Better solution: stop creating heat in the home. Instead of using gas or electricity to heat water, use a heat pump joined to the A/C. Store greywater and heat that up, then send it down the sewers. A liter of water has the same heat capacity as 3 cubic meters of air and a person uses 300+ liters of water per day, enough to cool 3200 square feet of house by 10 F.
I wish there were viable commercial solutions for this.
The other day, when it was 106F outside and I had to dry some clothes, I found it quite unfortunate that I was spending a bunch of energy to move hot air out of my house, while at the same time spending a bunch of energy creating hot air in my house to dry my clothes.
It would have been so nice if there were a reasonable way for me to take the heat already in my house and push it through the dryer.
(I could have hung them to dry, but I live too close to the freeway to do that -- they would have been dirtier than when I washed them)
Your dryer should be in unconditioned space, at least during the summer. That's easy if it's in its own room with a window. Summer: window open, door closed. Winter: window closed, door open, vent inside.
There is such a thing as ventless clothes dryers, from major brands such as Whirlpool, LG, etc. [1] We had an older one in an apartment we rented; it had a water reservoir that collected the moisture which you had to empty into the sink regularly.
A large number of clothes dryers in Europe (save for the UK, which still uses a lot of hotboxes) are condensation dryers. Some countries (Sweden I believe) actually don't allow vented hotbox dryers for new construction due to building codes explicitly barring them. Heat pump dryers have been around for about 3-4 years now, but condensation dryers have been around for decades.
In the US, but have been running Bosch condensation dryers for over a decade. Previous rental had one and the immediate difference I noticed was how much longer my clothes lasted from the cooler temps, so when I moved I bought my own W/D. No regrets.
And more recently, heat pump dryers, which can dry basically as fast as standard electric dryers, while not requiring a vent, and using much less energy. You get double benefit form the heat pump, as the hot side heats the air in the dryer more efficiently than a (resistance-based) electric heater, and the cold side chills the moist air, extracting the water to be drained.
s you say, this seems very wasteful. Now, I don't live in a place where A/C is needed (I have lived in the tropics several times in my life but never had it), but from what I recall it causes the air to be extremely dry! That would mean you can just hang your clothes up and the water would evaporate out of them pretty quickly, no?
"Really dry" is very relative. The HVAC in my house in FL barely keeps my house in the 50% humidity range in the middle of a muggy summer. My clothes won't dry super fast at that humidity level.
I took that figure from the USGS per capita household water use[1], which was 300-380 liters per day. Watering plants may make up as much as 20% of that but the biggest culprits are toilets and showers. This report[2] directly measured 1000 households and found daily direct water consumptions from 456 liters to 1815 liters(jesus).
For a while in the 70's, inspired by a book I'd read (maybe Nomadic Furniture, by Papanek and Hennessey) I took my showers with the drain closed. I would paddle around in the ankle deep warm water and leave it in the tub until cool, thus warming my chilly bathroom and small apartment for "free".
You can actually recover heat from sewers which can heat water or space in nearby buildings. The first example of this (in North America at least) went online in Vancouver around 2010[1].
> Similar to a geo-exchange (or geothermal) system, heat pumps transfer thermal energy from the warm sewage supply to a higher temperature range that’s effective for residential space heating and domestic hot water. While similar in concept, sewage heat recovery is more efficient and cost effective than typical geo-exchange systems. The heat source (raw sewage) has a higher temperature than ground-source heat (on average 18 degrees Celsius as opposed to 8), so it requires less energy to upgrade. Secondly, accessing the sewer line is less invasive and less capital cost intensive than drilling into the earth to access geothermal heat. It also utilizes a continuous supply of waste heat, closing the loop on a fundamental energy >> waste >> energy stream. [2]
It might reduce the buildup of sediment inside pipes. It also might increase pipe erosion. It would probably have a comparable ground-warming effect to geothermal sinking. I have no idea what effect it would have on wastewater treatment plants, but it would cause significant warming local to sewage outflows similar to how water-cooled power plants can disturb river ecosystems. It would probably make sewage maintenance much more difficult since it would be so hot and humid. It might drive out animals living in the sewers, or just make it impossible for them to survive. I have no idea what that would mean. Mainly I was thinking that it would be a great deal easier to simply deal with the heat at the wastewater plant, but there would also be an immense heat sinking effect because of all the distance traveled inside sewers.
I was only thinking of it in context of using the ground to sink heat, not as a real implementable plan. I think it goes without saying that the heat-pump-as-a-water-heater idea is far more pragmatic.
