"The basis of geothermal energy is very different from that of ground source heat pumps"
Well it is but it isn't. :-)
My hometown of Klamath Falls, OR, pioneered direct use of geothermal heat for buildings, for de-icing roads and sidewalks and numerous projects conventional, exotic and some crackpot.
But everybody knew the geothermal brines were too cool to generate electricity.
But now they do.
The most neglected of all geothermal power generation and yet the most rewarding is low temperature.
From Lightning Dock, NM's, geothermal complex to our Gulf Coast oil wells being used for co-generation of power one might see a very green future if they will just look.
What is the cost of using an abandoned oil or gas well for geothermal power?
As you surely know, Leslie, it's a trick question since numerous low cost, low risk uses of geothermal heat that have been badly neglected for many decades are being restarted.
IMHO the diversion of resources to the high-risk, speculative hot dry rock research by engineers at MIT who had little or no knowledge of geothermal power has been a very predictable disaster similar to Japan planning an armada of solar satellites while a second nuclear holocaust was getting warmed up to show its hideous self.
Can be useful for people to use their heads for something besides a hat rack. :-}
"Geothermal has to be closed loop to be clean"
This gives a whole new meaning to imaginary numbers. Brian's Law would prevent the sequestering of carbon from polluted surface waters, the "mining" of desperately needed minerals from geothermal brines, etc., while decrying the fierce threat to the planet from mini-quakes that may be detectable by only the most sensitive instruments.
Seeking ultimate purity wiped out the Shakers and would do the same to all humans if carried to Brian's extreme. Although we have the great majority of our antique sales from primitives, we have never fully appreciated the beauty of Shaker furniture that Mark Twain found almost as stiff and unlovable as the Shakers themselves.
To each his own I guess.
"I am not sure why Terry is opposed to research into a major new source of dependable power."
I am not against research into much of anything. That was my professional life.
I am most certainly not against research into HDR [Hot Dry Rock technology] or its renamed EGS but going balls-out into unproven technology while fully proven and wonderfully productive geothermal technology is starved for funding is mindless.
EGS technology has a long, long history of failure much like antisense and peaceful uses of nuclear fusion power. Money continues to pour into all three because of the spectacular payoff possible. but only EGS beggars the associated technology and is promoted primarily by amateurs in the field.
Of course we can get to 100% renewables but we can't do it with expensive intermittents (or even cheap as many foolishly believe them to be).
Baseload renewables are the cheapest, greenest, by far the most plentiful energy sources on earth. We would rather stare at the sun and destroy our vision and possibly life on the planet.
"Geothermal using air cooling looses efficiency in the middle of the summer when needed the most"
You never heard of geothermal heating and air conditioning?
Direct uses of geothermal are ancient and include even evidence that inhabitants of the Americas were using geothermal heat for cooking some 12,000 years ago.
While most geothermal power plants use water instead of air for a heat sink, even there the temperature differential decreases in summer but that is hardly the same as the wind and sun quitting altogether.
"it is not necessary for renewables to provide 100.00% of the energy we need"
Of course. It is also not necessary for life on the planet to persist long term.
Small bits of evidence from our solar system suggest there may have been life on other planets though for now the are now only dubious hints.
Fact is our planet continues to warm and species continue to be destroyed as we continue to pour greenhouse gases into the atmosphere while polluting our land and waters.
We need not be green at all. We can even choose to become extinct. Dosen't seem intelligent to me but I am biased.
"Why do people still harp on the intermittent nature of solar and wind? This has been address many place..."
What is needed is actual solutions, not fanciful, imaginary dreams.
My favorite example is Japan actually planning an armada of solar satellites to replace the fossil and nuclear-fueled power plants. The nukes were brewing up another holocaust of course while the plans to zap power down to earthlings from space was seriously proposed decades earlier in another crisis but no one knows how to do it.
"The same reserve generators base load needs, works just fine for intermittent renewables"
That wouldn't even pass muster in Alice's Wonderland. The earth's heat doesn't increase or diminish with the rotation of the earth and changes in it's orbit. Availability of waste is constant - were it not so. The tidal pull of the moon will continue until the moon disintegrates, flies away or crashes into the earth.
But denialists never listen do you, Brian?
"I can't see how e-cars will quickly replace IC engines with current technology"
Don't need to.
The answer has been around since the 19th Century when Mark Twain wrote of the Trans-Egypt Railroad using mummies for fuel.
While the usual suspects busy themselves calling Twain a liar trying to be funny [Twain did try to be funny a lot], they ignore crematoriums this very day generating electricity with the dearly beloved.
E-cars are another tragic departure from real solutions rather than even a band-aid on a cancer.
"The E-car itself is a reality, but with its current energy source (a battery only), yes, then the IC engen will still be with us for a long time to come."
Not if we are able to correct stupid blunders.
When the imaginary Creator made man in his own image, he created a mess because the Big Idiot forgot about the better half.
Infernal internal combustion may have to serve men and horses for now but there is no reason faulty design for transportation must continue one day longer than necessary. Batteries are worse.
"I could go on for quite some time pointing out how much spin there is in this article.... "
And who would listen to you, Steven?
Even Mark Twain's "lies, damn lies and statistics" just gets a chuckle without learning.
Thank you for trying.