Friday, January 21, 2011

An Opportunity for Underground Electricity Transmission?

Electricity transmission is a significant barrier to ramping up renewable capacity. The New York Times published a story this week about Texas where the Public Utility Commission has struggled to site 2,300 miles of new transmission lines. Much of the battle revolves around citizens unhappy with the prospect of lines degrading the quality of public and private property. Utilities are also constrained and looking to avoid costs associated with circuitous routing and permitting.

Controversies over electricity lines always leave me envious of the Germans. In Germany, a country that stands near the top of world rankings for total wind capacity, distribution lines are mostly underground – a considerable factor in mitigating localized power outages caused by downed trees. Destruction of infrastructure during WWII explains why Germany has a more modern and reliable electricity system compared to the US. Germany is also exploring underground transmission options through a pilot project near Bremen. Historically avoided due to premiums on installation and maintenance, underground transmission lines may be a solution to overcoming stateside NIMBY battles.

What exactly are the barriers to placing transmission lines underground? An operational barrier, emphasized by the American Transmission Company, is the fact that electricity transmission creates heat, which must be dissipated for safe and reliable delivery of power. While air is a much more effective medium for heat transfer relative to soil, releasing heat into the atmosphere is a waste of a valuable resource. If heat is released into the soil, however, the challenge of heat dissipation may be an opportunity for efficient heat capture. Capturing electricity transmission waste heat is a concept I’ve not heard about. Geothermal heating and cooling, a process that uses convection and heat pumps to capture ground warmth, is the obvious comparison.

There seem to be opportunities for coupling underground transmission development with heat capture, or combined transmission and heating. Namely, a chief inefficiency in the electrical grid, unused electrons, can be transformed into a revenue generating tool as heat is captured and sold to customers. This benefit alone may be enough to overcome the cost barriers associated with placing transmission lines underground. On the other hand, it seems like a bad idea putting fluids in close proximity to an electrical current. An additional concern is infrastructure requirements (I.e., electrical and fluid piping) under the principle of placing people close to heat sources to minimize heat loss, but away from electrical currents to minimize health risks.

I believe that is as far as my hair-brained idea should go without consulting experts. What are your thoughts? Has this concept been introduced before?


  1. As far as reliability, I remember over the last year or so that Maryland had a much bigger problem with power outages from the snow storms and summer storms than did downtown DC, despite having the same power utility responsible for maintaining transmission (PEPCO).

    A lot of the outages, as you say, were due to fallen trees. One difference between the suburbs (and even the outer part of the District): the District bans overhead wires in the L'Enfant City. When trees fell in intown neighborhoods, there weren't any wires for them to hit on their way down.

    This might be an environment in which you could explore more about the heat capture idea, since facilities are already in the ground.

  2. When you're talking about remote generation, though, you're almost entirely talking about renewables (onshore wind, maybe solar or geothermal in years to come) that are pretty marginal in cost terms. If the cost of connecting them to the grid were raised massively by having to bury the transmission network, it could kill those projects' viability completely. If the Germans can demonstrate it works, it might be useful for short stretches near to particularly sensitive locations or where planning is proving impossible. For long stretches I'm not convinced it would be worth it, potential additional revenue streams from piped heat notwithstanding.

    Of course, a load of heat in the middle of nowhere isn't much of an economic boon either. Unless you can find a way to transmit it to where it can be used without losing most of its energy potential you'd have the same energy-loss problem as with the HV cables.

  3. Heat capture wouldn't be a viable option for many projects let alone most land along a single transmission line. I see it sort of as district heating, which is viable only in communities with power generation and residential/commercial property in close proximity. Also, in locations where significant (re)development is occurring, there are efficiencies to be gained in doing things right from the start (i.e., laying pipe to share waste heat).

  4. "Thermal energy generation
    from underground power
    transmission cables." See page 47 of