Electricity has become such a vital element that is so interwoven in society that we cannot function without it. Electricity usage, in general, has grown tremendously in the last 50 years, where in 2020, the United States consumed a total of 3.80 trillion kWh. While this demand is not projected to increase dramatically from year-to-year, it is projected to have an annual growth of about 1% from 2020 to 2050 [1]. We know electricity will always be in massive demand for residential, industrial, and commercial purposes and one lofty (but necessary) goal many important players around the world have put together is becoming net zero by 2050. Net zero is the state at which the amount of Greenhouse gas (GHG) emissions going into the atmosphere equals the amount going out. Right now, non-renewable energy sources such as coal, natural gas, oil, and nuclear, represent a significant percentage of the electricity provided to the grid, all which generate an unhealthy amount of GHG emissions being sent out into the atmosphere.
This GHG issue is urgent and one way to still generate electricity without compromising the health of our planet is by using renewable energy sources, which have no (or very little) GHG emissions tied to their production processes. While renewable energy growth has increased in recent years, renewable energy generation was only about 20% of the total energy generation in the United States in 2020, which is shown in Table 1. This renewable energy generation was dominated by wind and hydropower, which accounted for almost 16% of the total energy generation [2].
Table 1: U.S. Electricity Generation (Utility-Scale) Broken Down by Energy Source, Amount, and Percentage of Total in 2020 [2]
| Energy Source | Amount (Billion kWh) | Share of Total (%) |
| Total- All Sources | 4,009 | |
| Fossil Fuels (Total) | 2,419 | 60.3 % |
|
1,617 | 40.3 % |
|
774 | 19.3 % |
|
17 | 0.4 % |
|
11 | 0.3 % |
| Nuclear | 790 | 19.7 % |
| Renewables (Total) | 792 | 19.8 % |
|
338 | 8.4 % |
|
291 | 7.3 % |
|
91 | 2.3 % |
|
56 | 1.4 % |
|
17 | 0.4 % |
| Pumped Storage Hydropower | -5 | -0.1 % |
| Other Sources | 13 | 0.3 % |
Although this usage has gotten higher over time, there is still a long way to go in fully implementing renewable energy processes to dominate the electric grid to reach net zero by 2050.
One major issue with renewable energy sources is the fact that they are contingent upon external factors, such as the time of the day and how windy it is. For example, solar panels can only generate electricity during the day when the sun is shining. This timing is especially unfortunate due to the electricity demand during the times when solar panels are generating the most energy. This can be seen in the duck curve (which resembles the shape of a duck, hence the name).
Figure 1: Electricity Demand Relative to Time of Day [3]
As can be seen in Figure 1, electricity demand is lowest in the range of about 8 am to 5 pm. But, this is the time of the day when solar panels are working their best since the Sun is shining. Without a way of storing this energy, this energy generation is unessential since we are not in dire need of electricity at those times and the solar panels cannot provide much, if at all, when energy demand is highest at around 8-9 pm.
So, if we run into these issues like the one discussed above when using renewable energy sources, how do we transition our grid to become renewable energy focused? The answer to that question is energy storage. Energy storage would allow us to still get this energy during the times when the renewable energy sources are working at full capacity or when we want them to, without having to waste some of the electricity that is produced. We could generate the energy and store it until it was needed. Building off of the example from before, we could generate the solar energy during the day when the solar panels are being the most productive but is not needed and store this excess energy until it is needed when the energy demand is highest later into the day. This would reduce all energy generation waste that is coming from renewable sources due to the issues that are currently handicapping them. This would allow us to bridge towards renewable energy sources becoming the main electricity generation source and eventually having a fully renewable electric grid, saving our atmosphere in the process. This is feasible because we could use renewable energy production processes when they are running best and store the excess energy for when it is needed on the grid, having a steady supply of electricity that is needed at all times. But, without some effective and applicable energy storage method(s), we will not ever be able to reach the point of running only on renewables.
This trend towards renewable energy and the necessity for renewable energy storage is tied into the market for electric vehicles (EVs). EVs are vehicles that run on batteries or on electricity from some source that it is in contact with or has access to. As renewable energy sources have become a focus on limiting our GHG emissions to help us become net zero, EVs have also been put in the limelight due to the hefty amount of GHG emissions that are emitted from cars each year. To put it into perspective, a normal, everyday vehicle puts roughly 4.6 metric tons of carbon dioxide into the atmosphere each year. On the other hand, an EV will not emit any [4]. It is obvious how much transitioning to EVs would be in creating a healthier atmosphere since the outlook of the EV market is tied pretty heavily to the renewable energy market. Once we make renewable energy a focus, the EV market will follow, or vice versa. They could be powered by renewable energy sources, which would create a total process that leads to essentially no GHG emissions.
