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Synlight - an innovative solar research facility


Hydrogen is considered to be the fuel of the future because it burns without producing carbon dioxide. But the production of hydrogen – by splitting water into its constituents of hydrogen and oxygen – needs significant amounts of energy. In the future, this will be obtained from the Sun. "Renewable energies will be the mainstay of global power supply in the future," said DLR (German Aerospace Center) Executive Board Member Lemmer, emphasizing the relevance of intensive research into alternative energy production. "Fuels, propellants and combustibles acquired using solar power offer immense potential for long-term storage and the production of chemical raw materials, and the reduction of carbon dioxide emissions. Synlight will enhance our research in this field."

The world's largest artificial Sun started shining on 23 March 2017 in Jülich, Germany at the DLR Institute of Solar Research when the new research facility Synlight was inaugurated in the presence of German Ministers as well as DLR Executive Board Members. Among other things, the facility is intended to develop production processes for solar fuels, including hydrogen. 1)


Figure 1: The world's largest solar simulator is located at the DLR facility in Jülich. The 149 high-performance Xenon short-arc lamps simulate natural solar radiation. Independent of weather conditions, the simulator will bring faster progress to solar fuel manufacturing (image credit: DLR)

‘Synlight' is the name of the research facility that Kai Wieghardt from the DLR Institute of Solar Research and his team have been developing and building since mid-2014. The goal is to provide optimal test conditions for solar thermal and solar chemical research, as well as for the development of components for the aerospace industry – regardless of the weather and time of day. 2)

Sun at the touch of a button

There have always been laboratory-scale systems for solar research. The high-flux solar simulator at the DLR site in Cologne, for instance, allows researchers to conduct solar radiation experiments on a small scale, and the weather-dependent solar tower in Jülich accommodates large-scale experiments. And now, there is also a place for solar research projects in between – Synlight. "With Synlight, we have achieved a whole new level of solar test conditions, and the development of the world's largest artificial Sun has bridged the gap between conventional high-flux solar simulators and solar towers," Wieghardt says. "The more than 350 kW of radiative power exceeds that of any of the currently available high-flux solar simulators in the world." There are no systems of a comparable size. The advantages: the test conditions can be very accurately adjusted and the scientists can conduct experiments independently of the weather. This will allow the further promotion of solar energy as a power source as well as boost the development of solar power plants.

The building in which the Sun shines at the touch of a button resembles a two-stage cube. The front area is occupied by the control offices and three radiation chambers, where the tests take place. The frame of the artificial Sun is located in the back. An array of 149 Xenon short-arc lamps arranged in 13 rows is mounted on a 15 m tall steel structure. "These lamps are also used in cinemas. Their emission spectrum closely matches that of sunlight," says Wieghardt, explaining the choice of lamps. Each individual 7 kW lamp is surrounded by a 1 m diameter ellipsoid-shaped aluminum reflector. The structure as a whole is a bit reminiscent of a honeycomb – except that what is collected in the reflectors is not honey, but light.

Each reflector, with its lamp, is mounted on a telescopic arm that can be individually adjusted from a control room. Each radiator module operates independently. "This makes it possible for us to concentrate or spread out the light from all the lamps. The target points are located 8 m away in the radiation chambers. Here, we want to achieve a light concentration corresponding to 10,000 times the solar radiation. This allows us to reach temperatures exceeding 3000 degrees Celsius – which is more than is usually achieved in combustion processes," Wieghardt explains. When all the lamps are switched on, the air in the research facility can heat up to as much as 50ºC; cooling is therefore essential. This is achieved by using an air system that blows cool air in through the rear wall and releases the heated air via the roof.

Three simultaneous tests in three radiation chambers

The facility receives 3.5 million euro in funding from the Ministry for Climate Protection, Environment, Agriculture, Conservation and Consumer Protection of the State of North Rhine-Westphalia and the German Federal Ministry for Economic Affairs and Energy. It is available to users from research facilities and industry for experimental purposes. The flexibly adjustable radiator modules and three radiation chambers arranged side by side make it possible for up to three users to carry out experiments in the facility at the same time. For this, the light from the lamps is divided into three subsets – one for each of the chambers – either bundled to focus onto one point or distributed over a larger area.

