Floating wind farms for the future

FLOATING WIND FARMS FOR THE FUTURE

pre-insertion resistors for turbines

ARE FLOATING WIND TURBINES THE ANSWER TO RENEWABLE POWER?

Back in 2019, then-Prime Minister Boris Johnson promised 40 GW of UK offshore wind power by 2030. In early 2022, the Government raised that target to 50 GW, with an additional five GW from floating wind turbines. But are floating wind farms the solution to existing offshore power problems?

Many of us will be familiar with the sight of wind turbines. After all, there are more than 10,000 of the structures on land and at sea in the UK. In terms of efficiency, offshore wind turbines often have more favourable wind conditions, producing more electricity per turbine than their onshore counterparts.

But traditional offshore wind turbines have their limitations. Traditional offshore turbines are built onto a large steel column, fixed into a concrete foundation on the seabed. These can only be installed in relatively shallow waters, up to depths of around 60m. Not only does this limit the potential areas for turbine installations, it also means that the turbines have less access to the stronger winds that are often found further out to sea.

FLOATING FARMS

To capitalise on the stronger winds further out, floating wind turbines can be built instead. These are turbines built on huge floats, anchored to the seabed with weighted subsea cables.

Operating in much deeper water, floating wind farms make use of vast areas that were previously considered not suitable for offshore wind power. Being further out to sea also means that turbines can be a lot larger in size than their counterparts, producing even more electricity per turbine.

Kincardine, the world’s largest floating wind farm based in Scotland, has five operational floating wind turbines. Three cylindrical floats arranged in a triangular formation support each turbine, and pipes between the floats allow liquid ballast to be pumped around the structure. In this manner, the weight of the turbine can be shifted to stabilise it in harsh conditions, as well as orientating it for the wind direction.

Are we on track to meet solar power targets?

ARE WE ON TRACK TO MEET SOLAR POWER TARGETS?

MAXIMISING EFFICIENCIES TO MEET RENEWABLE TARGETS

In April 2023, a report published by the House of Commons stated that, at the UK’s current pace of change, it will miss its target of decarbonising the power sector by 2035. As the UK fights to secure its energy supply, what progress is being made in the renewable sector, and what needs to change? In this article, Simone Bruckner, managing director of resistor manufacturer Cressall, explores.

More and more applications are going electric. Whether it’s the cars we drive or the heat pumps in our homes, rising electrification is putting more pressure on the grid. In fact, the UK’s electricity demand is expected to double by 2035.

60 per cent of our current electricity usage comes from low-carbon sources, which includes renewables and nuclear power. But within the next twelve years, renewables are expected to supply up to 90 per cent of the country’s power if we’re to meet decarbonisation targets. In real terms, this sets a target of around 150 GW of renewable energy. But this is a long way off our current capacity of just 40 GW.

Further efforts to secure the UK’s energy independence while meeting decarbonisation targets have resulted in additional goals. The British Energy Security Strategy has outlined a 50 GW target for offshore wind by 2030, as well as a 70 GW target for solar by 2035.

But with a current solar capacity of just 14 GW, is the UK on track to meet such targets?

DELVING INTO SOLAR

One of the biggest issues faced by those in the solar sector is obtaining planning permissions and approvals. Industry body Solar Energy UK reported back in 2021 that around 17 GW of new projects were in the planning pipeline, with just under 800 MW of new projects entering the pipeline each month. But typically only around 500 MW of capacity is added each year, much lower than the approximate 4.5 GW required to meet the Security Strategy’s 70 GW target.

In Sleaford, Lincolnshire, a 600 MW solar farm able to power 190,000 homes is currently undergoing consultation with local residents. Despite being in talks now, if the plans for the farm are approved, it’s not expected to start construction until at least 2026.

Another problem with solar power is efficiency. Solar panels tend to operate with efficiencies between 15 and 20 per cent, compared to between 30 and 50 per cent for wind. Evidently, there’s improvements to be made to the efficiency of solar power if the UK is to hit its targets. But what can be done?

SAFE, EFFECTIVE MAINTENANCE

Maintenance is a key factor in improving efficiency. Regular cleaning and inspection ensures that the solar panels are working properly. But there might be times when the solar panel needs to be disconnected for more extensive maintenance or repairs, presenting an electrical safety challenge.

