To maintain a stable grid, Eirgrid have always ensured that there is enough "spinning reserve" (or back up generation) running or available to provide power at short notice in the event that a power station trips (i.e. suddenly has an outage) or there is a sudden change in demand.
For many years, the minimum for this reserve requirement was set at 440MW, made up of four different types of reserve with different reaction times, of 110MW each. The quickest can deliver in less than five seconds, the slowest in less than five minutes, with the latter capable of lasting much longer than the former. The remaining reserves can react within 15 and 90 seconds.
The two fastest reacting reserves are called Primary and Secondary Operating Reserve and are provided by units already running on the system that can change their output quickly to deal with unexpected events. The two slower reacting reserves are called Tertiary Operating Reserves and are provided by units both already on the system and that can start quickly at short notice. For additional security, there are also replacement reserves that can start from 20 minutes to four hours and are provided by fast acting offline generators such as open gas cycle turbines (basically jet engines).
The question then arises - if wind energy is inherently variable, just as demand is, or unpredictable just as a generator outage is, what impact does it have on reserve requirements in the event that it unexpectedly rises or falls ? In otherwords, does it contribute to an increase in unexpected events that can't be forecast by the grid operators ? If the answer is yes, then more reserves will be required, likely in the form of fast acting fossil fuel generators (and with a consequence increase in emissions.) Consider that the single largest generator that can fail in the system at any one time is about 500MW compared to combined wind energy capacity of 3,000MW which if acting in unison (as it usually does) is six times the size.
In 2014, the SEAI issued their "Quantifying Ireland's Fuel and CO2 Savings from Renewables" report based on the contribution from wind energy during 2012.
This is what they concluded in relation to the potential impact of wind generation on reserve requirements :
Future planned increases in wind capacity will influence the reserve requirements, particularly tertiary reserve requirements. The All-Island grid study showed that additional reserve requirement in hypothetical 2020 scenarios is related to the amount of wind installed but that the largest contributing factor remains the loss of the largest conventional unit. Wind power does not necessarily require larger amounts of primary and secondary reserve, when the characteristics of the wind are taken into account in the calculation of reserve requirements. The relative electrical isolation of the All-Island system means that the reserve levels consider the need for a high degree of generator flexibility, while additional rules ensure a sufficient number of units remain online to ensure frequency and voltage stability. Reserves allow the electricity system to respond to unexpected events but the ability of the system to incorporate variability and uncertainty due to renewable electricity generation is primarily determined by system flexibility.
In essence, the SEAI are claiming there will be little impact on reserves from wind power but with caveats thrown in about it impacting mainly tertiary reserve and careful use of words like "at present" which would indicate that future levels of wind energy are not being examined in their report anyway.
At present, renewable electricity generation on the All-Island system does not influence the quantity of reserve required.
In the same year, I wrote an article for this blog challenging the SEAI's report and in particular their omission of the impact of wind energy on reserves. I argued that higher levels of wind energy would indeed lead to an increase in reserves and based my argument on research done by both Danish and UCD researchers (in 2007 and 2005) :
There should be enough spinning reserves to cover an outage of the largest unit in combination with a fast decrease of the current wind power production. However, the capacity of the largest online unit changes dynamically. (Doherty and O’Malley 2005) further demonstrate the dependency of the demand for TR1 [Reserve Type 1] from the installed wind power capacity.
"Generally, the demand for replacement reserves increases with increasing wind power capacity installed.
The occurrence of high demands for replacement reserves is mainly driven by a high number of simultaneous forced outages that happen simultaneously to relatively high wind power or load forecast errors. The value of these peaks tends to increase with increasing wind power capacity installed." - Wind Variability Management Studies (P.Meibom et al)"
My article has now been vindicated four years later as a recent Eirgrid document shows that they have increased the minimum levels of spinning reserve required for the Irish grid.
