Potential of renewable surplus electricity for power-to-gas and geo-methanation in Switzerland

Energy systems are increasingly exposed to variable surplus electricity from renewable sources, particularly photovoltaics. This study estimates the potential to use surplus electricity for power-to-gas with geo-methanation for Switzerland by integrated energy system and power-to-gas modelling. Various CO₂ point sources are assessed concerning exploitable emissions for power-to-gas, which were found to be abundantly available such that 60 TWh surplus electricity could be converted to methane, which is the equivalent of the current annual Swiss natural gas demand. However, the maximum available surplus electricity is only 19 TWh even in a scenario with high photovoltaic expansion. Moreover, making this surplus electricity available for power-to-gas requires an ideal load shifting capacity of up to 10 times the currently installed pumped-hydro capacity. Considering also geological and economic boundary conditions for geo-methanation at run-of-river and municipal waste incinerator sites with nearby CO₂ sources reduces the exploitable surplus electricity from 19 to 2 TWh.     

A quantitative assessment of the hydrogen storage capacity of the UK continental shelf

Increased penetration of renewable energy sources and decarbonisation of the UK's gas supply will require large-scale energy storage. Using hydrogen as an energy storage vector, we estimate that 150 TWh of seasonal storage is required to replace seasonal variations in natural gas production. Large-scale storage is best suited to porous rock reservoirs. We present a method to quantify the hydrogen storage capacity of gas fields and saline aquifers using data previously used to assess CO₂ storage potential. We calculate a P50 value of 6900 TWh of working gas capacity in gas fields and 2200 TWh in saline aquifers on the UK continental shelf, assuming a cushion gas requirement of 50%. Sensitivity analysis reveals low temperature storage sites with sealing rocks that can withstand high pressures are ideal sites. Gas fields in the Southern North Sea could utilise existing infrastructure and large offshore wind developments to develop large-scale offshore hydrogen production.     

Hydrogen supply scenarios for a climate neutral energy system in Germany

A climate neutral energy system in Germany will most likely require green hydrogen. Two important factors, that determine whether the hydrogen will be imported or produced locally from renewable energy are still uncertain though - the import price for green hydrogen and the upper limit for photovoltaic installations. To investigate the impact of these two factors, the authors calculate cost optimized climate neutral energy systems while varying the import price from 1.25 €/kg to 5 €/kg with unlimited import volume and the photovoltaic limit from 300 GW to unlimited. In all scenarios, hydrogen plays a significant role. At a medium import price of 3.75 €/kg and photovoltaic limits of 300–900 GW the hydrogen supply is around 1200 to 1300 TWh with import shares varying from 60 to 85%. In most scenarios the electrolysis profile is highly correlated with the photovoltaic power, which leads to full load hours of 1870 h–2770 h.     

Utility-scale subsurface hydrogen storage: UK perspectives and technology

To reduce effects from anthropogenically induced climate change renewable energy systems are being implemented at an accelerated rate, the UKs wind capacity alone is set to more than double by 2030. However, the intermittency associated with these systems presents a challenge to their effective implementation. This is estimated to lead to the curtailment of up to 7.72 TWh by 2030. Through electrolysis, this surplus can be stored chemically in the form of hydrogen to contribute to the 15 TWh required by 2050. The low density of hydrogen constrains above ground utility-scale storage systems and thus leads to exploration of the subsurface.This literature review describes the challenges and barriers, geological criteria and geographical availability of all utility-scale hydrogen storage technologies with a unique UK perspective. This is furthered by discussion of current research (primarily numerical models), with particular attention to porous storage as geographical constraints will necessitate its deployment within the UK. Finally, avenues of research which could further current understanding are discussed.     

