Tag: electricity generation

How to count carbon emissions

Iain Staffell, Imperial College London

31 August 2020

Opinion

Reduced demand, boosted renewables, and the near-total abandonment of coal pushed last quarter’s carbon emissions from electricity generation below 10 million tonnes.

Emissions are at their lowest in modern times, having fallen by three-quarters compared to the same period ten years ago.  The average carbon emissions fell to a new low of 153 grams per kWh of electricity consumed over the quarter.

The carbon intensity also plummeted to a new low of just 18 g/kWh in the middle of the Spring Bank Holiday.  Clear skies with a strong breeze meant wind and solar power dominated the generation mix.

Together, nuclear and renewables produced 90% of Britain’s electricity, leaving just 2.8 GW to come from fossil fuels.

The generation mix over the Spring Bank Holiday weekend, highlighting the mix on the Sunday afternoon with the lowest carbon intensity on record

National Grid and other grid-monitoring websites reported the carbon intensity as being 46 g/kWh at that time.  That was still a record low, but very different from the Electric Insights numbers.  So why the discrepancy?

These sites report the carbon intensity of electricity generation, as opposed to consumption.  Not all the electricity we consume is generated in Britain, and not all the electricity generated in Britain is consumed here.

Should the emissions from power stations in the Netherlands ‘count’ towards our carbon footprint, if they are generating power consumed in our homes?  Earth’s atmosphere would say yes, as unlike air pollutants which affect our cities, CO2 has the same effect on global warming regardless of where it is produced.

On that Bank Holiday afternoon, Britain was importing 2 GW of electricity from France and Belgium, which are mostly powered by low-carbon nuclear.  We were exporting three-quarters of this (1.5 GW) to the Netherlands and Ireland.  While they do have sizeable shares of renewables, they also rely on coal power.

Britain’s exports prevented more fossil fuels from being burnt, whereas the imports did not as they came predominantly from clean sources.  So, the average unit of electricity we were consuming at that point in time was cleaner than the proportion of it that was generated within our borders.  We estimate that 1190 tonnes of CO2 were produced here, 165 were emitted in producing our imports, and 730 avoided through our exports.

In the long-term it does not particularly matter which of these measures gets used, as the mix of imports and exports gets averaged out.  Over the whole quarter, carbon emissions would be 153g/kWh with our measure, or 151 g/kWh with production-based accounting.  But, it does matter on the hourly timescale, consumption based accounting swings more widely.

Imports and exports helped make the electricity we consume lower carbon on the 24th, but the very next day they increased our carbon intensity from 176 to 196 g/kWh.

When renewable output is high in Britain we typically export the excess to our neighbours as they are willing to pay more for it, and this helps to clean their power systems.  When renewables are low, Britain will import if power from Ireland and the continent is lower cost, but it may well be higher carbon.

Two measures for the carbon intensity of British electricity over the Bank Holiday weekend and surrounding days

This speaks to the wider question of decarbonising the whole economy.

Should we use production or consumption based accounting?  With production (by far the most common measure), the UK is doing very well, and overall emissions are down 32% so far this century.  With consumption-based accounting it’s a very different story, and they’re only down 13%*.

This is because we import more from abroad, everything from manufactured goods to food, to data when streaming music and films online.

Either option would allow us to claim we are zero carbon through accounting conventions.  On the one hand (production-based accounting), Britain could be producing 100% clean power, but relying on dirty imports to meet its entire demand – that should not be classed as zero carbon as it’s pushing the problem elsewhere.  On the other hand (consumption-based accounting), it would be possible to get to zero carbon emissions from electricity consumed even with unabated gas power stations running.  If we got to 96% low carbon (1300 MW of gas running), we would be down at 25 g/kWh.  Then if we imported fully from France and sent it to the Netherlands and Ireland, we’d get down to 0 g/kWh.

Regardless of how you measure carbon intensity, it is important to recognise that Britain’s electricity is cleaner than ever.

The hard task ahead is to make these times the norm rather than the exception, by continuing to expand renewable generation, preparing the grid for their integration, and introducing negative emissions technologies such as BECCS (bioenergy with carbon capture and storage).

Read full Report (PDF)   |  Read full Report   |   Read press release

Front cover of Drax Electric Insights Q2 2020 report

Electric Insights Q2 2020 report [click to view/download]

What are ancillary services?

