Switzerland
Hydrogen: The Future Energy Carrier
Jul 2010
Publication
Since the beginning of the twenty-first century the limitations of the fossil age with regard to the continuing growth of energy demand the peaking mining rate of oil the growing impact of CO2 emissions on the environment and the dependency of the economy in the industrialized world on the availability of fossil fuels became very obvious. A major change in the energy economy from fossil energy carriers to renewable energy fluxes is necessary. The main challenge is to efficiently convert renewable energy into electricity and the storage of electricity or the production of a synthetic fuel. Hydrogen is produced from water by electricity through an electrolyser. The storage of hydrogen in its molecular or atomic form is a materials challenge. Some hydrides are known to exhibit a hydrogen density comparable to oil; however these hydrides require a sophisticated storage system. The system energy density is significantly smaller than the energy density of fossil fuels. An interesting alternative to the direct storage of hydrogen are synthetic hydrocarbons produced from hydrogen and CO2 extracted from the atmosphere. They are CO2 neutral and stored like fossil fuels. Conventional combustion engines and turbines can be used in order to convert the stored energy into work and heat.
Link to document download on Royal Society Website
Link to document download on Royal Society Website
Hydrogen Production from Natural Gas and Biomethane with Carbon Capture and Storage – A Techno-environmental Analysis
Mar 2020
Publication
This study presents an integrated techno-environmental assessment of hydrogen production from natural gas and biomethane combined with CO2 capture and storage (CCS). We have included steam methane reforming (SMR) and autothermal reforming (ATR) for syngas production. CO2 is captured from the syngas with a novel vacuum pressure swing adsorption (VPSA) process that combines hydrogen purification and CO2 separation in one cycle. As comparison we have included cases with conventional amine-based technology. We have extended standard attributional Life Cycle Assessment (LCA) following ISO standards with a detailed carbon balance of the biogas production process (via digestion) and its by-products. The results show that the life-cycle greenhouse gas (GHG) performance of the VPSA and amine-based CO2 capture technologies is very similar as a result of comparable energy consumption. The configuration with the highest plant-wide CO2 capture rate (almost 100% of produced CO2 captured) is autothermal reforming with a two-stage water-gas shift and VPSA CO2 capture – because the latter has an inherently high CO2 capture rate of 98% or more for the investigated syngas. Depending on the configuration the addition of CCS to natural gas reforming-based hydrogen production reduces its life-cycle Global Warming Potential by 45–85 percent while the other environmental life-cycle impacts slightly increase. This brings natural gas-based hydrogen on par with renewable electricity-based hydrogen regarding impacts on climate change. When biomethane is used instead of natural gas our study shows potential for net negative greenhouse gas emissions i.e. the net removal of CO2 over the life cycle of biowaste-based hydrogen production. In the special case where the biogas digestate is used as agricultural fertiliser and where a substantial amount of the carbon in the digestate remains in the soil the biowaste-based hydrogen reaches net-negative life cycle greenhouse gas emissions even without the application of CCS. Addition of CCS to biomethane-based hydrogen production leads to net-negative emissions in all investigated cases.
Potential for Hydrogen Production from Sustainable Biomass with Carbon Capture and Storage
Jan 2022
Publication
Low-carbon hydrogen is an essential element in the transition to net-zero emissions by 2050. Hydrogen production from biomass is a promising bio-energy with carbon capture and storage (BECCS) scheme that could produce low-carbon hydrogen and generate the carbon dioxide removal (CDR) envisioned to be required to offset hard-to-abate emissions. Here we design a BECCS supply chain for hydrogen production from biomass with carbon capture and storage and quantify at high spatial resolution the technical potential for hydrogen production and CDR in Europe. We consider sustainable biomass feedstocks that have minimal impacts on food security and biodiversity namely agricultural residues and waste. We find that this BECCS supply chain can produce up to 12.5 Mtons of H2 per year (currently ~10 Mtons of H2 per year are used in Europe) and remove up to 133 Mtons CO2 per year from the atmosphere (or 3% of European total greenhouse gas emissions). We then perform a geospatial analysis to quantify transportation distances between where biomass feedstocks are located and potential hydrogen users and find that 20% of hydrogen potential is located within 25 km from hard-toelectrify industries. We conclude that BECCS supply chains for hydrogen production from biomass represent an overlooked near-term opportunity to generate carbon dioxide removal and low-carbon hydrogen.
