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Sektorenkopplung im Rahmen der Energiewende -Einsatz von Elektrolysesauerstoff auf kommunalen Kläranlagen
Abstract
Der Umbau der Energiewirtschaft hin zu regenerativen Energiequellen erfordert eine Auseinander-setzung mit der technischen Anpassungsfähigkeit der derzeitigen Infrastruktursysteme und der dazu-gehörigen Organisations-bzw. Betreibermodelle. So stellt sich die Frage, inwieweit bestehende Infra-struktursysteme neue Aufgaben in einem zukünftigen Energieversorgungssystem übernehmen kön-nen bzw. dafür ausgerüstet werden müssen. Als eines dieser Infrastruktursysteme ist die Abwasser-entsorgung zu sehen, die jedoch bislang kein Bestandteil einer sektorengekoppelten Betrachtung ist. Die Power to Gas-Technologie, bei der Wasser unter Einsatz von Elektrizität in Wasserstoff und Sau-erstoff zerlegt wird, bietet dafür einen Ansatz.
Die vorliegende Arbeit präsentiert die Ergebnisse aus Untersuchungen zur Nutzung des in der Regel nicht verwerteten Sauerstoffs aus der Wasserelektrolyse im Rahmen der biologischen Reinigungs-stufe kommunaler Kläranlagen. Der Sauerstoff ersetzt dabei die üblicherweise zur Versorgung der Mikroorganismen in das Abwasser eingebrachte Luft. In einer Versuchskläranlage im technischen Maßstab wurde hierbei über einen Zeitraum von 6 Monaten parallel der Betrieb mit Sauerstoff aus der Elektrolyse sowie der herkömmliche Betrieb mit Luft betrachtet.
Im Reinsauerstoffbetrieb konnten Verbesserungen des Stoffüberganges von Sauerstoff in Wasser ermittelt werden, so dass geringere Mengen an Sauerstoff eingebracht werden mussten als dies bei der Einbringung mit Luft notwendig war. Zudem stellten sich in den Versuchen auch die Abbauleistungen für Gesamtstickstoff und chemischen Sauerstoffbedarf (CSB) im Vergleich zur herkömmlichen Betriebsweise mit Luft um bis zu 20 Prozentpunkte verbessert dar. Dadurch können höhere Abwasserbelastungen behandelt oder perspektivisch kleinere Baugrößen der Behandlungsanlagen realisiert werden. Mit dieser Arbeit wird nachgewiesen, dass kommunale Kläranlagen grundsätzlich als Standorte für die Wasserelektrolyse in Betracht gezogen werden können, da durch die Sauerstoffabnahme eine zusätzliche Einnahmequelle entsteht.
... Before the hydrogen can be delivered to a vehicle, it must be compressed to the required pressure. The aerator for pure oxygen only works at an operating pressure of approximately 2.5 bar [32]. Therefore, the gas can be depressurized from 90 bar before it Is introduced into the aeration tank of the WWTP. ...
... Before the hydrogen can be delivered to a vehicle, it must be compressed t the required pressure. The aerator for pure oxygen only works at an operating pressur of approximately 2.5 bar [32]. Therefore, the gas can be depressurized from 90 bar befor it Is introduced into the aeration tank of the WWTP. ...
... Before the hydrogen can be delivered to a vehicle, it must be c the required pressure. The aerator for pure oxygen only works at an opera of approximately 2.5 bar [32]. Therefore, the gas can be depressurized from it Is introduced into the aeration tank of the WWTP. ...
In order to harmonize supply and demand of green energy, new future-proof technologies are needed. Here, hydrogen plays a key role. Within the current framework conditions, the production of green hydrogen is not yet economically viable. The use of the oxygen produced and the possible increase in efficiency associated with it mostly remains unconsidered. The aim is to demonstrate that the economic efficiency of a power-togas (PtG) project can be increased by using the by-product oxygen. In this research project, a water electrolyser connected to grid is powered to supply hydrogen to a hydrogen refuelling station. By utilising the by-product oxygen from water electrolysis for a wastewater treatment plant (WWTP), it is shown that the net present value (NPV) of the project can be improved by up to 13 % compared to the initial scenario. If a photovoltaic (PV) system is used in addition to grid electricity for higher green hydrogen production, the NPV can be further improved by up to 58 %. The levelized cost of hydrogen (LCOH) is calculated for different scenarios with and without oxygen configuration. A sensitivity analysis is then performed to find important parameters.
... Regarding purification quality, approaches for a pure O 2 system in Spain showed no significant increase in COD (chemical oxygen demand), BOD (biochemical oxygen demand) or TN (total nitrogen) removal, whilst energy savings were assumed [54]. In contrast, a study in Germany showed that, in comparison with a conventional system, an additional reduction of up to −20% for COD and TN is possible, but no energy savings could be achieved [47]. At the Nürnberg WWTP (Germany), pure oxygen is successfully used for years as the first biological treatment step for COD removal [55], and at the Lynette WWTP (Copenhagen, Denmark), pure O 2 was used to support the biological treatment step for 15 years. ...
... For pure oxygen systems, an additional mixing system is required, and deeper basins are favorable due to a longer contact of the O 2 bubbles with the media. The authors of [46,47] showed that shallow basins or volatile fill levels might cause losses in the purification quality. Furthermore, the reduced gas volume of the pure O 2 system is insufficient for mixing the media and preventing sludge settling in common aeration tanks. ...
... To solve this problem, it could be required to add chemicals (e.g., milk of lime; cf. [47]) or add additional aeration times for the system (cf. [46]) to sustain the biological treatment. ...
The development of a power system based on high shares of renewable energy sources puts high demands on power grids and the remaining controllable power generation plants, load management and the storage of energy. To reach climate protection goals and a significant reduction of CO2, surplus energies from fluctuating renewables have to be used to defossilize not only the power production sector but the mobility, heat and industry sectors as well, which is called sector coupling. In this article, the role of wastewater treatment plants by means of sector coupling is pictured, discussed and evaluated. The results show significant synergies—for example, using electrical surplus energy to produce hydrogen and oxygen with an electrolyzer to use them for long-term storage and enhancing purification processes on the wastewater treatment plant (WWTP). Furthermore, biofuels and storable methane gas can be produced or integrate the WWTP into a local heating network. An interconnection in many fields of different research sectors are given and show that a practical utilization is possible and reasonable for WWTPs to contribute with sustainable energy concepts to defossilization.
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