4 ms·

> Solar has less single points of failure and if it fails not much happens On the surface this is very true. However, types of solar have caveats that do not m

> Solar has less single points of failure and if it fails not much happens On the surface this is very true. However, types of solar have caveats that do not manifest until you have a certain amount of utilization in the grid. Photovoltaics do not contribute to inertia. This is the Newtonian concept that ensures instantaneous voltage stability separate from any active demand/generation management functions. The more inertia you have, the more work it takes to speed up or slow down the grid. Hypothetically, a grid that is 50% PV solar and 50% others would experience severe stability issues if the other class of generation were to be substantially impacted (i.e. your big-bang-for-buck military targets). You cannot run a power grid on PV solar alone. It just won't work at scale.

cesarb 4y ago
> Photovoltaics do not contribute to inertia. Besides "synthetic inertia" on the PV inverters, there exist also synchronous condensers (basically a motor/generator spinning a heavy mass) which can already be found in many substations.
throw827474737 4y ago
> Photovoltaics do not contribute to inertia. This is the Newtonian concept that ensures instantaneous voltage stability separate from any active demand/generation management functions. Wait what, Newton's inertia was about physical objects, not voltage stability? You talking base vs peak demand or what?
- phyzome 4y ago
  That voltage stability is electromagnetically coupled to huge chunks of spinning iron. That's your inertia. It buffers voltage spikes. Solar, and surprisingly enough wind as well, do not contribute to this stability. It's one of the big challenges we need to figure out.
  - phyzome 4y ago
    Actually, this is something I'm not clear on: Why can't we just add free-spinning "generators" to the grid to contribute inertia?
    - ncmncm 4y ago
      Costs money. And, unnecessary.
      - phyzome 4y ago
        It's pretty clearly necessary to solve. And any kind of energy generation costs money. So I don't think that, unqualified, those are good reasons.
        ncmncm 4y ago
        Free-spinning wheels generate no energy. Electronics do the job much cheaper.
- samatman 4y ago
  The rotors of electrical generators are physical objects, with inertia.
Panzer04 4y ago
Batteries are more "inertia" than any rotational generator could ever hope to be. Inertia is only a concept because the grid has traditionally relied on rotational generators (which do have inertia). It's by no means necessary for the functioning of a power grid - isolated inverters don't need it, nor do portable rotational generators. It's useful in traditional grids because we didn't have electronics that could more or less instantaneously respond to load changes - they had to rely on spinning generators instead.
- bob1029 4y ago
  Even with synthetic inertia supplied by every inverter, you will still eventually run into a situation where the system begins to oscillate wildly if you do not have enough spinning mass.
  - p1mrx 4y ago
    What does a large spinning mass do that a computer-controlled inverter with batteries cannot?
    - bob1029 4y ago
      I will grant you a hypothetical wherein the inverters are all perfectly synchronized by some central system and have no reliance on grid voltage as the primary signaling mechanism. But, this is a precipitous arrangement. If there is any drift in the clocks or some fault in the sync protocol, you can quickly wind up with a completely dead grid (because all your inverters will have killed each other). Spinning metal is very simple and robust. The failure modes are all much more gradual in nature. Today, one or 2 bad inverters would not start a chain of horrible events because hundreds of tons of metal are not easily perturbed. Without inertia, a bad element in the grid can have substantially more impact.
      - Panzer04 4y ago
        I must admit to not being an expert in the matter - but it seems odd to expect inverters to spontaneously desync. Grid-tie inverters take their cue from the existing grid presence, so it's not like we'll have a grid full of inverters attempting to drive their own frequency slowly getting out of sync. I don't actually know how they work, but presumably they will attempt to match the available frequency at their outputs within some tolerance of their own notion of 50/60Hz (eg. they want 50Hz, if grid is 50.5 they will match that, if grid is 51 problems might start - but that's a bit contrived) A grid without rotating generators would act differently, for sure, as you won't have varying frequency to indicate if the grid is overloaded - you'd have to rely on different measures to understand how close parts of it might be to failure. "Bad actors" in the grid can already cause severe problems regardless of spinning generators; if a power station goes offline the unexpected load spike can easily trip off most of the grid anyway. Smaller, distributed generators/inverters if anything are more reliable, as a fault in one is less likely to constitute an outsize portion of power generation. "Grid inertia" today is largely a result of the total machinery attached to the grid just massively outweighing any individual actor.

