Decarbonizing the energy supply is essential if climate targets are to be met. The issue of gas and heating supplies has again become a focus of public concern, not least because of the ongoing gas supply crisis triggered by the conflict in Ukraine. In the near term, measures are being discussed that will save energy at all levels and particularly for domestic and commercial customers. But that’s not all. The structural changes that are needed to transform the heating sector and decarbonize the energy supply to buildings are also taking center stage in the current debate.
It’s within this context that heat pumps have been singled out as a key technology for achieving net-zero space heating. However, there has also been repeated talk of green hydrogen offering a possible solution.
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While up until now energy has traditionally been supplied from a centralized grid, as has long been the case for natural gas, in recent years a number of pilot projects have got underway in which hydrogen is produced and used to generate power and heat through a decentralized model. One of the key motivating factors for these projects is an ambition to achieve a year-round autonomous energy supply from local renewable energy sources. The explosion in price for electricity, natural gas and heat which we are now experiencing means that the issue has added poignancy.
The aim of this article is therefore to provide an overview of example projects that have been completed so far and to shed light on the current supplier situation for self-sufficient building energy systems that are based on hydrogen. As these two areas are subject to dynamic changes, this summary does not claim to be exhaustive.
Definition: Energy self-sufficiency
The term “energy self-sufficiency” is understood to mean a total independence from external, often grid-based energy supply infrastructure, for example for power, gas and heating. All the energy required is produced, stored and consumed locally within a certain boundary, such as a building. Any excess power and heat can be fed into external supply infrastructure. If the system is “power self-sufficient,” that signifies that only electricity needs are met through local generation. In this case it’s possible to feed into the grid. “Partially self-sufficient” supply systems often achieve a high level of autonomy without being fully independent of external supply infrastructure.
Overview of projects
Table 1 shows a selection of German projects in which locally generated hydrogen is used for storing energy and supplying energy to buildings. As well as achieving different levels of self-sufficiency, the projects diverge in how they implement and integrate hydrogen technologies. In some instances the projects integrated turnkey system solutions that offer hydrogen production, storage and utilization within a standard product. These systems will be considered in greater depth later on (see table 3). Meanwhile other projects had individually tailored designs in which electrolyzers, fuel cells, storage systems and other components were sourced from various manufacturers and suppliers and then combined by a system integrator to create an overall solution. Another distinction was made in terms of the scope or the size of each project. This allowed the projects to be divided into residential buildings, commercial premises and neighborhoods.
From 2018 onward, over 100 hydrogen energy supply projects were completed within buildings using Picea systems, thus enabling the manufacturer Home Power Solutions, known as HPS, to become established in the German market. Because of the similarity between hydrogen houses that have a Picea system, table 1 only shows two such projects in single-family homes and one such project in a commercial property. The single-family home in Zusmarshausen deserves particular attention. As well as using the standard commercial HPS product, other components were added to the system which resulted in an entirely off-grid energy supply. In addition to the gel battery included in the Picea system, a further 25-kilowatt lithium-ion battery was installed as a backup and to give the option for bidirectional charging of a battery electric car. What’s more, a relatively large hydrogen tank was fitted in comparison with other projects involving single-family homes.
By contrast, the project in Lahn-Dill-Kreis is a typical example of a Picea house. Here, for instance, heat pumps were installed to support heat generation as well as a photovoltaic system. It is also possible for the Picea systems to supply a building with energy on a larger scale. In 2021, the company Josef Küpper Söhne installed a self-sufficient building energy supply for one of its commercial operations in the form of a multi-Picea system consisting of five units.
One project in Augsburg has a unique feature that is worthy of note. Whereas all the other projects store and use hydrogen, in this case the supplier Exytron created a partially self-sufficient multifamily home with a methanation plant that converts locally produced hydrogen directly into synthetic natural gas, i.e., SNG. The carbon dioxide that is needed for the conversion is obtained from the combustion of SNG in a combined heat and power unit and a condensing boiler, meaning that the process is carbon free overall. A fuel cell is not used.
Compared with the projects described thus far which have all concerned single buildings, the two neighborhoods in Bochum and Esslingen presented in table 1 incorporate custom designs. The Open District Hub achieved partial self-sufficiency for its 81 apartments through the use of electrolyzer equipment, a fuel cell, a PV system, a battery and a heat pump.
