Recently there has been much rejoicing in the green media that the entire country of Portugal succeeded in powering itself with 100% renewables for four straight days from May 7 through May 10, 2016. Here we look into the question of whether this is true (it is) and second the question of what caused it (the weather). Over the period in question Portugal was able to make maximum use of its hydro and wind capacity because of unusually heavy rains (inset) and strong winds, a combination of renewables-favorable weather conditions that has been described as “fantastic”, although the tourism industry may take a different view.
The data used in this post are from the REN Portuguese grid website.
Installed capacity in Portugal at the end of 2014 and 2014 generation by source are as shown in the Table below. Portugal’s peak demand is around 8.5GW, or about half of the country’s total installed capacity:
Because of its relatively high hydro and wind capacity Portugal generated 63% of its electricity from renewables in 2014. It’s not hard to see how a spell of unusually wet and windy weather could increase this to 100%. Calm, dry, sunny weather would of course have the opposite effect, particularly with solar contributing only 1% to Portugal’s total generation, but good weather isn’t considered in this post.
REN, the Portuguese grid provides 15 minute grid readings separately for each day. Figure 1 shows the graph for May 10, 2016, during the period of 100% renewables generation:
Figure 1: REN grid data graph, May 10, 2016
A few comments on the REN data before proceeding. First, clicking on “download” brings up a spreadsheet with all the numbers, but the decimal point is a comma rather than a period. So one has to do a little work to translate the data into usable numerical format.
Second, some translations, courtesy of Luis da Sousa:
Bombagem = pumping (pumped hydro)
Carvao = coal
Albuf (Albufeira) = conventional hydro
Fios de Agua = small hydro
PRE = “Special Regime” generation with grid priority
Third, a notable feature of Figure 1 is the large difference between generation and demand. This occurs because the graph ignores exports. Generation and demand are in close balance when exports and pumping, which is a load on the system and therefore included as demand, are allowed for.
Figure 2 shows total generation from May 1 through May 19, 2016, covering the May 7 to 10 period of 100% generation. This was clearly a period of strong winds – in fact it seems that hydro, which was already generating abundant power because of the April floods, was cut back to accommodate the extra wind:
Figure 2: Portugal generation by source, May 1 through 19, 2016.
Figure 3 compares renewables generation with demand. Renewables generation includes the following:
- Non-PRE and PRE hydro
- Thermal (assumed to be biomass or biofuel used in electricity generation)
Demand is estimated as demand plus pumping, which as noted above is reported as load.
Figure 3: Portugal renewables generation versus demand, May 1 through 19, 2016
The interesting thing is that not only did Portugal meet its electricity demand with 100% renewables between May 7th and 10th, it exceeded it by a substantial margin (the surplus power was exported). The May 7 to 10 time period is also conservative. According to Figure 3 demand was met or exceeded by renewables between late on May 6 and the morning of May 12. Moreover, generation and demand track each other so closely after May 12 that one gets the impression that with a little bit of extra effort Portugal could have filled 100% of demand with renewables all the way from May 7 through May 19 (renewables generation exceeded demand by 6% in the first 19 days of May). In short, the greens are understating their case, something I have never seen happen before.
But what does it all signify? These quotes from the Guardian are typical of the reaction of the green community:
Oliver Joy, a spokesman for the Wind Europe trade association said: “We are seeing trends like this spread across Europe – last year with Denmark and now in Portugal. The Iberian peninsula is a great resource for renewables and wind energy, not just for the region but for the whole of Europe.”
“An increased build-out of interconnectors, a reformed electricity market and political will are all essential,” Joy said. “But with the right policies in place, wind could meet a quarter of Europe’s power needs in the next 15 years.”
James Watson, the CEO of SolarPower Europe said: “This is a significant achievement for a European country, but what seems extraordinary today will be commonplace in Europe in just a few years. The energy transition process is gathering momentum and records such as this will continue to be set and broken across Europe.”
To draw such conclusions from a spell of unusually bad weather in Portugal is of course good publicity, but to claim that a spell of bad weather in Portugal represents an achievement for renewable energy is nonsense.