Article

Cost effective power-to-X plant using carbon dioxide from a geothermal plant to increase renewable energy penetration

Authors:
To read the full-text of this research, you can request a copy directly from the authors.

Abstract

In the framework of a scenario with an always increasing share of generation from variable renewable sources, the need for systems able to store energy or to convert the excess generation into useful goods is becoming of paramount importance. While several projects and pilot plants deal with direct energy storage or with the conversion of the excess generation into other energetic goods (hydrogen or methane) often overlooking economic considerations, this paper proposes a cost-effective approach in which liquified methane and oxygen are produced and sold on their specific markets, which represents one of the first profitable Power-to-X applications at current market values. The paper presents the completely new and never investigated before idea of coupling the plant with a freely available source of pure carbon dioxide from a geothermal unit, thus making it possible to produce synthetic methane to be liquefied, stored and then used in other sectors of the society. The carbon dioxide coming with the geothermal fluid is no longer released in the environment as it currently naturally happens even when not going through the geothermal facility. Detailed models of the main system components were created, and an optimization procedure was carried out. Interestingly, the revenues from the sale of liquefied oxygen are well above those coming from synthetic methane and turn the system profitable. With a proper operation planning, bidding on the electricity day-ahead-market, a large hydrogen storage system proved to be unnecessary. The results of the system optimization clearly show that this kind of systems, although conceived in a very favourable condition, can become profitable only if the energy storage function is coupled with the production of other goods services. Assuming an average electricity price of 52 €/MWh, the plant profitability is achieved for an LNG selling price of 0.45 €/kg and an LOx price around 0.30 €/kg. These figures will rapidly decrease in the near future as lower electricity prices are forecasted.

No full-text available

Request Full-text Paper PDF

To read the full-text of this research,
you can request a copy directly from the authors.

... • Hydrogen compression to 700bar requires 5.3-6 kWh/kg (16-18% of LHV), liquefaction 10-15 kWh/kg (30-45% of LHV) [53,57,58]. • Methane compression to 220 bar 0.15 kWh/kg (1% of LHV) and liquefaction 0.3-0.6 kWh/kg (2-4% of LHV) [59]. Conversion of e-hydrogen into other e-fuels has a maximum theoretical conversion efficiency (on an LHV basis) determined by the chemical stoichiometry of the synthesis reaction: ...
... • Hydrogen compression to 700bar requires 5.3-6 kWh/kg (16-18% of LHV), liquefaction 10-15 kWh/kg (30-45% of LHV) [53,57,58]. • Methane compression to 220 bar 0.15 kWh/kg (1% of LHV) and liquefaction 0.3-0.6 kWh/kg (2-4% of LHV) [59]. ...
... E-methane, often called also synthetic natural gas (SNG), is produced with this reaction, also called the 'Sabatier reaction' in honour of the French chemist Paul Sabatier who discovered it. Usually, the CO 2 is compressed up to 30 bar and introduced into a methanation reactor at 300 • C [59]. These are the optimal operating conditions for the Sabatier reaction to occur [100]. ...
Article
Full-text available
Road transport is one of the most energy-consuming and greenhouse gas (GHG) emitting sectors. Progressive decarbonisation of electricity generation could support the ambitious target of road vehicle climate neutrality in two different ways: direct electrification with onboard electrochemical storage or a change of energy vector with e-fuels. The most promising, state-of-the-art electrochemical storages for road transport have been analysed considering current and future technologies (the most promising ones) whose use is assumed to occur within the next 10–15 years. Different e-fuels (e-hydrogen, e-methanol, e-diesel, e-ammonia, E-DME, and e-methane) and their production pathways have been reviewed and compared in terms of energy density, synthesis efficiency, and technology readiness level. A final energetic comparison between electrochemical storages and e-fuels has been carried out considering different powertrain architectures, highlighting the huge difference in efficiency for these competing solutions. E-fuels require 3–5 times more input energy and cause 3–5 times higher equivalent vehicle CO2 emissions if the electricity is not entirely decarbonised.
... Nevertheless, the discussion regarding the importance of a management strategy should not be confined solely to the electrolysis system but can be expanded to the entire P2G system, in particular when an intermediate Hydrogen Storage (HS) system is employed to decouple the ES and the MU. Baccioli et al. [26] analyze the costs associated with the production and sale of liquefied methane and oxygen from a P2G plant associated with a CO 2 source from a geothermal plant. This study reveals that using HS does not increase the cost-effectiveness of the plant, while "only small storage systems will be needed for managing the different dynamic behavior of the components" [26]. ...
... Baccioli et al. [26] analyze the costs associated with the production and sale of liquefied methane and oxygen from a P2G plant associated with a CO 2 source from a geothermal plant. This study reveals that using HS does not increase the cost-effectiveness of the plant, while "only small storage systems will be needed for managing the different dynamic behavior of the components" [26]. Gorre et al. also published two studies on this subject [27,28]. ...
... Several models for power-to-gas systems were proposed in the literature. In particular, Baccioli et al. [12] analyze the costs associated with the production and sale of liquefied methane and oxygen from a power-togas plant associated with a CO2 source from a geothermal plant. This study reveals that using hydrogen storage does not increase the cost-effectiveness of the plant, while "only small storage systems will be needed for managing the different dynamic behavior of the components" [12]. ...
... In particular, Baccioli et al. [12] analyze the costs associated with the production and sale of liquefied methane and oxygen from a power-togas plant associated with a CO2 source from a geothermal plant. This study reveals that using hydrogen storage does not increase the cost-effectiveness of the plant, while "only small storage systems will be needed for managing the different dynamic behavior of the components" [12]. Gorre et al. also published two studies in this subject [13,14]. ...
Conference Paper
Full-text available
Despite the impact of global warming on the living conditions of the Earth, fossil fuels still dominate the global energy scenario. The precariousness of our energy system requires the use of more reliable and less polluting energy sources, but a greater penetration of intermittent renewables implies the need for large-scale flexible energy storage. This need, combined with the growing interest in the use of hydrogen in mobility and industry, makes the prospect of including this energy vector in our daily lives tangible. However, the problems related to the development of dedicated infrastructures make its positioning on the market complex. In a transition phase, power-to-gas systems constitute an emerging solution that allows the use of existing structures for natural gas and, at the same time, solves the problem of hydrogen storage. In this study, a power-to-gas system producing synthetic methane from wind energy was modelled. Management strategies for both the electrolysis system and the hydrogen storage tank were tested to assess the flexibility and versatility of the system. Particular attention was dedicated to the analysis of the impact of the storage on the mitigation of the operating condition fluctuation of the methanation unit. Results of the simulations showed similar performances of the four electrolyzers and a limited number of methanation unit shutdowns. Nevertheless, the annual utilization factor of the subsystems was low, and this suggests a further investigation of the subsystems’ sizing. Overall, the effectiveness of the management strategies developed for the power-to-methane system makes the proposed model a good instrument to be used for further analysis and evaluations.
... An additional advantage of PtM technology, and one that is of great interest, is the possibility it offers for CO 2 utilization [12]. Biogas production, tail gas from power plants or industrial processes, direct air capture and geothermal units have been proposed as sources for the CO 2 to be supplied to the PtM system [4,13]. This paper evaluates the alternative of supplying PtM with the CO 2 streams generated by advanced carbon capture technologies. ...
... • The load hours of PtM systems significantly influences LCA results [33]. • Different CO 2 sources can be considered: flue gas from power stations, the cement industry, biogas upgrading, CO 2 extracted from ambient air and geothermal units [13,31,34,35]. • The highest greenhouse gas emission benefit is attained when biogenic and atmospheric sources are provided [34]. ...
