Here's another energy philosophy; what works is already doing so and what doesn't yet work is pure speculation. Some critical factors are overlooked with granite geothermal. First is the low thermodynamic efficiency with a temperature difference of say 200C, less than half that of other thermal plant. Each time a hole is drilled into the granite to find a new hot spot or because a water channel isn't working that incurs a large energy debt equivalent to hundreds of kilowatt hours. Budget on at least half a million dollars per kilometre for high voltage direct current transmission lines in the outback. Note also the wet froth from these drill holes contains hazardous radon from uranium in the granite. Therefore the water has to be in a closed cycle. In fact the heat flux from hot granite is minuscule compared to solar radiation on the surface. It would probably be easier to store solar energy overnight and bring the facilities a lot closer to town.

I'd give this geothermal revolution a couple of years to prove itself then look elsewhere. Ironically it's kind of the reverse of that other furphy, geosequestration of coal emissions.

Development of hot-rock power generation is already proceeding. There is no need for a change to the economic rules to support it.

The idea of adding solar heaters to make the resource last longer is nothing more a thinly veiled attempt to make solar power look more viable than it is. Making the resource last longer is almost worthless from an economic standpoint.

We have no viable way of storing energy, so our options for exporting energy generated from hot-rocks is limited to those markets that could be reached economically by power transmission line. It's likely that there are none.

The value of tagged money depends on the demand for it. It's simplistic to suggest that there would be no cost to the initial recipient of the tagged money, because they would probably find that they had to sell it at a discount, there being insufficient demand for investment in renewables on anything like the scale required.

These ‘hot rocks’ are part of the natural environment. I wonder if anyone has looked into the consequences of human fiddling with this ‘resource’.

According to the CSIRO’s Peter Metabe, the world will be dependent on fossil fuels for at least the next 20 years.

Oil, gas and coal currently supply 86% of the world’s energy; wind, solar and geo-thermal less than 1/%.

Even if the energy options could be increased by 10 to 20 times (how long would that take?), renewable energy will never meet the growing demand.

And yet, people like Green Senator Milne say that we can switch to renewable energy now for all our needs!

Amazing how Mr Right (aptly named I think) can pour doubt on anything that might cause change. It seems he's quite nervous about change.

And Sylvia, on solar energy, I think you'll find that there are now batteries that store store power reasonably well and that this technology is only improving. In fact, one look at California and you'll find Australian solar thermal technology providing very large inputs to (I think) San Diego, if memory serves correctly, about 15%.

In Perth, where I am lucky to live, we have plenty of hot rocks in the perfect places to provide geothermal energy for the city, plenty of sunshine to utilise solar-thermal, and a regular wind source in summer when energy usage is highest. Add to that a trial of tidal power off Fremantle and it is clear that our reliance on coal and gas could be hugely reduced if the will was there along with only a fraction of the investment currently given to older and less efficient technologies. And even wth gas, the use of combined heat power stations would reduce the waste of power that our current technologies allow, particualarly coal-fired power stations. This is technology that was used over 100 years ago and was lost with the advent of coal, and yet it works far better. Check out what Woking Council did in the UK. They ended up selling power into the grid.

Nay-sayers about these new technologies are simply clinging on to what they know, petrified of change, and unable to show any innovation themselves.

"These ‘hot rocks’ are part of the natural environment. I wonder if anyone has looked into the consequences of human fiddling with this ‘resource’."

The irony is that the only way anyone will find out is if they try it! And they probably won't know for decades if in fact it does make a change.

Basically, the worst that can happen is that the granite rocks will cool down. Whether that will affect us on the surface of the planet is a moot point. Most unlikely I would think.

The biggest problem is likely to be the degree of fracturing of the granite. If it's too great, the injected water turns to steam, escapes down the cracks and is lost to the circulation process. This would kill the idea quicker than anything else.

Phil,

I think you'll find that the battery technology is still at a point where it could not conceivable be used as a way of transporting the energy output from a power station. The highest energy density battery I can find is Lithium Ion, at about 160kWh per tonne. That is, a one tonne battery stores energy worth about $10 wholesale. The output from a 100MW power station would require the movement of 15,000 tonnes of battery per day to the destination market. This is completely outside the realms of plausibility, and nothing short of a couple of orders of magnitude improvement in batteries (not going to happen in our lifetime, and probably never) would change that.

There's no question that things like solar thermal power generators can be built, and they do get built when normal economic rules are ignored(i.e., they're subsidised by governments, either directly with cash, or indirectly with "renewable energy certificates"). Their cost can even be (and usually is) fudged downwards by discounting the capacity required elsewhere in the system to deal with periods of overcast weather. But in any case, attaching one to a hot-rocks generator would make no commercial sense, because it would provide no return at all on investment until the hot-rock resource would otherwise be depleted. Since that would be decades away the net present value of the future return would be next to nothing.