March 2011

Rare Metals & RenewablesGlobally, the demand for a wide range of rare metals is roaring. Applications such as LCD’s, LEDs and semi-conductors require for example gallium and indium, while solar photovoltaic and wind power also require rare metals. Here we investigated the demand and supply issues for the renewable energy sector.

By Pieter van Breevoort & Rolf de Vos

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are made of silicon, while silver and copper are being used for the cell pasting. The exact material demand varies per manufacturer and type of solar cell.

Thin film PV: There are many types of thin film PV. The most important subgroups are:(i) Amorphous silicon (a-Si), which

is silicon based,(ii) CdTe film, of which the main

constituents are cadmium and telluride;

(iii) CI(G)S film, of which the main constituents are copper, indium, selenium and optionally gallium;

(iv) GaAs, which consists of gallium, arsenic and germanium.

Presently, GaAs still has a near-zero market share, and will probably

LaRge-scaLe dePLoymenT of renewable energy is regarded as an important strategy to reduce human greenhouse gas emissions and increase the security of energy supply. In recent years, concerns related to the future supply of rare metals reached the public arena, triggered by China’s rare earth export restrictions. It is therefore interesting to get an overview of metal demand for renewable energy. Here, we will use the International Energy Agency’s (IEA) BLUE Map Scenario, with a relatively high deployment of renewable energy as a starting point.

critical materialsWe consider a broad range of critical materials that are needed

in emerging technologies. The production of these materials ranges from tens of tons (e.g. for gallium) to millions of tonnes (for copper). The materials are used in many daily applications, ranging from products in industry to households and are of great economic importance.

Semiconductors and related technologies (LEDs, LCDs), hard disks and batteries are applied in a broad range of applications, such as smart phones, screens, computers and electric vehicles. As these applications penetrate more and more into our daily lives, demand for metals such as cadmium, indium, gallium and neodymium increases. On top of this, all the materials mentioned in the table above are also required for renewable power generation, especially solar PV and wind. Material demand for renewable energy has become a subject of interest in recent years (for example in the EU2), as material availability is an issue of economic, political, strategic and environmental importance. It is thus interesting to assess how much rare metals are needed if renewable energy is deployed globally at a high pace.

solar PV TechnologiesThere are two main groups of

solar PV: crystalline PV and thin film PV. The first group is silicon based; the latter is based on a variety of materials.crystalline PV: Crystalline PV currently has the highest share in the global PV market (> 78% of the 2009 market).3 This can again be subdivided into:(i) Multi-crystalline PV and,(ii) Poly-crystalline PV. The cells

... material availability is an issue of economic, political, strategic and

environmental importance

Table 1: overview of Important metals for solar PV & Wind Power

Production in 2009 examples of applications

arsenic 40 ktonnes (Arsenic content) (1) Batteries, fertilizers, solar cells

cadmium 19 ktonnes (1) Batteries, coating, solar cells

copper 15,900 ktonnes (1) Power transmissions and generation

gallium 79 tonnes (1) Laser diodes, LEDs, solar cells

germanium 120 tonnes (1)(fiber)optic systems, chemotherapy, solar cells

Indium 546 tonnes (1) LCDs, solar cells

neodymium 7.3 tonnes (2)Perma-magnets (for wind turbines, electric vehicles), hard disks

selenium 2,280 tonnes (1) Pigment, alloys, solar cells

silver 22 ktonnes (1)Mirrors, jewelry, conductive wiring, coins, solar modules

Tellurium 200 tonnes (1,3) Alloys, rubber processing, solar cellsSources: (1) United States Geological Survey; (2) Fraunhofer, 2007 production5; (3) Own Estimates1

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and are expected to gain an important market share. The main advantage of a direct drive turbine is that it does not contain a gearbox and consequently contains fewer parts. This increases the robustness of the turbine and decreases the frequency of maintenance operations. Especially for offshore wind power this is advantageous, as maintenance is more expensive and complex at sea while turbines should withstand harsher conditions (stronger winds, salt environment, waves).

A possible disadvantage is that the magnets in these direct drive turbines may contain neodymium, which is a rare earth metal. neodymium magnets reduce the overall weight of the magnet and the turbine.

Copper demand, for both the generators and offshore cabling is included in the calculations as well.

solar PV & Wind in the BLUe map scenarioIn the BLUE Map Scenario, renewable energy is deployed at a

relatively high pace, as part of a transition to an energy supply with low carbon emissions. By 2050, 3,000 GW of solar PV is operational and more than 2,000 GW of wind. In this case, solar PV and wind power will both have a share of 12% in the global electricity production. The projected growth of both technologies is shown in Figure 1.

We can see that solar PV grows exponentially until 2030 (with growth rates above 20% per year around 2020). After 2030, a linear growth is envisaged. Wind grows steady, between 35 and 55 GW per year, toward 2050. The contribution of offshore wind capacity increases: by 2050, about 1/3 of the total capacity is located offshore.

