Outline Of The Study Objects

A key of precondition for the realisation of a hydrogen economy is the development of a hydrogen infrastructure which, by definition, includes the systems needed to produce hydrogen, to store it, and to deliver it to users. As discussed in Section 2.3, in order to realize the hydrogen energy economy in Germany, the required "clean" hydrogen may be imported from other countries [200, 201,168]. For example, the Euro-Quebec Hydro-Hydrogen Pilot Project, 1989-2001 (EQHHPP) considered to import hydrogen from Canada, where the cheapest electricity is available. The hydrogen is produced from water in large-scale water electrolysis plants powered by renewable energies (e.g. hydro, wind, solar, etc). It is imported to Germany using a large LH2 tanker ship, and/ or using a long distance GH2 pipeline. The imported hydrogen is then stored in mass storage plants located near a harbour (called "terminals"). Furthermore, the hydrogen is then transported or distributed to the regional storages or to user centres via regional transport by road, rail, river, and pipeline [ 208].

Fig. 3.1 shows the simplified scheme of the hydrogen energy economy considered in the study. Similar to other energy carriers (such as LPG) the hydrogen economy may be represented by hydrogen storage and transport. Storage at terminal is mainly used to store a large bulk quantity of hydrogen arriving from abroad, where the hydrogen can be stored in the form of liquid hydrogen (LH2) and compressed gaseous hydrogen (GH2). In case of transhipment, the LH2 storage is filled from an LH2 tanker, while GH2 storage from a longdistance pipeline. The hydrogen is distributed the regional distributors (e.g. depot) through regional transport, such as tanker truck, inland waterway, rail cars, or regional pipeline. To facilitate a regional distribution various hydrogen companies and traders should install depots for the intermediate storage of hydrogen. The hydrogen stored at depots is mainly used for the distribution in smaller tank trucks, for delivery by third parties, as buffer stocks, for reasons of economy (the storage of lots bought at low prices), and for operational reasons (the emptying, cleaning, and putting into operation of tank truck). Finally, the hydrogen can be distributed to hydrogen filling stations or directly to end-users through tanker truck or pipeline.

Figure 3.1 Hydrogen production, transport, storage and end-use pathways [ 187]

Small amounts of hydrogen may be produced domestically from reforming of hydrocarbons, refinery byproducts, and chemical by products as in the present production, or water electrolysis using electricity during peak power production or using renewable energies [168, 72, 197, 201].

Although some experts predicted that the hydrogen economy might be realized in the next 30-50 years (2030-2050) [30, 201], some of the infrastructures (such as hydrogen filling station) have been built worldwide. Besides, several industrial-scale hydrogen production plants (e.g. water electrolysis) as well as the end-use technologies (such as fuel cells) have also been successfully demonstrated. For example, a solar hydrogen plant has been successfully demonstrated in Germany for 13 years (1986-1999) [181, 182]. The study is focused on the following existing hydrogen plants information obtained through study visits, open literature, and contact or discussion with some German experts:

(1). Hydrogen production

The study considers a solar hydrogen plant (Solar-wasserstoff-Bayern, SWB) that was an industrial scale demonstration project (1986-1999) situated in Neunburg vom Wald, Germany. The system mainly consists of electricity generation, electrolyser, compressor, hydrogen storage, and so on. The hydrogen is produced from water through water electrolysis by using electricity generated from solar energy.

(2). Hydrogen storage

Since the large-scale hydrogen storages at terminals or depots as shown in Fig. 3.1 are not yet available the study considers the large-scale hydrogen storage situated in Ingolstadt, Germany. It stores a large amount of hydrogen in liquid phase (LH2) currently used for the regional distribution. Therefore, it may be considered as storage depot. The tank is filled (loading) directly from a liquefaction plant at the flow rate of 180 kg/h. The LH2 is distributed to costumers (e.g. hydrogen filling station) by a LH2 tanker truck.

(3). Hydrogen filling station

Hydrogen filling stations are a key of the hydrogen economy. Currently the numbers increase dramatically. The study considers the first public filling station owned by BVG, Berlin. The station stores hydrogen in liquid form, and delivers it to public hydrogen vehicles both in liquid and gaseous form. The tank is filled from the nearest hydrogen depot through an LH2 tanker truck.

(4). Hydrogen energetic applications

The study considers a hydrogen vehicle and a fuel cell - combined heat and power (FC-CHP) for household applications. The hydrogen private car (e.g. BMW 735i) stores hydrogen in liquid form, and delivers it to the internal combustion engine (ICE). For household application, the FC-CHP is regarded to provide electricity and heat for residential buildings situated in Hamburg.

(5). Hydrogen transportation

The study considers two types of hydrogen transport, i.e. a LH2 tanker truck and GH2 pipeline operated in Germany. The LH2 truck (e.g. Linde) with a capacity of 53 m3 is regularly used to deliver LH2 from a storage depot to end-uses technology (e.g. hydrogen filling stations). The transport routes, numbers of filling station and the truck delivery times were modelled in the study. The considered GH2 pipeline proposed to transport hydrogen from a hydrogen plant to user storage with the distance of about 53 km.

3.3 HYDROGEN PRODUCTION

The study considers a solar hydrogen plant situated at Neunburg vorm Wald, Germany. The plant was built by the Solar-Wassertoff-Bayern GmbH (SWB) founded in 1986, as a joint venture with 70% of the shares held by Bayernwerk AG and 10% each by BMW AG, Linde AG (both through wholly owned subsidiaries) and Siemens AG [181, 182]. Objective of the project was to improve the system components, test them in interaction with another and among other things reduce conversion losses, advance their suitability for practical implementation, and develop optimised overall concepts

Fig. 3.2 shows a layout of the overall facility from the aerial photograph which shows the operating and multi-purpose building (information center) and the plant subsystems installed outdoors. Prominent features are the South-oriented photovoltaic solar fields, the storage vessels for hydrogen and oxygen gas, liquid and gaseous nitrogen, and the liquid hydrogen filling station.

3.3.1 System Description

A solar hydrogen plant is a hydrogen production plant using solar energy to electrochemically decompose water in an electrolyser to obtain hydrogen and oxygen. In the electrolysis of water the electric current is passed through an electrolyte solution of water and potassium hydroxide or alkali, decomposing the water into its constituent elements hydrogen and oxygen. Hydrogen is formed in the cathode and oxygen in the anode. A diaphragm separates the two cells to keep the two gases from recombining into water. The produced hydrogen is then stored in a pressurized vessel. Energy input required to produce one cubic meter of hydrogen is about 5 KWh [181, 182].

The plant is an industrial-scale demonstration facility. It comprises major system components of a possible future energy supply based on (solar) hydrogen, such as photovoltaic solar generators, water electrolyzers, hydrogen and oxygen storage facilities, catalytic and advanced conventional heaters, a catalytically heated absorption refrigeration unit, fuel cells for stationary and mobile application, and a gaseous hydrogen filling station as shown in Fig. 3.3.

The larger solar generators (about 360 KW photovoltaics modules) convert the sunlight into direct current (DC) electricity, which is mainly used to power electrolysers. The feed power through maximum power point (MPP) -controlled DC/DC converters is connected to a common DC busbar interconnecting the solar generators, water electrolyzers and AC power grid. Two types of electrolyzers were installed to produce hydrogen (and oxygen) classified as low-pressure and high-pressure electrolyzers. Two advanced low-pressure water electrolyzers employing different technologies, rated at 111 KWe and 100 KWe capacity, total maximum hydrogen output 47 m /h. Addtionally, an advanced pressure-type electrolyzer of 100 KWe is characterized by operation at 32 bar pressure, provision for intermittent working mode and fast control response. No subsequent compression of the product gases to the SWB system pressure of approximately 3 MPa is necessary.

Figure 3.2 The solar-hydrogen plant in Neunburg vorm Wald [182].
Study Fermentation
Figure 3.3 Diagram of the solar-hydrogen plant [181].
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