21 August 2020

Power generation
Ancillary services

What are ancillary services?

Ancillary services are a set of processes that enable the transportation of electricity around the grid while keeping the power system operating in a stable, efficient and safe way.

Why do we need ancillary services? 

When electricity makes its way through the country, it needs to be managed so that the power generation and electricity useage levels are equal.

The regulating of elements such as frequency and voltage has to be carefully managed, so that the massive amounts of electricity moving – or transmitted – are able to be used safely in homes,  businesses, schools and hospitals around the country.

Ancillary services enable the power system to operate in a stable, efficient and safe way.

 What do ancillary services offer?

Ancillary services include a wide variety of electrical efficiency and safety nets, all focussed on ensuring the power system delivers enough output to meet demand yet remains stable:

Frequency: The UK’s power system runs at a frequency of 50 hertz – to stay balanced, it has to remain at that frequency. Turbines and generators adjust the speed at which they spin automatically to increase or decrease power in line with demand and ensure that the system is kept stable.

Voltage: Different parts of the UK’s transmission system use voltages of either 400, 275 or 132 kilovolts. To ensure that voltage remains within 5% of those figures at all times, to be safe for domestic electricity use, power stations can produce or re-absorb excess energy as reactive power, keeping the overall system reliable.

Inertia: Turbine use is important in keeping the system operating in its current state, even with disruptions and sudden changes. The electricity system uses the weight of heavy spinning turbines to create stability, acting as dampeners and smoothing out unexpected changes in frequency across the network.

Reserve: An important part of ancillary servicing is making sure that there are no surprises – so holding back powerto release if something unexpected happens means that the network can function confidently, knowing that there are generators and other power providers such as pumped hydro storage waiting ready to back it up.

Key facts about ancillary services

Who manages ancillary services?

In the UK the grid’s stability is managed by National Grid Electricity System Operator (ESO) – a  separate company of National Grid Electricity Transmission (ET). The ESO works with ancillary service providers to either sign long-term contracts or make short term requests for a service.

These partners are often power stations, such as Drax Power Station, which have large spinning turbines capable of controlling voltage, frequency, providing inertia and serving as a source of reserve power. 

What is the future of ancillary services, as we move to a more renewable system?

As the UK’s electricity system continues to change, so to do its requirements for different ancillary services. The switch from a few very large power stations to a greater variety of different electricity sources, some of which may be dependent on the weather, as well as changes in how the country uses electricity, means there is a greater need for ancillary services to keep the grid stable.

These services have historically been delivered by thermal power stations, but new innovations are enabling wind turbines to provide inertial response and overcome changes in frequency, and batteries to store reserve power that can then be supplied to the power system to ensure balance.

Ancillary Services

Ancillary services fast facts  

  • Batteries can in some cases be cheaper ancillary alternatives to conventional sources of energy. The Hornsdale Power Reserve, which runs on a Tesla battery in South Australia, lowered the price of frequency ancillary services by 90% after just four months of use.
  • Ancillary services usually work from habit; knowing when to slow electricity production, or increase supply based around the general public’s standard working hours, dinner time and the early morning rush.
  • But during the COVID-19 lockdown, electricity consumption on weekdays fell by 13% and so National Grid ESO had to intervene with ancillary services to keep the lights on.
  • Every year, the ESO’s ancillary services move 300 terawatt hours (TWh) of electricity, which is equal to 4 trillion kettles boiling at once.

With recent innovations around renewable energies, there are a wider variety of ways for ancillary services to generate power.

Go deeper

Button: What is decarbonisation?

Is renewable-rich the new oil-rich?

2 June 2020

Power generation
Aerial view of hundreds solar energy modules or panels rows along the dry lands at Atacama Desert, Chile. Huge Photovoltaic PV Plant in the middle of the desert from an aerial drone point of view

We’re all familiar with the phrase ‘oil-rich’ nations, but as low carbon energy sources become ever more important to meeting global demand, renewable energy could become a global export. With a future favouring zero-carbon and even negative emissions innovation, here are some countries that are not only harnessing their natural resources to make more renewable energy, but are making progress in storing and exporting it.

Could these new opportunities lead us to one day deem them ‘renewable-rich’?

Could Europe import its solar power supply?

