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Tag Archives: variabilty intermittencty

Set the controls for the heart of the Sun

By Dave Elliott

A report from Carbon Tracker and the Grantham Institute says that by 2050 solar PV could supply 29% of all global electricity. Its 2050 scenario still has a lot of nuclear in it, supplying about the same as PV, but not much wind (about 7%). That’s a bit odd, especially since the report indicates that onshore wind is currently cheaper in capital cost terms than either nuclear or PV. That stays true up to 2050 on its baseline scenario. But in its lower cost prediction, it sees PV undercutting all by 2050 – falling to M$390-643/GW, about a tenth of its rather low estimate for the current (and future) cost of nuclear (M$3706-4200/GW) and also much cheaper than the baseline capital costs for onshore wind (M$1640/GW) and offshore wind (M$2970/GW) by 2050. That does ignore the likelihood that wind costs may fall faster too and, given the low capacity factor for PV, in order to get to 29% of total output, they say 65% of global generation capacity would have to be PV by 2050 – around 10TW!

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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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Grid Integration of Renewable Energy

By Dave Elliott

Eric Martinot has been one of the key people behind the indispensable annual REN21 Renewable Energy Network publications reviewing the state of play with renewables globally: see  The latest one says renewables now supply around 24% of global electricity. Martinot has also taken time out to look in detail at renewable integration issues, and this work has led to some excellent publications, including a useful non-technical overview ‘Grid Integration of Renewable Energy – Flexibility, Innovation, Experience’ for the Annual Review of Environment and Resources 2016 (February 2016). It focusses on the concept of flexibility, which it sees as vital for balancing variable renewables, including small continual changes, sudden large swings in availability, requiring rapid ramp-up of backup plants or other balancing measures, as well as for occasional longer periods of low input.

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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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Renewable Integration – a view from Germany

By Dave Elliott

High shares of wind and solar power transform the entire power system and can lead to additional system integration and back-up costs aside from building the power plants themselves. A new background paper from Agora Energiewende examines these dynamics and concludes that, not only are the direct integration/balancing costs low, but so are the controversial indirect costs associated with the variable utilization, in balancing mode, of conventional plant – as long as the power system becomes considerably more flexible.

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Energy system integration costs cut

By Dave Elliott

Imperial College London and the NERA consultancy have produced studies of energy system integration costs and grid balancing options for the government’s advisory Committee on Climate Change. They focus on flexible generation and backup systems and conclude that ‘flexibility can significantly reduce the integration cost of intermittent renewables, to the point where their whole-system cost makes them a more attractive expansion option than CCS and/or nuclear’.

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Small modular nuclear – is small beautiful?

By Dave Elliott

A new report ‘The role for nuclear within a low carbon energy system’ from the Energy Technologies Institute, claims that the UK could have 50GW of nuclear power plants by 2050, including Small Modular Reactors (SMRs). Although it says, due to basic economies of construction and operational scale, ‘large reactors are best suited for baseload electricity production’, it notes that, based on using existing sites, there is ‘an upper capacity limit in England and Wales to 2050 from site availability of around 35 GWe’, and it could be less (e.g. if CCS plants need some of the sites). However, there could be more room for small nuclear plants (under 300kW) on new sites, at least 21GW and in theory up to 63GW.

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Balancing variable renewables- capacity markets, smart grids or super grids?

By Dave Elliott

The previous few posts have looked at the state of play with renewables in some key countries. In many cases an urgent issue is grid integration and balancing. The variable outputs from wind and PV solar outputs are balanced on some grid systems by using existing fossil-fueled plants, but the later are having a hard time competing, now that some of their peak market has been taken over by low marginal cost (zero fuel cost) wind and PV. To ensure that there is enough capacity still available capacity markets have been proposed, offering extra payments. Some critics don’t like the sound of that- it’s yet another subsidy, in effect for fossil fuel. However, the proposed UK version includes payment for energy storage and demand management options, as well as for gas-fired back up plants, and longer term, fossil gas might be replaced by green gas in the latter. There again there are other balancing options- supergrid links for example, which would open up a new multi-national balancing market.  Which option is best? (more…)

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US green energy: store, curtail – or export?

by Dave Elliott

The US is pressing ahead with renewables, with around 60GW of wind and 10GW of PV solar already in place.  But that means some system operation issues are coming to the fore.  Since these sources vary, as does demand, when there is surplus output from wind of PV, should it be stored or just dumped?

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Too much wind

‘When storms come, some build walls, some are thrown by the wind, others build windmills’. So said Chinese philosopher Lao Tzu. But sometimes you can overdo it.