Seasonal Energy Storage in Aluminium for 100 Percent Solar Heat and Electricity Supply
Sep 2019
Publication
In order to reduce anthropogenic global warming governments around the world have decided to reduce CO2 emissions from fossil fuels dramatically within the next decades. In moderate and cold climates large amounts of fossil fuels are used for space heating and domestic hot water production in winter. Although on an annual base solar energy is available in large quantities in these regions least of the solar resource is available in winter when most of the energy is needed. Therefore solutions are needed to store and transfer renewable energy from summer to winter. In this paper a seasonal energy storage based on the aluminium redox cycle (Al3+→Al→ Al3+) is proposed. For charging electricity from solar or other renewable sources is used to convert aluminium oxide or aluminium hydroxide to elementary aluminium (Al3+→Al). In the discharging process aluminium is oxidized (Al→Al3+) releasing hydrogen heat and aluminium hydroxide or aluminium oxide as a by-product. Hydrogen is used in a fuel cell to produce electricity. Heat produced from the aluminium oxidation process and by the fuel cell is used for domestic hot water production and space heating. The chemical reactions and energy balances are presented and simulation results are shown for a system that covers the entire energy demand for electricity space heating and domestic hot water of a new multi-family building with rooftop photovoltaic energy in combination with the seasonal Al energy storage cycle. It shows that 7–11 kWp of photovoltaic installations and 350–530 kg Al would be needed per apartment for different Swiss climates. Environmental life cycle data shows that the global warming potential and non-renewable primary energy consumption can be reduced significantly compared to today's common practice of heating with natural gas and using electricity from the ENTSO-E network. The presumptive cost were estimated and indicate a possible cost-competitiveness for this system in the near future.
Molecular Transport Effects of Hydrocarbon Addition on Turbulent Hydrogen Flame Propagation
Sep 2007
Publication
We analytically investigated the influence of light hydrocarbons on turbulent premixed H2/air atmospheric flames under lean conditions in view of safe handling of H2 systems applications in H2 powered IC engines and gas turbines and also with an orientation towards modelling of H2 combustion. For this purpose an algebraic flame surface wrinkling model included with pressure and fuel type effects is used. The model predictions of turbulent premixed flames are compared with the set of corresponding experimental data of Kido et al. (Kido Nakahara et al. 2002). These expanding spherical flame data include H2–air mixtures doped with CH4 and C3H8 while the overall equivalence ratio of all the fuel/air mixtures is fixed at 0.8 for constant unstretched laminar flame speed of 25 cm/s by varying N2 composition. The model predictions show that there is little variation in turbulent flame speed ST for C3H8 additions up to 20-vol%. However for 50 vol% doping flame speed decreases by as much as 30 % from 250 cm/s that of pure H2–air mixtures for turbulence intensity of 200 cm/s. With respect to CH4 for 50 vol% doping ST reduces by only 6 % cf. pure H2/air mixture. In the first instance the substantial decrease of ST with C3H8 addition may be attributed to the increase in the Lewis number of the dual-fuel mixture and proportional restriction of molecular mobility of H2. That is this decrease in flame speed can be explained using the concept of leading edges of the turbulent flame brush (Lipatnikov and Chomiak 2005). As these leading edges have mostly positive curvature (convex to the unburned side) preferential-diffusive-thermal instabilities cause recognizable impact on flame speed at higher levels of turbulence with the effect being very strong for lean H2 mixtures. The lighter hydrocarbon substitutions tend to suppress the leading flame edges and possibly transition to detonation in confined structures and promote flame front stability of lean turbulent premixed flames. Thus there is a necessity to develop a predictive reaction model to quantitatively show the strong influence of molecular transport coefficients on ST.
The Potential of Gas Switching Partial Oxidation Using Advanced Oxygen Carriers for Efficient H2 Production with Inherent CO2 Capture
May 2021
Publication
The hydrogen economy has received resurging interest in recent years as more countries commit to net-zero CO2 emissions around the mid-century. “Blue” hydrogen from natural gas with CO2 capture and storage (CCS) is one promising sustainable hydrogen supply option. Although conventional CO2 capture imposes a large energy penalty advanced process concepts using the chemical looping principle can produce blue hydrogen at efficiencies even exceeding the conventional steam methane reforming (SMR) process without CCS. One such configuration is gas switching reforming (GSR) which uses a Ni-based oxygen carrier material to catalyze the SMR reaction and efficiently supply the required process heat by combusting an off-gas fuel with integrated CO2 capture. The present study investigates the potential of advanced La-Fe-based oxygen carrier materials to further increase this advantage using a gas switching partial oxidation (GSPOX) process. These materials can overcome the equilibrium limitations facing conventional catalytic SMR and achieve direct hydrogen production using a water-splitting reaction. Results showed that the GSPOX process can achieve mild efficiency improvements relative to GSR in the range of 0.6–4.1%-points with the upper bound only achievable by large power and H2 co-production plants employing a highly efficient power cycle. These performance gains and the avoidance of toxicity challenges posed by Ni-based oxygen carriers create a solid case for the further development of these advanced materials. If successful results from this work indicate that GSPOX blue hydrogen plants can outperform an SMR benchmark with conventional CO2 capture by more than 10%-points both in terms of efficiency and CO2 avoidance.
