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Tag Archives: variable renewables

Can nuclear be used to balance renewables?

By Dave Elliott

Nuclear plants are designed to run flat out, in part to recoup their large construction costs. Their output can be varied a bit, but this entails thermal stresses and potential safety issues with the build up of active xenon gas that is released when fission reactions are reduced. It needs time to decay. That limits how often and how quickly the plant can be ramped down and then back up so as to match changes in energy demand (“load following”) and the varying output of renewables. So basically nuclear plants are inflexible. Do they have any role for balancing variable renewables?  (more…)

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Rotatiload! Synchronous inertia and frequency stability

By Dave Elliott

Power engineers worry that, as more renewables are added to the grid, replacing old coal, gas and nuclear plants, we will loose lock-step AC synchronous system stability, since the latter had large heavy rotating turbo-generators which provided system inertia against frequency perturbations. The big plants’ rotational inertia acts as a buffer to grid frequency changes, and to varying supply and inductive loads. However, PV solar has no rotational inertia, and wind turbines not much, though direct drive machines can provide some. With more renewables on the grid it will become more of an issue: https://arxiv.org/pdf/1312.6435.pdf

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Do batteries and EVs ‘change everything’?

By Dave Elliott

You almost need to draw a line under what has come before and start again. There is no doubt that batteries completely and utterly metamorphose the market in that they make the uncontrollable controllable. It makes the arguments against renewable energy fall away’. Nick Boyle, founder of Europe’s largest solar operator, Lightsource.

And batteries in electric vehicles (EVs) take it to a new level, with IRENA claiming that ‘EVs can be used to enable a higher share of variable renewable energy in the power system’. So does all this add up to technological revolution? (more…)

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Transitional green power issues – sectorial conflicts

By Dave Elliott

It is often said that, whereas it should be possible to meet electricity needs from renewables, heating is harder and transport harder still. While wind and solar and other renewables can generate electricity and replace the use of fossil plants, heating and vehicle transport use of fossil fuels are harder to replace. Except possibly by the use of renewable electricity. Although some disagree, there should be enough renewable electricity output to meet all energy needs in time. However, even enthusiasts accept that there may not be enough to go around initially. So there may be sectorial conflicts at some stages.

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100% Renewables? Mostly nonsense!

by Dave Elliott

So says a new study by a group of mostly pro-nuclear academics, who look critically at some of the many ‘100% renewables’ global or regional energy scenarios that have emerged in recent years. 24 were deemed to have forecast regional, national or global energy requirements in sufficient detail to be considered potentially credible but, on inspection, none were considered to have provided convincing evidence that basic feasibility criteria, in relation to energy supply reliability, grids and balancing, could be met. (more…)

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ICL and UCL on renewable balancing

By Dave Elliott

Several academic studies have indicated that balancing variable renewables need not be expensive. An authoritative review of over 200 studies by UK Energy Research Centre in 2006 concluded: ‘Intermittency costs in Britain are of the order of £5 to £8/MWh, made up of £2 to £3/MWh from short-run balancing costs and £3 to £5/MWh from the cost of maintaining a higher system margin’.  

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WEC on renewables – a glass half empty!                                 

By Dave Elliott

The London-based World Energy Council (WEC) and the Paris-based International Energy Agency (IEA) both regularly produce global energy scenarios. While they both still back nuclear and see fossil fuels as continuing to play a major role, these days they also increasingly identify renewables as a major player. However, the IEA tends to be more assertive in its promotion of renewables and efficiency, while WEC is usually more cautious.

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Renewables and nuclear both have problems

By Dave Elliott

Nuclear and renewables continue to be seen as rivals, with, as part of the debate, studies emerging that address their problems. A study by the Energy Institute at University College London says the UK’s proposed Hinkley Point C nuclear plant will be obsolete by the time it starts up (possibly EDF says in 2025/6) since it will be in competition with cheaper low carbon options, including wind and PV solar. These sources are variable, but at times they will produce all the electricity needed, leaving no room for Hinkley unless their output is curtailed. At other times they will only make small contributions, but the UCL team calculates that only around 20GW of ‘firm’ inputs like Hinkley will be needed to operate for more than half the year by 2030 to meet the gaps and peak demand. And there are cheaper more flexible balancing options for this than Hinkley.

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Non-nuclear UK energy futures

By Dave Elliott

Several non-nuclear energy scenarios for the UK have been produced recently, as I have reported in an earlier post, some of them in response to the perceived need for a ‘Plan B’, as an alternative to the Hinkley EPR project. Some new ones include a submission to the government by TASC, the Together Against Sizewell C campaign group, and a study by developer Green Hedge. They may have lost the first battle, with Hinkley going ahead, but their analysis remains relevant for whatever happens next e.g. in relation to the next projects, which include another EDF EPR at Sizewell. (more…)

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Balancing green power

By Dave Elliott

If the use of renewables is to expand further, ways have to be found of compensating for their variability. Fortunately there are many, as I have outlined in a new book ‘Balancing green power’, produced for the Institute of Physics. It sets out to show how, taken together, they can help balance grid systems as increasing amounts of renewable capacity is added, helping to avoid wasteful curtailment of excess output and minimising the cost of grid balancing. The options include flexible generation plants, energy storage systems, smart grid demand management and supergrid imports and exports.

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