Dynamic modeling and characteristic analysis of natural gas network with hydrogen injections

With the transformation of energy structure, the proportion of renewable energy in the power grid continues to increase. However, the power grid's capacity to absorb renewable is limited. In view of this, converting the excess renewable energy into hydrogen and injecting it into natural gas network for transportation can not only increase the absorption capacity of renewable energy but also reduce the transportation cost of hydrogen. While this can lead to the problem that hydrogen injection will make the dynamic characteristics of the pipeline more complicated, and hydrogen embrittlement of pipeline may occur. It is of great significance to simulate the dynamic characteristics of gas pipeline with hydrogen injection, especially the hydrogen mixture ratio. In this paper, the cell segmentation method is used to solve each natural gas pipeline model, the gas components are recalculated in each cell and the parameters of partial differential equation are updated. Additionally, the dynamic simulation model of natural gas network with hydrogen injections is established. Simulation results show that for a single pipeline, when the inlet hydrogen ratio changes, whether or not hydrogen injection has little influence on the pressure and flow. The propagation speed of hydrogen concentration is far less than that of the pressure and flow rate, and it takes about 1.2 × 10⁵ s for the 100 km pipeline hydrogen ratio to reach the steady state again.     

Upgrading biogas produced at dairy farms into renewable natural gas by methanation

Renewable natural gas can be produced from raw biogas, a product of the anaerobic decomposition of organic material, by upgrading its CO₂ content (25‐50%) via thermocatalytic hydrogenation (CO₂ methanation). The H₂ needed for this reaction can be generated by water electrolysis powered by carbon emission‐free energy sources such as renewable or nuclear power, or using surplus electricity. Herein, after briefly outlining some aspects of biogas production at dairy farms and highlighting recent developments in the design of methanation systems, a case study on the renewable natural gas generation is presented. The performance of a system for renewable natural gas generation from a 2000‐head dairy farm livestock manure is evaluated and assessed for its economic potential. The project is predicted to generate revenue through the sale of energy and carbon credits with the payback period of 5 years, with a subsidized energy price.     

Resource assessment for green hydrogen production in Kazakhstan

Kazakhstan has long been regarded as a major exporter of fossil fuel energy. As the global energy sector is undergoing an unprecedented transition to low-carbon solutions, new emerging energy technologies, such as hydrogen production, require more different resource bases than present energy technologies. Kazakhstan needs to consider whether it has enough resources to stay competitive in energy markets undergoing an energy transition. Green hydrogen can be made from water electrolysis powered by low-carbon electricity sources such as wind turbines and solar panels. We provided the first resource assessment for green hydrogen production in Kazakhstan by focusing on three essential resources: water, renewable electricity, and critical raw materials. Our estimations showed that with the current plan of Kazakhstan to keep its water budget constant in the future, producing 2–10 Mt green hydrogen would require reducing the water use of industry in Kazakhstan by 0.6–3% or 0.036–0.18 km³/year. This could be implemented by increasing the share of renewables in electricity generation and phasing out some of the water- and carbon-intensive industries. Renewable electricity potential in South and West Kazakhstan is sufficient to run electrolyzers up to 5700 and 1600 h/year for wind turbines and solar panels, respectively. In our base case scenario, 5 Mt green hydrogen production would require 50 GW solar and 67 GW wind capacity, considering Kazakhstan's wind and solar capacity factors. This could convert into 28,652 tons of nickel, 15,832 tons of titanium, and many other critical raw materials. Although our estimations for critical raw materials were based on limited geological data, Kazakhstan has access to the most critical raw materials to support original equipment manufacturers of low-carbon technologies in Kazakhstan and other countries. As new geologic exploration kicks off in Kazakhstan, it is expected that more deposits of critical raw materials will be discovered to respond to their potential future needs for green hydrogen production.     

The prospective of coal power in China: Will it reach a plateau in the coming decade?

Coal power holds the king position in China's generation mix and has resulted in ever-increasing ecological and environmental issues; hence, the development of the electric power sector is confronted with a series of new challenges. China has recently adopted a new economic principle of the “new economic normal,” which has a large effect on the projection electricity demand and power generation planning through 2020. This paper measures electricity demand based upon China's social and economic structure. The 2020 roadmap presents China's developing targets for allocating energy resources to meet new demands, and the 2030 roadmap is compiled based upon an ambitious expansion of clean energy sources. Results show that electricity demand is expected to reach 7500 TWh in 2020 and 9730 TWh in 2030. Coal power is expected to reach its peak in 2020 at around 970 GW, and will then enter a plateau, even with a pathway of active electricity substitution in place.     

