Nuclear CHP as a solution

GreatApe

Modified version example to get low pumping energy needs and reducing the pressure to 2 bar

Take an example of a 1GW pipe running to London 50km away

1st Run 1 x 1GW @ 50km. 247 cm pipe 2 bar 1.2 MW pumping
2nd Runs 10 x 100MW @ 5km. 78 cm pipe 1 bar 60kW pumping (x10 pipes)
3rd runs 100 x 10MW @ 500m. 22 cm pipe 1 bar 6KW pumping (x 100 pipes)
Final run connecting upto 5,000 homes/flats/busioneses this would be done by the cold water system (so homes and businesses recieve hot and cold water at the same pressure)
The cold water runs through a heat exchanger like a traditional tank but instead of the boiler heating a coil in the tank this nuclear district heating heats the coil

Total thermal energy 1,000 MW
Total pumping energy both ways ~4 MW
So total eletrical energy to pump = about 0.4 % of the thermal energy
Very acceptable and this is not all new demand because currently we pump/pipe natural gas and homes pump/pipe water which wouldn't be required if those were replaced by district heating

And just for reference if the distance was 150km rather than 50km you just add another 4 bar pressure to the first run which only increases energy use of overall pumping from 0.4% to 0.8%

And this is for winter peak demands. Summer time the flow rate can be reduced 3 x and the pressure reduced ~4x resulting in pumping energy being reduced >90%

GreatApe

Or something like this.

Heat source 10 GW (3 X 3.3GW thermal reactors) 100km away

1st run. 100 X 100MWt pipes @ 100km. 120cm pipe 2 bar pressure
2nd run 1,000 X 10MWt pipes @ 1km. 25cm pipe 1 bar pressure
3rd run 20,000 X 0.5MW pipes @ 100m. 5.7cm pipe 1 bar pressure

That's a lot of infrastructure but bear in mind it's heating all of London of 2040. 4 million London homes countless offices shops schools hospitals cinemas hotels and everything else too

At the end of this 0.5MW run there would be a tank and the nuclear heat would run through a coil and heat this tank. This tank would feed the equivalent of 250 homes/businesses. This could be for instance a 5 ton tank at 80 centigrade in the basement of a block of flats or a 500 bedroom hotel or a hospital or a school or....you get the idea. Tank size can vary for calculated peak useage so the tank doesn't drop below say 50 centigrade. Local cold tap water would flow into the tank and feed the 250 homes with cold and hot water at the same local pressure. Could also have a backup 200KW immersion heater in this tank for redundancy/maintenance or even a gas fired boiler. Homes can draw water and use it for showers etc through a mixer tap to downblend the temperature. Or run it through a mini tank heat exchanger (30 litres would probably be fine it's mostly to not return dirty radiator water) and that heat exchanger runs the homes radiators. This tank doesn't even need to be insulted as it would only be on when you turn the central heating on and it itself can act as a radiator

Total is about 4 bar pressure
60 tons per second 40 meter height is some 24 MWe pumping and the same again for return
So about 50MW pumping for 10 GW heat transfer or 0.5%


BTW for those complaining about heat loss the current system of boilers have very high heat losses too. My system is about 5KWh per day heat loss (I know this as that's roughly what the smart meter reads for gas useage when I've been away) So it's the pure heat loss from pipes and storage tank and a total waste for about 9 months of the year. A heat pump system would presumably be the same seeing as that also has tanks and piping warm/hot water about. Also the natural gas grid loses some of its methane from well to boiler flame too. Overall you may find that a well designed well insulated district nuclear heating grid has fewer energy losses than compared to natural gas boilers or heat pumps with tanks