Excess Wind Power Research Articles

Determining onshore or offshore hydrogen storage for large offshore wind parks: The North Sea Wind Power Hub case

The large-scale integration of renewable energy sources leads to daily and seasonal mismatches between supply and demand and the curtailment of wind power. Hydrogen produced from surplus wind power offers an attractive solution to these challenges. In this paper, we consider a large offshore wind park and analyze the need for hydrogen storage at the onshore and offshore sides of a large transportation pipeline that connects the wind park to the mainland. The results show that the pipeline with line pack storage, though important for day-to-day fluctuations, will not offer sufficient storage capacity to bridge seasonal differences. Furthermore, the results show that if the pipeline is sufficiently sized, additional storage is only needed on one side of the pipeline, which would limit the needed investments. Results show that the policy which determines what part of the wind power is fed into the electricity grid and what part is converted into hydrogen has a significant influence on these seasonal storage needs. Therefore, investment decisions for hydrogen systems should be made by considering both the onshore and offshore storage requirements in combination with electricity transport to the mainland.

Joint chance‐constrained coordinated scheduling for electricity‐heat coupled systems considering hydrogen storage

AbstractStrong interdependence between power production and heat supply from combined power and heat units could restrict the wind power integration. Deploying hydrogen storage, typically formed by the electrolyser, hydrogen tank, and fuel cell, could be a promising measure to accommodate surplus wind power and facilitate the coordinated operation of power and heat. The authors consider coordinated scheduling under wind power uncertainty for an electricity‐heat coupled system with hydrogen storage and propose a distributionally robust joint chance‐constrained coordinated scheduling (DRJCC‐CS) model, where the waste heat from the electrolyser and fuel cell is incorporated. The authors design distributionally robust joint chance constraints to account for wind power uncertainty related constraints and derive their tractable inner and outer mixed‐integer convex approximations. Consequently, the proposed DRJCC‐CS model is casted into a mixed‐integer convex programme. Case studies are conducted to demonstrate the effectiveness of the proposed DRJCC‐CS method.

Low-Carbon Economic Dispatch Model of Integrated Energy System Accounting for Concentrating Solar Power and Hydrogen-Doped Combustion

Against the background of carbon peak and carbon neutralization, in order to solve the problem of poor flexibility of integrated energy systems and wind power consumption while improving the potential of hydrogen energy emission reduction, this study proposes an integrated energy system that takes into account the coupling of concentrating solar power (CSP), hydrogen-doped combustion, and power-to-gas (P2G) conversion. Firstly, a mathematical model of a CSP-CHP unit is established by introducing a CSP power station, aiming at the defect of the “heat to power” mode in the CHP system. Secondly, the energy consumption of P2G hydrogen energy production is satisfied by surplus wind power. The utilization stage of hydrogen energy is divided into supply CHP combustion and CO2 methanation, forming a CSP-P2G-HCHP collaborative framework and establishing an IES low-carbon economic dispatch model with CSP-P2G-HCHP. At the same time, the carbon trading mechanism is introduced to constrain the carbon emissions of the system. Finally, an optimization strategy with the minimum sum of the operation and maintenance cost, the energy purchase cost, the wind curtailment cost, and the carbon emission cost as the objective function is proposed, and the CPLEX solver is used to solve and carry out multi-case analysis. The simulation results show that the carbon emissions are reduced by 6.34%, the wind curtailment cost is reduced by 52.2%, and the total cost is reduced by 1.67%. The model takes into account the carbon reduction effect and operating efficiency and effectively improves the new energy consumption capacity.

