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Wind power, where the lights might never turn on.....
The realistic limits on wind power are probably much lower than scientists have suggested, according to new research, so much so that the ability of wind turbines to have any serious impact on energy policy may well be in doubt. Even if money were no object, the human race would hit Peak Wind output at a much lower level than has previously been thought.
The turbine installations would have to be very extensive and intensive for them to change large scale wind directions and speed. The major oceanic wind fields are created by equatorial to polar temperature differences modified by the Coriolis Effect. Continental wind patterns are modified by cyclonic weather pressure and temperature moderation. I doubt if wind power installations could change these planetary scale air movements.
On a more local scale extensive wind developments could and do change the effective surface roughness of the wind flow field. Wind power installations do extensive flow field modeling to study this effect in order to maximize the energy recovery of their installation. If the downwind flow fields were not affected by the turbines they would be installed right next to each other. As the air flow turbine wake is wider than the upstream flow field the air has to be moving slower downstream of the turbine. Turbines are spaced far enough apart to allow the overhead flow to reenergize the turbine wakes before the air is intercepted by the next wind turbine. At least that is supposed to be the way it works.
I can imagine a situation where the turbine installations become so extensive that the normal moving air would react to the effectively increased surface roughness and simply flow at full normal velocity well above the turbine height. This would decrease the velocity at turbine height and thus decrease the recoverable energy. I would think this effect would require hundreds of square miles of installation with many lines and rows of turbines before it became a problem.
I think we're getting into an all-or-nothing mindset again with this study. If wind farms have a peak maximum efficiency due to their effect field, simply design the system within those limits. It's still renewable energy, and when combined with other renewable energy generation methods, could still provide us with most/all of our energy needs. Even if they only provide 5% of our total energy needs, that's 5% less fossil resources required.
The issue with wind isn't the size of the resource, it's the timing of the resource. Most is available at night when demand is low. There's more than enough resource to provide 100% of our electrical needs if we could store electricity efficiently.
Agreed. Solar & Wind isn't on-demand. But conventional power systems utilize battery storage, so it's not a terrible leap to need them for an RE system. But I agree, the true limiting factor now is storage... and we defintely need improvements in that tech.
Anyway, back to overstating the potentials. Even if the wind potentials are overstated, the newly factored potentials still provide ample electricity to supply our power system (esp. a hybrid and/or distributed system).
It's the same with Solar PV. Argument that PV is inefficient because only a percentage of incident light is converted to energy... however, according to the ARS study:
Quote:
...the annual averaged efficiency of solar-cell-driven electrolysis is about 10 percent. Solar energy conversion efficiencies for crop plants are about 1 percent...
Considering that nearly everything bio-electrical & mech-electrical on Earth is currently powered by the photosynthetic reaction in plants (all meat is grass and fossil fuels are just banked condensed plants) the 9% efficiency improvement of PV over plants is certainly not "inefficient".
But, like wind, solar needs a way to store surpluses for use during peak and non-generation periods... and we're currently relying on chemical storage for that purpose (either fossil fuels or batteries). Both PV and Wind have the potential to generate more power than we could possibly use (they already power the entire planet!), we just need a way to store it so we can use it when we want it.
Since the "fuel" is free for solar and wind, the efficiency argument is really specious. Efficiency of conversion in this case affects capital costs and ultimately busbar electricity cost but the people making the efficiency argument are just raising a red herring.
On storage, we need less than people think and not matched to individual resources. Storage has its highest value used as a system resource. With a diversity of renewable resources, there is only modest need for storage. Current modelling suggest that the grid can absorb about 20% wind without the need of storage. I haven't seen studies on solar. An alternative to storage is fast response demand reduction. The smart grid will facilitate that.
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Wind power