Power-to-fuels Via Solid-oxide Electrolyzer: Operating Window and Techno-economics
May 2019
Publication
Power-to-fuel systems via solid-oxide electrolysis are promising for storing excess renewable electricity by efficient electrolysis of steam (or co-electrolysis of steam and CO2) into hydrogen (or syngas) which can be further converted into synthetic fuels with plant-wise thermal integration. Electrolysis stack performance and durability determine the system design performance and long-term operating strategy; thus solid-oxide electrolyzer based power-to-fuels were investigated from the stack to system levels. At the stack level the data from a 6000-h stack testing under laboratory isothermal conditions were used to calibrate a quasi-2D model which enables to predict practical isothermal stack performance with reasonable accuracy. Feasible stack operating windows meeting various design specifications (e.g. specific syngas composition) were further generated to support the selection of operating points. At the system level with the chosen similar stack operating points various power-to-fuel systems including power-to-hydrogen power-to-methane power-to-methanol (dimethyl ether) and power-to-gasoline were compared techno-economically considering system-level heat integration. Several operating strategies of the stack were compared to address the increase in stack temperature due to degradation. The modeling results show that the system efficiency for producing H2 methane methanol/dimethyl ether and gasoline decreases sequentially from 94% (power-to-H2) to 64% (power-to-gasoline) based on a higher heating value. Co-electrolysis which allows better heat integration can improve the efficiency of the systems with less exothermic fuel-synthesis processes (e.g. methanol/dimethyl ether) but offers limited advantages for power-to-methane and power-to-gasoline systems. In a likely future scenario where the growing amount of electricity from renewable sources results in increasing periods of a negative electricity price solid oxide electrolyser based power-to-fuel systems are highly suitable for levelling the price fluctuations in an economic way.
Optimal Hydrogen Production in a Wind-dominated Zero-emission Energy System
May 2021
Publication
The role of hydrogen in future energy systems is widely acknowledged: from fuel for difficult-to-decarbonize applications to feedstock for chemicals synthesis to energy storage for high penetration of undispatchable renewable electricity. While several literature studies investigate such energy systems the details of how electrolysers and renewable technologies optimally behave and interact remain an open question. With this work we study the interplay between (i) renewable electricity generation through wind and solar (ii) electricity storage in batteries (iii) electricity storage via Power-to-H2 and (iv) hydrogen commodity demand. We do so by designing a cost-optimal zero-emission energy system and use the Netherlands as a case study in a mixed integer linear model with hourly resolution for a time horizon of one year. To account for the significant role of wind we also provide an elaborate approach to model broad portfolios of wind turbines. The results show that if electrolyzers can operate flexibly batteries and power-to-H2-to-power are complementary with the latter using renewable power peaks and the former using lower renewable power outputs. If the operating modes of the power-to-H2-to-power system are limited - artificially or technically - the competitive advantage over batteries decreases. The preference of electrolyzers for power peaks also leads to an increase in renewable energy utilization for increased levels of operation flexibility highlighting the importance of capturing this feature both from a technical and a modeling perspective. When adding a commodity hydrogen demand the amount of hydrogen converted to electricity decreases hence decreasing its role as electricity storage medium.
