Simulations of Combined Solar Thermal and Heat Pump Systems for Domestic Hot Water and Space Heating

AbstractThe system combination of solar thermal collectors and heat pumps is a very attractive option for increasing the renewable energy usage at worldwide level for heating and domestic hot water preparation. In this work parallel and series combined solar and heat pump systems are analyzed within the IEA SHC Task44/HPP Annex38 reference conditions for different buildings and a typical Central European climate. Three combined systems have been studied in detail: solar and air source heat pump, solar and ground source heat pump, and exclusively solar source heat pump in combination with an ice storage. Numerical calculations have been performed using two simulation platforms: TRNSYS-17 and Polysun-6®. Comparisons between the two simulation environments have been also provided. Moreover, a reference case without solar has been used to determine the potential efficiency benefits of using solar collectors compared to a system with a heat pump alone in the specified climate and for covering the specified heat load. Simulations presented in this work show that differences in system performance up to 4% can be expected between TRNSYS-17 and Polysun-6® for air source based systems, and higher discrepancies, up to 14% are obtained for ground source based systems. Comparisons between combined solar thermal and heat pump systems with their respective “heat pump only” reference solutions show that the absolute electricity savings of air source are usually higher compared to ground source based systems. Systems using large ice storages are able to reach seasonal performance factors in the range of 5, which is of the order of performance of combined solar and ground source heat pump systems

Extensive geothermal heat use in cities energetic and economic comparison of options for thermal regeneration of the ground

Geothermal energy as a heat source for heat pumps is increasingly unused in the city of Zürich. However, as indicated by other authors, the renewable potential for shallow geothermal heat use is limited due to the fact that natural regeneration in the absence of ground water flow is slow. Constant heat extractions from dense geothermal heat pump installations continuously cool down the affected ground layer.. In this case boreholes have to be drilled deeper or regenerated in order to avoid freezing around the borehole. The aim of this simulation study is to find the most economic geothermal heat pump concept, which does not lead to borehole freezing after 50 years of operation in areas with dense installations (an exemplary mean geothermal heat extraction of 35kWh/m2/a was supposed for this this study). Therefor a multi-family house with a standard ground source heat pump was simulated for a period of 50 years in Polysun. Various solar concepts, an air heat exchanger concept, a geo cooling concept and also a system without regeneration were added to the system. These concepts were compared under the assumption that all neighboring installations are using an equivalent regeneration strategy as the simulated system For the different system concepts, highly variable total borehole length were needed to avoid freezing, reaching from 1020m for a system with a large glazed collector field to 2160m for the un-regenerated case. The heat cost of the analyzed system concepts was in the range of 21- 27 Rp/kWh. The most cost-effective system concepts according to this analysis are the air heat exchanger or unglazed collectors. Increasing the total borehole meters was not only one of the most expensive options, but also the least sustainable, since the continuation of ground tem-perature decrease after 50 years was more pronounced with this option than for any other option

SOLAR & PELLET HEATING: SPECIFICATIONS FOR HIGH EFFICIENCY SYSTEM DESIGN

Abstract Combined biomass and solar heating systems provide the opportunity for a heat supply of single family houses without the use of fossil energy. Pellet fired boilers play a predominant role within these systems because their standardised combustible allows for the fully automated operation. However, the combination of biomass boilers and solar collectors places special requirements in view of a good system solution. To analyse the proper combination of both technologies three separate projects were carried out at SPF. the main instrument thereby was the Concise Cycle Test method supplemented by preliminary tests of the boiler and subsequent simulations. It was shown that a modulating boiler operation is superior in terms of both, high energetic efficiency and low emissions compared to intermitting boiler operation. But this is only the case if the following requirements are met: Low excess-air factors for the complete modulation range, low envelope losses, a fast adaption of the output power, correct dimensioning of the boiler. Beside the characteristics of the boiler the hydraulic connection and the control is important to reach a good system performance. Mostly for combined biomass and solar heating systems the best solution is a connection of the boiler to the thermal energy store instead of a direct connection to the heating circuit. The requirements that have to be fulfilled for the control of TES charging are: Temperature sensors within the store to control the boiler dependent to the demand for space heating or domestic hot water. In order to control the power modulation of the boiler, the best option is to reduce the volume flow rate of the boiler pump based on an algorithm that takes into account the temperature measured in the TES. Other options are to increase the return temperature of the boiler using a motorized mixing valve, or to reduce the set-temperature for the water leaving the boiler

HIV-1 Nef Employs Two Distinct Mechanisms to Modulate Lck Subcellular Localization and TCR Induced Actin Remodeling

