Putting thermal energy storage on the rocks
Methods of generating renewable energy are becoming more productive. Whether it’s a more efficient solar cell or a larger rotor blade, developers are continually coming up with more efficient methods of harnessing natural resources. While many companies are devoting their efforts to refining existing technologies, there is an issue with renewables which has yet to be definitively resolved: energy storage. That is, how do we store the excess energy generated by renewable resources?
The storage situation
One of the advantages of utilising oil or gas in energy generation is that they are ‘on-demand’ energy sources. When a driver wants to make a trip in his vehicle, he can be sure it will start if there is fuel in the tank. Oil also boasts a high energy density, meaning that a relatively small amount of refined crude oil can produce a comparatively large quantity of energy. However, as the world seeks to decarbonise, it must also develop equally dispatchable methods of powering our way of life.
Lithium ion batteries — with their impressive energy density and long lifetimes — have been touted as the favoured method for combatting the intermittency of renewables, especially solar. Tesla famously utilises the batteries in its home-use Powerwall and utility-scale Powerpack energy storage solutions. The lifetime of these batteries, and equivalent products manufactured by Panasonic, are reportedly limited to roughly 500 ‘deep cycles’. This is the measure of the number of times a battery can deplete from full charge to 20 percent power before its performance deteriorates.
While lithium ion batteries might be suitable for use in smartphones with an anticipated life of two years, they may not be the large-scale storage ‘silver bullet’ that the renewable industry is seeking. This doesn’t mean that battery solutions should be abandoned altogether, but companies in the sector are already trialling new and innovative ways of capturing energy for later use.
The Siemens solution
In October of this year, Germany’s Siemens, the largest engineering firm in Europe, debuted a thermal storage concept for wind power which promises low costs and reliability. The company has partnered with Technical University Hamburg Harburg (TUHH) and utility Hamburg Energie to test the viability of what the company calls its Future Energy Solution (FES). The system will reportedly deliver energy at below US $111 per megawatt hour.
The technology combines existing steam turbine technology with packed-bed heat storage. The system works by utilising excess wind energy to power an industrial-scale heater which then blows air heated to 600 degrees celsius across a bed of rocks inside an insulated container. When power is required, the heat stored in the rocks provides steam to a conventional turbine capable of funneling electricity to the grid. The system is being designed to work with wind energy, but could theoretically accommodate other forms of renewable generation, too.
With the help of scientists for the TUHH Institute for Thermofluid Dynamics, Siemens is currently researching how to make the process of charging and discharging the FES more efficient. The firm and its venture partners are assembling at 25-cubic-metre model of the storage tank in Hamburg’s Bergedorf borough. As it stands, the mock-up environment only tests the thermal requirements for the storage process with no reverse current generated. Researchers are planning to test the system’s energy conversion potential in spring of next year. According to a statement issued in late September, the company is also constructing a full-size FES capable of storing some 36 megawatt hours of energy in a container with 2,000 cubic metres of rock. Siemens predicts that the solution will generate up to 1.5 megawatts (MW) of electricity for up to 24 hours a day.
"The technology of our FES store deliberately uses mainly tried and trusted technology," said Till Barmeier, Siemens' Project Manager in a statement. "Because we are working here with tested thermal components and a series-ready steam turbine, we will be able to offer a practical solution within a few years. Our complete experimental system will be operational in just around 15 months."
Barmier has said that Siemens is going to develop a commercial pilot project of between 30 and 40MW in 2019. It is in the process of identifying potential customers. Further down the line, the firm anticipates that the FES would have a capacity that could exceed 100 megawatts and be able to store 48 hours’ worth of energy for up to seven days.
No single answer
Just as no single form of renewable energy generation will be capable of meeting all demand, no storage solution will universally house excess energy. It’s likely that a mix of technologies — from solid-state batteries to pumped hydropower — will act as storage facilities. Siemens’ FES admittedly breaks new ground in terms of cost and efficiency, but it will be one of many available options for capturing energy to be dispatched as-needed.
Read the January 2017 issue of Energy Digital magazine
UK must stop blundering into high carbon choices warns CCC
The UK Government must end a year of climate contradictions and stop blundering on high carbon choices, according to the Climate Change Committee as it released 200 policy recommendations in a progress to Parliament update.
While the rigour of the Climate Change Act helped bring COP26 to the UK, it is not enough for Ministers to point to the Glasgow summit and hope that this will carry the day with the public, the Committee warns. Leadership is required, detail on the steps the UK will take in the coming years, clarity on tax changes and public spending commitments, as well as active engagement with people and businesses across the country.