Transforming the electricity generation of the Berlin–Brandenburg region,Germany

We present possible steps for Germany's capital region for a pathway towards high-level renewable energy contributions. To this end, we give an overview of the current energy policy and status of electricity generation and demand of two federal states: the capital city Berlin and the surrounding state of Brandenburg. In a second step we present alternative, feasible scenarios with focus on the years 2020 and 2030. All scenarios were numerically evaluated in hourly time steps using a cost optimisation approach. The required installed capacities in an 80% renewables scenario in the year 2020 consist of 8.8 GW wind energy, 4.8 GW photovoltaics, 0.4 GW_el bioenergy, 0.6 GW_el methanation and a gas storage capacity of 180 GWh_th. In order to meet a renewable electricity share of 100% in 2030, approximately 9.5 GW wind energy, 10.2 GW photovoltaics and 0.4 GW_el bioenergy will be needed, complemented by a methanation capacity of about 1.5 GW_el and gas storage of about 530 GWh_th. In 2030, an additional 11 GWh_el of battery storage capacity will be required. Approximately 3 GW of thermal gas power plants will be necessary to cover the residual load in both scenarios. Furthermore, we studied the transmission capacities of extra-high voltage transmission lines in a second simulation and found them to be sufficient for the energy distribution within the investigated region.     

Where,when and how much solar is available? A provincial-scale solar resource assessment for China

Integrating variable energy resources, notably solar and wind, requires better understanding of where, when and how much of variable resources are available. China's ambitious solar energy development goal will be greatly facilitated by the resources assessment at higher spatial and temporal resolution. We utilized 10-year hourly solar irradiation data from 2001 to 2010 from 200 representative locations to develop provincial solar availability profiles. We found that China has a potential stationary solar capacity from 4700 GW to 39300 GW, distributed solar about 200 GW, and the annual solar output could reach 6900 TWh to 70100 TWh. Resources are most concentrated in northwest provinces, topped by Inner Mongolia, Xinjiang and Gansu. The challenge of solar development in China is integration rather than resources. The spatial and temporal variation of the solar resource show an efficient, robust, and inter-connected national grid and sound energy planning would be necessary to facilitate the integration of these vastly available but variable solar resources.     

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.     

Allocation of energy resources for power generation in India: Business as usual and energy efficiency

This paper deals with MARKAL allocations for various energy sources, in India, for Business As Usual (BAU) scenario and for the case of exploitation of energy saving potential in various sectors of economy. In the BAU scenario, the electrical energy requirement will raise up to 5000 bKwh units per year or 752 GW of installed capacity with major consumers being in the industry, domestic and service sectors. This demand can be met by a mix of coal, hydro, nuclear and wind technologies. Other reneawbles i.e. solar and biomass will start contributing from the year 2040 onwards. By full exploitation of energy saving potential, the annual electrical energy demand gets reduced to 3061 bKwh (or 458 GW), a reduction of 38.9%.The green house gas emissions reduce correspondingly. In this scenario, market allocations for coal, gas and large hydro become stagnant after the year 2015.     

Steady-state analysis of a natural gas distribution network with hydrogen injection to absorb excess renewable electricity

Natural gas networks, thanks to their extensiveness and capillarity, could play a crucial role in the green transition of the energy sector. The decarbonization of a gas network can be achieved by injecting green hydrogen into the grid. This work aims to simulate a low-pressure natural gas distribution network serving industrial and residential users and subjected to one localized injection of hydrogen produced by renewable energy sources. The main quality indexes and fluid dynamics parameters of the gas mixture are analysed to understand the feasibility of injecting hydrogen into a natural gas network. Firstly, the network was examined under nominal steady conditions with a constant hydrogen injection. Then, the same grid was simulated considering a 24-h pattern of hydrogen injection, according to the power daily surplus. The results show that the grid can help to buffer the surplus of renewable power produced. The conclusions derived by the results underline that the effect of H2 injection is maximum during the highest excess of electricity and the importance of an accurate choice of the injection node: a wrong choice leads, at the peak of power production, leads to an amplification of the H2 injection impact and hence to a reduction of the Wobbe Index value that overcomes the safety lower limit.     

Reconciling self-sufficiency and renewable energy targets in a hydro dominated system: The view from British Columbia

British Columbia's energy policy is at a crossroads; the province has set a goal of electricity self-sufficiency, a 93% renewable portfolio standard and a natural gas development strategy that could increase electricity consumption by 21 TWh to 33 TWh. To ascertain the BC's supply position, a mathematical programming model of the physical workings of BC's hydroelectric generating system is developed, with head heights at the two dominant power stations treated as variable. Using historical water inflow and reservoir level data, the model is used to investigate whether BC is capable of meeting its self-sufficiency goals under various water supply and electricity demand scenarios.     

