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Why renewable energy is not enough – challenges for a UK powered by green energy


In the UK today, we need to decarbonise to avoid the potentially devastating immediate and long term effects of climate change.  The Government has set a strict target in 2017 of reducing the current level of about 300 to 100g CO2 per kWh of energy generation, 28% of all CO2 emissions, by 2050.  The  2050 target is to reduce all emissions by at least 80% of 1990 levels which will require reducing domestic emissions by at least 3% per year.  

Sustainable energy generation from renewable sources, typically solar, wind, hydro and biomass, promises to be part of the solution to reducing CO2 emissions.  Another challenge is to match energy demand with energy supply particularly when seeking sustainable energy generation.  

Energy supply: electricity generation

There has been significant progress in the UK in using renewable energy, and  about 30% of UK energy now comes from renewable sources, up from 5.9% in 2010. This is good news for decarbonising the National Grid, and a very significant milestone has been passed  in 2019. So far this year there have been 1,096 hours of “coal free” electricity generation, and only 3.5% of British electricity from coal over the last 12 months, ironically, the longest period since 1882.

In the UK we are now clearly reducing our reliance on the most polluting and, therefore, the least sustainable fuels for electricity generation.  To give you an idea how electricity is used, the electricity mix at 8am on 10th May 2019 was: –

Gas 57.6%, Nuclear 17.5%, Import 9.6%, Biomass 6.0%, Solar 4.2%, Wind 2.2% Hydro 1.6%

Storage 1.2%, Other 0.2%, and Coal 0.0%. Note that while no coal was used gas provided nearly 60%.  Wholly renewables, solar, wind and hydro only account for 8% of totally green energy production. The combined 23.5% of electricity provided by biomass and, particularly, nuclear energy have serious environmental downsides.

Total electricity generation was 37GW with a carbon of intensity of 312g CO2eq/kWh (the target for 2030 is target of 50-100g CO2e/kWh), but the UK still currently emits three times the amount of carbon necessary  to combat the worst effects of Climate Change. To achieve the goal of minimum impact, all gas power plants need to be replaced and, further, a significant increase in the amount of electricity produced by renewable energy sources is required.  Provision probably needs to double every 10 years for the next 40 years, which will be a major challenge.

However, unlike traditional coal or gas power plants, which can be turned on and off to meet demand, renewable energy is volatile and unpredictable. If there is no wind, there is no electricity, which will need to be addressed.  But firstly energy demand.

Energy Demand

The graph below shows the typical energy use of a UK home.  The standout is the large daily peaks and troughs, especially high energy use at over 700W in the early evening, dropping to just over 200W  in the early morning. The evening peak is  3½ times that of the morning.  “So what” you might think, but there are important implications for renewable energy.

The “peak problem”, the disparity between peak and trough demands requires the infrastructure for the energy generation, transformers, power lines and so on to have the capacity to meet the ‘worst case scenario’, the period of maximum power use.  These are usually short-lived periods with low demand prevailing for the rest of the day. The whole system, must be over-engineered massively and, therefore, much more expensive than required for the majority of the time.

The secondly, how best to manage peak demand.  This has a social behaviour dimension. Getting home from work, we turn on the TV, the washing machine, make a cup of tea or coffee, causing high demand.  When most energy came from fossil fuels demand was easily met: want more electricity burn more coal; but this is not so straightforward with renewables.

When demand peaks it might be calm or dark and when the sun does not shine nor the wind no electricity and little or no control.  Given the UK climate,energy demand is at its greatest in mid-winter, mostly to provide home heating. Short days and bad weather severely restrict solar energy placing great reliance on wind power, which we realise is itself variable and not wholly predictable. Hence a potential  mismatch – “the energy gap” with supply failing to meet demand. Is there a solution?

Possible Solutions: a way forward

Nuclear Energy

The massive capital cost of nuclear power plants, the raw materials, safe disposal of waste, the danger of malfunction, security and complex political and environmental considerations make the future of nuclear power uncertain. The replacement of Sizewell B for instance is en-mired in escalating costs and political problems, and proposals for a £16 billion plant in Wales and another in Cumbria have been scrapped. The decade plus time frames for planning and development, the massive costs and associated environmental problems, probably puts nuclear power outside the issues sought to be address in this article.

Over specification of renewables

Many more wind turbines and solar plants must be built to meet peak demand than are required to satisfy base loads. Wind power is the overwhelming source of renewable energy in the UK and many more on and offshore wind turbines are needed for meet future demand and there are trade-off on environmental impact against sustainability. Tidal barrages and hydro-electricity also have potential, but have had little investment to date. Local and environmental resistance to major projects will create political problems and national considerations may have to over-trump the views of the local community. While the size and efficiency of new generation turbines are increasing and relative manufacturing and unit energy production costs are falling, the traditional model of “predict and provide” will require many more units to be built than are technically needed to satisfy normal demand.  This is not the optimum use of resources.

A “smarter” way of filling the energy gap between supply and demand

Managing demand by incentivising behavioural change to allow jobs, tasks and operations in the workplace and at home to be undertaken and organised when energy demand is at its lowest. Some of this is underway in the wider transition to electric transport. Energy storage – charging batteries in the off-peak for peak use, has some potential, despite the limitations and cost of batteries.  Energy storage at Grid scale, however, is in its infancy.

Smart electrical products have growing utility and tech companies are rapidly exploring how best to allow consumers to determine their use electricity, when most convenient and at best cost using smartphones or computers. This technology is in its infancy and needs to be more user friendly and effective and, equally, energy producers need to develop ranges of green and variable tariffs to incentivise and accelerate behavioural change in consumers.


Ecopush has developed and is improving its product/system which enables consumers, using a smartphone or computer, to control and programme their energy use flexibly.  It is simple and convenient and will enable them to obtain the lowest tariffs, use green energy and make the best fit between supply and demand. The system also has the potential to make a contribution to national decarbonisation and to help reduce the UK’s impact on climate change .

If you would like more information contact us at –

Our smart plug is available to buy at





[5] Tackling climate change

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