Article
Power-to-methane (PtM) systems may allow fluctuations in the renewable energy supply to be smoothed out by storing surplus energy in the form of methane. These systems work by combining the hydrogen produced by electrolysis with carbon dioxide from different sources to produce methane via the Sabatier reaction. The present work studies PtM systems based on the CO2 supplied by the chemical looping combustion (CLC) of biomass (PtM-bioCLC). Life- cycle- assessment (LCA) was performed on PtM-bioCLC systems to evaluate their environmental impact with respect to a specific reference case. The proposed configurations have the potential to reduce the value of the global warming potential (GWP) climate change indicator to the lowest values reported in the literature to date. Moreover, the possibility of effectively removing CO2 from the atmosphere through the concept of CO2 negative emissions was also assessed. In addition to GWP, as many as 16 LCA indicators were also evaluated and their values for the studied PtM-bioCLC systems were found to be similar to those of the reference case considered or even significantly lower in such categories as resource use-depletion, ozone depletion, human health, acidification potential and eutrophication. The results obtained highlight the potential of these newly proposed PtM schemes.
... Refs. [16,59,79]). It was assumed that electrolysis uses renewable sources of electricity as a possible incorporation of power-to-methane systems [16]. ...
Article
Full-text available
In the process of upgrading biogas to biomethane for gas grid injection or use as a vehicle fuel, biogenic carbon dioxide (CO₂) is separated and normally emitted to the atmosphere. Meanwhile, there are a number of ways of utilizing CO₂ to reduce the dependency on fossil carbon sources. This article assesses the climate performance of liquefied biomethane for road transport with different options for utilization or storage of CO₂. The analysis is done from a life cycle perspective, covering the required and avoided processes from biogas production to the end use of biomethane and CO₂. The results show that all of the studied options for CO₂ utilization can improve the climate performance of biomethane, in some cases contributing to negative CO₂ emissions. One of the best options, from a climate impact perspective, is to use the CO₂ internally to produce more methane, although continuous supply of hydrogen from renewable sources can be a challenge. Another option that stands out is concrete curing, where CO₂ can both replace conventional steam curing and be stored for a long time in mineral form. Storing CO₂ in geological formations can also lead to negative CO₂ emissions. However, with such long-term storage solutions, opportunities to recycle biogenic CO₂ are lost, together with the possibility of de-fossilizing processes that require carbon, such as chemical production and horticulture.
... Another study used a 4 A framework that included i) availability, ii) acceptability, iii) applicability, and iv) affordability to evaluate the security of supply [38]. Some studies also mentioned optimization or network integration to minimize costs or maximize the use of CO₂ [39][40][41][42][43][44][45][46][47]. Therefore, the main indicators employed for the methodologies were summarized as part of the literature review. ...
Article
Full-text available
Carbon capture and utilization has been proposed as an essential climate change mitigation strategy, but only a few implemented cases exist. During biomethane production from anaerobic digestion, CO₂ is commonly separated and emitted into the atmosphere, which can be utilized as raw material for various products. This research aims to identify and assess CO₂ utilization alternatives for possible integration with biogas upgrading from anaerobic digestion by developing a soft multi-criteria analysis (MCA). A literature review complemented with stakeholder participation enabled the identification of relevant alternatives and criteria for assessment. Potential alternatives for CO₂ utilization include methane, mineral carbonates, biomass production, fuels, chemicals, pH control, and liquefied CO₂. Results show that although no alternative performs well in all indicators, there is an opportunity for short-term implementation for methane, biomass production, mineral carbonates, liquefied CO₂, and pH control. Moreover, the uncertainty analysis reveals that even though the technologies have a high technological development, more information on critical aspects is still required. The soft MCA provides information to decision-makers, practitioners, and the academic community on learning opportunities of the alternatives and indicators to step from development into implementation. For instance, the method can be used to assess more specific systems with different locations and scales or to direct efforts to ease the implementation of CCU.
... The increased penetration of not-programmable RES will also face problems of dispatchability, and, in some hours, the supplied electricity could be larger than the demand thus causing a surplus of energy. When overgeneration occurs, electricity must be recovered in short-term [11] or long-term storage [12], converted into different energy forms, or curtailed [13,14]. Other authors used LCA approach to evaluate the sustainability of electricity mixes of European countries in 2030, finding an average reduction of 42% in the impacts on climate change (with the only exception of Belgium [15]) and proving the impact of Italian PNIEC (forecast of 46% reduction of gCO2eq/kWh) [16]. ...
Article
Full-text available
The need to reduce greenhouse gas emissions is driving many actions to decarbonize the most impactful sectors. Among these, the energy sector accounts for almost one third of emissions. Increasing the penetration of renewable energy in the energy mix could easily reduce the emissions of this sector. Theoretically, the target to aim for would be 100% renewable energy production. However, the variable nature of power production from photovoltaic and wind systems, which are expected to play a key role in the energy transition, may pose several limitations to the effective penetration of renewable energy. Many concerns arise when one considers the large diffusion of renewable energy that would be required to meet green targets, and the operating conditions of other systems in charge of compensating for renewable energy variations. This study aims to investigate the potential impact of an increase in the amount of renewable energy installed in a country, particularly in Italy. A simplified approach has been used, based on the assumption of knowing the hourly demand and power generation mix, and multiplying the intermittent power generation by a certain factor. Although not accurate, this approach allows the authors to highlight some critical aspects regarding the potential surplus of renewable energy and the operating conditions of other energy sources. The results of this study may provide a useful basis for a preliminary system evaluation, in particular to assess the feasibility of surplus recovery and the operability of residual generation systems. In addition, it may be easily replicated in other countries for similar estimations.
... With the increase in the penetration of non-programmable REs, problems of dispatchability arise, and the electricity produced could be even more than the requested load causing an energy surplus for some hours. Electricity surplus must be stored in short-term [8] or long-term storage [9], converted into another energy vector [10], or simply curtailed. ...
... A group of studies includes optimization of plant capacities and multiple energy vectors but take the perspective of a single plant. Study [25] created a process model for the P2G plant, which was then linearized for the purpose of optimization against electricity market. The study paid particular attention to oxygen revenues and very high oxygen prices were also considered. ...
Article
Full-text available
Power-to-gas technology has been proposed as one component for future energy systems facing decarbonization targets. This paper presents a power-togas focused open optimization model for studying cost efficient design and operation of future urban energy system. The model is able to distinguish the benefits of different configurations of power-togas by modelling several energy vectors, including electricity, heating, and cooling alongside with different plant components. The usefulness of the built multi-vector model is illustrated by a case study where the benefits of power-togas are studied in the context of a medium-sized Nordic city. The results show that the city is able to reach carbon neutrality with the help of power-togas. Power-togas provides cost savings by reducing the need of heat storages and transmission capacity. The savings are greatest when the emission reduction goal is high and transmission capacity expansion is expensive. Direct air capture appears as the superior carbon dioxide source when compared to post combustion capture from flue gases due to costs and annual availability. The case study shows no economic benefit for distributed power-to-gas.
... Considerable electricity consumption needed to split water in WE leads to a substantial operating expense in the entire system [32]. Furthermore, recent studies have indicated that the installation cost of WE systems in addition to electricity usage accounts for a large share of the total expenditure [33,34]. Besides the WE system, the share of methanation reactor system, which is another great portion of the whole system, has also been estimated based on historical scale information, as reported by Böhm et al. [35]. ...
