Could we ever make a completely clean energy system? Or, at least, could we build one that allowed an entente or a peaceful co-existence with a thriving and exuberant natural world? The pioneers of renewable energy were searching for that decades ago, as they plunged ahead with their solar photovoltaics (PV) and wind turbine experiments and projects in a world that seemed deaf and blind to their driving concerns. The researchers, policy-makers, scientists, and entrepreneurs who spear-headed this movement deserve to feel a sense of deep satisfaction for their victory. The two most sustainable sources of energy are now the cheapest and are getting cheaper. They now invite us on a path leading out of the fossil age and into the solar age.
The world is installing solar panels at an exponential rate. In April 2022, it reached 1 Terawatt of installed capacity. With continually decreasing costs, and driven by both climate urgency and energy security needs, global installed capacity is expected to double in 3 years. We have indeed entered the Terawatt age that brings a vision of a vastly expanded renewable energy resource, opening up new horizons and possibilities. Wind is ramping up yearly as well.
The problem that arises, however, is the irregularity of the resources. Near the equator, year-round, there are 12 hours of day and 12 hours of night. In these sunny climes, a battery system can easily extend the hours of electricity gleaned during the day for use at night. Further towards the poles, this gets trickier. Daylight diminishes in the fall to very low winter levels. Solar PV becomes inadequate faced with the change of seasons. Indeed, the demand for energy could triple in winter, due to the need for heat in colder latitudes. Luckily, in these regions, wind energy can come to the rescue. Wind and solar PV are complimentary sources of power, with the wind often picking up when the sun goes down or hides behind the clouds. But not always. The wind can die down even in the long winter months. The Germans, who have installed more wind turbines and solar panels than most, call this double disappointment “dunkelflaute,” or, the dark doldrums, the dark lull.
When wind and solar are inadequate, other renewable resources can help, if available. Geothermal, pumped hydro, hydroelectricity, and bioenergy resources vary greatly country to country. Bioenergy, especially from the injection of biomethane captured from biogas plants, can add to the methane volumes in the gas grid. But even if this were ramped up considerably, it is limited by arable land, the need for food and feed, and a place for nature. The wastes and residues left for energy are not infinitely scalable.
But are we destined to revert to fossil fuels for the dunkelflaute or for the winter? Batteries are unsuitable for seasonal storage since they drain over time, and they require a lot of material for the storage they provide. Long-term storage for electricity is very difficult.
German scientists Michael Sterner and Michael Specht came up with the novel idea of connecting the electricity sector to the gas sector. Excess renewable electricity could be used to split the water molecule into streams of hydrogen and oxygen in a machine called an electrolyzer, in imitation of the process of photosynthesis performed by plants. This “green” hydrogen, made without fossil fuels, could then be mixed with recycled carbon dioxide (CO2) to make methane, the main part of natural gas. In this form, it could be injected into an existing natural gas grid and its vast storage capacity. From there, it could be made available for heating, for industrial uses, or mobility. The process could also be reversed. The gas could be fed into gas-fired power plants to generate electricity.
Two sectors that had previously co-existed on the same territory could now form a unified system, capable of bypassing fossil fuels altogether. The gas grid and the power (electricity) grid could now exchange in both directions. Gas-to-Power, of course, is an old pathway, as gas from the gas grid feeds some power plants. Power-to-Gas, however, is new and offers huge storage and uses for excess renewable electricity. Indeed, we could overbuild renewable energies so that a large stream of electrons (non-storable electricity) would become molecules (easily storable and transportable) methane. The intermittency problem is now solved. Renewable electricity could pass into the gas system and reemerge in later times and seasons when renewable electricity is scarce.
The concept of Power-to-Gas has expanded in the last 12 years or so to a whole range of products that can be made from the basic ingredients of electrolytic (green) hydrogen and carbon dioxide. These products often are preceded by an “e” to point out that their origin was neither fossil, nor biogenic, but electrical. E-methane was joined by e-gasoline, e-kerosene, e-methanol, e-diesel, and e-ammonia. Some of these are made for the chemical industry, so that we can now substitute e-feedstocks for fossil feedstocks. These e-fuels (or powerfuels) now provide a third pathway forward in the solar age. Their versatility brings renewable energy into applications and uses that were unimaginable before. Compared to fossil energy and bioenergy, they touch lightly the earth, forming a semi-closed, circular system with great perspectives to scale up.
