Hot water heat
Hot water heat recovery sytems (also known as drain water heat recovery, greywater heat recovery, or sometimes shower water heat recovery) is the use of heat exchanger technology to recover and reuse hot water heat from various activities such as dishwashing, clothes washing and especially showers. The technology is used to reduce primary energy consumption for domestic water heating while also reducing greenhouse gases. Standard units save up to 60% of the heat energy that is otherwise lost down the drain when using the shower.
Consider for a moment how truly in-efficient energy is used when it comes to domestic water heating. A dishwashing machine uses and maintains water at temperatures as high as 65°C and at the end of each cycle all of this heat energy is thrown away. The shower is even worse because hot water is used only a few, brief seconds before it is thrown away with 90% of the heat energy still held by the drainwater.
Here’s how it works
As warm/hot drain water flows down the vertical heat exchanger it clings to the surface of the inner section forming a very thin film of water. This thin water film allows for ultra-high heat transfer. Heat that was normally wasted now instead is rapidly absorbed by cold water flowing through the outer section.
The preheated freshwater exiting the heat exchanger then proceeds to the conventional water heater. This preheating of the water before it enters the water heater substantially reduces the energy/fuel used by any water heating system.
How much do you save?
For residential systems, the most accurate claim is that the savings on water heating ranges from 25% to 40%, depending upon a number of factors including efficiency of unit, how the freshwater is plumbed and water use habits. For commercial and industrial systems, savings can be up to 80% with short payback periods.