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  1. 13 Jun '14 16:35 / 7 edits
    http://phys.org/news/2014-06-iberian-peninsula-geothermal-power-current.html

    Although this link doesn't mention this, I think one thing that makes this type of renewable energy very attractive is that there is no need for off-the-grid energy storage for this type because you can simply enough control power output by controlling fluid flow rate through the boreholes.

    For this reason, I think this could complement solar and wind energy very well because it could be powered up when there is little sun or wind and powered down when there is plenty of solar and wind and thus reduce the required amount and therefore the total cost of off-the-grid energy storage.

    I definitely think a lot more research should be done into this.
  2. 13 Jun '14 17:49
    Originally posted by humy
    For this reason, I think this could complement solar and wind energy very well because it could be powered up when there is little sun or wind and powered down when there is plenty of solar and wind and thus reduce the required amount and therefore the total cost of off-the-grid energy storage.
    What are the savings to me made when you power it down? I suspect that they are not significant enough for your proposal to make sense. Why not simply keep it powered up 24/7 and not bother with solar and wind?
  3. 13 Jun '14 21:23 / 1 edit
    Originally posted by twhitehead
    What are the savings to me made when you power it down? I suspect that they are not significant enough for your proposal to make sense. Why not simply keep it powered up 24/7 and not bother with solar and wind?
    Or at the least use it as the base load in place of coal/oil/gas.

    I also don't think that geothermal would be as responsive as all that.

    It' takes time for the hot rocks to heat the water to turn it to steam.
    Even if you stop pumping water in, it will take a while for steam to stop
    coming out.
    And it's even worse trying to start back up.

    Unlike gas turbines which turns on and off within seconds, this would take
    minutes, or tens of minutes at the minimum.

    Also, you get lots of minerals in the steam, if you keep cooling the system
    down you're likely to get lots of deposits on all your turbine blades, which
    is a big enough problem as it is.


    EDIT: Although I'm not knocking geothermal, I think it's a highly undervalued
    power source. And it's also a good source of hot water for heating homes
    and businesses. Iceland has hot water networks which supply hot water
    to peoples homes and offices which is much more efficient [and green] than
    everyone having their own heat generation.
  4. 13 Jun '14 21:48 / 1 edit
    Originally posted by twhitehead
    What are the savings to me made when you power it down? I suspect that they are not significant enough for your proposal to make sense. Why not simply keep it powered up 24/7 and not bother with solar and wind?
    What are the savings to me made when you power it down?

    Being able to power it up only when the energy is needed would save on the amount of and therefore the total cost of energy storage. I don't know how to calculate that cost saving but I would guess it would be considerable because off-the-grid energy storage generally doesn't come cheap!
    I suspect that they are not significant enough for your proposal to make sense.

    the only cost of powering down or powering up the geothermal power in this case would be the relatively small cost of installing a few extra valves and control systems and the tiny amounts of energy to turn those few valves. I am sure the cost of that would be covered millions of time over by the savings in the otherwise extra costs of the needed extra off-the-grid energy storage facilities.
    Why not simply keep it powered up 24/7 and not bother with solar and wind?

    Because keeping it fully powered up all the time wouldn’t work without the significant extra costs of off-the-grid energy storage because amount of electric power demanded is not constant but varies with time especially over each 24 hour period with lowest demand typically at ~4am but peak demand typically at ~7pm. The main reason for making it be able to power up and down would be to reduce the need for such expensive storage.
    Also, rigidly sticking to only geothermal wouldn't necessarily be the most cost effective option and there are many places were geothermal power is not yet economical and then you would have the problem of transmitting electricity large distances from where it is economical to where it isn't.
  5. 13 Jun '14 21:58 / 2 edits
    Originally posted by googlefudge
    Or at the least use it as the base load in place of coal/oil/gas.

    I also don't think that geothermal would be as responsive as all that.

    It' takes time for the hot rocks to heat the water to turn it to steam.
    Even if you stop pumping water in, it will take a while for steam to stop
    coming out.
    And it's even worse trying to start back up.

