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Author Topic: Is there an economical way to turn heat into 240v electricity,at usable current?  (Read 4361 times)
julian
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« on: September 10, 2013, 01:24:22 PM »

I have almost unlimited access to glycerol.  When mixed with sawdust this creates a fuel that burns hot and long.  The emissions are comparable to kerosene - ie not great, but no worse.


If i could turn this into electrical energy, id be very happy indeed.

I suspect (but i dont know) that id need so many peltier plates that id end up spending far more than the electricity was worth (im on grid, but want to buy less, rather than export)


Steam seems like an option, but, try as i might, i cant work out what size boiler would be exempt from the costly annual certification.  I suspect too small to be of use.



Most of the electricity in this country is generated from heat.  The fact that i cant work out an economic way to do it with free fuel irritates me! : )


Any ideas?


Thank you,
Julian
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Tiff
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« Reply #1 on: September 10, 2013, 01:34:34 PM »

How about a stirling engine?
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julian
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« Reply #2 on: September 10, 2013, 01:35:20 PM »

Dont they stop the moment there is any load?
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Tiff
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« Reply #3 on: September 10, 2013, 01:48:08 PM »

Dont they stop the moment there is any load?

An LTD one would.

They seem to work ok in the Baxi Ecogen which can output 1.1kW.
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jotec
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« Reply #4 on: September 10, 2013, 04:59:02 PM »

How about a steam engine. Admittedly low efficiency but very quiet and you could reuse the low grade heat in the house?
Dick
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Aiming to reduce dependency on 'mains energy'. Own bio for 40k miles, solar water heating (DIY),  CHP done blog at http://www.dpks.co.uk/CHP/main.htm (not always up to date!)
julian
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« Reply #5 on: September 11, 2013, 02:32:02 PM »

Dick, that is what id like, but i think that the boiler would have to have annual inspections etc. under the pressure vessels act (or whatever its called).

Obviously the mechano engine i had as a kid did not require inspection, so there is a cut-off on size, but, try as i might, i cant work out where that cut-off is.
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Ted
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« Reply #6 on: September 11, 2013, 02:55:44 PM »

I'm not sure you need to worry if you were only doing this as a 'hobby'.  The relevant legislation is The Pressure Equipment Regulations 1999 and The Pressure Systems Safety Regulations 2000.  I think most of the requirements are really for insurance purposes which you may want to have anyway. You don't want to do anything that might invalidate your household insurance, for example.

See http://www.hse.gov.uk/pressure-systems/law.htm and (for model steam engines) http://www.normodeng.org.uk/2012_Test_Code_V12a.pdf
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julian
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« Reply #7 on: September 11, 2013, 03:12:30 PM »

Thank you,

It seems like the limits are 3 litres for the boiler, or ('or', rather than 'and' - so far as i can see?) a pressure of 0.5bar.

Could i get a stable output from a 3l boiler?
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renewablejohn
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« Reply #8 on: September 11, 2013, 05:51:51 PM »

using thermal oil steam evaporators gets around most of the boiler regulations as the thermal oil is not under pressure only the flash steam.
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oliver90owner
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« Reply #9 on: September 11, 2013, 07:57:55 PM »

The most economical way on a small scale  is to burn the fuel in an internal combustion engine, generate electricity and use the waste heat for other duties.

It is called combined heat and power... Wink

Glycerol burns to produce some nasties if not completely  oxidised and how you arrange to get it into a suitable form to use as a liquid for an engine might entail some dilution.

RAB
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julian
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« Reply #10 on: September 11, 2013, 08:11:27 PM »

I doubt that the distillation apparatus that seems to be required in order to burn glycerine in an internal combustion engine is in any way economical for anything other than medium to large scale.  Certainly not the sort of thing i can see myself doing in the garage.
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oliver90owner
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« Reply #11 on: September 11, 2013, 10:02:04 PM »

In that case, give it up as a viable project.  There are minimum practical sizes for all these projects.  If bio-diesel production could avoid the wasteful side-products, they would, by now, be well documented and in use.

RAB
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julian
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« Reply #12 on: September 11, 2013, 10:20:30 PM »

My by products are not wasted at all -

An amount of the glycerol either currently / has / will heat our home / heat our water / cooks our food.

Any excess from this has gone to a commercial plant of someone i know, who splits off the FFAs for reprocessing, and then the purified glycerol is sold on.

To date, the quantity of glycerol that i have produced, that has gone to 'waste' is absolutely and entirely 'zero' - this is over several years of production.


You've first suggested to me a CHP approach which is unfeasible, and then told me i should throw in the towel! 
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renewablejohn
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« Reply #13 on: September 11, 2013, 10:26:57 PM »

At a large scale its quite easy but smaller scale is harder i know of this company who makes steam lab equipment.

http://www.cussons.co.uk/education/Data/Product_Downloads/LAB-5KWSTEAMPLANT.pdf
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DaS Energy
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« Reply #14 on: September 12, 2013, 02:22:45 AM »


Hello Julian,

CO2 remains the most efficient of heat energy, however if the standard Steam engine configuration is to be used it requires construction from Stainless Steel given it high pressures to low heat.

Should you wish to remain at gas throughout then this model is easily home built.

This model will work on any gas. Gasses other than CO2 may provide greater energy however to date we have not worked with such.


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