Let’s do a little calculation concerning the ability of renewable sources of energy to generate and expand itself. A reasonable assumption is an EROEI value for a wind turbine of 20. This means that during the 25-30 years life span, this windturbine can generate 20 times as much energy as it costs to build said winturbine. How much time would it take to satisfy the world’s current energy needs (consumption rather) with wind power, based on a single windturbine, reproducing itself? Assume we are dealing with a windturbine of 5 MW and that the world’s energy consumption is 12,000 MTOE.
Assuming a load factor of 33%, the wind turbine wil generate 24 * 365 * 5,000,000 * 0.33 = 14.5 million kwh or 14,500 megawatt hours per annum.
Converting 12,000 MTOE in kwh:
1 toe = 11.63 megawatt hours
1 mtoe = 11.63 * 1,000,000 megawatt hours
12,000 mtoe = 12,000 * 11.63 * 1,000,000 megawatt hours = 139560000000 megawatt hours
The number of 5 MW windturbines necessary to generate this amount of energy is 139560000000 / 14,500 = 9.6 million
Now let’s calculate how much time it would cost for a single 5 MW windturbine to multiply itself to this number (EROEI 20):
20 – 25 years
400 – 50 years
8,000 – 75 years
160,000 – 100 years
3,200,000 – 125 years
So we need a little more than 125 years.
Fortunately we do not have to start from 1 windturbine, currently 275 GW windpower already is installed or 275,000 MW or 55,000 5 MW turbines. There we go again:
EROEI 20 * 55,000 turbines = 1.1 million – 25 years
9.6 million – ca. 40 years
We can of course add the already installed solar base (with lower EROEI than wind), which brightens the picture a little. Conclusion: if we use all the energy generated by wind turbines to build new wind turbines and nothing else, than it would take us ca. 40 years to accomplish setting up a global windpower energy base that could replace all current sources of energy. But if we consider that according to the Energy Watch Group, global peak energy will arrive by 2018 and gradually decline afterwards, than it becomes immediately clear that there is no energy capacity left for setting up a new energy base and at the same time maintain current energy consumption levels. And the longer we wait with facing some very hard truths, the more devastating the coming crunch (crash?) will be. Although there is no doubt about the long term potential of renewable energy, we are simply too late for a smooth transition. We should have listened and acted upon the findings of the Club of Rome 40 years ago. We did not (sufficiently) and choose to waste the energy capital on unhindered economic expansion, now in a 7+ billion me-too world and 9 billion soon. Timber!!!
Btw: refining the very simple calculation above into a fullfledged computer simulation model could be very usefull as an instrument of substantiating an energy policy.