7 February 2018
Silvan Siegrist and Pascal Kuhn are two of the five award winners of the Competition of Visions 2017. Siegrist is in shared first place with his concept of the Moving Brick Receiver Reactor (MBR2) and receives a grant of € 180,000. MBR2 could double the efficiency of sustainable synthesis gas production. Kuhn's vision of a combined data network of satellite imagery and publicly available cameras to improve solar performance predictions came in second place, earning € 80,000.
The DLR Competition of Visions honours creative suggestions of its employees in the fields of aerospace, transportation, energy and safety. The suggestions are judged by societal, scientific and economic relevance, the technological feasibility or applicability and the benefits for DLR. Particular attention is paid to 'out-of-the-box' ideas.
Synthesis gas or syngas is a mixture mainly composed of carbon monoxide (CO) and hydrogen (H2). It is an important intermediate for the production of basic industrial chemicals such as ammonia and methanol. So far, it is usually produced by steam reforming from natural gas or by the gasification of coal. However, there are also sustainable manufacturing methods. In a solar thermal process solar radiation is concentrated on a special metal oxide compound, a so-called redox material, and heated to about 1500 degrees Celsius. At this temperature the metal oxide releases oxygen (O2). The redox material is then cooled down to about 800 degrees Celsius and water vapour (H2O) and carbon dioxide (CO2) are introduced. The redox material extracts oxygen from both substances and returns to its original form. The water vapour and the CO2 are transformed into syngas. However, this method is rather inefficient due to significant losses of energy. Over half of the losses result from lost heat energy. In addition, the reaction cannot take place continuously, but only during the day with sufficient direct radiation. Therefore, this method has not been competitive so far.
Siegrist's MBR2 could change that. It is characterized by a new process control of the redox cycle, which allows it to operate around the clock thanks to storage units and to recapture a large part of the heat losses with a heat exchanger.
Instead of letting the redox reaction take place in a fixed reactor, Siegrist relies on movable metal oxide reactors- the bricks. Immediately after the reduction of the metal compound, the brick is moved out of the focus and the waste heat is used to preheat a second block. As a result, the energy losses fall dramatically. The solar researcher is confident: "Heat exchangers are a well-known technology and ours works on a simple principle."
The idea came to Siegrist during a lecture by colleagues on sequentially irradiated reactors. He wondered if it would be more efficient to move the redox material through the focus than to laboriously change the focus position. The storage principle is already applied to particle reactors and MBR2 expands it to a solid state with a new heat exchanger. The challenge now is to find metal oxide compounds that can also be used as redox material at temperatures around 1500 degrees Celsius and to make the position changes of the blocks as energy efficient as possible. The grant from the Vision for MBR2 Contest is spent on a PhD position to realize the idea.
Solar thermal energy and photovoltaics are key elements of a sustainable power generation. However, the delivered power is subject to significant fluctuations throughout the day. Whenever clouds cast shadows on solar systems, the dispatched electricity drops sharply. Optimized predictions of these fluctuations can partially replace expensive technical measures such as the incorporation of storage facilities, the provision of backup power plants or the expansion of the power grid. Currently, solar power forecasts are based on numerical weather models, data from weather satellites and cloud camera systems. Weather satellites provide solar predictions with a resolution in the kilometre range for the next few hours.
Kuhn is specialized in all-sky imagers, which provide accurate local cloud data and are already used in solar power plants. Cloud camera systems deliver forecasts with a higher temporal and spatial resolution than satellites- but only for the next few minutes. In short, satellites monitor large areas, but are light on details and cloud cameras provide high-resolution data, but only for limited areas and timescales.
By themselves, both methods are suitable to predict solar power in the power grid but are complementary and can enhance each other. However, all-sky imagers require frequent maintenance and there are relatively few of them, making them a bottleneck in solar energy predictions.
Kuhn is aiming to overcome that bottleneck. He plans to complement satellite data with data captured by networks of publicly accessible cameras. Kuhn’s vision relies on networks of public webcams and of citizen science meteorologists who freely share their images on the internet. The combination of the different datasets promises to be a cost-effective method to improve the accuracy of the weather forecast for solar energy systems. With his idea Kuhn breaks new ground. The challenge is huge: Is it feasible to evaluate the images of hundreds of thousands of cameras and connect them to satellite data? Kuhn is optimistic: "We hope to be able to combine the advantages of cloud cameras and satellites and look forward to give important impulses for further developments."
Siegrist and Kuhn are two of the five winners from a total of 54 applications that entered into the Competition of Visions 2017 competition. Of those, ten applicants were shortlisted by a jury and invited to present their visions to the DLR Board of Directors on 27th November and to apply for funding. The competition encourages especially the younger scientists. The aim is to make the creative potential of the scientists visible and to give them scope for development.