While there is still sufficient light, the solar panel will continue to produce electricity. This electricity must be discharged so that the panel can be handled safely. This can be done using a load bank, which dissipates excess electricity to allow safe disconnection, installation, and maintenance of solar panels.

THE BENEFITS OF MOTORISATION

Ground-mounted solar panels have the advantage of space, compared to those fixed onto rooftops. This means that the panels can be tilted and moved with respect to the sun’s position in the sky. An electric drive system is used to move the panels, either along a pre-programmed path or using information obtained via solar radiation sensors.

Moving the solar panels helps to maximise their efficiency throughout the day, as well as accounting for minute changes in the sun’s position and trajectory throughout the seasons. In fact, these systems can increase the output of solar farms by up to 35 per cent.

Motorising solar panels requires electronics that can ensure they move precisely and safely. To achieve this, a dynamic braking resistor (DBR) can be used. A DBR dissipates the excess voltage generated by the motors as they decelerate. As a result, the panels stop exactly when required, resulting in a more accurate positioning.

Though these slight changes in positioning may only be minute, when multiplied across an entire solar farm, they represent a significant proportion of its overall output and efficiency.

Finding suitable resistors for the solar sector can be a challenge. Cressall has vast experience in providing resistors for a variety of applications, including renewables. Offering resistors with no wearing components, they can last as long as the solar panels themselves, minimising downtime.

As deadlines get closer, pressure is mounting to provide a secure supply of green energy. Evidently, governments, planning regulators, energy companies and manufacturers will all have a part to play in the UK’s journey to green energy. As the House of Commons’ report states, the achievement of a decarbonised energy system will not come easily ─ but it is not impossible.

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Why are wind turbines being switched off?

WHY ARE WIND TURBINES BEING SWITCHED OFF?

POWER TRANSMISSION IS JUST AS IMPORTANT AS GENERATION

UK windfarms hit an all-time high in wind power last year, generating more than 80 thousand gigawatt hours (GWh) and enough power for over 22 million homes. Yet, reports also came out of wind turbines being switched off due to overcapacity — at the expense of customers.

Despite reaching impressive milestones in recent years, there’s a massive problem with the renewable — and particularly wind sector — power wastage. In 2022, it was reported that Brits paid millions to switch off wind turbines as networks were unable to deal with the levels of power generated.

The UK has set ambitious goals for renewable energy sources for the next few years, aiming for a more sustainable approach while reducing dependency on both fossil fuels and external suppliers. As the past 18 months or so have highlighted, the volatility of global markets means it’s essential that the country is able to secure its own energy supply.

Fortunately, the UK does have the natural resources to do so. With the greatest wind energy potential in Europe, it’s clear why wind power has been a preferred route for planners and developers to take. So why are wind turbines still being switched off, and why is this energy being wasted?

DISTANCE FROM THE GRID

Offshore wind farms are often a significant distance from the Grid. Typically, these farms are connected to the Grid with a specialist, individual cable connection through a converter and into the transmission network, allowing the farm to distribute power.

The issue with this setup is that the offshore system will typically have fewer connections readily available than an equivalent farm on land. Because of this, there are less options available when it comes to distributing power during surges or when there are problems with the on-land network.

DISTANCE FROM DEMAND

Furthermore, many of these wind farm installations are being built in remote areas of Scotland or in the North Sea, where winds are stronger. Though this is certainly positive when it comes to power generation, the issue is that the local area isn’t where the demand is.

More power is needed in the south of the country, far from where the electricity is being generated. And while the transmission networks can transport electricity great distances, without efficient connections and cable routes a lot of power can be lost before it reaches crucial areas.

A FOCUS ON INFRASTRUCTURE

It’s clear from these issues that improving power infrastructure is just as vital as delivering new power generation projects. Reassuringly, there are developments underway to address these issues. One such example is the ‘Eastern Green Link 2’ (EGL2), which involves the manufacture and installation of a high voltage direct current (HVDC) subsea cable from Peterhead in the North of Scotland down to Drax in Yorkshire.

A crucial element of these power transmission systems is the host of resistors within that help to facilitate the safe movement of electricity. Pre-insertion resistors, for example, can absorb and control transient magnetising currents within transformers throughout the network. This control helps keep voltages consistent with minimal dips, reducing potential disturbances for users of the power network. They can also help mitigate against temporary overvoltages, such as those caused by exceptionally strong winds.

