<div class="gmail_quote">On Sat, Jan 7, 2012 at 07:49, Robert Kana <span dir="ltr"><<a href="mailto:sinan@biomassindo.com">sinan@biomassindo.com</a>></span> wrote:<br><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">
<div id=":28g">We need some help calculating the amount of fuel needed to generate enough power for 160 Kwe every hour. Suggestions are welcomed.<br></div></blockquote></div><div><br></div>Are you looking for an approximate quantity (so you know how big to build your gasifier)? That's pretty straightforward (to get an estimate within say +/-15%).<div>
<br></div><div>If all you need is a rough estimate, mine is that you'll need 160-240 kg/hour of fuel input, with 190kg/hour being my best first guess.</div><div><div><br></div><div><br></div><div>***** some detail on how to do the calculations yourself, better.<br>
<div><br></div><div>You need to know your overall system efficiency (electricity output per unit of fuel energy input), then you multiply that by 160kW (your electrical power output).</div><div><br></div><div>Your overall system efficiency is the product of three subsystems:</div>
<div>- gasifier</div><div>- engine</div><div>- generator</div><div><br></div><div>A conventional gasifier might have a 70% "cold gas efficiency" (which means the fuel energy of its cooled, ready-to-use output gas, divided by the fuel energy of its input feed).</div>
<div><br></div><div>A typical small spark ignition engine might give 20% efficiency (shaft power out divided by fel energy in). But there could be quite a big range here, this figure could easily be 15%-30% so the best idea is to lookup the data of that engine and find out the manufacturer's ratings (if they give a specific fuel consumption "sfc" for natural gas or gasoline/petrol, you can convert that).</div>
<div><br></div><div>Electrical generators are pretty efficient. For this calculation let's use 90% (but for better results, look up the specs on the generator you are using).</div><div><br></div><div>Now we can calculate your overall system efficiency:</div>
<div><br></div><div>OverallEfficiency = GasifierColdGassEfficiency * EngineEfficiency * GeneratorEfficieny</div><div>OverallEfficiency = 70% * 20% * 90%</div><div>OverallEfficiency = 12.6%</div><div><br></div><div>The final thing you need to know is then energy content of your input fuel. You know your fuel better than I do but I will assume that it is "standard wood":</div>
<div><br></div><div>InputFuelEnergyContent = 20,000,000 Joules / kg (in Imperial units 8612 BTU/lb)</div><div><br></div><div>You want your generator to produce 160kWe. This is 160,000 Watts of electrical power output, which is 160,000 Joules / second.</div>
<div><br></div><div>Because your overall efficiency is 12.6%, to get 160,000 Watts out you will need to feed:</div><div><br></div><div>FuelInputRate(power) = OutputPower / OverallEfficiency</div><div>FuelInputRate(power) = 160000 Watts / 0.126</div>
<div><div>FuelInputRate(power) = 160000 Watts / 0.126</div></div><div><div><div>FuelInputRate(power) = 1,269,841 Watts</div></div></div><div><br></div><div>So you need 1269841 Watts (which is Joules/ sec) of fuel input. How much is that?</div>
<div><br></div><div><div><div><div><div><div>FuelInputRate(massflow) = FuelInputRate(power) /InputFuelEnergyContent</div><div><div>FuelInputRate(massflow) =1,269,841 Joules/sec / 20,000,000 Joules / kg</div></div></div>
</div></div></div></div><div><div><div><div><div><div><div><div>FuelInputRate(massflow) =1,269,841 Joules/sec / 20,000,000 Joules / kg</div></div></div></div></div></div></div></div><div>FuelInputRate(massflow) = 0.0634921 kg/sec</div>
<div><br></div><div>If you want an hourly rate, multiply it by one hour (which is 3600 seconds/hour):</div><div><br></div><div><div>FuelInputRate(massflow) = 0.0634921 kg/sec * 3600 sec/hr</div></div><div><div><div>FuelInputRate(massflow) = 230 kg/hour</div>
</div></div><div><br></div><div>So my estimate is that you will need 230 kg/hour fuel input in order to produce 160 kWe</div><div><br></div><div>(this is a system end-to-end Specific Fuel Consumption of 1.4 kg wood per kWh of electricity output)</div>
<div><br></div><div>The accuracy of this calculated result depends directly on the accuracy of the input data. If your engine actually has 28% efficiency rather than the 20% I assumed/used in my calculation, your fuel consumption will be 20/28= 71% of what I've calced (so that would be 160kg/hour).</div>
<div><br></div><div><br></div><div><div>-- <br>- Daniel<br>Fredericton, NB Canada<br>
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