The most important technologies for desert power are already in practical use. While there is, of course, still room for improvement, the current state of technology has reached a high level of maturity for application. For instance, two key technologies for desert power, namely solar thermal power plants and high-voltage direct current (HVDC) transmission lines, have been in practical use for a long time.
There are numerous ways to harness energy from deserts, including traditional photovoltaic (PV) systems and wind turbines. These technologies can produce particularly low-cost but fluctuating electricity, which can either be used locally or transmitted to metropolitan regions.
However, for contributions from the deserts of North Africa to the European electricity market, solar thermal power plants are the most attractive option. These plants can provide baseload power in the gigawatt range 24 hours a day with minimal fluctuations or balance the significant variability in power generation from PV and wind through dispatchable electricity.
Solar thermal power plants are capable of generating electricity as reliably as conventional power plants. They operate similarly to conventional plants, with the key difference being that the steam driving the turbines is generated using the sun’s heat rather than fossil fuels. To achieve this, solar radiation is concentrated, which is why these facilities are also referred to as CSP plants (CSP = Concentrated Solar Power).
If a single, large solar thermal power plant were built to supply electricity for the entire world, it would cover less than 1% of the Sahara’s area! In practice, many smaller plants would be constructed, but this comparison underscores the immense potential of desert regions.
Concentrated Solar Energy
To concentrate solar radiation, either parabolic troughs with crescent-shaped mirrors are used, or sunlight is focused by a large number of mirrors onto the top of a centrally located tower.
In parabolic trough systems, the concentrated sunlight heats a tube through which a special oil or other heat transfer medium is pumped. In solar tower power plants, liquid salt is currently the preferred heat transfer medium. This medium is used in a heat exchanger to produce steam to drive a turbine. Some designs even generate steam directly for industrial heat applications or electricity production.
Contrary to popular belief, much of the Sahara is not covered by sand; most of it consists of barren rock. As a result, sandstorms and shifting dunes pose no significant issues for solar thermal facilities. If a sandstorm does occur, the mirrors can be moved to a protective position.
Finally, Solar Energy at Night!
A portion of the heated heat transfer medium is stored either directly in a thermal storage unit or transfers its heat to a storage system. This allows vast amounts of energy to be stored for periods of up to several days at very low cost. This stored heat solves one of the biggest challenges of solar energy: electricity generation during the night.
Solar Thermal Power – The Strong Partner for PV and Wind
Thanks to the ability to store solar heat, CSP plants are largely weather-independent and can thus provide balancing power. This is ideal for accelerating the further expansion of PV and wind energy.
Additionally, the turbine rotors and attached generators in CSP plants, with their large mass and high inertia, help buffer short-term fluctuations in grid frequency, thereby stabilizing the electricity grid. This function is identical to what traditional gas or coal-fired power plants offer and is becoming increasingly important as more variable renewable energy sources feed into the grid.
Advantages of Solar Thermal Power Plants
Low Water Consumption
Water requirements for CSP plants are a minor concern in desert environments. In newer facilities, steam is cooled using air or, at coastal sites, condensed using seawater, creating a closed water cycle. Cleaning the mirrors is done using methods designed to minimize water consumption.
Ongoing Development of Solar Thermal Power
CSP plants have been and continue to be steadily improved. Most components have become cheaper and more efficient, mirror control software has become increasingly sophisticated, and overall system design is continually refined. However, the development of CSP systems is far from complete.
To transport desert power, for instance, to Central Europe, the technology of high-voltage direct current (HVDC) transmission is particularly well-suited. HVDC avoids the inductive and capacitive resistance that causes significant losses in alternating current (AC) lines over long distances. HVDC transmission lines are already widely used in Europe, such as for connecting islands to the mainland or linking the Scandinavian power grid with Central Europe’s grid via subsea cables in the North and Baltic Seas. For an HVDC line approximately 3,000 kilometers long—the distance from the Sahara to Germany—the expected transmission loss would be less than 10%.
At existing or newly constructed substations, the direct current can be converted into alternating current and fed into the local power grid.
Hydrogen is an extremely versatile energy carrier. It can be used in industrial processes, in fuel cells for electricity generation, or even burned in power plants similarly to natural gas.
The Myth of Hydrogen
Contrary to popular belief, hydrogen technology is neither futuristic nor particularly dangerous. For nearly a century, hydrogen has been used on a large scale in the chemical industry, especially in fertilizer production. Hydrogen is also used in other industrial applications, as well as in rockets and vehicles.
While hydrogen is a small atom, this does not mean that hydrogen gas (H₂) can magically pass through barriers. The applications mentioned above face minimal issues with hydrogen leakage into the environment. Similarly, the risk of explosions with hydrogen is no greater than that associated with conventional fossil fuel technologies.
