Why it is necessary to separate hydro from non-hydro renewables

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Renewable energy statistics are presented in a variety of confusing and misleading ways, and often they do not mean what the average reader thinks they mean. We are regularly told about the growth of renewables strictly in terms of installed capacity. Gigawatts of wind, solar, hydro and other renewables are added together and compared with gigawatts of coal, natural gas, oil and nuclear. Yet, these numbers cannot be compared in an apples to apples manner. After all, 1 gigawatt of nuclear capacity will produce almost ten times as much electricity as 1 gigawatt of solar capacity installed in Bavaria.

Another form of confusion is the regular treatment of hydroelectricity. Do “renewables” include hydroelectricity? This may sound like a strange question. Is hydroelectricity not a renewable energy? Yet, the BP Statistical Review of World Energy divides global energy consumption into the following categories: Oil, Natural Gas, Coal, Nuclear Energy, Hydro-electric, and Renewables, with “Renewables” not including hydroelectricity.

A similar, and even more confusing approach, was taken by a recent UNEP report widely covered by the media, which lumped all “renewables” together to find that “renewables” had crossed the 100 GW of new capacity additions for the first time last year.

But how did they define “renewables”?

Here is what the original report says:

The following renewable energy projects are included: all biomass and waste-to-energy, geothermal, and wind generation projects of more than 1MW; all hydropower projects of between 1MW and 50MW; all wave and tidal energy projects; all biofuel projects with a capacity of one million litres or more per year; and all solar projects, with those less than 1MW estimated separately and referred to as small-scale projects, or small distributed capacity, in this report.

This is an arbitrary and confusing definition of renewables. Why are hydro projects of more than 50 MW excluded? This excludes most of the new hydro capacity being added globally. The reason given is unsatisfying:

The main body of the report also does not cover large hydro-electric projects of more than 50MW, since this technology has been mature for decades and is at a very different stage of its roll-out than, for instance, wind or solar.
I cannot argue that large scale hydro is more mature than wind and solar. But on what planet is small hydro not mature? Hydro power plants below 50 MW have been in operation since the time of Edison. And speaking of maturity, why is the burning of trees not classified as mature? Weren’t we getting most of our energy from burning wood around the time Moses parted the Red Sea? But these arbitrary, and often ideologically driven, definitions are a common feature of energy discourse.
So, here is a simple rule of thumb:
If you ever see renewable energy statistics, check how they treated hydroelectricity.
But what is to be done? My view is that renewables must always be disaggregated into hydro and non-hydro.
There are a number of reasons for doing this. First, it is to be intellectually and morally consistent. For example, many environmentalists are happy to cite statistics showing the supposedly rapidly growth of renewables in China, growth which is dominated by hydro. However, the same individuals will regularly say, with good reason, that the expansion of hydroelectricity in China has had many very undesirable consequences. We should therefore not lump together “good” and “bad” renewables. The same, of course, goes for many forms of biofuels, which are often little more than acts of taking food out of the mouths of babies and placing it into cars.
Second, there is the simple fact that hydroelectricity is not evenly distributed around the world, far from it. Here is a figure showing per-capita rates of production:
Per-capita hydroelectric production varies massively. Norway, the world’s number one producer, has per-capita production almost 20 times greater than Portugal, which is the number ten producer. These numbers can be particularly problematic in Europe. We regularly see news items with graphs comparing renewables in a variety of European countries. These graphs supposedly show that Britain and other countries are lagging behind in renewables. But they fail to account for the massive levels of hydroelectricity in some EU countries. Accounting for hydroelectricity (and biomass) can make things look a lot different.
Third, in most developed countries hydroelectricity has stopped growing. This is true for the EU and the US, where capacity has been essentially flat since 1980. In these countries, growth of renewables is not well understood if the relatively fast growing wind and solar sectors are lumped on top of an unchanging hydro sector. Disaggregation is necessary.
And finally, we have the problem of the varying output of hydroelectric dams. As I wrote last week, changes in weather conditions in China last year resulted in the output of its hydroelectric dams being 9% higher in 2014 than they would have been under the weather conditions of 2013. Lumping all renewables together and tracking growth in terms of changes in generation can clearly lead to unrealistic appraisals of inter-year changes. If it’s a wet year, renewables will appear to grow much faster than they did.
The alternative is if it is a dry year. In 2012, US hydroelectric output fell by 14%. This was without any changes in total capacity. In the preceding year the output increased by 22%. Again, this was without any changes in capacity. Clearly, year to year changes in hydroelectric output are not reliable proxies for changes in installed capacity.
So, separate hydro from non-hydro renewables, and be careful that year to year changes in hydro output aren’t simple due to the weather.