Sunday, April 20, 2014

Living in the Material World

Let's make a comparison on the amount of "material" that is needed by two different electricity production sources.

First, let's start with nuclear. According to the MIT study referenced below, 200 tons of natural uranium (in other words, as it comes out of the mine) produce 1 GWe for a full year.

To convert this to GWh, we multiply 1GWe x 365 days x 24 hours = 8,760 GWh.

To scale this down to a more manageable amount we'll calculate the electricity production per ton of natural uranium:

     8,760 GWh / 200 = 43.8 GWh.

Now, let's estimate how much material is required to produce this same amount of electrical energy with solar photo-voltaic panels.

Searching in Amazon, I found 250 Watt solar panels that weight 19 kgs (sure, other models may weight less or more). We'll use these panels in our exercise, considering they have a useful life of 25 years. Also, we'll be optimistic and consider a capacity factor of 20% during the useful life of the panels.

One 250 W panel would then produce:

     250 W x 20% (capacity factor) x 24 hours x 365 days x 25 years = 10.95 MWh.

How many panels would be required to produce 43.8 GWh?

That would be:

     (43.8 GWh x 1000) / 10.95 MWh = 4,000 panels.

If as stated above, each panel weights 19 kilograms, the total weight would be:

     19 kgs. x 4,000 = 76,000 kgs. or 76 metric tons.

So, in summary, one ton of uranium would produce approximately as much as 76 tons of solar panels.

1. The above calculations do not include the material used to build the actual nuclear reactor nor does it include the material required for the solar inverters. Also, for simplicity, the inefficiency of the inverters is not considered above.
2. Sure, it could be argued that at the end of its useful life the material in the solar panels can be recycled, but still the difference in material utilization is significant.
3. Other nuclear technologies in the drawing board could require less material to produce the same amount of electricity.
4. Fell free to make your own calculations and share your results if they are significantly different from the ones presented here.


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