jueves, 28 de julio de 2016

El Hierro completes a year of full operation

Posted on  by Roger Andrews

At the end of June the Gorona del Viento (GdV) plant completed its first year of full operation, during which it supplied 34.6% of El Hierro’s electricity demand with renewable electricity at a cost probably exceeding €1.00/kWh and lowered the island’s CO2 emissions by approximately 12,000 tons at a cost of around €1,000/ton. This post summarizes these unexpectedly poor results, discusses the reasons for them and concludes that GdV, which was intended to show the world how fossil fuel generation can readily be replaced with intermittent renewables, can already be classified as a “failed project”. GdV’s performance further suggests that replacing fossil fuels with intermittent renewables elsewhere in the world could be a lot more difficult than the proponents of renewable energy are prepared to admit.
Details on GdV plant layout, operation and capacities are given in the September update. Previous posts on GdV are accessible through the El Hierro Portal.
Figure 1 plots the daily average percentage of renewables generation supplied by GdV to the El Hierro grid since June 27, 2015, when full operations began, through June 30, 2016: Noteworthy features are:
  • The low renewables generation from September 2015 through January 2016, a result of low wind speeds.
  • The irregularity of renewable energy deliveries to the grid, which can change from 70% or more of demand to near-zero in the space of a few days, again depending mostly on wind speed.
  • The lack of any significant increase in the percentage of renewables generation with time.
Figure 1: Daily average percent renewable electricity sent to the El Hierro grid
The Table below summarizes generation statistics by month. Note that all the data presented in this post are 10-minute grid readings from Red Eléctrica de España (REE)unless otherwise specified:
And Figure 2 shows generation by source during June 2016:
Figure 2: El Hierro generation by source, June 2016
June started inauspiciously with a grid crash, but the 53.9% renewables generation during the month was the highest yet achieved, marginally exceeding the 53.5% achieved in February. Partly this was a result of the two 100% renewable tests conducted on June 14/15 and 19/20/21 and partly a result of strong and unusually sustained winds during the second half of the month (Figure 3):
Figure 3: Three-hour wind speeds recorded at El Hierro airport , June 2016
El Hierro airport is located at sea level some 3km northeast of the GdV wind park. As shown in Figure 4 airport wind speeds generally track GdV’s wind production, confirming that variations in airport wind speeds are representative of variations in GdV wind speeds, although absolute GdV wind speeds would be expected to be higher. The correlation further suggests that there have been no extended turbine shutdowns since project startup. (The “busts” in May 2016 were a result of a failed generation experiment discussed later.)
Figure 4: Daily average airport wind speeds vs. GdV daily average gross wind generation since the beginning of full-time operations
GdV’s Problems:
These can be divided into the three basic categories discussed below – inadequate wind capacity, failure to solve grid stability problems associated with high levels of wind penetration and hopelessly inadequate energy storage. However, it should be noted that GdV does not publish any performance data or supply any information on its operating procedures, so these conclusions are deduced from REE’s grid data plus whatever background information could be obtained from other sources, such as the reservoir level photos and grid frequency data compiled by Rainer Strassburger. It’s therefore possible that some of them are wrong or misleading, and once again GdV representatives are encouraged to point out any errors.
Wind Power
The GdV wind park consists of five 2.3MW Enercon turbines capable of generating up to 11.5MW, but during the first year of operation wind generation never exceeded 7.5MW. Wind has consistently been curtailed, usually but not always at or around the 7MW level. Figure 5, which shows wind generation in June 2016, is an example. Wind was curtailed at 7MW for much of the month:
Figure 5: GdV gross wind generation, 10-minute intervals, June 2016
Comments in previous posts have addressed the question of why wind output is curtailed at this level, but the reasons are secondary. The facts are a) that it is and b) that there has been no significant relaxation of curtailment thresholds in a year of operation. Curtailment of wind power at or around 7MW is obviously considered necessary, presumably because too much wind power compromises grid stability, and short of a system redesign we can be reasonably certain that it will continue at or around these levels.
