I've not seen one but I am in favour of the idea and try to illustrate a further expansion of it which does not happen yet. Any comments ?
Consider an English market town high street with lots of shops offices and flats with different tenants landlords and shop head offices.
Whom would one ask for go-ahead to run a one-inch "shared renewables warm water pipe" from one end of the row to the other? It needs a fair way of billing, networked computers, and a heat and flow metering inlet and outlet device available on request, but only a T joint and padlocked closed tap fitted by default. Into that pipe, anyone may sell or buy heat. Once that shared infrastructure is in place, somebodies' landlord might decide that it is a bargain to get warm water out of the pipe, run it through a couple of warm radiators to heat his appartment without switching on his boiler, return the water to the shared 1 inch pipe, and pay for metered heat taken.
Down below, the shop might look at the chiller for their stock room, decide that it is usually wasteful to dump heat to the air con outdoor fan unit, and get somone to fit a fluid to water heat pump so that heat added to the shared pipe (from chilling the stock room) gains money for the shop.
Then the pipe goes through the wall to the next shop and flat above .. Sombodies' landlord, noting that his roof is capable of earning money, gets in the hot water plumbers to do something not presently advertised, to take warm "shared renewables" water, directly run that through solar thermal evacuated tube collectors on his roof, then it goes back downstairs through the radiators in the flat to the shared pipe at a sometimes higher or sometimes lower temperature. The flat has thermostatic radiator valves of the usual kind in every room, parallel bypass pipes, and a new central heating pump so that water through the solar thermal tubes must always be moving in the daytime. Depending on solar thermal gain and radiator use, heat change in water and bills can be positive or negative. Thats right. The town renewables computer might make a net payment to this address for adding heat to the renewables pipe.
The next flat and shop are owned by a capitalist miser who won't invest in anything unless it has been demonstrated to beat his target rate of return on investment.
The next flat and shop are managed by an unresponsive holding company in Luxembourg, at the same holding company address as a couple of thousand similar tax evasion holding companies who let out shops.
The next flat and shop are owned by a pension fund and managed by cautious estate agents who don't spend money on the building.
All of those just get the pipe bashed through their wall, and don't touch the padlock on the warm water tap T's.
The next shop adds a supplimentary ducted air heating vent from a metered heat exchanger which receives sometimes warm water from the renewables pipe, and depending on the thermostat and water temperature sensor values might decide to blow warm air into the shop if necessary and available. That being supplimentary heating, not a complete replacement of shop heating, shoppers don't notice any difference at all and the existing ducted warm air shop heating gets used a bit less. The owner of that shop pays for heat used at the going rate, and that is somewhat less than his main heating.
The flat above that shop adds one extra radiator with thermostatic radiator valve and antithermostatic bypass valve, keeps all of their existing heating but uses that slightly less. The warm water then goes to a large (4kW electrical, 6 to 24 kW thermal) air source heat pump on the roof, which that landlord decided to buy as an investment. He adds extra flow/heat monitors to count the pennies worth of heat collected for the shared water pipe, and has an Elster 100C meter off the 32Amp extra circuit breaker on the consumer unit in his flat. The flat, staying well inside the 80 Amp rating, pays the electricity bill like usual, and the landlord gets the tenant to read the electricity used for the heat pump which is reimbursed. The landlord buys electricity from the tenant and sells heat to the district heating shared renewables pipe. He might decide to sublet the roof next door and cover that in solar panels too.
At the next shop, the owners don't want to invest in air source heat pump machinery but decide to buy a smaller four port "Welsh heat pump" which has inlet and outlet for warm water from the shared pipe, inlet and outlet of water to the heat exchanger of their shop ducted air heater/chiller unit, and a mains electricity connection with bidirectional metering.
This could go on, with every imaginable way of using and of making (possibly intermittent) warmth from the shared pipe. With there being several of each adds resilience against various shortages and price changes in energy without paying somebody to hedge the bill. Somebody attached to that row might decide to invest in thermal storage too. As a district heat system, this is as inhomogeneous as possible to illustrate what could be in need of heating, which is a lot less uniform than the rows and rows of appartments in Stalingrad. In common to the whole scheme through, is needed a trusted water flow and temperature heat metering device, in pairs for in/out and the trusted communications with the district heat forecast and price auctionboard computer.