While the countries the Cop26 climate conference in Glasgow first agreed initial targets and possible measures to protect the climate, others are moving forward with very practical measures to reduce greenhouse gases. The district of Düren in North Rhine-Westphalia, for example, wants to become climate neutral by 2035. Public passenger transport is a key factor here. In future, buses and trains will run on hydrogen. The light element is obtained from water, which is divided by an electrolyser to form hydrogen and oxygen.
However, this is only climate neutral if the power for the electrolyser comes from renewable sources, preferably from sunlight or wind energy. The foundation for this was laid on 27 October 2021: the groundbreaking for the Merscher Höhe solar park in Jülich. Around 17,000 photovoltaic modules spanning 9.5 hectares produce 9.2 megawatts and accumulate 9.7 gigawatt hours of energy that feeds the electrolyser. “We are experiencing a historic hour when it comes to climate protection”, praised district administrator Member Wolfgang Spelthahn.
Hydrogen for buses and trains
With electricity from the solar park, 170 tons of hydrogen can be generated every year. In the first phase, this will be used to supply the buses and trains ordered by the district. A total of up to 20 trains and 170 buses will run on them. The very light hydrogen gas has a low density, which is why it is compressed and pressed into four tanks sitting on mobile trailers at a pressure of up to 350 bar. These can then be transported to nearby petrol stations, where buses and trains are provided with corresponding refuelling options.
In future, the hydrogen can also be consumed on the Brainergy site, for example as an admixture to natural gas for building heating. Brainergy is a business and innovation park in the district of Düren with a focus on renewable energies. The park is located in the middle of a lignite coal production region and is intended to help overcome the structural change caused by the end of coal production. There is a great deal of interest. Some companies wanting to establish themselves there, for example, have already declared their need for oxygen that is produced as a waste product during electrolysis. The waste heat from hydrogen generation is also intended to be fed into a low-energy grid in the Brainergy Park and can also be used for building heating.
Specialised foundation
Rurenergie GmbH is operated by the solar park built by F&S solar service GmbH. F&S solar service GmbH develops, finances and builds large, turnkey solar parks around the world. Despite decades of experience in constructing ever larger solar power plants, the Jülich project is a challenge in many respects. On the one hand, it is the first project of its size where solar power flows via a direct cable connection to produce hydrogen. Secondly, specially manufactured screw anchors are used here to mount the frame for the modules.
After all, the site where the Deutsche Welle radio masts were located until recently is a suspected explosive ordnance site. In the 1960s, the ground was heaped up with several metres of earth and interspersed with all kinds of metallic structures, meaning that probing in advance is not sufficiently possible. In order to still be able to provide the assembly teams with protection against possible explosive ordnances, the classic frame posting method had to be omitted due to the vibrations caused by the impact. The solution for the approx. 7000 anchors required was to use screw foundations. The screw foundations are remotely screwed into the ground around one and a half metres deep from a secure distance and support the PV module construction.
For F&S solar service GmbH, this solar power station is not the first with screw-in foundations. The Inden solar power plant was also built turnkey by the Euskirchen-based company for Rurenergie in 2011 and screw foundations were also used here due to the landfill body.
All cables produced by Lapp
The photovoltaic modules in the Merscher Höhe solar park come from Asia, while all other components come from Germany – the inverters are supplied by SMA and the electrolyser is supplied by Siemens, and all cables are produced by Lapp. The global market leader for cables and integrated electrical connection systems is supplying 210 kilometres of string cables to the construction site. They always connect 27 modules, each with an output voltage of around 42 volts, to form so-called strings. A total of 22 strings are connected in parallel to one of the 29 switching boxes.
From there, over 21 km of DC master cable run to the inverters. The transition to the medium voltage network is guaranteed by 5.5 km of AC cables. LAPP is also supplying 3.5 km of fibre optic cables for monitoring the inverters and for data transmission from the weather station. Each string is individually monitored. The entire plant is equipped to meet the requirements of the grid operators. This is necessary for the grid operator to control the solar park remotely when required, for example in the event of excess electricity or to stabilise the grid.
To the construction site on time
“We have had very good experiences with Lapp, which is why we use these cables in all of our solar parks worldwide“, praises Jens Brücken, Technical Director at F&S solar service GmbH. Above all, Lapp’s delivery capability is a major advantage. While planning a solar park can take years – it took six years in Jülich – the actual construction is relatively fast. The average time it takes is three to six months, but the very large solar park in Monte Cristi in the Dominican Republic, where F&S solar acts as general contractor and operator, took eight months. However, this is only possible if the components arrive on time to the construction site. There are a number of bottlenecks due to the coronavirus crisis, such as modules from Asia, which have also recently risen in price.
By contrast, there has never been a delivery problem at Lapp. “There are not many manufacturers who can deliver such large quantities of cables at all”, says Brücken. For Monte Cristi, Lapp even created detailed documents about the contents of the containers so that customs officials can immediately see that they are components for renewable energy, as only these are exempted from the high import duties.