My journey to Liverpool from Oxfordshire set me thinking. How much waste heat did my journey expel to the atmosphere, and could it be trapped and used?
My cunning plan involves using the waste engine heat to warm a medium in a tank - perhaps a saline solution, which on return home is then plugged into the hot water circuit of the domestic plumbing and has the heat extracted from it.
Clearly the issues include: safety, cost/return on investment, weight (and fuel penalty) as well as the space taken up, and a host of others I've yet to think of.
Anyone care to think about it and provide a serious critique?
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You could get into a pickle using brine........;)
Regards;);)
Edited by oilrag on 27/05/2008 at 10:50
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would'nt a denser medium like oil be able to store more of the heat energy, like in those oil filled electric radiators? or what about using the engines heat and converting it directly into electricity using a bi-metal gizmo and feeding it straight into the battery saving the alternator or doing away with it even?
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Perhaps the best thing would be to attempt to use the waste heat to help drive the car (reducing the fuel consumption), so it doesn't have to be stored and carried home?
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I think that you would need a very large tank to store the heat energy, any savings gained from the heat would be lost due to decreased mpg.
You could look into heat engines - the stirling engine in particular. A stirling engine could be powered by the heat from the exhuast and drive an electric generator - the electricity could then be used to supplement the cars engine or stored in a battery to take home.
Edited by moonshine {P} on 27/05/2008 at 11:15
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If you use the heat to heat up something it will have to have a good heat capacity and be insulated, I suspect you need 10's of kgs or more of it, so will contribute to fuel demand (ie higher mpg). You need to connect to the existing cooling system somehow. 10's of hours of your time and you'd have to lug a 20kg+ box in and out of the house? BUT very cheap otherwise.
You car would generate more than enough waste heat, even if only 30% of the heat went out through the coolling system, assume your car is generating 20 - 50 KW on an average run, an hours drive is giving you 6 KWH of waste heat (minus what is used to heat the cabin). I think these numbers are probably a conservative estimate as well.
The other option is to convert it to power ie. store in as electrical power in a second battery - but you would need to have some sort of computer management of the charging system, connecting a second (discharged) battery directly may overload or strain the alternator. Perhaps if it only came on when you were going down hill? But this is not recovering the waste heat.
My suggestion is to use a small stirling type motor using the radiator's heat to power a small 12 v generator topping up a spare battery. I think some car makers (Hybrids) may be looking at this technology already to top up hybrid batteries. But standard car Batteries may only hold 0.5 - 2 KWH, enough to heat one room for 1 - 2 hours. High initial cost but lightweight and effective, especially if you invest in Hybrid type batteries.
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Admirable though it is, I can't help wondering (even if all the practicalities were worked out) how much exta energy you'll use lugging the extra weight (esp. of the liquid) around.
If it helps - I already do this partially (by default) inasmuchas my car is parked in the integral garage where the CH boiler & water pipes are. My warm car raises the garage temp. considerably & keeps it warm for several hours. This heat warms the coldwater pipes, the garage & adjoining kitchen & bedroom above - it also lessens the loss when the boiler is on since the heat gradient is less. The car also benefits since it's almost always warm (or not cold) when starting.
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When I put the E-type away in our garage, I can tell you it's warm as toast in there for the rest of the day, I often leave the door open to warm up the utility room too.
MVP
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Yes these last two posts were my first thought. If you get an especially well insuated garage door for integral garage, then that is probably the most effective way of transferring heat from the car to the house, simply by radiation.
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