Excess Renewable Energy Research Articles

Techno-economic analysis of long-duration energy storage and flexible power generation technologies to support high-variable renewable energy grids

Techno-economic analysis of long-duration energy storage and flexible power generation technologies to support high-variable renewable energy grids

Modeling Renewable Electricity Generation for Northern Cyprus (TRNC)

Several researches have been done on modeling renewable energy for different countries and continents, employing unique approaches, strategies and methodologies. This paper aims to do the same by using the sunlight and wind resources to model a hybrid renewable energy system for the Turkish Republic of Northern Cyprus (TRNC). This paper will also carry out a comparative analysis between the modeled renewable energy generation and the present electricity generation in the country. The paper will also depict how the renewable energy relates with the country load, based on the amount of energy generated from renewable resources and the size of battery used to store excess renewable energy generated. This paper will also show how base load power plants do not allow lots of renewable energy penetration, because of the varying nature of wind and solar resources.

Hydrogen farm concept: A Perspective for Turkey

Hydrogen farm concept: A Perspective for Turkey

Self-Supported Solid Oxide Fuel Cells by Multimaterial 3D Printing

Nowadays, renewable energy increases its contribution to the present energy scenario. In this regard, the implementation of energy storage and sources as the electrolysers and fuel cells gives the opportunity to transform the surplus of renewable energy to the form of hydrogen, by water electrolysis and the use of this hydrogen as a fuel for energy generation by the reverse mode of the same devices, in the so-called power to gas and gas to power routes. Among the different technologies of fuel cells and electrolysers, the high temperature technology based on ceramic solid oxides presents the best efficiencies. However, the fabrication of this devices implies several manufacturing procedures and multiple intermediate steps of fabrications, such as tape-casting, screen-printing, annealing, manual stacking, joining, sealing, etc. As a result, the SOC production process becomes more expensive and time-consuming. Recently, it has been demonstrated that the application of additive manufacturing (AM) technologies for functional ceramics fabrication, specially to SOC production, leads to significant improvement of the process. AM represents freedom of design, that allows to enhance the performance of the SOC-based device, an increase of manufacturing speed and productiveness, while the waste material is reduced. As a final result, one-step printed monolithic SOFC stack could be produced combining different AM technologies in a single printing process.For this purpose, hybrid 3D printing technology which combines stereolithography (SLA) and robocasting (direct ink writing, DIW) has been developed. Thus, the technique uses 8YSZ for the electrolyte fabrication by SLA and deposition of electrodes and interconnectors by DIW. The elaborated hybrid multimaterial 3D printing technology renders possible complete SOC stack fabrication as a single-step process. Complete fully printed SOFC cells, their co-sintering process and their characterization are here presented while the advantages and limitations of the fabrication process are discussed.

Hydrogen for Maritime Application—Quality of Hydrogen Generated Onboard Ship by Electrolysis of Purified Seawater

Maritime transport is investigating several options to reduce its greenhouse gases and air pollutant emissions. An experimental ship, Energy Observer, is using excess renewable energy to generate onboard hydrogen by electrolysis of purified seawater. As a promising option for storing energy, it can provide on-demand energy to the ship through a hydrogen fuel cell (FC). As hydrogen FCs lifetime and performance are correlated to hydrogen quality, the hydrogen produced onboard needs to be monitored. This study assesses the probability of contaminants presence for this electrolyser, using purified seawater and supports the results with a hydrogen fuel quality analysis from the Energy Observer ship. It demonstrates that an electrolyser using onboard purified seawater can generate hydrogen of a quality compliant with ISO 14687:2019. Additional contaminants (i.e., ions, heavy metal) were also measured. The study highlights the potential contaminants to be monitored and future research on new contaminants from seawater to further develop hydrogen fuel for maritime applications.

