Author Topic: Where does the power go ?  (Read 7383 times)

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Offline PinheadBE

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Where does the power go ?
« on: August 20, 2017, 06:24:56 AM »
Hi there,

Here's a somewhat dumb question, but it haunts me for a couple of nights now while it probably shouldn't....

All our means of producing electrical power are running 24/7.
But, obviously, at some times, all of the power which is produced is not used.  For example, during the night.

So, if I simplify the whole grid to one producer (say a 1 GW nuclear power plant) and a bunch of consumers which at a certain time consumes only 500 MW, where do the other 500 MW go ?  |O

The decay of uranium in the reactor produces the same amount of heat which is transformed in the same amount of steam which in turn makes an alternator turn at the same speed, but the counter-eletromagnetic force exerced on it may be lowered (due to the lower consumption on the grid).
So, where does the remaining power go ?

(The same reasoning could be applied with other energy sources such as a wind farm or a coal power plant; the nuclear reactor is only used as an example)

Sorry if this is, indeed, dumb, but pls, help me to regain some restorative sleep....  :=\

Thanks, and good night  :-+
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Offline stmdude

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Re: Where does the power go ?
« Reply #1 on: August 20, 2017, 06:31:12 AM »
The decay of uranium in the reactor produces the same amount of heat

The decay is actively controlled by "control-rods", which can increase or decrease the output of the reactor.

Now, the demands of the grid can change faster than the control-rods can change the power-output of the reactor, which is (one of the) reason that the voltage in your outlet actually varies.
In my home, I've seen 210V -> 240V RMS.
 

Offline Someone

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Re: Where does the power go ?
« Reply #2 on: August 20, 2017, 08:18:06 AM »
Wikipedia has a good introduction to this:
https://en.wikipedia.org/wiki/Load_following_power_plant
There aren't many references to learn more details, so you'd need to hunt down some industry information to learn more about how each specific type of plant handles load changes. But for the very fast changes its often just pouring extra energy into the condensers, simply dumping that energy as heat into the atmosphere.
 

Offline IanB

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Re: Where does the power go ?
« Reply #3 on: August 20, 2017, 08:49:51 AM »
All our means of producing electrical power are running 24/7.

But, obviously, at some times, all of the power which is produced is not used.  For example, during the night.

So, if I simplify the whole grid to one producer (say a 1 GW nuclear power plant) and a bunch of consumers which at a certain time consumes only 500 MW, where do the other 500 MW go ?

Broadly speaking, the amount of power generated is continuously adjusted to match the demand. The grid managers use models and historical data to predict how the demand will change at various times of the day and so they can plan ahead for how to adjust generator output.

If there is excess power generation at any instant it can also be stored for later use, for example in hydroelectric facilities by pumping water up into a higher reservoir.
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Online Ian.M

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Re: Where does the power go ?
« Reply #4 on: August 20, 2017, 09:02:18 AM »
Also https://en.wikipedia.org/wiki/Demand_response
e.g an industrial consumer with a large electric smelter, furnace or kiln can get a preferential tariff for scheduling their peak power usage to suit the grid management authority, and can also load-shed on electronic request for short periods up to a few minutes without significantly affecting the process due to the large thermal inertia.
 

Offline T3sl4co1l

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Re: Where does the power go ?
« Reply #5 on: August 20, 2017, 09:37:46 AM »
Many power plants can't vary their output much (nuclear is a good example of a base load generator, in fact).  What they can't control directly, they shunt regulate: that is, the excess power is sent to the cooling towers, or cooling water, or burned in very large resistors (think power transmission towers, but strung up with stainless steel rods that run red hot under load!).

This continues to be a problem as nuclear fuel is changed: the removed fuel continues to "glow" with significant power for some time (decades).  It must be stored in a pool with circulating water.  (After some time, it's not that it's sweltering hot, in and of itself, but just that there's an industrial quantity of it in the pool, and if the water isn't kept circulating, the pool eventually boils off.  A fuel bundle, some years after removal, could be stored outside without being noticeably hot (thermally).  It might be a bit toxic with radiation though. :)  (In contrast, water blocks radiation very nicely; you could swim pretty far in such a spent fuel pool.)

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Offline Jr460

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Re: Where does the power go ?
« Reply #6 on: August 20, 2017, 10:23:20 AM »
I don't know of any plants where they "dump" energy.

I'm most familiar with fossil fired plants.  So that is where I will start.

