# Evaluation of Hydrogen Generation with Hybrid Renewable Energy Sources
## 1 Introduction  
### Background  
Global energy consumption has experienced substantial growth over the past ten years, with a 100% increase between 2010 and 2020 [1]. The International Energy Agency (IEA) has recently reported that the annual global energy consumption per capita stands at 22,000 kWh. This upward trend is expected to persist due to population growth and improvements in living standards [2]. Notably, approximately 85% of this energy is derived from fossil fuels such as coal, oil, and gas, which release greenhouse gases [3]. To address the global energy demand sustainably and substantially reduce greenhouse gas emissions, renewable energy sources emerge as the most effective and viable alternative. Information provided by the European Environment Agency (EEA) suggests that without the adoption of renewable energy since 2005, carbon dioxide emissions would have been over 10% higher [4]. According to research findings, nearly one-third of global energy consumption can be attributed to the building sector. Nevertheless, the proliferation of householdappliances and the construction of new buildings for various purposes are contributing to the growth of energy consumption [5]. This increased energy demand leads to a rise in greenhouse gas emissions, which is a significant and adverse consequence [6]. Solar and wind energies, as clean and abundant renewable energy sources, hold great promise for integration into buildings to achieve net-zero-energy buildings. However, the effective storage of solar and wind energies is critical for harnessing these clean energy sources. In recent years, hydrogen has gained popularity as a viable means of storing renewable energy [7]. It is projected that the global demand for hydrogen will see a substantial increase by 2050 [8]. Hydrogen possesses several appealing characteristics aside from its evident trait of clean combustion. Notably, it stands out as the most abundant element in the universe (although often inconveniently bonded to other elements such as oxygen or carbon). Of particular importance are its useful properties in terms of relative transportability (e.g., compared to heat) and long-term storage capacity. This last point is beneficial not only for the intermittency problem described above but also for energy security and the resilience of systems in a broad sense. Hydrogen appears to have both technical and economic advantages for long-term storage [9]. Moreover, hydrogen is characterized by its high calorific value, lightweight properties, and high gravimetric energy density, which offers a renewable energy source that can aid in phasing out the use of fossil fuels [10]. As a result of the growing interest in hydrogen as a clean and carbon-free energy source, there have been numerous endeavours to integrate it into buildings for long-term energy storage [11]. A hydrogen energy system typically includes solar panels and wind turbines for generating the required electrical load for the building, an electrolyzer for hydrogen production, a hydrogen storage tank, and a fuel cell for converting electrochemical energy into electrical energy.