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PostPosted: Sat Mar 07, 2009 5:32 am
by Suffering_Peon
How much yield would one expect for a PBR of a given size? Is there any rough estimate of the amount of biodiesel output vs exposed area (i.e. 1 gallon per X sq ft?)? What are the rough dimensions for a PBR that can eventually yield 1 gallon of oil?


Re: Yield?

PostPosted: Sat Mar 07, 2009 9:19 am
by DR Johansen
Suffering_Peon wrote:How much yield would one expect for a PBR of a given size? Is there any rough estimate of the amount of biodiesel output vs exposed area (i.e. 1 gallon per X sq ft?)? What are the rough dimensions for a PBR that can eventually yield 1 gallon of oil?

You should be able to estimate a range by assuming the efficiency of conversion of light energy to bio-mass is between about 2% (normal) and 10% (REALLY good).

Re: Yield?

PostPosted: Wed Mar 25, 2009 3:37 am
by AlgaeMan
That's not good news! I was considering using Solar Panels and a Wind Generator to provide clean energy to power my pumps for my Algacultrue.

BUT if you are correct, the energy I get directly from the solar panels and wind generator is best used directly to power my home or charge my electric car batteries. Why bother with Algae at all, if it results in a net loss of energy?

Something is missing - why are we harvesting so little energy from the algae? Is not the process of photosynthesis giving us enough chemical energy (sugars, carbohydrates, lipids) within each algae cell?

If my solar cells are more efficient, why should I burn algae-derived biodiesel if I am getting less net energy? Where is the algal payoff? Is it still hidden within the complex chemistry, and we just don't have the tech to get at it yet?

Re: Yield?

PostPosted: Wed Mar 25, 2009 6:24 am
by DR Johansen
If you want electricity, by all means, use your solar cells and wind turbine directly! But until battery technology is several times better than it is now, folks will still want transportation fuels, liquid fuels, fuels like algaeoleum.

And remember, getting a square mile of solar cells is bloody expensive. A square mile of algae bloom in the ocean is a drop in the bucket and there for FREE. Well, free except for harvest... costs. Automatic sailing trawlers anyone?

Re: Yield?

PostPosted: Wed Mar 25, 2009 7:18 pm
by worrallj
There are a few reasons to use algae instead of solar panels. As stated above, solar panels are a lot more expensive, and this is probably the biggest count against them. Also, solar cells take a lot of energy to produce, and it takes (roughly) 2 years for the cell to reach the "break even" point: The initial energy input of algae is (depending on your set up) pretty trivial. Of course you do have to spend energy drying and pressing the algae. But my understanding is that there isn't this long wait for the energy to be made back - you start getting returns immediately. Also, electricity is harder to store than energy stored in algae cells. Batteries are expensive and degrade, a tank of oil can last pretty much for ever and is cheaper.

Re: Yield?

PostPosted: Wed Mar 25, 2009 9:42 pm
by AlgaeMan
There is another possibility!

If I could find local buyers for Algal Oil, and if the price were decent, I could do it!

If I could find local buyers for Algal Livestock Feed, I could do it!

But it occurs to me, those that need those products could pretty easily make it themselves... hmmm...

The search for the profitable path continues...

Re: Yield?

PostPosted: Fri Mar 27, 2009 3:52 am
by tehol
I find the concept of his point to be valid though.

If we are too look at algae fuel from an environmental perspective, then you want the energy costs of converting algae into fuel to be less than the energy you get from burning the fuel PLUS the energy stolen from the sunlight.

As in the algae to fuel energy cost is x, burning the fuel is y, and energy gained by the algae from the sun is z, and:

x< y+z.

The reason we need this to be true, is that without it, we are continually expending more energy (which comes from burning more oil) than we can produce.

We would be running an energy deficit, similar to what we are doing now. We are burning our oil reserves, from within the earth, faster than the world can produce more.

tl;dr: Is the energy gained by the algae, from the sun, added to the energy gained from burning fuel made from algae, greater than the amount of energy it takes to make algae fuel?

Re: Yield?

PostPosted: Sat Apr 11, 2009 8:40 pm
by AlgaeMan
The model. albeit attractive, suggests that a comparison between two energy producting facilities is in order. This can either be done using measured data from existing plants or hypothetically if we can get reasonably good estimates.

For example, consider an Algae based facility versus a Solar based plant.

Solar cells take energy and cost to produce, and after about 2 years, have broke even and are producing pure electrical power, ready to consume, at a reletively low cost and for quite a long time. My local panels have a 30 year warranty. Let's also note that the production of panels does release some CO2 into the atmosphere.

After all the mark-ups and installation, and given the absurdly cheap current energy prices, it would take about 8 years to break even for a decent sized Solar Farm. Maintenence costs are fairly low (need to keep them fairly clean is all). IF they are mounted on a roof of some other facility, they don't consume much real estate on their own. Pluses for solar.

Pretty attractive.

An Algae based operation looks a lot more complex. Take the area occupied and consider how much solar power could be collected in that space. Maintenance looks challenging, and includes harvesting efforts. Pumps take energy too. On the plus side, Algae is easy to grow and produce, and abosrbs CO2 from the atmosphere. Huge plus!

With the wet green goo, what do you do? Dry it? That takes time and energy, which cuts directly into the bottom line.

A cheap, fast, continous-process wet extraction method is NEEDED here! Let's assume we got that. Excellent.

Now we have a certain amount of Algal Oil production rate, its total cost, and the total real estate occupied by the operation.

We are still good to go IF we can command a strong price for our Algal Oil, and can sell it directly. Let's assume NOT.

Then, we have to add more time and energy to convert the Algal Oil into Biodiesel. These costs are known, but perhaps a tech breakthrough here will tip the scales in our favor.

Fine. Now, calculate the total rate of energy production we can get from the resulting BioDiesel, and compare to the total energy rate produced by a Solar Farm occupying the same real estate. When the energy from Biodiesel is consumed, the sequestered CO2 is released back into the atmosphere. Darn.

I think those numbers put Algae on some pretty shaky ground, but we need to know more. Also note that Solar cells are slowly becoming cheaper and more efficient along with technology advancements.

Just food for thought. I need coffee... Will my retirement years see me as an Algae Farmer, or a Solar Farm operator? I have to figure something out, eventually.