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Tag Archives: grid balancing

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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Firm power parity metric

By Dave Elliott

A paper from Imperial College proposes a new conceptual framework for understanding competition in electricity markets that include variable input but marginal cost renewables. Noting that one of the primary drivers for consumers to switch from grid-supplied electricity to self-generated electricity (e.g. home roof-top PV with batteries) is cost savings, the researchers constructed a model that forecasts when going-it-alone ‘grid defection’ by consumers may become widespread. In reality, few domestic consumers in the UK are likely to want to go entirely off grid. At least not for some time. Grid links are   needed and useful for backup, e.g. for when there has not been enough sunshine for a while and consumers’ batteries are discharged, and also to sell any surplus power they can generate, beyond what they can store. However, the grid defection analysis is still a useful conceptual exercise, not least since it gives us some idea of the cost of balancing/backing up variable renewables. And, in time, some users may want to try the off grid option. (more…)

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European wind co-operation could benefit all

By Dave Elliott

‘European cooperation could provide more stable wind power’. So says a new Imperial College study. Co-author Dr Iain Staffell, from Imperial’s Centre for Environmental Policy, said: ‘Some weather regimes are characterised by storms rolling in from the Atlantic bringing high winds to northwest or southwest Europe, but these are accompanied by calm conditions in the east. Other regimes see calmer weather from the Atlantic and a huge drop in wind production in Germany, the British Isles and Spain. But at the same time, wind speeds consistently increase in southeast Europe, and this is why countries such as Greece could act as a valuable counterbalance to Europe’s current wind farms.’

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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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The last word on the cost of balancing renewables

By Dave Elliott

The UK Energy Research Centre (UKERC) has produced an update to its 2006 report that had looked at the costs and impacts of using ‘intermittent’ electricity from renewables such as wind and solar. The 2006 study had only examined impacts with up to a 20% input, but the UKERC researchers now say that, even at the higher levels we are now expecting, it was still the case that the costs of balancing renewables could be low. However, they warned that, unless ‘urgent’ action was taken by the government to boost grid flexibility, the costs of adding renewables in future will be ‘much higher than they need to be’.

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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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German energy balancing

By Dave Elliott

Germany is in the lead globally with its ambitious renewable energy programme, already supplying over 32% of its electricity and aiming for 80% by 2050.  At present, Germany’s 1.5 million photovoltaic solar installations have a generation capacity of over 40GW, four times the remaining 10.8 GW base-load nuclear fleet that is being decommissioned in stages between the end of 2017 and 2022. PV can be well matched to day-time peak demand in Germany, which is why it has challenged gas peaking plant in this market.  However, due to its low load factor (10-15%, compared to 70-80% or more for nuclear), solar PV generation only delivers around 940 equivalent full-load hours of electricity per year, so in 2015 its high capacity only met around 7.5% of German electricity demand, compared to 14% for nuclear generation. That’s why some think it is not the best option to expand for the future – it’s expensive for relatively low levels of actual output. (more…)

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EU e-Highway 2050

By Dave Elliott

A recent report says that long distance transmission grids offer many advantages including enhanced cross-EU trade and grid balancing opportunities, enabling high levels of renewables to be used while reducing curtailment of occasional surpluses. The European Network of Transmission System Operators for Electricity group had already addressed the development of the pan-EU electricity transmission network up to 2030 in a Ten-Year Network Development Plan. Starting with that, the e-Highway 2050 research and innovation project has now looked to 2050: it deals with the transition paths for the whole power system, with a focus on the transmission network, to support the European Union in reaching a low carbon economy by 2050.

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Storage will cut renewable balancing cost

By Dave Elliott

Energy storage is all the rage at the moment, with a Daily Telegraph columnist even claiming that ‘cutting-edge research into cheap and clean forms of electricity storage is moving so fast that we may never again need to build 20th Century power plants in this country, let alone a nuclear white elephant such as Hinkley Point’.

And it could be cheap. The recent Carbon Trust/Imperial College report on energy storage says that ‘the UK can realise significant cost savings if market arrangements for the electricity system allow for an efficient deployment and use of energy storage, alongside other flexibility options such as demand response and interconnectors’. It claims that many of the changes needed ‘are likely to be cost neutral and require no additional funding from the government’.

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