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The idea of storing engine heat for longer periods is expensive, difficult and space-consuming, I've tried. Storing a sensible amount of heat energy for 8 hours can be achieved, but the insulation and amount of material to store the heat is not very practical.
In Finland, timer equipped electrical outlets are common in private parking spaces; for using block heater and interior heaters. Two hours of running a average 1.5 kW electric heater in the cabin and a few hundred watt block heater results in a nice, thawed cabin but the engine is still quite cold. The poorly insulated engines lose most of that block heater energy to the air surrounding them.
I had an idea few months ago to use the "lost" energy in a different way. Say you use a 500 W heater to heat the block for 2 hours. That's 500 J/s * 2 * 60 * 60s = 3600 kJ of energy spent. If you spent that energy on heating plain water (specific heat 4,19kJ/kgK) a 10 liter water container could have its temperature go up over 85C, assuming no losses, and keeping under boiling point of course.
This is just theoretical, but maybe it brings into perspective how much energy that is. Heating the engine versus storing heat energy in an insulated container for quick energy transfer when actually needed.
The problem? The same as with the original heat storage idea: space and weight. Electric heating has it's advantages though, you're not bound by the engines maximum temperature of around 100 C. You could use other materials and liquids to store energy at higher temperatures. Heat wax to 200C, and make the container smaller. Going high temperature with flammable materials brings issues of burning the car down. Maybe a "pressure cooker"? At 20 bar, water boils at over 200 C too. An old fire extinguisher insulated and fitted with a copper coil and a heater?
This is where I'm now. Any ideas from you guys?
Installing a fuel heater was an option, and they are very common in diesel engines in the northern countries. Still it's not that "DIY", and prices for such systems are upwards of 500 euros, even used. Any research on fuel used for heating vs. saved fuel, other than fuel heater manufacturers own?
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