Some Danish houses don't get natural gas or oil for heating water or rooms. They get hot water to the house and use a heat exchanger. The hot water isn't boiling hot, so the heat exchanger will transfer heat from one batch of hot water to heat further the hot water. They are charged on temperature difference between the input hot water and the colder water returned to the city. The temperature monitor is
In my hosts particular case, the heat is originally generated by coal generators.
I was totally blown away. I'd never heard of or even thought about heat exchangers from town centralized water heating as a way of distributing energy.
To prevent abuse or tampering, my guess is that if there is less cold water returned than hot, they charge assuming maximum heat usage. This prevents them from just receiving hot water and dumping cold water into wherever.
I wonder about the efficiency of transferring hot water instead of electricity. I know that electricity can be really inefficient, with up to 50% transfer loss. Imagining a coal plant that heats water, then converts to electricity, then heats water in the home, it seems like the water exchange idea might be really efficient.
Comments (2)
Nice isn't it?
You made me blog about this too: http://ijesper.blogs.com/weblog/2005/06/hot_water_grid_.html
Here's the really cool thing about the hot water system in Denmark: The hot water is a by-product of electricity generation. When the steam has been through the turbines in a powerplant, the heat of the steam is transferred in a heat exchanger to the hot water system that heats the houses. So it's not matter of whether its more efficient to use coal to make heat or electricity. Our coal plants produce both heat and electricity.
Posted by Jesper Joergensen | June 3, 2005 11:19 AM
Posted on June 3, 2005 11:19
The next obvious question is: what about cogen opportunities? If I pass the output through, oh, say, my bed at night when the wife is feeling frisky, could I get a reduction in the charge? What if the water comes out hotter? I wonder if I can get gerbils to spin a compressor to run a Hilsch Vortex Tube. The mind boggles.
Posted by Robert Laing | June 7, 2005 8:22 PM
Posted on June 7, 2005 20:22