Which is a better deal: an established, off-the-shelf type of solar panel or a cutting-edge type that delivers more power for a given area but costs more? It turns out that’s far from a simple question, but a team of researchers at MIT and elsewhere has come up with a way to figure out the best option for a given location and type of installation. The bottom line is that for household-scale rooftop systems in relatively dry locations, the more efficient but more costly panels would be better, but for grid-scale installations or for those in wetter climates, the established, less efficient but cheaper panels are better. The costs of solar cells continue to plummet, while the costs of installation and the associated equipment remain relatively constant. So, figuring out the tradeoffs involved in planning a new installation has gotten more complicated. But the new study provides a clear way to estimate the best technology for a given project, the authors say. The findings are reported today in the journal Nature Energy, in a paper by MIT graduate student Sarah Sofia, associate professor of mechanical engineering Tonio Buonassisi, research scientist I. Marius Peters, and three others at MIT and at First Solar and Siva Power, solar companies in California....

The dramatic drop in the cost of solar photovoltaic (PV) modules, which has fallen by 99 percent over the last four decades, is often touted as a major success story for renewable energy technology. But one question has never been fully addressed: What exactly accounts for that stunning drop? A new analysis by MIT researchers has pinpointed what caused the savings, including the policies and technology changes that mattered most. For example, they found that government policy to help grow markets around the world played a critical role in reducing this technology’s costs. At the device level, the dominant factor was an increase in “conversion efficiency,” or the amount of power generated from a given amount of sunlight. The insights can help to inform future policies and evaluate whether similar improvements can be achieved in other technologies. The findings are being reported today in the journal Energy Policy, in a paper by MIT Associate Professor Jessika Trancik, postdoc Goksin Kavlak, and research scientist James McNerney....

In any conventional silicon-based solar cell, there is an absolute limit on overall efficiency, based partly on the fact that each photon of light can only knock loose a single electron, even if that photon carried twice the energy needed to do so. But now, researchers have demonstrated a method for getting high-energy photons striking silicon to kick out two electrons instead of one, opening the door for a new kind of solar cell with greater efficiency than was thought possible. While conventional silicon cells have an absolute theoretical maximum efficiency of about 29.1 percent conversion of solar energy, the new approach, developed over the last several years by researchers at MIT and elsewhere, could bust through that limit, potentially adding several percentage points to that maximum output. The results are described today in the journal Nature, in a paper by graduate student Markus Einzinger, professor of chemistry Moungi Bawendi, professor of electrical engineering and computer science Marc Baldo, and eight others at MIT and at Princeton University....

In the transition to a decarbonized electric power system, variable renewable energy (VRE) resources such as wind and solar photovoltaics play a vital role due to their availability, scalability, and affordability. However, the degree to which VRE resources can be successfully deployed to decarbonize the electric power system hinges on the future availability and cost of energy storage technologies. In a paper recently published in Applied Energy, researchers from MIT and Princeton University examine battery storage to determine the key drivers that impact its economic value, how that value might change with increasing deployment over time, and the implications for the long-term cost-effectiveness of storage. “Battery storage helps make better use of electricity system assets, including wind and solar farms, natural gas power plants, and transmission lines, and that can defer or eliminate unnecessary investment in these capital-intensive assets,” says Dharik Mallapragada, the paper’s lead author. “Our paper demonstrates that this ‘capacity deferral,’ or substitution of batteries for generation or transmission capacity, is the primary source of storage value.”...