From: Hannah Pell

I recently moved back to my hometown in southern Pennsylvania from the busy Washington, DC subway area. My new room is in a quiet, wooded area; In front of my back window I see an area full of trees (“Pennsylvania” actually means “Penn’s Woods”) – and in between there is a small solar park. As the sun shines on the panels, I ask myself: How much electricity that powers my laptop comes from the sun? What is the science behind it, and where does solar fit into Pennsylvania’s diverse energy portfolio?

Physics of solar cells and their efficiency

The basic physical principle of solar cell technology is the photoelectric effect. Photons (light particles) can be viewed as discrete packets of energy. The energy of the electrons emitted when some form of radiation (such as light) hits a material is directly related to the frequency of that incident radiation. Solar cells are made of semiconducting material in order to use this energy and convert it into usable electricity. Individual solar cells are put together to form solar modules, and the modules are arranged in arrays (see above) in order to increase the output voltage.

Efficiency is a major concern in solar cell technology, both in terms of the location of the solar modules and the materials from which they are made. First, sunlight is not always or equally available everywhere. Pennsylvania only receives about 60-65% as much sunlight as regions in the southwestern United States. This makes it a little harder to argue about additional large solar projects in Pennsylvania (compared to California, which is home to several of the largest solar parks in the country), although it is certainly not impossible.

The efficiency of solar cells is also limited by the semiconductor materials used and the 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 tipping point. However, they are generally more expensive than other types of batteries. In addition, materials science researchers at the National Renewable Energy Laboratory are focusing on the use of perovskites to increase the efficiency, stability, and overall performance of solar cells. With combined improvements in storage and material capacities, the science behind solar seems to be suggesting that the future is really promising (thank goodness!).

According to the Solar Energy Industries Association, solar has seen an average annual growth rate of 49% over the past decade, and (perhaps more importantly) the cost of installing solar has decreased by more than 70% over that period. What could these trends mean about the role of solar energy in Pennsylvania’s diverse energy portfolio?

Solar in Pennsylvania

The story of modern energy generation and innovation in the US is a story from Pennsylvania – between the mining of hard coal, the first commercial nuclear power plant in Shippingport, natural gas from the Marcellus shale and the increasing use of various renewable energies such as wind, hydropower and solar – the Commonwealth is and always has been an important region shaping our collective energy future. Pennsylvania is indeed a microcosm of the opportunities and challenges our diverse energy demands require.

The Alternative Energy Portfolio Standards Act (AEPS) of 2004 is an important part of Pennsylvania’s energy legislation. It was required that a certain percentage of the electricity purchased in the Pennsylvania wholesale energy market be made specifically from renewable sources. AEPS stipulated that at least 0.5% would come specifically from solar energy before this year. Today, renewables are still a categorically small part of Pennsylvania’s energy circle, accounting for just 5.1% of electricity generation at the end of 2020 (the US average is 22.5%, according to the Energy Information Association). Of this proportion, Solar supplied 0.31% of the electricity located in Pennsylvania, which is very small compared to neighboring New York (2.32%).

All in all, what could be the best avenue for solar in Pennsylvania? The “Finding Pennsylvania’s Solar Future” project aims to identify strategies to increase solar energy to 10 percent of state consumption by 2030. An effective way to do this could be to focus on smaller solar systems (such as residential roofs) which also forecast more jobs. Solar modules for residential buildings are “grid-tied”. So if a house produces more solar energy than they consume, the excess is fed back into the grid and you receive credits for it. Given Pennsylvania’s geographic location, this could be a more viable option for the future of solar energy.

I am very happy to have a solar park in my new garden. So much of our energy infrastructure is hidden in sight that it can easily be taken for granted. The solar panels outside were enough to make me stop and think about where my electricity is coming from and why it’s so important. As we steer our transition from over-reliance on fossil fuels to cleaner energy sources, it is clear that solar power has become an increasingly important piece of the puzzle. The question remains, how can we best use it here at home?


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