H2RES,Energy planning tool for island energy systems – The case of the Island of Mljet

When it comes to the energy planning, computer programs like H₂RES are becoming valuable tools. H₂RES has been designed as support for simulation of different scenarios devised by RenewIsland methodology with specific purpose to increase integration of renewable sources and hydrogen into island energy systems. The model can use wind, solar, hydro, biomass, geothermal as renewable energy sources and fossil fuel blocks and grid connection with mainland as back up. The load in the model can be represented by hourly and deferrable electricity loads of the power system, by hourly heat load, by hydrogen load for transport and by water load depending on water consumption. The H₂RES model also has ability to integrate different storages into island energy system in order to increase the penetration of intermittent renewable energy sources or to achieve a 100% renewable island. Energy storages could vary from hydrogen loop (fuel cell, electrolyser and hydrogen storage) to reversible hydro or batteries for smaller energy systems. The H₂RES model was tested on the power system of the Island of Porto Santo – Madeira, the islands of Corvo, Graciosa, and Terrciera – Azores, Sal Island – Cape Verde, Portugal, the Island of Mljet, Croatia and on the energy system of the Malta. Beside energy planning of the islands, H₂RES model could be successfully applied for simulation of other energy systems like villages in mountain regions or for simulation of different individual energy producers or consumers.     

Analysis and techno-economic assessment of renewable hydrogen production and blending into natural gas for better sustainability

In this study, comprehensive thermodynamic analysis and techno-economic assessment studies of the renewable hydrogen production and its blending with natural gas in the existing pipelines are performed. Solar and wind energy-based on-grid and off-grid power systems are designed and compared in energy, exergy, and cost. Solar PV panels and wind turbines are particularly considered for electricity and hydrogen production for residential applications in an environmentally benign way. Fuel cell units are included to supply continuous electricity in the off-grid system. Here, the heat required for a community consisting of 100 houses is provided by hydrogen and natural gas mixture as a more environmentally benign fuel. The costs of capital, fuel, operation, and maintenance are calculated and evaluated in detail. The total net present costs are calculated as $6.95 million and $2.47 million for the off-grid and on-grid power systems, respectively. For the off-grid system, energy and exergy efficiencies are calculated as 32.64% and 40.73%, respectively. Finally, the energy and exergy efficiencies of the on-grid system are determined as 26.58% and 35.25%, respectively.     

How to achieve a 100% RES electricity supply for Portugal?

Portugal is a country with an energy system highly dependent on oil and gas imports. Imports of oil and gas accounted for 85% of the country’s requirements in 2005 and 86% in 2006. Meanwhile, the share of renewable energy sources (RES) in the total primary energy consumption was only 14% in 2006. When focusing only on electricity production, the situation is somewhat better. The share of RES in gross electricity production varies between 20% and 35% and is dependent on the hydropower production in wet and dry years. This paper presents, on a national scale, Portugal’s energy system planning and technical solutions for achieving 100% RES electricity production. Planning was based on hourly energy balance and use of H₂RES software. The H₂RES model provides the ability to integrate various types of storages into energy systems in order to increase penetration of the intermittent renewable energy sources or to achieve a 100% renewable island, region or country. The paper also represents a stepping-stone for studies offering wider possibilities in matching and satisfying electricity supply in Portugal with potential renewable energy sources. Special attention has been given to intermittent sources such as wind, solar and ocean waves that can be coupled to appropriate energy storage systems charged with surplus amounts of produced electricity. The storage systems also decrease installed power requirements for generating units. Consequently, these storages will assist in avoiding unnecessary rejection of renewable potential and reaching a sufficient security of energy supply.     