Previous Operating Reserve Requirements
New Operating Reserve Requirements, Summer 2018
This means the minimum reserve now is 540MW (135 * 4), up 100MW, with at least half of that coming from units already running on the system. The reason for this increase is due to DS3 System Services Contracts. DS3 services, as explained before on this blog, are services required by conventional and other generators to facilitate high levels of wind energy.
From the onset, the integration of wind generation presented a range of challenges previously unseen in the power sector. Through collaboration with the Regulatory Authorities and the wider electricity industry, DS3 has developed a number of innovative and progressive solutions.
The cost of which may well become significant :
This means that some types of service providers could be available and eligible for payments for every hour of the year assuming they are not forced out or scheduled out for maintenance, even if the service is not required from those providers for all of these hours. The scale of overall payments will therefore increasingly depend on the portfolio of service providers and the expected availability of individual service providers.
2014 Irish Energy Blog article : http://irishenergyblog.blogspot.com/2014/12/seais-quantifying-savings-from.html
We need 6,500 MW of fossil fuel generation in the Republic. We are heading towards double that and more when solar comes on stream. The excess is a mixture of wind and the reserve plant outlined above. They all have to break even financially. They must be paid whether they generate or not. Fast acting fuel plant of all types has a long life span, low commercial rates and low expenses. It's contained in a building with convenient access. Wind has high commercial rates, is expensive to repair and turbines have a short life span. Wind is rewarded based on electricity produced and not enough is being produced.
ReplyDeleteThe blog makes the important point that increased penetration of inherently variable wind necessitates more reserves, particularly POR and SOR and has indeed been vindicated by the September 11 Operational Constraints Update from EirGrid/Soni.
DeleteHowever, it is difficult to see why we need 6500MW of fossil fuel generation in the Republic and why this should approach 13GW of fossil fuel generation when solar comes on stream. Could you please elaborate on this?
Yes. It must be remembered that with Irish (and most other) grid systems, the default position is on, not off. To clarify, the default position of a car, a washing machine or a lawn mower is off (stopped). The entire country and economy depends on electricity at the flick of a swatch. A lot of the power is for very light loaded appliances like lifts, escalators, clocks, computers, lighting, traffic lights, medical, oil/gas heating regulators/timers/pumps and so on. If this default fails, it is an emergency and must be avoided. The occasional scheduled blackout is a sort of novelty for which we can cope, but if that blackout lasts a long time or repeats, it would damage confidence in suppliers, it would be costly and dangerous. This is the world we have built.
DeleteIt must also be remembered that if a country changed to an intermittent supply to save generation emissions, it would reduce fuel usage, but it would result in a radical alteration in the way our economy operates and some customers might switch to home generation.
Ireland's maximum winter peak demand is 5,000 MW at mid evening and lowest summer demand is 2,000 MW at early morning. There must be 6,000 MW of firm (fossil fuel) capacity to meet this load which includes a reserve in case of a break down of plant during winter peak demand. From mid Spring to Mid Autumn (fall) there is adequate reserve with 5,000 MW. Up until 1990 this was all the capacity we had or needed in Ireland and prices were relatively low. Electricity workers were a very powerful force and could strike for higher wages and better conditions. They could hold government and the people to ransom and very often they did. This may have been a factor in the decision to split up the monopoly held by the ESB. Add in the global warming scare and an unjustified obsession with self reliance and renewables were shoehorned in by government and accepted by an ignorant public.
The problem is that generators must be there when needed. Grid controllers can predict demand and they can schedule generators to meet it. Generators vary from diesel engines with immediate start up to gas fired combined cycle turbines and heavy condensing steam plant fired by coal.
Neither wind or solar can be scheduled because they are powered by intermittent weather conditions. If it is a calm night, there is none at all. It is important not to confuse predictability of the wind or sun with availability of them. If they are not available, they don't exist until they are available. Solar is worse than wind, because there is none at night and often little or none in the day time.
