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How lasers reduce emissions

Drax laser

Of the air that makes up our atmosphere, the most abundant elements are nitrogen and oxygen. In isolation, these elements are harmless. But when exposed to extremely high temperatures, such as in a power station boiler or in nature such as in lightning strikes, they cling together to form NOx.

NOx is a collective term for waste nitrogen oxide products – specifically nitric oxide (NO) and nitrogen dioxide (NO2) – and when released into the atmosphere, they can cause problems like smog and acid rain.

At a power station, where fuel is combusted to generate electricity, some NOx is inevitable as air is used in boilers to generate heat. But it is possible to reduce how much is formed and emitted. At Drax Power Station, a system installed by Siemens is doing just that.

It begins with a look into swirling clouds of fire.

Not your average fireplace

“Getting rid of NOx is, at heart, a problem of getting combustion temperatures to a point where they are hot enough to burn fuel effectively. Too hot and the combustion will form excess amounts of NOx gases. Too cool and it won’t combust efficiently,” says Julian Groganz, a Process Control Engineer who helped install the SPPA-P3000 combustion optimisation system at Drax. “Combustion temperatures are the result of the given ratio of fuel and air in each spot of the furnace. This is our starting point for optimisation.”

An industrial boiler works in a very different way to your average fireplace. In Drax’s boilers, the fuel, be it compressed wood pellets or coal, is ground up into a fine powder before it enters the furnace. This powder has the properties of a gas and is combusted in the boilers.

“The space inside the boiler is filled with swirling clouds of burning fuel dust,” says Groganz. Ensuring uniform combustion at appropriate temperatures within this burning chamber – a necessary step for limiting NOx emissions – becomes rather difficult.

Heat up the cold spots, cool down the hotspots

If you’re looking to balance the heat inside a boiler you need to understand where to intervene.

The SPPA-P3000 system does this by beaming an array of lasers across the inside of the boiler. “Lasers are used because different gases absorb light at different wavelengths,” explains Groganz. By collecting and analysing the data from either end of the lasers – specifically, which wavelengths have been absorbed during each beam’s journey across the boiler – it’s possible to identify areas within it burning fuel at different rates and potentially producing NOx emissions.

For example, some areas may be full of lots of unburnt particles, meaning there is a lack of air causing cold spots in the furnace. Other areas may be burning too hot, forcing together nitrogen and oxygen molecules into NOx molecules. The lasers detect these imbalances and give the system a clear understanding of what’s happening inside. But knowing this is only half the battle.

A breath of fresher air

“The next job is optimising the rate of burning within the boiler so fuel can be burnt more efficiently,” explains Groganz. This is achieved by selectively pumping air into the combustion process to areas where the combustion is too poor, or limiting air in areas which is too rich.

“If you limit the air being fed into air-rich, overheated areas, temperatures come down, which reduces the production of NOx gases,” says Groganz. “If you add air into air-poor, cooler areas, temperatures go up, burning the remaining particles of fuel more efficiently.”

Drax Laser 2

It’s a two-for-one deal: not only does balancing temperatures inside the boiler limit the production of NOx gases, but also improves the overall efficiency of the boiler, bringing costs down across the board. It even helps limit damage to the materials on the inside the boiler itself.

Thanks to this system, and thanks to its increased use of sustainable biomass (which naturally produces less NOx than coal), Drax has cut NOx emissions by 53% since the solution was installed. More than that, it is the first biomass power station to install a system of this sophistication at such scale. This means it is not just a feat of technical and engineering innovation, but one paving the way to a cleaner, more efficient future.

What’s next for bioenergy?

Morehouse BioEnergy in Louisiana

Discussions about our future are closely entwined with those of our power. Today, when we talk about electricity, we talk about climate change, about new fuels and about the sustainability of new technologies. They’re all inexplicably linked, and all hold uncertainties for the future.

But in preparing for what’s to come, it helps to have an idea of what may be waiting for us. Researchers at universities across the UK, including the University of Manchester and Imperial College London, have put their heads together to think about this question, and together with the Supergen Bioenergy programme they’ve created a unique graphic novel on bioenergy that outlines three potential future scenarios.

