Seeking Consensus on the Externalized Costs of Battery Storage
- August 8, 2017
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What is meant by “externalized costs”?
Externalized costs are costs associated with energy consumption which is not reflected in the selling price of the energy. These costs are directly or indirectly paid by other sectors of the economy in forms such as increased healthcare expenditures, losses in property values, increased costs associated with natural disasters, and a reduction in the free services rendered by the biosphere.
Externalized costs of battery storage
Environmental impacts of battery technology arise primarily from substantial quantities of embodied energy required and the mining of rare-earth materials. Li-ion batteries are by far the most thoroughly studied subject and we will assume that their external cost also applies to other battery chemistries.
A very recent review of 113 studies has provided a good summary of the environmental impacts of Li-ion batteries. As can be seen in the summary graph below, significant scatter is present between different studies and different Li-ion battery chemistries.
Key for environmental impacts: ADP = Abiotic depletion, AP = Acidification, GWP = global warming potential, EP = Eutrophication, ODP = Ozone depletion and HTP = Human toxicity.
Key for battery chemistries: LFP = Lithium-ion phosphate, LTO = Titanate, LCO = Lithium Cobalt oxide, LCN = Lithium cobalt nickel oxide, LMO = Litium manganese oxide, NCM = Lithium cobalt manganese oxide, NCA = Lithium nickel cobalt aluminium oxide.
The global warming potential is the most commonly studied topic in the literature and returns average equivalent CO2 emissions of about 110 g/Wh. For perspective, this implies a CO2 cost of 6.6 tons for the 60 kWh battery pack of the Chevy Bolt – equivalent to 40000 miles of gasoline emissions in a Prius.
However, the study notes that, although global warming potential is the most studied environmental impact of Li-ion batteries, it is arguably less important than other aspects. The following graph is presented where average environmental impacts are normalized by the total impact in Europe.
It is clear that global warming potential is mild relative to abiotic depletion, acidification and human toxicity. When monetizing externalities, it therefore appears reasonable to express other externalities as a cost that is somewhat larger than the cost of climate change. Assuming a 50/50 split between deployment in developed and developing countries, the CO2 price comes to $36/ton. If we double that to account for other external costs, it amounts to $72/ton or $8/kWh of battery capacity, which is quite low relative to the internalized battery costs. We will add another 50% for externalities related to other components (inverter, cabling, BOS), bringing the total up to $12/kWh. Assuming an average of 50% depth of discharge per day for 10 years at a discount rate of 5%, the total externality amounts to $10/MWh of stored electricity.
To compare to internalized costs, note that the Tesla Powerpack hardware currently costs $420-630/kWh depending on scale. Using $500/kWh in the internalized costs calculations presented earlier returns an energy storage cost of about $400/MWh for an average of 50% depth of discharge per day.
If you have a number that differs significantly from the estimates given above, please add it in the comments section below together with an explanation and a reference.