The BLUE Map Scenario does not provide details on the types of solar PV, nor the types of wind turbines that are deployed. We therefore have to make a number of assumptions in order to quantify the future material demand for renewable energy.

our assumptionsFirst of all, we assume certain shares of the different types of

solar PV and wind power technologies. The next step is to assume (based on a range of sources) the amount of materials that is

be used for concentrated PV (where sunrays are first focussed on the cells). Other options (not market ready) for thin film PV are so-called dye-sensitized solar cells (DSC) and organic solar cells.

The advantage of thin film compared to crystalline PV is a lower material demand (and consequently

less weight), flexibility of the material and some types of thin film have achieved higher efficiencies (e.g. CI(G)S and GaAs).

Apart from the material demand for the solar cells, copper is used in the invertors, transformers and cabling (for all types of PV).

Windturbine TechnologyWind power mainly requires steel,

copper, carbon and glass-fibre. Currently, most turbines contain a gearbox, but so-called direct drive turbines are commercially available

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figure 1: deployment of solar PV & Wind Power(Iea BLUe map scenario Until 2050)

Source: IEA

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share of direct drive turbines: We assume that all offshore wind power is equipped with direct drive turbines with a neodymium magnet.

For the materials use (per MW) for wind and solar PV we use estimates from the studies of Fraunhofer5, Öko-Institut6 and ECn.7

For offshore wind power, we included the copper demand for transport cabling: We assume that the average wind farm is located 30 km from an onshore connection. Material demand for an average High Voltage Direct Current (HVDC) cable was estimated with specifications from a DLR study.8

For the materials used in the actual solar cells9 an increase in material efficiency was taken into account. We assumed a so-called progress ratio of 0.85: This means that a doubling in installed capacity results in a 15% decrease in material demand per MW. For cabling and neodymium magnets, we did not include a progress ratio: A conservative estimation was used for the neodymium content, and material efficiency opportunities for cabling are limited (at least for the conductive parts in the cables).

We should emphasize that the actual future solar PV and wind markets may look very different from our assumptions. Winning technologies (as yet unknown) will of course be partly determined by material availability. The quantification in this article is thus not an exact prediction of how the material demand will develop if the BLUE Map Scenario is realised, but is merely an exploration of the (im)possibilities in terms of material supply.

Results: material demand in BLUe map scenario

In order to get a direct grasp of the material demand for solar PV and wind, we present the demand as a share of the current annual production of these materials.

An overview of the results is presented in Table 2 which shows the average demand in the periods 2009-2020 (blue), 2020 - 2030 (red) and 2030-2040 (green).

For elements in thin film solar cells, we quantified the demand for two cases: (i) where current material demand per MW remains constant, and (ii) where material efficiency increases according to a progress ratio (see previous section). The latter case is indicated with ‘Learning’ in Table 2. This shows that, in cases where solar PV and wind is deployed according to our assumptions, material demand relative to current production will be very high. neodymium, gallium, germanium, tellurium, indium approach or even exceed current production (depending on material efficiency improvements). Copper and silver demand for solar PV and wind

actually needed per unit of capacity (e.g. tonne of material per MW).solar PV breakdown: By 2050, we assume that 40% of the total installed capacity of solar PV will be thin film PV, where CdTe, a-Si, CI(G)S and GaAs all have an equal share.

Table 2: critical demand; solar & Wind Power(Iea BLUe map scenario, Until 2040)

2009-2020 2020-2030 2030-2040

arsenic 0% 1% 1%

Arsenic - Learning 0.05% 0.2% 0.3%

cadmium 1% 3% 6%

Cadmium - Learning 0% 1% 1%

gallium 55% 280% 600%

Gallium - Learning 25% 90% 150%

Germanium 30% 160% 330%

Germanium - Learning 15% 50% 80%

Indium 9% 50% 100%

Indium - Learning 4% 15% 25%

selenium 1% 6% 14%

Selenium - Learning 1% 2% 3%

silver 5% 15% 20%

Tellurium 15% 80% 170%

Tellurium - Learning 7% 25% 40%

copper 2% 4% 6%

neodymium 60% 50% 90% Source: Ecofys

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might be 6%, respectively 20% of the current production. Material efficiency improvements via learning result in decreases in material demand: Up to four times less material is needed in cases where there is learning. But, as Table 2 shows, demand still approaches/exceeds current production for gallium and germanium.

The consequencesA number of important conclusions can be drawn from the

quantification above: Firstly, large-scale deployment of CI(G)S, CdTe and GaAs thin film technologies, will be very difficult. This is the case even if material efficiency improves steadily towards 2050. Secondly, offshore wind cannot be fully equipped with neodymium-containing magnets, which implies that some types of direct drive turbines cannot be deployed in large quantities.

Is the BLUe map a Possibility?The quantification above is performed using a range of

assumptions, and under other conditions the BLUE Map Scenario might be more feasible. For solar PV there is an alternative: Silicon based PV. Silicon is an abundant mineral and current production capacity (to make solar grade silicon) has been increasing very fast: The current and planned production capacity is almost sufficient to achieve the 2020 target in the BLUE Map Scenario.

