Using The Electricity Grid In Cities As A Source Of Heat

In the process of finding new, low-carbon ways to provide our homes with heat and electricity, it is that one might consider sources that never before came to mind. In London such a source that has been examined by researchers and an electricity network operator are the 2.5 meter wide tunnels that run for many kilometers underneath the city. In each of them are many more kilometers worth of electricity distribution cables, each of which produces so much heat from electric resistance that active cooling is required.

Currently, every 1.8 kilometers there are shafts that lead to the surface, through which cold surface air is brought in and the warm tunnel air is exhausted into the air. The study by London South Bank University researchers and UK Power Networks looked at using this heat directly for heating local houses, replacing the use of gas boilers. This is in effect similar to heating with waste heat from industrial processes, but with noticeable differences.

The thermal power available from each 1.8 kilometer section of tunnel differs between 100 – 460 kW by installing equipment at the top of the shafts. With London looking at using heat from the London Underground for heating in a similar fashion, it would be fascinating to see whether the combined heat from both underground sources could provide the city with a sizeable source of low-carbon heat, while increasing creature comfort.

32 thoughts on “Using The Electricity Grid In Cities As A Source Of Heat

  1. Amazing this energy waste stream wasn’t utilized before. Of course… preference to lead by example with the other wealthiest diocese over on that side of the pond to taint whatever they can and export adulteration of survival .

    It’s like “geothermal doesn’t make us money… well definitely don’t use the public resource waste for public resource operations to reduce taxes and produce less heat.” I guess other than their “hot air.” Welcome to the City of London.

        1. Add to that: the Persians figured out passive cooling 2000+ years ago with simple architecture. Uncomplicated waste heat chimneys that rise above ground level, with ground level inlets would reduce the cost of active cooling for these tunnels to the cost of the chimneys. As for carbon, it’s a building block of life, particularly available to plant life in the form of CO2. It’s air-born plant food.

  2. Seems like an excellent idea to incorporate tunnel infrastructure throughout the U.S. for transit and in order to better shield and move the utilities underground.

    Seems the story board can include to negate the effects of hackers and a man made or natural disaster “EMP.”

  3. That’s quiet facinating it’s not a source of heat that immediately springs to mind.

    I’ve often wondered about integrating different household appliance to better utilize “waste” products – such as the waste heat from the AC unit to preheat water heat a pool.

    Things often though tend to work the wrong way. There is usually an abundance of surplus heat in summer when you don’t want more.

    I wonder if this heat extraction from the electricity grid would suffer from it’s on potential success. Start utilizing the waste heat causes the end user to reduce their consumption which reduces the load on the network which reduces the amount of heat produced causing the end user to turn on heating and so on….

    1. „replacing the use of gas boilers“ would not lower the electric power consumption too much. If more heat pumps has to be included into the system it may raise. Someone has to do some calculations, if it‘s worth the trouble. The idea itself sounds not bad. What about putting some water pipes in the game? In parallel to the power cables, they could provide the cooling and the heat transfer to the (water/water) heat pumps. Even the planet could support the system 365 days a year with his own heat.

    2. Kinda-Sorta replacing the condenser of central AC to heat pool water is something that is done. I’m not sure how well it works given the frankly enormous amount of heat required to move the temperature of a body of water as big as a pool, but my guess is that as long as the pool water stays fairly below the outside ambient temperature, it’s probably a win-win.

    1. adding unnecessary complication to solve a problem that isn’t really a problem. how German. what if any part of the liquid nitrogen infrastructure failes? not saying it’s a bad idea but as a mechanic(who essentially specialises in German vehicles) this solution seems like it’s adding un-necesary points of failure to an infrastructure that could do without extra points of failure, for a slight gain in efficiency.

      1. A typical coal power plant generates about 600 MW, and the power lost as heat (I squared R losses in the aluminum/copper) for a city the size of London could easily require an extra power plant to compensate for the current losses in the system. It is not like the losses in the system are an insignificant rounding error, London is about 1572 square km (607 square miles).

        If you read the 2017 document that I linked to, ComEd Chicago was selecting suppliers for REG (Resilient Electric Grid) a project based on the exact same technology. Which was just given the DHS stamp of approval in July of this year to secure the nation’s electric grid against extreme weather or other catastrophic events (ref. search for “site:gov Resilient Electric Grid” in your search engine of choice).

        TL;DR Chicago is upgrading to a highly efficiency, highly fault tolerance system. Less points of failure, BIG gain in efficiency.

        1. “TL;DR Chicago is upgrading to a highly efficiency, highly fault tolerance system. Less points of failure, BIG gain in efficiency.”