You would be surprised how quickly a unit can ramp up load.   I've seen the load charts in controls go from 250MW to over 500MW in about 10-15 minutes.   Why 250MW as a base?   Well that was about 50% load on the unit and below that the efficiency of the unit drops rapidly.

If you need faster response to overall system load, then smaller units or gas turbines (jet engine basically) that top out at about 90MW can be started and follow load quickly until you larger units in the system ramp up.  If you still can't keep up, then then the system frequency drops for a bit, but track that over time and make up for it later so over a day the looks that run on small synchronous motors are not off by more than a second.

Any way, as you add load to a generator, it wants to slow down.  The controls then open the steam control valves a bit more to keep it spinning right at 3600RPM.  Of course then the steam flow goes up which means the pressure goes down, and level in the steam drum goes down.  This causes the feed water pumps (run by a small turbine off the first stage extraction steam) to ramp up and put water faster into the boiler.  This causes the temp to start go down which causes the forced draft fans to push more air into the coal mills which increase the fuel flow.  Then of course other controls adjust induced draft fans to match the full flow.

Seems like a bunch of steps, but it is all interconnected with feedback and feed forward control systems.  So having a load of X schedules a basic fuel flow, and the controls fine tune everything.

The only times things are "dumped", and I've seen it....  is a unit trip.  Full load and the unit trips, the control cut off fuel and slam all kinds of valves closed.  The fans and dampers for boiler air to to max to push all the air they can into the boiler.  Even with nothing burning a a 14 story high boiler has a lot of mass that can't cool that quickly.   Thus the water/steam trapped in the system increase in pressure until a big safety pop-off values opens on the roof.   The whole build shakes.

The reverse happens if the load goes down, load or heat, nothing is dumped.  Everything is saved.   Just the cooling for the stator in the generator is routed to help pre-heat air into the boiler.

Now a nuke.  In a BWR design, the controls rods make gross adjustments.  Reactor power is control by adjusting the flow of the recirculation pumps.   Run them faster and you more cool and denser water into the core.  Denser water means more neutron moderation and reactivity and power levels go up.  I'll admit, I'm not up on PWR reactors and power control.

Bottom line.  Power doesn't go anywhere because they never generate it in the first place.  Yes, larger units react ti changing load a bit slower.  Most reasons for minimum loads or staying at fixed load is based on operational issues and the mostly running the unit at the most efficient point.
 

Offline IanB

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Re: Where does the power go ?
« Reply #7 on: August 20, 2017, 11:10:23 AM »
Any way, as you add load to a generator, it wants to slow down.  The controls then open the steam control valves a bit more to keep it spinning right at 3600RPM.  Of course then the steam flow goes up which means the pressure goes down, and level in the steam drum goes down.  This causes the feed water pumps (run by a small turbine off the first stage extraction steam) to ramp up and put water faster into the boiler.  This causes the temp to start go down which causes the forced draft fans to push more air into the coal mills which increase the fuel flow.  Then of course other controls adjust induced draft fans to match the full flow.

Seems like a bunch of steps, but it is all interconnected with feedback and feed forward control systems.  So having a load of X schedules a basic fuel flow, and the controls fine tune everything.

The control system is like a finely orchestrated ballet. One interesting point about the part highlighted above. When the pressure goes down, the steam bubbles in the tubes expand, causing the level to go up, initially. This effect (and the reverse) is known as "shrink and swell". It obviously has an impact on the response of the level controller, which is the kind of thing which complicates the design of control systems.
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Offline Someone

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Re: Where does the power go ?
« Reply #8 on: August 20, 2017, 01:05:53 PM »
I don't know of any plants where they "dump" energy.

I'm most familiar with fossil fired plants.  So that is where I will start.

You would be surprised how quickly a unit can ramp up load.   I've seen the load charts in controls go from 250MW to over 500MW in about 10-15 minutes.   Why 250MW as a base?   Well that was about 50% load on the unit and below that the efficiency of the unit drops rapidly.

If you need faster response to overall system load, then smaller units or gas turbines (jet engine basically) that top out at about 90MW can be started and follow load quickly until you larger units in the system ramp up.  If you still can't keep up, then then the system frequency drops for a bit, but track that over time and make up for it later so over a day the looks that run on small synchronous motors are not off by more than a second.