With the largest concentrated solar farm in the world, Morocco is already streets ahead in its ability to capture and convert sunlight into power. The 3,000 hectare solar complex, known as Noor-Ouarzazate, has a capacity of 580 megawatts (MW), which provides enough power for a city twice the size of Marrakesh.

Noor-Ouarzazate Power Plant, Morocco. Image source: ACWA Power

Its uses curved mirrors to direct sunlight into a singular beam that creates enough heat to melt salt in a central tower. This stores the heat and – when needed – is used to create steam which spins a turbine and generates electricity. This has helped keep Morocco on course to achieve its goal of deriving 42% of its power from renewable sources by the end of 2020, which potentially means a surplus in the coming years.

Morocco already has 1.4 gigawatts (GW) of interconnection with Spain, and another 700 MW is scheduled to come online before 2026. The country’s close proximity to Europe could make its solar capacity a source of power across the continent.

Africa’s geothermal potential

Olkaria II geothermal power plant in Kenya

Kenya was the first African nation to embrace geothermal energy and has now been using it for decades. In 1985, Kenya’s geothermal generation produced 45 MW of power – 30 years later, the country now turns over 630 MW.

Kenya’s ample generation of geothermal electricity is due to an abundance of steam energy in the underground volcanic wells of Olkaria, in the Great Rift Valley. In 2015, the region was responsible for providing 47% of the country’s power.

Currently the Olkaria region is thought to have a potential capacity of 2 GW of power, which could help to provide a source of clean energy for Kenya’s neighbours. However, there is potential for the rest of East Africa to generate its own geothermal power.

In this region of the continent there is an estimated 20 GW of power generation capacity possible  from stored geothermal energy, while the demand for the creation of usable grids that can connect multiple countries is high. Kenya is currently expanding its own grid, installing a planned 3,600 miles of new electrical wiring across the country.

Winds of change

China’s position in the renewable energy market is already up top, with continuous investment in solar and hydro power giving it a renewable capacity of more than 700 GW

The country is also home to the world’s largest onshore wind farm, in the form of the Gansu Wind Farm Project, which is made up of over 7,000 turbines. It is set to have a capacity of 20 GW by the end of 2020, bringing the nationwide installed wind capacity to 250 GW.

With China exporting more than 20,000 gigawatt-hours (GWh) of electricity in 2018, large scale renewable projects can have a wide-reaching effect beyond its borders. South-Asia is the primary market, but excesses of power in Western China have stoked ideas of exporting power as far away as Germany.

Can the US store the world’s carbon?

In the quest for zero-carbon energy it won’t just be nations that can export excess energy that could stand to profit – those that can import emissions could also benefit.

While many countries are developing the capabilities to capture carbon dioxide (CO2), storing it safely and permanently is another question. Having underground facilities that can store CO2 creates an opportunity to import and sequester carbon as a service for other nations. Norway is already doing it, but the US has the greatest potential thanks to its abundance of large underground storage capabilities.

The Global CCS Institute highlights the US as the country most prepared to deploy carbon capture and storage (CCS) at scale, thanks to its vast landscape, history of injecting CO2 in enhanced oil recovery, and favourable government policies.

The Petra Nova plant in Texas is also known as the world’s largest carbon capture facility. The coal-power station captured more than 1 million tonnes of CO2 within the first 10 months of operating as a 654 MW unit.

Carbon capture facility at the Petra Nova coal-fired power plant, Texas, USA

Chile’s hydrogen innovation

Hydrogen is becoming increasingly relevant as an energy source thanks to its ability to generate electricity and power transport while releasing far fewer emissions than other fossil fuels.

Chile was an early proponent of energy sharing with its hydrogen programme. The country uses solar electricity generated in the Atacama Desert (which sees 3,000 hours of sunlight a year), to power hydrogen production in a process called electrolysis, which uses electricity to split water into oxygen and hydrogen.

Chile plans to export the gas to Japan and South Korea, but with global demand for hydrogen set to grow, higher-volume, further-reaching exporting of the country’s hydrogen could soon be on the way.

Going forward, these green innovations – from carbon storage to geothermal potential – could increasingly be shared between countries and continents in an attempt to lower the overall carbon footprint of the world’s energy. This could create a global power shift toward nations which, rather than having high capacity for fossil fuel extraction, can instead use a different set of natural resources to generate, store and export cleaner energy.