Beyond the farm: Making edible protein from CO2 via hybrid bioinorganic electrosynthesis

Beyond the farm: Making edible protein from CO2 via hybrid bioinorganic electrosynthesis

Economic dispatch of multi-area integrated electricity and natural gas systems considering emission and hourly spinning reserve constraints

With the increasing growth of gas-fired units and power-to-gas facilities, the power system and natural gas system become an integrated electricity and natural gas system (IENGS), which brings new opportunities to mitigate the associated environmental issues and deal with various uncertainties from electricity load, renewable energy generation, and gas load. Different geographical locations may have many IENGSs which are connected by electric or gas transmission lines, thus formulating multi-area IENGSs. These multi-area IENGSs are not simple addition of individual IENGSs, since renewable energy may distribute unequally between different IENGSs, and excess renewable energy needs to be transmitted from one area to another, but is limited by potential tie-line congestions. To solve these problems, this paper proposes an economic dispatch model for multi-area IENGSs considering tie-line congestion, maximum allowable emission bounds and hourly spinning reserve constraints. The considered multi-area IENGS consists of multiple single-area IENGSs, among which wind energy distribution varies considerably. The maximum allowable emission bounds of carbon dioxide and nitrogen oxygen are separately set based on their different influences on the environment. The hourly spinning reserves are allocated for both the power system and the natural gas system, which are provided by fossil fuel-fired units, power-to-gas facilities, gas pipelines, and natural gas storage facilities. After that, the presented model is converted into a mixed-integer linear programming problem for higher computing efficiency. Case studies for integrated systems are analyzed to demonstrate the effectiveness of the proposed model.

Liquefied Synthetic Natural Gas Produced through Renewable Energy Surplus: Impact Analysis on Vehicular Transportation by 2040 in Italy

Time mismatch between renewable energy production and consumption, grid congestion issues, and consequent production curtailment lead to the need for energy storage systems to allow for a greater renewable energy sources share in future energy scenarios. A power-to-liquefied synthetic natural gas system can be used to convert renewable energy surplus into fuel for heavy duty vehicles, coupling the electric and transportation sectors. The investigated system originates from power-to-gas technology, based on water electrolysis and CO2 methanation to produce a methane rich mixture containing H2, coupled with a low temperature gas upgrading section to meet the liquefied natural gas requirements. The process uses direct air CO2 capture to feed the methanation section; mol sieve dehydration and cryogenic distillation are implemented to produce a liquefied natural gas quality mixture. The utilization of this fuel in heavy duty vehicles can reduce greenhouse gases emissions if compared with diesel and natural gas, supporting the growth of renewable fuel consumption in an existing market. Here, the application of power-to-liquefied synthetic natural gas systems is investigated at a national level for Italy by 2040, assessing the number of plants to be installed in order to convert the curtailed energy, synthetic fuel production, and consequent avoided greenhouse gases emissions through well-to-wheel analysis. Finally, plant investment cost is preliminarily investigated.

An estimation–Based optimal scheduling model for settable renewable penetration level in energy hubs

Several recent studies suggest that power–to–gas (PtG) facilities can be operated to absorb and convert surplus renewable energy into hydrogen or synthetic natural gas, which is then supplied to the natural gas grid, forming an energy hub (EH). This paper argues and demonstrates that there is a trade off between maximizing the renewable penetration level (PRL) into the EH and minimizing the cost associated with it. The paper presents a new optimal scheduling model allowing variable and settable PRLs into the EH to minimize the system operating cost. The RPL, as determined by the grid operator, is taken in as a setting to the scheduling model. A new algorithm is presented by which the relationship between the RPL and scheduling setpoints of PtG and gas–fired generation (GfG) facilities are estimated. Accordingly, the optimal scheduling setpoints of PtG and GfG facilities are decided by the model, so that the required RPL can be met. The problem is formulated using the mixed integer nonlinear optimization method where the estimation algorithm is developed using the least error square technique. The developed problem is then solved using the combined interior point nonlinear programming and Newton trust region techniques. Numerical studies are conducted on a test system using historical operating data to validate the efficacy of the model. The system operating parameters are analyzed, and it is demonstrated that it is imperative to optimally manage the desired RPL taking into consideration the arbitrage revenue shortfall resulted from RPL enhancement in an EH.

Integration of Excess Renewable Energy with Natural Gas Infrastructure for the Production of Hydrogen and Chemicals

Power to gas (PtG) capitalizes on the free or low-cost power made available during frequent mismatches between power demand and power supply by converting water into hydrogen and oxygen via electrolysis. Current PtG projects vent the oxygen to the atmosphere and utilize the hydrogen for myriad purposes. Although oxygen has relatively little value when compared to hydrogen on a mass basis, the value of oxygen produced via electrolysis is significant compared to the value of the hydrogen due to the composition of water. This work presents a systematic methodology for designing a PtG project which co-utilizes hydrogen and oxygen to manufacture hydrogen and chemicals via integration with the natural gas infrastructure. A case study is developed and solved to demonstrate the applicability of the proposed methodology. The results of the case study show that significant value may be added by utilizing oxygen and the natural gas infrastructure.

