Ulrike Jordan

INFLUENCE OF THE DHW-LOAD PROFILE ON THE FRACTIONAL ENERGY SAVINGS: A CASE STUDY OF A SOLAR COMBI-SYSTEM WITH TRNSYS SIMULATIONS

Abstract In this paper the influence of domestic hot water (DHW) load profiles with a constant total yearly heat demand is studied for a solar combisystem. Whereas so far simulation studies are usually done with a simplified DHW load profile (e.g. according to prEN 12977), a more realistic profile was generated on a 1-min time scale with statistical means. Assumptions about the distribution of the DHW consumption during the year, depending also on the weekday, and the time of the day were made. To study the influence of the draw-off duration and flow rate as well as the daytime of DHW consumption, TRNSYS simulations were carried out with a variety of simplified and fairly realistic load profiles. In this case study the investigated solar system consists of a storage tank with an internal thermosyphonally driven discharge unit. Despite a rather minor influence of the draw-off flow rate on the fractional energy savings for the given system applying simplified profiles: a fairly wide range of more than 2 percentage points of the fractional energy savings was found for the system with some constructive improvements or for applying more realistic DHW-profiles. It can be concluded that the influence of the DHW-load profile may not be disregarded, when combistores are compared. This is true especially for stores, for which duration and flow rate of a DHW draw-off have a severe influence on the temperature stratification in the storage tank.

Investigations of a Dehumidifier in a Solar Assisted Liquid Desiccant Demonstration Plant

A solar-assisted liquid desiccant demonstration plant was built and experimentally evaluated. Humidity of the air, density of the desiccant, and all relevant mass flow rates and temperatures were measured at each inlet and outlet position. Adiabatic dehumidification experiments were performed in different seasons of the year under various ambient air conditions. The moisture removal rate _ mv, the mass balance factor jm, and the absorber effectiveness, eabs, were evaluated. An aqueous solution of LiCl was used as liquid desiccant with an initial mass fraction of about 0.4 kgLiCl/kgsol. The mass flow rate of the air through the absorber was about 1100 kg/h. The experimental results showed a reduction in the air humidity ratio in the range of 1.3–4.3 g/kg accompanied with an increase in the air temperature in the range of 3–8.5 K, depending on the inlet and operating conditions. For the air to desiccant mass flow ratio of 82, a mass fraction spread of 5.7% points in the desiccant and a volumetric energy storage capacity of 430 MJ/m were achieved. By operating the desiccant pump in an intermittent mode, a mass fraction spread of about 13% points in the desiccant and an energy storage capacity of about 900 MJ/m were reached. In addition, the experimental results were compared with results from a numerical model. The numerical model overestimates the heat and mass transfer because it assumes ideal surface wetting and uniform distribution of the circulated fluids. [DOI: 10.1115/1.4040841]

Experimental Analysis of a Liquid Desiccant Cross Flow Plate-Type Dehumidifier for Air-Conditioning Applications

The mass transfer is driven by the difference between the partial pressure of water vapor in the air stream and the vapor pressure associated with the desiccant solution. The vapor pressure above the solution decreases with increasing solution concentration and increases with increasing solution temperature. Therefore, cold and highly concentrated solution provides the best dehumidification while warm and dilute solution provides the best humidification.

Sustainable Beer Production by Combining Solar Process Heat and Energy Efficiency - Holistic System Concept and Preliminary Operational Experiences

Recent research projects in the field of solar process heat have shown that, besides the ambitious economic targets, the integration of solar heating systems in industrial processes is a main barrier for the widespread of this technology. Therefore, a sufficiently deep understanding of industrial processes is necessary, which currently does not exist among solar engineers. In a current research project, Kassel University developed a concept for solar process heat generation in a brewery that combines energy efficiency measures and the application of solar thermal energy. This paper gives an overview of the developed concept including the applied approach and will present experiences of planning and installation of the solar heating system. Furthermore, first operational results are presented.

Simulation Based Optimization of a Solar Water Heating System by a Hybrid Genetic – Binary Search Algorithm

A proper design of a large solar heating system is important to maximize the benefit of the system. The system hydraulics, control parameters and dimensions of single components are usually tried to be optimized towards achieving better system performance at lower costs. The complexity of the target functions, a large number of optimization parameters and boundary conditions imposed on the system require application of advanced numerical optimization techniques and tools as well as additional software.

Technical Potential of Solar Thermal Driven Open Cycle Absorption Processes for Industrial and Comfort Air Conditioning

The open absorption process is basically an air drying process. Applications for this process can be found in the sector of industrial and comfort air conditioning. In this investigation seven categories of applications are described and characterized concerning their specific requests for temperature and humidity.

Solare Heizungsunterstützung ‐ auch für Bestandsgebäude

Thermische Solaranlagen sind inzwischen ein selbstverstandlicher Bestandteil der Haustechnik vieler Neubauten. Entsprechend sind in Deutschland bis Ende 2001 knapp vier Millionen Quadratmeter Solarkollektoren installiert worden, und zwar bei einer Zubaurate von zuletzt fast 1 Mio. m� pro Jahr. Die folgenden Ausfuhrungen diskutieren die wesentlichen technischen Voraussetzungen fur die Installation von Standardsolaranlagen, wie z. B. geeignete Zusatzenergietrager oder den Platzbedarf. Allgemein ist bei der Integration von Solaranlagen in bestehende Haustechniksysteme ganz besonders auf eine exakte Planung und eine gute Abstimmung der Komponenten zu achten.