In my last Blog http://environmentalresearchweb.org/blog/2011/05/not-enough-reliable-wind.html I reported on criticisms from, basically, anti wind power groups that there was not enough reliable wind. However, there are, perhaps perversely, also criticisms that there is sometimes too much wind- which means that, under current market and grid balancing arrangements, compensation is paid for the loss of potential earnings. For example, six Scottish wind farms were paid a total of nearly £900,000 to stop producing energy because the grid network could not absorb it, for several hours between April 5-6th.

£308,000 went to Scottish Powers Whitelee wind farm in East Renfrewshire, £265,000 to RWE/nPower’s Farr wind farm south of Inverness, £140,000 to SSE Renewables’ Hadyardhill in South Ayrshire, and £130,000 to Scottish Power’s Blacklaw in Lanarkshire, while the Millennium wind farm in the Highlands and Beinn Tharsuin, north of Alness, got £33,000 and £11,500 respectively.

The Renewable Energy Foundation (REF) said the payments ranged up to 20 times the value of the electricity that would have been generated if the turbines had kept running. That was for the Farr wind farm. The payments include compensation for the loss of the Renewable Obligation subsidy element. Dr Lee Moroney, planning director for the REF, which has criticised subsidies to renewables in the past, said: ‘The variability of wind power poses grid management problems for which there are no cheap solutions. However, throwing the energy away, and paying wind farms handsomely for doing so, is not only costly but obviously very wasteful. Government must rethink the scale and pace of wind power development before the costs of managing it become intolerable and the scale of the waste scandalous.’
www.ref.org.uk/publications/231-high-rewards -for-wind-farms-discarding-electricity-5th-6th-april-2011

The National Grid said ‘On the evening of the 5th into the 6th of April, the demand for power was low but the nuclear generating plants in Scotland were running as expected. There was also heavy rainfall, which mean hydro power plants were operating well too’. A fault in the transmission system also meant the surplus energy could not be transferred to England.

DECC described the incident as ‘unusual’ and said ‘In future we need greater electrical energy storage facilities and greater interconnection with our EU neighbours so that excess energy supplies can be sold or bought where required.’

The Scottish government said ‘electricity generated by renewables accounted for 27.4% of Scotland’s electricity use. National Grid is responsible for balancing the supply of electricity from all sources across the grid to match demand and generators will sometimes be required to reduce output as part of that process. At the same time, the Scottish and UK governments have been working with the National Grid and others in the industry to strengthen grid capacity and address access constraints’. That will certainly be necessary if Scotland is to achieve the new heroic target promoted by the SNP during the recent Scottish elections of getting 100% of electricity from renewables by 2020!

The basic problem is that turbines can be, and have been, built much faster than connectors, although payment for curtailment is common to all plants with similar supply and grid balancing contracts- fossil fired standby plants get paid when idle too. But under the ROC system wind gets larger basic payments and some projects have it seems negotiated good curtailment deals. Crucially, under current policies, the nuclear output is not curtailed. Maybe it should be, making room for wind. But then nuclear would be (even more?) uneconomic, and if it got a curtailment fee, (even more?) subsidised.

This problem will only get worse as more wind, plus other renewables, and more nuclear are put on the grid. The Climate Change Committee (CCC) has just outlined a possible strategy in which, by 2030, nuclear and renewables would each have about a 40% share. This would require an additional 2-3 nuclear reactors on top of those developers are already planning to build. The CCC do look to smart grids and storage to help deal with grid balancing, but much more will be needed- and ideally new market and contractual arrangements. But, even so, it is hard to see how we can avoid expensive curtailment events during low demand periods if we have large amounts of inflexible nuclear and variable wind both seeking to feed into the grid. Perhaps the new government White Paper on the Electricity Market Reforms, expected maybe in June, will have some answers.

The overall renewable energy target seem likely to remain in place, unless we re- negotiate it down with the EU, as a new report fro the right of centre Policy Exchange suggested. However, the CCC report suggested cutting back on offshore wind targets, as did the Policy Exchange- which claimed it was too expensive. The offshore wind target has already been drastically cut from the 30-32GW envisaged at one time, to around 13GW by 2020, as spelt out in last July’s UK National Renewable Energy Action Plan. Will even that now be viewed as excessive? And if so where is the compensating expansion? The new Renewable Heat Incentive is fine as far as it goes, although most of it won’t start until next year, and it’s just for heat. As for electricity, PV solar has just been savaged with FiT tariff cuts for large projects, the Marine Renewables Deployment Fund has been axed, and last year Lord Marlan said ‘there should be no dramatic increase’ in on-land wind generation above current targets. The White paper should make for interesting reading.

http://www.theccc.org.uk/reports/renewable-energy-review

http://www.policyexchange.org.uk/publications/publication.cgi?id=239

For more on renewables policy, see: http://www.natta-renew.org

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