Positive Energy District: A Model for Historic Districts to Address Energy Poverty

The Positive Energy District (PED) concept has been pointed out as key for cities' energy system transformation toward carbon neutrality. The PED may be defined as an energy-efficient and flexible urban area with net-zero energy import and greenhouse gas emissions, aiming toward annual local surplus of renewable energy. Most of the studies and practical experiences about PEDs are based on newly built districts, where the planning and integration of innovative solutions are less complex and more cost-effective. However, to achieve Europe Union's 2050 carbon-neutral ambition, we argue that the transformation of the settled districts is essential, including historic districts, which present common challenges across European cities, such as degraded dwellings, low-income families, and gentrification processes due to massive tourism flows. This paper aims to discuss how the PED model can be an opportunity for historic districts to reduce their emissions and mitigate energy poverty. The historic district of Alfama, in the city of Lisbon (Portugal), is used as a case study to show the potential of energy renovation measures and solar PV production in households, cornerstones of a PED. The annual energy needs potential reduction due to building retrofit is 84 and 19% for space heating and cooling, respectively, while the integration of building-integrated PV technologies in rooftops and windows potentially generates up to 60 GWh/year. At the district scale, these two components of the PED concept could require an investment of 60M€ to 81M€ depending on the PV technologies in the rooftops, a sensitive aspect in historical districts. Unlike other mechanisms to tackle energy poverty, like the social tariffs, the adoption of structural measures like building energy efficiency retrofit and renewable energy integration will contribute to solve the energy poverty problem, which is significant in Alfama, in both the winter and summer. The highlighted investments require an innovative financial scheme to support not only buildings' owners but also tenants, as these are among the most vulnerable to energy poverty. However, the social benefits of that investment, on the health system, air quality, climate resilience, labor productivity, and social integration, would be invaluable.

Water sorption enhanced CO2 methanation process: Optimization of reaction conditions and study of various sorbents

Excess renewable energy can produce hydrogen and together with carbon dioxide a closed energy loop can be formed through methanation (Power to Gas), which can be enhanced by in situ water sorption. Sorption causes a shift in equilibrium to favor methane production, while also decreasing secondary reactions and allowing operation at lower temperatures. In order to get suitable conditions for water sorption operating parameters were adjusted. The optimum temperature was 290 °C, avoiding high temperatures inside the catalytic bed due to the high exothermicity of the methanation; moreover, 15 bar of total pressure, 1.4 g catalyst and intermediate feedflows were found the best ones to obtain conversion close to equilibrium without external mass transfer resistance. The achieved hydrogen conversion was 92–94% with high selectivity, as no CO was detected and methane yield matched hydrogen conversion. The positive effect of water sorption was proved with Zeolite 4A, La2O3 and CaO sorbents.

Planning strategies of power-to-gas based on cooperative game and symbiosis cooperation

Power-to-gas (PtG), as a promising technology proposed to store surplus renewable energy (RE), can hardly be commercialized for its low profitability. In this paper, three approaches are proposed in this paper to enhance the profitability of the PtG. Firstly, a cooperative union containing PtG is proposed and its sustainability analysis is undertaken based on Shapley Value method. Secondly, the PtG reaction heat, as an essential by-product of PtG which is valuable and therefore requires further study, is fully exploited for district heating in the operation of regional integrated energy system, which is solved by an improved SOCP method. Thirdly, a symbiosis cooperation mode is designed for wind power and PtG to enhance the benefit of PtG through optimization-based trading strategy, which is a MINLP model and solved by Big-M method. The results show that the daily profit of PtG is significantly increased with the cooperative union as the symbiosis cooperation mode can produce a 15.1% profit lift, meanwhile, exploitation of reaction heat can produce an 8.6% profit lift. Finally, our study reveals the conflict of interest between wind power and the cogeneration. A sensitivity study on the proportion of reaction heat used for district heating is performed to verify the mutually beneficial relation between PtG and the cogeneration. The findings of this paper can guide the commercialization of PtG.

