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  • Writer's picturericcardo

Lithium, coal and hydrogen

#energy #batteries #lithium #hydrogen #renewable


Are lithium’s reserves enough to transition the entire world to sustainable energy through lithium batteries?

After the recent post on this blog discussing the possible math of how 100 Tesla Gigafactories could allow the transition of the entire world to sustainable energy, it seemed appropriate to add a more in-depth analysis on the availability of the raw material required to implement that scenario. In the discussion below, the focus will be on the total capacity to be built every year, regardless of the producer or producers. The general question will be: is it possible to source enough lithium for all the cars, smartphones, house batteries and all the other installations required for a complete transition to renewable energy? The following analysis will assume only lithium batteries and it will include any possible chemical composition of the cathode, the element currently differentiating them: Lithium / Manganese (Nissan Leaf), Lithium / Cobalt (Apple iPhone) and so on. Therefore, the focus will be on the main ingredient, lithium. Lithium’s reserves will also be compared to the reserves of coal, that is the current main energy source. A final comparison with hydrogen, often discussed as an alternative to lithium, will be presented at the end.

The previous post showed that after accounting for the electricity not needing storage because directly used, and accounting also for the compounding annual growth of the demand of electricity through the next 15 years, the battery capacity to be produced would be about 15 TWh/year. The ramp-up period was assumed to be about 15 years, comparable to the average life of a battery, therefore, the same throughput reached after 15 years will be associated to the replacement of the aging batteries in time and will be used to calculate the years of available reserves.

Diving into the calculation:

A small-sedan car's battery with 85 kWh of capacity may have about 7-10 kg of lithium in its battery; that is about 0.1 kg of lithium per kWh -- it may be optimistic at the moment but, it should include some future improvements. Therefore, 15 TWh/yr would require about 1,500,000 MT (Metric Tons) of Lithium per year to be produced. According to public estimates, current worldwide lithium's reserves are about 13,500,000 MT (mostly in Chile, Argentina, China and Australia; see picture below), resulting in about 9 years of available lithium once the battery yearly production have reached steady state regime and complete transition. Assuming that a big part of the available amount (about 5,000,000 MT) would be used during the ramp-up from the current 40,000 MT of lithium used worldwide every year to the 1,500,000 MT/year, reserves for the period after the sustainable transition is obtained are closer to 6 years. Therefore, even assuming strong focus of the battery industry on lithium, reserves should be enough for the next 20+ years (15 years ramp-up + 6 years).

The 5 MM MT above is the result of compounding the current 40,000 MT/yr at 30% per year.

20+ years may be subject to improvement as the amount of lithium per kWh required in batteries decreases in time. Some calculations show that, even today, the lithium required may be as low as 0.08 kg/kWh, resulting in 1,200,000 MT of lithium consumed per year.

Just to have a reference, it may be interesting to compare lithium’s reserves with those of coal, the current most common source of energy for electricity generation. Hopefully, though, lots of that available coal will stay unused.

Coal accounts for about 40% of the electricity produced worldwide (picture below), corresponding to about 6 Bil MT/yr of coal burned at electricity-production plants every year -- the interested reader can find the calculation below. Coal’s reserves are estimated to be a little more than 200 Bil MT worldwide, resulting in more than 30 years of reserves at current rates of utilization.

The calculation for the 6 Bil MT/yr above is the following:

Average coal’s calorific value = 18,000 kJ/kg

Average power-plant total efficiency = 33%

Heat to provide per kWh [3,600 kJ] = (3,600 kJ) / 33% = 10,900 kJ

Kg of coal required per kWh = 10,900 / 18,000 = 0.6 kg / kWh

Considering the current 25 TWh / yr of electricity consumed worldwide: 40% (coal share) x 25 TWh/yr x 0.6 kg/kWh = 6 Bil MT of coal burned per year

So, it seems that lithium reserves are enough for the transition to happen during the next 15 years and prosper for something less than a decade after that. However, some readers may think lithium reserves are not exceptional or that the technology itself is not the best available solution, therefore, it is worth comparing lithium battery technology with another possible energy-storage method often discussed in automotive, hydrogen.

Hydrogen does not seem to have reserves’ issues being hydrogen the most abundant element in the universe. Considering similar applications on energy storage, issues with hydrogen are mostly related to the fact that it has to be extracted from water (H2O), compressed, stored and transformed back into electricity through fuel cells. At the moment, the sustainable way to extract hydrogen from water is electrolysis, using electricity generated from renewable sources to separate hydrogen from water. However, the overall efficiency of the hydrogen system is negatively affected by the series of steps and transformation listed above.

Instead of going through the calculation of the efficiency of hydrogen vs lithium batteries, it is possible to discuss it intuitively applying the discussion to cars: battery electric vehicles store electricity directly into the batteries, while hydrogen vehicles use that same electricity to extract hydrogen from water through electrolysis, compress it into tanks and transform it back into electricity inside fuel cells. In general, when additional stages are added to a series, additional losses of efficiency compound (multiply), resulting in a lower total efficiency. Hydrogen cars' efficiency is about half the efficiency of a battery EV, the comparison comes close to 30% vs 60%.

Note: hydrogen cars do not have battery leakage because they store energy in the form of compressed hydrogen into tanks, therefore, they recover at least part of that loss common among battery EVs. However, hydrogen vehicles still have batteries, likely not lithium based though, in order to recover energy from braking. That component does not affect too much the comparison of the efficiency of the main cycle but, it adds to the overall complexity and cost.

To conclude, hoping the transition to renewable energy happens as fast as possible, lithium batteries seem to be winners against hydrogen from an engineering point of view. Moreover, lithium's reserve, while not exceptional, do not appear to be critical. However, hydrogen seems to be at the moment something that could participate in the transition with applications where current lithium technology would not be suitable or the best solution -- not clear which ones, some say aviation ...

Maybe, lithium, hydrogen and other future types of batteries (e.g. solid state) or energy storage methods will coexist in the future in order to allow for a complete transition to renewable energy. However, hopefully, the technology leading the transition will be determined only by technical and environmental reasons ...


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