Pathways to transform the German energy system by 2050

Dr. Hans-Martin Henning (Fraunhofer ISE)

Europe has agreed on ambitious targets to reduce greenhouse gas emissions. Each European country has translated these into national targets. Germany as an example aims at reducing national greenhouse gas emissions by at least 80 % up to 95 % until 2050 compared to the reference value of the year 1990. This keynote talk highlights cost-optimized pathways to achieve these targets based on a study considering all sectors and energy carriers. The model-based study investigates in detail various scenarios of system development and related costs to transform Germany’s energy system with increased energy efficiency and a dominant part of the energy generation using renewable energy sources.



Scheffler reflectors for steam generation, from process heat to power

Prof. Wolfgang Scheffler (Simply Solar)

Scheffler reflectors have a long operational history in India. The range includes: Single units, large scale cooking systems, which are now already in uninterrupted operation for the last 18 years, and systems for process heat. The latest addition is a 1 MWe solar power-plant with 24h operation, manufactured on site. A unique storage concept makes 24 hour operation possible, with a fully automated tracking, including automatic shape adaptation of the mirror. 


Innovative combinations of solar energy and heat pumps

Dr. Michel Haller (Institut für Solartechnik, SPF)

Research laboratories and the market have seen many innovative ideas and products for combinations of solar energy and heat pumps in recent years. There are good reasons why some of them have disappeared, whereas others are struggling to reach the market as niche products. This keynote talk provides a selection of innovations that are here today, and an educated guess on innovations that are here to stay!


Overall solutions for zero-energy buildings in the changing world

Prof. Jan Tywoniak (Czech Technical University, CTU)

A big general challenge is finding reasonable and achievable solutions for new generations of zero-energy buildings and for zero-energy building retrofit. Zero-energy concepts require a better co-operation of technical systems with building construction, accompanied by appropriate control. Building designs should be adapted to the local climatic and social situation and reflect changing climatic phenomena.  People remain as key elements – in the role of stakeholder, building designers, operators and users.   


Seasonal thermal storage


Prof. Wim van Helden (AEE-INTEC) 

Seasonal solar thermal systems provide a solution to one of the most challenging problems in energy supply, namely the covering of the high heating demands in winter by the abundant solar energy in summer. At large central scale, water pit storages are already commercially available and at distributed scale a number of novel technologies are being developed at the moment. An overview will be given of these developments and the challenges faced. 


Solar education


Prof. Klaus Vajen (Uni Kassel)

Solar education at all levels is of foremost importance for a successful implementation of solar energy technologies.


Potential of the Solar Heat for Industrial Processes in Spain

Prof.  Luisa Cabeza (CREA-UdL)

The SOLARCONCENTRA platform is an association working at the Spanish level to promote concentrating technologies with various work groups. In one of its work groups, dedicated to medium temperature applications, has developed potential studies for the use of solar heat for industrial processes.


Efficiency Limits for Solar Energy Conversion and the Opportunity for Hybrid PV – Thermal Collectors

Dr N.J. (Ned) Ekins-Daukes (Imperial College London)




Several photovoltaic solar cell technologies are approaching their fundamental efficiency limit for electrical power conversion.  Higher power conversion efficiency is possible with multi-junction structures but this is not yet cost effective.  Hybrid photovoltaic-thermal collectors therefore present an opportunity to attain high system efficiencies and meet a greater fraction of energy demand when collector area is limited.


                                                Illustrative picture:



How can we make the use of phase change materials in buildings economically feasible? 

Prof. Mohamed Mehdi Farid (The Univeristy of Auclkand)

The use of phase change materials (PCM) for thermal storage is a well-known approach aiming to increase thermal mass of buildings. The benefits of capturing solar radiation passively in winter, free night cooling in summer and also create peak load shifting have been well demonstrated in the literature. However, true assessment of these benefits has been in questions because of the improper use of PCM in many cases, making PCM use not economical with many years of payback. These aspects will be discussed in this presentation in an effort of making the use of PCM economically feasible. We have shown that the use of PCM in buildings could create energy cost saving, even if does not show some energy saving, through the application of electricity price based control.

Solar energy and Architecture: an integration challenge  

Dr. Maria Cristina Munari Probst (École Polytechnique Fédérale de Lausanne, CH)




Is it possible to maximize the use of solar without impoverishing the architectural quality of buildings and urban contexts?      

Are market products adapted , architects knowledge sufficient, urban regulations adequate?
State of the art , and possible improvements.






On the future of the photovoltaic conversion 

Prof. Antonio Luque (Institute of Solar Energy, Technical University of Madrid)

This presentation follows closely this I delivered when Boer Medal was presented to me in 2015.

It starts with a brief presentation of my relations with Professor Boer and with my own institute, whose name appears in my affiliation.
Then it tries to defend the necessity of the solar energy and the convenience of using the photovoltaic (PV) conversion; it is a thermal
machine whose hot reservoir is the sun at about 6000 K, leading to a tremendous potential for increasing efficiency. Next it describes
the role that Spain has played in the development of this technology al the power plant level.

As an example of the PV efficiency potential my own research on the Intermediate Band Solar Cell is introduced together with the
interest that this research has awakened. Yet it is concluded that PV generation is already close to find its own cost‐competitive way.
Now a next challenge is energy storage, very important for the intermittent solar energy but also for the energy management, including
he large scale one. PV has a big role to play here, because molten silicon is one of the cheapest ways to store energy and retrieving it
is best achieved by thermophotovoltaics converters based in special solar cell.

The preceding arguments are summarized in a list of conclusions.






University of Stuttgart
Research and Testing Centre
for Thermal Solar Systems (TZS)