Any way, as you add load to a generator, it wants to slow down.  The controls then open the steam control valves a bit more to keep it spinning right at 3600RPM.  Of course then the steam flow goes up which means the pressure goes down, and level in the steam drum goes down.  This causes the feed water pumps (run by a small turbine off the first stage extraction steam) to ramp up and put water faster into the boiler.  This causes the temp to start go down which causes the forced draft fans to push more air into the coal mills which increase the fuel flow.  Then of course other controls adjust induced draft fans to match the full flow.

Seems like a bunch of steps, but it is all interconnected with feedback and feed forward control systems.  So having a load of X schedules a basic fuel flow, and the controls fine tune everything.

The only times things are "dumped", and I've seen it....  is a unit trip.  Full load and the unit trips, the control cut off fuel and slam all kinds of valves closed.  The fans and dampers for boiler air to to max to push all the air they can into the boiler.  Even with nothing burning a a 14 story high boiler has a lot of mass that can't cool that quickly.   Thus the water/steam trapped in the system increase in pressure until a big safety pop-off values opens on the roof.   The whole build shakes.

The reverse happens if the load goes down, load or heat, nothing is dumped.  Everything is saved.   Just the cooling for the stator in the generator is routed to help pre-heat air into the boiler.

Now a nuke.  In a BWR design, the controls rods make gross adjustments.  Reactor power is control by adjusting the flow of the recirculation pumps.   Run them faster and you more cool and denser water into the core.  Denser water means more neutron moderation and reactivity and power levels go up.  I'll admit, I'm not up on PWR reactors and power control.

Bottom line.  Power doesn't go anywhere because they never generate it in the first place.  Yes, larger units react ti changing load a bit slower.  Most reasons for minimum loads or staying at fixed load is based on operational issues and the mostly running the unit at the most efficient point.
Have a look at the efficiency of the plant during slewing down, it drops substantially and that waste energy is dumped as heat. There are many cascaded control loops in such a large and complex system but since many of them run hard against the material limits to improve efficiency any perturbations (particularly down slew) creates a lot of waste heat while the system stabilises again. Efficiency/waste heat gets progressively worse as the slew rates increase right up to the catastrophic fast 100% down to 0% unplanned trip/scram.
 

Offline denverpilot

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Re: Where does the power go ?
« Reply #9 on: August 20, 2017, 01:45:53 PM »
Besides the excellent comments above, from hanging around family members in the power biz...

In addition to efficiency there's also designs of plants that simply aren't stable enough to operate outside of certain limits. Especially in nuclear power. But boilers have both low and high limits too. Turbines are a lot less sensitive overall, but have lubrication and speed limits as well.

Chernobyl being the prime example of doing that, even as a test, and doing it way wrong, of course.
 

Online blueskull

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Re: Where does the power go ?
« Reply #10 on: August 20, 2017, 04:24:14 PM »
Also, some generators can bleed off hot steam to bleed off extra energy before governor and fuel chamber can keep up.
I used to work on a microturbine that burns natural gas and diesel, the unit has lead acid batteries to store energy in case of a sudden load shift, it also allows efficient light load condition.
When a huge load dump occurs and the battery simply can't handle such high power, the system bleeds off hot gas to atmosphere to prevent turbine overspeed.
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Offline IanMacdonald

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Re: Where does the power go ?
« Reply #11 on: August 20, 2017, 09:33:33 PM »
Basically there is only limited storage capacity on the Grid, so generation has to be matched to demand as an ongoing process. In the UK anyway, the frequency is used as a means of signalling over or under supply. If it gets a bit below 50Hz then all contributing stations will tend to ramp their output up. Not sure if other Grids use this principle or not.

When heavier loads are anticipated, extra stations are asked to become 'spinning reserve' -That is, turbines revolving and synced-up bit not delivering any significant output. Thus they can quickly come onstream to cope with demand. If it turns out their services aren't required, the operators get paid 'constraint payments' for the fuel used to spin-up needlessly.

The controversial aspect is that renewables operators also get constraint payments, only in their case  it's for all energy which could have been delivered even if no-one could possibly have wanted it.

http://gridwatch.templar.co.uk/

Nuclear cannot vary its output rapidly, plus the main costs are the fixed ones, whilst the fuel is cheap. Thus it makes financial sense to run nuclear stations at full power as much as possible.

The main source of reserve in the UK is combined cycle gas turbine plant. Although this can come onstream very quickly it takes time (an hour or so) for the secondary steam cycle to start up, and that means accepting a significant reduction in efficiency under start/stop operating conditions. 
 

Offline Jr460

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Re: Where does the power go ?
« Reply #12 on: August 21, 2017, 12:20:10 AM »
Let me correct a few things I see.