In addition, wind power is GdV’s only primary generation source, meaning that the wind turbines must be capable of generating at least enough power to fill El Hierro’s annual electricity demand. But over the last year they filled barely more than half of it (45.1GWh demand versus 24.5GWh gross wind generation). Even with no curtailment wind generation would still have fallen short of demand. Clearly the GdV wind park is too small. (Why was it not built larger? The reasons are unclear, but there is evidence to suggest that a capacity factor of around 50% was assumed for design purposes. The actual capacity factor calculated using gross wind generation over the last year is 24%.)
Grid Stability
A 2012 study conducted before GdV started operations concluded that power generated by the wind turbines could be admitted to the El Hierro grid without compromising grid stability provided three of the Pelton turbines in the hydro plant were maintained as a spinning reserve:
The results show that, to ensure system stability in the worst network contingency, the best option is to hold three hydraulic units in spinning reserve mode
This approach has clearly not worked, and as a result GdV has had to resort to other measures. And it’s important to note here that GdV has been experimenting for not just one year but two. The just-completed year of full operation was preceded by a year of testing.
And what are these other measures? There are two basic approaches, both of which must have been developed during the testing period because they were applied as soon as GdV went into full operation:
  1. During lower-wind periods generation is matched to demand using mostly diesel for load-following, assisted or replaced by wind and hydro generation when available.
  2. During higher-wind periods diesel generation is used in baseload mode and held stable at levels of 1.6MW or higher. Load-following is performed by switching wind generation between the grid and the GdV pumping plant, which wastes the excess power by pumping water uphill from the lower to the upper reservoir and letting it flow down again without turning the hydro turbines. In short, the hydro system is being used as a dynamic resistor – a far cry from its intended purpose.
Figure 6 shows generation for July 2015, the first month of full operation and a good wind month. For most of the time diesel was run in a 1.6 or 3.2MW baseload mode and generation was matched to demand by sending excess wind power to pumping. During a few lower wind-days, such as July 7 and 8, demand was matched with variable combinations of diesel, wind and hydro. Overall, however, the plot is very similar to the June 2016 generation plot (Figure 2), confirming that there has been no significant change in operating procedures over the last year:
Figure 6: El Hierro generation by source, July 2015
A third approach was tried in May 2016, with wind and hydro used as baseload generation and diesel for load-following. Needless to say it failed to improve renewables output, and in fact probably chopped a point or two off GdV’s annual percent renewables number. The fact that it was even attempted suggests that desperation may have begun to set in:
Figure 7: El Hierro generation by source, May 2016
Two other factors bear on the question of grid stability. The first is grid outages. Since mid-February there have been five complete or partial grid crashes on El Hierro (February 18 at 0450 and 1040, February 19 at 0320, April 7 at 1220 and June 1 at 1420). The reasons for these outages have not been publicized, but the three February outages correlate with what appears to have been system-mandated shutdowns in wind generation, possibly caused by wind speeds exceeding the turbine cutout speed (wind speeds of up to 16m/s were recorded at the Airport over this period):
Figure 8: Gross 10-minute wind generation versus El Hierro demand during the February 2016 grid outages.
The second factor is 100% renewables testing. Since August 2015 GdV has conducted eleven tests, with durations ranging from 2 to 41 hours, when diesel generation was shut down and all GdV’s generation came from renewables. Two of these tests occurred in June (Figure 2).
The problem in evaluating the significance of these tests is that except for those run on Sundays, when demand is lowest and a grid outage will cause the least damage, there is no obvious reason why they started and stopped when they did. This is in fact a problem with all the GdV grid data, which show numerous changes in the generation mix that do not coincide with any obvious changes in wind conditions or demand. It seems that GdV’s operating protocols, which are reportedly handled by state-of-the-art computer technology, are too complex for the human mind to understand. If so it’s not surprising that GdV has failed to solve its grid stability problem. But the bottom line is that grid manager REE remains unwilling to allow these tests to continue indefinitely, and presumably it has good reasons for this.
