A good forecast for onshore wind

Jon Masters
05 January 2016

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Prospects for expansion of onshore windpower still look good in Scotland, without Government subsidies, but with a viable future owing to developing technology, the sector’s maturity and industry’s expertise. This is the view from Tony Gee & Partners, reports Jon Masters.

Government in Westminster confirmed in October this year that indeed, as industry was expecting, subsidies for onshore wind will effectively come to an end from April 2016. The closing of the Renewables Obligation does not necessarily mean it’s all doom and gloom for onshore wind power, however; not in Scotland anyway.

Consultant Tony Gee & Partners is still upbeat about market prospects, partly as a reflection of views coming from some of the firm’s clients. So says Tony Gee infrastructure director Alasdair Fowler.

“Absolutely there is still a market. The Scottish Government remains very pro-renewable energy and we’re still hearing from our clients, from one major developer in particular, that they’re still feeling bullish about prospects,” Fowler says.

“The country already had a base load of hydro power generation, but this achievement of getting to 50% renewables, or close to it, has been reached mostly by encouraging development of onshore windfarms.”

Scotland has set an ambitious target of generating the equivalent of 100% of the country’s power demand from renewable sources by 2020. Projections published by Scottish Renewables in November this year show that Scotland will fall short of the target at its current rate of development, but not by much.

Energy from renewable sources is on course to reach 87% of equivalent demand by 2020 with a forecast installed capacity of 11.9GW. In June 2015 available capacity from renewables stood at 7.4GW, of which 5.2GW can be generated by onshore windfarms. According to Scottish Renewables, another 1.5GW will come on stream from projects under construction. Schemes that have secured planning permission and await construction will provide a further 990MW.

“Scotland had reached 44.5% of its power generation from renewables by the end of 2013, so by the end of this year it should be just about hitting its 2015 target of 50%,” Fowler says. “The country already had a base load of hydro power generation, but this achievement of getting to 50% renewables, or close to it, has been reached mostly by encouraging development of onshore windfarms.”

The changes to subsidy arrangements are likely to make further new projects difficult for smaller developers, Fowler says. “But we expect the larger promoters, who can provide the necessary capital funding, will still be able to develop more sites because the business cases should still stack up. It’s generally easier to make onshore schemes work in Scotland than it is in other parts of the UK.”

There is another reason for Tony Gee’s positive outlook for the onshore wind sector; that is the challenge of operating and repowering the first and second generation of existing windfarms.

“Smaller schemes are now possible with far more powerful machines and better controls that get more power at lower wind speeds and can maintain electricity generation in higher winds."

“Even if we stop building new sites over the next five years or so, there will still be a significant market in upgrades to increase power output and efficiency. Windpower technology is still developing.” says Fowler.

Energy companies have strong incentive to re-engineer their first generation windfarms, Fowler adds. One such site has had a further 19 wind turbine generators (WTG) built to add to an existing array of 45 WTGs. The additional 19 WTGs provided more power than the initial 45 strong development, which was just 10 years old when it was extended.

“Smaller schemes are now possible with far more powerful machines and better controls that get more power at lower wind speeds and can maintain electricity generation in higher winds. So overall the latest WTG models have a greater operating range and a bigger power yield,” says Tony Gee’s technical manager Peter McDonald.

There is a lot of work involved in upgrade projects; practically as much in terms of engineering as development of a new scheme. Furthermore, Tony Gee is looking at a significant amount of work for industry to do in renewing and re-engineering the transmission supply network. “This is another big opportunity for us,” says Fowler.

“During planning, developers are now keen to see the civils design considered early on to take the risk of delays to the construction programme due to amendments to planning out of the equation,”

“The majority of power supply for the north of Scotland used to come either locally from hydro power or the country’s central belt. But now the direction of supply is being reversed and much of the power generated in the north is going south. This has created the requirement to re-engineer the transmission network.”

This work to come will present another interesting phase in the evolution of onshore windpower in Scotland specifically and the UK in general. Clients have come to realise the importance of getting the engineering right at the front end of project developments.

“A trend we have seen in recent years, is that the larger developers now recognise that while the civil engineering is a relatively small part of overall scheme cost, the civils design is a vital part of risk to delivery.” McDonald says.

As a civil, structural and geotechnical engineering practice, Tony Gee & Partners is commonly involved in all aspects of windpower projects, from early scheme development, through to planning, detailed design and construction supervision.

“Schemes require modelling and design of supporting infrastructure including transport route assessments, access roads, local road improvements, WTG foundations and substation buildings. We’re often providing all of this,” says Fowler.

“During planning, developers are now keen to see the civils design considered early on to take the risk of delays to the construction programme due to amendments to planning out of the equation,” McDonald says.

“The sector has been through a painful learning curve in terms of WTG foundation design."

“Proper visual design representation is now common, as is high quality detailed ground investigation. Clients now recognise the importance of SI and that prices from contractors are not fixed if they don’t have knowledge of ground risks.”

Specifically with regard to WTG bases, clients have come to realise that design efficiency is not good value at the expense of successful operation. A number of developers now commission directly for the design of WTG bases. Technical knowledge has grown as the sector has matured.

“The sector has been through a painful learning curve in terms of WTG foundation design. There have been some cases historically where bases have been designed insufficiently for the high fatigue forces of larger WTG models,” McDonald says.

“There are many things to look at during early scheme development, such as siting and wind yield and supporting infrastructure. Crucially, however, the business cases demand developments are connected to the grid as soon as possible more than they need construction cost savings, so value engineering has been replaced by certainty of delivery.”

Scaling up of WTGs, from circa 1MW turbines to the 3MW machines now commonly built, has brought a more than three times magnitude increase in moment forces on base structures. Design codes are different for the task and the industry has recognised the change of requirements with a more rigorous approach, Fowler says.

“Most clients are now very strict on this. The design methodology has become more rigorous and holding down systems are more robust. We take a cautious approach to ensure long term operational success, and we consider close site supervision is essential to ensure construction is of the highest standard. We work with our clients to ensure they understand the importance of this.”

“We’re looking for construction efficiencies in the construction of the WTG foundations. Innovation comes from how we detail structures to make construction as rapid and straightforward as possible."

Efficiencies in WTG foundations are still there to be made, says McDonald. Bases are being designed to maximise the efficient use of materials while ensuring the required robustness of the structure is maintained. The bases are not necessarily three times larger in line with the magnitude of load increase of the bigger WTGs.

“We’re looking for construction efficiencies in the construction of the WTG foundations. Innovation comes from how we detail structures to make construction as rapid and straightforward as possible. This is what we’re trying to bring to the market all the time. Half a day saved on each base makes a lot of difference to the overall construction programme,” McDonald says.

Opportunities for efficiencies on foundation design are also coming from use of partially precast solutions. And rock anchors instead of simple gravity solutions are becoming economically viable with the new generation of turbines of 4MW and more.

Furthermore, a growing focus on high resolution imagery of what windfarms will look like is starting schemes off on the right foot and significantly speeding up processes that would otherwise rely on designs printed on paper.

“This is a significant change in the market, making a big difference to projects at planning stages,” Fowler says. “Having a 3D model of windfarm designs on a topographical image is helping to reduce visual impact and showing people what the windfarm will really look like when built. This is highly valuable material for developers.”