Precipitation phase is fundamental to a catchment’s hydrological response to precipitation events in cold regions and is especially variable over time and space in complex topography. Phase is controlled by the microphysics of the falling hydrometeor, but microphysical calculations require detailed atmospheric information that is often unavailable and lacking from hydrological analyses. In hydrology, there have been many methods developed to estimate phase, but most are regionally calibrated and many depend on air temperature (Ta) and use daily time steps. Phase is not only related to Ta, but to other meteorological variables such as humidity. In addition, precipitation events are dynamic, adding uncertainties to the use of daily indices to estimate phase. To better predict precipitation phase with respect to meteorological conditions, the combined mass and energy balance of a falling hydrometeor was calculated and used to develop a model to estimate precipitation phase. Precipitation phase and meteorological data were observed at multiple elevations in a small Canadian Rockies catchment, Marmot Creek Research Basin, at 15-minute intervals over several years to develop and test the model. The mass and energy balance model was compared to other methods over varying time scales, seasons, elevations and topographic exposures. The results indicate that the psychrometric energy balance model performs much better than Ta methods and that this improvement increases as the calculation time interval decreases. The uncertainty that differing phase methods introduce to hydrological process estimation was assessed with the Cold Regions Hydrological Model (CRHM). The rainfall/total precipitation ratio, runoff, discharge and snowpack accumulation were calculated using a single and a double Ta threshold method and the proposed physically based mass and energy balance model. Intercomparison of the hydrological responses of the methods highlighted differences between Ta based and psychrometric approaches. Uncertainty of hydrological processes, as established by simulating a wide range of Ta methods, reached up to 20% for rain ratio, 1.5 mm for mean daily runoff, 0.4 mm for mean daily discharge and 160 mm of peak snow water equivalent. The range of Ta methods showed that snowcover duration, snow free date and peak discharge date could vary by up to 36, 26 and 10 days respectively. The greatest hydrological uncertainty due to precipitation phase methods was found at sub-alpine and sub-arctic headwater basins and the least uncertainty was found at a small prairie basin.

Final Master Thesis report EGI 2010-2013   Thesis Title: The Role of Renewable Energies in Energy supply Planning and   Management for Sustainable    Development “Case of Rwanda”. ABSTRACT   This report provides an overview of the main results from the scenarios analysed in the Rwanda energy policy strategy, planning and prospective energy initiatives and alternatives (Hydropower, Biomass, Solar, Methane, Peat, etc.) as well as other Government Development Frameworks meant for poverty reduction strategies and economic development. Under this context, the report attempts to assess the role of renewable energies particularly micro hydropower in solving Rwanda energy supply and management issues for sustainable development. The main conclusion is that renewable energies (micro hydropower) substantially contribute to reducing greenhouse gas emissions and improving diversification of the energy production and supply into the national grid as well as independent off-grid systems particularly in rural based areas that are far from the grid. This becomes even more significant and relevant when considering that electricity access in the country stands at about 14% leaving about 86% of the population especially in rural areas without power supply. Although other technologies are still used to meet urgent and pressing power demand, Renewable energy sources are well placed in offering medium and long term solution in a sustainable manner. To this effect therefore, the report has tried to outline the impacts, costs and benefits of ambitious renewable energy targets for Rwanda in the medium and long term perspectives.

The study is experimentally inclined, with a high target precision for performance measurement. A comprehensive programme of measurements was carried out in a two-storey building, having a massive structure and dating from 1970. Measurements were made continuously during the heating season from a total of about 70 points. Readings were taken every 30 seconds, and the mean values stored in a computer every 15 minutes. Analysis of the results have been concentrated on: * Thermal inertia, and particularly that of cooling mechanisms. * Time delays in heat flows through the building envelope in response to variations in ambient temperature. * The amount of solar input beneficially retained when operating with night setback and with normal operation. The results indicate that the building has both a long time constant, of about 200 h, and a short one, of about 1.5 h. The magnitude of the shorter time constant depends on the thermal capacity of the interior of the building (furniture, curtains etc.), and can be regarded as having some validity for other apartment building stock. Analyses of temperature gradients in the internal surfaces of the exterior walls indicate that the building's ventilation system, which was originally constructed as an exhaust air ventilation system, but with the inflow of fresh air blocked off, generates a dynamic insulation effect. Calculations indicate that this effect can provide a saving of 6 % of the total heating requirement, excluding that for domestic hot water. Investigation of the static heat requirement with and without night set-back indicate a considerable potential annual saving of heating energy, amounting to a maximum of 13 %, provided that the building is heated in accordance with a prescribed strategy. A 'comfort indoor temperature' has also been determined, being the temperature above which the occupants of the building consume excessive heating energy. Theoretical models have been derived to illustrate the short time constant and to analyse the dynamic insulation effect noted. / <p>Diss. Umeå : Umeå universitet, 1987</p> / digitalisering@umu

