasibility study and market review of small scale bioenergy heating plants in the Russian North-West region. The main focus is effective and competitive usage of low-grade wood for heating purposes in the region. As example of economical feasibility estimation it was chosen the project of reconstruction of small scale boiler plant in Leningrad region that Brofta Oy is planning to implement the nearest time. It includes calculation the payback time with and without interest, the estimation of probable investments, the evaluation of possible risks and research on the potential of small scale heating plants projects. Calculations show that the profitability of this kind of projects is high, but payback time is not very short, because of high level of initial investments. Though, the development of small scale bioenergy heating plants in the region is considered to be the best way to solve the problems of heat supply in small settlements using own biomass resources.