Results 1 - 10 of 65
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[en] In Britain, residential properties are predominantly heated using gas central heating systems. Ensuring a reliable supply of gas is therefore vital in protecting vulnerable sections of society from the adverse effects of cold weather. Ahead of the winter, the grid operator makes a prediction of gas demand to better anticipate possible conditions. Seasonal weather forecasts are not currently used to inform this demand prediction. Here we assess whether seasonal weather forecasts can skilfully predict the weather-driven component of both winter mean gas demand and the number of extreme gas demand days over the winter period. We find that both the mean and the number of extreme days are predicted with some skill from early November using seasonal forecasts of the large-scale atmospheric circulation (r > 0.5). Although temperature is most strongly correlated with gas demand, the more skilful prediction of the atmospheric circulation means it is a better predictor of demand. If seasonal weather forecasts are incorporated into pre-winter gas demand planning, they could help improve the security of gas supplies and reduce the impacts associated with extreme demand events. (letter)
[en] In the present work, we consider the use of thermal stores in spacecraft heating systems. The advantages and disadvantages of various approaches to heat storage are compared. The use of heat stores with a melting working material is most promising and practicable at present.
[en] The propagation characteristics and physical nature of low-frequency waves observed in the ionosphere during heating of the near-Earth plasma by a powerful short-wavelength radiation are investigated using the singular value decomposition method. The experimental results obtained with the Sura midlatitude heating facility and detected by the onboard equipment of the DEMETER satellite were used. The ion composition of the near-Earth plasma is estimated from the spectral characteristics of the observed radio waves. The method is verified using results of full-scale measurements performed at altitudes corresponding to the Earth’s outer ionosphere.
[en] China has become the world’s largest carbon emitter since 2007; thus, reducing future emission has become an arduous task. Calculating energy efficiency fairly is paramount for formulating energy policies, given the different development levels of provinces. This study employed a three-stage data envelopment analysis model that considered environmental constraints to evaluate the energy efficiency of China’s 30 provinces in 2015 and redefined traditional energy efficiency as energy environment efficiency which calculated under environmental constraints. Different factors, such as urban development level and industrial structure in relation to energy environment efficiency, were analyzed. Three main results were obtained. First, the average energy environment efficiency in 2015 was only 0.73, which showed that China has roughly 30% capacity for improvement in the future. Second, stochastic frontier analysis demonstrated that the industrial structure, energy consumption structure, and central heating systems exerted negative impacts, and the level of city design and the degree of openness exerted positive effects on energy environment efficiency. Third, capital, manpower, and the extent of industrial concentration in central and western regions should be increased to improve China’s energy environment efficiency.
[en] An upgraded infrared imaging system has been installed at the stellarator TJ-II as a diagnostic tool of the Neutral Beam Injection heating. Thermographic analysis of the beam-wall interaction areas can be used to estimate the beam power lost through reionization and shine-through mechanisms in Neutral Beam heated plasmas. Three different Regions of Interest inside TJ-II vacuum vessel have been determined whose thermographic analysis will be applied to the study of beam related processes. The optical conditions required for each application have been used to define the specifications of the IR camera. Optimization of the optical design has been carried out by means of the optical simulation code ZEMAX. The IR window size has been increased to maximize the fraction of the field of view that is free from vignetting. The system has been fully commissioned and is now operative, routinely providing thermographic data of the regions of interest during the last TJ-II experimental campaign. The IR diagnostic is described in detail and its applicability to study beam power deposition on different targets is discussed.
[en] In this work, calcium chloride hexahydrate (CaCl2 · 6H2O) was adopted as phase change material (PCM), and the supercooling degree of CaCl2 · 6H2O can be reduced to 0.3 °C by adding 5 wt% sodium metasilicate nonahydrate (Na2SiO3 · 9H2O). Then the composite material of ‘CaCl2 · 6H2O/5 wt% Na2SiO3 · 9H2O’ was added into the floor heating system as the phase change layer to analyze and compare its controlling effect for the indoor temperature under summer and winter conditions. The results showed that the cooling rate of the floor heating system with the phase change layer is lower about 78.7% than that of floor heating system without the phase change layer; the heating rate of the floor heating system with the phase change layer is lower about 70.1% than that of floor heating system without the phase change layer. This result showed that the ‘CaCl2 · 6H2O/5 wt% Na2SiO3 · 9H2O’ composite PCM has a good application prospect in the field of building energy efficiency. (paper)
[en] This paper reports on the development of an integrated leaf quality inspecting system using near infrared reflectance (NIR) spectroscopy for quick and in situ estimation of total polyphenol (TP) content of fresh tea leaves, which is the most important quality indicator of tea. The integrated system consists of a heating system to dry the fresh tea leaves to the level of 3–4% moisture, a grinding and sieving system fitted with a 250 micron mesh sieve to make fine powder from the dried leaf. Samples thus prepared are transferred to the NIR beam and TP is measured instantaneously. The wavelength region, the number of partial least squares (PLS) component and the choice of preprocessing methods are optimized simultaneously by leave-one-sample out cross-validation during the model calibration. In order to measure polyphenol percentage in situ, the regression model is developed using PLS regression algorithm on NIR spectra of fifty-five samples. The efficacy of the model developed is evaluated by the root mean square error of cross-validation, root mean square error of prediction and correlation coefficient (R2) which are obtained as 0.1722, 0.5162 and 0.95, respectively.