Leptin is a peripheral adiposity signal and a key hormone in energy balance regulation in mammals, acting as a link between nutritional status and the endocrine reproductive axis. If this is also the role of leptin in fish is not fully understood. This thesis investigates how different components of the leptin system are affected by sexual maturation and seasonal changes in energy balance in male Atlantic salmon (Salmo salar L.) parr under fully fed and feed-restricted conditions. Moreover, the role of sex steroids as being one of the possible mechanisms by which sexual maturation interacts with leptin is explored. The salmon leptin-a genes, lepa1 and lepa2, were expressed mainly in liver and the leptin receptor (lepr) in brain and ubiquitously in peripheral tissues. Seasonal characterization of the lepa genes and lepr during the growth and reproductive season in one-year old males showed that hepatic lepa1 and lepa2 mRNA levels and plasma leptin levels were down-regulated concomitantly with an increase in weight and body fat. Feed restriction up-regulated hepatic leptin, and pituitary lepr expression as well as plasma leptin levels. Correlation between leptin levels and body lipid stores were either lacking or negative. These findings show that leptin and lepr are sensitive to changes in energy balance, but that leptin might not reflect adiposity in juvenile salmon. Hepatic lepa1 and lepa2, and testicular lepr expression increased during mid- to late spermatogenesis in early maturing males. This up-regulation was preceded by rapid gonadal growth and elevated pituitary follicle-stimulating hormone gene expression levels, whereas peak leptin levels coincided with peak pituitary luteinizing hormone expression and the presence of running milt in the testes. The sex steroids testosterone (T), 11-ketotestosterone and 17-β estradiol stimulated lepa1 and lepa2 gene expression in Atlantic salmon hepatocytes in vitro differentially depending on developmental stage. T was also able to stimulate hepatic lepa1 and pituitary lepa1 and lepr gene expression in immature male salmon in vivo. These results suggest that leptin plays a role in male fish reproduction during later stages of the maturational process and that the elevation of leptin expression during spermatogenesis could be caused by androgen stimulation.

Objective. To compare energy balance and nutrient intake of elite and non-elite school-aged gymnasts, as well as to evaluate their nutritional knowledge and eating attitude and its effect on dietary intake and practices. Methods. Demographic information, anthropometric measurements, menstrual status, sources of nutritional information, nutritional habits as well as supplement use was documented. Eating attitudes were measured by the EAT26 test and nutritional knowledge by a standardised questionnaire. Dietary intake and practices were determined with a 3-day weighed food record, while energy expenditure was measured with an Actical® accelerometer (Mini Mitter Co., Inc. Bend, OR, USA). Results. The total daily energy intake (non-elite = 6 944.37 ± 1 272.28 kJ vs. elite = 6 543.01 ± 2 570 kJ) in both groups was similar to their daily energy expenditure values (non-elite = 6 393.77 ± 1 244.19 kJ vs. elite = 6 696.09 ± 1 676.58 kJ). Elite gymnasts tended to have higher protein (21.37 vs. 15.4% total energy intake (TE), small effect size, d = 0.1) and lower fat (28.9 vs. 33.6% TE, medium effect size, d = - 0.6) intakes. More non-elite gymnasts (n = 7, 88.88%) used micronutrient supplements than elite gymnasts (n = 4, 45.45%, medium effect size, d = 0.45). Most of the gymnasts (55%) ate snacks during the day, which consisted mostly of refined carbohydrates. In the total group of gymnasts the most frequently used source of nutritional information was the coach (60%). There was no difference in nutritional knowledge between the groups (elite = 61.8% vs. non-elite = 62.8% respectively). Lastly, elite gymnasts had a practically significantly higher risk than non-elite gymnasts to follow a diet (large effect size, d = 1.32), while non-elite gymnasts exercised practically significantly more self-control over their food intake com pared to elite gymnasts (large effect size, d = - 1.03). Conclusions. South African elite gymnasts do not differ from non-elite gymnasts in terms of energy-, carbohydrate-, protein-, or fat intake. There is also no difference in energy expenditure or risk in developing an eating disorder, probably due to less competitiveness compared to other international gymnasts. / Thesis (M.Sc. (Dietetics))--North-West University, Potchefstroom Campus, 2005.

