An Economic Case Study of Hydrogen Energy Storage

Research Article

Austin Environ Sci. 2021; 6(3): 1064.

# An Economic Case Study of Hydrogen Energy Storage

Brito PSD* and Monteiro E

VALORIZA Research Centre, Polythecnic of Portalegre Campus Politécnico, Portalegre, Portugal

*Corresponding author: Paulo SD Brito, VALORIZA Research Centre, Polythecnic of Portalegre Campus Politécnico, Portalegre, 7300-555, Portugal

Received: September 01, 2021; Accepted: October 06, 2021; Published: October 13, 2021

## Abstract

The use of hydrogen as an energy vector has been considered as one promising way to attend society decarbonization. Hydrogen can be used as a chemical to store electricity and as a fuel to electric fuel cell mobility. This work makes hydrogen production potential economical evaluation of 5 real solar photovoltaic installations intended primarily for self-consumption. The surplus electrical energy can be used to produce hydrogen, which will be used later as a form of energy, potentially in an application. That provides greater economic value. Hydrogen serves as an important career to the storage of energy and can be more interesting and competitive than a battery-based solution. The results show that the use of hydrogen is only economically viable for mediumsized installations, greater than 300MW and for the production of hydrogen for mobility.

Keywords: Hydrogen vector; Energy economic analysis

## Introduction

Currently, humanity is confronting a major environmental problem that demands scientific and innovative solutions: the rise in the average temperature of the planet. This problem has resulted due to the rise of carbon dioxide emissions in the last 200 years due to the massive use of fossil fuels, and therefore it is imperative to develop new sources and ways for energy and fuel production that can be sustainable and simultaneously with neutral emissions of carbon dioxide. The previous problem requires persistent work in scientific research focused on the implementation of innovative solutions that can be sustainable for the environment, economy, and society. Nowadays, hydrogen is an important intermediate in the chemical industry and refineries. Renewable hydrogen is seen as an important secondary energy carrier of the future and could be used directly as fuel and feedstock for further syntheses as well as for the generation and storage of electricity. Generally, hydrogen production processes can be classified into three categories: electrochemical, biological, and thermochemical methods [1]. All of these methods can be realized on a renewable base. In the case of electrochemical methods, electricity must be generated by sustainable energy sources. Biological processes are a promising alternative approach for production of hydrogen from low cost, renewable, and environment-friendly resources [2]. In this process microorganisms convert organic substrates and water molecules into hydrogen by catalytic activity of two main enzymes as hydrogenase and nitrogenase [3]. Bio-hydrogen can be produced through different processes including photo-fermentation, darkfermentation, CO gas-fermentation, and photolysis. Among these processes, dark fermentation and photo-fermentation are considered as the most promising processes [4]. Dinesh et al. [5] performed an economic analysis of bio hydrogen production from food waste using dark fermentation method and reach a low hydrogen production cost of 3.20$/kg. However, as production rate of the fermentation processes is very low, required size of reactor would be high and hence installation cost is high. This is the key challenge of fermentation processes is the low production capacity per unit of capital investment [6]. Thermochemical hydrogen production process produces hydrogen from synthesis gas which is obtained from different processes. This technology mainly constitutes pyrolysis and gasification of biomass processes where a gas mixture mainly comprising hydrogen, carbon monoxide, methane, and carbon dioxide is obtained [7]. This gas mixture needs to be further processed to hydrogen gas by steam reactions and water gas shift reaction [8]. However, the use of thermochemical methods for hydrogen production is very expensive. Gholkar et al. [9] performed a technoeconomic assessment of hydrogen and methane production from thermochemical conversion of microalgae and conclude that the process is only viable if the market price of hydrogen is as high as$10/ kg. Sara et al. [10] performed a techno-economic analysis of hydrogen production from fluidized bed gasification of lignocellulosic biomass on a small-scale system and found out even a greater hydrogen production cost of 12.75€/kg. In terms of electrochemical hydrogen production processes, electrolysis processes are those with the highest degree of maturity and highest yields [8]. The electrolysis of water consists of the decomposition of water into oxygen and hydrogen by the effect of the passage of a continuous electric current through the water in a device called an electrolyzer. Hydrogen and oxygen are produced from water through redox reactions. The electrolyzer is a device that combines oxidation and reduction reactions to produce hydrogen and oxygen from water. A typical electrolysis process can use three different types of electrolytes: liquid electrolyte, solid polymeric electrolyte in the form of a Proton-Conducting Membrane (PEM), or oxygen ion-conducting membrane [1]. Grimm et al. [11] performed a techno-economic analysis of two solar assisted hydrogen production technologies: A photoelectrochemical system and its major competitor, a photovoltaic system connected to a conventional water electrolyzer. The production cost of hydrogen resulted in 6.22$/kg for the photovoltaic-electrolyzer system and in 8.43$/kg for the photoelectrochemical system. Pinaud et al. [12] found a production cost of hydrogen even it higher in 10.40\$/kg for the photoelectrochemical system. Since alkaline electrolysis is the most mature electrolysis technology and also most widely used [13]. An alkaline solution, which normally consists of 20-40% Potassium Hydroxide (KOH), is used as an electrolyte to increase the ionic conductivity of cells [14]. The main disadvantage of alkaline electrolysis is that the liquid alkaline solutions used are corrosive. In recent years, major developments have focused on reducing operating costs associated with electricity consumption, thereby improving efficiency. However, the current density has been increased, thereby reducing investment costs [15]. New materials are also being tested to replace the asbestos used in the diaphragm. These include membranes based on polymers of antimony impregnated with polymers, porous composites consisting of a matrix of polysulfone and ZrO2, known as Zirfon, and separators based on polyphenol sulfide. With regard to PEM electrolyzers, the main difference compared to alkaline electrolyzers is the use of electrolytes. PEM electrolysis employs a solid polymeric membrane as an electrolyte instead of the corrosive liquid electrolyte used in the alkaline electrolysis process. However, high-purity deionized water is required for this electrolysis process [16]. At the anode, water is oxidized to produce oxygen, electrons, and protons. Protons pass through the membrane to the cathode side while the electrons pass to the cathode side through an external circuit. At the cathode, protons are reduced to generate hydrogen. The PEM electrolyzer is more suitable for working with variable energy sources such as renewable energies. This is due to the transport of protons across the membrane which is facilitated by floating energy sources. Currently, the main drawback of PEM electrolyzers is the high cost of production, so the development of these types of demonstration projects on a pilot-scale contributes positively to the growth of these technologies that allow the energy storage and the production of fuels and raw materials with practically environmental null impact. The aim of this work is to evaluate the potential for hydrogen production in 5 real solar photovoltaic installations intended primarily for selfconsumption. Currently, all energy that exceeds the facility’s own consumption is either injected into the public utility grid, with a very low economic value or is simply wasted. The alternative that this study proposes is that this surplus electrical energy can be used to produce hydrogen, which will be used later as a form of energy, potentially in an application that provides greater economic value. Hydrogen thus serves an important function of storing electrical energy and can be more interesting and competitive than a battery-based solution. Its later use will be made essentially as thermal fuel, but it can also be used to produce electricity again through fuel cells either to produce electrical energy to inject into the grid or in hydrogenelectric mobility. This function is sometimes described as an energy vector, since it is not a primary source of energy, but it allows the transformation to other forms of energy in other applications.

