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Tag Archives: intermittency

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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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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Grid balancing ‘needs extra firm capacity’

By Dave Elliott

Even ‘very significant’ storage, demand-side measures and interconnection would not be sufficient to cope with intermittency in a weather-dependent renewables-based electricity system, according to modeling, up to 2030, by the Energy Research Partnership (ERP). It says there would still be a need to have a significant amount of zero-carbon firm capacity on the system too – for dark, windless periods. It could, for example, be supplied by nuclear, biomass or fossil fuel plants with Carbon Capture and Storage (CCS).

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Europe and supergrids – balancing grids across the EU

By Dave Elliott

A pan-European supergrid network could play a major role in helping Europe achieve an ambitious 45% share of renewable energy by 2030 at low extra cost, by balancing grids and limiting curtailment,  according to a new Greenpeace report,  PowE[R]2030, based on analysis by Energynautics, and using data from the International Energy Agency.

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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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IEA on energy costs

by Dave Elliott

Renewable energy may supply more electricity than natural gas and twice as much as  nuclear globally by 2016, due to declining costs and growing demand in emerging markets, according to the International Energy Agency.

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Wind power reliability

by Dave Elliott

Earlier this year (26/6/13) Daily Telegraph columnist Geoffrey Lean said that ‘it has become an article of popular faith that building wind farms also involves constructing fossil-fuelled power stations for back‑up when the weather is calm. As a result, some opponents go on to say, wind turbines do little or nothing to cut carbon dioxide emissions’.  But he reported that the National Grid says that, although between April 2011 and September 2012 wind produced some 23,700 gigawatt hours of electricity, only 22GWh of power from fossil fuels was needed to fill the gaps when the wind didn’t blow- under 0.1%. Moreover this standby burning of fossil fuels only reduced the emission saving from having wind on the grid by 0.081%. He commented ‘not surprisingly, given these figures, no new fossil‑fuel power station has been built to provide back‑up for wind farms, and none is in prospect’.

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Renewables: observing the future

by Dave Elliott

In its business leader column on August 25th The Observer, said “If there is a body of opinion that states that wind farms and energy efficiency can fill the looming energy gap, then it is small and deeply unrepresentative”. www.theguardian.com/business/2013/aug/25/anger-fracking-cant-manage-without-gas

Germany is aiming to get at least 80% of its electricity from renewables by 2050, with overall energy demand cut by 50%, so the Observer seems to have it wildly wrong, certainly long term.  And in fact, far from being marginal, around 50 countries are already getting more than 60% of their electricity from renewables in the form of hydro, some of them near 100%. http://k.lenz.name/LB/?p=6525. Longer term, dozens of studies claim that renewables could supply 100% of the worlds electricity in many countries by around 2050. http://www.mng.org.uk/gh/scenarios.htm. That is what Denmark and New Zealand are aiming for and many others see renewable as their main future energy option- with China leading the way.

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Beyond pessimism

by Dave Elliott

One of the justifications for the UK government plan to expand the use of nuclear power is the assertion that energy demand will double in the decades ahead. That seem a little odd given that DECCs statistics show that in 2011 electricity consumption went down by 3.3% and gas use fell by almost 20%, while renewable generation expanded, albeit from a low level, by 33%. Renewables seem likely to continue to expand, given that the UK has amongst the EU’s (if not the world’s) best renewable energy resources, even if we have not developed them much yet.  As then Tory Energy minister Charles Hendry said at the opening of the annual All Energy conference in Aberdeen last spring, ‘It is shameful that with some of the strongest winds and highest tidal reaches in Europe, the UK is currently third from bottom in the whole of the EU in its use of renewables.’   He was removed from office a few months later.

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Variable truths on wind

The debate over how to deal with the variable energy output from wind turbines continues to rumble on. Some say that, when wind availability is low, there will be a need for extensive back up from conventional plant to maintain grid reliability. However, this backup may already exist: we have a lot of gas-fired capacity, much of which is used regularly, on a daily basis, to balance variations in conventional supply and in demand. Balancing wind variations means this will just have to be used a few times more often each year, adding a small cost penalty and undermining the carbon savings from using wind very slightly. But some say we will need much more that that. A report from Parsons Brinckerhoff (PB) claims that “the current mix of generating plant will be unable to ensure reliable electricity supply with significantly more than 10 GW of wind capacity. For larger wind capacity to be managed successfully, up to 10 GW of fast response generating plant or controllable load will be needed to balance the electricity system”.

www.pbpoweringthefuture.com

“Controllable load” includes the idea of having interactive smart grids which can switch off some devices when demand is high or renewable supplies are low.

