renewables

By Peter Majewski, Future Industries Institute, University of South Australia

During the past ten years, the uptake of renewable energy systems, especially solar photovoltaic (PV) panels and wind turbines, has significantly increased, and represents a significant change in the way we are generating power on-grid and off-grid. Both technologies have become important means to transition to an electric power generation which is renewable, scalable and free of greenhouse gas emission. 

Recent reports of The World Bank¹ clearly highlight the future demand in mineral and metal resources to manufacture renewable energy systems, and estimates that over three billion tons of minerals and metals are needed to manufacture renewable energy systems. Especially energy storage, which requires an up to 500 per cent increase in production of graphite, lithium and cobalt; and solar PV and wind power systems require significant resources of aluminium, silicon and rare earth elements. 

In 2050, the entire 2018 production volume of nickel will be consumed to manufacture renewable energy systems, and the production of vanadium and indium needs to be doubled to satisfy the demand. In addition, it is estimated that up to 29 million tonnes of copper have to be mined by 2050 to provide sufficient amounts for renewable energy systems. 

All this is required to avoid a global temperature increase of 2°C. However, if more ambitious climate targets are requested – and this is not unthinkable – the required amount of minerals and metals for the manufacturing of renewable energy systems will even be higher. While this demand in minerals and metals represents a significant challenge in future, it also represents a significant economic opportunity for mineral-rich nations and related industries, and the prognosis provides the necessary data for long-term planning in this industry sector.

While these reports are providing an important outlook of what will be necessary in 2050 from today’s point of view, it still needs to be considered that technology change may affect this prognosis within the next 30 years. For example, the report of the Club of Rome in the early 1970s² gave the prognosis that the world will run out of essential minerals and metals within a few decades. However, this prognosis was quickly rendered obsolete by the rise of plastics and polymers, which by now have replaced minerals and metals in numerous applications, by the rise of computers and ICT which transformed manufacturing, and the discovery of more and more minerals and metals resources worldwide.

More challenging may be the aspect of technology change, which may significantly reduce the expected demand in minerals and metals in some areas, but may increase the demand of other minerals and metals in other sectors of renewable energy systems. New concepts for wind power systems, called vortex wind power, may provide wind energy with less demand in materials, especially materials for the wind turbine blades and generators³. However, more significant development may have to be made in order to make such wind power systems compatible with conventional wind power systems.

Currently, 85 per cent of all solar photovoltaic panels are based on silicon. However, new solar PV systems are emerging, which are based on copper-indium-gallium-selenide instead of silicon⁴. While such PV systems may play a more significant role in future, it is not very likely that they will replace silicon-based solar PV systems in the near future, as significant investments were made to build manufacturing capacities for silicon solar PV systems, so they will most likely stay for some time.

It is, therefore, essential to assess the demand in minerals and metals for renewable energy systems over a much shorter time frame in order to identify potential bottlenecks in supply which may affect the spread of renewable energy systems.

Increase of renewable energy capacity until 2025

Together, solar PV and wind power technologies generated 1.44TW of electric power in 2020⁵. Considering the increase of solar PV power and wind power since 2011, it can be expected that by 2025 solar PV power will generate electric power in excess of 1.5TW and wind power in excess of 1.1TW (Figure 1)⁶. 

Figure 1

Figure 1: Increase in the uptake of solar and wind power⁵ and expected further increase until 2025. Grey: wind power; black: solar PV power.

These combined 2.6TW of electric power generated by a conventional black coal plant would produce about 16.4 billion tonnes of CO2. However, as shown in Figure 2 the demand in electric energy increases by almost the same amount between 2020 and 2025, and therefore, the increased solar PV and wind power uptake will most likely only address the increased global energy demand and not reduce greenhouse gas emissions.

Figure 2: World energy consumption. Source: US Energy Information Agency⁷.

Compared to conventional electric energy generating technologies, the energy density in kilograms of weight per watt generated by solar PV or wind power systems is very low. Compared to coal and gas, solar PV requires about five to ten times more essential materials and wind energy requires nine to 18 times more⁸. This only considers the essential materials for the actual power generation like copper, silicon and other metals. If additional necessary materials used in the systems are included, like glass and aluminium for solar PV panels, fibreglass composites in wind power, and steel for the mounting the solar PV systems or building the wind turbine towers, the ratios are much larger. 

