EUROTHERM Seminar Nr. 98
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List of Confirmed Invited Speakers

Pr. Stephan KABELAC (LEIBNIZ UNIVERSITÄT, Hannover, Germany)

 

Title: Thermodynamics of Solar Radiation


Abstract: Solar radiation consists of electromagnetic waves which carry energy and entropy. As the solar radiation is free of costs, it is an ideal source of primary energy for mankind which should and will be used increasingly. The entropy content of solar radiation reaching the ground varies, depending on its interaction with the atmosphere. When analyzing the conversion from incoming solar energy to useful energy forms like electric energy or mechanical energy, this entropy content plays a dominant role. A ray of coherent monochromatic radiation, laser radiation, is free of entropy. On the other side there is the black body thermal radiation, which has the same entropy content as a heat flux of the same temperature. A thermodynamic analysis of solar energy conversion devices must take into account the incoming and the outgoing energy and entropy fluxes. Such an analysis gives the maximum energy conversion efficiency for a given incoming solar radiation flux and is thus the basis for evaluating real conversion devices. Due to the entropy content of solar radiation not all of the incoming radiation energy may be converted to entropy free mechanical or electric energy. The maximum conversion efficiency of a photovoltaic cell, for example, is not 100 % but something around 70 % of the incoming global radiation flux, depending on the atmospheric conditions. The presentation will review the radiation entropy calculation procedure, it will discuss the impact of an entropy content on solar radiation energy conversion and it will give some examples on the calculation for concentrated solar radiation.

 


Dr. Manuel ROMERO (IMEDEA ENERGY, Mostoles, Spain)


Title: Solar Thermal Power Plants, Developing technologies for dispatchable solar electricity


Abstract: The first generation of commercial solar thermal power plants is mainly based on technological developments and concepts that matured in the 80’s and 90’s. They are projects still based on conservative schemes and technologies which do not exploit the enormous potential of concentrated solar energy. Commercial projects use technologies operating with thermal fluids at relatively modest temperatures, below 400ºC. The most immediate consequences of these conservative designs are the use of systems with efficiencies below 20% nominal in the conversion of direct solar radiation to electricity; the tight limitation in the use of efficient energy storage systems; the high water consumption and land extension due to the inefficiency of the integration with the power block; the lack of rational schemes for their integration in distributed generation architectures and the limitation to reach the temperatures needed for the thermochemical routes used to produce solar fuels. R&D programmes are accelerating the development of new thermal fluids for operation at higher temperatures; new thermal (sensible heat and phase change) and thermochemical energy storage systems; solar receivers with volumetric absorbers or clouds of particles for higher apparent absorptivity and development of dry-cooling at power block for avoiding water consumption. Main priorities for this technology are to speed up the cost reduction curve with more disruptive designs and the increment of dispatchability issues.

 


Dr. Robert PITZ-PAAL (DLR, Cologne, Germany)


Title: Optical and thermal performance of parabolic trough collectors


Abstract: The performance of parabolic trough collectors is affected by the interaction between three major components: the reflector, the receiver and the steel support structure. Typically all elements are provided by different manufactures and are assembled on site. While it is relatively straight forward to evaluate the overall performance or the assembled collector by thermal measurements, other measurements approaches are required to understand the contribution of each component to the relative losses. The geometry and rigidity of the structure, the reflectivity and shape of the reflector, the optical and geometrical properties of receiver tube as well as the assembly accuracy need to be individually assed in order to optimize the design and assembly of the collector. The presentation gives a deeper insight into optical and thermal measurement technologies developed by DLR that can evaluate these aspects in detail.

 


Dr. Martin ROEB (DLR, Cologne, Germany)

 

Title: Thermochemical Reactions for Solar Energy Storage and Fuel Production


Abstract: Thermochemical multistep processes are promising options to face future energy problems. Such reactions can be used to enhance the availability of solar energy in terms of energy transport, of energy demand/supply management and of potential energy related applications. Coupling concentrated sunlight to suitable sequences of thermochemical reaction enables the production of hydrogen, syngas and other fuels derived from those precursors by water- and CO2-splitting as well as the storage of solar energy by breaking and forming chemical bonds in suitable reversible reactions.  These processes are sustainable and environmentally attractive since only water, CO2 and solar power are used as “raw materials”. All other materials involved are recycled within the process. The concentrated solar energy is converted into storable and transportable chemicals and fuels. One of the major barriers to technological success of many of those processes is the identification of suitable active materials like catalysts and redox materials exhibiting satisfactory durability, reactivity and efficiencies. Moreover, materials play an important role in the construction of key components of the respective high-temperature processes  and for the implementation in commercial solar plants.  Besides materials aspects also process engineering issues needs to be overcome. One of the most striking challenges is to couple an intermittent energy source to a chemical process. The most promising thermochemical processes are being described and discussed with respect to further development and future potential. The main challenges of those processes are being analyzed. Technical approaches and development progress in terms of solving them are addressed and assessed.
 

 

Dr. Manuel BLANCO (CSIRO. Australian Solar Thermal Research Initiative (ASTRI))

 

Title: The Australian Solar Thermal Research Initiative
 

Abstract: The Australian solar thermal research initiative (ASTRI) supports long-term research programs and aims to transform Australia into a global leader in concentrated solar thermal power (CSTP) technologies. Under ASTRI, six Australian universities, CSIRO, and several US National Laboratories and universities will be working on targeted research programs and producing large-scale collaboration on CSP across Australia. This $87.3 million initiative will move Australia to a leading position on solar energy research by building capability and knowledge within the country in the CSP field. The presentation will provide a general overview of ASTRI.
 

 

Pr. Markus HAIDER (TU, Vienna, Austria)


Title: Thermal and Thermo-chemical Storage Solutions for Concentrating Solar Energy Systems

Abstract: The possibility to store solar energy either in form of sensible or latent heat or in the form of heat of reaction of a thermo-chemical reaction is one of the key advantages of concentrating solar energy systems. The presentation will give an overview of both state of the art and state of research systems. Due to differences in the nature of the primary radiation absorption system, a rather wide spectrum of storage solutions is possible. The differences are triggered by the temperature and pressure level of the primary fluid, by the required storage duration and by transport considerations.
Liquid state nitrate salts are currently dominating sensible heat storage solutions for both line concentrating and point concentrating systems. In parallel many groups are working on research and market introduction of solid state storage media. Systems with direct steam generation require more sophisticated storage solutions, as a consequence of the combination of sensible/latent temperature/heat characteristic of the primary fluid. Thermo-chemical storage offers the double potential of long term storage and heat carrier transport.

 

 

Dr.-Ing. Philipp SCHRAMEK (Solar Tower Systems GmbH, Starnberg/Munich)


New Components and Technology for Solar Tower Plants


The main components of a solar tower plants are the heliostat field and the thermal receiver which is located on top of a tower. The heliostat field concentrates direct solar radiation onto the receiver which transfers the radiation into heat. Due to the high level of concentration of solar radiation on the receiver of a solar tower plant high temperatures of more than 550°C can be reached which leads to increased efficiency of power block. The main cost component in a solar tower power plant, including the power block, is the heliostat field, which can be in the range of 30 to 50% of the total costs of the solar power plant. Therefore any savings in the heliostat field have a high impact on the reduction of total costs of a solar tower plant. The presentation will give an overview of the technologies developed by Solar Tower Systems to achieve significant savings in the heliostat field.