However even if that option is available, some say that, with more wind on the grid, to meet peak demand, we will still need more backup plants than we have. By contrast, wind energy consultant David Milborrow claims we have enough, and that some fossil-fired plants can actually be retired when wind capacity is added. That depends on the “capacity credit” of wind – how much of the wind plant capacity can be relied on statistically to meet peak demand. Milborrow puts the capacity credit of wind at around 30% with low levels wind on the grid, falling to 15% at high levels (at say 40% wind on the grid). That indicates how much fossil plant can be replaced.

www.greenpeace.org.uk/media/reports/wind-power-managing-variability

PB see it very differently: “A high penetration of intermittent renewable generation drastically reduces the baseload regime, undermining the economic case for more-efficient plant types with lower carbon emissions.”

Milborow admits that balancing wind variations has the effect of reducing the load factor for thermal plant, but says that this only costs ~£2.5/MWh at 20% wind, or ~ £6/MWh at 40%. PB will have none of this: “Very high early penetration of wind generation is likely to have adverse effects on the rest of the generating fleet, undermining the benefits of an increased contribution of renewable electricity.”

PB also seems to slam the door on a possible way out, importing power from continental Europe, the wider footprint then helping to balance variations across a much larger geographical area. It says: “Electricity interconnection with mainland Europe would offer some fast-response capability, but would be unlikely to offer predictable support. Without additional fast-response balancing facilities, significant numbers of UK electricity consumers could regularly experience interruptions or a drop in voltage.”

Addressing the interconnector issue, among others, TradeWind, a European project funded under the EU’s Intelligent Energy-Europe Programme, looked at the maximal and reliable integration of wind power in Trans European power markets. It used European wind power time series to calculate the effect of geographical aggregation on wind’s contribution to generation. And it looked ahead to a very large future programme, with its 2020 Medium scenario involving 200 GW – a 12% pan-EU wind power penetration. It found that aggregating wind energy production from multiple countries strongly increased the capacity credit.

www.trade-wind.eu

It also noted that “load” and wind energy are positively correlated – improving the capacity factor – the degree to which energy output matches energy demand. For the 2020 Medium scenario the countries studied showed an average annual wind capacity factor of 23–25 %, rising to 30–40 %, when considering power production during the 100 highest peak load situations – in almost all the cases studied, it was found that wind generation produces more than average during peak load hours.

Given that “the effect of windpower aggregation is the strongest when wind power is shared between all European countries”, cross-EU grid links were seen as vital. If no wind energy is exchanged between European countries, the capacity credit in Europe is 8%, which corresponds to only 16 GW for the assumed 200 GW installed capacity. But since “the wider the countries are geographically distributed, the higher the resulting capacity credit” if Europe is calculated as one wind energy production system and wind energy is distributed across many countries according to individual load profiles, the capacity credit almost doubles to a level of 14%, which it says corresponds to approximately 27 GW of firm power in the system.

Clearly then, with very large wind programmes you do get diminishing returns and need more backup, but it seems that can be offset to some extent by wider interconnectivity – the supergrid idea, linking up renewables sources across the EU.

That is already underway. The UK’s National Grid has agreed with its Norwegian counterpart Statnett to draw up proposals for a £1 bn grid-interconnector grid link-up, to be funded on a 50:50 basis, which could help solve the problem of winds intermittency, given that Norwegian hydro could act as back-up for the UK, in return for electricity from the UK on windy days. As yet no UK landfall site has been indicated, but it could include connection nodes along the route with spurs taking power from offshore wind farms and become the backbone of a new North Sea “supergrid”: the UK and eight other North West EU countries have now agreed to explore interconnector links across the North sea and Irish sea. National Grid said: “Greater interconnection with Europe will be an important tool to help us balance the system with large quantities of variable wind generation in the UK.”

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