The eco-friendly neighborhood in Esslingen am Neckar (see H2-international, May 2021) is based on a combination of several energy conversion systems that provide electricity and heating to residential buildings, university buildings, offices and commercial spaces. A fuel cell, however, is not used. In order to heat the neighborhood, particular use is to be made of the waste heat from the electrolyzer. The resulting hydrogen is to be used in a multi-fuel CHP unit and also marketed externally, in other words sold outside the neighborhood through a supply arrangement with a hydrogen refueling station as well as fed into the natural gas grid.
Besides the above neighborhood schemes, a fully self-sufficient events center is also in operation in Ursprung in which energy is supplied by means of PV power, electrolysis, a fuel cell and a compost heater. Plus, there is a project planned for Gütersloh in which an entirely off-grid district will make and use its own hydrogen. The two projects are not listed in table 1 since it has not yet been possible to obtain precise information about the systems used or their size in either case.
Looking beyond the German projects outlined, the first hydrogen systems designed to supply energy to multifamily homes were completed in Sweden and Thailand as early as 2015. In these examples hydrogen was used for both energy provision and storage.
Microorganisms have many talents. Some of them produce hydrogen from sunlight or biomass, others produce electricity from hydrogen. With their help, metabolic processes from the earliest days of the planet could become an integral part of a modern energy economy.
Blue-green algae do not have a good reputation. When they emerge in lakes visited by bathers, their toxic metabolites can cause dizziness and breathing difficulty. But they are the basis for all life on earth. And these special microbes are not actually algae at all, but bluish bacteria – today, therefore, they are also known as cyanobacteria.
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Billions of years ago, they developed the ability to convert sunlight into energy and to store it. It is only thanks to this process, photosynthesis, that more complex forms of life have been able to develop.
Today, researchers are trying to use photosynthesis to produce hydrogen in an environmentally friendly way. For this, they are focusing on certain enzymes, specifically hydrogenases, that can originate from blue-green algae or “real” algae.
Hydrogen via photosynthesis
The process of photosynthesis occurs in several steps. In so-called photosystem I, sunlight sets energetic electrons free. Normally, the cell would use these to store energy in the form of sugars in further steps. The enzyme hydrogenase can capture these electrons and bind them to H+ ions instead, which are available everywhere in the cell. This is how hydrogen is biologically produced from sunlight.
This process is a relic from times when completely different conditions prevailed on earth. “We can encourage this metabolic pathway by putting the algae on a type of sulfur diet in an airtight container. After they have consumed the oxygen, they begin to produce hydrogen, which rises in small bubbles,” illustrates Christina Marx of the photobiotechnology working group at Ruhr-Universität Bochum (RUB).
The search for the perfect enzyme
Also Kirstin Gutekunst, professor in molecular plant physiology at Universität Kassel, emphasizes, “No organism has an interest in primarily producing hydrogen for humans.” To promote hydrogen production, they therefore have to artificially join the hydrogenase to photosystem I. A major challenge in this is that the hydrogenase is sensitive to and reacts with oxygen, which also evolves from the water splitting during photosynthesis.
Marx, Gutekunst and other researchers are therefore in the laboratory searching for microorganisms, enzymes and other biological components that produce as much hydrogen as possible yet at the same time are not destroyed by oxygen.
In 2020, Gutekunst had led the research group at the Christian-Albrechts-Universität zu Kiel (CAU) that succeeded in inducing the process in a living cyanobacterium for the first time. The advantage of this is that the bacterium can repair itself, so the process is more stable. Also the H2 yield ended up being significantly higher than in earlier projects. However, the cyanobacteria got the electrons not only from water splitting, but also from sugar. “Either the organism must produce the sugar itself beforehand or we must supply it externally. What we really want is to produce hydrogen exclusively with water and sunlight,” explains Gutekunst.
As part of her professorship in Kassel, she is continuing the research towards finding suitable hydrogenases. “Right now, we’re studying an enzyme from knallgas bacteria. It is fairly resistant to oxygen. Unfortunately, it takes up H2 rather than producing it,” says Gutekunst. That’s why her team is working in parallel with different mutations – always in search of the all-rounder.
The Arbeitsgruppe Photobiotechnologie team around Prof. Thomas Happe at the RUB, to which Marx belongs, is also looking for the perfect enzyme for hydrogen production. Together with the University of Osaka, the researchers at the RUB want to understand the structures and mechanisms even better, by looking at cryogenic enzyme samples and other biological building blocks under the electron microscope. Their goal is not only to make the enzymes more active and stable, but also to develop simpler structures, which are easier to use technically.