Day-ahead Optimal Scheduling of Regenerative Electric Heating System Considering Load Imbalance

For the regenerative electric heating system, on the premise of ensuring reliable heat supply to users, a day-ahead optimization scheduling method for the regenerative electric heating system considering the load imbalance is proposed. First, users' heating demand under normal working conditions and grid power rationing scenarios are calculated by estimate index method. Then, in order to match the heating demand of users and reduce the load imbalance caused by thermal storage electric heating in the distribution network, comprehensive consideration of grid constraints and the adjustable capacity of regenerative electric heating load, the operating strategy of the thermal storage electric heating system is studied. Reasonable control of heat storage and release in regenerative electric heating can not only reduce the distribution line pressure during heating period, but also maximize the accommodation of low-cost electricity such as surplus renewable energy and improve the economic benefits of the system. Taking the regenerative electric heating system in Chongli area of Zhangjiakou, Hebei Province as an example, the multi-objective optimal scheduling model is simulated and analyzed, and the feasibility and effectiveness of the proposed optimal scheduling strategy are verified.

Energy Analysis of A Hybrid Wind-Wave Solution For Remote Islands

The energy needs of most Aegean islands are covered by the operation of autonomous/local power stations (APS/LPS) using imported oil. The costly operation of the APS/LPS combined with the resulting environmental problems, set the issue of a sustainable and rational energy solution mainly for the remote islands, showing respect to the sensitive island ecosystems and the acceptance of local communities. In this context, high wind speeds as well as the remarkable wave potential of the Aegean Archipelagos could be the driving force for a sustainable energy supply solution for these islands by exploiting combined energy sources along with an appropriate energy storage system, comprising a modern hybrid renewable based station. Moreover, the exploitation of wave energy is one of the future priorities of the European Union (Blue Growth) in an effort to support the installation of wave energy converters, which are in the final stage of technological development. The proposed analysis examines the combined exploitation of the wave and wind potential for a representative medium sized island of the Aegean Archipelagos in order to cover its electrical needs. The results show that the installation of a hybrid power station contributes to a higher integration of renewable energy systems (RES) into an autonomous micro-grid and that the stochastic production of wind turbines can be counterbalanced due to the smoother (time-dependent) production of wave systems. In addition, the ability to store excess renewable energy enhances the energy supply security of an island micro-grid providing a clean energy solution for the remote Aegean island communities and thus reducing their oil dependence.

The opportunity of membrane technology for hydrogen purification in the power to hydrogen (P2H) roadmap: a review.

The global energy market is in a transition towards low carbon fuel systems to ensure the sustainable development of our society and economy. This can be achieved by converting the surplus renewable energy into hydrogen gas. The injection of hydrogen (⩽10% v/v) in the existing natural gas pipelines is demonstrated to have negligible effects on the pipelines and is a promising solution for hydrogen transportation and storage if the end-user purification technologies for hydrogen recovery from hydrogen enriched natural gas (HENG) are in place. In this review, promising membrane technologies for hydrogen separation is revisited and presented. Dense metallic membranes are highlighted with the ability of producing 99.9999999% (v/v) purity hydrogen product. However, high operating temperature (⩾300 °C) incurs high energy penalty, thus, limits its application to hydrogen purification in the power to hydrogen roadmap. Polymeric membranes are a promising candidate for hydrogen separation with its commercial readiness. However, further investigation in the enhancement of H2/CH4 selectivity is crucial to improve the separation performance. The potential impacts of impurities in HENG on membrane performance are also discussed. The research and development outlook are presented, highlighting the essence of upscaling the membrane separation processes and the integration of membrane technology with pressure swing adsorption technology.

