MILP Model for Energy Supply Design to overcome the Cannibalization of Solar Thermal Plants and large-scale Heat Pumps in Urban District Heating Systems

Urban infrastructure is accountable for a large share of carbon emissions, especially energy supply to meet the demand for thermal heat and domestic water. Regarding the climate agreements these systems have to be decarbonized. In urban neighbourhoods, district heating systems (DHS) are efficient solutions to supply heat and favoured by locally or regionally operating municipal utilities. To integrate renewable heat from solar thermal plants or waste heat from lakes or rivers by using heat pumps, DHS in highly densed agglomerations face major problems. On the one hand the availability of land respectively free space is limited. On the other hand operating times of solar thermal plants and large-scale heat pumps are similar considering a long-term planning horizon. In this contribution a mixed integer linear programming (MILP) model is developed todetermine the implementation of both options solar thermal plants as well as large-scale heat pumps in DHS with adjustable generation plants in an optimal way. The model computes minimal investment costs and related emission savings for different alternatives integrating heat of renewable sources. The results can support the decision-making regarding the feasibility. Furthermore, good combinations of different renewable energy sources and their integration into a DHS can be identified even though the sources are distributed over the DHS. Main decision variables are the choice of possible plant sizes under consideration of the (existing) DHS-network layout and available space in highly densed urban districts. The networktopology as well as energetic and ecological constraints (e.g. maximum flow capacity in pipes or operating times of heat pumps due to boundary conditions of heat sources) lead to a selection of plant combinations which represent the optimal solution to lower the emissions at acceptable investment costs. The developed model is applied to a case study for an DHS in a newly built neighbourhood with several available heatsources for heat pumps and free areas for solar thermal collectors. The results proof the function of the model and illustrate that an energetic improvement of the DHS is possible by integrating solar thermal plants and large-scale heat pumps at economically acceptable conditions

Key role for transforming growth factor-β in melanocyte stem cell immaturity and quiescence

Division of Stem Cell Medicin

Experimentelle Untersuchungen zur Graphitkorrosion und Aerosolentstehung beim Lufteinbruch in das Core eines Kugelhaufen-Hochtemperaturreaktors

A High Temperature Reactor can be designed to remove the decay heat without usingany active systems. For most accident scenarios a release of radioactive fission productscan be excluded by design. However, during operation of a HTR some accidents areprincipally possible, which can result in a release of fission products out of the fuelelements and of the reactor system. One of these accidents is a hypothetical massive airingress into the hot graphite reactor core. After a pressure drop caused by leakages inthe primary circuit a gas mass flow may be able to stream through the core according tofree natural convection leading to a corrosion of the graphite fuel elements and reflector structures

Power Management Optimization of an Experimental Fuel Cell/Battery/Supercapacitor Hybrid System

In this paper, an experimental fuel cell/battery/supercapacitor hybrid system is investigated in terms of modeling and power management design and optimization. The power management strategy is designed based on the role that should be played by each component of the hybrid power source. The supercapacitor is responsible for the peak power demands. The battery assists the supercapacitor in fulfilling the transient power demand by controlling its state-of-energy, whereas the fuel cell system, with its slow dynamics, controls the state-of-charge of the battery. The parameters of the power management strategy are optimized by a genetic algorithm and Pareto front analysis in a framework of multi-objective optimization, taking into account the hydrogen consumption, the battery loading and the acceleration performance. The optimization results are validated on a test bench composed of a fuel cell system (1.2 kW, 26 V), lithium polymer battery (30 Ah, 37 V), and a supercapacitor (167 F, 48 V)

Enhancer-deleted retroviral vectors restore high levels of superoxide generation in a mouse model of CGD

BACKGROUND: Retroviral vectors possess many advantages for use in gene therapy protocols, especially within the haematopoietic system. A number of attendant problems, however, still limit their safety in clinical application. The effects of the enhancer present in the retroviral long terminal repeat (LTR) are a major concern for the clinical usage of such vectors, as they can exert a powerful regulatory influence on the genes that surround them. METHODS: To improve the safety and widen the applicability of retroviral vectors for use in gene therapy we have developed an enhancer-deleted (Delta-LTR) retroviral vector that retained high titre and demonstrated transcriptional activity in myeloid cells. RESULTS: When used to correct a mouse model of autosomal recessive chronic granulomatous disease, the Delta-LTR vectors gave acceptable levels of gene transfer to mouse bone marrow cells. Evidence for a slight preferential expression in myeloid cells was obtained with all the vectors studied. Nitroblue tetrazolium assay of superoxide generation in mouse bone marrow derived haematopoietic colonies revealed that transduction with Delta-LTR vectors could restore functional NADPH oxidase to cells from these animals. Superoxide assay of peripheral blood confirmed that, although relatively low numbers of cells were transduced, the Delta-LTR vector was capable of reconstituting very high levels of oxidase activity, comparable to that obtained from normal cells. CONCLUSIONS: The Delta-LTR vector described here could provide the basis for a new generation of retroviral vectors with improved safety