The current outlook for the EV market is pretty variable, depending on numerous external factors, such as politics, renewable energy production, gas prices, and battery characteristics. As Figure 2 shows, the EV market has increased substantially in the U.S. in the last seven years.
Figure 2: Year-by-year growth of EV sales for 2015-2021 [5]
The growth of the share of new vehicle sales has increased each year, except from 2018 to 2019, showing just how much of an increasing role EVs are playing in society. If we continue on this trend, EVs will soon be at the forefront of our vehicle fleet. This is not to mention that there are other countries that are at a higher growth rate than the U.S., where Europe is expected to reach 15% of the share of new vehicle sales by 2021 [5]. The outlook of the future of EVs globally, although hard to accurately predict, is pretty substantial, too. In 2020, there were an estimated 8.5 million EVs in the global fleet; this number is projected to grow to 115 million EVs by 2030 [6]. While this number is still very substantial, if the external factors that affect the EV field influence EV development positively, the actual number could be much larger than this. Ultimately, EVs have (to an extent) and will increasingly in the future play a key role in the automotive and renewable energy markets.
To keep up with the pace of, and encourage, the development of EVs and their integration into society, there needs to be some sort of charging system in place that would allow for all vehicle owners to have access to charging their vehicles. In addition to, or in place of, having charging elements at the vehicle owner’s house, there should be access to charging in more readily available places. Whether these are set-up similar to how gas stations are now, or just in public places like a parking lot, there is a necessity for commercial charging stations to be mainstream implemented for EVs to fully make their commanding presence in the vehicle market. There are numerous concerns with using EVs as a personal vehicle and one of these is the mileage range on one charge. One who thinks about purchasing an EV has to think about the potential of not having a place to charge their vehicle if they wanted to travel somewhere that is not local, whether that is a long road trip or a day trip. This is a possible scenario due to the small availability of commercial chargers for public use in our current society, and will really hamper this market until it becomes more common for charging stations to be available for use. Also, having efficient charging stations to implement that store renewable energy and can use that to power an EV (rather than using sources like fossil fuels) would create a process that leads to virtually no GHG emissions. This would be great for both public and private use, and would help encourage the growth of EVs, as well as the growth of EV chargers to supplement the growth.
Figure 3: Our Need Finding Diagram for CAES System with Potential EV Charging Integration
Sources:
[1] “Electricity explained ,” U.S. Energy Information Administration (EIA), 07-Apr-2021.
[Online]. Available: https://www.eia.gov/energyexplained/electricity/use-of-electricity.php. [Accessed: 30-Sep-2021].
[2] “Frequently asked Questions (FAQs) – U.S. Energy Information Administration (EIA),”
U.S. Energy Information Administration (EIA), 05-Mar-2021. [Online]. Available:
https://www.eia.gov/tools/faqs/faq.php?id=427&t=3. [Accessed: 30-Sep-2021].
[3] “Confronting the duck curve: How to address over-generation of solar energy,”
Energy.gov, 12-Oct-2017. [Online]. Available: https://www.energy.gov/eere/articles/confronting-duck-curve-how-address-over-generation-solar-energy. [Accessed: 30-Sep-2021].
[4] “Greenhouse Gas Emissions from a Typical Passenger Vehicle,” EPA. [Online]. Available: https://www.epa.gov/greenvehicles/greenhouse-gas-emissions-typical-passenger-vehicle.
[Accessed: 30-Sep-2021].
[5] B. L. McDonald, “Forecast: 2021 US EV sales to increase 70% year over year,”
CleanTechnica, 30-Oct-2020. [Online]. Available:
https://cleantechnica.com/2020/10/30/forecast-2021-us-ev-sales-to-increase-70-year-over
-year/. [Accessed: 02-Oct-2021].
[6] M. Carlier, “Number of electric vehicles in use globally 2020-2030,” Statista,
05-Aug-2021. [Online]. Available:
https://www.statista.com/statistics/970958/worldwide-number-of-electric-vehicles/. [Accessed: 02-Oct-2021].