Based on their imagined views of the future there’s plenty to be optimistic about, but it could just as easily go south.

Future one: Failure to act on climate change

Dams on river

In the first scenario, our energy use and reliance on non-renewable fuels like oil, coal and gas continues to grow until we miss our window of opportunity to invest in renewable technology and infrastructure while it’s affordable.

Neither the beginning nor the end of the supply chain divert from their current trends – energy providers produce electricity and end users consume it as they always have. Governments continue to pursue growth at all costs and industrial users make no efforts to reverse their own rates of power consumption. In response, electricity generation with fossil fuels ramps up, which leads to several problems.

Attempts to secure a dwindling stock of non-renewable fuels lead to clashes over remaining sources as nations vie for energy security. As resources run out, attempts to put in place renewable alternatives are hampered by a lack of development and investment in the intervening years. The damages caused by climate change accelerate and at the same time, mobility for most people drops as fuel becomes more expensive.

Future two: Growing a stable, centralised bioenergy

Rows of saplings ready for planting

A future of dwindling resources and increasing tension isn’t the only way forward. Bioenergy is likely to play a prominent role in the energy mix of the future. In fact, nearly all scenarios where global temperature rise remains within the two degrees Celsius margin (recommended by the Paris Agreement) rely on widespread bioenergy use with carbon capture and storage (BECCS). But how far could the implementation of bioenergy go?

A second scenario sees governments around the world invest significantly in biomass energy systems which then become major, centralised features in global energy networks. This limits the effects of a warming climate, particularly as CCS technology matures and more carbon can be sequestered safely underground.

This has knock-on effects for the rest of the world. Large tracts of land are turned over to forestry to support the need for biomass, creating new jobs for those involved in managing the working forests. In industry, large-scale CCS systems are installed at sizeable factories and manufacturing plants to limit emissions even further.

Future 3: The right mix bioenergy

Modern house with wind turbine

A third scenario takes a combined approach – one in which technology jumps ahead and consumption is controlled. Instead of relying on a few concentrated hubs of BECCS energy, renewables and bioenergy are woven more intimately around our everyday lives. This relies on the advance of a few key technologies.

Widespread adoption of advanced battery technology sees wind and solar implemented at scale, providing the main source of electricity for cities and other large communities. These communities are also responsible for generating biomass fuel from domestic waste products, which includes wood offcuts from timber that makes up a larger proportion of building materials as wooden buildings grow more common.

Whether future three – or any of the above scenarios – will unfold like this is uncertain. These are just three possible futures from an infinite range of scenarios, but they demonstrate just how wide the range of futures is. It’s up to us all – not just governments but businesses, individuals and academics such as those behind this research project too – to to make the best choices to ensure the future we want.

4 of the most exciting emerging technologies in electricity generation

Petri dish with microbe colony

Since the dawn of the industrial age, the world has been powered by a relatively small set of technologies. The 20th century was the age of coal, but this side of 2000, that’s changed.

The need to curb emissions and the rise of renewables, from wind to solar to biomass, has significantly changed how we fuel our power generation.

Today, some of the world’s most interesting and exciting emerging technologies are those designed to generate electricity.

Microbial fuel cells – harnessing the power of bacteria

Bacteria are all around us. Some are harmful, some are beneficial, but all of them ‘breathe’. When they breathe oxidation occurs, which is when something combines with oxygen at a chemical level, and when bacteria do this, electrons are released.

By connecting breathing microbes to a cathode and an anode (the positive and negative rods of a battery), the flow of these released electrons can be harnessed to generate power. This is what’s known as a microbial fuel cell (MFC). MFCs are used largely to generate electricity from waste water, but are expanding into more exotic uses, like powering miniature aquatic robots.

New developments are constantly expanding the power and applications of MFCs. Researchers at Binghamton University, New York found that combining phototropic (light-consuming) and heterotrophic (matter-consuming) bacteria in microbial fuel reactions generates currents 70 times more powerful than in conventional setups.

Building with sun shining through glass windows

Solar – a new dawn

Solar power may not be a new technology, but where it’s going is.