A review on distributed generation impacts on electric power system

In 2021, the world's total installed capacity of generation units based on renewable energy sources (not including hydropower) amounted to about 1674 GW: over 825 GW and 849 GW of wind and solar power plants were installed respectively. The growing of the installed capacity of these distributed generators is a response to the increasing the power consumption, global environmental issues and has also become possible due to the development of technology in field of power semiconductor devices. However, on the way of large-scale implementation of distributed generators based on renewable energy sources, traditional electric power system meets new challenges to ensure the reliability and sustainability of new electric power systems with renewable energy sources. In particular, distributed generators change processes in the electric power system, impact to the parameters and power balance, change the magnitude and direction of power flow and short-circuit current, which determines the need to update the settings of the relay protection and automation systems of traditional electric power system and to coordinate their operation with automatic control systems of installed distributed generators. The above-mentioned tasks form a number of scientific research directions, one of which is a task of determining optimal size and location of distributed generators. The main purpose of this optimization task is to reduce power losses, operating and total electricity cost, improve the voltage profile, etc. In addition, the correct and reasonable placement of distributed generators defines an effective planning of the operating modes of electric power system and power plants (especially based on renewable energy sources, the operating modes of which depend on weather conditions and can be sharply variable).The paper highlighted the impacts of distributed generators on power losses, the voltage level, maintaining the power balance and the possibility of participating in the frequency regulation, and short-circuit current in power system. The optimization criteria, the main limiting conditions, as well as methods for solving this optimization problem are considered. This review will help the System operators and investing companies, especially in Russia, to form the main aim, objective function and constraints that will aid to meet their load demand at minimum cost and to choose from the options available for optimization of location and capacity of distributed generators.     

Hydrogen supply chain scenarios for the decarbonisation of a German multi-modal energy system

Analysing hydrogen supply chains is of utmost importance to adequately understand future energy systems with a high degree of sector coupling. Here, a multi-modal energy system model is set up as linear programme incorporating electricity, natural gas as well as hydrogen transportation options for Germany in 2050. Further, different hydrogen import routes and optimised inland electrolysis are included. In a sensitivity analysis, hydrogen demands are varied to cover uncertainties and to provide scenarios for future requirements of a hydrogen supply and transportation infrastructure. 80% of the overall hydrogen demand of 150 TWh/a emerge in Northern Germany due to optimised electrolyser locations and imports, which subsequently need to be transported southwards. Therefore, a central hydrogen pipeline connection from Schleswig-Holstein to the region of Darmstadt evolves already for moderate demands and appears to be a no-regret investment. Furthermore, a natural gas pipeline reassignment potential of 46% is identified.     

Assessing the potential of renewable energy sources in Turkey

To meet Turkey’s growing energy demand, the installed electric power capacity of 27.8 GW in 2001 has to be doubled by 2010 and increased fourfold by 2020. The difference between Turkey’s total primary energy supply (TPES) of from its own sources and total final consumption (TFC) is projected grow from 1 quad (1.06–2.06) in 1999 to 5.71 quads (2.79–8.5) in 2020 (1 QUAD=293.071 TWh). Turkey’s limited amount of fossil fuels has a present average ratio of proved reserves of 97.38 quads to production rate of 3.2 quads yr⁻¹ of about 30 years. Turkey’s reliance on fossil fuel-based energy systems to meet the growing demand is most likely to exacerbate the issues of energy insecurity, national environmental degradation, and global climate change in increasing proportions. Economically-feasible renewable energy potential in Turkey is estimated at a total of ca. 1.69 quads yr⁻¹ (495.4 TWh yr⁻¹) with the potential for 0.67 quads yr⁻¹ (196.7 TWh yr⁻¹) of biomass energy, 0.42 quads yr⁻¹ (124 TWh yr⁻¹) of hydropower, 0.35 quads yr⁻¹ (102.3 TWh yr⁻¹) of solar energy, 0.17 quads yr⁻¹ (50 TWh yr⁻¹) of wind energy, and 0.08 quads yr⁻¹ (22.4 TWh yr⁻¹) of geothermal energy. Pursuit and implementation of sustainability-based energy policy could provide about 90 and 35% of Turkey’s total energy supply and consumption projected in 2010, respectively. Utilization of renewable energy technologies for electricity generation would necessitate about 23.2 Mha (29.8%) of Turkey’s land resources.     