    Unl ...[text shortened]... fices which is much more efficient [and green] than
    everyone having their own heat generation.
    It' takes time for the hot rocks to heat the water to turn it to steam.
    Even if you stop pumping water in, it will take a while for steam to stop
    coming out.

    I am no expert on this but I assumed that the water would be kept liquid by keeping it under huge pressure until AFTER it has already reached the surface and only THEN go into a steam turbine? This would make more sense to me and would mean you could turn it off within seconds just by simultaneously turning both the valve for the water going down and for the hot water going up and do this without any part of the pipework blowing up under the pressure!
  6. Standard member DeepThought
    Losing the Thread
    13 Jun '14 22:27
    Originally posted by humy
    What are the savings to me made when you power it down?

    Being able to power it up only when the energy is needed would save on the amount of and therefore the total cost of energy storage. I don't know how to calculate that cost saving but I would guess it would be considerable because off-the-grid energy storage generally doesn't come ch ...[text shortened]... oblem of transmitting electricity large distances from where it is economical to where it isn't.
    A more or less free form of energy and you want to switch it off some of the time? It makes more sense (at least to me) to use conventional power stations to cope with peak demand and use geothermal as the base generation. I don't know how feasible that is as one has to get the conventional generators going.

    They have a pretty impressive solar generator in Spain (type PS20 into Wikipedia's search widget) but these things are limited to about 20 MW. In the U.K. wind power produces up to 10 Gigawatts of unreliable power. In the U.K. demand for power is of the order of 35GW on average and 50 GigaWatts peak, so renewables are simply not going to provide it all.

    The normal problem with renewables is that one has to have enough conventional generating capacity (or storage) to completely replace the renewable source when the doldrums strike. The advantage with geothermal energy is that that won't happen, so it may as well be left on all the time.
  7. 14 Jun '14 06:54 / 1 edit
    Originally posted by DeepThought
    A more or less free form of energy and you want to switch it off some of the time? It makes more sense (at least to me) to use conventional power stations to cope with peak demand and use geothermal as the base generation. I don't know how feasible that is as one has to get the conventional generators going.

    They have a pretty impressive solar gener ...[text shortened]... age with geothermal energy is that that won't happen, so it may as well be left on all the time.
    A more or less free form of energy and you want to switch it off some of the time?

    why would you want to extract geothermal energy out of the ground at the times when you don't need it? Better to extract it only while you need it and temporally keep it down there while you don't.

    The advantage with geothermal energy is that that won't happen, so it may as well be left on all the time.

    not full on all the time! That wouldn't make any sense because power demand is not constant with time and therefore ideally you don't want power generation to be constant but vary with demand to reduce the amount and therefore the cost for costly off-the-grid energy storage facilities although some storage would often still be needed.
  8. 14 Jun '14 09:22
    Originally posted by humy
    Because keeping it fully powered up all the time wouldn’t work without the significant extra costs of off-the-grid energy storage
    You are not making any sense.
    Suppose you have a geothermal power plant capable of supplying one city with all its power needs at peak load. During off peak, there is no need to turn it off. During off peak, there is no need to store the extra power.

    Now suppose it is not capable of supplying peak load. Then you have a choice, store some of the power generated during off peak, or look for alternatives such as solar - assuming that they happen to peak at the same time as peak load. But even under this scenario, there is no need to turn off the geothermal at any time.

    You would only ever turn off the geothermal power station if the cost of keeping it running is significant - and critically for your scenario, if the cost of keeping it running is higher than the cost of other power sources such as solar and wind.

