The Possible Roles of Wastewater Treatment Plants in Sector Coupling

Abstract

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 CO 2 , 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.Energies 2020, 13, 2088 2 of 20 reached, like in Uruguay, Germany and the United Kingdom [6]. The gradual extension of RES and the expedited abandonment of fossil and nuclear energy production results in new problems but also new opportunities for power supplies. There is a shift from demand-oriented power generation to a production-driven generation of electrical energy. In an electricity system with a high share of RES, flexibility options are needed to counterbalance fluctuating wind and solar-based power production to maintain the high standards in its supply [7]. For now, there are just a few hours of surplus energy but with proportions of more than 60% RES; times in which supply exceeds demand are increasing significantly. On this basis, there will be a high need of short-term flexibility in the near future to stabilize power grids and further integrate RES into the energy grids [8]. Short-term storage options are classified in the range of seconds up to 24 h (daily storage). These energy surpluses and deficits have to be balanced by flexible energy generators and consumers. Furthermore, long-term storage capacities are needed to provide enough energy in times of deficits on a larger scale. This is caused by longer periods of low amounts of available wind and sun. To compensate these fluctuations and store or generate energy, based on its availability, fundamentally different applications compared to short-term flexibility are required [9].Energy has always been stored, but the focus and the technologies used have changed. Storage concepts like pumped storage plants, battery or compressed air systems are not suitable for long-term storage-too expensive or cannot provide enough capacities for an extensive use in every country [10]. Additionally, ecological issues and resource scarcity have to be considered. Unlike solar and wind-based energy p...

Evaluating Spatial Interdependencies of Sector Coupling Using Spatiotemporal Modelling

“…Recent studies mainly focus on the technical aspects of SC, such as infrastructure optimisation [19], SC facilities [20], or SC solutions like demand and response systems [21]. Other research also tried to include economic considerations of SC [3].…”

Seasonal Energy Storage Potential Assessment of WWTPs with Power-to-Methane Technology

“…In this research, polymer electrolyte membranes (PEMEC) electrolysis is applied, which is preferred for seasonal energy storage (as it is applied also by Power-to-Gas Hungary Kft), mainly because of its high flexibility, fit to volatile renewable energy generation, and high technology-readiness level [23]. While hydrogen is going to be used in the next P2G step (methanation), oxygen generation can also be exploited at WWTPs; the efficiency of the aeration system can be increased by injection of oxygen into it [8].…”

“…While the promising role of the P2G technology in the energy sector has been argued comprehensively in recent years (e.g., from the aspect of long-term energy storage [2], system analysis [6] or technological and economic factors [7]), researchers have also started to focus on the role of WWTPs with respect to different aspects of renewable energy transition and power-to-X technologies. Schäfer et al [8] pointed out that WWTPs have notable synergy potential in sector coupling, for example, hydrogen and methane can be produced at WWTPs (with P2G technologies), and the oxygen (as the byproduct of the electrolysis) can be used to enhance purification processes. Gretzschel et al [9] focused on power-to-hydrogen (P2H) technology and the elimination of organic micropollutants at WWTPs, considering the possibility of offering system service, as well: automatic frequency restoration reserve (aFRR), which can provide short-term flexibility for network operators.…”

Advanced Wastewater Treatment to Eliminate Organic Micropollutants in Wastewater Treatment Plants in Combination with Energy-Efficient Electrolysis at WWTP Mainz

“…Based on the electricity sector driven by renewables, power-to-x technologies can supply the required transformation of energy to the other sectors to substitute fossil-based resources and lead to more stability of the system. A large review of the possible role of WWTPs by means of sector coupling is given in [19]. Practical implementations and their impacts on the processes are depicted, discussed and evaluated.…”

“…Furthermore, storable methane gas can be produced at WWTPs, which can contribute to an implementation of local heating networks. As explained in detail in [19], an interconnection in many fields of different research sectors is given and it is shown that it is possible and reasonable for WWTPs to contribute with sustainable energy concepts to defossilization. Thus it can be assumed that many WWTPswill be able to support the energy transition with its gas potentials and flexibility options if suitable management concepts are applied (cf.…”