Geothermal water heater by hal

Very interesting idea, seems to have great potential. I wonder why the focus is on extracting energy from the cold water. There is probably more waste energy in the waste water from the showers and laundry washers. Also, in cooler climates (like in the North-East for example), the tap water is pretty cold already. Highly efficient HVAC systems include heat recovery wheels, that extract heat from the exhaust air and use it to warm up the intake air. Perhaps if you could develop a similar system to extract energy from domestic waste water, it would be viable in colder climates as well. Cheers !..

The same method i mentioned above might be used to generate electricity both from the waterflow while showering and the drainage of water. the question would be if the amount of power generated was sufficient to justify the process.

I think waste heat reclamation from drain lines is very much a current reality, although a kind of long payback item in it's current form. To Gunesh's point, we sometimes neglect to factor in the embodied energy of systems (especially solar panels, side point) As we evaluate new process maybe we should develop simple LCA or EPD metrics. I see all waste heat and heat pump systems as a form of conservation...and in that sense micro turbines that capture energy from any flow make great sense, if costs are manageable.

Saravanan, Before addressing your comments, I will answer the questions about heat recovery. There are quite a few mature system designs used to recapture heat from drain waste. In very cold climates, it seems to work but has generally not caught on due to the low delta-T for the heat exchange v. the high cost of copper components. Now your questions 1. I call it geothermal because the heat extracted comes from the ground in which the supply lines are buried though an argument could be made that this is solar energy. 2. Any electric source will do, with an EF of 4.0 it only uses 25% of the energy of a standard electric water heater, though PV is best. 3. I am not sure what you mean by pilot project. The system prototypes were tested in a lab at UC San Diego and in homes in various climate zones. The unit should cost about the same as any heat pump water heater. 4. As noted, the EF of 4.0 represents a 75% savings over conventional electric water heating. Powered by 100% coal (worst case scenario) a family of four creates 4400 lbs of CO2 per year heating water. That would be 3,300 lbs of CO2 per year per unit saved. 5. Solar water heating is actually more complex and problematic (see http://www.halslater.com/Solar-Hot-Water.htm ) and costs about three times as much for a comparable system with a 75% solar fraction. Thank you all for your comments and questions. Keep them coming.