Getting to an all U.S. renewable grid by 2050 is a critical component of achieving the world’s climate goals. Solar energy will be a crucial contributor to that effort. But, there is a “dark side” to solar power and it is increasingly in the news based on a variety of theoretical calculations. The dark side includes the need to trash millions of used, outdated solar panels in landfills. It includes the problem of intermittency, which occurs because solar often produces the most energy when demand is low. And it includes covering tens of thousands of acres of potentially usable land with solar collectors — making the land unusable for housing or agriculture. Let’s look at each of these challenges to the future of solar power and explore some  solutions that shed light on the darkness.


Solar Panels and Batteries Will Clog Landfills

The International Renewable Energy Agency (IRENA) projects that “large amounts of annual (solar panel) waste are anticipated by the early 2030s” and could reach 78 million tons by the year 2050. It has been projected that with increased efficiency and lower cost panels, many people will replace their current panels years before the expected 30 years of useful service. Theoretically early replacement could result in 50 times more waste in four years than IRENA projects. That could result in about 315,000 metric tonnes of solar panel waste by 2050. 

The Solution: First of all, most people will not likely rush to replace solar panels before 30 years, when they are still operating at better than 70% of their original production capability. Long term, life cycle assessment and recycling must be implemented for solar panels along with all other disposed materials in our economy. The Korea Institute of Energy Research has made great progress on this front. They have developed techniques for recycling 100% of the glass from discarded solar panels and for turning 80% of the other materials into high efficiency solar cells. They are now licensing this process for commercial use by a solar panel manufacturer. In the EU, recycling responsibility is assigned to manufacturers based on their current market share. Producer recycling fees are built into the price of solar panels. It is a realistic hope that improved recycling techniques and strategies will make recycling profitable — thus avoiding the need for government regulation and fees. Life cycle assessment of batteries, which will be crucial to the success of using solar to meet our climate goals, shows that lithium ion batteries have a significantly lower carbon impact than fossil fuels — and it is coming down. Life cycle assessment, recycling, and creating a “circular economy” for batteries and solar panels will greatly reduce the need for large-scale mining operations while reducing or eliminating the need to dump them in landfills. 


Intermittency Will Reduce the Value and Growth of Solar

Because solar produces energy when the sun shines, it currently contributes little or no energy to the grid during peak hours of energy use in the early morning and evening. This results in the need for natural gas fired power plants to fill the gap and may reduce the return on investment on solar farms because they may produce a glut of electricity when it is needed less, resulting in lower pricing. This may stall the growth of the very solar power plants we need to reach the world’s climate goals. 

The Solution: Batteries for homes, businesses, and utilities are already becoming more cost-effective for meeting short-term peak demand. And a great deal of work is being done to economically produce green hydrogen from excess solar energy to generate electricity during peak demand. The combination of a smart grid, smart homes and buildings, smart appliances, and peak-hour pricing will encourage electric vehicles to be charged, clothes to be laundered, and water to be heated during off-peak hours when energy is abundant. Electric vehicles are being developed with batteries that can function as home and grid storage, allowing for increased battery storage at no or little added cost. 


Solar Farms Displace Agriculture and Housing

It has been estimated that the average solar farm can produce 357,000 kWh per acre. This estimate will vary depending on factors such as the latitude, cloud cover, and snow cover of the area, along with the power of the collectors themselves and the distance from end use. The U.S. currently uses close to 4,000 billion kWh of electricity per year. To obtain 100% of this electricity from solar would result in covering more than 11 million acres or 17,000 square miles with solar panels — an area larger than many of our smaller states. 

The Solution: It’s not necessary to locate all solar facilities on land, particularly land that has better uses. There are 8 billion square meters of rooftops in the U.S. suitable for solar — capable of producing 1,400 terawatts of electricity — enough for 40% of U.S. current needs for electricity. There are another 9 billion square meters of parking lots that may be suitable for shading with solar collectors to produce another 40% of our electricity needs. And certain agricultural crops grow well with partial shade provided by solar collectors. Rooftop solar produces energy closer to where it is used, creating less need for long, expensive transmission lines that waste energy. The efficiency of solar panels is growing, so more electricity is being produced in a smaller area. And contributions to renewable energy from hydro and off-shore wind will further reduce the need for building out solar. Using these approaches, land use will not be a problem. 


Going All Electric Will Double the Land Needed for Solar

The above estimates do not take into account the “electrify now” movement and the widespread adoption of electric vehicles, including the car, truck, bus, and public transportation fleets. In addition, green hydrogen will be produced from renewable electricity. According to a Princeton study, if we electrify everything, it is likely our electricity consumption could more than double before 2050. This would require a huge expansion of solar that could take huge swaths of land out of use for housing and agriculture. 

The Solution: If all new buildings and homes are built to zero energy or passive house standards, and existing ones get well on the path to zero energy, the electric demand from all electric homes and buildings will be drastically reduced. Rooftop solar collectors will reduce the burden on utility power. New electric vehicles may have solar collectors on their skin, too. And efficiency gains of heat pump HVAC and water heating systems will complement the gains in solar cell efficiency.


Renewable Energy Powered Future Is On the Way

While there are several serious challenges on the road to a fully renewable energy system, there is a wide array of potential solutions. Thanks to thousands of small technical innovations, the theoretical challenges of shifting to a largely solar-based, all-renewable energy-powered economy are being solved. We can all help speed up the process by creating demand for currently available products that will get us there  —  solar panels, battery storage, heat pumps, “smart” grid-aware appliances, and electric vehicles, as well as all electric zero energy or passive house homes and buildings. As demand grows, innovations will increase and prices will fall — leading to universal adoption of zero energy lifestyles. All we need to do is shine our light on the challenges.