“We are working on so-called mini-enzymes. These have the function of a hydrogenase, but are smaller and simpler in structure. They contain practically only the active center and the necessary structure to be able to catalytically produce hydrogen as well as split hydrogen. This way, they will also be easier to commercially manufacture and use later on,” says Happe.
A challenge is still the sensitivity to oxygen. Some enzymes, like the CbA5H being studied at the RUB, can shield themselves against oxygen. “This is an important step, because then the active center stays intact,” says Marx. “But as soon as oxygen is present in the environment, it’s kind of like the pause button is pressed and the enzyme doesn’t produce more hydrogen, although like practically all other enzymes is not destroyed by oxygen. Our goal is to develop an enzyme that does not allow oxygen to penetrate into the active center and at the same time still produces hydrogen.”
In order for these enzymes to be used technically, they must be applied to surfaces, and in such a way that they stay a long time and can work as efficiently as possible. The RUB team intend to approach this task in further projects.
While most countries in Western Europe laid out their strategies for hydrogen extraction some time ago, this southeastern member of the European Union has yet to take this step. Indeed the Romanian government isn’t planning to announce its hydrogen strategy until 2023. Huge potential exists for Romania to excel in the production of carbon-free hydrogen, however, given the country’s impressive sustainable energy mix.
In 2021, over 30 percent of Romania’s electricity consumption was met by hydropower. Almost 20 percent of electricity generation is provided for by nuclear power plants. And wind power, at over 11 percent, accounts for a significant share which is also growing rapidly.
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Despite the lack of a national strategy, hydrogen development is well underway in Romania. The infrastructure side is being supported by the Three Seas Initiative or 3SI. This project has been actively involved in all EU states located between the Baltic, Adriatic and Black seas since 2016. It aims to promote cooperation on the implementation of major infrastructure schemes which will connect the region economically and drive it forward.
One of the ways in which 3SI has provided assistance is by helping grid operator Hidroelectrica Romania establish a joint venture for the construction of hydrogen pipelines. What’s more, Hidroelectrica has been taking part in the Green Hydrogen @ Blue Danube project alongside Austria (see fig. 1). Within the framework of the European Commission’s Important Projects of Common European Interest or IPCEIs, the states in the Danube region and in southeastern Europe are to be supplied with green hydrogen along the Danube and in southeastern Europe. Other participants include Austrian power company VERBUND as well as Hydrogenious LOHC Technologies in Germany.
A multitude of separate schemes
In 2009, Romania witnessed the founding of the National Research and Development Institute for Cryogenic and Isotopic Technologies ICSI and the National Center for Hydrogen and Fuel Cells CNHPC. Their remit is to encourage the introduction, development and spread of hydrogen-based energy technologies. However these initiatives have enjoyed only modest success. So far researchers from ICSI have developed two electric car prototypes that are powered by fuel cells and have a maximum range of around 200 miles (320 kilometers).
A pot of EUR 115 million is envisaged for the first 100 megawatts of green hydrogen production capacity. This funding is a key pillar in the country’s recovery program entitled Național de Redresare și Reziliență or PNNR for short. In Romania, industry giants Hidroelectrica, Romgaz (SNG), OMV Petrom (SNP), Liberty Galați as well as several wind power producers are all currently investigating options to produce green hydrogen.
Liberty Galați recently announced its intention to manufacture green steel and also to develop hydrogen-powered vehicles. Romgaz is planning use photovoltaic power plants to generate electricity which it will use to make hydrogen. The hydrogen will then fuel the company’s fleet of vehicles, 20 percent of which are to be converted to run on hydrogen. Also involved is Russian group Lukoil, which has a refinery in Ploiești. It too is expecting to take the first steps toward green hydrogen manufacturing. At the moment there are 13 industrial hydrogen producers in Romania and these principally use fossil fuels in their processes. Only Chimcomplex (CHOB) and Liberty Galați have projects to produce green hydrogen on their agenda.
Hence there is no shortage of initiatives from the hydrogen industry in Romania, but the lack of coordinated strategic planning has been viewed critically by local experts. Răzvan Nicolescu, Romania’s former energy minister, sees insufficient investment particularly when it comes to the integrated production chains needed by the hydrogen sector. “We talk a lot about hydrogen (…), but we haven’t yet actually asked ourselves how we can convince Cummins, one of the largest manufacturers of hydrogen plants, which is already based in Craiova, to produce electrolyzers in Romania,” explained Nicolescu with disappointment.
