The deployment of wind energy in cold-climate (CC) areas is growing rapidly. CC sites - the definition covers low-temperature and icing climates - are becoming more attractive because of high wind speeds, increased air density resulting from low temperatures, and low population density.
In many European countries, the move to CC sites has been prompted by the fact that the more-easily exploitable inland areas are already in use.
However, CC conditions bring extra challenges to wind-power projects, such as ice accretion on rotor blades and instruments, and demand specialist choices in materials, lubricants and cold start-up procedures.
Blade icing decreases energy production and potentially reduces the wind turbine's mechanical lifetime, which could impact the efficiency and profitability of the project. Additionally, iced blades increase noise emissions and generate ice throw, posing environmental and safety issues for project workers and local residents.
To resolve some of the main CC challenges, the International Energy Agency (IEA) established a task force, IEA Wind Task 19, which has been gathering and coordinating recommended practices on cold-climate wind energy since 2002.
The first global CC market study for 2012-2017 was published in the BTM World Market Update report in 2013, and estimated that by the end of 2015, up to 100GW of cumulative wind capacity would have been installed in CC areas.
The forecast horizon of the BTM study ends in 2017, so Task 19 has decided to update the market estimate to cover 2016-2020.
Mapping cold-climates sites
Accurate information on icing and low-temperature climates is needed to estimate the size and potential of the CC market.
Historical observations of in-cloud icing conditions (known as meteorological icing) at 150 metres above ground level were used to create a map of icing climates. Low temperature regions (experiencing several days below –20C) were estimated using global re-analysis weather data.
A commercial global wind-farm database, with site-specific coordinates and capacity information, was used to categorise all global onshore wind farms as non-CC, low-temperature climate, icing climate or both of the latter.
Icing climate sites were categorised according to their meteorological icing using the IEA ice classification (see table, below). Sites in ice classes 2-5 were labelled as icing-climate sites.
Country specific market forecasts for 2016-2020 were obtained from the BTM World Market Update 2015, and combined with the low-temperature and icing information to estimate the CC market potential in this new market study.
This new market study shows a cumulative capacity of 127GW at the end of last year, a 28% increase from BTM's previous analysis (see map). The forecast for the end of 2020 shows a total installed capacity of 186GW, indicating a remarkable 30% share of global forecasted wind capacity.
Around 12GW of new CC capacity will be built each year. By comparison, the average annual growth rate for offshore wind is forecast at around 4GW, making the CC market nearly three times the size of offshore wind.
In cumulative capacity, the largest CC market areas are North America, Europe and Asia (see map).
Compared to the previous BTM analysis, the largest capacity increase - in both low-temperature and icing climates - is in the North American market. Europe leads the way in terms of icing sites, with nearly 62GW forecasted to be installed by the end of the decade.
Scandinavia provides the largest amount of moderate to severe icing sites (Ice Class 3 and above), followed by Canada, but a large portion of the total icing markets are found in central Europe and the US in Ice Class 2 climates. Asia dominates the low-temperature climate market, but has very few icing sites.
There is vast potential for profit when building large onshore wind farms in CC conditions and remote locations. But special care needs to be taken to minimise the extra risks and costs asscociated with building wind projects in these conditions.
This is the mission of IEA Wind Task 19: "To write and disseminate state-of-the-art and recommended practices that enable safe and economically viable projects in CC conditions."
Based on its cumulative and combined experience of CC conditions, IEA Wind Task 19 has developed six recommendations to help project developers plan and build better and safer CC wind projects.
- Be aware of the extra risks and costs of CC wind-energy production at the early stages of the project
- Use latest Task 19 recommended practices report for best procedures in CC project development
- Use Task 19 available technologies report to find lists of existing CC technologies
- Start screening of potential sites using the icing maps from the available technologies report, which also provides information on warmer climate sites in high elevation locations
- If the pre-screening process shows a site of IEC class 2-5, always perform on-site icing measurement, for at least one year at hub height, and apply a long-term adjustment
- Discuss with turbine manufacturers how their technology is suited for site-specific icing and low-temperature conditions. Request turbine performance data either via simulations field or lab test report, preferably, scada data from sites with similar climatic conditions, especially regarding icing and low temperature operations. Review turbine control strategy in icing conditions.
Of course, reality is often more complex than following a six-point list, but the recommendations above include the most crucial steps required to build a profitable CC site.
The cold climate market is one of the largest "non standard" sectors for wind energy today, and with a huge potential that remains untapped. These sites are reasonably low cost, with excellent wind resources during winter when electricity market prices are typically high.
The market for building new CC wind farms and creating technologies that solve the toughest challenges are there for the taking. The business potential for enhancing existing technological solutions, and especially creating new low-cost solutions for light icing sites, is massive.
Through better international research and development efforts, involving industry as well as research institutes, the wind energy sector will find a new source of affordable onshore sites with excellent wind resources and large business potential in CC locations.
Ville Lehtomaki is a senior scientist at the VTT Technical Research Centre of Finland. He will be speaking at Windpower Monthly's Optimising Wind Farms in Cold Climates event, 6-8 December, Helsinki, Finland
IEA ICING CLIMATE SITE CLASSIFICATION