"We have optimized the radiation chambers for different fields of application," Wieghardt continues. "We are now standing in the UV chamber, which means that the lamps facing us emit more UV light than the lamps on the left side of the construction. This can, for example, be of interest to our colleagues in aerospace research, as their components are generally exposed to particularly high levels of UV radiation." The other two chambers are specially designed to meet the requirements that come with solar-chemical process development testing. They are equipped with a stainless steel pipe that is directly connected to an adjacent room in which the exhaust gases are neutralized and washed – a prerequisite for many solar-chemical experiments.

A flat, wheeled trolley with a maximum payload of 2500 kg is used to pick up the test objects from the delivery hall on the ground floor. From there, they are pushed on a system of rails into the elevator and then into the radiation chamber, where they are positioned. In the front part of the building, shielded by a massive concrete wall, are the control and measuring rooms for the chambers. From here, the research partners – together with a DLR staff member – control the individual radiator modules. They can also monitor their experiment and evaluate the measurement results on screen.

To operate, Synlight needs energy – a lot of it. In three hours, the system consumes as much electricity as a four-person household in a whole year. However, these kinds of tests are restricted to just a few hours per month. "The aim of the facility is to obtain more energy from the Sun in the future. If we were to increase the efficiency of a solar power plant by one percent, we would be able to supply electricity to an additional 1000 households per year," says Wieghardt.


Figure 2: An equivalent power of 10,000 times the solar radiation focused on one spot: 149 Xenon spotlights can be concentrated on a 20 x 20 cm area. This results in temperatures of up to 3000 degrees Celsius (image credit: DLR)

A way to the fuel of the future

The projects are from different research fields. The focus of Synlight, however, is to produce solar-generated fuels – because in the future it should be possible to ‘refuel' with energy from the Sun. Solar fuels are one way of making the transport sector climate-neutral. For instance, hydrogen could be the fuel of the future – either directly in fuel cell vehicles or as an intermediate for the production of liquid fuels, such as kerosene. With solar energy, it is possible to split water into hydrogen and oxygen directly, without electricity and electrolysis. DLR researchers have already tested this successfully on a small scale.

No more than three years have elapsed since the funding agreement and the start of the project through to the festive opening of Synlight. During this time, the building, including its elaborate technical equipment, was designed, approved and built. Things did not always go smoothly because the facility is situated on historical land. A farm from the Roman Empire was located where the facility now stands. "This had to be secured before we could start constructing the building," Wieghardt recalls. In parallel with this, the researchers developed their system, built a module as a prototype and, after its successful test, installed it in their facility mainly using their own resources. "For DLR, it is probably rather unusual that a facility of this size has not been completely constructed by a general contractor," Wieghardt says. "But in this way, we were fully in control of the costs and were even able to equip Synlight with twice the originally planned radiative power without exceeding our budget. And, of course, we know our facility extremely well now."

The first attempt at generating solar hydrogen is currently under way, and the solar experts are hoping to use their facility for many more experiments in the near future. This ‘Glorious Giant' in Jülich is therefore boosting solar research and the development of new energy technologies – no matter the weather.


1) "DLR inaugurates the world's largest artificial Sun," DLR, March 23, 2017, URL:

2) Jana Wiedemeyer, "Sun at your Fingertips: Part two of the ‘Glorious Giants' series – Synlight," DLR magazine 153 Solar Research, April 2017, pp: 48-51, URL:

The information compiled and edited in this article was provided by Herbert J. Kramer from his documentation of: "Observation of the Earth and Its Environment: Survey of Missions and Sensors" (Springer Verlag) as well as many other sources after the publication of the 4th edition in 2002. - Comments and corrections to this article are always welcome for further updates (

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