Article
Synthetic natural gas (SNG) production from captured CO2 and H2 produced by water electrolysis using renewable energy is of increasing interest for low-carbon fuel production, CO2 utilization technology, and unstable renewable energy storage. In this study, the effect of voltage degradation in a water electrolyzer, a core technology for SNG production, on the unit production cost of SNG production and CO2 emissions, with different water electrolysis types such as alkaline electrolysis (AEL), proton exchange membrane electrolysis (PEMEL), and solid oxide electrolysis (SOEL), was identified through techno-economic and environmental assessment. In particular, the energy efficiency, unit production cost of SNG, and CO2 emissions were identified based on the change in the power consumption caused by voltage degradation. Moderate voltage loss results in a decrease in energy efficiency from 53.8% to 48.8% in AEL, 55.3% to 47.0% in PEMEL, and 76.3% to 51.2% in SOEL. Moreover, respective SNG unit production costs of 140.3–170.2 USD MWh⁻¹, 157.5–203.1 USD MWh⁻¹, and 153.1–353.5 USD MWh⁻¹ for AEL, PEMEL, and SOEL, respectively, were obtained, showing an increase in SNG production cost due to the voltage degradation. Furthermore, total CO2 emissions for the SNG production process were investigated considering voltage degradation as well as electricity generation sources.
... To the best of the authors' knowledge, there is no research covering the scope of nationwide deployment on renewable electricity generation which extended with Power-to-X till-date. Such a deployment strategy has been proven with the potentiality on improving renewable energy penetration in a cost-effective scheme [31]. Nonetheless, such a deployment strategy could be a great enhancement approach on reducing the environmental impact in a defined system. ...
Article
The urge to increase renewable energy penetration into the power supply mix has been frequently highlighted in response to climate change. South Korea was analyzed as a case study for which the government has shown motivation to increase renewable energy penetration. Herein, a hybrid renewable energy system (HRES) including solar and wind energies were selected due to their relatively stable and mature technology. In addition, Power-to-X has been incorporated to cover other renewable energy options such as hydrogen and synthetic natural gas (SNG). Therefore, an approach of forecasting the weather characteristics and demand loading over a relatively long timeframe was implemented via deep learning techniques (LSTM and GRU) and statistical approaches (Fbprophet and SARIMA), respectively. A deployment strategy incorporating HRES and Power-to-X is then proposed in correspondence to the forecasted results of the 15 regions considered in this study. An extension of this, the reliability of the designed system is further assessed based on the probability of the demand losses with the aid of Monte-Carlo simulation. With the proposed deployment strategy, a total annual cost of 9.88 × 1011 /yearandagreenhousegasreductionof1.24×106tons/yearareexpectedfora35/year and a greenhouse gas reduction of 1.24 × 106 tons/year are expected for a 35% renewable energy penetration. However, only SNG shows relatively competitive cost (at 23.20 /m3 SNG), whereas the average costs of electricity (0.133 /kWh)andhydrogen(7.784/kWh) and hydrogen (7.784 /kg H2) across the regions are yet to be competitive compared to the current market prices. Nonetheless, the priority of deployment across regions has been identified via TOPSIS.
Article
Full-text available
E-fuels represent a crucial technology for transitioning to fossil-free energy systems, driven by the need to eliminate dependence on fossil fuels, which are major environmental pollutants. This study investigates the production of carbon-neutral synthetic fuels, focusing on e-hydrogen (e-H2) generated from water electrolysis using renewable electricity and carbon dioxide (CO2) captured from industrial sites or the air (CCUS, DAC). E-H2 can be converted into various e-fuels (e-methane, e-methanol, e-DME/OME, e-diesel/kerosene/gasoline) or combined with nitrogen to produce e-ammonia. These e-fuels serve as efficient energy carriers that can be stored, transported, and utilized across different energy sectors, including transportation and industry. The first objective is to establish a clear framework encompassing the required feedstocks and production technologies, such as water electrolysis, carbon capture, and nitrogen production techniques, followed by an analysis of e-fuel synthesis technologies. The second objective is to evaluate these technologies’ technological maturity and sustainability, comparing energy conversion efficiency and greenhouse gas emissions with their electric counterparts. The sustainability of e-fuels hinges on using renewable electricity. Challenges and future prospects of an energy system based on e-fuels are discussed, aiming to inform the debate on e-fuels’ role in reducing fossil fuel dependency.
Article
Full-text available
Urbanisasi dan perkembangan kota yang cepat, diiringi dengan permintaan pemenuhan infrastruktur perkotaan yang meningkat. Dalam upaya pemenuhan infrastruktur perkotaan, mayoritas masih menggunakan infrastruktur energi tak terbarukan. Hal tersebut mendorong munculnya berbagai dampak dari perubahan iklim. Dalam mengatasi kondisi tersebut terdapat inovasi pemenuhan infrastruktur dengan energi terbarukan. Penelitian ini bertujuan untuk menganalisis secara bibliometrik bagaimana perkembangan dan apa saja topik paling sering dibahas terkait pemanfaatan energi terbarukan dalam infrastruktur perkotaan. Studi bibiliometrik dilakukan dengan pengumpulan data base artikel ilmiah dan analisis menggunakan VOSViewer. Hasil studi bibliometric menunjukkan bahwa pemanfaatan energi terbarukan pada infrastruktur perkotaan paling banyak tercatat berasal dari Asia dan Afrika dengan topik popular adalah infrastruktur dan sistem, pembangunan perkotaan, pemanfaatan energi, dan kajian bangunan berkaitan dengan implementasi dari pembangunan infrastruktur. Selain itu, hasil penenlitian juga membahas topik bagaimana integrasi adanya infrastruktur dengan pemanfaatan energi terbarukan, pengembangan infrastruktur perkotaan memanfaatkan energi terbarukan dengan konsep smart city, kapasitas dan skema penyediaan infrastruktur perkotaan dengan energi terbarukan dan mengenai kebijakan penyediaannya.
Chapter
The development of renewable energy infrastructure and technologies is accelerating. One of the main concerns in renewable electricity production is the emergence of generation intermittency and fluctuation along with existing load variability. Power-to-X could play a critical role in providing many technological methods to handle power supplies with the consistency and reliability of future energy systems. A comprehensive investigation of the various power-to-X technologies is provided in this chapter, which could be utilized to integrate the benefits of renewable energies whereas avoiding the limitations when used alone. As well, the latest advances in PtX technologies are investigated and discussed in detail since limitations must be overcome to implement infrastructures around the world.KeywordsRenewable energyElectricity productionPower-to-XPower suppliesPower-to-gasGreenhouse gas emissionsFuture energy supplyHydrogen productionCarbon-neutral fuelsGreen fuelsAlkaline electrolysisWater electrolysisPolymer electrolyte membraneSolid oxide electrolysisPower-to-methanePower-to-hydrogenCatalytic methanationBiological methanationPower-to-liquid
Article
Green hydrogen production is expected to have a major contribution in addressing the global challenge of energy transition and economy decarbonization. In such a transition, wind energy is considered as one of the principal electricity sources for H2 production, both because it is a sustainable source and owing to the intermittency of the wind resource. In recent years, new wind farms have gradually moved offshore, due to better wind resource quality and due to limited space onshore. However, a mismatch between instantaneous wind energy availability and electricity demand often leads to wasting some of the wind resource, usually referred to as curtailment events. Such an excess energy could be used to produce hydrogen and thus make efficient and integrated use of the available equipment and resources. The present work analyzes the feasibility of hydrogen production employing electricity generated from wind energy, taking the WindFloat Atlantic offshore wind farm and Portugal’s electricity market as a case-study. Two scenarios are considered. Scenario 1 assumes the WindFloat Atlantic wind farm’s present capacity of 25.2 MW and scenario 2 considers a long-term commercial phase of 150 MW integrated in a developed hydrogen economy with pipelines for H2 distribution. In both scenarios a readily available PEM electrolyzer system is employed and the benefits of complementary oxygen sales are estimated. The availability of the wind resource and occurrence of different wind conditions for the particular location is estimated from the wind energy atlas. Afterwards, correlations between the renewable energy production and wholesale electricity price in the Iberian market are established by processing the data corresponding to the year 2019 and taking seasonal variations into account. For each of scenarios, two cases are considered. Case A assumes hydrogen is produced only at night whereas Case B allows for production both during nights and afternoons. Results show Case B and oxygen sales contribute to a more economically feasible project. For Case B and assuming a H2 selling price of 8 €/kg, discount rate (10%) and corporate tax of 21%, results show scenario 2 is the only profitable solution, due to the long-term lower costs. Scenario 1 appears to be feasible only with government incentives. The ratio between the hydrogen plant power and wind farm capacity (PPR) has a significant impact on the H2 production, with results showing a minimum in H2 cost for a ratio of approximately 30%.