Enabling Low-carbon Hydrogen Supply Chains Through Use of Biomass and Carbon Capture and Storage: A Swiss Case Study
Jul 2020
Publication
This study investigates the optimal design of low-carbon hydrogen supply chains on a national scale. We consider hydrogen production based on several feedstocks and energy sources namely water with electricity natural gas and biomass. When using natural gas we couple hydrogen production with carbon capture and storage. The design of the hydrogen biomass and carbon dioxide (CO2 ) infrastructure is performed by solving an optimization problem that determines the optimal selection size and location of the hydrogen production technologies and the optimal structure of the hydrogen biomass and CO2 O2 networks. First we investigate the rationale behind the optimal design of low-carbon hydrogen supply chains by referring to an idealized system configuration and by performing a parametric analysis of the most relevant design parameters of the supply chains such as biomass availability. This allows drawing general conclusions independent of any specific geographic features about the minimum-cost and minimum-emissions system designs and network structures. Moreover we analyze the Swiss case study to derive specific guidelines concerning the design of hydrogen supply chains deploying carbon capture and storage. We assess the impact of relevant design parameters such as location of CO2 storage facilities techno-economic features of CO2 capture technologies and network losses on the optimal supply chain design and on the competition between the hydrogen and CO2 networks. Findings highlight the fundamental role of biomass (when available) and of carbon capture and storage for decarbonizing hydrogen supply chains while transitioning to a wider deployment of renewable energy sources.
Comparative Life Cycle Assessment of Hydrogen-fuelled Passenger Cars
Feb 2021
Publication
In order to achieve gradual but timely decarbonisation of the transport sector it is essential to evaluate which types of vehicles provide a suitable environmental performance while allowing the use of hydrogen as a fuel. This work compares the environmental life-cycle performance of three different passenger cars fuelled by hydrogen: a fuel cell electric vehicle an internal combustion engine car and a hybrid electric vehicle. Besides two vehicles that use hydrogen in a mixture with natural gas or gasoline were considered. In all cases hydrogen produced by wind power electrolysis was assumed. The resultant life-cycle profiles were benchmarked against those of a compressed natural gas car and a hybrid electric vehicle fed with natural gas. Vehicle infrastructure was identified as the main source of environmental burdens. Nevertheless the three pure hydrogen vehicles were all found to be excellent decarbonisation solutions whereas vehicles that use hydrogen mixed with natural gas or gasoline represent good opportunities to encourage the use of hydrogen in the short term while reducing emissions compared to ordinary vehicles.
Life Cycle Assessment of Substitute Natural Gas Production from Biomass and Electrolytic Hydrogen
Feb 2021
Publication
The synthesis of a Substitute Natural Gas (SNG) that is compatible with the gas grid composition requirements by using surplus electricity from renewable energy sources looks a favourable solution to store large quantities of electricity and to decarbonise the gas grid network while maintaining the same infrastructure. The most promising layouts for SNG production and the conditions under which SNG synthesis reduces the environmental impacts if compared to its fossil alternative is still largely untapped. In this work six different layouts for the production of SNG and electricity from biomass and fluctuating electricity are compared from the environmental point of view by means of Life Cycle Assessment (LCA) methodology. Global Warming Potential (GWP) Cumulative Energy Demand (CED) and Acidification Potential (AP) are selected as impact indicators for this analysis. The influence of key LCA methodological aspects on the conclusions is also explored. In particular two different functional units are chosen: 1 kg of SNG produced and 1 MJ of output energy (SNG and electricity). Furthermore different approaches dealing with co-production of electricity are also applied. The results show that the layout based on hydrogasification has the lowest impacts on all the considered cases apart from the GWP and the CED with SNG mass as the functional unit and the avoided burden approach. Finally the selection of the multifunctionality approach is found to have a significant influence on technology ranking.
Calibration of Hydrogen Coriolis Flow Meters Using Nitrogen and Air and Investigation of the Influence of Temperature on Measurement Accuracy
Feb 2021
Publication
The performance of four Coriolis flow meters designed for use in hydrogen refuelling stations was evaluated with air and nitrogen by three members of the MetroHyVe JRP consortium; NEL METAS and CESAME EXADEBIT.<br/>A wide range of conditions were tested overall with gas flow rates ranging from (0.05–2) kg/min and pressures ranging from (20–86) bar. The majority of tests were conducted at nominal pressures of either 20 bar or 40 bar in order to match the density of hydrogen at 350 bar and 20 °C or 700 bar and −40 °C. For the conditions tested pressure did not have a noticeable influence on meter performance.<br/>When the flow meters were operated at ambient temperatures and within the manufacturer's recommended flow rate ranges errors were generally within ±1%. Errors within ±0.5% were achievable for the medium to high flow rates.<br/>The influence of temperature on meter performance was also studied with testing under both stable and transient conditions and temperatures as low as −40 °C.<br/>When the tested flow meters were allowed sufficient time to reach thermal equilibrium with the incoming gas temperature effects were limited. The magnitude and spread of errors increased but errors within ±2% were achievable at moderate to high flow rates. Conversely errors as high as 15% were observed in tests where logging began before temperatures stabilised and there was a large difference in temperature between the flow meter and the incoming gas.<br/>One of the flow meters tested with nitrogen was later installed in a hydrogen refuelling station and tested against the METAS Hydrogen Field Test Standard (HFTS). Under these conditions errors ranged from 0.47% to 0.91%. Testing with nitrogen at the same flow rates yielded errors of −0.61% to −0.82%.
