Transitioning to Eco-Friendly Cities: The Role of Green Hydrogen in Achieving Climate Neutrality

The Transition to an Eco-Friendly City as a First Step Toward Climate Neutrality with Green Hydrogen

Abstract

A future-oriented city must be eco-friendly while fulfilling social and economic needs. Hydrogen-based technologies offer solutions for reducing CO2 emissions initially, with the potential for complete decarbonization in the long run. Cities need to adopt and integrate these technologies to bridge the gap between hydrogen production and its urban application. This paper analyzes the achievable outcomes of injecting hydrogen into the urban methane gas network, starting with small proportions and gradually increasing over time. A numerical application focusing on Bucharest, Romania—a metropolis with a population of 2.1 million—illustrates these concepts. While fuel cells are less advantageous for urban transport compared to electric battery solutions, the heat generated from hydrogen technologies can efficiently serve residential heating needs. Additionally, storage solutions are necessary for residential use, separate from urban transport, along with developments in electric transport requiring a detailed economic assessment. For electricity generation, gas turbines have proven to be the most effective solution. This paper synthesizes the opportunities presented by hydrogen technologies for future cities.

Keywords

green hydrogen; smart cities; CO2 emissions

1. Introduction

Currently, approximately 57% of the global population resides in urban areas, surpassing 8.1 billion people. Urban agglomerations typically include the populations of cities or municipalities along with adjacent suburban areas. Envisioning a city of the future is complex, as this idea is continually evolving and difficult to define succinctly. A primary objective remains the creation of a city with minimal pollution and effective environmental impact management. Pollution is a multifaceted issue requiring targeted approaches, with the reduction or elimination of carbon dioxide emissions being a well-defined and prioritized goal.

Cities are characterized by high energy consumption and the production of goods and services, which are often accompanied by pollutant emissions, particularly carbon dioxide. In 2023, primary energy consumption rose by 2% compared to 2022, with CO2 emissions increasing by 2.1%. In 2022, emissions from energy production totaled 35,129.6 million tons of CO2, alongside 317.4 million tons from gas combustion for household consumption, culminating in a total of 40,417.9 million tons of CO2 emitted. The EU’s carbon dioxide emission trading scheme was priced at 85.17 EUR/ton of CO2 in 2023.

Globally, hydrogen production in 2023 reached 4,834.9 thousand tons, with green hydrogen accounting for only 147.6 thousand tons. The remainder was produced from fossil fuels, resulting in significant CO2 emissions—10 tons of CO2 per ton of hydrogen from natural gas, 12 tons from petroleum products, and 19 tons from coal. The shift toward hydrogen as an energy carrier in future cities is increasingly viewed as a reliable solution, especially as production costs decline.

2. Objectives of Using Green Hydrogen

The Sustainable Development Goals (SDGs) established in 2015 as part of the UN’s 2030 Agenda for Sustainable Development aim to eradicate poverty and promote sustainable development. Among the 17 SDGs, Goal 7 emphasizes access to clean and affordable energy. The European Union (EU) is committed to carbon neutrality by 2050, and hydrogen serves as a clean energy carrier that can integrate different sectors into a unified energy market.

In 2023, Europe produced 75.8 thousand tons of hydrogen compared to the global total of 4,834.9 thousand tons, with 31.6 thousand tons being green hydrogen. Global hydrogen demand is projected to reach nearly 100 million tons in 2024. The current production of hydrogen is primarily for refining, ammonia production, and methanol, with significant reliance on fossil fuels.

The EU supports hydrogen development by imposing only VAT on this fuel. Two entities—the European Hydrogen Industry and the European Hydrogen Bank—facilitate the production and deployment of green hydrogen. Nonetheless, discrepancies between EU policies and local implementation must be anticipated and resolved.

3. Methodology

To achieve climate neutrality, cities must reduce reliance on fossil fuels that emit CO2. This transition can be facilitated by substituting fossil fuels with hydrogen in transportation, energy storage, and residential heating. The use of electric vehicles and biofuel blends can significantly reduce carbon emissions in transportation.

The study methodology includes transitioning to green hydrogen production and its economic challenges, focusing on its combustion in methane blends. The technology for stable and efficient combustion tailored to residential applications is also addressed. The implications for a city with over 2 million inhabitants are analyzed, emphasizing energy storage and its impact on various sectors.

4. The Particularities of the Combustion of the Methane-Hydrogen Gas Mixture

Hydrogen combustion produces only water vapor and nitrogen when burned with air, contrasting with methane, which generates carbon oxides. The stoichiometric combustion of a methane-hydrogen mixture significantly reduces CO2 emissions. The mixture’s combustion energy is less than that of pure methane due to hydrogen’s lower calorific value.

5. Analysis of the Use of Hydrogen in a Future Eco-City

The successful development of a hydrogen value chain relies on effective production, transportation, distribution, storage, and end-use infrastructure. Integrating hydrogen into existing natural gas systems could minimize capital costs while helping to reduce CO2 emissions. The existing global natural gas infrastructure could be leveraged for hydrogen transport.

6. Simulating Hydrogen Consumption in Bucharest, a Future Eco-City

A simulation of hydrogen consumption during Bucharest’s transition to a zero-emission city indicates significant potential for residential heating and urban transport. The residential market is currently focused on natural gas, but hydrogen blends can be introduced into existing supply chains. The analysis shows a clear pathway for integrating green hydrogen into urban environments.

7. Conclusions

Reducing emissions in future cities is critical for addressing climate change and enhancing urban living standards. Green hydrogen, produced through renewable energy sources, presents a promising solution. Effective policies promoting its use, along with local strategies for production and distribution, are essential for transitioning to carbon-neutral urban environments. The analysis highlights that mixing hydrogen with methane can effectively reduce CO2 emissions and facilitate the shift toward sustainable energy practices.

This paper lays the groundwork for further research into the economic and infrastructural aspects of green hydrogen integration in urban settings, underscoring its role in creating eco-friendly cities.