Two-stage planning model of power-to-gas station considering carbon emission flow

The widespread use of fossil fuels has substantially contributed to global climate change. One of the most crucial ways to address climate change is to minimize carbon emissions in the energy sector. Power-to-Gas (P2G) technology provides a potential solution. In this context, this paper introduces a novel two-stage P2G planning method for the electric-gas coupling system, using carbon emission flow technology. The carbon emission flow model employed facilitates the distribution of carbon emissions across the entire energy network. Central to our planning strategy is the identification of nodes with reduced carbon emissions for the siting of P2G facilities, predicated on the premise that such nodes are indicative of significant renewable energy utilization. Constructing P2G systems at these particular nodes is strategically advantageous for augmenting renewable energy consumption. In the initial phase, a P2G siting planning methodology predicated on a low-carbon criterion is advanced, resulting in a definitive siting scheme. Subsequently, the second phase involves establishing a P2G capacity optimization model that seeks to strike an economic equilibrium between the utilization of surplus wind power and P2G operational investment. An enhanced pigeon optimization algorithm is employed to resolve the proposed model. Our method is verified by simulation. Compared with other conventional models, the accommodation capacity of renewable energy with the proposed method is enhanced, and the carbon emissions and operating costs of IES are also reduced.

Chemical Reactor Network modeling of ammonia–hydrogen combustion in a gas turbine: stochastic sensitivity analysis

To tackle climate change, we need to incorporate renewable energy sources on a large scale. One potential solution is the use of hydrogen, as an alternative energy vector that can be burnt in existing devices with little modification. Hydrogen can be produced from excess wind and solar power, ammonia, as a hydrogen carrier, is very appealing as it can be easily liquefied and distributed through the existing infrastructure. This study aims to explore the feasibility of using ammonia–hydrogen mixtures in industrial settings. This exploration is made by modeling a gas turbine system through a network of chemical reactors (CRN) and it is aimed at improving our understanding of the energy conversion process involving hydrogen, ammonia, and their mixtures. In this work, we analyze the most significant parameters of the CRN model, leveraging stochastic techniques. Specifically, we study the effects of the model and operational parameters on NOx emissions. This could represent a valuable aid in the development of CRN models capable of predicting emissions from gas turbine systems, to understand the impact of various operating conditions, such as pressure, temperature, equivalence ratio, and mixture composition.

Proposed Extension of the U.S.–Caribbean Super Grid to South America for Resilience during Hurricanes

Climate change mitigation, adaptation to intensifying hurricanes, and decarbonization challenges in developing countries emphasize the urgent need for resilient high-voltage grids to facilitate the expansion of renewables. This research explores the technical feasibility of extending the U.S.–Caribbean Super Grid to include the Virgin Islands, Guadeloupe, Martinique, Trinidad and Tobago, Guyana, Suriname, French Guyana, and the northeastern part of Brazil in South America. This proposed extension aims to capitalize on the recent introduction of a new generation of wind turbines certified for operation under strong hurricane forces. The research utilizes modeling and simulation techniques to evaluate the performance of the proposed extension. A method for modeling and estimating spatiotemporal wind power profiles is applied, and the results demonstrate a reduction in maximum wind power variability within the U.S.–Caribbean Super Grid. Depending on the hurricane trajectory, the variability is reduced from 56.6% to less than 43.2%. This reduction takes effect by distributing peak surplus wind power alongside the proposed U.S.–Caribbean–South America Super Grid (UCASG). The research concludes by acknowledging the merits and limitations of the study and discussing potential directions for future research in this field.

Integrated energy system optimization and scheduling method considering the source and load coordinated scheduling of thermal-storage electric boilers and electric vehicles