Energy Storage
Here we come to GdV’s fundamental (and unsolvable) problem. GdV was built because of the existence of an inactive volcanic crater 700m up the hill, which it was believed would provide enough energy storage when filled with water and linked to a lower reservoir to smooth out fluctuations in wind generation. Unfortunately no one bothered to do the sums and check the wind records. Had they done so they would have found that the storage was adequate to fill El Hierro’s demand for only about two windless days and that low-wind periods on El Hierro can last for months. As a result the project now boasts a pumped hydro system that is totally inadequate and which to all intents and purposes might as well not be there. Here is what I had to say about it in the January/February update :
Now we will look at a specific example – October 2015, the worst wind month since operations began, although December wasn’t much better. The GdV reservoirs have an energy storage capacity of about 250MWh (limited by the 150,000 cu m capacity of the lower reservoir) and I start by assuming that they are fully charged at 0000 hours on October 1, although as a practical matter they won’t be because the second half of September was windless too. How long does the storage last? Figure 7 shows that it runs out at midnight on October 4, leaving a 3,000MWh deficit between demand and wind generation over the rest of the month that would have to be filled with diesel generation.
Figure 9: Figure 7 of the January/February update, showing the 3,000MWh energy storage deficit in October 2015.
A 3,000MWh deficit represents over ten times the storage capacity of the existing reservoirs. Add to it the deficits incurred during the windless periods in September and November and the existing storage capacity would have to be increased by a factor of at least twenty to provide adequate long-term storage. This is not a feasible option, nor is it ever likely to be.
The hydro system does not seem to be working as planned either. Hydro generation to date has been minimal, and the fact that the upper and lower reservoirs seem never to have been filled to more than 20% of their design capacity suggests that there is either a shortage of desalinated water or a problem with dam stability. These are, however, secondary issues.
Is GdV a failed project?
There are two aspects to this question; first, what exactly were GdV’s goals, and second, if they have not yet been met, is there any chance that GdV could still meet them.
As to what GdV’s goals were, there are three different perspectives. First we have the starry-eyed pronouncements of the mainstream media, who were never in any doubt that GdV was henceforth going to supply all of El Hierro’s energy needs with renewables. GdV is nowhere close to doing this, so the verdict here is FAIL.
Second are two engineering studies carried out before project startup, one of which estimated that GdV would supply 68.4% of El Hierro’s electricity demand  with renewables and the other 64.6%. With renewables supplying only 36.4% of El Hierro’s electricity in its first year of operation GdV is falling well short of these projections too. So the verdict up to this point is also FAIL.
Third is the one that counts – the official version of what GdV was supposed to achieve and the one on which the project was marketed and financed. This is set forth in GdV’s project description and reads as follows:
The operation’s philosophy is based on supplying the electrical demand of the island with renewable sources, thus guaranteeing the stability of the electrical network; the diesel engine plant will only operate in exceptional/emergency cases, when there is not enough windwater (sic) to produce the demanded energy.
This is another obvious FAIL. The wording clearly implies that GdV was expected to produce if not 100% renewable energy all the time then something very close to it. In addition, the stability of the electrical network is still not guaranteed and the diesel plant has so far operated for more than 97% of the time, not just in exceptional cases. I hasten to add, however, that I don’t think that GdV’s bloated expectations were an intentional attempt to defraud. They simply illustrate what happens when green energy enthusiasts get carried away with visionary concepts that they do not take the time to evaluate properly, and also the gullibility of the project’s backers, notably the Spanish government, who also never took the time to do their homework before signing the GdV contract. As a result the government paid through the nose for a very modest amount of GdV renewable electricity in 2015 – €12 million for the 8.7 GWh delivered works out to €1.38/kWh – while the El Hierro Island Council, which owns 67% of GdV, is laughing all the way to the bank.
The second aspect of the issue is whether GdV, given time, could ultimately meet its goals. In this context I am indebted to Hubert Flocard, who after carrying out a detailed analysis of GdV’s first-year operating data has concluded that the maximum achievable annual renewable fraction at GdV barely exceeds 50% even when all of the wind and hydro power the grid can accept is sent to the grid. This number is of course dependent on wind speeds over the last year being representative of a typical year, but Figure 10 suggests that they are not exceptional:
Figure 10: Smoothed daily average wind speeds at El Hierro airport since January 1, 2014
The details of Hubert’s analysis are provided in the Appendix at the end of the post.