Wind energy,electricity, and hydrogen in the Netherlands

The curbing of greenhouse gases (GHG) is an important issue on the international political agenda. The substitution of fossil fuels by renewable energy sources is an often-advocated mitigation strategy. Wind energy is a potential renewable energy source. However, wind energy is not reliable since its electricity production depends on variable weather conditions. High wind energy penetration rates lead to losses due to power plant operation adjustments to wind energy. This research identifies the potential energetic benefits of integrated hydrogen production in electricity systems with high wind energy penetration. This research concludes that the use of system losses for hydrogen production via electrolysis is beneficial in situations with ca. 8 GW or more wind energy capacity in the Netherlands. The 2020 Dutch policy goal of 6 GW will not benefit from hydrogen production in terms of systems efficiency. An ancillary beneficial effect of coupling hydrogen production with wind energy is to relieve the high-voltage grid.     

Hydrogen from natural gas without release of CO2 to the atmosphere

The “Hydrogen economy”, in which hydrogen will be a main carrier of energy from renewable sources, is a long term prospect. In the near and medium term increasing demand for hydrogen--also as an energy carrier in special niches--will probably be covered by hydrogen from fossil sources, mainly natural gas. This can be acceptable from an environment as well as an economical point of view, since hydrogen can be produced from natural gas at acceptable costs, without release of CO₂ to the atmosphere. There are two main options for this: (1) hydrogen from natural gas by conventional technology (e.g. steam reforming) including CO₂ sequestration; (2) high temperature pyrolysis of natural gas, yielding pure hydrogen and carbon black. Technologies for industrial scale realisation of these options have been developed and evaluated in Norway, which is a large producer and exporter of natural gas. The economy and market opportunities are discussed in the paper. It appears that renewable energy costs must come down considerably from present levels before hydrogen from renewables can compete with hydrogen from natural gas without release of CO₂ to the atmosphere.     

Production of hydrogen for export from wind and solar energy,natural gas,and coal in Australia

Hydrogen production for export to Japan and Korea is increasingly popular in Australia. The theoretically possible paths include the use of the excess wind and solar energy supply to the grid to produce hydrogen from natural gas or coal. As a contribution to this debate, here I discuss the present contribution of wind and solar to the electricity grid, how this contribution might be expanded to make a grid wind and solar only, what is the energy storage needed to permit this supply, and what is the ratio of domestic total primary energy supply to electricity use. These factors are required to determine the likeliness of producing hydrogen for export. The wind and solar energy capacity, presently at 6.7 and 11.4 GW, have to increase almost 8 times up to values of 53 and 90 GW respectively to support a wind and solar energy only electricity grid for the southeast states only. Additionally, it is necessary to build-up energy storage of actual power >50 GW and stored energy >3000 GW h to stabilize the grid. If the other states and territories are considered, and also the total primary energy supply (TPES) rather than just electricity, the wind and solar capacity must be increased of a further 6–8 times. It is concluded that it is extremely unlikely that hydrogen for export could be produced from the splitting of the water molecule by using excess wind and solar energy, and it is very unlikely that wind and solar may fully cover the local TPES needs. The most likely scenario is production hydrogen via syngas from either natural gas or coal. Production from natural gas and coal needs further development of techniques, to include CO₂ capture, a way to reuse or store CO₂, and finally, the better energy efficiency of the conversion processes. There are several challenges for using natural gas or coal to produce hydrogen with near-zero greenhouse gas emissions. Carbon capture, utilization, and storage technologies that ensure no CO₂ is released in the production process, and new technologies to separate the oxygen from the air, and in case of natural gas, the water, and the CO₂ from the combustion products, are urgently needed to make sense of the fossil fuel hydrogen production. There is no benefit from producing hydrogen from fossil fuels without addressing the CO₂ issue, as well as the fuel energy penalty issue during conversion, that is simply translating in a net loss of fuel energy with the same CO₂ emission.