Umeå Energi AB har bestämt att en kontroll av pannverkningsgraden för kraftvärmepannan Dåva 2 skall genomföras. I dagsläget genomförs en beräkning av verkningsgraden månadsvis med den direkta beräkningsmetoden. Resultatet varierar dock kraftigt månad till månad varav en undersökning med indirekt beräkningsmetod är av intresse. Arbetet genomförs för att ge en mer noggrant beräknad verkningsgrad samt utreda förlustfaktorer kopplad till pannan. Då pannverkningsgraden i vanliga fall inte inkluderar rökgaskondensering beräknades också totalverkningsgraden för att ge en mer rättvis bild av pannan samt för att illustrera dess relevans. Arbetet genomfördes för två olika driftsfall, hög och låg last, för att undersöka hur verkningsgraden varierar beroende på driftsfall. Arbetet inleddes genom att studera de standarder som finns inom området för att utreda vilka faktorer som skulle beräknas samt vilka kriterier som skulle följas. Det framgick att en hel del provtagningar och analyser skulle genomföras på bland annat bränsle, aska och rökgaser. Detta krävde i sin tur en noggrann planering varav ett provtagningsschema skapades. Samtliga provtagningar genomfördes vid bägge driftsfallen och proverna skickades på analys, därefter kunde verkningsgraden beräknas. Resultatet tyder på hög totalverkningsgrad med något lägre pannverkningsgrad. Beroende på driftsfall varierar pannverkningsgraden mellan 74% vid hög last och 72% vid låg last. Totalverkningsgraden ligger på 92% vid hög last och 91% vid låg last. Den förlustfaktor som är av störst magnitud är rökgasförluster som beror av rökgasernas fukthalt och temperatur. Rökgasförlusterna varierar mellan 24% till 26% för pannverkningsgraden och 6.6% till 7.2% för totalverkningsgraden. Utöver rökgasförlusterna ligger strålningsförlusterna på runt 0.7% vid bägge driftsfallen. Förbränningsförlusterna är mycket låga och varierar mellan 0.52% och 0.53% vilket i kombination med de låga askförlusterna (0.006%-0.04%) tyder på mycket bra förbränning. På grund av de höga verkningsgraderna framkom inga självklara effektiviseringsåtgärder. Då rökgasförlusterna är de största förlustfaktorerna är därför åtgärder mot dessa av störst betydelse för verkningsgraden. Ett alternativ för att öka verkningsgraden ytterligare är att minska fukthalten på de utgående rökgaserna. De är i dagsläget runt 9% och står för majoriteten av rökgasförlusterna. En sänkning av denna fukthalt kan erhållas genom att sänka temperaturen på rökgaserna och på så vis kondensera mer fukt ur rökgaserna. Detta innebär att temperaturen på kondensatet i rökgaskondenseringsanläggningen måste sänkas, vilket i sin tur innebära att antingen sänka fjärrvärmereturen som kyler kondensatet, alternativt installera en värmepump mellan kondensatet och fjärrvärmereturen. Detta kräver dock en djupare utredning för att fastställa om dessa effektiviseringsåtgärder är genomförbara rent tekniskt samt om de är ekonomiskt försvarbara. / Umeå Energi AB has decided that an evaluation of boiler efficiency should be performed on their CHP-plant Dåva 2. Calculation of the efficiency using the input-output method is currently carried out monthly but the results vary greatly over time whereby an evaluation of the efficiency using the energy balance method was of interest. This was done to give a more accurate efficiency and to evaluate boiler losses. Due to the fact that the boiler efficiency doesn’t usually include flue gas condensation two different efficiency were calculated, boiler efficiency and total efficiency.  The boiler and total efficiency was determined for the CHP during two different loads, high and low. This was done to investigate how the efficiency varies with different loads. The work was initiated by studying the standards in the field of efficiency calculations to evaluate which factors and criteria to be calculated and followed.  It was shown that a lot of samplings and analysis was to be performed which demanded accurate sampling interval. A sampling schedule was therefore constructed to be followed. All sampling was then performed at both loads and the efficiency calculations could begin. The results indicate a high total efficiency with somewhat lower boiler efficiency. The boiler efficiency varied depending on the load by 74% on high load and 72% on low load. The total efficiency was 92% on high load and 91% on low load. The greatest losses were all connected to flue gas losses. Losses like moisture in flue gas or hot dry flue gas. The flue gas losses varied between 24% to 26% for the boiler efficiency and 6.6% to 7.2% for the total efficiency on high and low loads. Besides flue gas losses the next greatest loss is radiation losses, about 0.7% for both high and low loads. Losses due to incomplete combustion were very low and varied between 0.52% and 0.53% for high and low load which in combination with the low ash loses (0.006%-0.04%) indicates very good combustion. Due to the relatively high efficiencies, no obvious solutions for decreased energy losses were found. The greatest energy losses are flue gas losses and a solution to this will influence the efficiency the most. One solution to increase the efficiency is to reduce the moisture content of the flue gas. At this time the moisture content is at 9% and contributes the most to the flue gas losses. Reducing the moisture content can be done by lowering the flue gas temperature. This will increase the amount of moisture that is condensed in the flue gas condenser. To achieve this, the flue gas condensate temperature needs to be decreased. This can be done by either lowering the temperature on the district heating return which is cooling the flue gas condensate or install a heat pump between the flue gas condensate and the district heating return. These solutions require a more in depth analysis to evaluate if this is technically possible and if it is economically viable.