The northern regions of China face the challenges of the mismatch of the power supply and demand, as well as serious wind curtailment issues, caused mainly by the limitation of the “with heat to determine electricity” mode for combined heat and power generation during the winter season. To further absorb the surplus wind power and alleviate restrictions, a comprehensive energy system optimization method for parks based on coordinated scheduling between sources and loads is proposed in this paper. First, the implementation of a heat-storage electric boiler on the source side further achieves the decoupling of heat and power. Second, an optimized scheduling method for electric vehicles combining incentive scheduling and orderly scheduling is proposed on the load side, which helps flatten the load curve. Finally, a tiered carbon trading mechanism is introduced and a community integrated energy system (CIES) optimization scheduling model is established with the aim of minimizing the total cost of the CIES, and the problem is solved using the CPLEX commercial solver. The simulation results indicate that the overall system efficiency is significantly improved through the coordinated scheduling of power sources and loads. Specifically, the integration rate of wind power increases by 3.91% when compared to the sole consideration of the integrated demand response. Furthermore, the peak shaving and off-peak filling effect is considerably enhanced compared to the utilization of only thermal-storage electric boilers. Additionally, the implementation of coordinated scheduling leads to a reduction in the total system cost by 2764.32 yuan and a decrease in total carbon emissions by 3515.4 kg. These findings provide compelling evidence that the coordinated scheduling of power sources and loads surpasses the limitations of thermal power units, strengthens the demand response capability of electric vehicles, and enhances the economic benefits of the CIES.

Comparative study on flexibility enhancement of combined heat and power for wind power accommodation

Flexibility enhancement of coal-fired combined heat and power units is an essential approach for improving the wind power accommodation and a significant low-carbon way to achieve clean urban heating. To consume excess wind power, this paper proposed a novel combined heat and power system integrated with the various flexible technologies. The EBSILON software was applied for modeling the proposed thermal systems and analyzing the thermal performance under different operating conditions. On this basis, the mechanism of their heating compensation and wind power consumption was revealed and the indicator, the heating compensation capacity, was presented considering from both peak shaving and coal-savings perspectives. Compared with the conventional system, the wind power accommodation rate of the novel system had a maximum increment of 31.7% and the standard coal consumption had a maximum reduction of 14.3%. Meanwhile, by adding dynamic payback period and internal rate of return, the techno-economic performances were more reasonable and precise. The results showed that the heating compensation capacities of absorption heat pumps, low-pressure cylinder of turbine removal and thermal energy storage with extracted steam from turbine are 0.29 t/MWh, 0.26 t/MWh, and 0.25 t/MWh, respectively, which are better than that of other technologies. The net annual revenue of thermal energy storage system could reach 3.87 M$, 0.57 and 0.37 M$ higher than that of low-pressure cylinder of turbine removal and absorption heat pumps, respectively. It can be concluded that thermal energy storage can be the best to balance the peak shaving demand and techno-economic performance. In all, the proposed systems provided a promising method for the flexibilization of coal-fired combined heat and power units alongside new renewable systems.

Electricity price modeling from the perspective of start-up costs: incorporating renewable resources in non-convex markets

This paper constructs a comprehensive electricity market model in the context of China, highlighting the deviation caused by neglecting start-up costs from an engineering perspective. The model allows for the abandonment of excess wind and solar power generation, contributing to the achievement of research objectives in scenarios with a high proportion of renewable energy. Our method innovatively integrates fuel and carbon prices, clean energy expansion, and power system marginal prices according to the carbon trading rules of the Chinese power industry, providing a more accurate representation of market dynamics. Findings reveal that neglecting start-up costs can lead to significant biases in electricity prices. We demonstrate that the marginal price sometimes deviates from the fluctuation of the real value. While fuel and CO2 prices can be transmitted downstream, the value of new energy must be transmitted through its impact on the marginal unit. This insight is crucial for understanding the “missing money” problem in electricity markets. Based on these findings, we propose policy recommendations. We suggest considering fixed and average costs as pricing benchmarks and utilizing capacity utilization as a signal for demand response to adjust power pricing. Furthermore, we recommend trading different energy types separately in the spot market with different pricing benchmarks to ensure the homogeneity of marginal units.

