Hydrogen System of Autonomous Power Supply of Low Power

Abstract

In the traditional centralized power supply systems, no alternative power source can be used if the main distribution network is damaged by a natural disaster, which makes traditional power systems fragile. In this article, an analysis of autonomous power supply systems has been carried out and an autonomous hybrid power supply installation based on a hydrogen power plant with a capacity of 5 kW has been developed.

1. Introduction

People spend most of their day in inside environments; therefore, those environments must be in good condition for these users. In 2019, the building sector accounted for 35% of the world’s energy consumption and 39% of gas emissions, the highest ever recorded [1].

With the increasing number of people living in cities, the demand for energy in homes is constantly increasing; thus, smart buildings were created to provide users with better comfort conditions.

In order to increase the efficiency of traditional sources of electricity, such as solar and wind power plants, as well as ensuring reliable power supply of the reserve for consumers, reducing the environmental burden on nature requires very effective means of energy storage and production.

“Increasing the capacity of systems from electrochemical batteries is associated with high costs, they become unreliable after prolonged operation, are sensitive to temperature and are hazardous to the environment during disposal.” Also, for a small power generation system, the overall characteristics of energy storage devices become critical. Metal hydride storage technology is a good alternative to other storage systems. “The energy reserve time when using metal hydride storage technology based on hydrogen fuel cells depends only on the amount of stored hydrogen.” The hydrogen system does not have a problem of recharging and self-discharge, which guarantees the stability of energy parameters and simplifies the operation [2].

The purpose of the dissertation is to analyze possible options for autonomous power supply systems. In the course of the study, the following tasks were performed:

• An analysis of autonomous power supply systems has been carried out.

• A power supply system for a remote settlement based on a hydrogen system has been developed. Object of research—power plants of backup power supply Subject of research—autonomous hybrid installation energy supply on the basis of a hydrogen power plant with a capacity of 5 kW.

Scientific novelty of the work:

• the required number of elements of the power system for sustainable and uninterrupted power supply to the consumer;

• it has been established that the developed autonomous power supply system based on a hydrogen system is economically feasible in the absence of the possibility of connecting to a centralized power supply system with a service life of more than 20years.

Practical significance of the work:

• the result of the work allows us to establish prospects for the development of the topic of the use of small-scale energy based on a hydrogen power supply system.

Approbation of the work:

The main provisions of the work were presented in the form of a report at student scientific and technical conferences.

Publications. Two printed works have been published on the topic of the dissertation.

Structure and scope of work. The dissertation consists of an introduction, three chapters, and conclusions. In the course of the study, a comparative analysis of classical power supply systems and a low-power hydrogen system up to 5 kW was carried out. A system based on an autonomous hydrogen power supply system was proposed.

Analytical review of information sources on the topic of the work “The current state of global energy, based mainly on traditional hydrocarbon sources of raw materials, is characterized even by optimistic estimates as precrisis.” And it is not only the obvious depletion of these resources, but also the increasing danger of global disasters due to environmental pollution. Of course, nuclear energy, taking into account the available uranium reserves in thorium, will play an increasingly important role in the global economy. It is assumed that in the distant future, thermonuclear energy will take a decisive place in large-scale energy. However, it is already clear that serious energy and environmental problems will overtake the world before the first thermonuclear power plant comes into operation. In addition, even if we assume that nuclear and thermonuclear energy will be able to produce the necessary amount of electricity, it remains unclear how the energy obtained can ensure, for example, the functioning of transport or the vital activity of remote areas [3].

Today, transport uses about half of the world’s the volume of consumption of petroleum products, and in the USA—up to 65%. At the same time, the exhaust of internal combustion engines contains about 45 toxic substances, including carcinogens. Therefore, the search for alternative renewable and environmentally friendly sources capable of providing humanity with energy for the next hundreds of years is one of the undoubted priorities of modern science. This search shows that one of the most likely substitutes for organic fuels of energy carriers for transport and energy in general is hydrogen. Hydrogen is suitable for all types of heat engines: reciprocating, turbine, piston-turbine, Stirling engines, etc. At the same time, hydrogen as a fuel has a high energy content per unit mass—120.7 MJ/kg, which is higher than that of any organic fuel.

“The use of hydrogen for energy production leads to a sharp decrease in environmental pollution.”

