Impact of hydrogen energy storage on California electric power system: Towards 100% renewable electricity

Decarbonization of the power sector is a key step towards greenhouse gas emissions reduction. Due to the intermittent nature of major renewable sources like wind and solar, storage technologies will be critical in the future power grid to accommodate fluctuating generation. The storage systems will need to decouple supply and demand by shifting electrical energy on many different time scales (hourly, daily, and seasonally). Power-to-Gas can contribute on all of these time scales by producing hydrogen via electrolysis during times of excess electrical generation, and generating power with high-efficiency systems like fuel cells when wind and solar are not sufficiently available. Despite lower immediate round-trip efficiency compared to most battery storage systems, the combination of devices used in Power-to-Gas allows independent scaling of power and energy capacities to enable massive and long duration storage. This study develops and applies a model to simulate the power system balance at very high penetration of renewables. Novelty of the study is the assessment of hydrogen as the primary storage means for balancing energy supply and demand on a large scale: the California power system is analyzed to estimate the needs for electrolyzer and fuel cell systems in 100% renewable scenarios driven by large additions of wind and solar capacities. Results show that the transition requires a massive increase in both generation and storage installations, e.g., a combination of 94 GW of solar PV, 40 GW of wind, and 77 GW of electrolysis systems. A mix of generation technologies appears to reduce the total required capacities with respect to wind-dominated or solar-dominated cases. Hydrogen storage capacity needs are also evaluated and possible alternatives are discussed, including a comparison with battery storage systems.     

Robust design of a future 100% renewable european energy supply system with hydrogen infrastructure

Variable renewable energy sources (VRES) will be the cornerstones of future energy supply systems. Nevertheless, their inherent intermittency remains an obstacle to their widespread deployment. Renewably-produced or ‘green’ hydrogen has been suggested as an energy carrier that could account for this in a sustainable manner. In this study, a fully VRES-based European energy system in the year 2050 is designed using an iterative minimal cost-optimization approach that ensures robust supply security across 38 weather-year scenarios (1980–2017). The impact of different power generation locations is factored in by defining exclusive VRES groups within each optimization region. From this, it can be seen that higher numbers of groups in each region offer cheaper electricity generation locations to the optimizer and thus decrease the system's total annual costs. Furthermore, the robust system design and impact of inter-annual variability is identified by iteratively combining the installed capacities of different system designs derived through the application of the 38 historical weather years. The system design outlined here has significantly lower capacities in comparison to the maximum regional capacities obtained in the first round of optimization.     

Power-to-ammonia in future North European 100 % renewable power and heat system

Power-to-gas and other chemicals-based storages are often suggested for energy systems with high shares of variable renewable energy. Here we study the North European power and district heat system with alternative long-term storage, the power-to-ammonia (P2A) technology. Assuming fully renewable power and heat sectors and large-scale electrification of road transport, we perform simultaneous optimization of capacity investments and dispatch scheduling of wind, solar, hydro and thermal power, energy storages as well as transmission, focusing on year 2050. We find that P2A has three major roles: it provides renewable feedstock to fertilizer industry and it contributes significantly to system balancing over both time (energy storage) and space (energy transfer). The marginal cost of power-based ammonia production in the studied scenarios varied between 431 and 528 €/t, which is in the range of recent ammonia prices. Costs of P2A plants were dominated by electrolysis. In the power and heat sector, with our cost assumptions, P2A becomes competitive compared to fossil natural gas only if gas price or CO₂ emission price rises above 70 €/MWh or 200 €/tCO₂.     

Assessment of the potential for hydrogen production from renewable resources in Argentina

The potential for hydrogen production from three major renewable resources (wind energy, solar energy and biomass) in Argentina is analyzed. This potential for the annual production of wind, solar and biomass hydrogen is represented with maps showing it per unit area in each department. Thus, by using renewable resource databases available in the country, a new Geographic Information System (GIS) of renewable hydrogen is created. In this system, several geographic variables are displayed, in addition to other parameters such as the potential for renewable hydrogen production per department relative to transport fuel consumption of each province or the environmental savings that would imply the production of hydrogen required to add 20% V/V to CNG, with the aim of developing the cleaner alternative CNG + H₂ fuel. In order to take into account areas where energy development would be restricted, land use and environmental exclusions were considered.     