An important caveat should be mentioned here. Each transformation of energy or energy conversion incurs an energy loss. Direct electrification is always more efficient, and should always be prioritized in an energy-constrained world. Switching a large portion of our heating from gas boilers to heat pumps powered by renewable electricity is not only good for the planet in terms of emissions, but it uses less energy overall. Electric cars are also more efficient than their gasoline counterparts, and they are more efficient than a gasoline car even with e-gasoline in the tank. In fact, some estimate that it would take 5 times more renewable energy to run a car on powerfuels than to run an electric car on renewable energy. So not only do electric cars use energy more efficiently than the internal combustion engine cars, but if we make them carbon-neutral through Powerfuels, it would take 5 times more energy just for the fuel. Powerfuels, therefore, should be reserved for sectors that are difficult to run on electricity, such as aviation and shipping, and perhaps heavy-duty trucking.
The vision of Power-to-X (Power-to-a list of products) is relatively new. While some of the technologies required to make powerfuels are well-known, others are less mature. Some, such as electrolyzers, have been used on a small scale for many years, but scaling up is challenging. Powerfuels are therefore mostly in the pilot and demonstration stages. Many companies and research organizations are moving fast to gain experience producing this set of nascent global commodities.
In the south of France at Fos-Sur-Mer, the project Jupiter 1000 began to produce green hydrogen in 2020, testing 2 different kinds of electrolysers together using 1 Megawatt of electricity. Last year they completed the Power-to-gas project by mixing this hydrogen with recycled CO2 captured and purified from the off gases of a steel mill. The new “methaniser” is working well, and now injecting 25 m3 of e-methane per hour into the French gas grid. The project brought together a group of companies to test and improve their parts of the whole system and to learn how to make them all work together at an early commercial scale. This project allows excess renewable energy to be stored in hydrogen, and for carbon dioxide to be reused, halving its impact on the climate. When injected into the grid, it requires no change in infrastructure nor applications.
The winds of southern Patagonia are probably the strongest and most persistent on earth, offering a steady supply of kinetic energy between 60% and 70% of the time, all year round. A clever start-up, HIF (Highly Innovative Fuels) Global has just finished building its pilot project (December, 2022) to tap this resource and convert the wind to e-methanol and then e-gasoline. The project takes wind turbines to produce renewable electricity, which runs the electrolysers that split water molecules into streams of hydrogen and oxygen. The green hydrogen is then mixed with oxygen and recycled CO2 from a brewery in a methanol synthesis reactor to make e-methanol (CH30H). Methanol can be used as a shipping fuel and has several applications in the chemical industry. But at this small plant in Patagonia, the e-methanol is further transformed into e-gasoline and is shipped to Germany and sold to Porsche.
Despite their truly amazing wind resource in south Chili, the HIF project had to adapt to the challenge of being about as off-grid as one could be. The only resource is the fluctuating wind. HIF met this challenge by choosing flexible technologies. The PEM electrolyser can quickly adapt to sudden surges or collapses of the wind. They chose the product methanol because the methanol synthesis reactor can also ramp up and down quickly.
HIF has leased lands in order to install a 15 Gigawatt wind farm and will build up the rest of the infrastructure, including Direct Air Capture of CO2. By 2030, the site will produce at least 72,000 barrels a day of e-gasoline. In parallel, a site in Texas is also underway to take advantage of the Inflation Reduction Act, the skilled workforce, and the rich renewable resources there. Another site near Sydney, Australia, is planned as well. In all, HIF plans to produce 150,000 barrels a day of e-gasoline. By way of comparison, the controversial Willow tract in Alaska may produce 180,000 barrels per day of traditional oil in a far less ecological way.
Other Power-to-X projects are sprouting up all over the world. The cost of electricity is the greatest part of the costs of these projects, so most will be built where there are rich renewable resources. Much of their product will be made for the maritime and aviation industries that require fuel with a high energy density. E-jet, e-methanol, and e-ammonia will be the welcome solutions for these very hard-to-decarbonize modes of transportation.
E-fuels are “drop-in” fuels. They can drop into the places previously manufactured for their fossil counterparts: storage tanks, pipelines, gas tanks, etc. They can give a new raison d’etre for all the infrastructure of the fossil age, without all that fossil carbon. The problem of losing billions of dollars of stranded fossil assets can be partially relieved this way.
The amount of CO2 they release in combustion will be scooped up again by Direct Air Capture for the next round of fuels, creating a circular carbon economy. Compared to their fossil predecessors, they avoid 90% of the CO2 emissions.