https://www.lowtechmagazine.com/2015/12/fruit-walls-urban-fa...
...and leaving those heat sources on continually... well... that's very energy inefficient, to say the least.
This is often done on north-facing walls in greenhouses. In winter when the sun is low, the thermal mass gets a lot of light and absorbs it as heat. Then at night it releases it to balance out nighttime lows. In summer when the sun is high up, because it's a wall there's less surface area that absorbs the radiation, so it's self-regulating to a degree.
Same idea is even used for seasonal thermal storage. Look up "earth batteries" on youtube, usually it's permaculture folks. Basically, put air circulation pipes a couple feet below a greenhouse. In the summer, you flush your (too hot) hot air through it, the ground absorbs the heat, and you cool off your greenhouse. In the winter, the same process absorbs some of the heat out of the ground. Some numbers I've heard is a greenhouse can stay at 50 degrees when it's -20 outside. Basically same idea as a geothermal heat pump, but much simpler because all you need is a blower fan and some pvc.
And a lot of land area.
That last part tends to be the problem.
But: we need to build low energy housing to manage climate change. That means there is very little waste energy available. Last house we built was 230m2, family of 5, had a total energy consumption, including everything from heating to water to home electricity, sitting at 8000kWh/y. That's in southern Sweden (N58deg).
There is no relevant amount of waste energy available.
This is the kind of housing we'll need to meet future energy targets.