The turbine speed.   It is held at 3600RPM.   It does not vary according to load.

A unit has lower efficiency when run below full load, that is a given.   I've had to measure it many times and produce the graphs of heat rate vs load.  Not easy, it is an all day task for several people to gather the data.  Then a few days of compiling and crunching all the numbers.  You can do it quick and fast, but it is not very accurate. 

However it was implied that to run at lower loads a unit dumps energy.  That is just not true.  You put less energy into the system to start with.   All kinds of odd things can happen as load shifts quickly,  but still no control system or part of the plant that is designed to "dump" energy.  One exception as listed is a unit trip.

Efficiency can be very confusing.  And example, for the same fuel input I can get 5% more load out of a unit, but it's efficiency goes in the toilet.

Any unit has diagrams showing a heat balance around the whole system, including what is required by either river water or cooling tower for the condenser.  These are shown for several different load conditions.   Break out your steam tables and look at one. 

Might not be the best example, but a quick Goggle search shows one with a lot of the details.  https://www.slideshare.net/jitendramechi/heat-balance-diagram
 

Offline petergebruers

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Re: Where does the power go ?
« Reply #13 on: August 21, 2017, 12:29:30 AM »
In Belgium, they store electricuty in "Coo", a pumped-storage hydroelectric power station, it can generate 1.2 GW:

https://en.wikipedia.org/wiki/Coo-Trois-Ponts_Hydroelectric_Power_Station

I do not think the maximum energy transfer is mentioned anywhere, but I seem to remember it can deliver that 1.2 GW for "a few hours" (2 hours?). My memory is rusty, I studied energy production in 1990 and at that time it didn't generate that amount of power, but it was smaller too, so run time might be the same.

They do mention: "It generates about 1 million MWh annually and consumes about 20 percent more in pumping mode."
« Last Edit: August 23, 2017, 10:54:31 PM by petergebruers »
 

Offline Someone

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Re: Where does the power go ?
« Reply #14 on: August 21, 2017, 07:39:08 AM »
However it was implied that to run at lower loads a unit dumps energy.  That is just not true.  You put less energy into the system to start with.   All kinds of odd things can happen as load shifts quickly,  but still no control system or part of the plant that is designed to "dump" energy.  One exception as listed is a unit trip.
Its during the slew that energy is dumped, faster down slew, more dumping. The slow thermal processes can't change quickly and they can't be left to heat up as the energy demand drops, there are some co/tri gen plants that can store that energy into their thermal outputs but the majority of plants are going to dump the excess in the cooling systems. We agree in steady state that an efficient equilibrium will be found minimising the thermal waste, but they are slow processes. I introduced the dumping specifically during slewing not as a steady state condition.
 

Offline madires

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Re: Where does the power go ?
« Reply #15 on: August 21, 2017, 08:32:12 AM »
Based on statistics about power usage you can estimate how much power has to be generated at a specific date and time. Power plants with a slow response time (nuclear) are used for the base load. For periods of higher power demand additional power is provided by plants with faster response times, like coal. For peak situations there are gas turbines and other fast acting power sources. Before PV and wind farms the whole controlling system required only a few manual corrections. There's pretty good software for calculating forecasts of the power generation by PV and wind farms but it's not 100% accurate. So we have now much more manual corrections to keep the power grid stable.
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Offline Jr460

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Re: Where does the power go ?
« Reply #16 on: August 21, 2017, 08:42:02 AM »
However it was implied that to run at lower loads a unit dumps energy.  That is just not true.  You put less energy into the system to start with.   All kinds of odd things can happen as load shifts quickly,  but still no control system or part of the plant that is designed to "dump" energy.  One exception as listed is a unit trip.
Its during the slew that energy is dumped, faster down slew, more dumping. The slow thermal processes can't change quickly and they can't be left to heat up as the energy demand drops, there are some co/tri gen plants that can store that energy into their thermal outputs but the majority of plants are going to dump the excess in the cooling systems. We agree in steady state that an efficient equilibrium will be found minimising the thermal waste, but they are slow processes. I introduced the dumping specifically during slewing not as a steady state condition.