It must also be understood that wind, solar and imported electricity is non synchronized, while the grid must me maintained at 50 Hz within a very small tolerance. This is provided by heavy rotors in large generators powered by controllable means and 3 phase motors driven by them. A ratio of 50 firm/50 renewables seems to work fine, 60/40 has been achieved and 70/30 is hoped for. The higher the renewable percentage, the more unable the system becomes. Renewables are constrained down to adjust the ratio.
One of the most inconvenient features of wind turbines is that most cutout or shutdown at wind speeds of 25 meters per second.Or 90 KPH wind. Cut back in wind speeds are usually 23 meters per second. In turbulent winds where wind speeds exceed the cut out speed you could have up to 1000 megawatts shutting down and starting back up again at regular intervals. Building these useless large capacity wind farms close to one another means that the sum of that capacity becomes prone to immediate or almost immediate shutdown.So your cycling/ spinning reserve will have to be equal to all that wind capacity in the most densely commissioned wind turbine geographic area. That is if Eirgrid chooses to allow such chaotic production access to the grid. In past storms they have forecast large wind output only to allow access to the grid for a small fraction of that output forecasted to the grid.The EU /State organised wind program is a sick joke and it has failed. Shut it down.
ReplyDeleteTo clarify my post of 19th inst at 8.34 am and avoid confusion The default position of the grid is on. Power must be available every minute or every hour of every day. It is the same as the human heart, if it missed a few beats at the age of 35 it will never beat again. Blackouts are abnormal, not normal. If I reduce this to frequency @ 50 Hz: 8766 hours per year X 60 minutes X 60 seconds X 50 Hz =
ReplyDelete1,577,880,000 frequency cycles or 1.5 billion. There is a big difference in ensuring supply where a blackout is OK to one where it is not OK. This is why firm fossil fuel generators can never be got rid of. Its a myth which many people still believe.
Decarbonisation Made Easy
ReplyDelete2 GW of nuclear generation at Moneypoint (where there is an existing port for transhipping nuclear fuel), another 2 GW at Carnsore Point (adjacent to Rosslare port) and a final 2 GW at Larne would nicely balance all-island distribution without the need for any other generation. Up to 2.2 GW of off-peak generation can be used to charge EVs (reducing fossil-fuelled transport) or exported to the UK (via EWIC and Moyle) or France (Celtic Interconnector).
This solves the need for additional pumped storage such as the Spirit of Ireland project proposed by Professor Igor Shvets of Trinity College which does not seem to be a starter. Writing in the Sunday Independent on May 20 this year, John Reynolds reported that Statkraft, a €5bn Norwegian energy giant, turned down a 2013 opportunity to invest in the €1.5bn Spirit of Ireland pumped hydro power storage scheme.
The Transmission Development Plan 2016-2026 sets out reinforcement of the transmission setwork in the South-West with new STATCOM projects at Ballynahulla (Ballydesmond, Co. Kerry) 220/110 kV Station (CP0934) and Ballyvouskill (Millstreet, Co. Cork) 220/110 kV Station (CP0935). The planning applications for both of these projects have been lodged with Kerry and Cork planning authorities in the past week, and have planned go-live dates of Q4 2020.
ReplyDeleteThese are in addition to planning applications currently under consideration for large scale battery based system services projects by Redfaze in Ballynahulla and both Redfaze and Kinbrace in Ballyvouskill. These projects, if granted planning permission, will add 200MVAr of static compensation and a 300MW source of fast frequency response systems service to the counties of Kerry and Cork alone.
If this scales up pro-rata across the remainder of the country, it looks like the technology underpinning grid stability may well transition from fossil-fuelled spinning reserve to solid-state synthetic inertia in the form of system services as set out so well in this blog. This transformation from electro-mechanical to electronic reserves will be intensified when the long awaited "smart" meters are rolled out.
Whether the reliability of the solid state national grid will weather lightning and sunspots as well as the existing configuration remains to be seen.
A large percentage of these Lithium Ion batteries will probably explode. Covering the country side with toxic gases. The whole wind program is crazy and it has failed.
ReplyDelete