What is net zero?

21 January 2020

Carbon capture
Skyscraper vertical forest in Milan

For age-old rivals Glasgow and Edinburgh, the race to the top has taken a sharp turn downwards. Instead, they’re in a race to the bottom to earn the title of the first ‘net zero’ carbon city in the UK.

While they might be battling to be the first in the UK to reach net zero, they are far from the only cities with net zero in their sights. In the wake of the growing climate emergency, cities, companies and countries around the world have all announced their own ambitions for hitting ‘net zero’.

It has become a global focus based on necessity – for the world to hit the Paris Agreement targets and limit global temperature rise to under two degrees Celsius, it’s predicted the world must become net zero by 2070.

Yet despite its ubiquity, net zero is a term that’s not always fully understood. So, what does net zero actually mean?

Glasgow, Scotland. Host of COP26.

What does net zero mean?

‘Going net zero’ most often refers specifically to reaching net zero carbon emissions. But this doesn’t just mean cutting all emissions down to zero.

Instead, net zero describes a state where the greenhouse gas (GHG) emitted [*] and removed by a company, geographic area or facility is in balance.

In practice, this means that as well as making efforts to reduce its emissions, an entity must capture, absorb or offset an equal amount of carbon from the atmosphere to the amount it releases. The result is that the carbon it emits is the same as the amount it removes, so it does not increase carbon levels in the atmosphere. Its carbon contributions are effectively zero – or more specifically, net zero.

The Grantham Research Institute on Climate Change and the Environment likens the net zero target to running a bath – an ideal level of water can be achieved by either turning down the taps (the mechanism adding emissions) or draining some of the water from the bathtub (the thing removing of emissions from the atmosphere). If these two things are equally matched, the water level in the bath doesn’t change.

To reach net zero and drive a sustained effort to combat climate change, a similar overall balance between emissions produced and emissions removed from the atmosphere must be achieved.

But while the analogy of a bath might make it sound simple, actually reaching net zero at the scale necessary will take significant work across industries, countries and governments.

How to achieve net zero

The UK’s Committee on Climate Change (CCC) recommends that to reach net zero all industries must be widely decarbonised, heavy good vehicles must switch to low-carbon fuel sources, and a fifth of agricultural land must change to alternative uses that bolster emission reductions, such as biomass production.

However, given the nature of many of these industries (and others considered ‘hard-to-treat’, such as aviation and manufacturing), completely eliminating emissions is often difficult or even impossible. Instead, residual emissions must be counterbalanced by natural or engineered solutions.

Natural solutions can include afforestation (planting new forests) and reforestation (replanting trees in areas that were previous forestland), which use trees’ natural ability to absorb carbon from the atmosphere to offset emissions.

On the other hand, engineering solutions such as carbon capture usage and storage (CCUS) can capture and permanently store carbon from industry before it’s released into the atmosphere. It is estimated this technology can capture in excess of 90% of the carbon released by fossil fuels during power generation or industrial processes such as cement production.

Negative emissions essential to achieving net zero

Click to view/download graphic. Source: Zero Carbon Humber.

Bioenergy with carbon capture and storage (BECCS) could actually take this a step further and lead to a net removal of carbon emissions from the atmosphere, often referred to as negative emissions. BECCS combines the use of biomass as a fuel source with CCUS. When that biomass comes from trees grown in responsibly managed working forests that absorb carbon, it becomes a low carbon fuel. When this process is combined with CCUS and the carbon emissions are captured at point of the biomass’ use, the overall process removes more carbon than is released, creating ‘negative emissions’.

According to the Global CCS Institute, BECCS is quickly emerging as the best solution to decarbonise emission-heavy industries. A joint report by The Royal Academy of Engineering and Royal Society estimates that BECCS could help the UK to capture 50 million tonnes of carbon per year by 2050 – eliminating almost half of the emissions projected to remain in the economy.

The UK’s move to net zero

In June 2019, the UK became the first major global economy to pass a law to reduce all greenhouse gas emissions to net zero by 2050. It is one of a small group of countries, including France and Sweden, that have enacted this ambition into law, forcing the government to take action towards meeting net zero.

