Because of generally low wind strengths the Gorona del Viento (GdV) plant achieved only 28.2% renewables generation in November and December 2016. Percent total renewables generation since full operations began in June 2015 stands at 37.7% at the end of 2016, down slightly from 38.7% at the end of October 2016. Renewables generation for the calendar year 2016 was 41.1%. Minor improvements are apparently being made in wind turbine performance but hydro generation remains negligible overall. Data on GdV plant layout, operation and capacities are given in the September 2015 review. Previous posts on GdV are accessible through the El Hierro portal.
Figure 1 shows daily mean percent renewables generation since June 27, 2015 (data from Red Eléctrica de España (REE). The 100% renewables target remains as elusive as ever:
Figure 1: Daily average percentages of diesel & renewables (wind plus hydro) sent to the El Hierro grid. The month scale is not exact
The Table below updates the monthly grid statistics since startup on June 27, 2015 through December 31, 2016, a total of 18 months of operation. The “percent of El Hierro total energy demand” numbers are again based on El Hierro obtaining 23% of its total energy needs from electricity and are italicized to signify uncertainty because the 23% estimate is not verified.
Figure 2 plots the REE 10-minute generation data for November and December. The renewables percentage for these months exceeds 20% because of three periods of stronger winds – between November 7 and 12, December 15 and 18 and December 29 and 31. Wind generation was minimal for most of the rest of the time, as was hydro – there was in fact no renewables generation at all for 202 hours during the two months. This was, however, partially offset by a 30-hour, 100% renewables test conducted on November 12 and 13.
Figure 2: Generation by source, November & December 2016
The grid failures on December 30 are also of note. These occurred during a period of very strong winds and began with an abrupt decrease in the amount of wind power sent to the grid, suggesting that the turbines had to be feathered. Grid restart was achieved using hydro alone. Figure 3 shows details:
Figure 3: Details of December 30, 2016 grid outages
While it’s hard to pick any positive trends out of the GdV data there is one area in which some progress is being made – wind curtailment during high wind periods. We have usually cited 7.5MW as the curtailment level for GdV’s Enercon turbines, but as shown in Figure 4 maximum wind generation has gradually been creeping up, reaching a high of 8.8MW in December. There is also a visible correlation between percent renewables and maximum wind generation which although weak (R squared = 0.25) suggests that the increase in wind generation may be having a positive impact on renewables percentages:
Figure 4: Percent renewables generation vs. maximum wind generation by month since project startup.
This impact, however, is unlikely to add more than a percentage point or two to GdV’s output because it increases wind generation during high wind periods when wind generation often exceeds demand (and therefore has to be wasted anyway) but does nothing to increase it during low-wind periods when the extra power is needed. And the problems with the hydro system, which now seems to be incapable of delivering more than a few tens of MWh of uninterrupted power before shutting down, remain.
The REE grid data:
The daily 10 minute REE grid data for El Hierro between project startup on June 27 and December 31 2016 have been combined into a continuous data series that is now accessible on the El Hierro portal. Variables are date/time, demand, diesel generation, wind generation and hydro generation. Users are reminded that total generation is diesel + wind + hydro and that the hydro value is the sum of hydro generation and energy used to pump water uphill, meaning that it is not possible to derive individual hydro and pumping values from it. Hydro is commonly negative because uphill pumping usually exceeds hydro generation.