## Methodology

Five practical cases of units in Portugal that have renewable production systems for photovoltaic electricity were studied, namely.

Case A: Services Operational Center Facilities in évora.

Case B: Pharmaceutics facilities in Lumiar/Lisbon.

Case C: Services Operational Center Facilities in Porto Salvo/Oeiras.

Case D: Services Operational Center Facilities in Queluz/Sintra

Case E: Car Stand Facilities in Abrunheira/Sintra.

The choice of locations for the case studies fell on the technical conditions in terms of electricity consumption, power level, and consumption profiles, as well as the characteristics of the location and the available area of exposure to solar radiation. In addition to the technical framework, the choice of locations was linked to the existing hydrogen consumption potential, in order to be used as an energy vector, as well as its location within or close to industrial parks. In all cases, the Energy Audit carried out proposed and designed photovoltaic installations for Self-consumption. In some cases, it was necessary to resize the photovoltaic solar installation in order to guarantee a surplus of energy necessary for the production of hydrogen. Table 1 shows the global values obtained during 2017 and Figure 1 shows the curves of energy consumption, electricity produced by the photovoltaic system and hydrogen production in a typical summer week. Most of the installations presents most of its electricity consumption at night, so during the day the production of electrical energy by means of photovoltaics ends up generating excess electrical energy that can be stored. Case A is an operational center of a large company, located in évora. Since this type is a typical industrial park facility, we chose to include it in this study. The installation presents most of its electricity consumption at night, so during the day, the production of electrical energy by means of photovoltaics ends up generating surplus electrical energy that can be stored. Case B is an installation corresponds to an office building of an industrial company and is located in a technological park in Lisbon. The company’s laboratories are located in the contiguous building. Thus, it appears interesting to include the analysis of this installation in the present study. As it is an office, most of its electricity consumption occurs during the day, so that during the day, the production of electric energy by means of photovoltaics does not generate a significant surplus of electricity unless the production installation is slightly over-sized. This surplus of electrical energy is used to produce electrolytic hydrogen in the sense that it can be stored. In relation do Case C, the facility corresponds to a logistics center (offices, warehouses and workshops) of a large company and is located on a campus in Porto Salvo, municipality of Oeiras. Most of its electricity consumption occurs at night, so during the day, the production of electric energy through photovoltaics ends up generating surpluses. Case D is an operational center of a service company, which is located in Queluz, in the municipality of Sintra. This type of facility is typical of industrial parks, so it is also included in this study. This installation presents most of its electricity consumption at night, so during the day, the production of electrical energy by means of photovoltaics ends up generating surpluses. This surplus of electrical energy is sent to the electrolysis device for hydrogen production and storage. Finally, Case E is a facility corresponds to a large logistics center (offices, warehouses, sales stand, training centers and workshops) of a large automobile and heavy vehicle and bus company. It is located on a campus in Abrunheira, municipality of Oeiras. The installation presents the majority of its electric energy consumption during the day, so that during the day, the production of electrical energy by means of photovoltaics does not generate significant surpluses unless the production installation is slightly over-sized.