Hydrogen Production
Currently, hydrogen is primarily produced from natural gas, though other hydrocarbons can also be utilized. Methane serves as a typical example:
The methane (CH₄) in natural gas is heated together with water (H₂O). Under high pressure, the steam reacts with methane to form hydrogen (H₂) and carbon monoxide (CO). This process is called steam reforming. The carbon monoxide is then burned to carbon dioxide (CO₂) to supply the necessary process heat. While this method produces pure hydrogen for chemical reactions, it also releases carbon dioxide.
Electrolysis offers an alternative. In this process, distilled water is split into hydrogen and oxygen using electricity. Essentially, two metal electrodes are submerged in a water-filled basin and supplied with current. While commercial electrolyzers are more complex, the principle remains straightforward.
Desert power is particularly well-suited for hydrogen production, though water consumption must also be considered. The hydrogen or a derived energy carrier would then need to be transported to the end-use facilities to provide energy where needed.
A widely known material but scarcely considered as an energy carrier, iron holds significant potential to store solar energy from deserts and make it transportable worldwide. Iron-based fuels could globally replace coal as an energy carrier—leveraging the existing infrastructure for coal, including ships, power plants, and power grids.
How Can Iron Burn? Iron components or bars, of course, do not burn under normal conditions. However, finely ground pure iron powder can be ignited and burned. A similar phenomenon occurs with flour: while heaped flour is difficult to ignite, dispersed flour particles in the air are highly combustible. Iron powder is also used in fireworks to produce bright yellow sparks.
Iron burns – CO2-free!
Short Video: https://youtu.be/2eavRtrsD8o
CO₂-Free: Iron as a Replacement for Coal
Iron powder enables the generation of a continuous flame, resembling the combustion properties of coal. In coal-fired power plants, coal is pulverized, blown into a boiler, and burned to generate steam, which drives turbines for electricity production.
A similar process applies to iron powder. The powder is injected into the boiler and combusted at a controllable temperature. Depending on requirements, the combustion temperature can match or even exceed that of coal. Unlike coal combustion, which releases large amounts of CO₂, ash, and pollutants, the combustion of iron produces only iron oxide (“rust”) as a residue—making it a CO₂-free process. Additionally, tests indicate that iron combustion produces significantly lower nitrogen oxide emissions than coal. The rust, in powder form, is transported away as a “byproduct” in much the same way as ash from coal boilers.
A Circular System: Rust Back to the Desert
This is where solar energy, particularly in deserts, comes into play. The concept would not be sustainable if the fuel could only be used once. Rust is non-combustible, non-toxic, non-corrosive, and does not require pressurized storage, making it easy to transport back to deserts using nearly any ship or other transport system.
Once the iron oxide (rust) reaches the desert, renewable energy is used to convert it back into pure powdered iron. This process involves hydrogen, which removes the oxygen from rust (a reduction process) and converts into water vapor in the process. This method, already established in the steel industry for producing green steel, is a proven technology. In the future, reduced iron powder could potentially also be produced directly using electrolysis powered by electricity.
Why Choose Iron Over Hydrogen?
Why take the indirect route via iron when hydrogen is already available? Is this just an added layer of complexity?
Hydrogen plays an essential role in the energy transition, both as a material and an energy carrier. However, hydrogen as a fuel comes with several intrinsic drawbacks:
Iron Avoids These Limitations:
Retrofitting Coal Plants for Iron Powder
The conversion of coal-fired power plants to use iron powder appears relatively cost-effective. Only a few components would need to be replaced, allowing existing power plants to continue operating with iron as a fuel—without emitting CO₂.
Hydrogen Remains Essential—In a Different Role
Despite iron’s numerous advantages as an energy carrier, hydrogen remains indispensable for reducing iron oxide to iron. Beyond this, hydrogen will continue to play a key role as a chemical feedstock and as a gaseous or liquid fuel for other applications, such as peak-load power plants.
For large-scale electricity generation, bridging energy shortages during periods of low renewable energy output, and the seasonal storage of massive energy quantities, however, iron emerges as a far more suitable energy carrier.
Scientific Advancements in the Concept
The concept of metallic energy carriers is currently being explored by several research institutions, including TU Darmstadt and the Karlsruhe Institute of Technology. Demonstrators for industrial-scale applications are under construction or in the planning stages in Germany and the Netherlands. Iron as an energy carrier offers a promising means of making renewable energy globally accessible—and could make a decisive contribution to the energy transition.
More Information on Metal Energy Carriers: TU Darmstadt Präsentation Clean Circles
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