Wind and solar performance maps from Vaisala, a Finnish manufacturer of environmental sensors, have found that the same meteorological conditions behind the current heatwave in Western Europe have contributed to a wind drought, negatively affecting wind energy performance in markets including the UK, France, Spain, Germany and Scandinavia. Simultaneously, solar plant performance in many of these markets has increased, illustrating the importance of including both technologies as part of a diversified, climate-resilient energy portfolio. The maps show that wind farm operators saw resources dip by as much as 20% in July 2018 from long-term averages, while solar irradiance in many of the same markets was up to 20% above average. For wind energy asset owners and operators in the UK, France, Spain and parts of Germany, Julys substantially below par wind speeds followed similarly low winds in May and June. In Scotland, meanwhile, wind speeds have been uniformly down for the whole seven months of 2018. This trend is likely to have a long-term impact on the financial performance of Scottish wind farms, and has already been noted in the financial results of major utilities. These conditions follow another notable wind drought across the USA in 2015, which had widespread financial impacts. Dr Pascal Storck, director of renewable energy, Vaisala, said, The 2015 conditions caused many wind energy investors in the USA to think very seriously about how they could diversify their portfolios, not just geographically, but also by technology. This new data shows that large-scale anomalies are not a one-time occurrence, and it may be time for the European market to follow suit in thinking about how it can become climate resilient. Often wind and solar technologies are played against each other, but the reality is that a diverse portfolio, obtained by building out both, to a large scale, will be the solution to long-term variability of this nature. Energy storage has a role to play in smoothing out fluctuations at an hourly or perhaps daily basis, but using storage to manage variability on a monthly basis is likely to be cost-prohibitive. The importance of diversification was clearly evidenced in Germany, for instance. While the countrys wind and solar capacity have both increased in the last year, wind energy production for July 2018 was 20% lower than the same month in 2017, a drop of 1.1TWh in generation, or the equivalent of a 10GW reduction in generation capacity (assuming a typical summer capacity factor of 15%). However, this shortfall was more than compensated for by a 26%, or 1.4TWh, increase in its solar energy production in the same period. That said, not all markets saw this balancing effect. Portugal, for example, experienced both low winds and low irradiance in July. This highlights the need for robust forecasting and financial planning on a project-by-project basis to account for the impact of site-specific conditions on energy production and returns. Ultimately, investment in robust, site-specific weather and climate data remains a critical requirement particularly as the European market enters a post-subsidy phase in which project margins are getting tighter and the impact of any resource shortfall is felt more keenly than ever, Storck concluded. To view and download Vaisalas wind and solar performance maps, click here.