Discharge resistors are another vital component, particularly in terms of safety. These can reduce the risk of sudden overvoltages from capacitors and inductors that have become isolated from their networks or in situations where an emergency shutdown is required. In offshore farms that are far from other connections, the inclusion of discharge resistors is essential in having a sufficient ability to remove excess electricity when required.

Implementing resistor technologies as new projects are built helps both to ensure safety from dangerous overvoltages, as well as safeguard electricity on the Grid from fluctuations and dips.

So, as the UK continues to invest heavily in the renewable energy sector, considering how we’ll transport this energy will be just as important as thinking about how we will generate it in the first place. With projects like EGL2 on the horizon, it’s clear that the industry is taking the right steps to secure a reliable network from the turbine all the way to our homes.

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Breaking the ice

THE ROLE OF RESISTORS IN POWERING ICEBREAKERS

Sea ice covers around twelve per cent of the world’s oceans, blocking the path for ships attempting to travel across the Earth’s coldest regions. Although they aren’t a new concept, icebreaker ships consistently play a crucial role in clearing these routes for trade, research projects and travel.


Icebreaker ships are a special class of vessel designed to break through even the thickest of ice sheets. Initially developed to open up trade routes that experience either seasonal or permanent ice conditions, ice breakers are commonly found in areas like the Barents Sea, Artic Ocean and the Saint Lawrence Seaway. More recently, they’ve also been used to support scientific research projects in the Arctic and Antarctic.

DETAILED DESIGN

To meet the challenges of ice-covered waters, icebreaker ships have a very specific, carefully considered design. The bow of an icebreaker has a unique shape that is smoother and rounder than a standard vessel, to allow it to easily glide over thick ice sheets with minimal opposing force. As it glides over the ice in this way, the weight of the ship descends onto the ice, crushing it and clearing the path.

To power the icebreakers to smoothly move over this difficult seascape, the vessels also require a significantly enhanced electric propulsion system that matches the power requirements for the icebreaker’s thrusters to break through the ice. 

As the sole enabler of transportation through these ice-covered waters, it’s essential that the propulsion system — and all of the components that it includes — are reliable, effective and safeguarded. If an icebreaker were to fail in transit, there could be major disruption to the global supply chain in the repair time. Think the Suez Canal fiasco in 2021, but much colder.

RELIABLE RESISTORS

One component that plays a crucial role in ensuring the safe operation of an icebreaker’s electric propulsion system is a dynamic braking resistor (DBR). When there is no ice in the vessel’s path, there’s less load on the system, meaning that any excess energy produced is surplus to requirements. To dissipate this excess energy, a DBR is integrated into the system, which acts as a load dump during propulsion and icebreaking activities. This load dump activity stabilises the power system, giving a constant load to the vessel’s gas engines.

It’s important to include a DBR in the electric drive system of an icebreaker for several reasons. Without the DBR, the power system would destabilise, risking potential damage to other components of the power circuit. If this continued, it could eventually lead to the loss of the vessel’s icebreaking function and complete failure of the power system.

Therefore, integrating a DBR is an absolute essential for icebreaker vessel design engineers. However, it’s not as simple as just selecting a DBR. There are several design elements for this specific application that must be considered to ensure the drive’s optimal performance.

MARINE MATTERS

When designing electrical components, like resistors, for use on icebreakers, there are several application-specific factors to consider. Each component needs to be able to withstand the salty, cold and unstable conditions that are common at sea. 

In terms of structural stability, conducting rigorous testing procedures like finite element analysis (FEA) provides evidence of a component’s ability to withstand unpredictable, inhospitable conditions. It’s also important to design in line with standards outlined by the global testing, inspection and certification specialists Bureau Veritas, for global compliance.

The saline atmosphere at sea is corrosive, so selecting the right material is essential to prevent salty sea water from leaving equipment inoperable. For metal components, it’s important to use stainless steel with a chromium content of at least 10.5 per cent. This enables the stainless steel to react with oxygen to produce a protective layer that prevent corrosion, even in an unpainted condition.

Icebreaker vessels are an indispensable part of the marine transport system. While their function is simple, having the right electrical components, including DBRs, designed specifically for icebreaking applications, is crucial to their safe and successful operation, making even the most treacherous of routes in the Polar regions accessible all year round.

Cressall designs and manufactures DBRs specifically for icebreaker vessels. Our team of expert engineers works together with our customers to develop the ideal, customer DBR solution for each application. For more information, please get in touch here.

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