A Two-Step Site Selection Concept for Underground Pumped Hydroelectric Energy Storage and Potential Estimation of Coal Mines in Henan Province

In the context of carbon neutrality, the phase-out of coal from the energy structure has resulted in numerous old coal mines that possess abundant underground space resources suitable for underground pumped hydroelectric energy storage (UPHES). Site selection and estimation of potential are critical to the planning and implementation of UPHES in old coal mines. This paper introduces a two-step site selection concept, including a screening assessment followed by a comprehensive assessment, to determine suitable locations for UPHES. The screening indicators in the screening assessment comprise geological features, mine water disasters, and minimum installed capacity, while the analytic hierarchy process (AHP) is applied in the comprehensive assessment. Additionally, coal mines in Henan Province are preliminarily screened through the screening assessment and the potential for UPHES is thoroughly investigated. The estimated volume of the drifts and shafts in old coal mines is approximately 1.35 × 107 m3, while in producing coal mines, it is around 2.96 × 107 m3. Furthermore, the corresponding annual potential for UPHES is 1468.9 GWh and 3226.3 GWh, respectively. By consuming surplus wind and solar power, UPHES is able to reduce 4.68 × 105 tonnes of carbon dioxide (CO2) emissions. The study provides preliminary guidance for policy-makers in developing UPHES in old coal mines.

A novel LH2/GH2/battery multi-energy vehicle supply station using 100% local wind energy: Technical, economic and environmental perspectives

With the gradual maturity of wind power technology, China's wind power generation has grown rapidly over the recent years. However, due to the on-site inconsumable electricity, the phenomenon of large-scale “wind curtailment” occurs in some areas. In this paper, a novel hybrid hydrogen/electricity refueling station is built near a wind farm, and a part of the surplus wind power is used to charge electric trucks, and the other part of the surplus power is used to produce “green hydrogen”. According to real-time load changes, different amounts of liquid hydrogen and gas hydrogen can be properly coordinated to provide timely energy supply for hydrogen trucks. For a 400 MW wind farm in the western Inner Mongolia, China, the feasibility of the proposed system has been carried out based on the sensitivity and reliability analysis, the static and dynamic economic modeling, with an entire life cycle analysis. Compared to the conventional technology, the initial investment of the proposed scheme (700.07 M$) decreases by 13.97%, and the dynamic payback period (10.93 years) decreases by 25.87%. During the life cycle of the proposed system, the accumulative NPV reaches 184.63 M$, which increases by 3.14 times compared to the case by conventional wind technology.

Environmental Economical Dispatching of Electric–Gas Integrated Energy System Considering Hydrogen Compressed-Natural Gas

As a high-quality secondary energy, hydrogen energy has great potential in energy storage and utilization. The development of power-to-hydrogen (P2H) technology has alleviated the problem of wind curtailment and improved the coupling between the power grid and the natural gas grid. Under the premise of ensuring safety, using P2H technology to mix the produced hydrogen into the natural gas network for long-distance transmission and power generation can not only promote the development of hydrogen energy but also reduce carbon emissions. This paper presents a new model for incorporating hydrogen into natural gas pipelines. To minimize the sum of wind curtailment cost, operation cost and carbon emission cost, an electric–gas integrated energy system (EGIES) model of hydrogen-compressed natural gas (HCNG) containing P2H for power generation is constructed. Aiming at the problem of global warming caused by a lot of abandoned wind and carbon emissions, the economy and environmental protection of the system model are analyzed. The results show that the model of EGIES considering HCNG can not only absorb excess wind power but also reduce carbon emission costs and system costs, which can reduce the total cost of the environmental economic dispatch of the EGIES by about 34.1%. In the context of the EGIES, the proposal of this model is of great significance to the economical and environmentally friendly operation of the system.

Research on surplus wind power consumption mechanism based on grid demand response

A method of using the demand response mechanism of the power grid to promote the consumption of surplus wind power is proposed for the consumption of new energy generation. In the proposed method, the replacement of the output of the gas turbine is used as an important way to consume the surplus power, and the consumption of the surplus wind power is realized by using the surplus wind power to replace part of the output of the gas turbine. With the objective function of the maximum consumable surplus wind power and the constraints of the maximum replaceable output of the gas turbine, the cost of the replacement output and the balance of supply and demand of the grid, a model of the maximum consumable surplus wind power considering the cost of the replacement output is constructed. In addition, a cost optimal allocation model considering the different quotations of surplus wind power resource owners is constructed to obtain the optimal surplus power resource consumption scheme.

