Yes, the demand is as ever on the increase.
No, the Renewables are (not yet) bridging the gap
We had a reasonably mild winter this year.
Next year, we may not be so lucky.
Our proble (one of our many problems) is that our
existing Nuke load is due for decommissioning in
the next decade, our Coal Fired load will be hit
hard by Emissions Regulations. In the 80's and
90's we made the 'dash for gas' to replace Coal
Fired Generation. Seemed like a good idea at the t
time...

The first, easy and immediate thing we could do is
a massive education program for conservation.
Probably more than 20% of base load is simply
wasted. It would need to start in Schools.
It would need to start now. In its self, it will
make a modest contribution, but it is an intrisically good thing to do and a start in the right direction.

The first problem will be getting 65.5 million
people to understand the second law of thermodynamics

Over 60's know all about conservation. Even some over
over 40's!

George Monbiot came to much the same conclusion  He is certainly no fan of nuclear power but in doing some very  rough sums he came to the conclusion that even with a 40% reduction in demand by increased efficiency and all the wind wave tide and biomass renewables we could install in the UK they will still be able to supply less than half the electrical generating power we need by 2050. This leaves the only non-environmentally destructive stopgaps of fossil fuels with carbon sequestration and nuclear fission .

As a broad brush estimate I think I agree with him but there are some points I would question. His assumption that we will solve the mass storage problem economically with 50% round trip efficiency by 2030 seems very optimistic to me.

His suggestion of generating hydrogen to burn in turbines does not seem that hopeful. Hydrogen generation by electrolysis or thermally such as by the sulphur-iodine process struggles to make 80% efficiency when all the ancillary  processes such as AC/DC conversion, pumping, compressing and cooling are taken into account. Even combined cycle gas/steam turbines struggle to make 45% efficiency overall of chemical energy to electricity on the grid. This gives 35% round trip efficiency.

 Batteries, that he also suggests, are even less promising. Lead acid batteries are not the best we can do but they are used for smoothing out small solar systems and can give some idea of the huge advances that would need to be made to use batteries on national grid level. A 12V 38Ahr lead acid battery costs about £100. It can store 0.4kWhr. At a wholesale price for electricity of about £0.05/kWhr that is  £0.02 worth of electricity. At a discharge depth of 50% you will be lucky to get 800 charge discharge cycles before the battery is almost dead. That means that during its service life it will store 160kWhr. That is £8 of electricity stored before having to replace it with another £100 battery. To smooth out the daily weekly and annual peaks and troughs of 25GW system dominated by wind, wave and solar generation will need storage at a wild guess of 2000GWhr. (11% below mean for a month) That is equivalent to 5 billion of our £100 car batteries that would need replacing every few years.

I know that a real system would use better batteries such as lithium ion and there would be economies of scale but to rely on technology delivering orders of magnitude improvements is to fall into the same Pollyanna optimism that we accuse opponents of peak oil theory of having.

Other schemes are also doubtful. We do not have the space in this country to  provide pumped storage schemes of sufficient size.  A 1000 square kilometre lake  20 metres deep 300 metres above the lower water source at 90% efficiency will store 15GWhr of energy.  Would anyone like to suggest 130 locations in the UK where we could build such schemes to store our 2000GWhr?

Compressed air does not have a very good round trip efficiency and we do not have all that many air tight underground structures such as salt domes to store the compressed air.

On the other hand I think George Monbiot dismisses Solar energy to easily. Its intermittency is worse than wind but not that much. If you can solve the storage problem you solve it for solar as well as wind. Concentrator systems using multi-junction cells have achieved 39% conversion efficiency at over 200 concentration factors with tiny 2 to 3 mm cells spread out so that you only have to cover a fraction of a percent of the sunlit area with each cell behind a cheap plastic lens. They do have to have a tracking system but that is not impossible. On such system installed in Spain recovered the energy of construction in 6 to 8 months. I think Solar has a greater potential for several fold cost reductions than does wind.

The bottom line of all this is that we should economise our energy use as far as we can, should massively increase our installation of renewable energy system but should expect to hit a law of diminishing returns when we get to several tens of percent of the total load and we will have to rely on non-renewable energy for a substantial part of our electricity.

If we can hold out for 60 years or so nuclear fusion may come to the rescue.