Article
The present paper analyzes an innovative energy system based on a hydrogen station, as the core of a smart energy production center, where the produced hydrogen is then used in different hydrogen technologies adopted and installed nearby the station. A case study analysis has been proposed and then investigated, with a station capacity of up to 360 kg of hydrogen daily generated, located close to a University Campus. A hydrogen mobility network has been included, composed of a fuel cell hydrogen fleet of 41 vehicles, 43 bicycles, and 28 fuel cell forklifts. The innovative proposed energy system needs to meet also a power and heat demand for a student housing 5400 m² building of the University Campus. The performance of the system is presented and investigated, including technical and economic analyses, proposing a hydrogen refueling station as an innovative alternative fuel infrastructure, called Multi-modular Hydrogen Energy Station, marking its great potential in future energy scenarios.
Article
Full-text available
The Power-to-Gas strategy has become a mainstream topic for decarbonization and development of renewables and flexibility in energy systems. One of the key arguments for decarbonizing the gas network is to take advantage of existing network infrastructure, gradually transitioning to lower fossil carbon sources of methane from Power-to-Gas. This work proposes the techno-economic investigation of an integrated system considering an advanced CO2 capture process, in terms of solvent and process configuration, to treat about 10% of a cement plant’s flue gas and convert the captured CO2 into synthetic natural gas using renewable hydrogen generated from a large-scale wind powered electrolyzer. An optimized heat recovery system is proposed, drastically decreasing the external hot utility demand of the CO2 capture unit. In addition, it leads to the production of complementary electricity (about 1.06 MW), reducing thus also the electrical demand of the integrated process. The synthetic natural gas produced has a composition (CH4 92.9 mol.%, CO2 3.7 mol.%, and H2 3.4 mol.%) and a Wobbe index (46.72 MJ/m3), corresponding to specification for gas grid injection at 50 bar in Germany. With an overall system efficiency of 72.6%, the process produces 0.40 ton synthetic natural gas per ton of captured CO2. The cost of the synthetic natural gas produced is higher when compared to the present natural gas market price, but cost reductions and possible commercial use of coproducts like oxygen, represent a likely alternative. Costs are mainly driven by high capital investments (the electrolyzer), and the price of renewable electricity, which is expected to decrease in the coming years.
Article
Full-text available
Optimization tool is developed for dimensioning Power-toGas components. • Detailed Power-toGas cost analyses are made for different operational environments. • 6-17% reduction in gas production costs was achieved via component dimensioning. • Sensitivity analyses show impacts of key parameters on plant operation. • Optimal configurations are highly dependent on the electricity source being used. A B S T R A C T Power-toGas technologies offer a promising approach for converting renewable electricity into a molecular form (fuel) to serve the energy demands of non-electric energy applications in all end-use sectors. The technologies have been broadly developed and are at the edge of a mass roll-out. The barriers that Power-toGas faces are no longer technical, but are, foremost, regulatory, and economic. This study focuses on a Power-toGas pathway, where electricity is first converted in a water electrolyzer into hydrogen, which is then synthetized with carbon dioxide to produce synthetic natural gas. A key aspect of this pathway is that an intermittent electricity supply could be used, which could reduce the amount of electricity curtailment from renewable energy generation. Interim storages would then be necessary to decouple the synthesized part from hydrogen production, to enable (I) longer continuous operation cycles for the methanation reactor, and (II) increased annual full-load hours, leading to an overall reduction in gas production costs. This work optimizes a Power-toGas plant configuration with respect to the cost benefits using a Monte Carlo-based simulation tool. The results indicate potential cost reductions of up to 17% in synthetic natural gas production by implementing well-balanced components and interim storages. This study also evaluates three different power sources which differ greatly in their optimal system configuration. Results from time-resolved simulations and sensitivity analyses for different plant designs and electricity sources are discussed with respect to technical and economic implications, so as to facilitate a plant design process for decision makers.
Article
Full-text available
The publication gives an overview of the production costs of synthetic methane in a Power-toGas process. The production costs depend in particularly on the electricity price and the full load hours of the plant subsystems electrolysis and methanation. The full-load hours of electrolysis are given by the electricity supply concept. In order to increase the full-load hours of methanation, the size of the intermediate hydrogen storage tank and the size of the methanation are optimised on the basis of the availability of hydrogen. The calculation of the production costs for synthetic methane are done with economics for 2030 and 2050 and the expenditures are calculated for one year of operation. The sources of volume of purchased electricity are the short-term market, long-term contracts, direct-coupled renewable energy sources or seasonal use of surpluses. Gas sales are either traded on the short-term market or guaranteed by long-term contracts. The calculations show, that an intermediate storage tank for hydrogen, adjustment of the methanation size and operating electrolysis and metha-nation separately, increase the workload of the subsystem methanation. The gas production costs can be significantly reduced. With the future expected development of capital expenditures, operational expenditure, electricity prices, gas costs and efficiencies, an economic production of synthetic natural gas for the years 2030, especially for 2050, is feasible. The results show that Power-toGas is an option for long-term, large-scale seasonal storage of renewable energy. Especially the cases with high operating hours for the subsystem metha-nation and low electricity prices show gas production costs below the expected market prices for synthetic gas and biogas.
Article
Full-text available
Numerous reviews on hydrogen storage have previously been published. However, most of these reviews deal either exclusively with storage materials or the global hydrogen economy. This paper presents a review of hydrogen storage systems that are relevant for mobility applications. The ideal storage medium should allow high volumetric and gravimetric energy densities, quick uptake and release of fuel, operation at room temperatures and atmospheric pressure, safe use, and balanced cost-effectiveness. All current hydrogen storage technologies have significant drawbacks, including complex thermal management systems, boil-off, poor efficiency, expensive catalysts, stability issues, slow response rates, high operating pressures, low energy densities, and risks of violent and uncontrolled spontaneous reactions. While not perfect, the current leading industry standard of compressed hydrogen offers a functional solution and demonstrates a storage option for mobility compared to other technologies.