[en] In this study, a corrosion failure analysis of a heat transport pipe was conducted, as the result of a pinhole leak. Interestingly, the corrosion damage occurred externally in the pipeline, resulting in severe thickness reduction near the seam line. Also, while a stable magnetite protective film formed on the inner surface, the manganese oxide formation occurred only on the outer surface. The interior and exterior of the pipe were composed of ferrite and pearlite. The large manganese sulfide and alumina inclusions were found near the seam line. In addition, the manganese sulfide inclusions resulted in grooving corrosion, which progressed in the seam line leading to the reduction in the thickness, followed by the exposure of the alumina in the matrix to the outer surface. To note, the corrosion was accelerated by pits generated from the boundaries separating the inclusions from the matrix, which resulted in pinhole leaks and water loss
[en] Highlights: • Biofuels for heating and cooking is the main cause of indoor pollution in developing countries. • In Peru the FISE program subsidizes the substitution of traditional cookstoves by gas cookstoves. • The program has not achieved the total replacement of traditional cookstoves. • We don’t find a direct relation between the use of LPG stoves and health outcomes. • Clean cookstoves should be complemented with improved heating systems and electricity subsidies. - Abstract: The use of biofuels for heating and cooking is the main cause of indoor air pollution in developing countries, and one of the main causes of acute respiratory infections. To tackle this problem, in 2012, the Peruvian Government created the FISE program, which subsidizes the replacement of traditional stoves with gas cookstoves. This paper describes the challenges faced during the implementation of the FISE, such as the selection of beneficiaries and the creation of a national network of suppliers for the delivery of liquefied petroleum gas (LPG) cylinders. Using a dataset with information collected from five districts in the department of Ayacucho in 2015, we apply propensity score matching at the household level to evaluate the effects of the program. We show that the FISE favored the adoption of the LPG cookstoves, but that many households still combine their use with traditional cookstoves. We find no evidence that the use of LPG stoves has reduced respiratory problems in the beneficiary households; however, the program has been found to increase the use of LPG stoves for boiling water, which may reduce the exposition of child in beneficiary households to water-related diseases.
[en] Wendelstein 7-X (W7-X) is a steady state capable optimised stellarator. The main heating system is electron cyclotron resonance heating (ECRH) operating at 140 GHz providing up to 9 MW microwave power. The power is launched into the machine by front steerable quasi-optical launchers in X- or O-mode. While in X-mode the first pass absorption is 99%, it is only 40... 70% in O-mode. O2-mode heating is forseen for high density operation above the X2 cutoff density of m−3. A set of diagnostics has been developed to protect the machine from non absorbed ECRH power which can easily damage in vessel components. The non absorbed power hitting the inner wall is measured by waveguides embedded in the first wall (ECA diagnostic). In order to prevent the inner wall from overheating or arcing, a near-infra red sensitive video diagnostic with a dynamic range of 450...1200 °C was integrated in the ECRH launchers. Thermal calculations for the carbon tiles predict a temperature increase above the detection threshold for scenarios of plasma start-up failure or poor absorption on a time scale of 50 ms. However, the temperature increase measured by an IR camera in experiments with failed break down, i.e. no ECRH absorption for up to 50 ms, was only C. In discharges with 5% transmission the measured temperature increase was comparable. The stray radiation level inside the machine is measured by so called sniffer probes resembling microwave diode detectors which were designed to collect all radiation approaching the probing surface independent of incident angle and polarization. Five sniffer probes are installed at different toroidal positions. They were integrated in the ECRH interlock system. During the first operational phase of W7-X this was the only available plasma interlock system. The signal quality proofed to be high enough for a reliable termination in case of poor absorption. After a breakdown phase of 10 ms, the sniffer probe signals dropped by more than an order of magnitude. Especially in the very first days of operation, most discharges died by a radiative collapse due to impurity influx. In this case the heating power was reliably switched off due to the increased level of stray radiation. Moreover, ECRH bolometers with a slower response time in the launcher ports and an empty diagnostic port were used to estimate the stray radiation level in the ports. In the launcher ports it could be shown that the stray radiation could lead to an overheating of the bellows in long discharges. Possible counter measures are discussed. (paper)