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By Terry Bickham, Vice President, Engineering and Business Solutions, Green CHP
The promise of the hydrogen economy is emerging as a beacon of hope, promising clean and efficient energy production with minimal environmental impact. However, with a renewed focus on hydrogen production, it becomes evident that not all methods are created equal. While hydrogen holds immense potential as a versatile and sustainable energy alternative, the way it is produced plays a critical role in determining its environmental footprint. While current practices face tradeoffs in terms of environmental footprint, efficiency and cost, PV-electrolysis stands out as a promising potential solution, offering a straightforward approach to sustainable hydrogen production.
The Rise of Hydrogen Energy Systems
In recent years, the environmental consequences of conventional energy production have become increasingly apparent. The adverse effects of pollutant emissions have spurred the search for alternative energy sources. Among these alternatives, hydrogen energy systems have emerged as one of the most promising solutions.
Currently, hydrogen serves primarily as a chemical substance rather than a fuel, finding application in various industrial processes such as oil refining and chemical production. However, as global demand for energy continues to rise, particularly in sectors such as transportation, fertilizers, and chemicals, the demand for hydrogen is expected to escalate as well.
In recent years, there has been growing momentum towards adopting hydrogen as a renewable energy source. This shift reflects a broader recognition of the need to transition towards cleaner and more sustainable energy systems to mitigate climate change and reduce dependence on fossil fuels.
Hydrogen energy works by harnessing the chemical energy stored in hydrogen molecules to generate electricity or power various applications. When hydrogen is burned, it undergoes a chemical reaction with oxygen (O2) from the air, producing water (H2O) and releasing energy. Hydrogen can be utilized in internal combustion engines, blended with or in place of natural gas, or in hydrogen fuel cells to generate power. Both processes produce energy and water vapor (H2O) as the only byproduct, making hydrogen combustion a clean and environmentally friendly process. This makes hydrogen a promising candidate for transitioning to a low-carbon energy economy and reducing greenhouse gas emissions. However, challenges such as hydrogen production costs, storage, and infrastructure must be addressed to realize the full potential of hydrogen as a renewable energy solution.
Before hydrogen can be burned, it must first be produced. Hydrogen can be obtained through various methods, including steam reforming of natural gas, electrolysis of water, biomass gasification, or through other renewable sources. Once produced, hydrogen must be stored and transported to its point of use. Hydrogen is typically stored either as a compressed gas in high-pressure tanks, as a cryogenic liquid at extremely low temperatures, or in solid-state materials such as metal hydrides.
The Environmental Imperative: Rethinking Hydrogen Production
The problem with hydrogen as a renewable energy source, particularly concerning greenhouse gas (GHG) emissions, lies primarily in the methods used for hydrogen production. While hydrogen itself burns cleanly, the processes involved in its production often result in significant emissions of GHGs, particularly carbon dioxide (CO2).
Most of the hydrogen today is produced through steam reforming of natural gas. This process involves reacting methane (CH4) with high-temperature steam (H2O) to produce hydrogen (H2) and carbon monoxide (CO). The carbon monoxide is then further reacted with steam to produce additional hydrogen and carbon dioxide.
Overall, steam reforming results in the release of large quantities of CO2 into the atmosphere, making it a significant contributor to GHG emissions. For every kilogram of hydrogen produced through steam reforming, 9-12 kilograms of CO2 are emitted, depending on the specific process and efficiency.
To mitigate the GHG emissions associated with steam reforming, carbon capture and storage (CCS) technologies can be employed to capture CO2 emissions and prevent them from entering the atmosphere. However, implementing CCS adds complexity and cost to the hydrogen production process, making it less economically viable compared to conventional steam reforming methods.
While steam reforming is currently the most common method for hydrogen production due to its cost-effectiveness, there are alternative methods that produce hydrogen without emitting GHGs. These include electrolysis of water using renewable energy sources such as solar power.
The Quest for Green Solutions
To address the GHG emissions associated with hydrogen production, there is a growing emphasis on the development and adoption of green hydrogen production methods. Green hydrogen refers to hydrogen produced using renewable energy sources or processes that do not emit GHGs. This transition is crucial not only for reducing carbon footprints but also for mitigating other pollutants associated with combustion, such as sulfur dioxide, nitrogen oxides, and particulate matter.
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While the concept of green hydrogen production holds immense promise, current technologies face significant challenges in terms of efficiency and cost. Among the various methods explored, one approach stands out as a viable off-the-shelf solution: PV-electrolysis.
PV-electrolysis, which combines photovoltaic (PV) power generation with water electrolysis, offers a straightforward and sustainable method for hydrogen production. This approach utilizes readily available components to convert solar energy into hydrogen, offering a renewable and emissions-free alternative to traditional production methods.
Although the individual components are well established, the challenge is a matter of operating costs, footprint, and efficiencies. Electricity for hydrolysis is the largest operating cost both in terms of capital dollars and land use. Planning factors for land use in solar PV installations range from 5-8 acres per megawatt (MW). The solar field footprint for an electrolyzer to produce the hydrogen needed to operate a 1 MW internal combustion driven generator is a 25-40 acre planning factor.
The opportunity represented in developing the green hydrogen ecosystem led to the Department of Energy’s Hydrogen Earthshot with the stated goal to “reduce the cost of clean hydrogen by 80% to $1 per 1 kilogram in 1 decade ("1 1 1")” from the current $5/kilogram. One path to achieving economic viability is to reduce the power required per kilogram of green hydrogen without sustainability tradeoffs for the improved efficiency.
