[Greenbuilding] Northeast Sandy rebuilding

nick pine nick at early.com
Sun Nov 4 15:09:46 CST 2012


This looks nice, for $2475 with electric starting. It's air-cooled and makes 
about 94K Btu/h of heat... 
http://www.generatorsales.com/order/Honda-10kw-Propane-Generator.asp?page=H04590

It could have helped some friends in NJ with natural gas but no  electrical 
power or heat yet, a week after Sandy. Honda engines running on  natural gas 
with regular oil changes should last at least 20K hours,  enabling 
economical full-time cogeneration, if the generators can be grid-excited. 
These generators now have a 5 week lead time.

Water-cooled generators seem to be a lot larger, with more heat than a house 
can use.

I'd unscrew the muffler and pipe the Pi(3.07"/2/12)^2x2.83"/12x3600 = 44 cfm 
exhaust outside, through a hookah, eg a 1"x5' capped copper pipe with 64 
1/8" holes under 1" of water in a 4' square x 2' deep box with a 10'x10' 
EPDM liner and a 1"x300' pressurized plastic pipe to heat water for showers. 
The muffler pipe is 1.25" OD. A 170 F thermostat and a circulation pump 
could keep the box from overheating.

What would it take to recover the rest of the heat indoors and reduce the 
sound output from 74 dB at 7 m to 30 at 1 m?

 Sound levels drop 6 dB with each doubling of distance. Moving 23'x2^8 = 
5888' away from the generator would reduce the sound level to 26 dB :-)

 The generator has a 9" cooling fan. It might move about 94KBtu/h/(120F-70F) 
= 1880 cfm, if the exhaust is 120 F on a 70 F day.

http://www.engineeringtoolbox.com/sound-attenuation-ducts-elbows-d_76.html 
says each 250 mm (9.8") duct elbow with a 1" lining reduces sound by 18 dB, 
so 4 intake and 4 exhaust elbows around a well-insulated 
19.25"x27.25"x20.75" tall box could do a good job.

http://www.freecalc.com/ductfram.htm says 8' of 10"x20" duct with 4 elbows 
would have a 0.103 "H20 friction loss, which seems OK. A rectangular 
horizontal spiral intake duct could  surround the lower part of the 
generator enclosure with a 39.25"x47.25" OD on top of the 4'x4'x2' deep 
tank, with a 4'x4'x2' tall horizontal exhaust  "duct" with 4 elbows and a 
0.072 "H20 pressure drop  above that, in a 4'x4'x5.7'-tall basement package.

Nick 





More information about the Greenbuilding mailing list