Industrial Engineering

Innovation at Sea: Lowering the Costs of Offshore Wind

Engineering Magazine October 2019
http://www.arup.com/

The world needs renewables that are large scale and produce dependable, valuable energy at acceptable cost.

The key to expanding the development of offshore wind energy is bringing down development and operating costs. This would spur innovation and expand the market for off-shore wind, but how do we get there?

Offshore wind must either provide significantly cheaper energy or overcome intermittency issues to preserve the value of the power it generates. Both options present significant challenges, but new innovations for these are evolving, so how can developers and investors best navigate risks in this market?

Storage makes renewables viable

Storage will become an essential component of more electricity grids as the proportion of energy from renewables rises. Once a grid is depending on renewables for up to 40% of its power, the intermittency issue becomes a threat to supply.

There are different options for storing offshore wind energy, some more cost effective than others. It could be done on a developmentby-development basis, with storage at each wind farm used to even out peaks and troughs in generation. Wind turbines are now available with small, integrated battery storage that can help even out generation in gusty winds, for example. Larger battery systems have been proposed for integration into wind farm development, offering improved power quality.

Whilst addressing power quality is an improvement, storage at utility scale to shift power supply by hours, days or months is the real goal. Mostly, this involves converting this intermittent power into some form of alternative potential energy. Hydropower or pumped storage could offer to fill this gap, with the ability to pump water uphill at variable rates and reverse the flow to service base load or address peak demand. Pumped storage has the scale to shift wind power supply by hours and days.

Concepts for better generation

Various gravity-based systems are currently being proposed across the market. These involve some form of raising mass to a predetermined height, and then lowering later, using reverse electromagnetic systems to reclaim the energy as the mass is lowered. The challenge is to deal with the larger loss in efficiency of this energy conversion. In addition, other systems are proposed to use the energy to pressurise air, then later release the pressure to drive turbines. And still more proposals include liquefying air, then later converting back to gas and as the air expands, to power turbines. In each case, the goal is to convert and shift, the variable power from wind turbines to be more productive and at a consistent base level.

Third parties, separate from the wind power producers, could enter the market. Getting paid to supply storage as a service to manage intermittent sources – including wind – and supply energy on demand, is an attractive concept. With spot prices for wind near zero at certain times of day, there’s a clear opportunity to store energy and sell it when prices are higher.

In emerging markets such as the USA, it’s vital that developers and grid operators keep an open-mind about the offshore wind business model. The challenges are real, but the potential for cost effective renewable power is there, and it’s increasingly achievable.

Designing down the costs

How else can the costs of offshore wind be reduced? Bigger turbines are one option – enabling the same power from fewer turbines whilst reducing the associated infrastructure. Offshore turbines have now reached 12MW and there are plans for larger. At the same time, operators and turbine manufactures are constantly improving the operational efficiency and conversion rate of the turbines. For its newest offshore wind turbine, GE is publishing a capacity factor of 63%, higher than typically used for the industry.

But how big is too big? Larger turbines are more challenging to install which pushes up the costs. There’s already talk about the need to invest in a new generation of installation vessels to cope, perhaps offsetting the gains in the turbines. So, the industry has continued to look elsewhere for cost efficiencies.

The focus has moved to the design of foundations. Monopiles have proven their worth, but bigger turbines in deeper water push the limits of this technology, and the industry has been investing in monopile design and research. Key advances in design have resulted in cost savings, reduced instillation times and the removed the standard transition piece. The European market has looked to jackets – truss structures with piling – as a solution but has so far struggled to deliver them on time or on budget. In the long term, floating turbines may be the answer and encourage innovation but, in the meantime, the industry must redouble its efforts for jackets and monopiles to refine the design to reduce cost, risk and schedule.

Sizing up substations

The cost of substations could be reduced through new structural approaches. Currently, substations typically weigh more than 2,000 tonnes – more than a turbine-installation vessel can lift – so they need specialist heavy-lift vessels. These can be expensive and they are in short supply in the markets such as the US. Smart design of infrastructure can reduce the size of substations and make them self-installing, enabling significant cost reduction.

Then there’s the issue of who owns the substations. In some European markets, it is utility companies, leaving wind farm developers to concentrate on the turbines. Emerging markets such as the USA, Japan or Taiwan face a choice between this approach or asking developers to take all the risk and build not only the turbines but also the substations and other infrastructure needed to get the electricity to shore. A clear approach to substation development from the outset of a programme can make distribution of generated power less complex. Establishing a strong relationship with local network operators is key to this and can ultimately reduce risk and cost. Realising the potential

It’s not possible to overcome the sector’s current challenges immediately. However, the earlier decisions are made – such as opting for self-installing substations– will ultimately have a big impact on costs and viability.

By keeping technical innovation at the heart of a proposed development, costs can be lowered and the true commercial potential of offshore wind can be realised.

It’s essential to look at an offshore wind development as one entire programme rather than split into segments, with a trusted and experienced supply chain to support the development. In an emerging market, costs can escalate and risk can be heightened, but by having the right experts on board the risks and cost implications can be successfully navigated.