Finally comes the $64,000 question:
What does GdV’s performance tell us about the potential of renewable energy?
The answer is simple. Intermittent renewable energy is not going to replace dispatchable fossil fuel generation without adequate energy storage backup, and since the amount of energy storage needed is almost always prohibitive it follows that an energy future based entirely on intermittent renewables is not a realistic prospect. As discussed at length in previous posts the only way to integrate significant amounts of intermittent renewable energy with the grid is by maintaining enough dispatchable capacity to cover demand when the wind doesn’t blow and the sun doesn’t shine. GdV has in fact already effectively defaulted into this operating mode.
The unexpected difficulties experienced in stabilizing the El Hierro grid at high wind penetration levels also come as an unpleasant surprise. It is not clear to what extent larger and more stable grids will experience similar problems, but the assumption that any problems of this type can be easily overcome with appropriate technology may require review.
Yet one would never know that anything was wrong from recent press releases. On July 8 GdV will host its first conference, which will be attended by representatives from other countries anxious to replicate GdV’s “success”. Here is an excerpt from the release (my translation):
Wind and solar are variable and fluctuating sources that by themselves are not capable of supplying constant energy, which results in generation limitations in vulnerable isolated systems, which in general do not cover more than 30% of demand*. GdV, which combines unstable wind generation with hydro generation, has been capable not only of making the maximum use of the available resource, substantially exceeding these generation limitations, but on numerous occasions has been the sole source of generation for the island.
*I have no idea which systems these are or where the 30% number comes from.
The second sentence stands out. It would in fact be difficult to cram more misrepresentations into a single short sentence. GdV has not made maximum use of the available resource – generation from the 11.5MW wind farm is routinely curtailed at 7MW and much of the wind power that remains is wasted pumping water uphill. The 11.3MW hydro system has generated an insignificant amount of electricity. The renewables penetration achieved in GdV’s first year of operation does not “substantially exceed” 30%. Renewables have been “the sole source of generation” for only 241 out of 8,880 operating hours, or less than 3% of the time. For 969 hours (11% of the time) renewables generated no energy at all. But of course we never get to read about that.
APPENDIX: Hubert Flocard’s Analysis
June 2016
Diesel 1793.33 MWh
Demand 3891.67 MWh
Renewable fraction 53.92 %
NB : On June 2 there are two missing lines which I have replaced by linear interpolation (my usual way of handling missing data)
From July 1st 2015 to June 30th 2016
Diesel 29768.48 MWh
Demand 45517.93 MWh
Renewable fraction 34.60 %
Wind 24257.93 MWh
Wind turbines load factor 24.01 %
Maximal achievable renewable fraction 51.33 %
(using wind or hydro as much as possible – no loss of wind energy – and diesel when either wind or hydro power is missing). The value decreases to 48.38 % if one asks that diesel never gets below 25 % of average demand. Then again there is no loss of wind energy (but a larger fraction is returned as hydro production with the associated 40 % loss)
Maximal achievable fraction without GdV hydro component and diesel never below 25 % of average demand : 41.01 %
Only 76.95 % of wind production can be used. The rest is lost.

Monthly renewable fraction (red line = yearly average)
Daily renewable fraction
Hourly renewable fraction
Fraction of demand covered by each production (52704 intervals of 10’ each) Diesel = grey, Wind to the grid= green, hydro to the grid ) blue.
Fraction of time in % (over 52704 intervals of 10’ each) with diesel covering a given fraction of the demand. The 00-05% bar corresponds always to 100 % renewable fraction. The 95-100 % bar to (almost) all the demand being covered by diesel production.
Wind power (MW) over 52704 intervals of 10’ each
Power (MW) Wind to the grid = dark green, Wind to pumping (lower bound) = light green, Hydro to the grid = blue.
Electric production (MW) Diesel = grey, Wind to the grid = green, Hydro to the grid = blue
Fuente: http://euanmearns.com/el-hierro-completes-a-year-of-full-operation/

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