The Nef protein acts as critical factor during HIV pathogenesis by increasing HIV replication in vivo via the modulation of host cell vesicle transport and signal transduction processes. Recent studies suggested that Nef alters formation and function of immunological synapses (IS), thereby modulating exogenous T-cell receptor (TCR) stimulation to balance between partial T cell activation required for HIV-1 spread and prevention of activation induced cell death. Alterations of IS function by Nef include interference with cell spreading and actin polymerization upon TCR engagement, a pronounced intracellular accumulation of the Src kinase Lck and its reduced IS recruitment. Here we use a combination of Nef mutagenesis and pharmacological inhibition to analyze the relative contribution of these effects to Nef mediated alterations of IS organization and function on TCR stimulatory surfaces. Inhibition of actin polymerization and IS recruitment of Lck were governed by identical Nef determinants and correlated well with Nef's association with Pak2 kinase activity. In contrast, Nef mediated Lck endosomal accumulation was separable from these effects, occurred independently of Pak2, required integrity of the microtubule rather than the actin filament system and thus represents a distinct Nef activity. Finally, reduction of TCR signal transmission by Nef was linked to altered actin remodeling and Lck IS recruitment but did not require endosomal Lck rerouting. Thus, Nef affects IS function via multiple independent mechanisms to optimize virus replication in the infected host

Trajectories of Early Adolescent Loneliness: Implications for Physical Health and Sleep

The current study examines the relationship between prolonged loneliness, physical health, and sleep among young adolescents (10–13 years; N = 1214; 53% girls). Loneliness was measured at 10, 12 and 13 years of age along with parent-reported health and sleep outcomes. Using growth mixture modelling, 6 distinct trajectories were identified: ‘low increasing to high loneliness’ (n = 23, 2%), ‘high reducing loneliness’ (n = 28, 3%), ‘medium stable loneliness’ (n = 60, 5%), ‘medium reducing loneliness’ (n = 185, 15%), ‘low increasing to medium loneliness’ (n = 165, 14%), and ‘low stable loneliness’ (n = 743, 61%). Further analyses found non-significant differences between the loneliness trajectories and parent-report health and sleep outcomes including visits to health professionals, perceived general health, and sleep quality. The current study offers an important contribution to the literature on loneliness and health. Results show that the relationship may not be evident in early adolescence when parent reports of children’s health are used. The current study highlights the importance of informant choice when reporting health. The implications of the findings for future empirical work are discussed

A Nuclear Localization of the Infectious Haematopoietic Necrosis Virus NV Protein Is Necessary for Optimal Viral Growth

The nonvirion (NV) protein of infectious hematopoietic necrosis virus (IHNV) has been previously reported to be essential for efficient growth and pathogenicity of IHNV. However, little is known about the mechanism by which the NV supports the viral growth. In this study, cellular localization of NV and its role in IHNV growth in host cells was investigated. Through transient transfection in RTG-2 cells of NV fused to green fluorescent protein (GFP), a nuclear localization of NV was demonstrated. Deletion analyses showed that the 32EGDL35 residues were essential for nuclear localization of NV protein, and fusion of these 4 amino acids to GFP directed its transport to the nucleus. We generated a recombinant IHNV, rIHNV-NV-ΔEGDL in which the 32EGDL35 was deleted from the NV. rIHNVs with wild-type NV (rIHNV-NV) or with the NV gene replaced with GFP (rIHNV-ΔNV-GFP) were used as controls. RTG-2 cells infected with rIHNV-ΔNV-GFP and rIHNV-NV-ΔEGDL yielded 12- and 5-fold less infectious virion, respectively, than wild type rIHNV-infected cells at 48 h post-infection (p.i.). While treatment with poly I∶C at 24 h p.i. did not inhibit replication of wild-type rIHNVs, replication rates of rIHNV-ΔNV-GFP and rIHNV-NV-ΔEGDL were inhibited by poly I∶C. In addition, both rIHNV-ΔNV and rIHNV-NV-ΔEGDL induced higher levels of expressions of both IFN1 and Mx1 than wild-type rIHNV. These data suggest that the IHNV NV may support the growth of IHNV through inhibition of the INF system and the amino acid residues of 32EGDL35 responsible for nuclear localization are important for the inhibitory activity of NV

Review on computational methods for Lyapunov functions

Lyapunov functions are an essential tool in the stability analysis of dynamical systems, both in theory and applications. They provide sufficient conditions for the stability of equilibria or more general invariant sets, as well as for their basin of attraction. The necessity, i.e. the existence of Lyapunov functions, has been studied in converse theorems, however, they do not provide a general method to compute them. Because of their importance in stability analysis, numerous computational construction methods have been developed within the Engineering, Informatics, and Mathematics community. They cover different types of systems such as ordinary differential equations, switched systems, non-smooth systems, discrete-time systems etc., and employ di_erent methods such as series expansion, linear programming, linear matrix inequalities, collocation methods, algebraic methods, set-theoretic methods, and many others. This review brings these different methods together. First, the different types of systems, where Lyapunov functions are used, are briefly discussed. In the main part, the computational methods are presented, ordered by the type of method used to construct a Lyapunov function

CMS physics technical design report : Addendum on high density QCD with heavy ions

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