    To reiterate:
    Your OP is suggesting that when solar and wind are producing, you turn off the geothermal. This only makes sense if keeping geothermal running costs more than solar and wind. My understanding is that this is not the case. The largest cost with geothermal is building the plant, and running costs are relatively low. Also, running costs tend not to drop significantly when you shut down a plant for part of the day. This is different from coal or gas where the running cost is directly dependent on the amount of coal or gas used.
    Solar has a similar situation in that you are not 'wasting sun' by leaving it on when you don't need the power.
  9. 14 Jun '14 09:24
    Originally posted by humy
    why would you want to extract geothermal energy out of the ground at the times when you don't need it? Better to extract it only while you need it and temporally keep it down there while you don't.
    Are you saying that geothermal heat is a finite resource, or is produced at a finite rate? If so, then you might have a case, but can you back up this claim?
  10. 14 Jun '14 10:35 / 3 edits
    Originally posted by twhitehead
    You are not making any sense.
    Suppose you have a geothermal power plant capable of supplying one city with all its power needs at peak load. During off peak, there is no need to turn it off. During off peak, there is no need to store the extra power.

    Now suppose it is not capable of supplying peak load. Then you have a choice, store some of the power ...[text shortened]... ilar situation in that you are not 'wasting sun' by leaving it on when you don't need the power.
    Suppose you have a geothermal power plant capable of supplying one city with all its power needs at peak load. During off peak, there is no need to turn it off. During off peak, there is no need to store the extra power.

    I don't understand what you mean here; How can there be “no need to store the extra power” ( actually, that is false anyway because it isn't “power” that is stored but “energy” but, of course, I know that is what you meant ) during off peak if the geothermal power plant [GPP] supplies the city with all its power at peak load?
    If, say, the GPP provides one GW of power for a city at its peak demand and the city's peak demand is exactly one GW, then if you didn't power the GPP down during off peak then, when the city is using, say, half of a GW, where would the other half of the one GW power output go without storage and/or transmission of power elsewhere? Would all that power just be wasted or what?

    Now suppose it is not capable of supplying peak load. Then you have a choice, store some of the power generated during off peak, or look for alternatives such as solar - assuming that they happen to peak at the same time as peak load. But even under this scenario, there is no need to turn off the geothermal at any time.

    Agreed. But that wasn't what I was talking about because I was talking in the context of the situation of the GPP BEING capable of supplying local peak demand and/or all the energy coming from renewables.
    Your OP is suggesting that when solar and wind are producing, you turn off the geothermal. This only makes sense if keeping geothermal running costs more than solar and wind. My understanding is that this is not the case.

    That statement makes no sense to me because once all the geothermal equipment has been installed and all the solar panels and wind turbines are installed, is it not the case that there is virtually NO cost in turning them on and keeping them on? -therefore, the 'cost' of keeping them fully on and with maximum power generation isn't a consideration.
    The largest cost with geothermal is building the plant, and running costs are relatively low.

    right -and isn't the same for wind and solar? in fact, aren't the 'running' costs for a solar panel zero?
  11. 14 Jun '14 10:37 / 3 edits
    Originally posted by twhitehead
    Are you saying that geothermal heat is a finite resource, or is produced at a finite rate? If so, then you might have a case, but can you back up this claim?
    I meant nothing more other than exactly what I said.
    But I suppose you could argue that it is a finite resource and that a given plant has finite max power output.
  12. 14 Jun '14 12:03
    Originally posted by humy
    Would all that power just be wasted or what?
    Yes, it either goes to waste or gets sent to other areas.

    Agreed. But that wasn't what I was talking about because I was talking in the context of the situation of the GPP BEING capable of supplying local peak demand and/or all the energy coming from renewables.
    I don't understand that sentence. What does GPP stand for? How would GPP supply energy to renewables? Renewables supply energy not demand it.

    That statement makes no sense to me because once all the geothermal equipment has been installed and all the solar panels and wind turbines are installed, is it not the case that there is virtually NO cost in turning them on and keeping them on?
    Yes, that is my understanding, and I believe geothermal is similar in this regard.

    -therefore, the 'cost' of keeping them fully on and with maximum power generation isn't a consideration.
    Exactly my point for geothermal - yet you suggest turning it off.
    My point is that there is no need to build solar and wind in the first place if the geothermal plant is already capable of supplying peak demand.

    right -and isn't the same for wind and solar? in fact, aren't the 'running' costs for a solar panel zero?
    Correct. But if the solar does not produce during peak demand, then either you need to store the energy, or you need other power stations capable of supplying peak demand.
    Now if these other power stations save money, or pollute less when turned off - like gas or coal, then there is an argument to be made for solar. If however they do not save money or pollute less when turned off, and you do not have an energy storage system, then there is simply no point building the solar plant.
  13. 14 Jun '14 12:37 / 12 edits
    Originally posted by twhitehead
    Yes, it either goes to waste or gets sent to other areas.

