Half a croissant, on a plate, with a sign in front of it saying '50c'
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Thermal busbar

Like a ring-main for heat.
  [vote for,

When new houses are built in temperate regions like the UK, they can be insulated enough to effectively not need heating. However, heating is still required for hot water, cooking etc. Meanwhile, cooling is still required for refrigeration.

With lower heat energy requirements, it almost becomes a waste to be connected to the gas supply. Why not save the standing charge and just use electricity? Of course, electricity is more expensive than gas per joule. However, electricity can be used much more efficiently to transfer heat from one place to another. This is how refrigeration works. For heating the process needs a supply of low-grade heat, while for cooling the process needs a way of disposing of the surplus, that is, a heat-sink.

A heat pipe is a way of redistributing heat, but in this case more for cooling to the environmental level, i.e. as a heat-sink. Basically a liquid pools at the bottom where it is heated by some source of waste heat, evaporates and condenses at the top due to cooling by the environment or some heat sink.

I propose that a house be built around an enormous heat-pipe. This would have large, reliable heat sources at the bottom, large, reliable heat sinks at the top, and the potential for intermittent or smaller sinks and sources in-between.

Heat sources include : refrigeration, cooling of cooking areas, cooling of waste water before efflux, solar heating etc. During very cold spells a fall-back source of heat would be required. This could be either or both of a fuel burner of some description or an electric heater.

Heat sinks include : hot water production (separately, both washing and drinking water), room heating units etc.
Some devices only need to 'borrow' heat for a short time - for example tumble-driers.

For the non-integrated heating/cooling units, a standard interface to the system is required. This would probably involve a flat metal plate in the wall, to which the device can be attached. Internal to the heat pipe, there is at the very least a small reservoir which collects liquid flowing down from above (for heating devices), and a condensation surface - perhaps a thin blade (for cooling devices).
When not in use, an interface is covered by a block of thermal insulation.

In areas where many devices are desirable, a horizontal branch from the vertical trunk can be made. This has a low lip at the junction, so all devices on the branch can share a fluid reservoir. Baffles on the inside of the trunk direct falling liquid into each branch (and any inline connections) in turn.

This means that heat can now be efficiently shared by the devices in your house. Waste heat is easily disposed of, and free heat acquired by the things which need it.

Loris, Mar 18 2010

Bar Bus Bar_20Bus
Not quite the same thing, and unfortunately lacking [bz]'s fine illustration. [jurist, Mar 19 2010]

Heat pipe wikipedia article http://en.wikipedia.org/wiki/Heat_pipe
But hang on... just what is a heat pipe? [Loris, Mar 28 2010]


       That's ... rather well thought out actually [+]
BunsenHoneydew, Mar 18 2010

       This idea would only have been better if it had more closely resembled [stephee]'s Bus Bar idea for commuters with nicer air conditioning and which was so brilliantly illustrated by [bristolz]. Oh, that was a "Bar Bus".<see link> ...Regardless, nicely presented.
jurist, Mar 19 2010

       the only downside I can see is that certain devices could have to work a lot harder (less efficient) depending on the temperature of the busbar. For example, if the bus is hotter than room temp then your fridge would be better off not using it. If it was colder than room temp then the fridge would only have to work 1/2 as hard but then other heating devices would not benefit. Using it purely one way or the other would be better.. like if it was a heatsink for everything, and al of hte heat went into pre-heating water going to the hot water tank or something of that sort. Because the bus would almost always be colder than room temp it would be a great heatsink for electronics, fridge, AC unit, etc. Just not for heating.
AutoMcDonough, Mar 19 2010

       AutoMcDonough, I think you're wrong in a couple of ways.   

       Least importantly, You can't use it "purely one way or the other". You need to both put heat in and take it out. Indeed, you then go on to say that you need a large reliable heat sink like hot water - which is in fact how I described it in the idea; somehow you missed that.   

       But more importantly, I think you've mis-interpreted how devices would work:   

       //the only downside I can see is that certain devices could have to work a lot harder (less efficient) depending on the temperature of the busbar. For example, if the bus is hotter than room temp then your fridge would be better off not using it. If it was colder than room temp then the fridge would only have to work 1/2 as hard but then other heating devices would not benefit.//   

       In a sense this might be true. Some devices might have to work harder than without a thermal busbar.
But overall, and using the physics sense of work, this is not the case. This is because some of the devices would be working in a different way. At the moment many electrical heating devices produce heat purely resistively. Like for example an electric kettle. If at least some of this heat can be gathered from elsewhere then less energy needs to be input. And as a bonus, this work contributes to the heating, too - there's no downside.

       Now you mention the fridge having to work harder if the busbar is hotter than the room. Now that may be the case (although it is counterbalanced by other devices working less hard, as I just mentioned). However, it may actually not be the case. If a fridge or freezer dumps heat into the room it is in, it can potentially re-enter the cold compartment by conduction etc. This can lead to a vicious cycle, with the freezer working harder and harder at expelling heat that it itself is generating. If the heat is instead moved away from the device, this can't happen.   

       It is important to appreciate that the thermal busbar is not acting as a large thermal store in itself. It only expedites the transfer of heat between devices. If the house were consistently too hot, it could help to dump heat efficiently. If the house were consistently too cold, it would provide a good distribution mechanism, so a potentially more efficient, larger heat source could be used. But unless the house is effectively insulated I don't think it would make much difference percentage-wise to the energy used - the real advantage comes from redistributing preexisting heat.
Loris, Mar 27 2010

       //Why can't we use a metal bar and replace all this plumbing?//   

       I suppose you could, but it wouldn't work as well. Heat pipes transfer heat much more effectively than metal conducts.
To put this in perspective, the Wikipedia article mentions that overheated copper heatpipes (in which all the fluid is evaporated) will conduct heat at 1/80th of their 'active' rate. Another article claims "effective thermal conductivity many thousands of times that of copper".
Plus it would be more expensive, since you'd be using much more copper.
Loris, Mar 28 2010


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