The Power to Flex project aims to promote the development of storage possibilities from sustainable energy sources. Hydrogen is opted to be a feasible energy carrier, which can also be stored for prolonged times without further losses and can be transformed into electricity and heat when needed. Producing hydrogen from electrolysis processes has a low CO2 footprint, however the efficiency at both the system, stack and cell level still increases due to further research and development.Electrolysis is conventionally performed with direct current, of which the energy is usually supplied from the grid. Rectifiers are necessary to provide the energy source for electrolysis, which unfortunately waste some of the efficiency, albeit becoming more efficient. Although it is known that distortions, harmonics and ripple, in the current supply can cause decreased performance of the electrolysis, a fundamental understanding is often not provided in published research. Controlled modulation of the electrolysis process can however form a possibility to enhance the performance of electrolysis
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Ammonia is heavily used in agriculture as a fertilizer and in industry as a raw material for the production of various organic nitrogen compounds. Its high hydrogen content and its established infrastructure for both storage and distribution makes ammonia a prominent candidate for storing fluctuating renewable energy. The Haber-Bosch heterogenous reaction of hydrogen and nitrogen on an iron-based catalyst is used today at large scale ammonia production sites. The current industrial hydrogen production is dominated by fossil energy sources. The traditional Haber-Bosch process can become green and carbon-free if renewable electricity is used for hydrogen generation. However, a continuous operation of power to ammonia can be challenging with a fluctuating renewable energy source. Techno-economic models show that electrolysis and the hydrogen supply chain is the main dominating cost factor of power to ammonia.
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Excess of renewable electricity from wind turbines or solar panels is used for electrolysis of water. To store this renewable energy as methane, the hydrogen is fed to an anaerobic digester to stimulate biological methanation by hydrogenotrophic methanogens. This workpackage focusses on the best ways for hydrogen delivery and the community changes in a biomethanation reactor as a result of hydrogen supply.
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Excess of renewable electricity from wind turbines or solar panels is used for electrolysis of water. To store this renewable energy as methane, the hydrogen is fed to an anaerobic digester to stimulate biological methanation by hydrogenotrophic methanogens. These work packages focus on the best ways for hydrogen delivery and the community changes in a biomethanation reactor as a result of hydrogen supply.
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Power-to-gas technologies are considered to be part of the future energy sys- tem, but their viability and applicability need to be assessed. Therefore, models for the viability of farm-scale bio-power-to-methane supply chains to produce green gas were analysed in terms of levelised cost of energy, energy efficiency and saving of greenhouse gas emission. In bio-power-to-methane, hydrogen from electrolysis driven by surplus renewable electricity and carbon dioxide from biogas are converted to methane by microbes in an ex situ trickle-bed reactor. Such bio-methanation could replace the current upgrading of biogas to green gas with membrane technology. Four scenarios were compared: a refer- ence scenario without bio-methanation (A), bio-methanation (B), bio-methanation combined with membrane upgrading (C) and the latter with use of renewable energy only (all-green; D). The reference scenario (A) has the lowest costs for green gas production, but the bio-methanation scenarios (B-D) have higher energy efficiencies and environmental benefits. The higher costs of the bio-methanation scenarios are largely due to electrolysis, whereas the environmental benefits are due to the use of renewable electricity. Only the all- green scenario (D) meets the 2026 EU goal of 80% reduction of greenhouse gas emissions, but it would require a CO2 price of 200 € t−1 to achieve the levelised cost of energy of 65 €ct Nm−3 of the reference scenario. Inclusion of the intermittency of renewable energy in the scenarios substantially increases the costs. Further greening of the bio-methanation supply chain and how intermittency is best taken into account need further investigation.
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Wind and solar power generation will continue to grow in the energy supply of the future, but its inherent variability (intermittency) requires appropriate energy systems for storing and using power. Storage of possibly temporary excess of power as methane from hydrogen gas and carbon dioxide is a promising option. With electrolysis hydrogen gas can be generated from (renewable) power. The combination of such hydrogen with carbon dioxide results in the energy carrier methane that can be handled well and may may serve as carbon feedstock of the future. Biogas from biomass delivers both methane and carbon dioxide. Anaerobic microorganisms can make additional methane from hydrogen and carbon dioxide in a biomethanation process that compares favourably with its chemical counterpart. Biomethanation for renewable power storage and use makes appropriate use of the existing infrastructure and knowledge base for natural gas. Addition of hydrogen to a dedicated biogas reactor after fermentation optimizes the biomethanation conditions and gives maximum flexibility. The low water solubility of hydrogen gas limits the methane production rate. The use of hollow fibers, nano-bubbles or better-tailored methane-forming microorganisms may overcome this bottleneck. Analyses of patent applications on biomethanation suggest a lot of freedom to operate. Assessment of biomethanation for economic feasibility and environmental value is extremely challenging and will require future data and experiences. Currently biomethanation is not yet economically feasible, but this may be different in the energy systems of the near future.