One of the most promising developments in the space is solar voltaic glass, which has the properties of a sheet of window glass but can also generate solar power.

Rather than collecting photons like normal solar does (and which transparent materials by definition can’t do) photovoltaic glass uses salts to absorb energy from non-visible wavelengths and deflects these to conventional solar cells embedded at the edge of each panel.

Or there’s solar PV paint, which contains tiny light sensitive particles coated with conductive materials. When layered over electrodes you’ve got a spray-on power generator.

Nuclear reactor hall in a power plant

Betavoltaics – nothing wasted from nuclear waste

Nuclear material is constantly decaying and in the process emits radioactive particles. This is why extremely radioactive material is so dangerous and why properly storing nuclear waste is so important and so expensive. But this waste can actually be put to good use. Betavoltaic devices use the waste particles produced by low-level radioactive materials to capture electrons and generate electricity.

The output from these devices can be fairly low and decreases over long periods of time, but because of the consistent output of nuclear decay they can be extremely long-lasting. For example, one betavoltaic battery could provide one watt of power continuously for 30 years.

And while they aren’t currently fit to work on a large scale, their longevity (and very compact size) make them ideal power sources for devices such as sensors installed on equipment that needs to be operational for long periods.

Ocean wave crashing at shore

Tidal power – changing tides

A more predictable power source than intermittent renewables like wind and solar, tidal power isn’t new, however its growth and development has typically been restrained by high costs and limited availability. That’s changing. Last year saw the launch of the first of 269 1.5 MW (megawatt) underwater turbines, part of world’s first large scale tidal energy farm in Scotland.

Around the world there are existing tidal power stations – such as the Sihwa Lake Tidal Power Station in South Korea, which has a capacity of 254MW – but the MeyGen array in Scotland will be able to take the potential of the technology further. It’s hoped that when fully operational it will generate 398MW, or enough to power 175,000 homes.

We might not know exactly how the electricity of tomorrow will be generated, but it’s likely some or all of these technologies will play a part. What is clear is that our energy is changing.

I am an engineer

Producing 16% of Great Britain’s renewable power requires innovative people with the right mix of skills, experience and determination. Running the country’s biggest power station is a team effort – but it’s worth taking a moment to hear from the individuals at the top of their game. Meet Luke Varley, Adam Nicholson, Gareth Newton, Andrew Storr and Gary Preece.

Getting more from less

There are few things in a power station as integral to generating electricity as the turbines. Making sure they run efficiently at Drax is down to Luke Varley and his team.

Luke Varley

Varley is the lead engineer in the turbine section at Drax Power Station. His team who look after what’s arguably the heart of the plant: the steam turbines that drive electricity generation. As well as managing day-to-day maintenance, the engineers and craftspeople within TSG deliver the major overhaul activities on the turbines to keep them running efficiently and safely.

Read Luke’s story

The problem solver

How do you convert a power station built for one fuel to run on another? It takes engineers with out-of-the-box thinking like Adam Nicholson.

Adam Nicholson

Nicholson is Process Performance Section Head at Drax Power Station. He has an eagerness to find solutions. That makes him the ideal candidate for his current job: managing day-to-day improvements at Drax.

His team makes sure the turbines, boiler, emissions, combustion, and mills are not just working, but running as smoothly as possible. It’s a job that brings up constant challenges.

Read Adam’s story

Taming the electric beast

To keep a site as big and complex as Drax Power Station running, you need to be ready to mend a few faults. That’s where Gareth Newton comes in.

Gareth Newton

As a mechanical engineer in one of the power station’s maintenance teams, he’s a man with a closer eye on that animal than most.

And when something does need fixing or improving, it’s his job to make sure it happens. It’s a task that keeps him busy.

Read Gareth’s story

The toolmaster

What do you do when a piece of equipment in the UK’s largest power station breaks down? More often than not, the answer is send it to Andrew Storr’s workshop.

Andrew Storr

Before Drax Power Station was a part of Andrew Storr’s career, it was a part of his local environment.

Today, Storr does more than strip the turbines, he’s part of the engineering team that oversees them – a job that needs to be taken seriously.