Yes I understand what you are saying.  However I'm skeptical.   I say this because even if the load drops quickly, you still are generating hundreds of MW.  So let's say load drops from 500 to 300 MW in a minute, and remember this one of many units on the grid, so each unit is trying to ramp back a similar amount.  300MW is still a good amount of power by anyone's standards, so I ramp the fuel back to what would be needed for 250MW rather than 300 and let the thermal flywheel keep me going at 300 for a bit.  Like I said early in this thread, you would be surprised how quickly you can change the load.  For example, a unit being spun up.  The generator is not connect to the grid and the turbine is spinning at 3600 RPM.  When the breaker closes in less than a second I saw it jump to 20 MW, before the operator put the controls in hold mode rather than load-follow.

I don't have access to the charts from a unit anymore, otherwise I find one of load and compare with water temp being sent to the cooling tower during a ramp down in load.  Because that is only place the waste process heat goes.  And you just can't dump anything you want into it, it has limits as to how much heat it can remove.  If you do, then the temp in the condenser goes up, the back pressure goes up and you are start hurting the last stage turbine buckets.  (note this is not a problem when the unit trips, turbine speeds down to a few RPM and put on the turning gear, and dump valve opens from the main steam lines past the stop and control valves directly into the condenser.  It prevents that trapped steam from over speeding the turbine, but is minor in the amount of heat in the whole boiler and unit piping.)
 

Online Mr. Scram

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Re: Where does the power go ?
« Reply #17 on: August 21, 2017, 08:47:26 AM »
Many power plants can't vary their output much (nuclear is a good example of a base load generator, in fact).  What they can't control directly, they shunt regulate: that is, the excess power is sent to the cooling towers, or cooling water, or burned in very large resistors (think power transmission towers, but strung up with stainless steel rods that run red hot under load!).

This continues to be a problem as nuclear fuel is changed: the removed fuel continues to "glow" with significant power for some time (decades).  It must be stored in a pool with circulating water.  (After some time, it's not that it's sweltering hot, in and of itself, but just that there's an industrial quantity of it in the pool, and if the water isn't kept circulating, the pool eventually boils off.  A fuel bundle, some years after removal, could be stored outside without being noticeably hot (thermally).  It might be a bit toxic with radiation though. :)  (In contrast, water blocks radiation very nicely; you could swim pretty far in such a spent fuel pool.)

Tim
I've been told that swimming in a spent fuel pool actually exposes you to less radiation that being outside of one, due to the water also blocking background radiation. Only when you dive deep and come quite close to the rods, you get into trouble.
 

Offline rs20

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Re: Where does the power go ?
« Reply #18 on: August 21, 2017, 09:08:03 AM »
Have I been living under a misconception? I thought when supply dropped, the main consequence was:
-- Reduced current flowing through the generators at the plant,
-- This reduced current means there's less torque holding back the turbines, so the resulting power imbalance causes the rotor's speed start to increase (assuming no control system intervenes)
-- This higher rotor speed manifests as a higher frequency in our power sockets at home, not higher voltage (the voltage at the plant might maybe move as well, but there's so much voltage regulation/autotransformers between there and your house that there's not going to be any correlation left over.)

Thus, in a very real sense, all the generators in the grid are rotating in lockstep, as if they're connected by some sort of mystical invisible (albeit slightly stretchy) belt, with all the steam turbines trying to spin the generators faster and all the users extracting energy by trying to slow the rotor down (extracting power in the process). Hence, the problem of matching supply to demand reduces to a problem of regulating steam to a turbine in order to regulate its rotational speed (albeit actually very complicated with so many different plants etc). Of course, the grid operators have control over many of our hot water cylinders, which is an excellent place to dump pulses of excess load (if it helps, think of it as a "brake" for the turbines), in addition to pumped hydro and battery storage, etc.

Hence, the short-term imbalance storage capacity of the grid is in the combined mechanical inertia of all the generators in the grid, not (traditionally) capacitors. This manifests as the mains frequency shifting over time, as shown here. The cool part is that many grid operators guarantee that although the frequency might change in the short term, the total number of cycles per day or per week are tightly regulated to be correct; so you can use it as a pretty decent time source for a clock (and indeed, many clocks used to work this way.)
 
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Offline IanB

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Re: Where does the power go ?
« Reply #19 on: August 21, 2017, 09:26:42 AM »
Have I been living under a misconception? I thought when supply dropped, the main consequence was:
-- Reduced current flowing through the generators at the plant,
-- This reduced current means there's less torque holding back the turbines, so the resulting power imbalance causes the rotor's speed start to increase (assuming no control system intervenes)
-- This higher rotor speed manifests as a higher frequency in our power sockets at home

This is true in principle if you had a single generator running the load. But when you have a whole grid with many generators connected, they all get synchronized to the same speed. There is so much inertia in the system that one generator cannot really affect the system frequency.