Analyzing the levelized cost of hydrogen in refueling stations with on-site hydrogen production via water electrolysis in the Italian scenario

Hydrogen refueling infrastructures with on-site production from renewable sources are an interesting solution for assuring green hydrogen with zero CO₂ emissions. The main problem of these stations development is the hydrogen cost that depends on both the plant size (hydrogen production capacity) and on the renewable source.In this study, a techno-economic assessment of on-site hydrogen refueling stations (HRS), based on grid-connected PV plants integrated with electrolysis units, has been performed. Different plant configurations, in terms of hydrogen production capacity (50 kg/day, 100 kg/day, 200 kg/day) and the electricity mix (different sharing of electricity supply between the grid and the PV plant), have been analyzed in terms of electric energy demands and costs.The study has been performed by considering the Italian scenario in terms of economic streams (i.e. electricity prices) and solar irradiation conditions.The levelized cost of hydrogen (LCOH), that is the more important indicator among the economic evaluation indexes, has been calculated for all configurations by estimating the investment costs, the operational and maintenance costs and the replacement costs.Results highlighted that the investment costs increase proportionally as the electricity mix changes from Full Grid operation (100% Grid) to Low Grid supply (25% Grid) and as the hydrogen production capacity grows, because of the increasing in the sizes of the PV plant and the HRS units. The operational and maintenance costs are the main contributor to the LCOH due to the annual cost of the electricity purchased from the grid.The calculated LCOH values range from 9.29 €/kg (200 kg/day, 50% Grid) to 12.48 €/kg (50 kg/day, 100% Grid).     

Stochastic security-constrained operation of wind and hydrogen energy storage systems integrated with price-based demand response

Because of highly increasing energy consumption, environmental issues and lack of common energy sources, the use of renewable energy sources especially wind power generation technology is increasing with significant growth in the world. But due to the variable nature of these sources, new challenges have been created in the balance between production and consumption of power system. The hydrogen energy storage (HES) system by storing excess wind power through the technology of power to hydrogen (P2H) and delivering it to the electricity network through hydrogen-based gas turbine at the required hours reduces not only wind alternation but can play an important role in balancing power production and consumption. On the other hand, power consumers by participating in demand response (DR) programs can reduce their consumption at peak load or wind power shortage hours, and increase their consumption at low-load or excess wind power hours to reduce wind power spillage and system energy cost. This paper proposes a stochastic security constrained unit commitment (SCUC) with wind energy considering coordinated operation of price-based DR and HES system. Price-based DR has been formulated as a price responsive shiftable demand bidding mechanism. The proposed model has been tested on modified 6-bus and 24-bus systems. The numerical results show the effect of simultaneous consideration of HES system and price-based DR integrated with wind energy on hourly generation scheduling of thermal units. As a result there is some reduction in wind generation power spillage and daily operation cost.     

Large-scale integration of optimal combinations of PV, wind and wave power into the electricity supply

This article presents the results of analyses of large-scale integration of wind power, photo voltaic (PV) and wave power into a Danish reference energy system. The possibility of integrating Renewable Energy Sources (RES) into the electricity supply is expressed in terms of the ability to avoid excess electricity production. The different sources are analysed in the range of an electricity production from 0 to 100% of the electricity demand. The excess production is found from detailed energy system analyses on the computer model EnergyPLAN. The analyses have taken into account that certain ancillary services are needed in order to secure the electricity supply system.The idea is to benefit from the different patterns in the fluctuations of different renewable sources. And the purpose is to identify optimal mixtures from a technical point of view. The optimal mixture seems to be when onshore wind power produces approximately 50% of the total electricity production from RES. Meanwhile, the mixture between PV and wave power seems to depend on the total amount of electricity production from RES. When the total RES input is below 20% of demand, PV should cover 40% and wave power only 10%. When the total input is above 80% of demand, PV should cover 20% and wave power 30%. Meanwhile the combination of different sources is alone far from a solution to large-scale integration of fluctuating resources. This measure is to be seen in combination with other measures such as investment in flexible energy supply and demand systems and the integration of the transport sector.     

