The solar power industry is growing rapidly. With new solar technology advancements, renewable energy is becoming less expensive then coal-powered electricity. Lazard’s annual Levelized Cost of Energy (LCOE) analysis reports solar photovoltaic (PV) and wind costs have dropped an extraordinary 88% and 69% since 2009, respectively. Meanwhile, coal and nuclear costs have decreased by 9% and increased by 23%, respectively. Even without accounting for current subsidies, renewable energy costs can be considerably lower than the marginal cost of conventional energy technologies. In addition, the Solar Investment Tax Credit (ITC) has provided industry stability and growth since its initial passage in 2006. In the last decade, solar has experienced an average annual growth rate of 50%.

How Many Solar Panels Do We Need?

Starting with some conservative assumptions from a 2013 National Renewable Energy Labs (NREL) report, we know that it takes, on average, 3.4 acres of solar panels to generate a gigawatt hour of electricity over a year. Given the U.S. consumes about 4 petawatts of electricity per year, we’d need about 13,600,000 acres or 21,250 square miles of solar panels to meet the total electricity requirements of the United States for a year.

This may seem like an impractically large amount of land, but not when you put it in perspective. In comparison, 40,223 square miles is the size of the land leased by the oil and gas industry (according to the US Bureau of Land Management). The U.S. has 3,797,000 square miles of land. Only about half a percent of that would be needed to provide enough solar energy to power the country.

In determining a very rough estimate to the number of solar panels for 13,600,000 acres, there are many considerations. Depending on different environmental and construction factors, and “semantics”, the wide-ranging answer is 3,225 panels covering approximately 5 acres1. So, hypothetically, there is a potential of 8,772,000,000 solar panels that are eventually installed to meet the electricity demand of the U.S.

With a lifetime of about 30 years on average, crystaline silicon solar panels don’t become obsolete very quickly. However, given the rapid expansion of the solar industry, the number of solar panels needing to be recycled or disposed of in the coming years will continue to increase. More and more panels will reach the end of their life each year, and even now, old solar panels are beginning to become a problem. In fact, if recycling processes are not put in place, there could be 60 million tons of PV panels waste lying in landfills by the year 2050; since all PV cells contain a certain amount of toxic substances, that would truly become a not-so-sustainable way of sourcing energy.

What Can Recycling Solar Panels Offer?

Recycling can offer two benefits. Besides environmental protection, recycling solar panels will be economically impactful as well. Some of the rare elements in photovoltaic (PV) cells like gallium and indium are being depleted from the environment over time. If we were able to recover those elements, we can conserve the limited amount available on earth and continue to use them for solar panels and other products. Furthermore, a 2016 study by the International Renewable Agency (IRENA) estimated that $15 billion could be recovered from recycling solar modules by the year 2050.

So, What’s the Problem?

The difficulty with recycling solar panels isn’t that the materials they are made from are hard to recycle; rather, it’s that they are constructed from many parts all used together in one product. Separating those materials and recycling them each in a unique way is a complex and potentially expensive process. For that reason, it is necessary that design teams and recycling units collaborate closely so that the ability to recycle is insured by mindful eco-designs.

There are two main types of solar panels requiring different recycling approaches. Both types—silicon-based and thin-film based—can be recycled using distinct industrial processes. Recycling solar panels is a relatively complex task because they contain many different types of materials. Panels contain metals, such as lead, copper, gallium and cadmium; an aluminum frame; silicon solar cells; and synthetic material that encapsulates the silicon. The various materials must be separated to be properly recycled. Undamaged solar cells, for example, can often be recovered and reused in new products.

What Can Solar Panel Recycling Look Like?

From a regulatory aspect, PV panel waste still falls under the general waste classification. A sole exception exists at EU-level, where PV panels are defined as e-waste in the Waste Electrical and Electronic Equipment (WEEE) Directive. The PV panel waste management is thus regulated by this directive, additionally to other legal frameworks.

In Europe, the solar cells manufacturers are bound by law to fulfill specific legal requirements and recycling standards in order to make sure that solar panels do not become a burden to the environment. That is when technologies to recycle solar panels started emerging. Photovoltaic producers collaborated with governmental institutions and have come up with a few ways to tackle solar waste.

PV Cycle, a European solar panel recycling association, developed a mechanical and thermal treatment process in 2017 that achieves a 96 percent recovery rate for silicon-based photovoltaic panels. The remaining 4 percent is utilized in an energy recovery process, using a waste-to-energy technology. Non-silicon-based solar panels can have a recovery rate of up to 98 percent.

What's the Happy Ending?

With development of PV recycling, not only will more green job opportunities be created, but also recycling could provide approximately $15 billion in recoverable value by 2050. This influx will make it possible to produce 2 billion new panels without the need to invest in raw materials. This means that there will be the capacity of producing around 630 GW of energy just from reusing previously used materials.

While solar panel recycling isn’t widely available in the U.S. for all of the components, there’s still a little time before the number of panels needing to be recycled gets too high. Groups like Solar Energy Industries Association (SEIA) and Recycle PV are doing important groundwork for the industry, but there’s more to do in years to come.

1 Chris Thompson, Off grid solar Industrial Electrical Engineering & Solar Energy, University of Arkansas

Answered July 24, 2018; https://www.quora.com/How-many-310-watt-solar-panels-are-needed-on-5-acres-to-get-a-MW.