Anyone who spends any time around the green business movement will have become used to being asked one question more than any other.
In essence it boils down to, "What technology is going to save us?", although if your questioner is of a more mercenary bent it can also be phrased as "Where should I invest my money?"
Now if I knew the answer to this question I would not be sitting here and would instead be trying to decide whether it is a touch too ostentatious to have a fountain installed in my land that spouts actual money, while simultaneously mulling which Premiership football team to buy.
However, while the truism that there is no silver bullet and a myriad of green technologies will be required remains as valid as ever, I am increasingly convinced that one area could have a critical role to play in making renewable energy feasible on the scale that it is required – and what's more it is a field that until now has remained largely under the radar of both investors and the media.
It is the oh so glamorous field of electricity transmission.
The renewable energy challenge has never been one of potential capacity, and nor for that matter has it been one of cost - it has always been about transmission.
This was hammered home to me last week on a press trip to Iceland, a country that some geologists believe is sitting on top of enough geothermal energy to power the whole of the northern hemisphere.
The energy is cheap, relatively easy to access and emission free, the only problem is that it is being generated in a country that is a very, very long way from anywhere. If we could only transmit, or even transport the energy, in an efficient manner we would instantly have the answer to many of our energy and climate problems.
This self same transmission issue emerges as the biggest stumbling block wherever you find huge potential reserves of renewable energy.
Several studies a couple of years ago from the German Aerospace Centre and a group of researchers called the Trans-Mediterranean Renewable Energy Cooperation suggested that installing concentrated solar power systems over just 0.3 per cent of the deserts in the Middle East and North Africa would meet all the current and future energy needs of both the Middle East and the EU.
Or to put it another way a little over one per cent of the Sahara could power the entire planet.
Progress is being made to make such thermal power systems cost effective and storage systems are also being developed that advocates reckon could save the problem of the sun setting each night. All of which means that again the only fly in the ointment is getting the energy from the deserts to the population centres where it is needed.
Tidal and offshore wind power also face the same problem on a smaller scale with the lower energy yields involved being compensated by the fact that transmission over a few nautical miles to the mainland is considerably easier than transmitting power across the thousands of miles from Reykjavik to London.
The simple truth is that if we can solve the problem of long distance energy transmission we have the missing piece of the jigsaw that makes the development of a genuine renewable energy economy if not simple exactly then certainly much simpler.
Now I will freely admit that I did not pay enough attention in Physics classes to draw any conclusions on the chances of this missing piece ever being found, but there is growing numbers of engineers who reckon that improvements in long distance high voltage direct current (HVDC) power cables could hold the answer.
These DC cables are currently much more expensive than the AC cables that underpin our national grid, but they are falling in price and unlike AC cables the amount of energy lost does not increase with distance, meaning they could feasibly allow electricity to be efficiently transmitted over thousands of miles.
It is worth noting that there are some who would argue you will need to pretty much rewrite the laws of physics to make such long range transmissions possible. But then again, if they are right then the vision of global clean energy hubs providing cheap reliable renewable electricity could be become a reality.
In the meantime, any industry that requires plenty of energy but few employees would be worth considering the old idiom about Mohammed and the mountain.
With energy costs soaring and concern over carbon emissions mounting it will make increasing sense for those industries that can relocate operations to consider getting as close as physically possible to the green energy hubs that can provide them with clean, reliable, cheap and carbon tax free power.
It is a concept that the Icelandic government is buying into with its support for the aluminium smelting industry and its work with companies such as Data Islandia and Hitachi Data Systems to encourage firms to shift their power hungry data centres to the country. It is also a model the governments of North Africa and any other country with a potential abundance of green energy would also be wise to emulate.
Meanwhile, the rest of us should sit back and hope the laws of physics aren't as rigid as some people think and that long distance energy transmission can one day become a reality.