Decarbonising city bus networks in Ireland with renewable hydrogen

This paper presents techno-economic modelling results of a nationwide hydrogen fuel supply chain (HFSC) that includes renewable hydrogen production, transportation, and dispensing systems for fuel cell electric buses (FCEBs) in Ireland. Hydrogen is generated by electrolysers located at each existing Irish wind farm using curtailed or available wind electricity. Additional electricity is supplied by on-site photovoltaic (PV) arrays and stored using lithium-ion batteries. At each wind farm, sizing of the electrolyser, PV array and battery is optimised system design to obtain the minimum levelised cost of hydrogen (LCOH). Results show the average electrolyser capacity factor is 64% after the integration of wind farm-based electrolysers with PV arrays and batteries. A location-allocation algorithm in a geographic information system (GIS) environment optimises the distributed hydrogen supply chain from each wind farm to a hypothetical hydrogen refuelling station in the nearest city. Results show that hydrogen produced, transported, and dispensed using this system can meet the entire current bus fuel demand for all the studied cities, at a potential LCOH of 5–10 €/kg by using available wind electricity. At this LCOH, the future operational cost of FCEBs in Belfast, Cork and Dublin can be competitive with public buses fuelled by diesel, especially under carbon taxes more reflective of the environmental impact of fossil fuels.     

Security of supply,energy spillage control and peaking options within a 100% renewable electricity system for New Zealand

In this paper, issues of security of supply, energy spillage control, and peaking options, within a fully renewable electricity system, are addressed. We show that a generation mix comprising 49% hydro, 23% wind, 13% geothermal, 14% pumped hydro energy storage peaking plant, and 1% biomass-fuelled generation on an installed capacity basis, was capable of ensuring security of supply over an historic 6-year period, which included the driest hydrological year on record in New Zealand since 1931. Hydro spillage was minimised, or eliminated, by curtailing a proportion of geothermal generation. Wind spillage was substantially reduced by utilising surplus generation for peaking purposes, resulting in up to 99.8% utilisation of wind energy. Peaking requirements were satisfied using 1550 MW of pumped hydro energy storage generation, with a capacity factor of 0.76% and an upper reservoir storage equivalent to 8% of existing hydro storage capacity. It is proposed that alternative peaking options, including biomass-fuelled gas turbines and demand-side measures, should be considered. As a transitional policy, the use of fossil-gas–fuelled gas turbines for peaking would result in a 99.8% renewable system on an energy basis. Further research into whether a market-based system is capable of delivering such a renewable electricity system is suggested.     

100% Renewable energy systems,climate mitigation and economic growth

Greenhouse gas mitigation strategies are generally considered costly with world leaders often engaging in debate concerning the costs of mitigation and the distribution of these costs between different countries. In this paper, the analyses and results of the design of a 100% renewable energy system by the year 2050 are presented for a complete energy system including transport. Two short-term transition target years in the process towards this goal are analysed for 2015 and 2030. The energy systems are analysed and designed with hour-by-hour energy system analyses. The analyses reveal that implementing energy savings, renewable energy and more efficient conversion technologies can have positive socio-economic effects, create employment and potentially lead to large earnings on exports. If externalities such as health effects are included, even more benefits can be expected. 100% Renewable energy systems will be technically possible in the future, and may even be economically beneficial compared to the business-as-usual energy system. Hence, the current debate between leaders should reflect a combination of these two main challenges.     