During the combustion of hydrogen in oxygen, toxic exhausts are completely absent, since the reaction product is water, and during combustion in air, pollution is much lower than when using gasoline. It is very important that hydrogen can be used for direct conversion of chemical energy into electrical energy. Such a transformation occurs in an electrochemical generator (fuel cell) when hydrogen is combined with oxygen on one of the electrodes, and harmful emissions are practically absent. “The efficiency of a fuel cell can reach very high values—from 40 to 70%, and it depends relatively little on the installed capacity and load,” (recall that the efficiency of thermal machines such as internal combustion engine, diesel, does not exceed 40%). It is the progress in the development of fuel cells (TE) with high efficiency that inspires confidence in the prospects of using hydrogen as a fuel when creating autonomous mobile and stationary energy sources. Such sources can be widely used in transport, including in cars with so-called “hybrid” engines [4] (a conventional engine plus an electric motor on a fuel cell).

“Cars with TE are especially promising for use in urban environments. Another booming TE market is associated with the need to increase the duration of continuous operation of small-sized electronic devices (cell phones, portable personal computers, etc.) and replace conventional batteries and accumulators in them with more energy-intensive power sources” [5]. The successes achieved in the development of fuel and energy sources, the rise in the value of traditional energy carriers (especially oil), political instability in oil-exporting countries, environmental problems—all this has led to an awareness at the government level of the need for accelerated development of research and technology in the field of hydrogen energy. In this regard, the decision of US President George W. Bush to include hydrogen energy among the national priorities is characteristic. The US Congress has decided on financing an amount of $ 1.3 billion. USA works on fuel cells for cars. Japan supports the development of technologies based on hydrogen and TE through a 28-year program (1993–2020) with a total budget of 2.4 billion euro. Financing of research on TE in Europe is approximately 1/3 of the financing in the USA and 1/4 of the financing in Japan. At the same time, in recent years, EU countries have been actively developing a strategy to consolidate the efforts of governments and large international companies in the development of hydrogen technologies and fuel cells. It should be noted that large nonstate companies, mainly automotive ones, also invest large funds in the development of hydrogen technologies.

2. Experimental study of hydrogen production using solar energy

Hydrogen is a sustainable fuel option and one of the possible solutions to environmental problems. In this study, hydrogen is obtained using a hydrogen generator with a proton-exchange membrane (POM) of an electrolyzer. A pilot study is being conducted at the Renewable Energy Development Center in Algeria.

The experimental device contains: a photovoltaic module, a POM electrolyzer, a gasometer, and devices for measuring the characteristic POM electrolyzer, as well as two pyranometers and a diffuser. This system allowed, on the one hand, to measure and analyze the characteristics of the POM electrolyzer at different pressures (Ratm and p = 3 bar), and on the other hand, allowed to study the volume of hydrogen in various sources of electricity (generator, photovoltaic module, and fluorescent lamp). The efficiency for each case was calculated and compared. This article presents the values of the change in the rate of hydrogen flow, depending on the time of day the experiment was conducted in which was in August during the daytime.

Hydrogen is considered as the energy carrier of the future. It can be obtained in various ways, including using solar energy, as well as using solar thermal energy.

Solar energy can be used in an electrolyzer to decompose distilled water into hydrogen and oxygen. Autonomous electrolyzer systems are used for the production of hydrogen fuel. This system consists of a photovoltaic module that supplies electricity through an electrolyzer system, as shown in the major projects in USA and FRG.

Water electrolysis is considered one of the key technologies for hydrogen production because it is compatible with existing and future power generation technologies and many renewable technologies (solar, biomass, hydro, wind, tidal, etc.). Most water electrolysis technologies currently available on the market use acidic or alkaline electrolyte systems for hydrogen production. Typical efficiencies are shown in the 55–74% range, with most commercial systems having efficiencies of less than 65%. Current densities are typically around [6] 0.3–0.4 A/cm, and there are technical difficulties in maintaining the electrolyte balance, as well as in maintaining hydrogen and oxygen. Currently, the technology of electrolysis of water based on a polymer electrolyte membrane is under development. The POM electrolysis system can quickly respond to changes in energy consumption and, therefore, can be easily integrated with renewable energy systems. The POM operates at relatively low temperatures, usually at 80°C or below, and usually consists of numerous cells stacked in series. Guillaume Doucet and others studied the general characteristics of the integrated and automated hydrogen power plant (APU).

