Breaking the Limitations of Solar Energy

By Sophia Ahmed
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New York City aims to install  1 gigawatt of solar capacity by 2030, which could power approximately 250,000 households. This would give these 250,000 households not only cleaner, but also cheaper energy; the average Brooklyn household could save $64,796 over 20 years with investment in solar energy. Additionally, using solar power in place of oil decreases greenhouse gas emissions  as well as water pollution and hazardous waste production. Despite the benefits of using solar energy, high installation costs and technological barriers create obstacles and consumer hesitation.  These issues could prevent the fulfillment of New York City’s goal, but labs at Columbia University’s Lenfast Center for Sustainable Energy are working to break through these restrictions.

While households can save $64,796 over 20 years from investing in solar power, the non-subsidized upfront cost of installing solar panels in Brooklyn isan average of $21,500. This high fee comes primarily from two sources: labor and hardware. Warranties, complex roofs, and updates on building electrical systems all increase the time and cost of labor required to install solar panels. Without a warranty, the maintenance of solar panels costs an average of $30 per megawatt hour; being that the average American household uses just below 11 megawatt hours of electricity per year, this approximately equates to a maximum of $6,600 in maintenance over twenty years without a warranty.  
Additionally, complex roofs include rearranging a typical layout of panels, such as having to stack them on top of each other, increasing hardware and installation costs. Furthermore, if a roof is made of certain materials, like tile or slate, installation costs will also rise. Lowering labor costs becomes difficult because paying for warranties and installation complexities are unavoidable. This leaves decreasing hardware production cost as the most feasible solution to decreasing solar panel installation costs, which is exactly what the Esposito Research Group at Columbia University is doing.

The Esposito Group is evaluating solar energy systems to improve manufacturing techniques and panel efficiency. Moreover, it is also testing the use of 3D printing to manufacture photo-electrochemical devices for testing cells and reactors. This could speed up the testing of new technologies, thus decreasing research and development costs and potentially lowering overall prices. Additionally, if production using 3D printing proves efficient and effective, it could be used to produce panels for consumers in addition to being used in the lab. By using 3D printing to manufacture panels for the market, manufacturing costs could decrease and the quantity of panels could increase, leading to an overall decrease in hardware costs.

While lowering installation costs can encourage further household investment in solar energy, issues with current solar technology and efficiency also create consumer hesitation, preventing costs from decreasing. A primary issue with solar energy is its volatility in energy production. Despite the seemingly infinite supply of the sun, you can’t control its abundance on a daily basis, especially in the depths of a New York winter, when more electricity for heat is needed and there is less sun exposure. There are two potential solutions to this issue: increasing solar cell efficiency so panels  can create more usable energy even when there is less sun exposure and increasing the energy storage capacity of solar panel systems.

Current solar panels convert an average of 15% of the sun’s incoming energy into usable energy. While this may seem like a small amount, increasing energy conversion efficiency will be challenging due to limits on the amount of sunlight that can be captured and converted to usable energy . For example,the Shockley-Queisser limit takes radiation, absorption, and energy loss into account to conclude that the maximum theoretical amount of sunlight capturable by a photovoltaic (solar) cell is 33.7%. Furthermore, the thermodynamic efficiency limit takes the different band-gap widths of photons into account to demonstrate that the absolute thermodynamic efficiency for solar cells is 86%. Band-gap widths are the gaps between electrons in a photon and they vary in every incoming photon, and solar cells can only successfully convert photon energy into usable energy for certain band-widths. Even if a technology that allowed panels to work with a variety of band-gap widths was developed, some incoming photon energy is released as heat, inherently making 100% efficiency impossible.

While the laws of thermodynamics remain unbreakable, the Shockley-Quiesser limit can be broken—but research has shown that this involves a complex and expensive process of adding extra layers to solar panels. But do we even need to explore these complex processes to make solar cells more efficient than their current rate? While the average solar cell only operates on a 15% solar conversion efficiency rate, this rate effectively powers a household on a sunny day. Thus, the primary problem with solar cells does not involve their efficiency but rather their lack of energy storage capacity for use on cloudy days.

The variable output of solar energy as well as the lack of solar energy at night makes improving energy storage crucial for the future of the solar industry. Two different lab groups at Columbia are working on novel methods for energy storage: batteries and fuel cells.

The Yang Research Group is tackling issues with batteries on two fronts. Its first method is to study dendrite formation in the negative electrodes of lithium batteries. Dendrites are filaments that form in the negative electrode, decreasing battery life and potentially causing units to inflame. By studying dendrite formation, battery life can be elongated and units made safer. The Yang lab has also developed a tri-layer structure that increases the energy density of a lithium battery and makes it cheaper to manufacture. By working towards making batteries cheaper, safer, and more efficient, the Yang Lab is furthering advancements in solar energy storage which can, in turn, encourage consumer confidence.

Fuel cells, another way solar energy can be stored, work by converting stored chemical energy into electricity when needed. While not working directly with solar energy, Diego Villarreal of Columbia University is working with reversible solid-oxide fuel cells, which convert excess solar energy into hydrogen, which can then be stored and used in a hydrogen fuel cell for when there is not enough solar energy supply.

The two primary issues driving consumer hesitation in solar power are costs and technological barriers. But these issues need to be further analyzed to find out how to drive costs down and advance solar technology. Costs themselves come from two main sources: labor and hardware, and given the inevitable complexities of the labor involved in panel installation, focusing on decreasing hardware costs appears to be the most effective route in decreasing overall costs. Among other technological frontiers in solar energy, efficiency and storage stand out as issues that can make consumers question investing in solar energy. When analyzing these two issues, it becomes evident that storage investment offers researchers a larger opportunity to make solar energy more widely used. By providing us with solutions to these issues, scientists at Columbia and many other institutions are making this world a greener and more sustainable place for us to live in.

Sophia Ahmed is a freshman in Columbia College planning to major in sustainable development