Potential of renewable hydrogen production for energy supply in Hong Kong

Hong Kong is highly vulnerable to energy and economic security due to the heavy dependence on imported fossil fuels. The combustion of fossil fuels also causes serious environmental pollution. Therefore, it is important to explore the opportunities for clean renewable energy for long-term energy supply. Hong Kong has the potential to develop clean renewable hydrogen energy to improve the environmental performance. This paper reviews the recent development of hydrogen production technologies, followed by an overview of the renewable energy sources and a discussion about potential applications for renewable hydrogen production in Hong Kong. The results show that although renewable energy resources cannot entirely satisfy the energy demand in Hong Kong, solar energy, wind power, and biomass are available renewable sources for significant hydrogen production. A system consisting of wind turbines and photovoltaic (PV) panels coupled with electrolyzers is a promising design to produce hydrogen. Biomass, especially organic waste, offers an economical, environmental-friendly way for renewable hydrogen production. The achievable hydrogen energy output would be as much as 40% of the total energy consumption in transportation.     

A 100% renewable electricity generation system for New Zealand utilising hydro,wind, geothermal and biomass resources

The New Zealand electricity generation system is dominated by hydro generation at approximately 60% of installed capacity between 2005 and 2007, augmented with approximately 32% fossil-fuelled generation, plus minor contributions from geothermal, wind and biomass resources. In order to explore the potential for a 100% renewable electricity generation system with substantially increased levels of wind penetration, fossil-fuelled electricity production was removed from an historic 3-year data set, and replaced by modelled electricity production from wind, geothermal and additional peaking options. Generation mixes comprising 53–60% hydro, 22–25% wind, 12–14% geothermal, 1% biomass and 0–12% additional peaking generation were found to be feasible on an energy and power basis, whilst maintaining net hydro storage. Wind capacity credits ranged from 47% to 105% depending upon the incorporation of demand management, and the manner of operation of the hydro system. Wind spillage was minimised, however, a degree of residual spillage was considered to be an inevitable part of incorporating non-dispatchable generation into a stand-alone grid system. Load shifting was shown to have considerable advantages over installation of new peaking plant. Application of the approach applied in this research to countries with different energy resource mixes is discussed, and options for further research are outlined.     

Energy system analysis of 100% renewable energy systems—The case of Denmark in years 2030 and 2050

This paper presents the methodology and results of the overall energy system analysis of a 100% renewable energy system. The input for the systems is the result of a project of the Danish Association of Engineers, in which 1600 participants during more than 40 seminars discussed and designed a model for the future energy system of Denmark. The energy system analysis methodology includes hour by hour computer simulations leading to the design of flexible energy systems with the ability to balance the electricity supply and demand. The results are detailed system designs and energy balances for two energy target years: year 2050 with 100% renewable energy from biomass and combinations of wind, wave and solar power; and year 2030 with 50% renewable energy, emphasising the first important steps on the way. The conclusion is that a 100% renewable energy supply based on domestic resources is physically possible, and that the first step towards 2030 is feasible to Danish society. However, Denmark will have to consider to which degree the country shall rely mostly on biomass resources, which will involve the reorganisation of the present use of farming areas, or mostly on wind power, which will involve a large share of hydrogen or similar energy carriers leading to certain inefficiencies in the system design.     

PEM electrolysis for production of hydrogen from renewable energy sources

PEM electrolysis is a viable alternative for generation of hydrogen from renewable energy sources. Several possible applications are discussed, including grid independent and grid assisted hydrogen generation, use of an electrolyzer for peak shaving, and integrated systems both grid connected and grid independent where electrolytically generated hydrogen is stored and then via fuel cell converted back to electricity when needed. Specific issues regarding the use of PEM electrolyzer in the renewable energy systems are addressed, such as sizing of electrolyzer, intermittent operation, output pressure, oxygen generation, water consumption and efficiency.     

Multi-agent direct current systems using renewable energy sources and hydrogen fuel cells

Direct current provides accumulation of electricity and is therefore necessary when using renewable energy sources. Hydrogen energy storage devices in the form of fuel cells are the most effective and environmentally friendly way of energy storage and conservation. Shortcomings of electric power networks compared with DC networks in terms of stability, controllability, reliability and redundancy are noted. The necessity of transition from digitalization in the form of automated process control systems to smart grids, and subsequently to multi-agent DC networks with a high degree of redundancy, is revealed. Besides, the paper deals with application of distributed generation consisting of traditional and renewable energy sources, as well as accumulators and static converters. Characteristics of the above mentioned elements are given for simulating the modes in order to select the structure and control algorithms that provide increased power supply reliability.     