Low carbon oriented power‐to‐gas station and integrated energy system planning with ancillary service provision and wind power integration

This study proposes an integrated energy system (IES) model consisting of natural gas system, electricity system, and power-to-gas stations (P2GSes), and then uses a centralised coordinated method to plan the IES. P2GSes can convert excessive renewable energy to natural gas and provide a promising approach to large-scale energy storage and long-distance energy transmission in the form of gas. However, considering the carbon emission of natural gas utilisation and high cost of P2G process, new embedded P2GSes will pose a threat to the economic and environment-friendly operation for the existing integrated energy system. Therefore, a more comprehensive P2G revenue objective, which is comprised of a secondary reserve service model, wind power integration model and carbon trading market participating model, is proposed in this study. The potential of P2GSes to provide the capacity of absorbing wind power and carbon reduction is innovatively and thoroughly evaluated in this study. The effectiveness of the proposed model is verified on an IES containing a coupled 24-bus electricity and 20-bus natural gas system. Simulation results show that it is optimal for the P2GSes revenue model to possess both capacities of absorbing wind power and converting the acquired power into natural gas as much as possible.

Grid balancing with a large‐scale electrolyser providing primary reserve

As the share of renewable energy sources increases, the grid frequency becomes more unstable. Therefore, grid balancing services will become more important in the future. Dedicated devices can be installed close to the point where off-shore wind farms are connected to the transmission grid on land. There, they can be used to attenuate power variations, reduce congestion and offer grid balancing. The provision of these ancillary services can create considerable additional economic revenue. In this study, the provision of the primary reserve by means of a large hydrogen electrolyser of 25 MW is investigated for the specific case of the Belgian transmission system. The revenue of the provision of the frequency containment reserve (FCR) is analysed on a techno-economic model, including capital costs, operational costs, the revenue of the generated hydrogen and oxygen products and the ancillary service income. The revenue depends strongly on the contracted power band. Therefore, it is optimised to yield maximum revenue. The results show that providing FCR creates considerable additional revenue. Therefore, a large electrolyser can be a good candidate to buffer excess renewable energy into green gas while simultaneously providing the grid support.

(Invited) Tailored Syngas Production Via High Temperature H2o-CO2 Co-Electrolysis

Solid oxide electrolysis cells (SOEC) operating at 600 – 850°C are used to split water using excess renewable or nuclear electrical energy and convert it to chemical energy which is stored in H2 and O2. SOECs can also be used as electrochemical reactors for the co-electrolysis of steam and carbon dioxide. The two reactants, typically waste products in an industrial plant, could be turned into syngas (CO+H2), a valuable and very commonly used reagent in the chemical industry. Syngas is subsequently used to produce synthetic fuels, olefins or other liquid hydrocarbons via Fischer-Tropsch synthesis or for methanol synthesis and hydroformylation.In this presentation we focus on CO2-H2O co-electrolysis, the simultaneous electrochemical reduction of carbon dioxide and steam, carried out on the porous Ni-based electrodes in high temperature SOECs. Experiments were conducted using multiple button cells. The rate of the electrochemical reactions was measured in the temperature range 700-850oC for varied reactant compositions: 10-98% CO2 and 5-50% H2O, also in the presence of some H2 and CO. Kinetics of electrochemical CO2 reduction were evaluated for different CO2/H2O ratios and compared to steam electrolysis. Product analysis was completed using gas chromatography. Long term electrochemical performance of multiple cells was recorded simultaneously for over 500 hours of continuous testing with occasional interruptions to obtain current-voltage characteristics and collect the impedance spectra. The ability to control H2 :CO ratios in generated syngas by varying the inlet H2O/CO2 ratios and cell potential was demonstrated. Thus, precise control of the H2 to CO ratios, a unique feature of electrochemical conversion can be used to optimize selectivity of the desired byproduct.

Thermophilic bio-electro carbon dioxide recycling harnessing renewable energy surplus

Renewable energies will represent an increasing share of the electricity supply, while flue and gasification-derived gases can be a promising CO2 feedstock with a heat load. In this study, microbial electrosynthesis of organic compounds from CO2 at high temperature was proposed as an alternative for valorising energy surplus and decarbonizing the economy. The unremitting fluctuation of renewable energy sources was assessed using two bioreactors at 50 °C, under circumstances of continuous and intermittent power supply (ON-OFF; 8–16 h), simulating an off-grid photovoltaic system. Results highlighted that maximum acetate production rate (43.27 g m−2 d−1) and columbic efficiency (98%) were achieved by working with an intermittent energy supply, while current density was reduced three times. This boosted the production of acetate per unit of electricity provided up to 138 g kWh−1 and reinforced the robustness of the technology by showing resilience to tolerate perturbations and returning to its initial state.