By: Hannah Pell
I recently relocated from the bustling Washington, D.C. metro area back to my south-central Pennsylvania hometown. My new space is in a quiet, wooded area; outside my back window I see an expanse full of trees (“Pennsylvania” actually means “Penn’s Woods”) — and a small solar farm is nestled in between them. As the sun shines onto the panels, I can’t help but wonder: how much of the electricity powering my laptop is sourced from the sun? What’s the science behind it all, and where does solar fit within Pennsylvania’s diverse energy portfolio?
Physics of solar cells and their efficiency
The fundamental physics principle underlying solar cell technology is the photoelectric effect. Photons (light particles) can be thought of as discrete packets of energy. The energy of the electrons emitted when some form of radiation (such as light) strikes a material directly depends on the frequency of that incident radiation. Solar cells are designed using semiconducting material to harness that energy and convert it to usable electricity. Individual solar cells are joined together to form solar panels, and panels are arranged in arrays (seen above) in order to increase the output voltage.
Efficiency is a big concern in solar cell technology with regard to both the location of the solar panels and the materials used to construct them. First of all, sunlight isn’t always or equally available everywhere; Pennsylvania only receives approximately 60 – 65% as much sunlight as regions in the southwestern United States. This makes the case for additional large solar projects in Pennsylvania a bit more challenging to argue (as compared to somewhere like California, home to several of the country’s largest solar farms), though certainly not impossible.
The efficiency of solar cells is also limited by the semiconducting materials used and energy storage capacity. Lithium ion batteries are usually described as the best option for solar panel systems, and the technology may be on the verge of a turning point, however, they’re generally more expensive than other types of batteries. Additionally, materials science researchers at the National Renewable Energy Laboratory are focused on using perovskites to increase the efficiency, stability, and overall performance of solar cells. With combined improvements to both storage and materials capabilities, the science behind solar seems to suggest that the future truly is bright (thankfully!).
Solar in Pennsylvania
The history of modern energy production and innovation in the United States is very much a Pennsylvania story — between bituminous coal mining, the first commercial nuclear power plant in Shippingport, natural gas from the Marcellus Shale, and increasing deployment of varied renewables such as wind, hydropower, and solar — the Commonwealth is and has always been an impactful region shaping our collective energy future. Pennsylvania is indeed a microcosm of both the opportunities and challenges that our diverse energy demands require.
The Alternative Energy Portfolio Standards Act (AEPS) of 2004 is an important piece of Pennsylvania’s energy legislation; it required that a certain percentage of electricity purchased in Pennsylvania’s wholesale energy market is sourced specifically from renewables. AEPS mandated that at least .5% would specifically come from solar power before this year. Today, renewables remain a categorically small portion of Pennsylvania’s energy pie, only accounting for 5.1% of electricity production at the end of 2020 (the U.S. average is 22.5%, according to the Energy Information Association). Of this slice, solar provided .31% of Pennsylvania’s in-state electricity, which is very low compared to neighboring New York (2.32%).
All things considered, what could be the best path forward for solar in Pennsylvania? The “Finding Pennsylvania’s Solar Future” project aims to identify strategies to increase solar generation to 10 percent of in-state consumption by 2030. One effective way to do that may be to focus on smaller solar systems (such as residential rooftops), which is also predicted to create more jobs. Residential solar panels are “grid-tied,” so if one house produces more solar energy than they consume, the excess will be fed back into the grid and they receive credits for it. Given Pennsylvania’s geography, this could be a more viable option for the future of solar.
|Image Credit: Pennsylvania’s Solar Future Plan booklet (pg. 5)
I feel quite lucky to have a solar farm in my new backyard. So much of our energy infrastructure is hidden in plain sight that it’s easy to take for granted. The solar panels outside were enough to make me stop and think about where my electricity is coming from, and why that’s so important. As we navigate our transition away from over-reliance on fossil fuels toward cleaner energy sources, it’s clear that solar has become an increasingly important piece of the puzzle. The question that remains is, how can we best utilize it here at home?