"It it is hard to discern any comprehensive strategy in the climate plans we have seen in the last 12 months. There are gaps and ambiguities. Climate resilience remains a second-order issue, if it is considered at all. We continue to blunder into high-carbon choices. Our Planning system and other fundamental structures have not been recast to meet our legal and international climate commitments," the update states. "Our message to Government is simple: act quickly – be bold and decisive."
The UK’s record to date is strong in parts, but it has fallen behind on adapting to the changing climate and not yet provided a coherent plan to reduce emissions in the critical decade ahead, according to the Committee.
- Statutory framework for climate The UK has a strong climate framework under the Climate Change Act (2008), with legally-binding emissions targets, a process to integrate climate risks into policy, and a central role for independent evidence-based advice and monitoring. This model has inspired similarclimate legislation across the world.
- Emissions targets The UK has adopted ambitious territorial emissions targets aligned to the Paris Agreement: the Sixth Carbon Budget requires an emissions reduction of 63% from 2019 to 2035, on the way to Net Zero by 2050. These are comprehensive targets covering all greenhouse gases and all sectors, including international aviation and shipping.
- Emissions reduction The UK has a leading record in reducing its own emissions: down by 40% from 1990 to 2019, the largest reduction in the G20, while growing the economy (GDP increased by 78% from 1990 to 2019). The rate of reductions since 2012 (of around 20 MtCO2e annually) is comparable to that needed in the future.
- Climate Risk and Adaptation The UK has undertaken three comprehensive assessments of the climate risks it faces, and the Government has published plans for adapting to those risks. There have been some actions in response, notably in tackling flooding and water scarcity, but overall progress in planning and delivering adaptation is not keeping up with increasing risk. The UK is less prepared for the changing climate now than it was when the previous risk assessment was published five years ago.
- Climate finance The UK has been a strong contributor to international climate finance, having recently doubled its commitment to £11.6 billion in aggregate over 2021/22 to 2025/26. This spend is split between support for cutting emissions and support for adaptation, which is important given significant underfunding of adaptation globally. However, recent cuts to the UK’s overseas aid are undermining these commitments.
In a separate comment, it said the Prime Minister’s Ten-Point Plan was an important statement of ambition, but it has yet to be backed with firm policies.
Baroness Brown, Chair of the Adaptation Committee said: “The UK is leading in diagnosis but lagging in policy and action. This cannot be put off further. We cannot deliver Net Zero without serious action on adaptation. We need action now, followed by a National Adaptation Programme that must be more ambitious; more comprehensive; and better focussed on implementation than its predecessors, to improve national resilience to climate change.”
Priority recommendations for 2021 include setting out capacity and usage requirements for Energy from Waste consistent with plans to improve recycling and waste prevention, and issue guidance to align local authority waste contracts and planning policy to these targets; develop (with DIT) the option of applying either border carbon tariffs or minimum standards to imports of selected embedded-emission-intense industrial and agricultural products and fuels; and implement a public engagement programme about national adaptation objectives, acceptable levels of risk, desired resilience standards, how to address inequalities, and responsibilities across society.
Drax Group CEO Will Gardiner said the report is another reminder that if the UK is to meet its ambitious climate targets there is an urgent need to scale up bioenergy with carbon capture and storage (BECCS).
"As the world’s leading generator and supplier of sustainable bioenergy there is no better place to deliver BECCS at scale than at Drax in the UK. We are ready to invest in and deliver this world-leading green technology, which would support clean growth in the north of England, create tens of thousands of jobs and put the UK at the forefront of combatting climate change."
Drax Group is kickstarting the planning process to build a new underground pumped hydro storage power station – more than doubling the electricity generating capacity at its iconic Cruachan facility in Scotland. The 600MW power station will be located inside Ben Cruachan – Argyll’s highest mountain – and increase the site’s total capacity to 1.04GW (click here).
Lockdown measures led to a record decrease in UK emissions in 2020 of 13% from the previous year. The largest falls were in aviation (-60%), shipping (-24%) and surface transport (-18%). While some of this change could persist (e.g. business travellers accounted for 15-25% of UK air passengers before the pandemic), much is already rebounding with HGV and van travel back to pre-pandemic levels, while car use, which at one point was down by two-thirds, only 20% below pre-pandemic levels.