Read Andrew’s story

The life of an electrical engineer

Unsurprisingly, running the country’s biggest single site electricity generator requires top-class electrical engineers. That’s where Gary Preece comes in.

Gary Preece

A station like Drax doesn’t run itself. Its six turbines generate nearly 4,000 megawatts (MW) of power when operating at full load. Unsurprisingly, for a site that produces 7% of Britain’s electricity needs, the role of an electrical engineer is an important one – both when managing how power is connected to the high-voltage electricity transmission grid, and how the giant electrical machines generating the energy work.

Read Gary’s story

This is how you unload a wood chip truck

Truck raising and lowering

A truck arrives at an industrial facility deep in the expanding forestland of the south-eastern USA. It passes through a set of gates, over a massive scale, then onto a metal platform.

The driver steps out and pushes a button on a nearby console. Slowly, the platform beneath the truck tilts and rises. As it does, the truck’s cargo empties into a large container behind it. Two minutes later it’s empty.

This is how you unload a wood fuel truck at Drax Biomass’ compressed wood pellet plants in Louisiana and Mississippi.

What is a tipper?

“Some people call them truck dumpers, but it depends on who you talk to,” says Jim Stemple, Senior Director of Procurement at Drax Biomass. “We just call it the tipper.” Regardless of what it’s called, what the tipper does is easy to explain: it lifts trucks and uses the power of gravity to empty them quickly and efficiently.

The sight of a truck being lifted into the air might be a rare one across the Atlantic, however at industrial facilities in the United States it’s more common. “Tippers are used to unload trucks carrying cargo such as corn, grain, and gravel,” Stemple explains. “Basically anything that can be unloaded just by tipping.”

Both of Drax Biomass’ two operational pellet facilities (a third is currently idle while being upgraded) use tippers to unload the daily deliveries of bark – known in the forestry industry as hog fuel, which is used to heat the plants’ wood chip dryers – sawdust and raw wood chips, which are used to make the compressed wood pellets.

close-up of truck raising and lowering

How does it work?

The tipper uses hydraulic pistons to lift the truck platform at one end while the truck itself rests against a reinforced barrier at the other. To ensure safety, each vehicle must be reinforced at the very end (where the load is emptying from) so they can hold the weight of the truck above it as it tips.

Each tipper can lift up to 60 tonnes and can accommodate vehicles over 50 feet long. Once tipped far enough (each platform tips to a roughly 60-degree angle), the renewable fuel begins to unload and a diverter guides it to one of two places depending on what it will be used for.

“One way takes it to the chip and sawdust piles – which then goes through the pelleting process of the hammer mills, the dryer and the pellet mill,” says Stemple. “The other way takes it to the fuel pile, which goes to the furnace.”

The furnace heats the dryer which ensures wood chips have a moisture level between 11.5% and 12% before they go through the pelleting process.

“If everything goes right you can tip four to five trucks an hour,” says Stemple. From full and tipping to empty and exiting takes only a few minutes before the trucks are on the road to pick up another load.

Efficiency benefits

Using the power of gravity to unload a truck might seem a rudimentary approach, but it’s also an efficient one. Firstly, there’s the speed it allows. Multiple trucks can arrive and unload every hour. And because cargo is delivered straight into the system, there’s no time lost between unloading the wood from truck to container to system.

Secondly, for the truck owners, the benefits are they don’t need to carry out costly hydraulic maintenance on their trucks. Instead, it’s just the tipper – one piece of equipment – which is maintained to keep operations on track.

However, there is one thing drivers need to be wary of: what they leave in their driver cabins. Open coffee cups, food containers – anything not firmly secured – all quickly become potential hazards once the tipper comes into play.

“I guess leaving something like that in the cab only happens once,” Stemple says. “The first time a trucker has to clean out a mess from his cab is probably the last time.”

3 ways decarbonisation could change the world

Mitigating climate change is a difficult challenge. But it’s one well within the grasp of governments, companies and individuals around the world if we can start thinking strategically.

On the behalf of the German government, The Internal Energy Agency (IEA) and the International Renewable Energy Agency (IRENA) have jointly published a report outlining the long-term targets of a worldwide decarbonisation process, and how those targets can be achieved through long-term investment and policy strategies.

