Photovoltaics and solar power
MIT’s approach to sustainable clean energy
Tonio Buonassisi, the primary investigator at MIT’s Photovoltaics Lab, recently took a trip to the Folgefonna National Park in Norway. There, he hiked across nearly 200 square kilometers of glaciers. Under the crunch of snow with each step he took, he could hear the water rushing below him — more water than was normal for the ebbs and flows of a glacier’s natural lifetime — a constant reminder that his time to act was running out.
According to the United States Energy Information Administration, only 1.3 percent of the country’s electricity comes from solar technology compared to the 63 percent generated by fossil fuels. At MIT, the Photovoltaics Lab (PVLab) focuses on materials and techniques to make solar energy more ubiquitous. Since its inception in 2007, the mission of the PVLab has been to develop solar energy technologies under three main canopies: commercial solar technology, which consists of studying impurities in silicon solar cells; next generation approaches, which include using artificial intelligence to analyze the impurities within the cell; and the study of photovoltaic (PV) systems.
To be viable, photovoltaic systems must be predictable, so that the system minimizes uncertainty around day-to-day fluctuations in the climate and optimizes the technology. As a result, the product is small, power-efficient, and cost-efficient. To be implemented on a wide scale, PV systems must also be persistent, providing a long-lasting solution to energy effiency issues. To these ends, the individual projects in PVLab range from making “artificial leaves” that mimic photosynthesis to combining machine learning, automation, and high-performance computing in order to predict the behavior of the systems.
Marius Peters, who leads the Systems on Silicon research group, dedicates much of his time to the predictability of PV systems. Recently, he completed a project with Amos Winter, the director of MIT’s Global Engineering and Research (GEAR) Lab. Peters implemented solar cells that power desalination systems to produce potable water out of ground water in rural areas. These systems are comprised of two streams of water running through a membrane with a potential difference to strip the water of unwanted ions. By timing the process in a certain way, the team was able to reduce the number of batteries used as well as the number of panels that powered the system. One of the main roadblocks of the project was the cost. “Making [projects] cheap is really essential for getting them adopted in the areas where they really need it,” Peters said. His team eventually reduced the cost of powering the system by 40 percent.
However, the work is not over — these systems must also be reliable and predictable. Much of Peters’s work now focuses on the behavior of solar cells in different outdoor conditions. Although silicon is the most widely used material to make solar cells, Peters and his group have studied cadmium telluride as an alternative. Cadmium telluride is less sensitive to changes in temperature and humidity, thus resulting in a more stable production of energy over time compared to silicon.
Recent innovations like these instill hope into Peters. In his eyes, renewable energy is at its renaissance. “Even within the United States, even under the current administration, and even under certain arguments put up against renewables, solar and wind installations in 2018 have counted for the vast majority of new installed electricity sources,” he noted. He encouraged students to face the challenges that renewable energy poses, both technical and political, in order to make sustainable energy cheaper and more reliable. “It’s not just an idea,” Buonassisi said, speaking to the importance of sustainable energy. “It’s something very real.”
The potential obstacles to sustainable energy may not be as concrete as the technology required to implement it. In particular, Buonassisi feels there are habits accepted in academia that can hamper productivity. “There are a number of unhealthy, culturally accepted things in academia and inefficient R&D is one of them. We’re trying to solve climate change issues, we don’t have time!” Buonassisi worried. “There are many unhealthy habits in academia, from working long hours — but a lot of that is procrastination and waste — to accepting all of the horrific things that happened before the #MeToo movement dragged it all out of the closet.”
For Buonassisi, the solution is a healthy dose of self-reflection. “It’s very easy to point a microscope away from us toward a material and [analyze] it, but focusing the microscope back on ourselves and asking ‘How are we conducting research? Can it be done faster?’” he wondered. “It’s almost like a trigger for many academics.” According to Buonassisi, there is an accepted form of mimicry in many areas of academia — newcomers to research learn that to get published, they must follow certain norms. As a result, they model their own work around methods of research that have already been established. “We don’t challenge the way we do R&D,” Buonassisi said.
Peters sees the state of research in a hopeful light. He emphasizes that scientists need to collaborate to find sufficient solutions to complex problems. “The role that we have as researchers in this field has increased. There is currently one of the biggest transitions in the energy infrastructure on the planet on its way.”
“It’s going to go a lot further, and it needs researchers — it needs people to be educated and trained for this,” he added.