Materials demand for solar photovoltaic power until 2025

Solar PV power generation has significantly increased worldwide between 2015 and 2020 by 490GW⁵. This means that – considering a state-of-the-art solar PV panel during this time period produced 300W to 350W – a staggering 1.4 billion to 1.63 billion solar PV panels were installed during this time period worldwide. 

At a usual weight of a solar PV panel of about 18.5kg⁹, to achieve this, 17.6Mt to 20.5Mt of tempered glass, 3.9Mt to 4.5Mt of aluminium for the frame of the panel, 0.78Mt to 0.9Mt of silicon for solar cells, and 0.26Mt to 0.3Mt of copper for the junction box, and 3.4Mt to 3.9Mt of polymers for waterproofing were consumed. In total, 25.9Mt to 30.1Mt of materials. 

However, in regards to copper, the numbers are even higher for solar panel systems due to the interconnection of the panels and connections to the storage battery and grid. It is estimated that about 4.6 tonnes of copper per megawatt generated is needed for complete systems⁸. Considering this number, the amount of copper consumed is about 2.25Mt. In addition, about 15Mt of steel for the mounts of the panels in complete systems were consumed.

By 2025, as outlined above, the expected installed capacity of solar PV power generation will have increased by about 800GW to about 1,500GW worldwide. Considering that the newest panels are capable of producing an output of 350-400W, it can be expected that in addition to the recently installed 1.4 billion to 1.63 billion panels another two billion to 2.3 billion panels need to be manufactured and installed during the time period between now and 2025. This would see a demand of 25.2Mt to 28.9Mt of tempered glass, 5.5Mt to 6.4Mt of aluminium, 1.1Mt to 1.3Mt of silicon, 0.37Mt to 0.42Mt of copper, and 4.8Mt to 5.5Mt of polymers. The demand for copper will reach between about 4Mt to 4.4Mt, and for steel about 24Mt when complete solar systems are considered, as outlined above.

While silver is used in older solar PV panels, it has gradually been replaced in manufactured panels. Therefore, silver demand for solar panel manufacturing over the coming years is not considered in this discussion.

Materials demand for wind power until 2025

Wind energy has been the second biggest renewable energy producer after hydro energy over the past 20 years. However, it can be expected that it will be overtaken by solar PV power in the near future. Due to better and more predictable wind resources offshore, wind power is being increasingly generated by offshore wind farms with foundations embedded in the ocean floor, or using new floating wind turbine technology. However, due to higher costs for offshore wind farms, onshore turbines remain the dominant technology. 

During the past  35 years, wind turbines have become significantly taller and more powerful. The world’s largest wind turbine currently is the 260m-tall Haliade-X offshore turbine. It features either a 14MW, 13MW or 12MW capacity, a rotor with a total diameter of 220m and three 107m-long blades.

In 2020, 733GW of wind power was generated worldwide⁵. During the time period between 2015 and 2020, the wind power capacity increased by about 317GW. In the near future, the expected increase in wind power capacity is about 400GW resulting in a total capacity of above 1,100GW to 1,200GW by 2025 (Figure 1)¹º. 

As for solar PV power, this increase of 400GW in capacity will result in significant demand in materials. Considering the current state-of-the-art wind towers, the expected increase would require the manufacture and installation of additional 30,000 wind towers of Haliade-X size or  130,000 of the state-of-the-art smaller 3MW onshore wind towers by 2025.

The demand in materials varies between the various types of wind towers. Older wind turbines apply a gearbox between the rotor and the generator. Newer wind turbines are mainly manufactured using a direct drive, i.e. gearbox free, power transmission to the generator. While removing the gearbox provides a significant weight reduction by reducing the amount of steel for the turbine, direct drive turbines require higher amounts of copper of 3000t to 5000t per gigawatt generated as well as higher amounts of rare earth elements for the permanent magnets (100 to 240t per gigawatt generated) (Table 2). 