Design and analysis of stand-alone hydrogen energy systems with different renewable sources

One of the most interesting developments of energy systems based on the utilization of hydrogen is their integration with renewable sources of energy (RES). In fact, hydrogen can operate as a storage and carrying medium of these primary sources. The design and operation of the system could change noticeably, depending on the type and availability of the primary source. In this paper, the results obtained considering a model of a stand-alone energy system supplied just with RES and composed by an electrolyzer, a hydrogen tank and a proton exchange membrane fuel cell are exposed. The energy systems have been designed in order to supply the electricity needs of a residential user in a mountain environment in Italy during a complete year. Three different sources have been considered: solar irradiance (transformed by an array of photovoltaic modules), hydraulic energy (transformed by a micro-hydro turbine in open-flume configuration) and wind speed (transformed by a small-size wind generator). It has been checked that, in that specific location, it is absolutely not convenient to use the wind source; the solar irradiance has a nearly constant availability during the year, and therefore the seasonal storage of the RES in form of hydrogen is the lowest; the availability of the micro-hydro source is less constant than in case of solar irradiance, requiring a higher hydrogen seasonal storage, but its advantage is linked to the higher efficiency of the turbine and the fact that the RES is directly sent to the user with high frequency (for these reasons it is the best plant option).     

Power-to-gas as an option for improving energy self-consumption in renewable energy communities

Renewable Energy Communities (RECs) have been introduced by the Renewable Energy European Directive (REDII) in order to allow their members to collectively produce, consume, store and sell renewable energy. With the distributed generation deployment, the electricity injection into power grids has to be limited. Thereby, the RES management has to maximise the local energy self-consumption (SC). The present work deals with Power-to-Gas (PtG) application for blending hydrogen in the local gas grid for maximising the energy-SC, comparing it with traditional electric batteries (PtP). Moreover, this study investigate how SC-based tariffs for RECs can represent an indirect incentive for hydrogen production. To do so, a case study, consisting of 200 dwellings, has been analysed. Four PV configuration have been considered for evaluating different RES excess conditions. PtP and PtG systems have been implemented and compared each other. The hydrogen production cost has been assessed exploiting the renewable electricity incentive scheme.     

Two energy system analysis models: A comparison of methodologies and results

This paper presents a comparative study of two energy system analysis models both designed for the purpose of analysing electricity systems with a substantial share of fluctuating renewable energy. The first model (EnergyPLAN) has been designed for national and regional analyses. It has been used in the design of strategies for integration of wind power and other fluctuating renewable energy sources into the future energy supply. The model has been used for investigating new operation strategies and investments in flexibility in order to utilize wind power and avoid excess production. The other model (H₂RES) has been designed for simulating the integration of renewable sources and hydrogen into island energy systems. The H₂RES model can use wind, solar and hydro as renewable energy sources and diesel blocks as backup. The latest version of the H₂RES model has an integrated grid connection with the mainland. The H₂RES model was tested on the power system of Porto Santo Island, Madeira, Portugal, Corvo and Graciosa Islands, Azores Islands, Portugal and Sal Island, Cape Verde. This paper presents the results of using the two different models on the same case, the island of Mljet, Croatia. The paper compares methodologies and results with the purpose of identifying mutual benefits and improvements of both models.     

Development of a renewable hydrogen economy: Optimization of existing technologies

There is an increasing need for new and greater sources of energy for future global transportation applications. One recognized possibility for a renewable, clean source of transportation fuels is solar radiation collected and converted into useable forms of electrical and/or chemical (hydrogen) energy. This paper describes methods for utilizing and combining existing technologies into systems that optimize solar energy collection and conversion into useful transportation fuels. Photovoltaic (PV)-electrolysis (solar hydrogen) and PV-battery charging systems described in this paper overcome inefficiencies inherent in past concepts, where DC power from the PV system was first converted to AC current and then used to power electrical devices at the point of generation, or fed back to the grid to reduce electricity costs. These past, non-optimized concepts included efficiency losses in power conversion and unnecessary costs. These drawbacks can be avoided by capitalizing on the unique feature of solar photovoltaic devices that match their maximum power point to the operating point of an electrolyzer or a battery charger without intervening power transformers. This concept is illustrated for two systems designed, built, and tested by General Motors for fueling a fuel cell electric vehicle and charging an automotive propulsion battery. Based on this research, we propose a scenario in which individual home-owners, businesses, or sites at remote locations with no grid electricity, can capture solar energy, store it as hydrogen generated via water electrolysis, or as electrical energy used to charge storage batteries. Such a decentralized energy system provides a home refueling option for drivers who only travel limited distances each day.     