At the heart of the report is a commitment to the ‘66% two degrees Celsius scenario’, which the report defines as, ‘limiting the rise in global mean temperature to two degrees Celsius by 2100 with a probability of 66%’. This is in line with the Paris Agreement, which agreed on limiting global average temperature increase to below two degrees Celsius.

Here are three of the findings from the report that highlight how decarbonisation could change the world.

The energy landscape will change – and that’s a good thing

Decarbonisation will by definition mean reducing the use of carbon-intensive fossil fuels. Today, 81% of the world’s power is generated by fossil fuels. But by 2050, that will need to come down to 39% to meet the 66% two degrees Celsius scenario, according to the report. But, this doesn’t mean all fossil fuels will be treated equally.

Coal will be the most extensively reduced, while other fossil fuels will be less affected. Oil use in 2050 is expected to stand at 45% of today’s levels, but will likely still feature in the energy landscape due its use in industries like petrochemicals.

Gas will likely also remain a key part of the energy makeup, thanks to its ability to provide auxiliary grid functions like frequency response and black-starting in the event of grid failure.

Renewables like biomass will likely play an increasing role here as well, particularly when combined with carbon capture and storage (CCS) technology.

Overall, renewable energy sources will need to increase substantially. In the report’s global roadmap for the future, renewables make up two thirds of the primary energy supply. Reaching this figure will be no mean feat – it will mean renewable growth rates doubling compared with today.

Everyday electricity use will become more efficient 

The report highlights the need for ‘end-use’ behaviour to change. This can mean everyday energy users choosing to use a bit less heat, power and fuel for transport in our day-to-day activities, but a bigger driver of change will be by investment in better, more efficient end-use technology – the technology, devices and household appliances we use every day.

In fact, the study argues that net investment in energy supply doesn’t need to increase beyond today’s level – what needs to increase is investment in these technologies. For instance, by 2050, 70% of new cars must be electric cars to meet decarbonisation targets.

Infrastructure design could also be improved for energy efficiency – smart grids, battery storage and buildings retrofitted with energy efficient features such as LED lighting will be essential. There’s also the possibility of increased use of cleaner building materials and processes – for example, constructing large scale buildings out of wood rather than carbon-intensive materials such as concrete and steel.

Decarbonisation will cost, but not decarbonising will cost more

The upfront costs of meeting temperature targets will be substantial. A case study used in the report estimates that $119 trillion would need to be spent on low-carbon technologies between 2015 and 2050. But it also suggests another $29 trillion may be needed to meet targets.

However, failure to act could mean the world will pay out an even higher figure in healthcare costs, or in other economic costs associated with climate change, such as flood damage or drought. Therefore, the sum for decarbonisation could end up costing between two and six times less than what failing to decarbonise could cost.

On top of this, the new jobs (including those in renewable fuel industries that will replace those lost in fossil fuels) and opportunities that will be created between 2015 and 2050 could add $19 trillion to the global economy. More than that, global GDP could be increased by 0.8% in 2050, thanks to added stimulus from the low carbon economy.

Achieving a cleaner future won’t be easy – it requires planning, effort, and the will to see beyond short-term goals and think about the long-term benefits. But as the report demonstrates, get it right and the results could be considerable.

Why we need the whole country on the same frequency

Electricity frequency

The modern world sits on a volatile, fizzing web of electricity. In 2015 the UK consumed roughly 303 terawatt hours (TWh) of electricity, according to government statistics. That’s an awful lot of power humming around and, in this country, we take it for granted that electricity is controlled. This means the power supply coming into your home or place of work is reliable and won’t trip your fuse box. In short, it means your mobile phone will keep on charging and your washing machine will keep on spinning.

But generating and circulating electricity at safe, usable levels is not an easy task. One of the most overlooked aspects of doing this is electrical frequency – and how it’s regulated.

What is electrical frequency?

