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So, throwing in a factor of 1/2 for latitude and a factor of 1/2 for weather you get 250 Kcal per year per square metre, or 2.5e6 Kcal per year per hectare. At 8% efficiency, that is 2e5 Kcal per year per hectare. That's about 8.4e5 KJ per year per hectare. For comparison, the energy density of diesel fuel is 11 KWh per litre, or approximately 4e4 KJ/l. So, a hectare of chlorella can at most produce the equivalent of 21 litres of diesel fuel per year.

I could easily be off by a factor of 1000 because of sloppy use of units, but otherwise this is a no-go.

We have met the enemy, and it is us — Pogo

by Migeru (migeru at eurotrib dot com) on Thu Oct 25th, 2007 at 05:31:37 AM EST
[ Parent ]
Biofuels & Petro-fuels = Liquid Fuels (Part Two) by afew on July 13th, 2006, has lots of data on first-generation biofuel yields. (3000 litres per hectare seems like a sensible estimate - I must be off by a few zeroes in my estimate for algae).

We have met the enemy, and it is us — Pogo
by Migeru (migeru at eurotrib dot com) on Thu Oct 25th, 2007 at 05:53:14 AM EST
[ Parent ]
Using incident solar power numbers from wikipedia, puts Europe at something like 150W/m^2 average for the year.

At 8% conversion efficiency:
150*0.8*365*24*60*60 = 378,432,000 J/(year*m^2)
For disel, 11kWh/L = 11000*60*60 = 39,600,000 J/L
So, per square metre disel equivalent yield per year:
378,432,000/39,600,000=9.6L/(year*m^2)
or 96,000L/(year*hectare)[sounds like a lot more than 3000. Do I have an extra zero??]

The EU used 494616 kTOE in 2005
In joules: 494616*1000*42e9 = 2.0774e19 J
Which, converted to diesel litres is: 5.2459e11 L
Per percent replacement: 5.4645e8 m^2
or 54645 hectares per percent replacement of 2005 fossil fuel usage.

by someone (s0me1smail(a)gmail(d)com) on Thu Oct 25th, 2007 at 06:43:05 AM EST
[ Parent ]
I think either kcurie's solar energy figure or my interpretation of it were off by a factor of 1000, which is not entirely surprising given the ambiguity in the meaning of the word "calorie".

Calorie - Wikipedia, the free encyclopedia

The calorie was never an SI unit. Modern definitions for calorie fall into 3 classes:

  • The small calorie or gram calorie approximates the energy needed to increase the temperature of 1 gram of water by 1 °C. This is about 4.184 joules.
  • The large calorie or kilogram calorie approximates the energy needed to increase the temperature of 1 kg of water by 1 °C. This is about 4.184 kJ, and exactly 1000 small calories.
  • The megacalorie or ton calorie[citation needed] approximates the energy needed to increase the temperature of 1 tonne of water by 1 °C. This is about 4.184 MJ, and exactly 1000 large calories.
Did I tell you I like TribExt?

We have met the enemy, and it is us — Pogo
by Migeru (migeru at eurotrib dot com) on Thu Oct 25th, 2007 at 06:12:08 PM EST
[ Parent ]

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