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.     

Design of hybrid power-to-power systems for continuous clean PV-based energy supply

The increasing penetration of intermittent renewable sources, fostering power sector decarbonization, calls for the adoption of energy storage systems as an essential mean to improve local electricity exploitation, reducing the impact of distributed power generation on the electric grid. This work compares the use of hydrogen-based Power-to-Power systems, battery systems and hybrid hydrogen-battery systems to supply a constant 1 MW_el load with electricity locally generated by a photovoltaic plant. A techno-economic optimization model is set up that optimizes the size and annual operation of the system components (photovoltaic field, electrolyzer, hydrogen storage tanks, fuel cell and batteries) with the objective of minimizing the annual average cost of electricity, while guaranteeing an imposed share of local renewable self-generation. Results show that, with the present values of investment costs and grid electricity prices, the installation of an energy storage system is not economically attractive by itself, whereas the installation of PV panels is beneficial in terms of costs, so that the baseline optimal solution consists of a 4.2 MW_p solar field capable to self-generate 33% of the load annually. For imposed shares of self-generation above 40%, decoupling generation and consumption becomes necessary. The use of batteries is slightly less expensive than the use of hydrogen storage systems up to a 92% self-generation rate. Above this threshold, seasonal storage becomes predominant and hybrid storage becomes cheaper than batteries. The sale of excess electricity is always important to support the plant economics, and a sale price reduction sensibly impacts the results. Hydrogen storage becomes more competitive when the need for medium and long terms energy shift increases, e.g. in case of having a cap on the available PV capacity.     

The economics and the environmental benignity of different colors of hydrogen

Due to the increasing greenhouse gas emissions, as well as due to the rapidly increasing use of renewable energy sources in the electricity generation over the last years, interest in hydrogen is rising again. Hydrogen can be used as a storage for renewable energy balancing the whole energy systems, and contributing to the decarbonization of the energy system, especially of the industry and the transport sector.The major objective of this paper is to discuss various ways of hydrogen production depending on the primary energy sources used. Moreover, the economic and environmental performance of three major hydrogen colors, as well as major barriers for faster deployment in fuel cell vehicles, are analyzed.The major conclusion is that the full environmental benefits of hydrogen use are highly dependent on the hydrogen production methods and primary sources used. Only green hydrogen with electricity from wind, PV and hydro has truly low emissions. All other sources like blue hydrogen with CCUS or electrolysis using the electricity grid have substantially higher emissions, coming close to grey hydrogen production. Another conclusion is that it is important to introduce an international market for hydrogen to lower costs and to produce hydrogen where conditions are best.Finally, the major open question remaining is whether – including all external costs of all energy carriers, hydrogen of any color may become economically competitive in any sector of the energy system. The future success of hydrogen is very dependent on technological development and resulting cost reductions, as well as on future priorities and the corresponding policy framework. The policy framework should support the shift from grey to green hydrogen.     

Estimating global production and supply costs for green hydrogen and hydrogen-based green energy commodities

Green energy commodities are expected to be central in decarbonising the global energy system. Such green energy commodities could be hydrogen or other hydrogen-based energy commodities produced from renewable energy sources (RES) such as solar or wind energy. We quantify the production cost and potentials of hydrogen and hydrogen-based energy commodities ammonia, methane, methanol, gasoline, diesel and kerosene in 113 countries. Moreover, we evaluate total supply costs to Germany, considering both pipeline-based and maritime transport. We determine production costs by optimising the investment and operation of commodity production from dedicated RES based on country-level RES potentials and country-specific weighted average costs of capital. Analysing the geographic distribution of production and supply costs, we find that production costs dominate the supply cost composition for liquid or easily liquefiable commodities, while transport costs dominate for gaseous commodities. In the case of Germany, importing green ammonia could be more cost-efficient than domestic production from locally produced or imported hydrogen. Green ammonia could be supplied to Germany from many regions worldwide at below the cost of domestic production, with costs ranging from 624 to 874 $/t NH₃ and Norway being the cheapest supplier. Ammonia production using imported hydrogen from Spain could be cost-effective if a pan-European hydrogen pipeline grid based on repurposed natural gas pipelines exists.     