To understand the importance of frequency, we need to understand a couple of important things about power generation. Generators work by converting the kinetic energy of a spinning turbine into electrical energy. In a steam-driven generator (like those at Drax Power Station), high pressure steam turns a turbine, which turns a rotor mounted inside a stator. Copper wire is wound around the rotor energised with electricity, this turns it into an electromagnet with a north and south pole.

The stator is made up of large, heavy duty copper bars which enclose the rotor. As the rotor turns, its magnetic field passes through the copper bars and induces an electric current which is sent out onto the transmission system.

As the magnetic field has a north and south pole, the copper bars experience a change in direction of the magnetic field each time the rotor turns. This makes the electric current change direction twice per revolution and is called an alternating current (AC). There are in fact three sets of copper bars in the stator, producing three electrical outputs or phases termed red, yellow and blue.

Electrical frequency is the measure of the rate of that oscillation and is measured in the number of changes per second – also called hertz (Hz). A generator running at 3,000 rpm, with two magnetic poles, produces electricity at a frequency of 50Hz.

Turbine Hall at Drax Power Station

Why is this important? 

Maintaining a consistent electrical frequency is important because multiple frequencies cannot operate alongside each other without damaging equipment. This has serious implications when providing electricity at a national scale.

The exact figure is less important than the need to keep frequency stable across all connected systems. In Great Britain, the grid frequency is 50Hz. In the US, it’s 60Hz. In Japan, the western half of the country runs at 60Hz, and the eastern half of the country runs at 50Hz – a string of power stations across the middle of the country steps up and down the frequency of the electricity as it flows between the two grids.

Sticking to one national frequency is a team effort. Every generator in England, Scotland and Wales connected to the high voltage transmission system is synchronised to every other generator.

When the output of any of the three phases – the red, yellow or blue – is at a peak, the output from all other phases of the same colour on every other generating unit in Great Britain is also at a peak. They are all locked together – synchronised – to form a single homogenous supply which provides stability and guaranteed quality.

How is frequency managed?

The problem is, frequency can be difficult to control – if the exact amount of electricity being used is not matched by generation it can affect the frequency of the electricity on the grid.

For example, if there’s more demand for electricity than there is supply, frequency will fall. If there is too much supply, frequency will rise. To make matters more delicate, there’s a very slim margin of error. In Great Britain, anything just 1% above or below the standard 50Hz risks damaging equipment and infrastructure. (See how far the country’s frequency is currently deviating from 50 Hz.)

Managing electrical frequency falls to a country’s high voltage transmission system operator (the National Grid in the UK). The Grid can instruct power generators like Drax to make their generating units automatically respond to changes in frequency. If the frequency rises, the turbine reduces its steam flow. If it falls it will increase, changing the electrical output – a change that needs to happen in seconds.

In the case of generating units at Drax Power Station, the response starts less than a second from the initial frequency deviation. The inertial forces in a spinning generator help slow the rate of frequency change, acting like dampers on car suspension, which minimises large frequency swings.

Frequency on a fast-changing system

Not all power generation technologies are suited for providing high quality frequency response roles and as the UK transitions to a lower-carbon economy, ancillary services such as stabilisation of frequency are becoming more important.

Neither solar nor wind can be as easily controlled. It’s possible to regulate wind output down or hold back wind turbines to enable upward frequency response when there is sufficient wind.

Similarly, solar panels can be switched on and off to simulate frequency response. As solar farms are so widely dispersed and tend to be embedded – meaning they operate outside of the national system, it is not as easy for National Grid to instruct and monitor them. Both wind and solar have no inertia so the all-important damping effect is missing too. Using these intermittent or weather-dependent power generation technologies to help manage frequency can be expensive compared to thermal power stations.

Nor are the current fleet of nuclear reactors flexible – nuclear reactors in Great Britain were designed to run continuously at high loads (known as a baseload power). Although they cannot deliver frequency response services, the country’s nuclear power stations do provide inertia.

UK plug on blue wall

Twenty times faster

Thermal power generation technologies such as renewable biomass or fossil fuels such as coal and gas are ideal for frequency response services at scale, because they can be easily dialled up or down. As both the fuel supply to their boilers and steam within their turbines can be regulated, the 645 MW thermal power units at Drax have the capability to respond to the grid’s needs in as little as half a second or less, complete their change in output in under one second and maintain their response for many minutes or even hours.