Hybrid Solar PVT Panels: A Path to Sustainable Hydrogen Production
One promising avenue for realizing the potential of green hydrogen lies in the integration of hybrid solar photovoltaic-thermal (PVT) panels. Unlike conventional solar panels, which convert sunlight directly into electricity, PVT panels combine photovoltaic and thermal elements to simultaneously generate electricity and harvest heat. By combining the proven concepts of solar PV and solar thermal collectors in a single module, up to four times the solar energy can be harvested per acre.
By leveraging this hybrid technology, PVT panels offer several advantages for hydrogen production:
Enhanced Efficiency
PVT panels integrate both photovoltaic (PV) and thermal (T) elements into a single module, allowing for simultaneous electricity generation and heat harvesting. By combining PV and thermal elements, PVT panels can achieve higher energy conversion efficiencies compared to standalone PV systems. This is because PVT panels utilize the heat generated by sunlight to supplement electricity production, maximizing overall energy output per unit area of panel.
Improved Hydrogen Production
The fundamental driver of the electrolysis process is increasing the energy state of water molecules, splitting the water molecules (H2O) into hydrogen (H2) and oxygen (O2), The thermal energy generated by PVT panels can be utilized to pre-heat the water feedstock for electrolysis, reducing the electrical energy input required to achieve electrolysis. In laboratory conditions the efficiency improvement or reduction in power required for electrolysis has been in the range of 10%.
Scalability and Versatility
PVT panels can scale to meet varying hydrogen production needs, making them suitable for both large-scale industrial applications and smaller decentralized systems. Additionally, PVT panels can be integrated into existing solar infrastructure, allowing for seamless integration with grid-connected or off-grid hydrogen production facilities. Integrating PV and thermal components into a single system streamlines installation and maintenance processes, reducing overall costs associated with hydrogen production.
Renewable and Sustainable
Since PVT panels utilize sunlight as their primary energy source, hydrogen produced through PV-electrolysis using PVT panels is considered green hydrogen. The entire process is emissions-free and environmentally sustainable, offering a viable solution for reducing GHG emissions and promoting renewable energy adoption.
In recent years, several multi-megawatt plants have been established, such as a 6 MW plant in Mainz in 2015, a 10 MW plant in Fukushima in 2020, and a 20 MW plant in Markham, Ontario by Enbridge-Cummins in 2020. Additionally, there are plans for a 100 MW plant in the UK, expected to be operational around 2025. Achieving the 2025 targets for hydrogen costs, proposed by the U.S. Department of Energy at $7 per kilogram for refueling and $2 per kilogram for production, presents significant challenges for certain applications. Hybrid thermal solar solutions is one important strategy to achieve these targets.
Combined Power and Hot Water Generation within a Hydrogen System
PV-electrolysis, employing hybrid solar photovoltaic-thermal (PVT) panels, offers significant advantages for industrial and commercial applications, especially in settings where there is a demand for both electricity and hot water.
Green hydrogen has numerous industrial applications, including chemical synthesis, metal refining, and fuel cell technologies. By integrating electrolysis units with PVT panels, industrial facilities can generate hydrogen on-site using renewable energy, reducing dependence on fossil fuels and minimizing carbon emissions.
PV-electrolysis systems harness solar energy to simultaneously generate electricity and hot water. In industrial and commercial settings where there is a constant demand for both power and hot water, this dual functionality can be highly advantageous. Many industrial processes rely on the availability of hot water or steam for various heating applications, such as sterilization, cleaning, and heating of equipment or materials. PV-electrolysis systems can supplement or replace conventional heating methods by providing a reliable and renewable source of hot water.
For manufacturing and commercial businesses, on-site power generation offers several benefits, including reduced electricity costs, increased energy resilience, and greater control over energy supply. PV-electrolysis systems enable businesses to generate their own electricity and hot water on-site, reducing reliance on the grid and mitigating the risk of power outages. This can be particularly advantageous in remote or off-grid locations where access to reliable electricity and hot water may be limited.
Here Comes the Sun
The sun provides an abundant and limitless source of energy. Every hour, enough sunlight reaches the Earth's surface to meet global energy demand for an entire year. This abundance ensures that solar energy can be harnessed at scale to power a wide range of applications, from residential rooftops to large-scale solar farms.
Solar energy is freely available to anyone with access to sunlight. Unlike conventional energy sources that require extraction, transportation, and processing, solar energy is harvested directly from the sun's rays. This accessibility makes solar power an attractive option for communities and regions seeking to enhance energy security and independence.
PV-electrolysis utilizing hybrid solar PVT panels offers a technically advanced and efficient solution for hydrogen production. By combining PV and thermal elements, PVT panels maximize energy conversion efficiency, improve the thermal efficiency of electrolysis, and enable the production of green hydrogen from renewable energy sources. With its scalability, versatility, and sustainability, PV-electrolysis using PVT panels holds great promise for making the hydrogen economy a reality and advancing the transition to a clean energy future.
As we continue to navigate the transition towards a hydrogen economy, it is imperative that we prioritize green solutions that not only meet our energy needs but also safeguard the health of our planet for generations to come. By embracing technologies like hybrid solar PVT panels, we can pave the way towards a brighter and more sustainable future.