The system consists of a 0.46 W photovoltaic module (RV), and the 0.64 W electrolyzer that includes a proton exchange membrane, an alternating voltage generator, a 1000 W fluorescent lamp, two vessels with a capacity of 250 ml, and a device that removes the characteristics of the POM electrolyzer, as well as two pyranometers [7].

The main part of the POM block is a membrane electrode block. A layer of catalyst material was applied to both sides of a thin proton-conducting membrane (POM = proton exchange membrane). These two layers form the anode and cathode of the electrochemical cell. As we see in Figure 1, oxygen gas, electrons, and H+ ions are formed on the anode side. H+ ions pass through the membrane to the cathode and form hydrogen gas with electrons flowing through an external conductive circuit. Thus, electrical energy is converted into chemical energy, and stored in the form of hydrogen and oxygen.

Figure 1.

Functional principle of the POM electrolyzer.

The electrolyzer produces hydrogen and oxygen in a ratio of 2:1 (Figure 1), the volume of hydrogen released is measured as a function of time, that is, the start of the countdown occurs when the water in the gasometer (H2) passes the lower sign. Next, the voltage and current I are measured during electrolysis [6].

The experience done should first of all show how the characteristics of the POM electrolyzer change at different pressures.

At the experimental facility, we determine the volume of hydrogen produced at different energy sources. The first way is solar energy. The second method consists of simulating solar energy using a lamp. The third method is an electrolyzer POM voltage generator.

The results are presented in the following paragraphs. First, the POM electrolyzer is operated at two different pressures (Patm and P = 3 bar). Then the volume of hydrogen was produced with various sources of electricity (generator, photovoltaic module, and daylight lamp). Finally, we calculated the efficiency for each case.

The performance of the POM electrolyzer for two different pressures is shown in Figure 2.

Figure 2.

Graph shows that the pressure has a significant impact on the performance.

The graph shows that the pressure has a significant impact on the performance of the electrolyzer POM. The effect of increasing oxygen pressure from three bars leads to an increase in voltage of 0.06 V and current. These results show that an increase in oxygen pressure leads to a significant improvement in polarization at the cathode.

The conclusions obtained:

• Hydrogen is a clean source of energy. In addition, the energy required to create hydrogen requires less than that can be derived from it.

• Reducing dependence on fossil and nuclear energy would free the country from costly foreign involvement and improve the health and welfare of its citizens. This would be accomplished by significantly reducing greenhouse gas emissions and other toxins associated with fossil and nuclear energy sources in the air, land, and water [6].

• Solar energy can serve as a power source for the electrolyzer to produce hydrogen. Hydrogen will be stored in storage devices to start the thermal power plant when solar energy is not enough to provide electricity to the consumer.

3. Development of hydrogen storage systems based on complex metal hydrides

This review describes the latest research in the development of a tank based on complex metal hydrides for thermolysis and hydrolysis. Commercial applications using complex metal hydrides are limited, especially for thermolysis-based systems, where only demonstration projects have been carried out so far. Hydrolysis-based systems find their application in the space and military industries due to their compatibility with proton membrane fuel cells.

Tanks containing mainly sodium aluminohydride and several examples with nitrides have been developed for thermolysis.

For hydrolysis, sodium borohydride is the preferred material, while ammonia has proven to be less effective. The disposal of spent sodium borohydride fuel remains an important part of their commercial viability.

Over the past 15 years, complex aluminum and boron hydrides have been investigated as possible materials for hydrogen storage. Although the composition of these materials is similar, the chemical behavior is completely different. An example of some complex aluminum hydrides are NaAlH4, CAlH4, NA1H6, etc. These hydrides can be decomposed at elevated temperatures and under technically significant conditions using catalysts, and repeated dehydrogenation can also be carried out. However, the decomposition temperature of complex boron hydrides (LIH4, NVH4) is often much higher, and reversibility cannot be observed under the conditions used for complex aluminum hydrides. Consequently, complex aluminum hydrides can be used for technical applications where repeated dehydrogenation of the material for hydrogen storage is an important condition [8]. And complex boron hydrides are preferred for cartridge systems that release hydrogen in a hydrolysis reaction at ambient temperature. These different properties lead to completely different technical requirements. This makes the development of storage systems based on aluminum or borohydride compounds a difficult task.

