South Australia - a renewable state?

Figure 3:Storage of surplus wind farm energy to match demand

The challenge is to identify storage technology for some 300 GWh of supply. The base case is to calculate the amount and cost of lead acid batteries to satisfy this need.

A very thorough summary of storage technologies is to be found in Sustainable Energy. Figure 4 is a summary of the storage technology power and energy density capabilities. The range of batteries extends from lead acid to lithium-ion and beyond. For this analysis the energy densities are the mid range values for lead acid and lithium-ion.

On the bottom far right of the figure, the hydrocarbons (fossil fuels) show energy densities of a factor of ten greater than the batteries considered here.

Figure 4:Scatter plot of power and energy density for storage technologies from page 400 of Sustainable Energy, Second Edition2012 by J W Tester, E M Drake, M J Driscoll, M W Golay and W A Peters MIT Press.

So for the lead acid batteries adopting a value of 40 Wh/kg for 300 GWh of storage requires 7,500,000 tonnes of lead acid batteries. For higher energy density lithium-ion batteries have an energy density of 140 Wh/kg so only 2,100,000 tonnes would be needed.

But this could be realized at what cost? Estimates of lead acid battery costs are around $0.20 per Wh while lithium-ion batteries vary from $0.50 to $0.90 per Wh. The Power Wall 2 lithium-ion battery from Tesla is A$8,000 for 14 kWh but this is a retail price of $0.57 per Wh. The wholesale bulk price could be as low as $0.30 per Wh with better performance than the lead acid battery in discharge rate and lifetime.

Willem Post has a detailed article on energy storage in Germany. His base case is lead acid batteries with massive, bulkenergy storage. The cost per Wh is $0.32.

So the battery storage is some $60 to $90 billion to store the surplus energy from 4,000 MW of new wind farms with substantial running costs due to battery lifetime and erratic discharges.

This analysis outlines the storage required to address wind's inherent intermittency. It does not address the requirements, presently unaddressed by wind energy technology, of grid stability and control, which is the need for the provision of synchronous inertia to protect grid stability. Should the battery route be chosen to address this requirement, such provision may indeed require more battery storage.

Of course South Australia could close all the gas fueled power stations and build massive interconnectors to the other states and then blame them for CO2 emissions. Perhaps that is why the South Australian government talks of nationalizing the power stations.