cesarb 4y ago

> Photovoltaics do not contribute to inertia. Besides "synthetic inertia" on the PV inverters, there exist also synchronous condensers (basically a motor/generator spinning a heavy mass) which can already be found in many substations.

throw827474737 4y ago

> Photovoltaics do not contribute to inertia. This is the Newtonian concept that ensures instantaneous voltage stability separate from any active demand/generation management functions. Wait what, Newton's inertia was about physical objects, not voltage stability? You talking base vs peak demand or what?

phyzome 4y ago
That voltage stability is electromagnetically coupled to huge chunks of spinning iron. That's your inertia. It buffers voltage spikes. Solar, and surprisingly enough wind as well, do not contribute to this stability. It's one of the big challenges we need to figure out.
- phyzome 4y ago
  Actually, this is something I'm not clear on: Why can't we just add free-spinning "generators" to the grid to contribute inertia?
  - ncmncm 4y ago
    Costs money. And, unnecessary.
    - phyzome 4y ago
      It's pretty clearly necessary to solve. And any kind of energy generation costs money. So I don't think that, unqualified, those are good reasons.
      - ncmncm 4y ago
        Free-spinning wheels generate no energy. Electronics do the job much cheaper.
samatman 4y ago
The rotors of electrical generators are physical objects, with inertia.

Panzer04 4y ago

Batteries are more "inertia" than any rotational generator could ever hope to be. Inertia is only a concept because the grid has traditionally relied on rotational generators (which do have inertia). It's by no means necessary for the functioning of a power grid - isolated inverters don't need it, nor do portable rotational generators. It's useful in traditional grids because we didn't have electronics that could more or less instantaneously respond to load changes - they had to rely on spinning generators instead.

bob1029 4y ago
Even with synthetic inertia supplied by every inverter, you will still eventually run into a situation where the system begins to oscillate wildly if you do not have enough spinning mass.
- p1mrx 4y ago
  What does a large spinning mass do that a computer-controlled inverter with batteries cannot?
  - bob1029 4y ago
    I will grant you a hypothetical wherein the inverters are all perfectly synchronized by some central system and have no reliance on grid voltage as the primary signaling mechanism. But, this is a precipitous arrangement. If there is any drift in the clocks or some fault in the sync protocol, you can quickly wind up with a completely dead grid (because all your inverters will have killed each other). Spinning metal is very simple and robust. The failure modes are all much more gradual in nature. Today, one or 2 bad inverters would not start a chain of horrible events because hundreds of tons of metal are not easily perturbed. Without inertia, a bad element in the grid can have substantially more impact.
    - Panzer04 4y ago
      I must admit to not being an expert in the matter - but it seems odd to expect inverters to spontaneously desync. Grid-tie inverters take their cue from the existing grid presence, so it's not like we'll have a grid full of inverters attempting to drive their own frequency slowly getting out of sync. I don't actually know how they work, but presumably they will attempt to match the available frequency at their outputs within some tolerance of their own notion of 50/60Hz (eg. they want 50Hz, if grid is 50.5 they will match that, if grid is 51 problems might start - but that's a bit contrived) A grid without rotating generators would act differently, for sure, as you won't have varying frequency to indicate if the grid is overloaded - you'd have to rely on different measures to understand how close parts of it might be to failure. "Bad actors" in the grid can already cause severe problems regardless of spinning generators; if a power station goes offline the unexpected load spike can easily trip off most of the grid anyway. Smaller, distributed generators/inverters if anything are more reliable, as a fault in one is less likely to constitute an outsize portion of power generation. "Grid inertia" today is largely a result of the total machinery attached to the grid just massively outweighing any individual actor.