From fossil fuels to low-carbon technologies, the energy transition has been realized worldwide during the last decades. Nowadays, the transition has become more critical because of some reasons such as risks to supply chains, increasingprices of fossil fuels, etc. When talking about energy transition, considering material requirements is crucial. Becauseunless required materials are provided, the countries cannot sustain the transition. A conceptional analysis is the first step of an article series about the materials in this article. Knowing concepts is vital due to understanding and discuss ona topic efficiently. So concepts that are related to the topic being discussed in the article.
The Rare-Earths Elements (REEs): Their atomic numbers are between 57-71. They are also known as lanthanides. Yttrium can be added to the elements because of the elements' same chemical and physical features. When the elements were found out, they were called 'earths.' Although they are quite abundant worldwide, they were named rare becausethey were rare according to other 'earths' (e.g., Magnesia). They exist abundantly in the Earth's crust, but the concentration of reserves is not high, so they are not economical. They are essential for energy transition because some are required for magnets used in wind turbines and electric motors.
The Precious Metals: They are rare, and their economic value is high. Gold and silver are known as precious metals. Furthermore, platinum group elements (PGMs) (ruthenium, rhodium, palladium, osmium, iridium, and platinum) are also considered precious metals in some sources. Gold and silver are essential for the electronics sector because of their high conductivity. Silver is also a good reflector and is used in the solar sector. Platinum is used as a catalyst which is vital for hydrogen production.
The Base Metals: Copper, lead, nickel, tin, aluminum, and zinc are accepted as base metals, besides steel is also included in the group in some studies. If we compare the metals with the precious metals, base metals are relatively abundant in nature and cheaper than precious metals. However, their conductivity and resilience against oxidation are not high. Copper is vital metal for electric wires and motors. Aluminum and steel are used for the structure of energy plants and vehicles. Nickel and lead are usable for different kinds of solar technologies. The mentioned elements are illustrated in the periodic table in Figure 1.
Figure 1: The Different Kinds of Elements in Periodic Table
The Critical Raw Materials: There isn't a generally accepted critical evaluation method for materials. Different sources measure criticality depending on various methods. For example, European Commission (EC) calculates the 'criticality' by considering economic importance and supply risk concepts described by the EC Report. In another study, geological and geopolitical supply risk and vulnerability to supply risk, the replaceability of a specific material, and recycling ability are used for the 'criticality' calculation. The critical raw materials list of EC is shown in Figure 2.
Figure 2: 30 Critical Raw Materials according to the EC
Besides the material type and definitions, some terms are used with the materials, such as reserve and resource. According to the United States Geological Survey (USGS), resource means a concentration of naturally occurring solid, liquid, or gaseous material in or on the Earth's crust in such form and amount that economic extraction of a commodityfrom the concentration is currently or potentially feasible. On the other hand, reserves are defined as the part of the reserve base that could be economically extracted or produced at determination. The term reserves need not signify that extraction facilities are in place and operative. Reserves include only recoverable materials. So, while 'resource' is a broader term, 'reserves' is an economic and demonstrated part.
On the other hand, according to EC Report, the most outstanding descriptional difference is the licensing permit situation. If a licensing permit is available, it is accepted as a reserve. However, if the licensing permit is probable, it is determined as a resource.
In conclusion, there are different descriptions of terms that relate to materials. Some articles and institutions suggest definitions according to their assessments. Concepts are important to argue, speak and produce new concepts on a topic. Furthermore, It also seems that the terms will be heard and argued more frequently in the following years. So, an agreement should be made on the definitions to discuss the topic.