Renewable Electricity and the Grid – The Challenge of Variability

Citation

Dow, S. (2009), "Renewable Electricity and the Grid – The Challenge of Variability", International Journal of Energy Sector Management, Vol. 3 No. 2, pp. 219-220. https://doi.org/10.1108/17506220910970605

This book is a welcome addition to the literature on renewable electricity. Too often, there is simply an assumption that because policy decides that renewables are desirable, then more investment in renewables will simply happen automatically. The book looks at the reality of trying to add renewables to the grid – given that the output is variable, adding capacity is not as simple as it might first appear.

The book is a collection of chapters looking at issues surrounding connecting variable (unreliable) generation sources to grids. By definition, collections of chapters tend to leave space for minor contradictions, which is certainly the case here. The most obvious contradiction is in the level of variable capacity which can be connected before problems arise – there is no single answer to the question. There are other issues where the chapters have minor disagreements – and adding the issue of combined heat and power always tends to cause problems. CHP sells electricity only where it is also selling heat – and there is no point whatsoever in switching off the generation source (even if it is actually physically possible) when the heat is being produced. CHP does not fit well with merit orders, and tends to lead to problems in allocating fixed costs between the heat and the electricity sales.

Similarly, unreliable power does not sit well with merit orders simply because there is no point in trying to predict when the plant will be online in the future. Instead, the system is set up to take the power whenever it is produced. The flexibility is found in some other part of the system. Creating a system which is completely reliant on renewables is difficult – although intriguingly there is a chapter which suggests it is not entirely impossible. There is also a chapter to show what the implications for fossil fuel will be given that it is those sources which must bear the brunt of flexibility until such time as more commentators agree that the hurdle can be jumped.

One of the most challenging parts of the renewable power sector is finding ways to make future output more predictable. Better wind modelling, and forecasting, is clearly important. Again such crucial issues are covered – although there is no overall view on how big an improvement can be expected or even hoped for.

No book on the subject would be complete without consideration of the costs of variability. That informs the key question – is it worth it? The chapter does not attempt to answer the question, but it does help inform the debate. The book tends to assume that renewables capacity will only grow. Given wider policy drivers, that is a reasonable assumption particularly in the European Union. But it must not be forgotten that there are still choices to be made regarding the future role of renewables. It cannot be assumed that renewable power is the only answer for the future.

This book is informative, interesting, and occasionally quite challenging. What it lacks is an overall theme, which is probably inherent in the nature of collecting chapters. It is easy to forgive small inconsistencies, but the book also leaves the reader to determine the overall message. On a selective reading of the chapters, it is possible to conclude that the message is that the march of new renewable capacity is unstoppable. On reading it all, there is a realisation that this book is remarkably cautious given the political fervour for renewables. That alone makes this book worth reading – it shows the world is more complex than political rhetoric might suggest.