Article
Full-text available
The renewed concern for the care of the environment has led to lower emissions of greenhouse gases without sacrificing modern comforts. Widespread proposal focuses on energy produced from renewable sources and its subsequent storage and transportation based on hydrogen. Currently, this gas applies to the chemical industry and its production is based on fossil fuels. The introduction of this energy vector requires the development of environmental-friendly methods for obtaining it. In this paper, existing techniques are just presented and the main focus is made on electrolysis, a mature procedure. In turn, some developed proposals as previous steps to the hydrogen economy are presented. Finally, some lines of research to improve alkaline electrolysis technology are commented.
Article
Full-text available
The paper aims at analysing the energetic performances of Organic Rankine Cycles (ORCs) for the exploitation of low temperature heat sources. Specifically, the attention has been focused on low-enthalpy geothermal energy for small-scale applications. To this purpose a thermodynamic model has been developed and a parametric investigation has been performed considering different organic fluids (isobutane, isopentane, and R245ca). Saturated conditions at the expander inlet have been adopted and the effect of the internal regenerator on the system performances has been evaluated.
Article
Full-text available
Alkaline water electrolysis (AWE) is a mature hydrogen production technology and there exists a range of economic assessments for available technologies. For advanced AWEs, which may be based on novel polymer-based membrane concepts, it is of prime importance that development comes along with new configurations and technical and economic key process parameters for AWE which might be of interest for further economic assessments. This paper presents an advanced AWE technology referring to 3 different sites in Europe (Germany, Austria, Spain). The focus is on financial metrics, the projection of key performance parameters of advanced AWEs, and further financial and tax parameters. For financial analysis from an investor’s (business) perspective, a comprehensive assessment of a technology not only comprises cost analysis but also further financial analysis quantifying attractiveness and supply/market flexibility. Therefore, based on Cash Flow (CF) analysis, a comprehensible set of metrics may comprise Levelised Cost of Energy or, respectively, Levelised Cost of Hydrogen (LCH) for cost assessment, Net Present Value (NPV) for attractiveness analysis and Variable Cost (VC) for analysis of market flexibility. The German AWE site turns out to perform best in all three financial metrics (LCH, NPV, VC). Though there are slight differences in investment cost and operation and maintenance cost projections for the three sites, the major cost impact is due to the electricity cost. Although investment cost is slightly and labour cost is significantly lower in Spain, the difference can’t outweigh the higher electricity cost compared to Germany. Given the assumption that the electrolysis operators are customers directly and actively participating in power markets, and based on the regulatory framework in the three countries, in this special case electricity cost in Germany is lowest. However, as electricity cost is profoundly influenced by political decisions as well as the implementation of economic instruments for transforming electricity systems toward sustainability, it is hardly possible to further improve electricity price forecasts.
Article
Full-text available
Blending hydrogen into existing natural gas pipelines has been proposed as a means of increasing the output of renewable energy systems such as large wind farms. X80 pipeline steel is commonly used for transporting natural gas and such steel is subjected to concurrent hydrogen invasion with mechanical loading while being exposed to hydrogen containing environments directly, resulting in hydrogen embrittlement (HE). In accordance with American Society for Testing and Materials (ASTM) standards, the mechanical properties of X80 pipeline steel have been tested in natural gas/hydrogen mixtures with 0, 5.0, 10.0, 20.0 and 50.0vol% hydrogen at the pressure of 12 MPa. Results indicate that X80 pipeline steel is susceptible to hydrogen-induced embrittlement in natural gas/hydrogen mixtures and the HE susceptibility increases with the hydrogen partial pressure. Additionally, the HE susceptibility depends on the textured microstructure caused by hot rolling, especially for the notch specimen. The design calculation by the measured fatigue data reveals that the fatigue life of the X80 steel pipeline is dramatically degraded by the added hydrogen.
Article
Full-text available
The Power-to-Gas (PtG) process chain could play a significant role in the future energy system. Renewable electric energy can be transformed into storable methane via electrolysis and subsequent methanation. This article compares the available electrolysis and methanation technologies with respect to the stringent requirements of the PtG chain such as low CAPEX, high efficiency, and high flexibility. Three water electrolysis technologies are considered: alkaline electrolysis, PEM electrolysis, and solid oxide electrolysis. Alkaline electrolysis is currently the cheapest technology; however, in the future PEM electrolysis could be better suited for the PtG process chain. Solid oxide electrolysis could also be an option in future, especially if heat sources are available. Several different reactor concepts can be used for the methanation reaction. For catalytic methanation, typically fixed-bed reactors are used; however, novel reactor concepts such as three-phase methanation and micro reactors are currently under development. Another approach is the biochemical conversion. The bioprocess takes place in aqueous solutions and close to ambient temperatures. Finally, the whole process chain is discussed. Critical aspects of the PtG process are the availability of CO2 sources, the dynamic behaviour of the individual process steps, and especially the economics as well as the efficiency.
Article
Full-text available
Reliquefaction technologies are being currently applied on board liquefied natural gas (LNG) carriers on the basis of economic criteria and energy efficiency. A variety of reliquefaction techniques have been developed so far during the last decade. Nevertheless, technology enhancement continues being a research area of interest. In this article the different technologies applied to the reliquefaction of the boil-off gas (BOG) on LNG carriers have been described, analysed and discussed, contributing to highlight the process and operation characteristics as well as selection plant criteria. Finally, a comparison of the different reliquefaction plants, considering their capacities and efficiencies as well as other technical data of interest has been carried out.
Article
Full-text available
With the help of the typical model of a water electrolysis hydrogen production system, which mainly includes the electrolysis cell, separator, and heat exchangers, three expressions of the system efficiency in literature are compared and evaluated, from which one reasonable expression of the efficiency is chosen and directly used to analyze the performance of a water electrolysis hydrogen production system under different operation conditions. Several new configurations of a water electrolysis system are put forward and the problem how to calculate the efficiencies of these configurations is solved. Moreover, a solid oxide steam electrolyzer system (SOSES) for hydrogen production is taken as an example to expound that the different configurations of a water electrolysis system should be adopted for different operation conditions. The results obtained here may provide some guidance for the optimum design and operation of water electrolysis systems for hydrogen production.
Article
Full-text available
The development of a new two-constant equation of state in which the attractive pressure term of the semiempirical van der Waals equation has been modified is outlined. Examples of the use of the equation for predicting the vapor pressure and volumetric behavior of single-component systems, and the phase behavior and volumetric behavior of binary, ternary, and multicomponent systems are given. The proposed equation combines simplicity and accuracy. It performs as well as or better than the Soave-Redlich-Kwong equation in all cases tested and shows its greatest advantages in the prediction of liquid phase densities.
Article
Full-text available
To avoid fossil-fuel consumption and greenhouse-gas emissions, hydrogen should be produced by renewable energy resources. Water electrolysis using proton exchange membrane (PEM) is considered a promising hydrogen-production method, although the cost of the hydrogen from PEM would be very high compared with that from other mature technologies, such as steam methane reforming (SMR). In this study, we focus on the effective utilization of by-product oxygen from electrolysis hydrogen production and discuss the potential demand for it, as well as evaluating its contribution to improving process efficiency. Taking as an example the utilization of by-product oxygen for medical use, we compare the relative costs of hydrogen production by means of PEM electrolysis and SMR.
