Nearly one hundred years after the United States entered an era of economic prosperity, the 2020s are set to usher in a new wave of socioeconomic expansion. However, instead of an era of hyper-consumption, the ‘20s of this century will see a green energy boom. Thirty-eight states, four U.S. territories, and the nation’s capital have all set goals to relinquish their dependency on fossil fuels by the end of the coming decade. High aims for renewable energy security in California, Hawaii, Vermont, and others, along with a nationwide push for a Green New Deal, are showing that the movement to curb greenhouse gas emissions is gaining speed.

The implementation and popularization of renewable energy do face some challenges. The largest potential hindrance to meeting the energy goals of the 2020s is the intermittent nature of renewable sources. The demand for energy persists indefinitely, but the ideal conditions for renewable energy production vary. When the sun doesn't shine, the wind doesn't blow, and renewable resources aren’t providing enough energy to meet grid demands, inefficient “peaker” fossil fuel power plants fire up. But as we progress into an era of necessary obsoletion for fossil fuels, we must look elsewhere to provide ‘baseload power.’ Some renewable power sources such as geothermal, molten salt, concentrated solar, in-stream hydro, and tidal power have the potential to act as necessary substitutes, but as of now only constitute a fraction of our total renewable capacity.

Fortunately, other renewable technologies have matured extensively over the last ten years and are poised to surpass unsustainable fossil fuel power. Solar panels and wind turbines, now capable of generating more power than immediate usage demands, can begin to more effectively replace oil, coal, and gas. With the right method of energy storage implemented to capture this surplus, our grid could draw from renewable reserves rather than from fossil fuel power plants in times of intermittency. The results could reduce or potentially eliminate our dependence on fossil fuels.

But how can we store enough energy to reliably serve our demands? As of now, experts deem battery and pumped hydro the most promising candidates for energy storage technology.

One of the quickest growing utility-scale energy storage methods is Advanced Battery Energy Storage (ABES). Optimistic projections determined through an analysis of load profiles of lithium ion, lead acid, sodium sulfur, and flow cell batteries place global battery storage capacity at 1,000 gigawatts within two decades—enough energy storage to power 118,000 U.S. homes annually. Similar to everyday consumer batteries, ABES contains three vital components: An anode, a cathode, and an electrolyte. The materials in which these components are constructed determine the type of battery. Though various forms of batteries such as lead-acid, nickel-based, sodium-based, and flow cell are used in ABES systems, 80 percent of these systems are composed of lithium-ion batteries. The storage process involves connecting the batteries to a renewable resource, such as solar panels or wind turbines, which provide electrical charge. Once charged, a grid operator may discharge the battery to supply instant, highly efficient baseload power to the grid. This method is reliable and can be constructed nearly anywhere, making it a favorable choice to developers.

In fact, Moss Landing, California is already set to develop the world's largest battery system by the end of 2020.

Following a 4-1 vote by the California Public Utilities Commission in November of 2018, Pacific Gas & Electric (PG&E) will partner with Tesla Inc. and Vistra Energy Corp. to develop four large-scale lithium-ion battery systems in lieu of continuing the use of three natural gas power plants owned by Calpine Energy Solutions. The total battery capacity of the projects will be 567.5 megawatts (MW); In comparison, natural gas and coal power plants operate at 500-800 MW and nuclear plants operate around one gigawatt (GW). Additionally, batteries retain the benefit of instant charge and discharge. Natural gas, coal, and nuclear plants take hours or days to reach full capacity once turned on.

A battery storage project of this size is significant in a few ways. One of this capacity has never been developed nor implemented into a grid. If successful, the Moss Landing battery storage project will further demonstrate the feasibility of a grid that is independent of fossil fuel power plants. Additionally, this project marks the crossover point where renewable sources have become more economically viable than natural gas, meaning the success of this project will provide the economic incentive and insight for other utility companies who are looking to make the switch.

Yet, current battery production comes with more costs than what PG&E or other adopters of battery storage have paid—the high external price of environmental degradation and worker exploitation. Significant challenges come with the fact that many types of batteries, especially at industrial sizes, require large amounts of lithium, cobalt, iron and manganese. As the demand for these batteries grows, so will the scope of the mining industry and potential human rights violations associated with it.

In the “lithium triangle,” situated among Argentina, Bolivia, and Chile, the presence of mining operations results in freshwater contamination, insufficient sewage systems, and exploitation of Indigenous communities. The ongoing imperialist venture to extract valuable minerals from South American reserves is set to expand under the boom of green energy, driving the need to enforce sustainable mining practices.

Another form of sustainable energy may be the solution. Geothermal mineral recovery uses naturally occurring heat from the Earth to “extract and purify” mining debris from water, potentially restoring clean, drinkable water to Indigenous communities in South America. But until that technology develops further, it remains essential to look toward other sustainable storage options.

Pumped Hydroelectric Energy Storage (PHES), an existing sustainable storage system, makes up 97 percent of our current energy storage capacity and is set to expand even more within the next decade. PHES operates in a fashion similar to other hydroelectric power sources but provides a water pumping mechanism for continual energy cycling. By placing two or more water reserves at different elevations, water can be released from the upper reserves into the lower ones, spinning a turbine on the way to produce power. The water is then pumped back into the higher elevation reserve using solar- and wind-generated power when customer electricity demands are low. The repetition of this process allows for the continual storage of potential energy that can be converted into usable energy whenever the grid demands.

Using a geographic information system (GIS) program, researchers have recently identified 530,000 sites suitable for PHES implementation. The determined storage capacity potential exceeds 22 million Gigawatt-hours (GWh)—an equivalent of our global energy demand and an excess of our global storage needs. Even with the construction of just a small percentage of total identified sites, PHES could play a leading role in the advancement of renewable energy.

However, like battery storage, pumped hydro comes with its own set of challenges. The initial capital costs of construction are high, and the process can take years of development to complete. Furthermore, ecological impacts on local wildlife and water runoff as a result of PHES construction are likely at some sites. In order to properly implement PHES systems with minimal environmental impact, in-depth research on several fronts is necessary. This research will allow for a new definition of which sites are suitable for PHES. Lastly, PHES is an old idea. Although its development is set to expand, technological developments may not result in major cost reductions, while job and site conversions may. Government subsidies to turn old coal mountaintop-removal mining sites into PHES may allow for coal companies to transition into the renewable sector.

Every bit of carbon that we pump into the atmosphere bolsters the urgency for our independence from fossil fuels. With global temperatures rising and the deadlines to our climate objectives sitting on the other side of just a few years, emerging energy solutions must be implemented as soon as possible. It remains critical that our decisions about the future of energy be made with great care, with the livelihood of the next generation in mind. The technologies of battery and pumped hydro storage may provide the solution to the independence we seek. Although there remains work to be done to improve our storage solutions, we cannot stall in the process of replacing old fossil fuel power plants with clean, renewable energy storage.