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Renewable energy sources – such as wind and solar power – are increasingly important low-carbon contributors to Europe’s energy supply and the fight against climate change. But as the use of renewable energy sources increases, their intermittency is becoming an issue.
The technology developed under CISTEM provides a solution by providing flexible generation of electricity and heat. When there is a shortage of renewable electricity, the fuel cell systems developed under CISTEM can balance the electricity grid by using the stored energy circulating in the gas grid. In the future, this could be decarbonised synthetic natural gas or even pure hydrogen.
Fuel cell systems have an additional benefit of generating by-product heat, which further improves the energy efficiency and reduces the energy bill for end users.
By enabling this distributed generation there is also the benefit of reduced transmission losses in the electricity grid with the appearance of “prosumers”. Distributed generation refers to a variety of technologies that generate electricity close to where it will be used, such as solar panels and combined heat and power. This means that instead of just consuming electricity from the grid customers can now also produce energy for the grid against payment.
The EU and industry-funded CISTEM project has advanced the technology by developing and testing a high-temperature proton exchange membrane fuel cell (HT-PEMFC) with improved performance and durability for use with combined heat and power (CHP) systems.
In doing so, the project team has overcome some of the key barriers to the commercialisation of HT-PEMFC technology which, compared to other similar solutions, can vary output quickly to meet demand.
Energy-efficiency levels are high, with more than 80 % of primary energy converted to electricity and heat. Although this might be comparable to commercial products such as CHP gas engines of this size, the HT-PEMFC offers a much higher electrical efficiency that can go up to 50-55 %. This is very beneficial to most consumers and other users as electricity is a high-value energy carrier that can be used in a lot more applications than heat.
The HT-PEMFC technology is operating at temperatures around 140-180 °C. This operation allows a much higher tolerance to fuel impurities which results in commercial advantages in terms of simplicity, size and cost. In addition, the system developed under CISTEM is modular which means it can be easily scaled up to larger sizes addressing other applications such as hospitals that could also use this high-temperature heat to sterilise equipment.
‘The CISTEM project has successfully demonstrated that primary energy savings and reduction of carbon dioxide emissions are possible,’ says project coordinator Peter Wagner of the German Aerospace Centre (DLR) Institute of Networked Energy Systems. ‘More than 80 % of the theoretically available energy from natural gas or hydrogen can be used directly by customers when installing a CISTEM CHP unit at their premises.’
Long-lasting components
CISTEM’s CHP unit is modular and can be scaled up to an output of 100 kilowatts, sufficient to supply electricity and heat to power multi-family residential buildings or small businesses. This ensures people can keep their homes and workplaces warm and the lights stay on even if the wind does not blow or the sun does not shine.
The project achieved very good results with its newly developed membranes that greatly improved the system’s life time. Previous proton-exchange membrane technology had an expected lifetime of 10 000 hours of operation. CISTEM’s membranes achieved 40 000 hours of operation, a fourfold improvement.
The CISTEM fuel cell also includes a processing system for converting natural gas into hydrogen which optimises the use of natural gas. A fully renewable scenario, in which the system uses hydrogen, is also an option in the longer term – for example, where hydrogen produced with renewable electricity is injected to and stored in the natural gas grid.
The project has also investigated operating strategies that allow CHP systems to be used in the most efficient way, in particular to avoid continuous shutdowns during the summer, when less heat and light is needed. As a result, CHP system suppliers are now well equipped to address customer demand for durable and energy-efficient products.
Preparing for market launch
Some of the components are already on the market, including the membrane electrode assemblies and bipolar plates – key components of a fuel cell – as well as the fuel processor. The stacks of fuel cells contained in the CHP unit are in the immediate pre-commercialisation phase, while the design and set-up of the system as a whole is undergoing preparation for market release.
CISTEM has borne further fruit in the shape of more than 30 scientific journal papers, a book chapter and some 15 scientific posters, as well as two Bachelor, ten Master, one diploma and two doctoral theses on the project.
‘By continuing our efforts and intensified close cooperation with industry, the market introduction of CISTEM CHP units will contribute to ensuring that already scarce fossil energy resources are used much more efficiently and help to reduce carbon dioxide emissions significantly,’ says Wagner.
CISTEM was funded through the Fuel Cells and Hydrogen Joint Undertaking, which pools EU and industry resources for research targeting commercial applications of the technology.