Article
Hydrogen facilities are worldwide recognized as decarbonizing energy systems, but strategic actions are needed by intensifying the effort on the feasibility studies concerning the integration of multiple hydrogen systems, to foster and accelerate the achievement of the break-even points. The present paper proposes a comprehensive technical-economical assessment of PEM hydrogen production system via water electrolysis, in three different Southern Italian locations powered by grid electricity and renewable energies, namely wind, solar, geothermal. Hydrogen is then stored in gaseous form at 350 bar. The generated hydrogen in each facility is used to meet two different end-users needs: hydrogen mobility and hydrogen injections in the natural gas grid/pipelines. Hydrogen-to-mobility serves fuel cell electric vehicles, requiring high-pressure delivery and dispensing up to 700 bar, while for hydrogen injections, a double-stage pressure reducer is considered, by stepping down the pressure level at 50 bar. The financial investigation has been based on two main sensitive analysis: a power-purchase agreement price ranging from 50 to 100 €/MWh, and several scenarios for the hydrogen end-users, by ranging the potential hydrogen delivery from 25 to 100% of the daily production for the Hydrogen Mobility. As a novelty, the present paper integrates an emission analysis, in order to take into account the carbon footprint of these innovative applications and their benefits related to health and quality of life in terms of economic repercussions on society.
Article
Embrittlement of steel due to its exposure to hydrogen is a well-established phenomenon, which diminishes its ductility and toughness. However, there is limited research on how hydrogen, which evolves from the corrosion process, affects the yield strength of mild steel in the long-term. This paper presents the results obtained from a long-term investigation on hydrogen evolving from a corrosion reaction, which causes embrittlement of mild steel. Both mechanical tests and microstructural analyses on corroded steel specimens are performed at three different intervals for one year. Time-dependent relations for predicting the corrosion rate and its subsequent hydrogen release were derived by analysing the test results. Moreover, relations for predicting the change in yield strength as a function of hydrogen content, corrosion rate and compositional element change were developed, along with one single equation considering all these factors. Furthermore, fractography analysis was performed to observe HE effect and reasons for the decline in yield strength. The analysis revealed hydrogen induced micro cracks, micro pores, intergranular cracks, grains deformation and hydrogen blisters.
Article
The paper proposes an innovative scheme exploiting oxygen liquefaction as a means for storing excess electricity generation from renewable sources. Liquid oxygen is then used in an oxy-combustion process with LNG to generate electricity when renewable energy generation is below the demand. An equivalent round trip efficiency is defined to make it possible comparing the system performances with hybrid plants including conventional generation and storage. The proposed scheme exhibits very high equivalent round trip efficiency, giving the system operators the opportunity to integrate more and more renewable energy generation inside power systems. Liquefied carbon dioxide and water are byproducts of the process. The size of the plant and of the storage tanks needed for a 4 TWh yearly demand with a peak around 800 MW is compatible with state-of-the-art systems used for LNG storage in similar size gas power plants.
Article
The gradual reduction of subsidies for electricity production from biogas and the raising interest of bio-methane as an integration to natural gas market force the biogas plant owners to choose alternative solutions for biogas exploitation. In this study, two solutions for biomethane distribution have been compared: biomethane liquefaction and grid injection. The analysis was carried out as a function of gas connection cost, electric tariff, selling price and type of expander adopted in the liquefaction cycle (radial turbines or screw expanders). A nitrogen Joule-Brayton reverse cycle was considered for liquefaction. A detailed model of the cycle was developed in Aspen Hysys and optimized to minimize the energy specific consumption. Results show that expander efficiency has a key role in the liquefaction scenario. Screw expanders lead to a specific consumption 1.45 times higher than radial turbines but reduce capital costs by a factor of 1.39. Biomethane grid injection is the preferable solution in terms of investment risk if the connection cost is below 500 k,independentlyontheelectricityprice.Asfarasitconcernstheprofit,liquefactionwithradialturbinesispreferableuptoelectricitypriceof0.23, independently on the electricity price. As far as it concerns the profit, liquefaction with radial turbines is preferable up to electricity price of 0.23 /kWh. A sensitivity analysis on product selling prices shows that biomethane grid injection is always the most profitable solution when connection costs are low. For higher connections cost, liquefaction with radial turbines is the best solution for minimizing the investment risk and maximizing the profit for most of the combination of selling prices.
Article
Heat inleak through insulation in the storage tanks produces boil-off gas (BOG) in LNG-carrying ships. Reverse Brayton cycle (RBC) with nitrogen is often chosen as the refrigeration cycle to reliquefy BOG to prevent loss of valuable gas and environmental pollution. In this paper, parametric evaluations of a basic RBC-based reliquefaction system are done based on exergy analysis. The analyses revealed that formation of liquid at turbine exit and close minimum temperature approach/temperature pinch in the BOG condenser plateaus out the improvement of performance of the RBC based reliquefaction system. The specification of equipment and operating parameters are determined to derive the highest savings in terms of power consumption and recovery of BOG. If RBC is operated in the range of 10–50 bara, close to 93% of BOG is reliquefied. Total reliquefaction is possible only if the RBC is designed with compressor suction at 4 bara. However, it increases the sizes of pipelines, compressor and heat exchangers. All parameters are non-dimensionalized to facilitate application of the results to any capacity of LNG-carrying ship. Part 2 of this paper presents the analyses on thermodynamically improved configurations of reliquefaction systems.
Article
Performance of an innovative storage system for renewable energy, based on the Power-to-Gas concept are numerically predicted. The investigated system is composed by a high temperature co-electrolyzer of Solid Oxide Electrolyte Cell technology and an experimental methanation section, based on structured catalyst, suitable for high temperature operation. With the aim to thermally integrate high temperature co-electrolysis and methanation, a parametric thermodynamic analysis of the Power-to-Gas system is carried-out with a lumped-parameters approach, including all the thermal and electric energy consumptions. In particular, in order to optimize the system thermal balance of plant, various configurations involving internal heat recovery and pressurization of components are also considered. Numerical results are provided in terms of different performance indicators, such as electric-to-fuel conversion index, first law efficiency and second law efficiency and output-fuel quality indicators. The study demonstrates the possibility to thermally integrate the co-electrolyzer and the high-temperature methanation section achieving significant energy savings. Moreover, the calculated results show that the system set-up providing higher quality of the produced synthetic natural gas do not always lead to larger values in energy conversion efficiency. Eventually, advanced configurations of the Power-to-Gas system including heat recovery allow to achieve first-law efficiency up to values around 80–85% and second-law efficiency around 70–78%; a second methanation section based on conventional low-temperature reactors is included in the system and pressurization of the methanation section, or pressurization of the co-electrolysis section, is mandatory, in order to achieve large fraction of methane (up to 95–99%) in the produced synthetic fuel.
Article
Several plant concepts for synthetic compressed natural gas (CNG) and liquefied natural gas (LNG) production using different water electrolysis and methanation technologies are compared in terms of power-to-methane efficiency, cooling water requirements, net water requirements, and carbon valorization. In these concepts, both oxygen and hydrogen produced in the electrolysis unit are valorized. Pure oxygen is used in the gasification unit, which allows a compact autothermal unit design and an efficient syngas production. Electrolytic hydrogen is fed to the catalytic methanation unit, thus improving the carbon utilization compared to state of the art plants with water-gas shift units. Pinch analyses were performed using an in-house MATLAB® algorithm to evaluate the thermal requirements of each plant concept and determine the maximal theoretical plant efficiencies. Plant efficiencies were then evaluated more accurately in static regime using full integrated Simulink® plant models. Calculated efficiency values are very close to the maximal theoretical ones, which validates the relevance of the implemented thermal integrations from an energy standpoint. Investigated plant concepts with solid oxide electrolysis (SOE) units present a significantly higher overall efficiency (in the range of 78.5–81.8% higher heating value (HHV) according to the end-products) compared to the reference case with liquid water electrolysis units (64.9% HHV for synthetic natural gas (SNG) or 64.4% HHV for CNG), thus highlighting the potential of the solid oxide electrolysis cell (SOEC) technology for power-to-gas/liquids applications. The plant efficiency values are then verified, discussed, and compared with previous literature values. The techno-economic feasibility of several options for residual heat valorization is then discussed, e.g. power production or coupling with a district heating network.