Infrastructure expansion
The operator of the national natural gas grid Transgaz (TGN) has been helped by the 3SI project in setting up a joint venture for the construction of hydrogen pipelines. Given the specifics of Romania’s energy requirement, the need to expand pipeline infrastructure is of primary importance. Romania anticipates that hydrogen will be chiefly deployed in industrial applications. The country experiences particularly high demand for energy from its domestic refineries, chemical works and steelmaking plants.
The focal point for the development of the Romanian hydrogen sector is the region to the southeast of the country. This is because the Black Sea coast is home to major branches of industry and is also the location for the planned expansion in offshore wind. The port of Constanta is often cited in this connection.
The Black Sea area offers Romania enormous potential in terms of wind energy generation – estimated at over 70,000 megawatts. “This energy is also due to be used for hydrogen production,” said former state secretary at the economy and energy ministry Niculae Havrilet.
The region that borders Ukraine in the north and Bulgaria in the south is known as Dobrogea. “Dobrogea ranks second after Scotland in terms of the size of potential for wind power generation in Europe. And this is where electrolyzer technology comes in, which allows the green energy generated by the wind turbines to be turned into green hydrogen,” explained Alexandru Bădescu from Cluster South East Europe at Linde Gaz Romania, speaking to the Romanian media.
In Dobrogea the wind conditions are well-nigh ideal for electricity generation. The area is inspiring lively interest from national and international wind farm developers. Leading the way in the use of wind power for hydrogen production in Dobrogea are companies Romgaz and OMV Petrom which are already working in partnership to unlock natural gas resources from the Black Sea.
The HyWays for Future project will boost efforts to ramp up renewable hydrogen production and use in northwestern Germany through a network of around 250 members. The aim of the initiative is to firmly embed sustainable hydrogen in the industry, energy supply and mobility sectors. Its initial focus will be on the deployment of hydrogen within transportation. As part of the project, investment will be channeled into various schemes, including the construction of hydrogen refueling stations, mobile storage, the procurement of hydrogen buses for local public transport, street sweepers and hydrogen-powered cars.
Hydrogen’s role as an energy carrier makes it a vital building block in the energy transition and northwestern Germany lends itself as a location for establishing a strong, sustainable hydrogen economy, in other words a veritable hydrogen hub. The focal point for this flagship hydrogen region is the Northwest Metropolitan Region which is home to the towns and cities of Cuxhaven, Wilhelmshaven, Bremerhaven, Oldenburg and Bremen.
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National hydrogen hub
The HyWays area is well placed to become a leading region for hydrogen in the transport sector. Thanks to the high number of wind plants, situated both onshore and offshore, the electricity consumed here is already nearly 100 percent renewable. What’s more, the region offers caverns that are suitable for hydrogen storage and there are a wide range of possible outlets here for hydrogen use. Consequently a hydrogen economy will have enormous potential to create new added value in the region. It’s this favorable location and potential for development which the project is hoping to exploit.
HyWays for Future is founded upon two pillars: the implementation project and the innovation cluster.
HyFri – hydrogen buses for the Friesland district
The German district of Friesland is deploying hydrogen buses to enable zero-emission public transportation in some parts of its local network. The project, which will initially see five vehicles enter service, is designed to kick-start the expansion of the local hydrogen economy. The title HyFri, a contraction of Hydrogen and Friesland, underlines the project’s local roots and the regional nature of the value chain. The hydrogen buses, operated by regional bus company Weser-Ems-Bus, will pioneer the use of green hydrogen in the area. This is because of the potential to save vast amounts of carbon dioxide within the transportation sector.
Bus refueling will take place at a new hydrogen filling station which is to be conveniently situated in the town of Schortens. Operation of the refueling station will fall under the remit of a new operating company founded by the partners Weser-Ems-Bus, EWE and the Gödens Group. HyFri will be funded by the German transportation ministry as part of the HyWays for Future scheme.
The implementation project
The clearly communicated aim of the HyWays for Future initiative is to not only produce clean hydrogen locally with sustainable energy but to use it locally too. To make this happen, the implementation project plans to develop electrolyzer capacities and hydrogen refueling stations as well as invest in hydrogen vehicles.