Exploring the feasibility of green hydrogen production using excess energy from a country-scale 100% solar-wind renewable energy system

When planning large-scale 100% renewable energy systems (RES) for the year 2050, the system capacity is usually oversized for better supply-demand matching of electrical energy since solar and wind resources are highly intermittent. This causes excessive excess energy that is typically dissipated, curtailed, or sold directly. The public literature shows a lack of studies on the feasibility of using this excess for country-scale co-generation. This study presents the first investigation of utilizing this excess to generate green hydrogen gas. The concept is demonstrated for Jordan using three solar photovoltaic (PV), wind, and hybrid PV-wind RESs, all equipped with Lithium-Ion battery energy storage systems (ESSs), for hydrogen production using a polymer electrolyte membrane (PEM) system. The results show that the PV-based system has the highest demand-supply fraction (>99%). However, the wind-based system is more favorable economically, with installed RES, ESS, and PEM capacities of only 23.88 GW, 2542 GWh, and 20.66 GW. It also shows the highest hydrogen annual production rate (172.1 × 10³ tons) and the lowest hydrogen cost (1.082 USD/kg). The three systems were a better option than selling excess energy directly, where they ensure annual incomes up to 2.68 billion USD while having payback periods of as low as 1.78 years. Furthermore, the hydrogen cost does not exceed 2.03 USD/kg, which is significantly lower than the expected cost of hydrogen (3 USD/kg) produced using energy from fossil fuel-based systems in 2050.     

Utilization of biodiesel waste as a renewable resource for activated carbon: Application to environmental problems

Stepping into the new globalized and paradigm shifted era, a huge revolution has been undergone by the oil palm industry. From a humble source of the edible oil, today oil palm has demonstrated a wide variety of uses, almost by every part of its plant. With the price of the crude petroleum hitting record height every other day, the feasibility of palm oil and oil palm biomass as renewable substitutes for the production of biodiesel has been proposed. Lately, its development has received various criticisms, mainly hinges on the huge generation of solid residues which are currently no profitable use. In view of the aforementioned reason, this paper presents a state-of-the-art review of oil palm industry, its fundamental background studies, propagation and industrial applications. Moreover, the recent developments on the preparation of activated carbons from oil palm waste, its major challenges together with the future expectation are summarized and discussed. Conclusively, the expansion of oil palm waste in the field of adsorption science represents a potentially viable and powerful tool, leading to the superior improvement of pollution control and environmental conservation.     

Global warming and renewable energy sources for sustainable development in Turkey

Turkey, with its young population and growing energy demand per person, its fast growing urbanization, and its economic development, has been one of the fast growing power markets of the world for the last two decades. It is expected that the demand for electric energy in Turkey will be 300 billion kWh by the year 2010 and 580 billion kWh by the year 2020. Turkey is heavily dependent on expensive imported energy resources that place a big burden on the economy and air pollution is becoming a great environmental concern in the country. In this regard, renewable energy resources appear to be the one of the most efficient and effective solutions for clean and sustainable energy development in Turkey. Turkey's geographical location has several advantages for extensive use of most of these renewable energy sources. This article presents a review of the potential and utilization of the renewable energy sources in Turkey.     

The economic analysis for hydrogen production cost towards electrolyzer technologies: Current and future competitiveness

Hydrogen production by electrolysis technology spurs as extensive investigation toward new clear energy acquisition. The mainstream hydrogen production electrolyzers, including alkaline electrolyzer (ALK), anion exchange membrane electrolyzer (AEM), and proton exchange membrane electrolyzer (PEM), are traced to compare their current and future hydrogen production cost regarding technology development. Technologies' characteristics are originally described as the polarization curve parameters such as current density, overpotential, and polarization curve slope. The feature of crucial materials such as catalysts and membranes are also taken into consideration. Then, a bottom-up hydrogen production cost prediction model stemming from technical factors is established with a combination of manufacturing and operating considerations. According to model predictions, the cost of hydrogen production of ALK will be 23.85% and 51.59% lower than AEM and PEM technologies in the short term. However, under technological advancement or breakthrough, the hydrogen production cost of AEM and PEM is expected to be 24% and 56.5% lower in the medium-term and long-term, respectively. The lifetime of the electrolyzers is significantly vital to affect the cost of hydrogen production. The cost reduction space brought about by various technical factors is also explored for the blueprint planning of the hydrogen economy.     

