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If I recycle the waste heat emitted by a Mcdonald's, can a well-placed Mcdonald's take the place of a community heating boiler?

George Chen
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    The heat emitted is a fairly low temperature. – paparazzo Aug 22 '18 at 19:36
  • Is the McDonald's going to be inside another building? What size and type of building? Some of the waste heat from kitchens can be recovered, but typically not enough to replace heating systems -- only to supplement. A big problem is that the hot exhaust air is also smoky. – LShaver Aug 22 '18 at 19:45
  • @paparazzo - 60℃ is enough for community heating. One can even recycle heat from lukewarm sources using heat pump. Burning fossil fuel can get to hundreds of degrees, which is an overkill and a huge waste for community heating. – George Chen Aug 22 '18 at 20:26
  • @LShaver - Since McDonalds' are already throwing away waste heat, they can recycle it and sell it back to the community. They can use small furnaces to burn their wast oil in place and sell the BTUs to their neighbours. – George Chen Aug 22 '18 at 20:29
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    If you feel you know the answer then why did you ask the question? – paparazzo Aug 22 '18 at 22:44
  • @paparazzo - I need a number from a real example so that I can ballpark the order of magnitude. – George Chen Aug 22 '18 at 23:33
  • You can use your fridge as a space heater. Put a pound of room temperature water in your fridge and freeze it to 0 F, you'll get way over 70 BTUs. Since water releases heat when changed to ice, you'll get a lot more heat. – George Chen Aug 23 '18 at 05:15
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    @paparazzo and GeorgeChen: Please keep the discussion civil. There is no need to question each other's education. – THelper Aug 23 '18 at 07:41

1 Answers1

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The bulk of the waste heat in a fast food joint ends up either warming air, or evaporating water.

Grills and fryers always have a vent above them, drawing air at a considerable rate. The one industrial kitchen I worked in had a 3 HP fan over the stove, grill and fryer. This ventilation is necessary to keep the grease and smoke from cooking from filling the kitchen with fog, and to keep from cooking the cooks.

Ours had fire detectors set at 140 F -- 60 C. If you got that hot, everything was covered in a foot of foam, and you were closed down until everything was cleaned up. Never saw it happen. So I assume that temps in the hood were well below that.

But to answer your question. Wild A** Guesses here:

  • Industrial fryer 20 kW. Probably have 4 units, with one being in use the entire open time, and the other 3 having various amounts of time depending on traffic.

  • Grill 20 kW each. Probably 2 of them in place.

  • Heated food tables. 2 kW per shelf? 4 shelves.

  • Walk in cooler and freezer 10 kW?

I'm guessing they would have a 250 kW service, and would average somewhere between 70 KW and 150 kW for open times. If that's 18 hours a day at 100 kW that would be 1800 kWh/day.

Sherwood Botsford
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