Thunberg is naïve: renewables alone is an Illusion

Thunberg is naïve: renewables alone is an Illusion

by Paul Spare
article from Friday 26, April, 2019

THE VISIT of Greta Thunberg to the UK and the other climate protests have been well publicised, but the muddled thinking and inconsistency amongst global warming campaigners will inevitably result in little tangible progress in reducing CO2 emissions.  They demand that renewable power should replace fossil fuels, but essentially, renewables are too unreliable to provide the electricity with the level of security that is essential to our society.  

The reliable option of low carbon nuclear is not acceptable to them, so coal and gas will have to be retained – which limits the scope for reducing CO2. Germany has adopted a similar policy and its emissions have hardly changed over the last 10 years.

Coming from Sweden, Greta Thunberg must be aware that their per capita CO2 emissions are the lowest of any developed country. This long-term performance is a consequence of the electricity supply being dominated for decades by nuclear power and hydro over wind and solar. This strategy has also worked in France and Switzerland so there is a clear message here for the wishful thinkers.

The two crucial areas where renewables fail are the inability to supply almost uninterrupted base-load and the inability to respond to short term demand changes.  For about 90 per cent of the year, power demand exceeds 25000 MW - 50 per cent of the winter peak value, with rock bottom base load about 20000 MW. Base-load is the underpinning generation that must be available with only the occasional hour default. Nuclear contributes about 6000 MW;  imports 3000 MW; wood burning 2500; CCGT plus coal the balance. On this macro-scale, the dependable wind contribution is very small. 

For several days, wind power may supply 35 per cent of demand but there are long periods of negligible output.  During ten days of calm weather from 4th July to 13th 2018 (not an isolated incident) output was less than 2 per cent of demand for about three days in total.  Our economy could not cope with such power failures.  Comprehensive studies of wind farm data show that for 20 per cent of the time, generated power is less than 10 per cent of nameplate capacity.

Against that ‘occasional default’ criterion, the wind power contribution is only 500 – 1000 MW.  Solar power can be considered as making zero contribution to base-load, since during the winter months it provides no power for 16 hours per day.  It performs well in the summer months, but that is the time of low demand.  Tidal power would also effectively contribute zero because of moving hours of slack water and no output.

The second requirement concerns daily demand curve.  This shows a surge every working day from 530 to 830 am usually in the range 10 – 15000 MW, but up to 20000 MW in very cold weather. Wind power, solar and tidal are not under human control and cannot be increased to meet this regular demand or any other sudden change.  In fact, wind power is often declining over the morning surge period. To prevent power cuts, despatchable power from CCGTs and some coal plants must always be available. 

One reaction might be that turbine numbers should be increased ten fold to improve the output during periods of low wind velocity. However that will bring massive additional problems.  Such turbine numbers would have to be constructed offshore to feed in from Scotland and the network periphery.

The transmission network is reaching its power handling limit in some areas of the UK because wind turbines are feeding in power at the extremities. 

The National Grid Electricity Ten Year Statement, November 2018 report identifies Scotland as at greatest risk. …… The north/south power flow could reach 15.7 GW in some scenarios. Almost three times the present maximum even with the Western HVCD line operational. From 2025, National Grid forecast that Scotland will be at a significantly higher risk for at least half the year.  Some conventional synchronous generation must stay/be constructed in Scotland to maintain year-round secure operation.

This analysis has looked at the short-term challenges. Proposals from the Climate Change Committee will multiply them.  Electric vehicle numbers are predicted to grow to millions.  Many will inevitably be charged on arrival at work. This will add many GW to the morning demand surge. However, that pales into insignificance compared with the proposal to phase out domestic gas use.  Maximum gas demand can be about 500 Million m3/day. Expressed as power, that equates to an increase of 100,000 MW over only a few hours on cold winter days – increasing electricity demand two or threefold.

In summary therefore, renewables cannot bring any low carbon salvation.  They cannot provide more than a few hundred MW of the secure, essential base-load.  They cannot respond to the daily (or twice daily) surges in demand that must be met quickly to stabilise system frequency.  Increased renewables input from Scotland and the network periphery will risk power and thermal restraints being reached across system boundaries and necessitate wholesale upgrading of the network.  They are degrading fault current detection and frequency response. 

A low carbon, secure and controllable electricity grid based on a high renewable penetration is an illusion.  Since the logical alternative of emulating the Swedish model with a large nuclear sector is being rejected, it looks like ‘business as usual’ for many years ahead.

Paul Spare CEng FEI FIMechE

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