Researchers Quantify Cost Targets for Storage of Renewable Energy

Energy storage cost will be crucial in estimating how much renewable energy could help in decarbonizing electricity. However, to what extent should energy storage costs decrease?

Researchers at MIT have found a solution to this in a study reported in Joule on August 7th, 2019. They measured cost targets for storage technologies to allow wind and solar energy with storage to attain competitiveness with other on-demand energy sources. They also investigated the types of batteries and other technologies that can help achieve these goals.

One of the core sources of uncertainty in the debate about how much renewable energy can contribute to the deep decarbonization of electricity is the question of how much energy storage can be improved.

Jessika Trancik, Study Senior Author and Associate Professor of Energy Studies, Massachusetts Institute of Technology

She continued, “Different assumptions about the cost of energy storage underlie significant disagreements between a number of assessments, but little was known about what costs would actually be competitive and how these costs compare to the storage technologies currently being developed. So, we decided to address this issue head on.”

Quantifying cost targets for energy storage required a new piece of insight,” she stated, “about how patterns of the renewable energy supply, and fluctuations in this supply, compare to electricity demand profiles. Large but infrequent solar and wind shortage events are critical in determining how much storage is needed for renewables to reliably meet demand, and it’s important to understand the characteristics of these events.”

As part of the study, Trancik and her team determined the costs of using storage along with solar and wind energy to reliably provide different output profiles for a period of two decades.

Later, they determined cost targets for energy storage that would allow plants to attain cost-competitiveness with conventional power sources. In addition, they assessed existing and future energy storage technologies against the predicted cost target.

Their model optimizes storage costs using any combination of solar and wind and storage that can offer low-cost power. This often implies increasing solar and wind capacity with respect to an aimed output, to reduce the storage amount required.

The study also investigated the characteristics that differentiate different storage options. Some technologies can store more energy at a lower cost but produce slowly at lower power, whereas others can economically store less energy that can be quickly discharged at high power. Trancik stated that the model, therefore, has to capture these differences.

Researchers discovered from the study that technologies with energy storage capacity costs less than $20/kWh could make cost-competitive baseload power available over a period of two decades, although this target changes with the location and target output profile. They also discovered that power costs respond more to costs of storage energy capacity than power capacity.

Trancik remarked that the study showed that “it’s critical to reduce the costs of the materials and manufacturing that contribute to the cost of the storage energy capacity.”

The numerical target we estimate, which varies with location, could mean a 90 percent drop in storage costs relative to today's technologies. It's a large drop but some technologies do tend to improve a lot, as we've seen in the case of solar panels, for example.

Jessika Trancik, Study Senior Author and Associate Professor of Energy Studies, Massachusetts Institute of Technology

According to her, “However, and importantly, there is another factor that could raise this target considerably and allow more expensive technologies to cost-competitively store renewable energy, which is to use supplemental technologies for a small percent of the time.”

The scientists reported that if the renewable energy system fails to fulfill the demand for just 5% of the hours over a period of two decades, it can reduce the cost of renewable electricity by half.

Trancik added, “The trick there is to figure out how to supply electricity for the remaining 5% hours. That’s where we need to focus our efforts. This could potentially be accomplished with supplemental generation technologies, or perhaps demand-side management.” She also stated that the expansion of the electricity transmission grid could also help reduce fluctuations in renewable energy supply.

The scientists are investigating alternatives for cheap and low-carbon additional technologies. They are also striving to model how certain economies of scale and research directions can help lower the costs of battery technologies.

This study was financially supported by the MIT Portugal Program and the Alfred P. Sloan Foundation.


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