          TL;DR Chicago is placing huge sums of money into the hands of cronies for a system that will be perpetually over-budget, and missing deadlines for decades to come.

          You know, because Chicago.

        1. The Chicago system will use the current generation of Amperium Laminated Wire (Yttrium barium copper oxide High Temperature Superconducting Wire), which in the absolute very worst case of a catastrophic cooling failure could still be used to route some power to critical infrastructure through the stainless steel stabiliser layer of the laminate (hospitals, PD, FD). But the overall system is nearly a ring like structure (see the linked document above) so even a cooling failure in one isolated segment does not bring down everything, the switches for the failed segment (or segment under maintenance) are open and power is routed around in the the opposite direction. People who design very large infrastructure are not morons, there is a backup to the backup for the backup system, and everything is monitored, and maintenance is factored into the design.

          1. The stainless steel layer only works with DC lines. For AC lines, the skin effect is very strong. Depending on the type of stainless, the current carrying capacity goes from about 65% of copper to “People who design very large infrastructure are not morons”

            But people who order the systems and pay for them most often are, and skip crucial details which would otherwise become showstoppers (“too much money spent, can’t back out now”). As a result, even large ships sail on good luck.

        2. Superconductors also fail spectacularly when the current through them exceeds a critical limit. They instantly lose superconductivity and become electric heaters, which causes flash-boiling of the liquid nitrogen and an underground explosion.

      2. Did you know that this project actually saves money? Cooling costs less than electric losses like those mentioned for London. And they save two buildings with transformers in the middle of the city which now can be sold.
        If cooling fails, nothing bad happens, just this one power line fails, like normal power lines do quite frequently. In even more places superconductors are used especially to fail like a fuse – but they don’t burn, but just heat up and interrupt the current flow.

    2. I don’t know how familiar you are with the UK’s infrastructure but it’s a battle to just keep it running at all, never mind upgrading to fancy new systems – thanks to the Victorians and their descendants we had some of the first water, sewerage, gas, electrical, and telephone systems… and we’ve still got most of it and rely on it to support towns and cities that have grown many times beyond the capacity of the original design.

      London especially is an astoundingly complex multi-layered beast where it’s a battle to keep up with demand – some places they can’t stuff enough wires down ancient ducts to provide service but they can’t pull 100 years of cabling out and replace it because the upheaval would be huge.

      Crossrail had some very good examples of threading tunnelling machines between victorian sewers, cable ducts, and foundations of skyscrapers with inches to spare on all sides – and they kept hitting undocumented things from plague pits to Victorian cellars.

  4. 200kW of heat is … not much. 20kW heater units for houses are quite usual. A campfire would be on the order of 200kW. A ton of cement based structure eats 2 weeks of 200kW – and a literal ton of structure is not a figurative ton of structure. My guess would be that the necessary rebuilding eats more energy than this scheme can repay.

    1. Interesting idea, and certainly worth thinking about when first building something.

      However, it’s hard to believe that the benefits of such a system would outweigh the environmental costs of retrofitting a massive complex system to an existing source of warm air, especially in London, let alone the financial costs. Plus that air is probably the last thing you want in the summer, homes probably only want it for 3 months tops.

      But if they were willing to allow a smaller-scale solution, it’s not impossible that they’d find a use for the hot air. Perhaps a local baker might want it to pre-heat their oven intake? Or they could provide free hot air to the Houses of Parliament?

  5. You have to consider the cost of creating the network of heat exchangers/piping to get that heat into homes vs the savings per year in home heating cost. If the payback period is 100 years, it might not make sense. It might make more sense to add solar heating to the homes. Again depends on the cost analysis. I often see these waste heat recovery projects collapse on the first cost analysis.

  6. Wow… Just wow.
    “Hey, we can use this waste heat to heat homes!”. How is this an improvement? Why not “Hey, let’s improve the infrastructure so we’re not throwing away a kW every kilometer!” instead?
    That’s some seriously short-sighted reasoning there.

  7. Cost analysis…. All comes down to money doesn’t it? It is interesting when I’ve talked with ‘free’ energy supporters that most don’t understand what it takes to build the infrastructure for the product to finally ‘get’ access to the ‘free’ energy. Someone and something has to dig the material out of the hill (takes energy). There is trucking material to a mill, a mill to make a raw product when goes to a factory, etc….. All takes energy and resources (human as well) which translates to taking time, energy, and money to build. Free? Far from it. Hopefully over time you get more energy from the device than you put into it. Otherwise the exercise is futile.

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