Before the introduction of high volumes of wind and solar generation almost all generators (excluding nuclear) running on the system could provide frequency response. As these generators are increasingly replaced by intermittent technologies, the system operator must look for new services to maintain system stability.

An example is National Grid’s recent Enhanced Frequency Response tender, which asked for a solution that can deliver frequency stabilisation in under a second – 20 times faster than the Primary Response provided by existing thermal power stations. Drax was the only participating thermal power station, however all contracts were all won by battery storage projects.

Frequency future

Given the decline in fossil fuel generation and uncertainty around our power makeup in future decades, National Grid is consulting on how best to source services such as frequency response. The ideal scenario for National Grid is one where services can be increasingly sourced from reliable, flexible and affordable forms of low carbon generation or demand response.

The next generation of nuclear power stations, as with some already operating in France, can provide frequency response services. However the first of the new crop, Hinkley C, is around a decade away from being operational. Likewise, solar or wind coupled with battery, molten salt or flywheel storage will provide an increasing level of flexibility in the decades ahead as storage costs come down.

Thanks to power generation at Drax with compressed wood pellets, a form of sustainable biomass, Britain has already begun moving into an era where lower carbon frequency response can begin to form the foundation of a more reliable and cleaner system.

This story is part of a series on the lesser-known electricity markets within the areas of balancing services, system support services and ancillary services. Read more about black startsystem inertiareserve power and reactive power.  View a summary at The great balancing act: what it takes to keep the power grid stable and find out what lies ahead by reading Balancing for the renewable future and Maintaining electricity grid stability during rapid decarbonisation.

What is a working forest?

An illustration of a working forest

For centuries, civilizations have relied on forests and forest products. Forests provided fuel, food and construction materials, and there were plenty of them.

But when, in 18th century Europe, the needs of growing industrialisation sent development into overdrive, a problem arose: forests were struggling to meet demand.

In Germany, the problem was acute. The growing steel industry had increased demand for wood to power its smelters and for wood used in mining operations. Large areas of forestland were stripped to meet industry’s needs and overall supply was quickly decreasing.

No one was more acutely aware of the challenge than Hans Carl von Carlowitz, who at the time was the head of the Saxon mining administration.

So, in 1713 he published ‘Silvicultura Oeconomica’, a book which advocated the conservation and management of German forests so they could provide for industries in the long term. Although he drew on existing knowledge from around Europe, it was the first time an important term was used: Nachhaltigkeit, the German word for sustainability.

Carlowitz explained this new term: “Conservation and growing of wood is to be undertaken in order to have a continuing, stable and sustained use, as this is an indispensable cause, without which the country in its essence cannot remain.”

It was arguably the start of the scientific approach to forestry, and although our needs of forests have changed (as have the words we use to describe them – working forest, plantation forest and managed forest all refer to largely the same thing), that same principle is at the heart of how a modern working forest functions: to ensure what exists and is useful today will still be there tomorrow.

This approach relies on responsible forest management, which sets out a few key principles on how a forest should be managed to sustain its life.

Providing room to breathe

Working forests are commonly managed to produced sawlogs – high value wood that can be sawn to make timber for construction or furniture. For a forester to optimise the quality and quantity of sawlogs, regular thinning is required. Thinning is the process of periodically felling a proportion of the forest to aid its overall health and vigour. This means there are fewer trees fighting for the same resources (water, sunshine, soil). More than that, thinning can promote diversity by providing more light and space for other flora.

Thinning can occur several times in a forest’s cycle. It can be used to increase the size and quality of the remaining trees and also to encourage new seedlings to establish in place of the harvested trees when managing for continuous forest cover.

Nothing should be wasted

The roundwood produced by thinning is often too small to be sold as sawlogs, but that doesn’t mean it’s worthless. It can be sold to the pulp industry to make paper, or for particleboard or to the biomass industry to make compressed wood pellets, which can be used to fuel power generation – as is done at Drax Power Station. These industries also provide a market for the lower grade roundwood removed when the more mature trees are finally harvested.

