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After his final secondary-school examinations at the Städtisches Stiftsgymnasium Xanten and the following civilian service, Jochen Döll began his studies of Environmental Science and Renewable Energies at the FHTW-Berlin (university of applied science). Before and during his studies he was able to extend his theoretical knowledge gathered at the FHTW by practical skills in various internships. While doing his 6 month work placement in Costa Rica the combined of scientific knowledge and practical skills proofed to be very useful in the development of a novel thermosiphon solar water heater.
Back in Germany he prepared his diploma thesis at the Fraunhofer Institute for Solar Energy Systems (ISE), Freiburg in the field of solar cooling technologies. Having a strong interest in this scientific area, he is today still working in several international projects (MEDISCO, HIGH-COMBI, SOLERA).
In his doctoral dissertation he will focus on problems concerning the thermodynamic evaluation and optimization of solar cooling applications.
„Thermodynamic evaluation of closed cycle, solar-thermally powered cooling systems with regard to primary energy aspects"
The growing scarcity of (energetic) resources accompanied with a simultaneous increase of demand represents a major challenge for the society today. This challenge can only be mastered if we change the ways we produce and use energy. One field of energy usage which has shown a big increase over the last years is the cooling and air-conditioning of buildings. Driven by higher demand for comfort, increasing ambient temperatures but also by the augmented usage of glass in architecture,this demand is expected to rise over the upcoming decades.
While covering this demand by conventional electrically driven compression chillers, a large amount of CO2 is emitted, and the electricity is further often drawn from the net during critical peak hours (cf. blackout in California 2001). Solar-thermally driven cooling systems can be an alternative to cover the growing demand without the above mentioned drawbacks. Especially due to the typically strong congruence of cold demand and supply of solar radiation, these systems represent a chance to supply sustainable air conditioning to dwellings. A further application can be process cold for industrial applications.
Up to now, there has been no agreement on a unified evaluation procedure to assess the thermodynamic characteristics of closed cycle solar cooling systems. Aim of this PhD project is to elaborate such a procedure in order to ease the dissemination of this energy resource saving and efficient way of cooling and air conditioning.
Thermally driven heat transformation systems are in the focus of this work. Among these, the focus is on solar thermally driven, closed-cycle systems like ab- and adsorption-systems. These systems are characterized by the low electricity consumption compared to conventional compression cooling systems. Additionally, they give the opportunity of storing the operating power – heat – in an appropriate storage. On the other hand, these systems show larger complexity when it comes to system layout, operation, evaluation and optimization. Unlike in electrically driven systems, thermal processes have to be examined and evaluated. In these, not only the energy demand, but also the needed or delivered temperature levels play a major role. The evaluation procedure to be developed should give the chance to analyze the thermodynamic path from radiation to "useful cold". Insight into the reasonable application of which heat transformation system on which site can cover which load are expected. Also energy management issues and primary energy aspects will be elaborated.
The evaluation procedures are to be implemented with respect to measured data collected in various ongoing projects in order to assess the decisions made for the systems and to reveal the potential for optimization.