Thermolysis requires heat input and care must be taken when designing a storage tank to distribute heat efficiently. Hydrolysis, on the other hand, requires not only the efficient mixing of complex hydrides and water but also the separation of the resulting hydrogen gas from a suspension composed of decomposition products and water. While pyrolysis tank systems are being developed in demonstration projects, hydrolysis storage systems are already being applied in real-world settings [8].

3.1 Autonomous hybrid power supply unit based on a hydrogen power plant

The structure of the system under consideration includes

• hydrogen generator;

• fuel cell module;

• inverter (voltage converter to ~220 volts);

• metal hydride storage.

1-external source; 2- voltage stabilizer; 3-hydrogen generator; 3- desiccant; 5-compressor; 6- check valve; 7- metal hydride storage; 8-reducer; 9-fuel cell; 10-ECU; 11-supply valve distilled water; 12- H20; 13- consumer; 14- A-ammeter; 15 -DH1- voltage sensor; 16- K1, K2- circuit key; 17 DU- level sensor; 18 UPD- hydrogen supply control; 19 DD- pressure sensor (Figure 3).

Figure 3.

Diagram of an autonomous hybrid power supply unit based on a hydrogen power plant.

The installation works as follows: the first circuit of the circuit is an external source, which is a power line. Its work consists in the energy supply of the consumer. The second circuit of the scheme is a hydrogen power plant with a nominal capacity of 5 kWh, which provides the consumer with electricity in the absence of electricity from an external source.

The Dantherm Power DBX5000 fuel cell module is shown in Figure 4—with a power of 5 kW. The average price of a fuel cell will be 550 € (Figure 5).

Figure 4.

Dantherm power DBX5000.

Figure 5.

Hydrogen generator.

The technical characteristics of the generator are given in Table 1.

Purity of hydrogen in terms of dry gas %	99,995
Concentration of water vapor at 2OC and 1 atm, no more, rrsh	5
Total hydrogen capacity reduced to normal conditions, l/h	16
The range of the specified output pressure of hydrogen, atm	1.5-6.5
Stability of hydrogen output pressure, atm	± 0.02
Operating mode setting time, no more than, min	30
Volume of distilled water to be poured, liters	1.0

Table 1.

The technical characteristics of the generator.

The operation of the hydrogen generator involves water costs, so we will give the cost calculations that are given in Table 2.

	Working/Hours	Water/Liters	Price/EUR
Day	10	0.1	0.01
Month	2100	21	2.1
Year	25,200	252	25.2

Table 2.

Calculation of water costs for the year of operation.

Metal hydride storage of hydrogenBL-3 (Figure 6). The average price is 500 EUR. We need two drives. Therefore, the price will be 1000 EUR (Table 3).

Figure 6.

Metal hydride storage of hydrogen BL-3.

Volume, liters	25
Pressure, atm	5
Length, millimeters	147
Weight, grams	307

Table 3.

Technical characteristics of a metal hydride storage device.

The price of owning the installation for 10 years will be 8125 EUR.

• Hydrogen is a clean source of energy. In addition, the energy required to create hydrogen requires less than can be derived from it.

• Reducing dependence on fossil and nuclear energy will free the country from costly foreign involvement and improve the health and well-being of its citizens. This would be accomplished by significantly reducing greenhouse gas emissions and other toxins associated with fossil energy sources in the air, land, and water [6].

• Solar energy can serve as a power source for the electrolyzer to produce hydrogen. Hydrogen will be stored in storage devices to start the fuel cell when solar energy is not enough to provide electricity to the consumer.

4. Conclusions

A diversity of research on strategies to promote thermal comfort and energy efficiency in buildings for sustainability was examined in addition to the main challenges and barriers encountered. Key aspects of thermal conditions that affect energy efficiency were identified in addition to building types and climates, new technologies, and discoveries to provide thermal comfort and reduce energy consumption.

• An autonomous energy supply system based on a hydrogen system can be considered under modern solutions, since it corresponds to current global trends in the field of power supply systems.

• The introduction of a hydrogen fuel cell system will implement environmentally friendly solutions for backup power supply systems.

• In terms of functional characteristics, fuel cell-based SRES are significantly superior to existing systems, which are confirmed in implemented projects all over the world.

• By cost indicators for averaged (typical) source, data backup power systems for fuel and energy sources and the initial cost is slightly higher in terms of cost of ownership by 10–30% as compared to the existing ones.