Germany's wind and solar power generation came to a standstill in late 2013. More than 23,000 wind turbines ran out of wind and most of the one million photovoltaic systems ran out of sunlight. For a whole week, coal nuclear and gas-powered plants generated an estimated 95 percent of Germany's electricity.

Britain has 3,500 wind turbines, but during a period of extreme cold they produced just 1.8% of UK's electricity. But, gluttons for punishment, politicians intend building more.

When electricity demand peaked at the height of the recent heatwave in Southern Australia, the total power output from the fleet of wind farms across Victoria and South Australia was almost zero. Solar panels worked at their peak for a short time during the heat of the afternoon, but waned as the sun moved on and smokiness increased.

At dinner time on any still, cold winter night, when all suburban stoves, lights, TV's and heaters need power, solar panels sit in the dark, powerless. And the idle wind turbines are probably drawing power from the grid for heating, lubrication, electro-magnets, hydraulics and start-up.

Despite the expenditure of trillions of dollars on conferences, green energy subsidies, research, carbon taxes, carbon trading, solar and wind subsidies, plant construction, additional transmission lines and back-up power, wind and solar only produce a derisory share of world energy ("zero" if rounded to the nearest whole number).

We keep hearing how "research" will solve the key green energy problems, but no amount of research can alter the fact that solar energy will always be variable, intermittent and dilute.

Even if solar panels collected 100% of the solar energy that fell on them, and no dust or snow ever covered the panels, the output is always variable and intermittent, with the rise and fall of the sun, the long night and the variable clouds, snow and dust.

Similarly the wind is variable, often too weak, sometimes too strong, and even when it is just right, there may be no demand for that surge of power. Germany has 23,000 wind turbines - they produce an average of about 17% of their installed capacity; on some days, they harvest nothing except subsidies (and they are good at that).

And crucially, both wind and solar energy are very dilute, so large areas of land are required to collect significant energy and to build the spider-web of roads and transmission lines required to connect to each other and to the grid. Solar panels rob green plants underneath of their sunlight. Wind turbines annoy neighbours with their noise, devalue their properties and slice up eagles, bats and migrating birds. These are very significant human and environmental costs never mentioned by green energy disciples and promoters.

No amount of research can change the key intermittent and dilute nature of green energy. We should stop wasting ever-increasing amounts of money on pointless research.

Even if we invented magic batteries (small with massive capacity, low cost, no energy losses and everlasting life), the green energy plants would still need to spend over 60% of the energy they generate to charge the batteries in order to produce 24/7 power.

There are places when green energy is appropriate and useful, and people should be free to use it at their own expense. But for grid power, it is not fit-for-purpose.

All of this explains why Green Germany is now using more coal than it did in 2009 and its power supply is more expensive and less reliable.

(estimates - sources vary and none reports everything).

Useful Sources:

http://www.bp.com/energyoutlook
http://www.eia.gov/totalenergy/data/annual/archive/038411.pdf