Green Hydrogen Blends with Natural Gas and Its Impact on the Gas Network

With increasing shares of variable and uncertain renewable generation in many power systems, there is an associated increase in the importance of energy storage to help balance supply and demand. Gas networks currently store and transport energy, and they have the potential to play a vital role in longer-term renewable energy storage. Gas and electricity networks are becoming more integrated with quick-responding gas-fired power plants, providing a significant backup source for renewable electricity in many systems. This study investigates Ireland’s gas network and operation when a variable green hydrogen input from excess wind power is blended with natural gas. How blended hydrogen impacts a gas network’s operational variables is also assessed by modelling a quasi-transient gas flow. The modelling approach incorporates gas density and a compressibility factor, in addition to the gas network’s main pressure and flow rate characteristics. With an increasing concentration of green hydrogen, up to 20%, in the gas network, the pipeline flow rate must be increased to compensate for reduced energy quality due to the lower energy density of the blended gas. Pressure drops across the gas pipeline have been investigated using different capacities of P2H from 18 MW to 124 MW. The results show significant potential for the gas network to store and transport renewable energy as hydrogen and improve renewable energy utilisation without upgrading the gas network infrastructure.

Negative CO2 emission from oxy-fuel combustion in CFB boilers

Oxy-combustion by flue-gas recirculation for CO2 capture is applied to an existing, already CO2-neutral, biomass-fired circulating fluidized bed (CFB) boiler, thus resulting in negative CO2 emissions. The required oxygen concentration is determined by a heat balance, but in an existing plant the volume flow is then reduced as well as the fluidization velocity, which affects the heat transfer. Methods to resolve this problem are investigated. The oxygen is usually proposed to be supplied by air separation; a method that consumes a considerable share of the energy produced in the plant. Here, it is instead suggested to use oxygen produced together with hydrogen in electrolysis by excess wind and solar power.

Green Hydrogen Storage in an Underground Cavern: A Case Study in Salt Diapir of Spain

The Poza de la Sal diapir is a closed circular depression with Cretaceous Mesozoic materials, formed by gypsum, Keuper clays, and a large extension of salt in the center with intercalations of ophite. The low seismic activity of the area, the reduced permeability and porosity of the salt caverns, and the proximity to the Páramo de Poza wind park, make it a suitable place for the construction of a facility for underground storage of green hydrogen obtained from surplus wind power. The design of a cavern for hydrogen storage at a depth of 1000 m takes into account the differences in stresses, temperatures, and confining pressures involved in the salt deformation process. During the 8 months of the injection phase, 23.0 GWh can be stored in the form of hydrogen obtained from the wind energy surplus, to be used later in the extraction phase. The injection and extraction ratio must be developed under the conditions of geomechanical safety of the cavity, so as to minimize the risks to the environment and people, by conditioning the gas pressure inside the cavity to remain within a given range.

Coupled hydro-mechanical analysis of seasonal underground hydrogen storage in a saline aquifer

Hydrogen is promising an efficient and viable solution for low-carbon fuel for different purposes, such as transportation, manufacturing, and electricity. Fluctuating renewable energy production, however, can lead to a temporary imbalance between demand and supply. Nonetheless, it is feasible to mitigate this mismatch by converting the surplus wind power to hydrogen and storing it in geological (subsurface) systems. This work investigates the applicability of underground hydrogen storage in a saline aquifer at the Powder River Basin of Wyoming State. Thus, a 3D coupled hydro-mechanical simulation is presented to evaluate the hydraulic and geomechanical effects during three annual injection-reproduction cycles. A fully calibrated one-dimensional mechanical model has been constructed to characterize the 3D geomechanical model. The simulated results show that the designed storage scenario can be operated with reasonable recovery efficiency such that 78% of injected hydrogen can be extracted to meet 16.7% of household summer electricity consumption for the considered scenario in this study. The surface uplift is highly correlated with the cumulative amount of hydrogen injection and production, and a maximum magnitude of 1.6 cm has been estimated. Integrity analysis of subsurface rock and caprock based on the Mohr-Coulomb criterion demonstrates the safety of underground hydrogen storage at the selected site.