Article
FULL TEST AVAILABLE UP TO February 15th AT: https://lnkd.in/gecDvNr The development of Hybrid Renewable Energy Systems (HRES) under the Distributed Generation (DG) paradigm is the support for substantial reduction of CO2 emissions and for greater penetration of renewable energy sources. The performance and reliability of HRES depend on the interaction between demand, generation, storage and the energy management strategy. In this study a comparison between two different control strategies is presented. In particular, a Rule Based Control (RBC) strategy has been compared with a more sophisticated Model Predictive Control (MPC) for the management of an HRES for residential applications. Results show that a HRES operating in a connected mode has potential to support grid balancing actions giving economic benefits for both end-users and providers. Moreover, the MPC strategy gives a potential reduction of the unbalanced energy exchange with the grid and a more efficient use of the HRES components. The MPC strategy allows thus for a more effective use of renewable sources if compared with a conventional RBC for a Microgrid of same size, thus allowing for a greater penetration of renewable sources into the energy mix, or equivalently, toward downsizing of storage and programmable source subsystems with economic benefits.
Article
The increasing penetration of renewable energy sources in the electricity generation scenario forces to face new challenges to achieve an effective management of the power system both in technical and economic terms. Traditional energy storage solutions, like electrochemical cells and pumped hydro energy storage appear critical in terms of economic sustainability and site-dependency. The use of compressed air as energy storage has been investigated since the 20th century, but, in its first configuration, it was affected by site constraints as pumped hydro plants do. Liquid air energy storage has the chance to overcome those limits, but the experimental studies have far reached low efficiency. However, by rising the highest cycle temperature with the addiction of fossil fuel energy, these results can be largely improved. The paper deals with the thermodynamic analysis of a hybrid system including energy storage and production based on a liquid air energy storage plant where only oxygen is liquefied, while liquefied natural gas is used as fuel. In the production phase, liquefied oxygen and natural gas react in an oxy-combustion chamber where a large amount of water is added to keep the temperature at an acceptable level by evaporation. The system does not require an external water supply since all the water needed is produced by the cycle itself, allowing the plant to be placed also in remote areas with poor water resources. At the beginning of the cycle, both the reagents are liquid at very low temperature (below −150 °C) and they need heat to be gasified; a large amount of this heat can be recovered from the combustion products, which, being cooled at suitable pressure, release liquid carbon dioxide which can thus be easily separated. Optimized arrangements, compared to the performances of the best available hybrid peak plants, even with sufficiently conservative hypotheses, reach high equivalent round trip efficiencies, even higher than 90%.
Article
In this paper, a comparison of two different small bio-LNG plants for upgrading and liquefaction have been conducted. In the first configuration liquefaction of the biomethane occurred after the upgrading with conventional processes; in the second configuration, cryogenic upgrading occurred within the liquefaction process, removing CO2 in solid state. For both the two configurations, a two-pressure levels Joule-Brayton reverse cycle, with nitrogen as working fluid, has been considered as refrigeration cycle. The two systems have been simulated and optimized in ASPEN HYSYS, determining the values of the various working parameters which minimized the energy specific consumption. Results showed that a bio-LNG plant with cryogenic upgrading did not require any pre-treatment of raw biogas and reached a very promising energy consumption: 0.61 kWh/Stm³ of raw biogas processed, equivalent to 1.45 kWh/kg of bio-LNG produced. Bio-LNG plants with standard upgrading techniques required between 0.57 and 0.72 kWh/Stm³ without considering additions for heating and raw biogas pre-treatment. A sensitivity analysis concerning CH4 content in bio-LNG and intercooling temperature has been accomplished for bio-LNG plants with cryogenic upgrading, proving their impact in specific energy consumption. A standalone bio-LNG plant cryogenic upgrading, with a natural gas internal combustion engine for energy supply, has been studied and briefly discussed. Some solutions for waste heat utilization have been proposed (digesters warming, energy recovery).
Article
Converting CO2-rich waste streams such as raw biogas, landfill gas and power plant flue gas into synthetic fuels and chemicals will reduce greenhouse gas emissions, providing revenue at the same time. One option is to convert CO2 into CH4 by hydrogenation via Sabatier reaction. This synthetic methane will be renewable if the H2 required for the reaction is generated via water electrolysis using solar and wind energy or hydroelectricity. However, to realize the potential of this approach, a number of technological challenges related to the Sabatier reactor design have to be resolved, including thermal management. The high exothermicity of the Sabatier reaction can lead to reactor overheating. High temperatures are unfavorable to the exothermic and reversible methanation process, resulting in low CO2 conversions. A simulation-based study of a Sabatier reactor was performed in order to optimize the removal of heat, while maximizing CO2 conversion and CH4 production. The heat-exchanger type packed bed reactor with internal cooling by a molten salt was simulated using a transient, pseudo-homogeneous mathematical model. Reactor performance was evaluated in terms of CO2 conversion and CH4 yield. The simulation results show that feed temperature, feed flow rate, and molten salt flow rate are the crucial parameters affecting the reactor performance. For the optimized operating conditions, the model predicts CO2 conversions and CH4 yields above 90% at high reactor throughputs, with space velocities up to 10,000 h⁻¹. A preliminary techno-economic evaluation is provided: opportunities and challenges are outlined.
Article
Power-to-Methane is a concept that converts electrical into chemical energy using CO2 and H2O. The concept brings the possibility of connecting the power grid to different sectors, where CH4 is needed such as mobility and industry. In this review, a comprehensive overview of the state-of-the-art of Power-to-Methane is presented. The Power-to-Methane process chain is described in detail. Fundamentals of water electrolysis are highlighted and cell technologies are discussed and assessed. CO2 sources are pointed out, CO2 separation technologies are depicted and compared, and some separation projects worldwide are listed. Thermodynamics of methanation process is analyzed; catalysts and reactors used are descripted and evaluated. Finally, Power-to-Methane plants in operation and construction are addressed.
Article
The enhanced bubble detachment in water electrolysis due to Lorentz-forces is discussed for the case of mainly parallel electric and magnetic fields. Experiments and numerical simulations were carried out to assess the velocity and pressure distribution around single rigid spheres mimicking electrolytic bubbles on a horizontal electrode in the presence of a vertical magnetic field. Astigmatism particle tracking velocimetry delivered the three-dimensional flow field and a finite volume method was used for the computations. Formerly it was assumed that the flow-induced pressure decrease at the bubble's top caused the earlier detachment under magnetic field action. However, the experimental and numerical results obtained here demonstrate that this pressure decrease is too weak as to effectively change the detachment process. Finally, an alternative explanation for the observed bubble behavior is suggested: it might result from the comparatively strong global flow generated by the additive effect of a group of bubbles.
Conference Paper
Hybrid energy systems represent today one optimal solution for different mobility areas. This is shown in the paper by describing three applications. The first one refers to a tramway system: regenerative braking has been enhanced by introducing some stationary storage capability in correspondence of electrical feeding substations. The second one regards the design of a series-hybrid powertrain for a platform of urban buses, in which usage of alternative fuels was also considered. The third one refers on hybridization of a hydraulic skid-loader. The three applications shown that also from economical point of view the proposed solutions can be of great interest since their cost-effectiveness.