In areas where there was no robust market for this low grade wood, it would often be left on site and become a fire risk or a haven for pest and disease attack. Too much low grade material left on site can also inhibit the regrowth of the next tree crop. So markets for this material are important for the health of the forest and the value of the land to the forest owner. Also in the Baltic countries markets for pulpwood are limited and the energy sector provides a valuable opportunity to clear the site for replanting and provide additional revenue to the forest owner.

This process of utilising all parts of the forest is essential for a healthy working forest. On the one hand, the revenue can cover the cost of thinning. This husbandry enhances the quality of the final tree crop and ensures that money is available to invest in future planting and regeneration, ensuring the forest area is consistently maintained and improved.

Red Pine, Pinus resinosa - thinned plantation with natural seedlings

Young regeneration in a shelterwood system, demonstrating the continuous forest lifecycle

The carbon benefits of a working forest

Rather than diminishing it, actively managing a forest helps its ability to sequester – or absorb and store – more carbon.

Carbon sequestration is directly related to the growth rate of a tree – a young, growing tree absorbs more carbon dioxide (CO2) from the atmosphere than an older one. Older trees will have more carbon stored (after a ‘childhood’ spent absorbing it), but if these are not harvested they are more susceptible to fire damage, pests and diseases and their carbon absorption plateaus.

In an actively managed forest, older trees ready for sawlog production can be harvested and replaced with vigorously growing young trees and in the process maximise the CO2 absorption potential of the forest.

The by-products of this process – the low grade wood and thinnings – can be used for the pulp and biomass industry, which both aids the health of the remaining forest, and provides revenue for the forester to invest in the long term life of his or her forest.

Three centuries of sustainability

In the 300 years since Carlowitz published his book on sustainability a lot has changed. And while it’s unlikely he foresaw forests providing fuel for renewable electricity and renewable heat, the approach remains as relevant.

What is a working forest? It is one that is as productive and healthy tomorrow as it is today. That we’re using the same resource today as we were 300 years ago is evidence to suggest it’s a practice that works.

Batteries as big as biomass domes?

Renewables are playing a bigger part of our electricity mix as the UK moves towards a low carbon economy. How we ‘plug the gaps’ left by intermittent renewables is among the greatest challenges faced by the energy sector.

Sources like wind and solar are intermittent – they can’t generate electricity all the time. When the sun doesn’t shine or the wind doesn’t blow they lack the fuel needed to generate power and can’t feed into the grid.

This leaves a gap in the UK’s electricity supply that needs to be filled. Today that’s done by sources like coal, gas and biomass which can be dialled up and down to accommodate for the dips and peaks in generation created by changes in demand and the weather.

One alternative being touted as a possible solution is storage and in particular, battery technology. However, creating batteries on a scale big enough to meet our incredible demand is a considerable challenge. It’s a challenge that will be met in a future where giant, affordable batteries are able to store solar power captured in the summer months for use in the winter. But costs would have to come down at an even faster rate than they have done in recent years.

The challenge of building bigger batteries

To demonstrate the size of this challenge, consider the biomass storage domes at Drax Power Station. These effectively operate as giant energy stores with the flexible ability to quickly feed renewable fuel to the power station, which generates electricity on demand.

Our biomass domes can hold 300,000 tonnes of sustainably-sourced compressed wood pellets, the equivalent of 600 GWh worth of electricity. Currently, batteries cost £350 per kWh, meaning at present prices it would cost £210 billion to replace the capacity of all four of our biomass domes using battery power.

Even if battery technology advances dramatically over the next few years that figure is only likely to fall to around £60 billion. Then there is the question of the ancillary services that thermal power stations provide. The batteries of the future may be able to provide these vital services (such as synthetic inertia, short-term reserve and reactive power), but for now, providing these via battery power is prohibitively expensive and in some cases best left to biomass and gas power stations.

We should not underestimate the challenges ahead. The UK’s ever-changing power system will need to balance more electricity generated via wind and solar with affordable solutions that are also reliable, flexible and lower carbon than coal. This is why Drax is developing four rapid-response gas power stations in addition to continuing its investment in biomass generation and supply.