Electrical radiator

Although this is an ambitious target, the UK is making steady progress towards it. In 2018 the UK’s emissions were 44% below 1990 levels, while some of the most intensive industries are fast decarbonising – June 2019 saw the carbon content of electricity hit an all-time low, falling below 100 g/kWh for the first time. This is especially important as the shift to net zero will create a much greater demand for electricity as fossil fuel use in transport and home heating must be switched with power from the grid.

Hitting net zero will take more than just this consistent reduction in emissions, however. An increase in capture and removal technologies will also be required. On the whole, the CCC predict an estimated 75 to 175 million tonnes of carbon and equivalent emissions will need to be removed by CCUS solutions annually in 2050 to fully meet the UK’s net zero target.

This will need substantial financial backing. The CCC forecasts that, at present, a net zero target can be reached at an annual resource cost of up to 1-2% of GDP between now and 2050. However, there is still much debate about the role the global carbon markets need to play to facilitate a more cost-effective and efficient way for countries to work together through market mechanisms.

Industries across the UK are starting to take affirmative action to work towards the net zero target. In the energy sector, projects such as Drax Power Station’s carbon capture pilots are turning BECCS increasingly into a reality ready to be deployed at scale.

Along with these individual projects, reaching net zero also requires greater cooperation across the industrial sectors. The Zero Carbon Humber partnership between energy companies, industrial emitters and local organisations, for example, aims to deliver the UK’s first zero carbon industrial cluster in the Humber region by the mid-2020s.

Nonetheless, efforts from all sectors must be made to ensure that the UK stays on course to meet all its immediate and long-term emissions targets. And regardless of whether or not Edinburgh or Glasgow realise their net zero goals first, the competition demonstrates how important the idea of net zero has become and society’s drive for real change across the UK.

Drax has announced an ambition to become carbon negative by 2030 – removing more carbon from the atmosphere than produced in our operations, creating a negative carbon footprint. Track our progress at Towards Carbon Negative.

[*] In this article we’ve simplified our explanation of net zero. Carbon dioxide (CO2) is the most abundant greenhouse gas (GHG). It is also a long-lived GHG that creates warming that persists in the long term. Although the land and ocean absorb it, a significant proportion stays in the atmosphere for centuries or even millennia causing climate change. It is, therefore, the most important GHG to abate. Other long-lived GHGs include include nitrous oxide (N2O, lifetime of circa 120 years) and some F-Gasses (e.g. SF6 with a lifetime of circa 3,200 years). GHGs are often aggregated as carbon dioxide equivalent (abbreviated as CO2e or CO2eq) and it is this that net zero targets measure. In this article, ‘carbon’ is used for simplicity and as a proxy for ‘carbon dioxide’, ‘CO2‘, ‘GHGs’ or ‘CO2e’.

What is a fuel cell and how will they help power the future?

27 June 2019

Carbon capture
A model fuel cell car

NASA Museum, Houston, Texas

How do you get a drink in space? That was one of the challenges for NASA in the 1960s and 70s when its Gemini and Apollo programmes were first preparing to take humans into space.

The answer, it turned out, surprisingly lay in the electricity source of the capsules’ control modules. Primitive by today’s standard, these panels were powered by what are known as fuel cells, which combined hydrogen and oxygen to generate electricity. The by-product of this reaction is heat but also water – pure enough for astronauts to drink.

Fuel cells offered NASA a much better option than the clunky batteries and inefficient solar arrays of the 1960s, and today they still remain on the forefront of energy technology, presenting the opportunity to clean up roads, power buildings and even help to reduce and carbon dioxide (CO2) emissions from power stations.

Power through reaction

At its most basic, a fuel cell is a device that uses a fuel source to generate electricity through a series of chemical reactions.

All fuel cells consist of three segments, two catalytic electrodes – a negatively charged anode on one side and a positively charged cathode on the other, and an electrolyte separating them. In a simple fuel cell, hydrogen, the most abundant element in the universe, is pumped to one electrode and oxygen to the other. Two different reactions then occur at the interfaces between the segments which generates electricity and water.

What allows this reaction to generate electricity is the electrolyte, which selectively transports charged particles from one electrode to the other. These charged molecules link the two reactions at the cathode and anode together and allow the overall reaction to occur. When the chemicals fed into the cell react at the electrodes, it creates an electrical current that can be harnessed as a power source.