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What will determine if power to gas will be an important technology in the energy transition over the next years? One can look at the development of a technology as a process that takes place in a technological innovation system (TIS). The TIS includes all actors and institutions that are involved in the development, diffusion and utilization of a technology. For a technology todevelop successfully the TIS should fulfil several functions. For power to gas technology several pilot projects are realized, studies are carried out and funds are available both for projects as for research. The functions called entrepreneurial activities, knowledge development, knowledge exchange and resource mobilization are all met. The function that faces the most problems iscalled market formation. There is not yet a regulatory framework for power to gas. Investors in power to gas also need to be rewarded for the benefits that they realize such as the avoided capital cost of extra infrastructure, the enabling of maximum utilization of renewable electricity and the increase in renewable content of the gas networks. Policy directed at market formation is therefor recommended.
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Caribbean coral reefs are in decline and the deployment of artificial reefs, structures on the sea bottom that mimic one or more characteristics of a natural reef, is increasingly often considered to sustain ecosystem services. Independent of their specific purposes, it is essential that artificial reefs do not negatively affect the already stressed surrounding habitat. To evaluate the ecological effects of artificial reefs in the Caribbean, an analysis was performed on 212 artificial reefs that were deployed in the Greater Caribbean between 1960 and 2018, based on cases documented in grey (n = 158) and scientific (n = 54) literature. Depending on the availability of data, reef type and purpose were linked to ecological effects and fisheries management practices around the artificial reefs. The three most common purposes to deploy artificial reefs were to create new dive sites (41%), toperform research (22%) and to support ecosystem restoration (18%), mainly by stimulating diversity. Ship wrecks (44%), reef balls© (13%) and piles of concrete construction blocks (11%) were the most-often deployed artificial reef structures and metal and concrete were the most-used materials. The ecological development onartificial reefs in the Caribbean appeared to be severely understudied. Research and monitoring has mostly been done on small experimental reefs that had been specifically designed for science, whereas the most commonly deployed artificial reef types have hardly been evaluated. Studies that systematically compare the ecological functioning of different artificial reef types are virtually non-existent in the Caribbean and should be a research priority, including the efficacy of new designs and materials. Comparisons with natural reef ecosystems are scarce. Artificial reefs can harbor high fish densities and species richness, but both fish and benthos assemblages often remain distinct from natural ecosystems. Studies from other parts of the world show that artificial reefs can influence the surrounding ecosystem by introducing non-indigenous species and by leaking iron. As artificial reefs attract part of their marine organisms from surrounding habitats, intensive exploitation by fishers, without clear management, can adversely affect the fish stocks in the surrounding area and thus counteract any potential ecosystem benefits. This study shows that over 80% of artificial reefs in the Caribbean remain accessible tofishers and are a risk to the surrounding habitat. To ensure artificial reefs and their fisheries do not negatively affect the surrounding ecosystem, it is imperative to include artificial reefs, their fisheries and the surrounding ecosystem in monitoring programs and management plans and to create no-take zones around artificial reefs that are not monitored.
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The installation of facilities replicating the realworld condition is often required for carrying out meaningful tests on new devices and for collecting data with the aim to create realistic device model. However, these facilities require huge investments, as well as areas where they can be properly installed. In this paper, we present a test infrastructure exploiting the concept of Remote Power Hardware-In-the-Loop (RPHIL), applied for characterizing the performances of a 8kW Proton Exchange Membrane (PEM) electrolyser installed at the Hanze University of Applied Sciences in Groningen (The Netherlands). The electrolyser is subjected to different test conditions imposed both locally and remotely. The results show that this measurement procedure is effective and can open new perspectives in the way to share and exploit the existing research infrastructure in Europe
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