Nimrod103 wrote:dspp wrote:Even CCGT need intermittency cover. Maybe not as much as wind but they still need some. Not as much as nuclear mind you, that is the real big need for intermittency 'insurance' as it can fall over in 1GW chunks. But it is difficult to properly allocate the 'insurance' required for intermittency as one policy currently covers multiple users which is a very cost-effective result, i.e. the same backup can support both wind & solar & gas & nuclear, as it is a pooled backup.
I don't really see why a CCGT power station should have downtime, except for maintainance, and when demand is lower during the night and summer. Hence why 70% is perhaps fair. The problem with wind is that some of the downtime due to the wind not blowing will be during peak demand....
Not all downtime is planned .......
I am clearly not explaining myself very well. The biggest short-term downtime event that currently concerns the UK grid (so I am told, by those who ought to know) is if a nuclear power station trips off the bars with no notice, that is about 1.2 GW but is a fairly high probability big event (i.e. needs to be planned for). A longer term event that is even bigger and is planned for is if a 'surprising' fault condition is found that affects all of one class of nuclear reactors requiring them all to be taken off load for (say) a few months, but probably with a day or so of notice. That is probably 7 x 1.2 GW = 8.4 GW for all the AGRs and is a very low probability event. Then there are much higher probability events that affect smaller amounts of power. The point about 'pooling' is that all the smaller events can take a free ride on the system-wide backup capacity that exists to cater for these big events, and so too - to a very significant extent - can all the smaller generators of other types take a similar free ride in both economic & technical terms.
Believe me conventional generators of all scales have intermittency issues - I have spent much of my life dealing with this, whether offshore or onshore. I have four such problematic events in the quarterly board report I was writing up today (MW-class, conventional legacy equipment). Maybe you can't see the problem, but I can assure you it exists. Typically about a week to resolve ....... (which happens to be the likely duration of the longest high pressure cells with low wind in mid winter BTW which is what some folk get concerned about for wind power, i.e. these are normal issues in grid/energy planning terms).
Then you should also look at the actual power used in any given half hour of all of the days of the year, vs the total capacity. Again the demand peaks at just a few hours in the winter months in the UK (typically). So there is plenty of spare capacity in the system for most of the months of the year, and for most of the hours of the day even in the high demand months. Again this means that a free ride exists in backup capacity planning terms for almost all types of generators for almost all of the time.
And yet some folk get fixation about the 'cost' of providing backup for renewables. And they keep trying to pin the 'backup cost problem' onto the renewables as if it was only a renewables issue. Really it is not a problem, and at the moment it is primarily a conventional intermittency problem that is both the technical design-driving case, and the economic 'cause' that ought to be carrying the bulk of the cost.
In due course renewables should carry their share but at present that is not a significant share. Below 40% renewables penetration it is a trivial share. Not until about 80% renewables penetration does it become a serious economic concern with renewable deployment, and that is assuming current technology. By the time the UK gets to 80% then I expect the technology will have improved such that the significant moment will be at 90% or etc.
regards, dspp