Some emerging technologies pave a bright path for the future of Large Scale Batteries
As we move towards more renewable energy sources and away from fossil fuels, we will need new technologies to capture energy production as well as provide new ways to store and deliver power. An ongoing issue with solar and wind production is the inability to predict exactly when you can produce and dispatch power. Additionally, we are seeing more interest for generating, storing, and time-shifting power in other ways to meet environmental goals. Large Scale Batteries are an exciting step toward meeting, and supporting, some of those goals.
While we don’t know what the future will bring, there are some forecasts that predict substantial drops in the cost of the various storage technologies as there is more adoption into the marketplace. Among these, in 2014 Citigroup analysts predicted a drop in battery storage costs to $230/kWh by 2020 and a further drop to $150/kWh in the years after that. Whether it is from the reduced cost or simply an increased need, Navigant Research forecasts worldwide battery storage to grow to almost 14 GW by 2023.
Graph 1: IRENA.org Source
These potential reductions in costs could even lead to some ‘grid defection’ as the economics change and become less of a hindrance for adoption.
Graph 2: IRENA.org Source
Tesla founder Elon Musk has been working with lithium-ion technology both for vehicle battery and grid-level storage for over five years. Li-ion is a familiar battery type, typically a pair of solid electrodes and an electrolyte, and has been around for a long time in smaller applications… Tesla (and other companies) is currently testing larger scale battery installations, currently only for households and businesses. In the future they are looking at becoming scalable for utility systems. Some advantages and disadvantages to Li-ion are:
· High-energy density
· Low maintenance
· Low self-discharge
· High cost to manufacture
· Limited number of charging cycles (They age and will need to be replaced.)
· Heat generated during use
Figure 1: EnergyStorage.org Source
Meanwhile others are pursuing what is known as “as “flow battery” technology. This is aptly named, in that it contains two liquids that flow next to each other, separated by a membrane, and as they move past each other create an electrical current. These batteries use two electrolytes in separate tanks, which are then pumped into a central stack. The central stack has an ion-conducting membrane that captures the electrons as the two liquids are pumped through the stack. Currently, most new flow batteries use a membrane containing vanadium. Some advantages and disadvantages to this technology include:
· Electrolyte solutions are safe, non-flammable, and non-corrosive
· The two electrolytes are compatible and easily rechargeable
· Expected to handle many more cycles than Li-ion batteries
· Maintenance cost of the tanks and pump system are high
· Overall cost is higher $/KWh than Li-ion
· Low energy density
· The volume of space that the tanks may take up
Figure 2: EnergyStorage.org Source
A promising hybrid of these two technologies is also being tested, using solid materials in two separate tanks with an electrolyte fluid that passes over them. The solid material can be lithium-based, while the flow of the liquid then conducts the electrons to the cell stack. Although still in testing, this looks to combine the scalability of flow batteries with the power density in Li-ion batteries.
Figure 3: Eletrochemical Society Source
The need for large scale energy storage will continue to grow as we move forward with renewable energy sources making up a larger portion of our energy generation. The inconsistency of renewables’ generation and the need for maintaining a stable grid will necessitate some form of storage. These are just a few of the most promising utility scale battery technologies that are currently available. Skeptics could argue that technologies like GTs or hydro which are currently used to firm up intermittent renewables will continue to do so in the future. That may be likely in some cases but those current technologies have their own issues. There are environmental and locational issues with hydro; there are pipeline access and saturation issues with small gas. Whatever technology moves us forward it seems apparent that battery storage will be an integral part of that future.