What happens instead is that the generator with too little load advances its phase angle slightly relative to the grid, while still keeping the same rotational speed. The increase in phase angle causes more power to be pulled from the generator, thus balancing the situation. Therefore the generator remains "locked" to the grid frequency even when there is a load imbalance.
I'm not an EE--what am I doing here?
 
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Offline djacobow

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Re: Where does the power go ?
« Reply #20 on: August 21, 2017, 09:31:07 AM »
Dumping electric power into resistors is very uncommon, but it has been done. I encourage anyone to Google the "Chief Joe Braking Resistor" operated by the Bonneville Power Administration for decades. At times it was cheaper and easier to dump excess hydropower this way then it was to throttle dams. Keep in mind that many dams are under legal requirements to flow a certain amount of water, so turning the flow down is operationally problematic.

Nowadays, controllers have access to a large array of resources in any balancing area and can combine small changes at many units to get the ramps they need. Typically this will not involve nukes and other "baseload" units, but more flexible generation like combustion turbines and combined cycle generators. Also, operationally, renewables are more like baseload, as they cannot be dispatched "up" and it's economically problematic to dispatch them "down."
 

Offline Someone

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Re: Where does the power go ?
« Reply #21 on: August 21, 2017, 12:00:24 PM »
Many power plants can't vary their output much (nuclear is a good example of a base load generator, in fact).  What they can't control directly, they shunt regulate: that is, the excess power is sent to the cooling towers, or cooling water, or burned in very large resistors (think power transmission towers, but strung up with stainless steel rods that run red hot under load!).

This continues to be a problem as nuclear fuel is changed: the removed fuel continues to "glow" with significant power for some time (decades).  It must be stored in a pool with circulating water.  (After some time, it's not that it's sweltering hot, in and of itself, but just that there's an industrial quantity of it in the pool, and if the water isn't kept circulating, the pool eventually boils off.  A fuel bundle, some years after removal, could be stored outside without being noticeably hot (thermally).  It might be a bit toxic with radiation though. :)  (In contrast, water blocks radiation very nicely; you could swim pretty far in such a spent fuel pool.)

Tim
I've been told that swimming in a spent fuel pool actually exposes you to less radiation that being outside of one, due to the water also blocking background radiation. Only when you dive deep and come quite close to the rods, you get into trouble.
This is from an old xkcd "what if":
https://what-if.xkcd.com/29/
Its focused on the fuel as a source and missing many of the other pathways that a human could be exposed to radiation in such a pool. The activation products in the water:
https://en.wikipedia.org/wiki/Activation_product
Which come from impurities and corrosion material would pose a significant safety hazard, so much that significant decontamination is required for objects coming out of the water. There are some numbers in here:
http://www-pub.iaea.org/MTCD/Publications/PDF/te_1081_prn.pdf

Swimming in such a mixed and unpredictable media is insane, I don't recall ever seeing a certain famous radiation "tourist" ever going swimming where neutron sources could be present even though they would happily eat an apple:

Understanding the nuclide chains, chemistry of the materials, and exposure pathways is very complicated. But we know that nuclear storage ponds are going to have some biologically active impurities which could enter your body if exposed to the water.
 

Online Red Squirrel

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Re: Where does the power go ?
« Reply #22 on: August 22, 2017, 06:08:35 PM »
If you are Hydro One, what you do is sell all the excess power at a loss to the states, and then when you need extra power, you buy it from Quebec at 5x the market value.  When you realize you are losing money doing this, you just keep increasing everyone's hydro bill.   :-DD

On more serious note, I had a similar question once and from what I recall, turbines can sorta act like flywheels, based on demand a turbine that is in motion will either lag behind and act as a motor or try to push harder, causing the others to act as motors.  At least in simple terms, I think that is sorta what happens. 

 

Online Mr. Scram

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Re: Where does the power go ?
« Reply #23 on: August 23, 2017, 01:38:14 AM »
In Belgium, they store 1.2 GW in "Coo", a pumped-storage hydroelectric power station:

https://en.wikipedia.org/wiki/Coo-Trois-Ponts_Hydroelectric_Power_Station
You mean 1.21 GW?
 

Online dr.diesel

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Re: Where does the power go ?
« Reply #24 on: August 23, 2017, 03:31:06 AM »
Jr has correctly answered, and I wrote quite a bit about this (coal plant operation from the control system side) several years ago here.  But if there are further questions please ask and I'll elaborate.


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