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I read that a centrifuge uses 48.8% of the total energy consumption during algal biofuel production ( http://www.oilgae.com/blog/2011/08/a-centrifuge-uses-48-8-of-the-total-energy-consumption-during-algal-biofuel-production.html)...that sounds an awful lot of energy…is this estimate correct?
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Industry Professional, Chennai
Cofounder of CleanTick, and keen on making my small contribution to make our world more clean and green.
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A comparative analysis of microalgae
dewatering technologies was conducted through the collaborative efforts of
AVS and a multinational water technologies company. This study compared
the energy cost and dewatering capabilities of a conventional centrifuge with
those of AVS' novel Solid-Liquid Separation (SLS) and Rapid Accumulation &
Concentration (RAC) technologies.
Results of the comparative analysis confirmed that the RAC and
SLS dramatically outperformed the
centrifuge, requiring far less energy to achieve a greater degree of
dewatering with the Scenedesmus
dimorphus and Chlorella sp. algal
species. Even with a lower starting
concentration, the coupled performance of RAC and SLS was 19 times
faster in terms of recovered biomass
than the best centrifuge trial, while
removing 8 times more water from the
algae solution. In terms of process
efficiency, the RAC and SLS are over
83 times more cost-effective than a
centrifuge on a metric ton basis.
The results further validate the SLS' $1.98/ton verses centrifuge at $3400/ton
hear is a clip of the company going to congress http://algaevs.com/newsletters/NL_AVS_Summer2011_Email.pdf
A centrifuge separation costs $3400 per T of algal biomass? Sounds crazy...we need the entire cost of a T of algal biomass to be under $400 for it to make fuel sense...and this is after factoring in the revenues from by-products...
Aliendave the simple explaination of why that won't work is, it takes more energy to split the hydorgen, and oxygen in the water than the hydrogen produces as a fuel. The water also has to be highly acidic, like battery acid to do this.
Here is a link that explains this in detail http://en.wikipedia.org/wiki/Water_splitting
I think you need to be able to write more carefully. Your statement emphisizes the seperation of water into it's elements, creating energy from it, and minimizes the speration of algae, and water. you said that you could use the hydrogen to opertate a gasoline generator, or a fuel cell.
According to your last statement "At 2V DC and .25Amps for 10 hrs once can extract 1.8Kg of algae from water and at around 95% separation. That is .5 watts for 10 hrs. That is 5 watt hours."
If it takes 10 hours to remove 1800 grams of algae from the water, that is a slow process for industrial use. Considering many systems produce up to 3 tons of algae per day.
That is 2,721,554.22 grams of algae.
Base on your formula at "5 watt hours" at that scale it would take 1512 hours to process that much algae. If you scaled up, it would consume 7560 watts in the same 10 hours, to process that much algae, or 756 watts per hour. @ $0.15 per kilowatt that would equal $37.80 a ton.
You said it takes .5 watts of electrical energy 10 hours to convert 1.8 kg of wet algae into dry algae, 5 watt hours total.
which means if you wanted to dry out 3 tons of algae = 2,721,554.22 grams of algae (average daily harvest) @ .5 watts of power input it would take you 15120 hours to accomplish this. divide the 2,721,554.22 by 1800 (1.8 kg) then multiply by 10 hours which gives you how much time it would take you to dry out the algae @ .5 watts.
In order to process the 3 tons of algae in a 10 hour period of time, you would have to increase your power input to 756 watts,(1512 X more algae than your original 1.8 kg .5 watts X 1512=756 watts) which would equal 7560 watt hours to do this. If you divide 7560 by three that gives you power input per ton (2520 watt hour). @ $0.15 per kwh = $3.78.
I screwed up before I didn't covert from watt hours to kwh.
That is still pretty impressive on the cost! $3.78 a ton. The $0.15 per kwh I used is a US average, so it will very depending on where you are.
I want to clear this up.
I didn't have a problem with your idea of harvesting the algae. I have come across a very large amount of people who think, since the system you have mentioned creates hydrogen, and oxygen as a biproduct, they can run the system on that.
The rest of the stuff was not to down grade what you were saying, it was to see what it would take to process large amounts of algae. It looks to me that it would be cost effective.
Hi rcollins, aliendave: fascinating discussion, and to be honest, I am not sure I followed all the calculations...
And I am not sure if I have obtained an answer for my question :-). Would either of you (or anyone else reading this) be knowing how much energy (kWh/dry ton of biomass or kWh/liter of water) a centrifuge uses while doing algae biomass separation? Thanks for your patience
That would be tough to answer, too many variables, how big is the centrifuge? What is the mass at any given moment, you are trying to run through the machine...? An analogy of what you are asking would be. What is the fuel mileage of "a car"?
Lets say a centrifuge required to produce 10 T of dry algae biomass a day. At 1 g/l, this will mean processing 10 million liters per day (about 3 million gallons of water per day).
I dont have an answer on "how big is the centrifuge?", guess that is something the vendor is better equipped to answer. I would request to know what the best centrifuge in the world would cost (capital cost) for processing 3 million gallons of water to separate an approximately 0.1% solid concentration, and what will be the total electricity and other operational expenses per day (for 10 tons of algal biomass)...
Please let me know if these specifications are good enough...
best I can figure is 34 kwh based on seperating the algae and water in a 24 hour day.
Just 34 kWh for 10 T of biomass / 3 million gallons? Sounds too low to me...@15 cents per kWh, that would be just 50 cents per T of biomass...
Or perhaps you meant a 34 kW system running 24 hours a day perhaps, in which case the total would be about 800 kWh and about $12 per T of biomass...sounds more likely...
Please clarify...
You would be moving 2,083 gallons of water per minute. It takes about 45.5 horse power to do this. So you may be right.
Excellent! It is indeed 34 kW. @ 746 W per HP, 45.5 HP comes to 34 kW...
Electricity cost of $12 per T of algal biomass is not a bad number at all...now I need to add any additional operational costs, and then amortized capital costs...this will give me a first level indication of the total levelized costs...
Any idea how much a 34 kW centrifuge would cost?
if it is 800 kwh about $12 a ton that would b $120 a day, and this is 48.8% of the total energy usage?
I have read that you can extract about 200 gallons of oil per ton of algae. That would equal 2000 gallons of oil per day @ 10 tons of algae.
Rounded up to $240 a day for total energy expenses, that would equal $8.33 per gallon.
My system is looking better all the time, once in full production the electical energy expense of my sysem is $0.00.
I have no clue how much it would cost for centrifuge.
You need to read this!
http://www.uscentrifuge.com/decanter-centrifuges.htm
The power consumtion was way way off.
Nice link rcollins...doing a bit of math, a 30 HP centrifuge can do about 70 gallons per minute = 4200 gal/hour, approx 100,000 gallons per day.
Yep, I agree, it is a far cry from the 3 million gal per day that we thought a 34 kW centrifuge could do. Were you referring to a different type of centrifuge. Perhaps the decanter centrifuge referred to here is not the most efficient?
It would take nearly six of the 150 hp centrifuge's at max capacity to do the job.