The effect of exercise (EXR) on food intake (FI), subjective appetite and net energy balance was investigated in normal weight (NW), overweight (OW) and obese (OB) boys. Each boy received in random order either a non-caloric sweetened control (CON) or glucose (GLU) drink after either EXR or sedentary activity. Normal weight and OW/OB boys exercised at their ventilation threshold (VeT) in experiment 1 and NW boys exercised at 25% above their VeT in experiment 2. Overweight/OB boys ate significantly more total food than NW boys but not when adjusted for body weight. Food intake was lower after the GLU drink. Although EXR increased average appetite it did not affect FI. However, net energy balance was reduced by EXR in OW/OB boys, but not in NW boys. Thus, while EXR increases subjective appetite, apparent intake compensation occurred only in NW, but not in OW/OB boys, resulting in reduced net energy balance in OW/OB boys.

The effect of exercise (EXR) on food intake (FI), subjective appetite and net energy balance was investigated in normal weight (NW), overweight (OW) and obese (OB) boys. Each boy received in random order either a non-caloric sweetened control (CON) or glucose (GLU) drink after either EXR or sedentary activity. Normal weight and OW/OB boys exercised at their ventilation threshold (VeT) in experiment 1 and NW boys exercised at 25% above their VeT in experiment 2. Overweight/OB boys ate significantly more total food than NW boys but not when adjusted for body weight. Food intake was lower after the GLU drink. Although EXR increased average appetite it did not affect FI. However, net energy balance was reduced by EXR in OW/OB boys, but not in NW boys. Thus, while EXR increases subjective appetite, apparent intake compensation occurred only in NW, but not in OW/OB boys, resulting in reduced net energy balance in OW/OB boys.

The relationship between substrate oxidation (RER) and food intake (FI) is undefined. This study examined the effects of RER modified by a glucose pre-load (GL), exercise (EX) and GL with EX on, FI and energy balance (NEB) in normal-weight boys (9-12 y) and men (20-30 y). Subjects (15 boys, 15 men) were randomized with treatments of either water or GL followed by either EX or rest. Measures included RER, energy expenditure (EE)(kcal/kg), subjective appetite, FI(kcal/kg) measured at a pizza lunch and NEB (kcal/kg). FI(kcal/kg) was reduced by GL(p < 0.0001), and further decreased with GL ingested prior to EX(p = 0.0254). RER was increased with GL(p < 0.0001) and EX(p = 0.0043), and was higher in men compared to boys (p = 0.007). There was no association between RER and FI(kcal/kg). In conclusion, there was no relationship between RER and FI, suggesting that FI is not affected by substrate oxidation.

The relationship between substrate oxidation (RER) and food intake (FI) is undefined. This study examined the effects of RER modified by a glucose pre-load (GL), exercise (EX) and GL with EX on, FI and energy balance (NEB) in normal-weight boys (9-12 y) and men (20-30 y). Subjects (15 boys, 15 men) were randomized with treatments of either water or GL followed by either EX or rest. Measures included RER, energy expenditure (EE)(kcal/kg), subjective appetite, FI(kcal/kg) measured at a pizza lunch and NEB (kcal/kg). FI(kcal/kg) was reduced by GL(p < 0.0001), and further decreased with GL ingested prior to EX(p = 0.0254). RER was increased with GL(p < 0.0001) and EX(p = 0.0043), and was higher in men compared to boys (p = 0.007). There was no association between RER and FI(kcal/kg). In conclusion, there was no relationship between RER and FI, suggesting that FI is not affected by substrate oxidation.