Many different kinds of chemicals can be used in a fuel cell, such as natural gas or propane instead of hydrogen. A fuel cell is usually named based on the electrolyte used. Different electrolytes selectively transport different molecules across. The catalysts at either side are specialised to ensure that the correct reactions can occur at a fast enough rate.

For the Apollo missions, for example, NASA used alkaline fuel cells with potassium hydroxide electrolytes, but other types such as phosphoric acids, molten carbonates, or even solid ceramic electrolytes also exist.

The by-products to come out of a fuel cell all depend on what goes into it, however, their ability to generate electricity while creating few emissions, means they could have a key role to play in decarbonisation.

Fuel cells as a battery alternative

Fuel cells, like batteries, can store potential energy (in the form of chemicals), and then quickly produce an electrical current when needed. Their key difference, however, is that while batteries will eventually run out of power and need to be recharged, fuel cells will continue to function and produce electricity so long as there is fuel being fed in.

One of the most promising uses for fuel cells as an alternative to batteries is in electric vehicles.

Rachel Grima, a Research and Innovation Engineer at Drax, explains:

“Because it’s so light, hydrogen has a lot of potential when it comes to larger vehicles, like trucks and boats. Whereas battery-powered trucks are more difficult to design because they’re so heavy.”

These vehicles can pull in oxygen from the surrounding air to react with the stored hydrogen, producing only heat and water vapour as waste products. Which – coupled with an expanding network of hydrogen fuelling stations around the UK, Europe and US – makes them a transport fuel with a potentially big future.

Fuel cells, in conjunction with electrolysers, can also operate as large-scale storage option. Electrolysers operate in reverse to fuel cells, using excess electricity from the grid to produce hydrogen from water and storing it until it’s needed. When there is demand for electricity, the hydrogen is released and electricity generation begins in the fuel cell.

A project on the islands of Orkney is using the excess electricity generated by local, community-owned wind turbines to power a electrolyser and store hydrogen, that can be transported to fuel cells around the archipelago.

Fuel cells’ ability to take chemicals and generate electricity is also leading to experiments at Drax for one of the most important areas in energy today: carbon capture.

Turning CO2 to power

Drax is already piloting bioenergy carbon capture and storage technologies, but fuel cells offer the unique ability to capture and use carbon while also adding another form of electricity generation to Drax Power Station.

“We’re looking at using a molten carbonate fuel cell that operates on natural gas, oxygen and CO2,” says Grima. “It’s basic chemistry that we can exploit to do carbon capture.”

The molten carbonate, a 600 degrees Celsius liquid made up of either lithium potassium or lithiumsodium carbonate sits in a ceramic matrix and functions as the electrolyte in the fuel cell. Natural gas and steam enter on one side and pass through a reformer that converts them into hydrogen and CO2.

On the other side, flue gas – the emissions (including biogenic CO2) which normally enter the atmosphere from Drax’s biomass units – is captured and fed into the cell alongside air from the atmosphere. The CO2and oxygen (O2) pass over the electrode where they form carbonate (CO32-) which is transported across the electrolyte to then react with the hydrogen (H2), creating an electrical charge.

“It’s like combining an open cycle gas turbine (OCGT) with carbon capture,” says Grima. “It has the electrical efficiency of an OCGT. But the difference is it captures CO2 from our biomass units as well as its own CO2.”

Along with capturing and using CO2, the fuel cell also reduces nitrogen oxides (NOx) emissions from the flue gas, some of which are destroyed when the O2and CO2 react at the electrode.

From the side of the cell where flue gas enters a CO2-depleted gas is released. On the other side of the cell the by-products are water and CO2.

During a government-supported front end engineering and design (FEED) study starting this spring, this CO2 will also be captured, then fed through a pipeline running from Drax Power Station into the greenhouse of a nearby salad grower. Here it will act to accelerate the growth of tomatoes.

The partnership between Drax, FuelCell Energy, P3P Partners and the Department of Business, Energy and Industrial Strategy could provide an additional opportunity for the UK’s biggest renewable power generator to deploy bioenergy carbon capture usage and storage (BECCUS) at scale in the mid 2020s.

From powering space ships in the 70s to offering greenhouse-gas free transport, fuel cells continue to advance. As low-carbon electricity sources become more important they’re set to play a bigger role yet.

Learn more about carbon capture, usage and storage in our series: