Thermal management of hydrogen refuelling station housing on an annual level

Highlights

• An optimal thermal management strategy of HRS was proposed.

• A detailed analysis of the system component's thermodynamic parameters was performed.

• The given procedure can be used as a sort of manual for thermal management of any HRS.

Abstract

A housing insulation of hydrogen refuelling station is vital from the aspect of safe operation of equipment in an environment that is installed. To secure hydrogen supply during the whole year, this work brings the solution for both cooling and heating insulation equipment inside of hydrogen refuelling station installed in Croatia, Europe. This hydrogen refuelling station was designed as an autonomous photovoltaic-hydrogen system. In the interest of improving its energy efficiency, an optimal thermal management strategy was proposed. To select the best technological solution for thermal management design which will maintain optimal temperature range inside the housing in cold and warm months, a detailed analysis of the system components thermodynamic parameters was performed. Optimal operating temperatures were established to be 25 °C in summer and 16 °C in winter, considering components working specifications. Insulation, type of cooling units, and heaters have been selected according to the HRN EN 12831 and VDI 2078 standards, while the regime of the heating and cooling system has been selected based on the station's indoor air temperature. The annual required heating and cooling energy were calculated according to HRN EN ISO 13790 standard, amounting to 1135.55 kW h and 1219.55 kW h, respectively. Annual energy share obtained from solar power plant used for the heating and cooling system resulted in 5%. The calculated thermal management system load turned out to be 1.437 kW.

Introduction

Solar energy and other forms of renewable energy sources (RES) in conjunction with hydrogen are perspective directions for energy transition [[1], [2], [3]]. Recognizing the potential of RES/hydrogen integrated technology, a growing number of studies and activities were made in the last decade regarding its applications [[4], [5], [6]]. The prominent use of hydrogen is in transportation [[7], [8], [9]], which is one of the largest sources of carbon emissions and therefore represents a great potential for its decarbonization, especially if it is produced via electrolysis using solar energy (PV–H2 systems) [[10], [11], [12]]. Compared to today's conventional internal combustion vehicles, in terms of their performances, the autonomy provided, and refuelling time required, hydrogen is the best solution to replace hydrocarbons as fuel [[13], [14], [15]]. However, hydrogen infrastructure, i.e. hydrogen refuelling stations (HRS), is not widely developed in comparison with other alternative forms of fuel. Hence, the prerequisite for further development is the reduced cost and improvement of technology for hydrogen production, storage, and distribution [[16], [17], [18]]. According to Ludwig-Bölkow-Systemtechnik, by the end of 2019, there are currently a total of 177 HRS in Europe, 178 in Asia, and 74 in North America, and a few in the rest of the world. Overall, there are 432 installed HRS, and out of them, 330 are public, while the remaining sites are reserved for closed user groups. In the past five years, the number of public HRSs has grown more than 4 times, with additional 226 HRS in the planning stage [19]. When considering hydrogen development in Europe, it is mainly focused on the European Union (EU), which invests in numerous projects of hydrogen technologies development of all regions [20]. By the beginning of 2020, hydrogen fuel cell electric vehicles (FCEVs) can be refuelled at 87 locations throughout Germany. By the end of the year, Germany is planning to reach the number of 100 HRS, according to its development plan [21]. Germany's development of HRS infrastructure is a result of constant investment in all aspects of hydrogen technologies with a great focus on research and development [22]. In Europe, France and Netherland are a significantly increasing the number of planned HRS. While France is focused on the development of fuel cell busses [23,24], Netherland is trying to utilize its great wind energy potential for hydrogen production [25]. The development of hydrogen technology in EU is not reserved only for its exclusive members. Due to well thought out and implemented policy [26], it is proficiently decentralized, with lots of countries successfully implementing hydrogen [27]. The Czech Republic is an excellent example of how the smaller country can develop hydrogen technology to the enviable level [28,29]. Asia, with its long history of hydrogen development, implemented a strong policy towards green environmentally friendly technologies, which is one of the world's first detailed national hydrogen strategies [30]. Japan with 114 HRS is the top country in the world, with Korea and China behind, with 33 and 27 stations respectfully. Korea is currently in process of building 40 HRS for buses and public use, which is the first step in their ambitus development plan, for 2030 and 2040, where they expect a significant exponential increase of hydrogen FCVs [31,32]. Environmental pollution is maybe best illustrated in China, which is why they are taking a strong turn towards green renewable energy [33]. One of the main fields is the transport sector, where hydrogen roads are being designed [34]. Therefore, China is adjusting its infrastructure, and by the year 2030, around 3.000 HRS should be installed [35]. Major hydrogen infrastructures exist in United States of America (USA - specifically California) and Australia, while development in Africa and South America [36] is not yet widespread.

The first Croatian HRS is designed as an autonomous photovoltaic-hydrogen (PVH2) system. It has multiple purposes. Primarily, it serves for refuelling hydrogen-powered bicycles up to 30 bar. Its secondary use is for the educational purpose of mechanical engineering students who have a chance to work with cutting-edge new technologies in the field of renewable energy. Station itself is designed for future upgrades so that the capacity of hydrogen flow and overall pressure can be increased with time and new innovative solutions can be implemented [37]. Another station purpose is research conduction for the development of the final product. To further clarify it, the shape of the housing resembling the letter H and number 2 is designed larger than current needs demand, enabling the installation of new devices in the system without changes in the structure. Furthermore, the installed power of photovoltaic modules provides more than double the amount of energy needed for the station's operational work and available area for an installment of additional PV modules if further development demands it is secured. These oversizing features were intentionally made as a cost-saving method, making further research more affordable. The station's design was protected as intellectual property which enables the design of HRS with bigger capacities as a final product. The current station serves as a model for testing upcoming systems and development research, such as the one in this paper. Since intermittency RES and energy demand significantly depend on the location of the system, i.e. climate conditions [38], a challenge was set out to optimize the energy management of the HRS and to dimension its components to achieve high energy efficiency and rational costs [39]. One of the most important parameters for the smooth operation of thermodynamically sensitive devices inside the HRS (Proton Exchange Membrane - PEM electrolyzer, batteries, regulator, charger, hydrogen storage tank) is the air temperature inside the housing itself. A heat management system is required to maintain an optimal temperature distribution throughout the year. The term Thermal Management describes all possible ways and processes such as heat transfer, conduction, convection, condensation, and radiation, with the aim to increase or decrease the temperature, or affecting the temperature distribution of the particular system [40]. Within thermal management analysis carried out on the HRS for hydrogen bicycles, the achieved results lead to the conclusion that one of the most important thermodynamic parameters for optimal operation of the sensitive equipment is the temperature of the air inside the housing itself. Analyzing the technical characteristics of the PEM electrolyzer, batteries, regulator, charger, and hydrogen storage tank, it was concluded that the required heat-controlled system will maintain an optimal temperature distribution between 16 °C and 25 °C throughout the year, with different operating modes depending on the measured internal temperature.