A Cost Estimation for CO2 Reduction and Reuse by Methanation from Cement Industry Sources in Switzerland
Feb 2018
Publication
The Swiss government has signed the Paris Climate Agreement and various measures need to be implemented in order to reach the target of a 50% reduction in CO2 emissions in Switzerland by 2030 compared with the value for 1990. Considering the fact that the production of cement in Switzerland accounts around 2.5 million ton for CO2 emissions of which corresponds to roughly 7% of the country's total CO2 emissions the following article examines how this amount could be put to meaningful use in order to create a new value-added chain through CO2 methanation and thus reduce the consumption and import of fossil fuels in Switzerland. With power-to-gas technology this CO2 along with regenerative hydrogen from photovoltaics can be converted into methane which can then be fed into the existing natural-gas grid. This economic case study shows a cost prediction for conversion of all the CO2 from the cement industry into methane by using the technologies available today in order to replacing fossil methane imports.
Uncovering the True Cost of Hydrogen Production Routes Using Life Cycle Monetisation
Oct 2020
Publication
Hydrogen has been identified as a potential energy vector to decarbonise the transport and chemical sectors and achieve global greenhouse gas reduction targets. Despite ongoing efforts hydrogen technologies are often assessed focusing on their global warming potential while overlooking other impacts or at most including additional metrics that are not easily interpretable. Herein a wide range of alternative technologies have been assessed to determine the total cost of hydrogen production by coupling life-cycle assessments with an economic evaluation of the environmental externalities of production. By including monetised values of environmental impacts on human health ecosystem quality and resources on top of the levelised cost of hydrogen production an estimation of the “real” total cost of hydrogen was obtained to transparently rank the alternative technologies. The study herein covers steam methane reforming (SMR) coal and biomass gasification methane pyrolysis and electrolysis from renewable and nuclear technologies. Monetised externalities are found to represent a significant percentage of the total cost ultimately altering the standard ranking of technologies. SMR coupled with carbon capture and storage emerges as the cheapest option followed by methane pyrolysis and water electrolysis from wind and nuclear. The obtained results identify the “real” ranges for the cost of hydrogen compared to SMR (business as usual) by including environmental externalities thereby helping to pinpoint critical barriers for emerging and competing technologies to SMR.
Dynamic System Modeling of Thermally-integrated Concentrated PV-electrolysis
Feb 2021
Publication
Understanding the dynamic response of a solar fuel processing system utilizing concentrated solar radiation and made of a thermally-integrated photovoltaic (PV) and water electrolyzer (EC) is important for the design development and implementation of this technology. A detailed dynamic non-linear process model is introduced for the fundamental system components (i.e. PV EC pump etc.) in order to investigate the coupled system behavior and performance synergy notably arising from the thermal integration. The nominal hydrogen production power is ∼2 kW at a hydrogen system efficiency of 16–21% considering a high performance triple junction III-V PV module and a proton exchange membrane EC. The device operating point relative to the maximum power point of the PV was shown to have a differing influence on the system performance when subject to temperature changes. The non-linear coupled behavior was characterised in response to step changes in water flowrate and solar irradiance and hysteresis of the current-voltage operating point was demonstrated. Whilst the system responds thermally to changes in operating conditions in the range of 0.5–2 min which leads to advantageously short start-up times a number of control challenges are identified such as the impact of pump failure electrical PV-EC disconnection and the potentially damaging accentuated temperature rise at lower water flowrates. Finally the simulation of co-generation of heat and hydrogen for various operating conditions demonstrates the significant potential for system efficiency enhancements and the required development of control strategies for demand matching is discussed.
Magnetic Field Enhancement of Electrochemical Hydrogen Evolution Reaction Probed by Magneto-optics
Nov 2020
Publication
External magnetic fields affect various electrochemical processes and can be used to enhance the efficiency of the electrochemical water splitting reaction. However the driving forces behind this effect are poorly understood due to the analytical challenges of the available interface-sensitive techniques. Here we present a set-up based on magneto- and electro-optical probing which allows to juxtapose the magnetic properties of the electrode with the electrochemical current densities in situ at various applied potentials and magnetic fields. On the example of an archetypal hydrogen evolution catalyst Pt (in a form of Co/Pt superlattice) we provide evidence that a magnetic field acts on the electrochemical double layer affecting the local concentration gradient of hydroxide ions which simultaneously affects the magneto-optical and magnetocurrent response.