Table 2: Materials in direct drive wind turbines¹¹. Numbers in tons/GW capacity.

Based on the data given by the International Energy Association⁷ and the European Commission¹¹, at the expected increase of about 400GW of wind power capacity, the expected demand in rare earth elements can be calculated to be between 40,000 tonnes and 96,000 tonnes between now and 2025. For copper, the demand would be between 1.2 and 2Mt. About 2.2Mt of zinc and between 48Mt and 52Mt of steel would be required. Demand in minor components of the wind turbines would be 0.2Mt to 0.4Mt of aluminium, 0.12Mt of nickel, 0.04Mt of molybdenum, 0.32Mt of manganese, and 0.2Mt of chromium.

At the current state of wind power technology, it is estimated that eight to 13.4 tonnes of wind turbine blade materials is required to generate one megawatt of electric power¹². Therefore, about 3.2 to 5.4Mt of glass fibre and carbon fibre composite material for wind turbine blades would be demanded until 2025. 

Discussion

While the benefit of using solar PV and wind power to reduce greenhouse gas emission during electric power generation is widely acknowledged, the required demand in materials to satisfy the expected increase in power generation by these technologies is of concern (Table 1). 

Table 1: Materials in solar PV panels. Average weight of an about 400W panel is about 18.5kg⁹.

To put these amounts of materials in some context, it can be calculated that the required amount of aluminium would be sufficient to build 100,000 airliners of the newest type of Boeing 737¹³. The amount of steel would be enough to build almost 1,200 Golden Gate Bridges, and with the amount of copper required it would easily be possible to connect planet earth with the sun with a 1.5mm solid copper wire. 

However, compared with the production numbers of these materials in 2020, shown in Table 3, the situation appears less critical. Nevertheless, the expected future demand in these materials represents a significant additional demand which can be considered a reasonable challenge, especially in regards to rare earth elements, as the demand competes with the increasing demand of other essential technologies such as information and communication technologies. Nevertheless, the prognosis also presents a short-term business opportunity for the producers of these materials and mineral-rich nations.

Table 3: Material demand between now and 2025 at an expected increase in power generation of about 800GW for solar PV power and 400GW of wind power. Numbers in Mt.

Given the significant demand in these materials within a rather short timeline, it is essential that markets, supply lines, and manufacturers of these materials and renewable energy systems are prepared to achieve this. In addition, governments need to create and ensure undisrupted supply lines and trade agreements for these goods to guarantee the expected increase in renewable energy capacity. The consequence would be an undesirable significant increase in greenhouse gas emission due to increased conventional power generation.

It has also to be considered that at one stage, in about 15 to 25 years, the renewable energy systems, which are currently installed, and those which are to be installed within the next few years, will reach the end of their operational life and will eventually go to waste. Most of the applied metals will go through recycling, but some of the materials are either very difficult to recycle or it is not economical to recycle them. One example is glass fibre composite material. The amount of this material consumed in wind turbine blades which were installed since 2015 and are expected to be installed until 2025 is about 5.7Mt to 9.6Mt, and causes a significant challenge for end-of-life management and recycling²¹. 

Silicon from existing solar PV panels is currently only recycled in very small amounts. The combined amount of silicon consumed for manufacturing solar PV panels since 2015 and required for the solar PV panels until 2025 is expected to be about 1.88Mt to 2.2Mt. In this context, economic recycling processes for silicon from solar PV panels is, therefore, important to ensure that this valuable material is incorporated into the circularity of the economy and reused for the manufacturing of solar PV panels or other silicon-based products such as silicon carbide ceramics.

Some materials are used across both technologies, such as copper, and some materials are crucial for generating electric power by the technologies, such as silicon and rare earth elements. These materials can be considered as absolutely essential, while others are only used for structural components, like aluminium and steel. Materials, like aluminium, which are not essential for directly generating electric power, can therefore be replaced by other materials, or made redundant by changing the design of a solar panel. Developments in this direction are already ongoing, such as the emerging organic solar cells²², floating solar panels and solar farms, which may require more light weight designs²³, and build-integrated solar panels²⁴.

References

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