    [b]Agreed. But that wasn't what I was talking about because I was talking in the context of the situation of the GPP BEING capable of supplying local peak demand and/or all the energy coming from renewables.

    I don't understand that sentence. What does GPP stand for? How would GPP supply ene ...[text shortened]... ou do not have an energy storage system, then there is simply no point building the solar plant.[/b]
    What does GPP stand for?

    I already indicated that with my quote “...geothermal power plant [GPP] ...“ i.e. GPP = Geothermal Power Plant.
    Exactly my point for geothermal - yet you suggest turning it off.

    ONLY when NONE of the power is needed. And when some but less than peak power is needed, don't turn it off but power it down to reduce the GPP's power output to whatever is needed. In other words, unless you need to store some of it ready for peak demand (which you won't if the GPP's power output can supply all of the peak demand ) , keep adjusting the power output of the GPP to whatever power output is currently needed.
    My point is that there is no need to build solar and wind in the first place if the geothermal plant is already capable of supplying peak demand.

    I would agree. But, where a GPP (Geothermal Power Plant ) IS capable of supplying all of the peak demand, why have it full on EVEN at the times when there isn't peak demand?
    If peak demand is one GW ( Gigawatt ) and the GPP supplies all of that one GW at peak demand, then why have the GPP output one GW when, say, the current demand is only half of one GW? What will be done to the other half of the GW? Would that energy be wasted? Would that energy be stored even though it will never be needed? -THIS is where I am confused about what you have been suggesting.
  14. 14 Jun '14 13:09
    Originally posted by humy
    ONLY when NONE of the power is needed. And when some but less than peak power is needed, don't turn it off but power it down to reduce the GPP's power output to whatever is needed. In other words, unless you need to store some of it ready for peak demand (which you won't if the GPP's power output can supply all of the peak demand ) , keep adjusting the power output of the GPP to whatever power output is currently needed.
    And that seems a reasonable thing to do if the costs of adjusting output are lower than the cost of keeping it on full power. With solar, that is not the case, I do not know what the situation is with geothermal.

    I would agree.
    Then your OP makes no sense. You said it would complement wind and solar, but now you admit that there is no benefit to adding wind and solar.

    But, where a GPP (Geothermal Power Plant ) IS capable of supplying all of the peak demand, why have it full on EVEN at the times when there isn't peak demand?
    It all depends on costs, and whether or not that extra power can be exported to other areas. Until all coal and gas plants are shut down, it makes sense to transport that spare geothermal power to areas which depend on coal and gas because the main cost of a geothermal plant is construction, so it is most economical when kept on as much as possible (except for maintenance).

    THIS is where I am confused about what you have been suggesting.
    And I am confused about your OP which somehow fits in solar and wind. What use are they if the GPP is supplying enough energy for all needs? How do they 'complement' the GPP?
  15. Standard member DeepThought
    Losing the Thread
    14 Jun '14 13:39
    Originally posted by humy
    A more or less free form of energy and you want to switch it off some of the time?

    why would you want to extract geothermal energy out of the ground at the times when you don't need it? Better to extract it only while you need it and temporally keep it down there while you don't.

    [quote] The advantage with geothermal energy is that t ...[text shortened]... costly off-the-grid energy storage facilities although some storage would often still be needed.
    Night time electricity use in the U.K. is I believe of the order of 20GW, I doubt that a geothermal plant would satisfy that. However the alternative for the Spanish is to export their surplus power.

    Storage requires a pump, some water, a mountain, and a turbine. I don't think it is as ruinously expensive as you think.
    Better to extract it only while you need it and temporally keep it down there while you don't.
    You seem a little confused about the concept of renewable energy.