Critical Materials for Water Electrolysers at the Example of the Energy Transition in Germany
Feb 2021
Publication
The present work aims to identify critical materials in water electrolysers with potential future supply constraints. The expected rise in demand for green hydrogen as well as the respective implications on material availability are assessed by conducting a case study for Germany. Furthermore the recycling of end‐of‐life (EoL) electrolysers is evaluated concerning its potential in ensuring the sustainable supply of the considered materials. As critical materials bear the risk of raising production costs of electrolysers substantially this article examines the readiness of this technology for industrialisation from a material perspective. Except for titanium the indicators for each assessed material are scored with a moderate to high (platinum) or mostly high (iridium scandium and yttrium) supply risk. Hence the availability of these materials bears the risk of hampering the scale‐up of electrolysis capacity. Although conventional recycling pathways for platinum iridium and titanium already exist secondary material from EoL electrolysers will not reduce the dependence on primary resources significantly within the period under consideration—from 2020 until 2050. Notably the materials identified as critical are used in PEM and high temperature electrolysis whereas materials in alkaline electrolysis are not exposed to significant supply risks.
Mobility from Renewable Electricity: Infrastructure Comparison for Battery and Hydrogen Fuel Cell Vehicles
May 2018
Publication
This work presents a detailed breakdown of the energy conversion chains from intermittent electricity to a vehicle considering battery electric vehicles (BEVs) and fuel cell electric vehicles (FCEVs). The traditional well-to-wheel analysis is adapted to a grid to mobility approach by introducing the intermediate steps of useful electricity energy carrier and on-board storage. Specific attention is given to an effective coupling with renewable electricity sources and associated storage needs. Actual market data show that compared to FCEVs BEVs and their infrastructure are twice as efficient in the conversion of renewable electricity to a mobility service. A much larger difference between BEVs and FCEVs is usually reported in the literature. Focusing on recharging events this work additionally shows that the infrastructure efficiencies of both electric vehicle (EV) types are very close with 57% from grid to on-board storage for hydrogen refilling stations and 66% for fast chargers coupled with battery storage. The transfer from the energy carrier at the station to on-board storage in the vehicle accounts for 9% and 12% of the total energy losses of these two modes respectively. Slow charging modes can achieve a charging infrastructure efficiency of 78% with residential energy storage systems coupled with AC chargers.
Measurement Challenges for Hydrogen Vehicles
Apr 2019
Publication
Uptake of hydrogen vehicles is an ideal solution for countries that face challenging targets for carbon dioxide reduction. The advantage of hydrogen fuel cell electric vehicles is that they behave in a very similar way to petrol engines yet they do not emit any carbon containing products during operation. The hydrogen industry currently faces the dilemma that they must meet certain measurement requirements (set by European legislation) but cannot do so due to a lack of available methods and standards. This paper outlines the four biggest measurement challenges that are faced by the hydrogen industry including flow metering quality assurance quality control and sampling.
Feasibility of Renewable Hydrogen Based Energy Supply for a District
Sep 2017
Publication
Renewable generation technologies (e.g. photovoltaic panels (PV)) are often installed in buildings and districts with an aim to decrease their carbon emissions and consumption of non-renewable energy. However due to a mismatch between supply and demand at an hourly but also on a seasonal timescale; a large amount of electricity is exported to the grid rather than used to offset local demand. A solution to this is local storage of electricity for subsequent self-consumption. This could additionally provide districts with new business opportunities financial stability flexibility and reliability.<br/>In this paper the feasibility of hydrogen based electricity storage for a district is evaluated. The district energy system (DES) includes PV and hybrid photovoltaic panels (PVT). The proposed storage system consists of production of hydrogen using the renewable electricity generated within the district hydrogen storage and subsequent use in a fuel cell. Combination of battery storage along with hydrogen conversion and storage is also evaluated. A multi-energy optimization approach is used to model the DES. Results of the model are optimal battery capacity electrolyzer capacity hydrogen storage capacity fuel cell capacity and energy flows through the system. The model is also used to compare different system design configurations. The results of this analysis show that both battery capacity and conversion of electricity to hydrogen enable the district to decrease its carbon emissions by approximately 22% when compared to the reference case with no energy storage.
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