A disadvantage of silicon is the relatively high energy investment necessary to produce solar grade silicon. Iron pyrite (FeS2) would be an attractive alternative material, in terms of availability and energy costs, for solar cells.10 CI(G)S, CdTe and GaAs based thin film, might find their niche markets (for applications where weight and size should be minimised), but will not reach a large market share.

To reduce silver and copper demand, these materials can in many cases be replaced by aluminium.

The current generation of wind turbines, generally does not contain neodymium, so there is an alternative already available.

Unfortunately, the current generation of turbines is not optimal in terms of weight and complexity. R&D is thus very important to find alternative designs, in order to reduce weights and increase robustness.

Summarizing, the BLUE Map can still be achieved, but only if material use is critically considered in R&D and investments decisions in production capacity.

Preventing BottlenecksIt’s not only about performance; it’s also about material use: The performance (weight, size, efficiency) should not be the only factor to take into account when investing in a technology. The materials will also determine the future market share. First of all, the selection of the materials is important: abundantly available materials should be preferred. Secondly, material efficiency is of key importance, although it is no golden bullet. Currently

the semi-conductor industry is already investing in research to find alternatives for rare metals and increase material efficiency, especially platinum.

Eventually, price increases will trigger reductions in rare metal consumption. This trigger is however not present when a technology is still in the R&D phase. If R&D financing in clean technologies is targeted at large-scale deployment, material use and material efficiency should thus be taken into account in advance (i.e. before producers face price increases and supply constraints).Recycling has a future: Recycling has a great future. Production increase by increasing mining activities is not always attractive: Some minerals are produced as a by-product of copper or zinc extraction, and will thus be dependent on the production of these bulk metals. Additionally, as the average mineral concentration generally decreases when production increases, production costs, negative environmental (and sometimes social) impacts as well as energy consumption will increase.

For some metals (for example gallium) the concentration are reported to be higher in waste electronics (e-waste) than in actual ores. Even if the materials discussed here are not applied for solar PV or wind power, more and more applications require rare metals. Recycling will increase the (security of) supply, so investments in optimising recycling, in terms of recovery rates and energy use are expected to pay off, both economically and environmentally.

assessing future energy supply

In our analysis, we focussed on wind power and solar PV. These technologies were not compared with, for example, nuclear or coal power. These conventional technologies also require raw materials (think of uranium and coal). To compare the different energy technologies, apart from GHG emissions, resource consumption (e.g. mineral, fuel and

the BLUE Map can still be achieved, but only if material use is critically considered in R&D and

investments decisions in production capacity

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water) should also be considered.11 One good indicator would be the energy investment that is needed to produce the resources for the different technologies. In order to reduce negative environmental and social impacts of future technologies, such an analysis will be a useful tool in assessments of our future energy supply.

We live in a world were more energy is used, and where more people use more and more technologies, with sometimes short lifetimes (think of cell phones, tablets, computers). Meanwhile, low-carbon energy production based on for example renewable technologies is of key importance. Unfortunately, some energy technologies require materials that are produced in relatively low quantities and also face demand increase from other applications. In order to prevent supply chain bottlenecks, high costs and negative environmental impacts, a critical assessment of the materials used in technologies (in this case energy) is needed.

We should focus on technologies that make use of abundant materials, increase material efficiency and improve recycling. Only if we start doing this, will large-scale deployment of renewable energy be possible. •

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Pieter van Breevoort & Rolf de Vos work for Ecofys, a research and consultancy company specialising in renewable energy,

energy savings and climate policies.E: p.vanbreevoort@ecofys.com

www.ecofys.com

footnotes & References1. Exact tellurium production is unknown, our estimation is based on the national

data that were available. This figure should be interpreted as an order of magnitude.

2. See for example: European Commission, 2010. Critical raw materials for the EU - Report of the Ad-hoc Working Group on defining critical raw materials. European Commission (EC)Enterprise and Industry

3. See Epia, 2011: Global Market Outlook for Photovoltaics Until 2014. Available at: www.epia.org

4. International Energy Agency, 2010. Energy Technology Perspectives5. Fraunhofer ISI/IZT, 2009. Rohstoffe für Zukunftstechnologien. Available at:

http://publica.fraunhofer.de/documents/n-91007.html6. Öko-Institut, 2011. Study on Rare Earths and Their Recycling. Available at:

www.oeko.de/oekodoc/1112/2011-003-en.pdf7. ECn, 2007. Environmental Life Cycle Inventory of Crystalline Silicon

Photovoltaic System Production - Status 2005/2006. Available at: www.ecn.nl/publicaties/default.aspx?au=446498. DLR, 2006. Trans-CSP Trans Mediterranean Interconnection for Concentrating

Solar Power. Available at: www.dlr.de/tt/desktopdefault.aspx/tabid-2885/4422_read-6588/9. i.e. arsenic, cadmium, indium, gallium, germanium, selenium and tellurium10. Wadia, C., A. P. Alivisatos, and D. M. Kammen, 2009. Materials Availability

Expands the Opportunity for Large-Scale Photovoltaic’s Deployment, Environmental Science and Technology 43: 2072-2077.

11. In order to analyse their sustainability, biofuels are already subject to so-called Life Cycle Analyses.