Energy prosumerism using photovoltaic power plant and hydrogen combustion engine: Energy and thermo-ecological assessment

Renewable Energy Sources (RES) represent an attractive way to save natural resources and improve the overall impact of power systems on the environment. A continuous increase of share of RES in national energy mixes is observed, and due to the energy policy of the European Union and many other countries, further increase is expected. A disadvantage of RES is their random, weather-dependent availability, which requires energy storage. A promising method of integrating RES with the energy system is the use of hydrogen as an energy carrier (e.g. coupling RES with electrolyzers in order to directly use the renewable electricity for production of hydrogen). In the present work, a simulation of cooperation of a photovoltaic power plant with a gas piston engine fueled by hydrogen was performed, with and without the presence of energy storage. The aim of the analysis is twofold. First, the “compensation losses” due to forced part-load operation of the engine coupled with RES are evaluated and compared with “storage losses” resulting from the thermodynamic imperfectness of the storage; this allows to calculate the minimum round-trip efficiency of storage required for positive energy effect. The “compensation losses” have been determined to be of the order of magnitude of 2%, and the minimum round-trip efficiency of storage to be at the level of 85%. Second, a thermo-ecological analysis was carried out to determine the impact of the source of hydrogen on the overall ecological effectiveness of the system. Contrary to the commonly used measure of “energy efficiency” describing a local balance boundary, thermo-ecological cost (TEC) evaluates the consumption of non-renewable exergy within a global balance boundary. The analysis confirmed that comparing various hydrogen production methods (especially renewable and non-renewable) in terms of local energy efficiency is inadequate, because it does not tell much about their sustainability. For a hydrogen energy system basing on the water electrolysis – hydrogen transport/storage – combustion in a gas piston engine pathway to be considered sustainable, the input electricity to the electrolysis process should be characterized by TEC lower than ∼0.15 J1/J, a value which even some renewable energy sources fail to achieve.     

Integration of large-scale hydrogen storages in a low-carbon electricity generation system

This study investigates the overall feasibility of large energy storages with hydrogen as energy carrier onsite with a pre-combustion carbon capture and storage coal gasification plant and assesses the general impacts of such a backup installation on an electricity generation system with high wind power portion. The developed system plant configuration consists of four main units namely the gasification unit, main power unit, backup power unit including hydrogen storage and ancillary power unit. Findings show that integrating a backup storage in solid or gaseous hydrogen storage configuration allows to store excessive energy under high renewable power output or low demand and to make use of the stored energy to compensate low renewable output or high power demand. The study concludes that the developed system configuration reaches much higher load factors and efficiency levels than a plant configuration without backup storage, which simply increases its power unit capacity to meet the electricity demand. Also from an economical point of view, the suggested system configurations are capable to achieve lower electricity generation costs.     

An investigation of optimum PV and wind energy system capacities for alternate short and long‐term energy storage sizing methodologies

The goal of this study is to find the optimal sizes of renewable energy systems (RES) based on photovoltaic (PV) and/or wind systems for three energy storage system (ESS) scenarios in a micro‐grid; (1) with pumped hydro storage (PHS) as a long‐term ESS, (2) with batteries as a short‐term ESS, and (3) without ESS. The PV and wind sizes are optimally determined to accomplish the maximum annual RES fraction (F_RES ) with electricity cost lower than or equal to the utility tariff. Furthermore, the effect of the use of battery and PHS on the electricity cost and F_RES are studied. A university campus on a Mediterranean island is selected as a case study. The results show that PV‐wind hybrid system of 8 MW wind and 4.2 MW PV with 89.5 MWh PHS has the highest F_RES of 88.0%, and the highest demand supply fraction as 42.6%. Moreover, the results indicate that the economic and technical parameters of RESs are affected significantly by the use of ESSs depending on the type and the capacity of both the RES and the ESS.     