A Risk-Controllable Day-Ahead Transmission Schedule of Surplus Wind Power with Uncertainty in Sending Grids

Transmitting the surplus wind power (SWP) to load centers is necessary for grids which would reduce the wind curtailment. The reliability and sharpness of the existing estimation models of SWP are not enough to support the optimization of the transmission schedule. Besides, the existing optimization models for wind power scheduling are insufficient in controlling the high risk of SWP transmission. To address the above problems, this paper proposes a random fuzzy model (RFM) for SWP estimation and a risk-controllable optimization (RCSO) model for the SWP transmission schedule. In the RFM, a conditional probability of SWP is utilized to represent the actual probability distribution. The impacts of wind power consumption that cause the misalignment of existing models are considered in RFM by a fuzzy set. In RCSO, the economic and security risks of SWP transmission are quantified by the conditional value at risk (CVaR) theory. Transmission risks are controlled through automatic adjustment of the risk factor. An equivalent transformation method of the RCSO model is derived which can solve the nonlinear stochastic optimization problem with multi-objective. A case based on the historical data in Northeast China is studied to verify the effectiveness of the proposed models.

Electrothermally balanced operation of solid oxide electrolysis cells

The ongoing green energy transition is increasing the need for dynamic and efficient Power-to-X (PtX) systems to convert surplus wind and solar power to high-value products. The solid oxide electrolysis cell (SOEC) technology offers the highest energy conversion efficiency. However, high degradation and thermal variations that cause thermomechanical stress hinders up-scaling of the SOEC technology. Here we present a novel operation method that alleviates temperature variations and minimize degradation caused by impurities and nickel migration. By rapidly switching between electrolysis mode and brief periods in fuel cell mode, a flat thermal profile is obtained. Our results thus establish a new, simple way to achieve increased SOEC stack and module size and extended lifetime. The new operation method enables dynamic operation of large SOEC modules for renewable energy powered PtX systems which could drastically decrease costs associated with production of high-value green fuels and chemicals from wind and solar power.

Feeding H2-admixtures to domestic condensing boilers: Numerical simulations of combustion and pollutant formation in multi-hole burners

Hydrogen can be produced through electrolysis from excess wind and solar power. Then, its injection into the natural gas network allows mitigating the challenges posed by the variability and intermittency of renewables, by exploiting the existing infrastructure for storage and distribution. However, the addition of hydrogen to natural gas affects gas properties; hence we need to ensure the safe and efficient operation of existing end-user equipment, such as domestic burners and boilers. This work intends to investigate the effect of H2 addition on the combustion process and pollutant emissions in domestic condensing boilers. To this purpose, 3-dimensional numerical simulations of multi-hole geometries mimicking perforated burners, typically encountered in such appliances, are performed by using detailed kinetics and taking into account different hole-to-hole distances. Indeed, since the burner holes are located very close to each other, the neighbour premixed flames can interact, thus differing from single flame behaviour. The impact of H2 on the operating conditions, i.e. equivalence ratio and thermal load, is preliminarily evaluated to ensure that the numerical model closely emulates the practical situation we expect from the fuel composition change. Anticipation of the reaction zone occurs with H2-admixtures, while the downstream temperature decreases because the boiler naturally shifts towards leaner conditions and smaller thermal loads when adding H2 to natural gas. This behaviour has a positive impact on pollutant emissions as the NO thermal formation route is suppressed in a larger measure than the increase of the NNH-intermediate contribution.