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[ddrueding]

At our place and in most of the cities in Denmark we get hot and cold water from the city. The water traditionally has been heated by burning waste, but as there is less waste these days some cities are implementing massive building-sized heat pumps to heat the water. Once the hot water reaches your house or apartment you use water-water heat exchangers to pull the heat from the city water and heat your underfloor heating and any hot water requirements. That is why I didn't do anything like that for my place.

And I haven't done anything with my PC yet, as we aren't sure where we'll end up. Current visa is good for another 3 months, working on options.

My friend lives in the country, and still has an independant heat pump water heater. The heat pump units are way more energy efficient than the tankless units, but take a longer time to heat the water, so still need tanks.

The heat pump tech is pretty cool.

 

[jtr1962]

I'm surprised they don't use tankless water heaters in Europe.

I looked into that first for the kitchen sink. They have ludicrous power requirements, starting at well over 5 kilowatts. That doesn't even get you a great flow rate. If your incoming water is 40°F (typical in NYC winters) and your outgoing is 110°F, 5 kW only gives you ~0.5 gpm, maybe twice that with summer water temps. OK to wash your hands, maybe clean lightly soiled dishes, but that's about it. To get enough for washing dirty pans and stuff you're probably talking 15 kW or more. For showering ( 30 to 60 gpm ) you get well into the 100 kW to 200 kW area. Granted, a tankless system using heat pumps instead of resistance heating can cut these numbers by a factor of 3 or 4, but in most cases you're still looking at installing a 240VAC circuit.

Tankless water heaters with batteries might be an idea. For every minute of hot water at 1 gpm you would need around 100 to 200 W-hrs of battery capacity, depending upon incoming water temperature. Not sure if the cost/benefit ratio would pan out but at least you could use a 120VAC, 15A circuit.

 

[jtr1962]

At our place and in most of the cities in Denmark we get hot and cold water from the city. The water traditionally has been heated by burning waste, but as there is less waste these days some cities are implementing massive building-sized heat pumps to heat the water. Once the hot water reaches your house or apartment you use water-water heat exchangers to pull the heat from the city water and heat your underfloor heating and any hot water requirements. That is why I didn't do anything like that for my place.

And I haven't done anything with my PC yet, as we aren't sure where we'll end up. Current visa is good for another 3 months, working on options.

My friend lives in the country, and still has an independant heat pump water heater. The heat pump units are way more energy efficient than the tankless units, but take a longer time to heat the water, so still need tanks.

The heat pump tech is pretty cool.

Sounds like a much better idea than every home having a furnace and hot water heater. Are there any heat exchangers to recover some heat from wastewater? In theory if you could recover most of the heat once you "prime" with some hot water to get things started you would need to add very little additional heat to maintain a continuous flow of hot water.

Heat pump hot water heaters are catching on in the states, but for now gas or oil or resistance heating is still far more common.

 

[LunarMist]

Of course we are now totally off of the topic, but I meant like the Natural Gasses. Electric tankless is good for a sink or something.

 

[ddrueding]

We are totally off topic, but to answer JTRs question, the hot water from the city is an isolated closed-loop system. You control the flow rate of it through the heat exchangers at your place to heat your own water to your desired temperature. The city hot water is supplied at 80C+ and they want you to return it at 40C- to maximize efficiency of the infrastructure.

As such the hot water is actually billed in kwh since all you are doing is extracting energy.

 

[LunarMist]

Maybe they can run some city cold water like air conditioning in the summer.