Since the Kyoto Protocol in 1997, the climate change awareness and initiatives have been painfully gaining ground around the globe. Renewable energy demand has been in steady progress with its power capacity set to expand by 50% between 2019 and 2024 according to the International Energy Agency 2019 report. Despite this positive shift, the modern renewable energy sources from solar photovoltaic, wind, biomass, geothermal and ocean all combined barely covered 2% of the total final energy consumption (TFEC) in 2017. A solid 80% of the TFEC relies today still on releasing carbon dioxide, particulates and other pollutants (NOx, SOx …) into the atmosphere while burning hydrocarbon fuels. The continuous industrial development, the global population growth and the emergence of the digital information age together have led to a strong energy demand surge and its direct consequence of more greenhouse gas emissions given the current energy mix.
The finite available hydrocarbon reserves with the negative environmental impact of their combustion and the direct high health risks linked to radioactive materials beg the transition to an alternative and more sustainable energy value chain. New ways of thinking and reconfiguring the global energy supply are of urgent order if the global community is to engage collectively and seriously behind the achievement of the long-term goal of the 2016 Paris Agreement in keeping the global average temperature capped to well below 2°C above pre-industrial levels.
The world cannot yet rely on renewable energy conversion alone to economically cover for its TFEC and reverse the emissions trend by decarbonizing its energy consumption. These sources represent an inherent challenge of intermittence. Their lack of a storage medium to better fit the demand curve as they are usually available when they are less needed especially for the more prominent solar and wind sources explains their weak present penetration. Unlike the hydrocarbon or nuclear sources where the chemical substance is the source and the carrier at the same time and both could be converted on-demand with relatively short response times (Gas turbines in minutes, coal and nuclear thermal plants in hours). The current energy mix does in fact reflect the current economic reality and the current technological limitations in terms of extraction, conversion, transport and storage cost efficiencies.
Analyzing the energy sources available on earth one quickly realizes that solar irradiation represents the most abundant and generalized energy source around the planet. One hour of the global influx of solar irradiation if converted with the current photovoltaic technologies is sufficient to cover the global need of electricity for a year. In terms of extraction, conversion and transport this source could provide the TFEC in a sustainable and abundant way. However, its yield distribution curve does not fit the typical demand curve of the electric grid.
The first energy viable solar PV cells made by Bel Laboratories, US in 1954 were 6% efficient. Early 2019, LONGi, China had achieved 24.06% efficient cells breaking the then six-month-old world record of 23.95% held by JinkoSolar, China. In the last ten years, the commercial PV modules doubled in efficiency progressing from 9% to 18%. An even steeper learning curve has been followed on the overall system cost during the same period a residential roof top system for example that would cost over $50 000USD now is priced at less than $20 000USD. Similarly, the levelized cost of electricity (LCOE) of solar PV had followed the same learning curve according to the Fraunhofer Institute. With these positive trends on the learning curves both on the technology efficiency and its cost and the large sunbelt region around the globe, solar PV should represent a larger portion of the global energy mix.
The now cheap electric energy produced by solar PV cannot be stored in useful quantities at a competitive cost given the current state-of-the-art of battery or capacitor banks technologies. Needless to say that battery storage is not the most environmental friendly method for storing and carrying energy in terms of heavy metals soil pollution and its very heavy minerals and scarce rare earths extractive needs. A critical component of the energy value chain is storage. Energy needs to be economically transported and stored at each articulation level of its form’s respective value chain. This logistical component has both technical and economic challenges yet to be solved.
To seriously consider an energy alternative for fully substituting fossil fuels, the alternative energy needs to be sustainable from its origin to its final consumption form, easily accessible and abundant to cover for the global population present and future needs. The alternative also is required to have the least CO2 footprint throughout the transformation stages of its value chain. It should fit the demand curve with no intermittence, adjusts to the demand shifts with a fast response time, safe with limited and controllable risks, portable if possible and when needed. Going through all the known energy sources, it seems that there is no silver bullet to this transition challenge. No single energy source alone is able to fulfill these criteria. However, a combination of energy technologies could present an advantageous energy alternative. Applying the strengths of each source accordingly to each stage of the value chain. Centralized solar and wind could be at the initial electric power production. This electricity could be used both direct into the grid and into producing combustible molecules that could be converted back to electricity or also directly used in thermal engines or fuel cells to produce other forms of usable energy. In this category of molecules, Hydrogen is a good contender with excellent overall system efficiency and cost. Ammonia and Methane could also be considered for this same role; however, they would require multiple transformation stages including Hydrogen production as well.
The most abundant element in the universe, Hydrogen, could help decarbonize the energy supply and act as the missing energy intermediary conversion storage medium for renewables. Coupled to solar photovoltaic energy, it could provide this renewable source with the physical substance for storage and transport. The inherent physio-chemical characteristics of Hydrogen make it an ideal energy carrier in terms of energy density by weight but also they represent some serious technical and safety challenges. Hydrogen is easily flammable and have a low energy density by volume comparatively to the hydrocarbon fuels at ambient conditions. Hydrogen is never directly available and needs to be extracted from its earth captive molecules of water and hydrocarbons both are energivore processes but with different carbon foot-prints. The more economical steam reforming process used to extract Hydrogen from hydrocarbons comes with heavy greenhouse gas emissions bill. Since we have electric energy at reasonable cost from solar PV, electrolysis could be the right pathway to extract Hydrogen from water. Although a very old known process, it is still very inefficient one. The combination of thermal and photovoltaic solar is under studies in many laboratories to create a more efficient and economical Hydrogen extraction from water. This could be a major breakthrough in the integration of Hydrogen into existing renewable energy investments in solar PV and wind to offer a clean hybrid energy system able to answer the requirement of the 21st century energy transition.
The photovoltaic energy finds its source in the sun’s Hydrogen fusion reactions which produces the photons energy carriers responsible for the excitation of the valence band electrons in a semiconductor junction making it capture and conduct the sun’s energy inflow. The same hydrogen could be at the source of an earth’s solution to store back in a closed-loop the sun’s energy into a more stable form of Hydrogen molecules making solar energy an all-around more viable and sustainable energy alternative to fossil fuels. If Hydrogen is the most abundant element in the universe is because it might be the optimum carrier the universe had perfected to manage its enthalpy.
Energy has been the focal point of mankind survival on earth. This is not the first energy transition humanity will live through, and certainly it will not be the last. Giving that we survive again this one through our collective human ingenuity.
By Nawal Moufarreh, 12/2019 Dauphine University Executive MBA, Energy Transition Module.
Great article Nawal! It catches the essence of the current energy and climate crisis. Thank you for this analysis and selection of the solution pathways. Indeed, Hydrogen has still a brighter future.