Dude... who is proposing that solar + wind alone can carry the grid?
You wrote that wind and solar compliment each other very well. I showed that they do not.
What point are you failing to get at?
- We should stop installing wind and solar?
- We should pay ~twice as much for nuclear?
- Or do you enjoy stating the obvious point that we need storage... in a really weird round about way...
I am trying to establish the facts we need to be able to get an idea of the cost of the grid you propose.
The ENERGY... sorry... the energy is there... you just need to capture it and disperse it as needed and/or consume it when available...
I'm aware that the energy is there, but the fact that there are vast amounts of energy out there is actually utterly irrelevant. The relevant question is whether it's possible to capture and tame it so it can be used to power society, and that is not obvious at all. If an energy generation system is to be useful, it needs to produce several times more energy than we spend building, maintaining and operating it. Those who have studied EROI and it's impact on society seem to think that an EROI of about 10:1 is required to keep society running. Otherwise, we will be spending so much effort building and maintaining energy systems that we don't have enough time for other activities. And it might be that nuclear power does not seem so expensive after all, if we can put some numbers to this nebulous "ENOUGH" bit, even if the EROI of a system based on wind and solar turns out to be sufficiently high to work in theory.
Anyway, before we can estimate the storage system, we need to figure out how other possible components might help.
The basic problem with demand response and V2G is that there are limits to how long you can ask people to wait, otherwise the system rapidly loses its usefulness. Would I be willing to sell power from my Model S to the grid? Sure, if I get paid sufficently well for the service. But I need the car - that's why I paid a heap of hard earned cash for it. So if they propose that I sell my energy without being able to get it back for a week, my answer is "no". I'd be hatching schemes to power my fridge with that energy instead, so I have something to eat when transportation breaks down.
It's the same thing with fridges, water heaters, aluminium smelters, you name it. Time shift demand a few hours? OK. Time shift for a week? No way. So demand response doesn't reduce the required size of the storage system at all. It will probably help reduce day to day losses and wear in the storage system, though.
Hydro is great, when you happen to have it. Many places don't. It does have serious environmental costs, but in my opinion they are a much lesser evil compared to fossil fuels. 16 % of the world's electricity is from hydro. I think it's unlikely to increase its share. The industrialized countries have already built all the hydro they can, and in developing countries, consumption is rising.
Many people think geothermal is a large renewable energy source. It isn't, except in some very rare hotspots, like Iceland. See
Ch 16 Page 96: Sustainable Energy - without the hot air | David MacKay. Geothermal energy can safely be ignored.
Biomass is a dispatchable, renewable energy source. However, it's very limited. Even with second generation biofuels, the growth rate of plants is just too slow. All biofuel we can get our hands on will be needed for aviation and long haul transportation. In fact, aviation will probably require all of it, so we'll have to think of something else for trucks, ships and trains. See "solar biomass" here:
Ch 6 Page 42: Sustainable Energy - without the hot air | David MacKay. There are also environmental costs to industrializing all plant growth.
There is one more renewable energy source that is actually fully dispatchable - ocean tides. See MacKay for a British estimate. That estimate is probably much better than the world average, because Britain has a lot of tide which is relatively easy to harvest. MacKay calculates that tidal energy could conceivably meet about 5 % of Britain's total energy needs, but this requires country-sized installations. Let's assume that 5 % of electricity demand is achievable for the rest of the world. I think that's wildly optimistic.
Finally, there is wave power. Wave power is especially useful because it will almost certainly last for a few days after the wind dies down, so it's slightly out of phase with wind. It's also fairly energy dense, so it can relatively easily be harvested. However, there is very little coastline per person, and only coastlines downwind of a couple of thousand km of open ocean can be used. MacKay's very ambitious number works out to about 2 % of British energy demand, and Britain has a truly world-class wave resource. Let's put the world average at 0.4 % and round down.
To summarize:
Grid integration doesn't help.
Solar plus wind is no better than either of them alone.
Demand response: Doesn't work at the required time scale.
Hydro: Works very well, it's a shame there's so little of it.
Geothermal has a vanishingly small potential.
Biomass is needed for transportation.
Tidal energy can make a small, but real contribution.
Wave energy has a potential almost large enough to bother counting.
All the rest will have to come from the storage system.
To estimate cost we need to determine the required power and capacity of the storage system. The numbers seem to indicate that in an average country, it will have to be able to handle about 80 % of peak power demand, and to avoid losing energy it needs to be able to recharge at a much higher rate. Capacity and cost will have to wait for another post.
