l'Actualité du Solaire

Contents :

The financial cost

The environmental cost

Lead

Metals in thin films

The text :

The COP25 is taking place in Madrid at the moment. It is the place where concerns about the climate, the disappearance of species and the need to reduce the use of hydrocarbons are exchanged. They are talking about pollution of the seas, land and space. Nothing escapes the catastrophism of the future, the disruption that man has brought with his expansion.

Curiously, photovoltaic and wind power are considered as the alternative to carbon energies, as the future towards which we must strive, as the solution to greenhouse gases. In accordance with this objective, all wills should be directed towards the multiplication of solar or wind power plants, without considering the financial cost, but also the environmental cost.

The financial cost

It is hidden in the price mechanism of a power plant: generators based on renewable energies have to be paid for when they are created, only to have almost free energy for twenty to thirty years afterwards. But this cost is high. On the one hand, the capital to be immobilised is considerable; on the other hand, as soon as the plant is built, it is immediately devalued. This is the consequence of the falling price of the panels or components, but also of the increasing efficiency of the panels. The devaluation of the plants occurs as soon as the constructions are only a few quarters old. This is the consequence of technological progress, which provides further improvements in their efficiency. The loss in value of all plants already in operation will continue (will it increase?). This loss in value is considerable.

The phenomenon is hidden by the mechanism of purchase offers proposed by governments or by private purchase contracts over a period of ten years: what will happen next for the owner of the plant? Will he have to sell his energy at half price, excluding the depreciation of his plant?

If investors were aware of this, they would wait until the efficiency of the installations has stabilised before continuing to invest, as the loss in value is too great. It is said that the cost of panels has fallen by 80% in a decade when panels were half the cost of a plant. This means that the "lucky" owner of a power plant has seen the value of his assets decrease by 40% in ten years, regardless of the ageing of the facility, which further reduces his assets! You have to be a candidate for financial suicide to invest in power plants that are doomed to depreciate so quickly! Or believe that holding an energy production portfolio will always have value. Either way, the financial loss is considerable as soon as a power plant is commissioned!

The environmental cost

The environmental cost is for the moment ignored, probably due to ignorance, more likely because the panels are essentially producing energy and the period of their replacement will be from 2030, and more likely from 2040. Between now and then, the financial and environmental constraints of construction, as well as the dangers posed by the panels, will be forgotten until the period when the panels will be destroyed, which will provoke a brutal awakening of public opinion.

The construction of a crystalline silicon panel requires a frame, glass, encapsulant, back sheet, junction box, EVA. These are the most visible products in the composition of a panel. It also requires different materials such as lead and silver for the metallisation pastes between the cells, but also aluminium, silicon, copper, iron, zinc, ... Aluminium and silicon represent the largest share in terms of weight, followed by copper, iron and zinc. "The maximum concentration of metal of concern was observed at 4.02 milligrams per PV panel, or 0.7% in a typical crystalline silicon panel," wrote the Indian research team that carried out the research.

.

Lead

A crystalline silicon panel contains on average 12 grams of lead. It acts as a junction between the cells, in conjunction with silver, which is a good electrical conductor. Although the amount of lead is small and well protected on the panel, it does not come into contact with water because then it is highly toxic, which has been known since ancient times. The nuisance power of lead comes into play when the panel is destroyed. If it is not recycled, its particles go into the water to contaminate it, with repercussions on human life. Placing the panel in a landfill is the simplest way to get rid of it because recycling is expensive. It is to be expected that end-of-life panels in China, India or other countries around the world will be dumped in landfills. If the panels are recycled as they should be in Europe, they will be shredded to allow sorting by component. It will be difficult to collect all the lead contained in the panel. Lead particles will be found in glass and in products made from recycled materials such as films, coatings, filters, ashes, etc. We are not done hunting for lead.

Producing lead-free panels would increase the cost of a panel. Solarworld had developed a lead-free panel, only it was 0.5% more expensive. This is not much, but a panel with a 20% efficiency costs 0.20%. € / W with lead solder and 0,21 € / W unleaded. The difference seems insignificant, but if the manufacturer produces 1 gigawatt per year, the cost difference amounts to €1 million. In an industry where every cent is important. This condemns manufacturers who are too expensive. Either there is general global legislation to ban lead, or this metal will continue to be used in the production of panels and then will end up in the industrial chain, and increasingly so. The search for lead in our environment and, more prosaically, on our plates, is not over. Cf Can lead be removed from PV panels?

.

Metals in thin films

On the other hand, CIGS and CdTe thin films use much more dangerous metals such as tellurium, cadmium, gallium, indium, ... Gallium would have lethal properties for the cells. It would be carcinogenic as a compound. However, it makes up 2.4% of the total.

In CdTe panels, copper, tellurium and cadmium have the highest concentration of metals. Cadmium and copper have been shown to be highly toxic to aquatic organisms. Cadmium is a known carcinogen with a maximum contaminant level of 0.003 milligrams per litre of drinking water. However, it would appear that the proportion of cadmium in a panel is not well known, with a rate of between 0.001% and 19.8% by weight of metals, including 0.0001 to 5.02% lead. Cf Landfilled solar panels: chemical composition and dangerousness

"The presence of these heavy metals (cadmium, tellurium, indium, gallium) in the composition of thin layers would represent a major threat to health and the environment if they are not disposed of correctly. Above all, there is a lack of data on the initial concentrations of metals. The ability of metals to be removed from thin films is not known. dissolve in solvent or water (or leach) when burying these metals. All this represents gaps in our knowledge," conclude the Indian researchers.

Thus, while photovoltaics (along with wind power) represent the hope of a generation to replace fossil fuels, the world is preparing for a great financial and environmental disillusionment.