Hydrogen production: HyWays for Future will rely on a variety of models for the manufacture of green hydrogen depending on local circumstances. Options include decentralized on-site production at refueling stations using small electrolyzers and large-scale centralized production, for example at industrial parks from which the hydrogen will then be transported to the filling stations.
Hydrogen refueling stations: Filling stations are vital facilities that underpin the use of hydrogen within the transportation sector. Up to five such refueling stations could be created in the flagship region as part of HyWays for Future. These stations will then form a network that will ensure widespread availability of hydrogen for fuel cell vehicles.
Fuel cell vehicles: Finally there are the zero-emission vehicles powered by green energy that will consume the hydrogen. The project foresees the purchase of buses, municipal vehicles such as street sweepers, and cars.
HY.City.Bremerhaven builds local green hydrogen infrastructure
A scheme in Bremerhaven will create a regional green hydrogen ecosystem from the end of 2022. To enable this vision, the company HY.City.Bremerhaven will build and operate an electrolyzer plant with a 2-megawatt capacity and a hydrogen refueling station located immediately adjacent to the service yard of Bremerhaven Bus. HY.City.Bremerhaven was established especially for this project by Bremerhaven startup Green Fuels, Bremerhaven Bus, construction service provider Georg Grube and tank logistics company UTG together with energy transition experts GP Joule. The project will construct a 2-megawatt electrolyzer and a public hydrogen refueling station for buses, trucks and cars. Funding for HY.City.Bremerhaven will come from the German transportation ministry as part of the HyWays for Future scheme.
The Safe Light Regional Vehicle (SLRV) was developed by the German aerospace center (Deutsches Zentrum für Luft- und Raumfahrt, DLR) as part of the research project Next Generation Car (NGC). It addresses concerns about the safety of today’s lightweight microcars with the novel metal sandwich construction. This together with an innovative entry concept, highly efficient H2 fuel cell drive system and crash-optimized chassis were able to achieve the ambitious targets regarding weight (450 kg), safety, energy consumption and manufacturing cost.
The body of the two-seat SLRV is 3.8 meters long and low to the ground, for the lowest possible air resistance. The additionally low weight is crucial for low energy consumption. Even for electrified vehicles with recuperation, up to 93 percent of energy consumption, depending on which point in the drive cycle, is weight-dependent [FRI2010]. A low body mass also enables secondary mass reduction, so smaller and more cost-effective drive components, and its effects [ECK2011].
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According to initial simulation results, the SLRV is expected to consume only half as much hydrogen as a conventional fuel cell-powered passenger car.
Sandwich construction: light, low-cost, safe
To achieve the goal of a lightweight and safe construction that is nevertheless cost-effective, the so-called metal sandwich construction (metallische Sandwichbauweise) was developed (see Fig. 2). The materials are composed of metal cover layers and plastic foam as the core. The front and rear sections of the SLRV are composed of sandwich panels and serve as crumple zones [BRU2017]. A large part of the vehicle’s machinery is also housed there.
The passenger compartment consists of a floor tray braced by a ring structure. This absorbs the forces that act on the car while it’s driving and protects the occupants in the event of a crash. With the floor tray, assemblies that are individually found in the passenger compartment of a conventional car body, such as front wall, rear wall, rocker panels and floor, are combined into a single construction element, which significantly reduces the complexity as well as the number of joints.
Similar advantages are offered by the use of the upward-opening canopy in conjunction with a roll bar. With these, the doors, posts, A and C pillars, and roof have been replaced by a single piece. So far, structures made of sandwich materials have not yet been used in the series production of vehicles. The DLR has shown its potential and in the next step is working to optimize the relevant manufacturing technologies.
Crash behavior in the event of a frontal impact
The crash behavior of the SLRV body during a frontal impact was analyzed and documented in accordance with US NCAP guidelines. Such a crash corresponds to an impact of the vehicle against a rigid wall at 56 km per hour (35 mph). The crash box and front end of the SLRV are evenly deformed in the process and absorb the crash energy. The passenger compartment is not deformed, to not reduce the survival space for the occupants.
Important for the crash behavior is also the chassis design of the SLRV. The chassis is designed in such a way that the wheels detach in the event of a crash and are guided past the car body [KRI2019]. This way, the passenger compartment is not hit by the wheel and can be more simply designed.
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