Comparing least cost scenarios for 100% renewable electricity with low emission fossil fuel scenarios in the Australian National Electricity Market

Policy makers face difficult choices in planning to decarbonise their electricity industries in the face of significant technology and economic uncertainties. To this end we compare the projected costs in 2030 of one medium-carbon and two low-carbon fossil fuel scenarios for the Australian National Electricity Market (NEM) against the costs of a previously published scenario for 100% renewable electricity in 2030. The three new fossil fuel scenarios, based on the least cost mix of baseload and peak load power stations in 2010, are: (i) a medium-carbon scenario utilising only gas-fired combined cycle gas turbines (CCGTs) and open cycle gas turbines (OCGTs); (ii) coal with carbon capture and storage (CCS) plus peak load OCGT; and (iii) gas-fired CCGT with CCS plus peak load OCGT. We perform sensitivity analyses of the results to future carbon prices, gas prices, and CO₂ transportation and storage costs which appear likely to be high in most of Australia. We find that only under a few, and seemingly unlikely, combinations of costs can any of the fossil fuel scenarios compete economically with 100% renewable electricity in a carbon constrained world. Our findings suggest that policies pursuing very high penetrations of renewable electricity based on commercially available technology offer a cost effective and low risk way to dramatically cut emissions in the electricity sector.     

Stand-alone PEM water electrolysis system for fail safe operation with a renewable energy source

A complete stand-alone electrolyser system has been constructed as a transportable unit for demonstration of a sustainable energy facility based on hydrogen and a renewable energy source. The stand-alone unit is designed to support a polymer electrolyte membrane (PEM) stack operating at up to ∼4 kW input power with a stack efficiency of about 80% based on HHV of hydrogen. It is self-pressurizing and intended for operation initially at a differential pressure of less than 6 bar across the membrane electrode assembly with the hydrogen generation side being at a higher pressure. With a slightly smaller stack, the system has been operated at an off-site facility where it was directly coupled to a 2.4 kW photovoltaic (PV) solar array. Because of its potential use in remote areas, the balance-of-plant operates entirely on 12 V DC power for all monitoring, control and safety requirements. It utilises a separate high-current supply as the main electrolyser input, typically 30–40 V at 100 A from a renewable source such as solar PV or wind. The system has multiple levels of built-in operator and stack safety redundancy. Control and safety systems monitor all flows, levels and temperatures of significance. All fault conditions are failsafe and are duplicated, triggering latching relays which shut the system down. Process indicators monitor several key variables and allow operating limits to be easily adjusted in response to experience of system performance gained in the field.     

Thermodynamic analysis of a multigeneration system using solid oxide cells for renewable power-to-X conversion

A hybrid renewable-based integrated energy system for power-to-X conversion is designed and analyzed. The system produces several valuable commodities: Hydrogen, electricity, heat, ammonia, urea, and synthetic natural gas (SNG). Hydrogen is produced and stored for power generation from solar energy by utilizing solid oxide electrolyzers and fuel cells. Ammonia, urea, and synthetic natural gas are produced to mitigate hydrogen transportation and storage complexities and act as energy carriers or valuable chemical products. The system is analyzed from a thermodynamic perspective, the exergy destruction rates are compared, and the effects of different parameters are evaluated. The overall system's energy efficiency is 56%, while the exergy efficiency is 14%. The highest exergy destruction occurs in the Rankine cycle with 48 MW. The mass flow rates of the produced chemicals are 0.064, 0.088, and 0.048 kg/s for ammonia, urea, and SNG, respectively.