Feasibility study of renewable energy sources for developing the hydrogen economy in Pakistan

Hydrogen energy can play a pivotal part in enhancing energy security and decreasing hazardous emissions in Pakistan. However, hydrogen energy can be sustainable and clean only if it is produced from renewable energy sources (RES). Therefore, this study conducts feasibility of six RES for the generation of hydrogen in Pakistan. RES evaluated in this study include wind, solar, biomass, municipal solid waste (MSW), geothermal, and micro-hydro. RES have been evaluated using Fuzzy Delphi, fuzzy analytical hierarchy process (FAHP), and environmental data envelopment analysis (DEA). Fuzzy Delphi finalizes criteria and sub-criteria. FAHP obtains relative weights of criteria considered for choosing the optimal RES. Environmental DEA measures relative efficiency of each RES using criteria weights as outputs, and RES-based electricity generation cost as input. The results revealed wind as the most efficient source of hydrogen production in Pakistan. Micro-hydro and Solar energy can also be used for hydrogen production. Biomass, MSW, and geothermal achieved less efficiency scores and therefore are not suggested at present.     

Integration of hydrogen storage system and wind generation in power systems under demand response program: A novel p-robust stochastic programming

Penetration of renewable energy sources (RESs) in power systems increase all over the world to overcome current challenges, most importantly environmental issues. Beside advantages of RESs, their integration into the power systems have imposed various challenges considering uncertain and intermitted power output. To cope with these challenges, utilizing energy storage systems with renewable energy sources alongside the demand response (DR) programs are considered as reliable solutions. On the other hand, in an uncertain environment, minimizing worst-case cost or regret is counted as an important criterion to evaluate operation of any system under uncertain parameters. Therefore, in this paper, optimal operation of power systems is solved under penetration of wind turbines, hydrogen storage system, and DR programs in an uncertain environment. To guarantee robust operation of the system under the worst-case scenario, a novel stochastic p-robust optimization method (SPROM) is proposed which combines both stochastic programming and robust optimization approaches where minimizes the worst-case cost or regret level. The performance of the developed model is evaluated considering a six-bus test system under two cases as stochastic optimization (SO) and SPROM. Obtained results show that the maximum regret level is reduced considerably using the proposed SPROM comparing with pure stochastic method.     

Dynamic hydrogen production from PV & wind direct electricity supply – Modeling and techno-economic assessment

Renewable hydrogen from water electrolysis could contribute to the defossilization of various energy intensive sectors but continues to suffer from unfavorable economics. Attention is being paid to the direct supply of renewable electricity to electrolyzers; in particular from photovoltaic (PV) and wind units, whose fixed remuneration period has expired. However, detailed analysis of such operating strategies via modeling and simulation of the dynamic behavior of alkaline electrolysis (AEL) and polymer electrolyte membrane electrolysis (PEMEL) is lacking. In this work, an electrolyzer model is developed for both AEL and PEMEL and analyzed for PV and wind power input data sets from the region of northwest Germany. It is shown that key performance indicators (KPI) such as hydrogen production efficiency, electricity utilization rate, product output and net production costs are highly reliant on the shape of transient power input signals as well as the electrolyzers ability to cope with them. PEMEL technology generally has higher electricity utilization rates than AEL, while AEL still achieves relatively large hydrogen production quantities due to its higher efficiency. Thus, the better operational flexibility of PEMEL cannot generally be considered advantageous in terms of hydrogen production quantities – the same applies for economics. The most competitive hydrogen production costs were 4.33 € per kg for the AEL technology with direct electricity supply from old wind farms, which no longer receive fixed remuneration.