Consider how many people park a hot car when they get home and then go immediately cook food. The heat energy in the engine block is wasted as they burn more energy on the stovetop. So why not design engine blocks with a flat cast iron topside that can give a good heat transfer to a skillet or copper pot? If it would bring water to a near boil, that’s tea water, or perhaps a start on cooking.
I recall an Australian steak house that would bring a raw bloody steak to your table along with a flat lava rock so screaming hot that you could cook your own steak as completely as you want. So of course I’m thinking: why not transfer this idea to engine blocks? The lava rock is somehow fastened onto your engine block, and when you park you bring the hot rock into the kitchen for cooking heat.
Of course we must factor in the payload weight added to the car as it moves. So carrying the rock might be foolish in a cross-country trip but perhaps efficient on commutes exactly long enough to get recoverable heat energy. In the winter, the rock could be put into the air ducts of a forced-air heating system and add warmth to the house.
Could be rediculous ideas here.. but I guess the job of thought_forge is to sort that out.
I know it was already studied to transfer ICE¹ heat to a steam engine to continuously convert (otherwise wasted) heat energy into more power to the drivetrain. Superficially it sounds brilliant, but apparently the complexity of the whole system was found to outweigh the benefits. I.e. many more things can go wrong with the car. But what if the steam engine does not directly complicate any essential car functions? Instead, it could generate power that charges the battery instead of the alternator. If it breaks down, it’s just the charging system. A switch simply puts the alternator back in the loop. Or it could mechanically power fans that blow heat into the cabin.
¹ internal combustion engine
Your particular idea is kinda silly because cars are usually outside, and they are dirty. But on an ideal world, no energy would be wasted in the home. The future home would have a central heat pump that would suck residual heat from the fridge compressor, as well as from the stove and oven after you turn them off. This heat would then be used to heat up water. The hot water drained from the shower could also be recaptured. Also, in the winter, the fridge "coldness" should just be coming from outside instead of using a compressor that produces lots of waste heat.
That's what tinfoil is for. In fact it's not unheard of for people using the engine block to cook food, or even the dashboard. It's not too common and what you can cook is a little limited, but it's not unheard of