Article
The current increase in the deployment of new renewable electricity generation systems is creating new challenges in balancing electric grids. Solutions including energy storage at small and large scales are becoming of paramount importance to guarantee and secure a stable supply of electricity. This paper presents a study about a hybrid solution including a large scale energy storage system coupled with power generation and fast responding energy storage systems. The hybrid plant is able to deliver the energy previously stored by using an air liquefaction process either with or without the contribution of additional energy from combustion. The paper also highlights how such hybrid plants may offer the chance of providing the grid with fast control services.
Article
Hybrid renewable energy (HRE) system based power generation is a cost effective alternative where power grid extensions are expensive. This system utilizes two or more locally available renewable energy resources such as wind, solar, biomass, biogas and small hydro power with or without conventional fossil fuel energy sources to create standalone mode to meet the energy needs in rural remote areas. This study offers a comprehensive review of the research work carried out in planning, configurations, and modeling and optimization techniques of hybrid renewable energy systems for off grid applications. Hybrid renewable system utilities today are more dependent on an optimal design to minimize the cost function. This paper presents a review of various mathematical models proposed by different researchers. These models have been developed based on objective functions, economics and reliability studies involving design parameters. The present study will familiarize the reader with various optimization techniques of system modeling and enable them to compare these models on the basis of their cost functions. Researchers may consider the most suitable model from the various hybrid renewable system models proposed in this study to develop customized designs for optimizing system size while incurring least cost.
Article
In the framework of the transition towards the new paradigm of electricity grids, the exploitation of intrinsic energy storage or deliberately installed storage systems (either thermal or electric) plays a major role in enabling the actual controllability of the various sources and loads connected to the system. Controllability, for different purposes, is the key factor which characterises a Smartgrid compared to a traditional energy system. This paper presents a systematic approach to the services that a storage system is able to provide in an electric power system and shows how such systems can be actually designed and built. In several research projects the University of Pisa installed storage devices for different purposes showing the effectiveness of the contribution they give. This paper also shows how particular loads, which are connected to the grid through a power conditioning device, can provide important ancillary services for the grid.
Article
There are several hydrogen production technologies. They range from the most widely used fossil fuel based systems such as natural gas steam methane reforming to the least used renewable energy based systems such as wind electrolysis. Currently almost all the industrial hydrogen need worldwide is produced using fossil fuels. Electrolytic hydrogen production based on electricity generated from renewable resources and hydrogen's energetic use could contribute to the global need for a sustainable energy supply. However, these technologies are also not free from environmental burdens. A life cycle assessment (LCA) helps to identify such impacts considering the entire life cycle of the process chains. This paper reviews twenty-one studies that address the LCA of hydrogen production technologies, a majority of them employing electrolytic technologies. It has been observed that global warming potential (GWP) is the impact category analyzed by almost all the authors. Acidification potential (AP) ranks second. Other categories such as toxicity potential are often not analyzed. The main environmental concern associated with electrolytic hydrogen production is electricity supply. The GWP contribution of the electrolyzer unit is relatively small (e.g. only about 4% in wind based electrolysis including hydrogen production and storage systems). From an LCA perspective, it can be concluded that electrolysis using wind or hydropower generated electricity is one of the best hydrogen production technologies, compared to those using conventional grid electricity mix or fossil fuel feedstocks.
Article
A low flow rate and short diaphragm life are the two disadvantages of diaphragm compressors when applied in hydrogen refueling stations. A new generatrix of the cavity profile of a diaphragm compressor was developed in this study to increase the cavity volume and decrease the diaphragm radial stress. A reduction in the diaphragm radial stress that resulted from the new design was validated by experiment and numerical simulation. The volumes of the cavities with different generatrices and the radial stress distribution of the diaphragm were investigated under various design conditions. The results indicated that the volume of the cavity with the new generatrix was approximately 10% larger than that with a traditional generatrix at the same allowable stress and cavity radius. At a similar cavity volume and radius, the radial stress values of the diaphragm in the cavity with the new generatrix were low. The decrease rate of the maximal radial stress of the diaphragm in the cavity with the new generatrix reached 13.8%. In the diaphragm centric region, where additional stress was induced by discharge holes, the maximal radial stress decrease rate reached 19.6%.
Article
Perfect compatibility between geothermal plants and the development of the other resources of the territory (tourism, quality agriculture, etc.) is a key issue for the sustainability of the geothermal energy and its acceptance by the communities hosting the plants. Third Millennium geothermal projects are able to win this challenge. Integration in the landscape of power plants and related infrastructures, abatement of the gaseous emission and of the cooling tower drift, reduced noise level, etc., allow the preservation of natural beauties, environmental features and life quality of the people living near the plants. The invention of a proprietary technology (AMIS ®) for the abatement of hydrogen sulphide and mercury emission and its application both to new geothermal plants and to the retrofit of the existing one's is a cornerstone of the New Geothermal Deal in Italy. Hydrogen sulphide is responsible of the bad smell often perceived in the geothermal areas. AMIS ® is an environmentally friendly process because it usually doesn't require the use of chemicals and doesn't produce sulphur based by-products to be landfilled or recycled. At present, three power plants are equipped with AMIS ® systems. The results of two years of commercial operation are outlined.
Article
Electricity grids with a high penetration of fluctuating energy production from wind and solar energy sources bear a risk of electricity over-production. A surplus of renewable energy can arise at times of high production when the energy volume cannot be absorbed by the electricity grid. Furthermore, the control of the stochastic power fluctuations has to be addressed since these will result in changes to grid stability.Producing hydrogen from excess electricity is one approach to solve these problems. This hydrogen can either be sold outside the electricity market, for instance as vehicle fuel, or re-converted into electricity, for instance as a means of controlling wind power output.This paper describes two different wind-hydrogen systems and analyses the ensuing costs of hydrogen per unit of energy service (i.e. kWh and Nm3). If hydrogen is to represent a practical fuel alternative, it has to compete with conventional energy carriers. If this is not possible on strictly (micro-) economic terms, at least a macro-economic calculation, in this case including all external costs of energy services, needs to show competitiveness.
Article
Currently, hydrogen is primarily used in the chemical industry, but in the near future it will become a significant fuel. There are many processes for hydrogen production. This paper reviews the technologies related to hydrogen production from both fossil and renewable biomass resources including reforming (steam, partial oxidation, autothermal, plasma, and aqueous phase) and pyrolysis. In addition, electrolysis and other methods for generating hydrogen from water, hydrogen storage related approaches, and hydrogen purification methods such as desulfurization and water-gas-shift are discussed.
Power: Technology Brief
  • Irena
ASME International Mechanical Engineering Congress and Exposition
  • V Chakravarthy
  • J Weber
  • A Rashad
  • A Acharya
  • D Bonaquist
Monitoraggio delle aree geotermiche. Controllo alle emissioni delle centrali geotermiche
  • Geotermia Arpat Settore
Department of Energy FreedomCAR & Vehicle Technologies Program Advanced Vehicle Testing Activity, Arizona Public Service - Alternative Fuel (Hydrogen) Pilot Plant Design Report
  • D Karner
  • J U S Francfort
Development of a centrifugal hydrogen pipeline gas compressor-Final report. Concepts NREC Technical memorandum n. 1785 prepared for DOE
  • C Osborne
  • F A Di Bella
Market Insider - Business Insider
  • Natural
  • Henry Hub