Dr Jacob Klimstra
In early February this year, I had the privilege of attending a celebration of one million successful running hours accumulated by four cogeneration units at a factory in Roermond, The Netherlands. It was a very pleasant event with a happy customer and a happy supplier.
The cogeneration units have been in operation since 1983, and I well remember all the efforts we took in those days to promote cogeneration. The monopolistic electricity companies initially tried to block the connection of local generators to the grid. They feared voltage and frequency instability, and were afraid that any generator not controlled by them would create safety issues. Fortunately, we could convince the authorities that increasing the number of generators on the grid would improve the security of supply as well as the frequency stability.
The big advantage of cogeneration, of course, was and is the substantial fuel savings compared with separate generation. Nowadays, grid connection for local generation is generally accepted. The factory in Roermond expects many years of successful operation to follow.
The four cogeneration units supply electricity and heat for a factory that processes an amazing 600,000 tonnes of recycled paper per year, turning it into useful products. The prime movers are modified aero-derivative gas turbines running at 14,250 rpm. According to the manufacturer, many people initially doubted that such light machines would really show high reliability and durability. Some engineers might have thought that a single large industrial unit would prove a better solution.
However, all doubts have been removed. The overhaul interval is only once every 45,000 hours. If needed in case of a calamity, a turbine can be exchanged in one day. The concept of having four units in parallel offers high supply reliability. At this factory, the match between electricity and steam production on the one hand and demand on the other is close to perfect. One unit is equipped with supplementary firing to create some extra flexibility in steam production. The factory has received a number of awards for its environmental friendliness.
A rough calculation reveals that, compared with separate generation, this cogeneration plant emits about 15 kilotonnes less CO2 per year. One might argue that 30 MW in wind turbine capacity can achieve the same reduction in CO2 emissions. However, the output from wind turbines is highly volatile, so the Roermond factory, with its steady energy demand, could never run on wind power alone. Yet the owners of wind turbines receive substantial subsidies, while the economy of the cogeneration plant currently suffers from artificially low electricity prices and artificially high gas prices. Soon we will have a discussion with the responsible ministry in The Netherlands about this unfair situation. Hopefully the talks will result in more favourable conditions for the country’s many cogeneration plants.
Notwithstanding the low financial benefits of cogeneration in the current climate, the management of the Roermond factory is investing in upgrading the installation’s control systems and counting on many more happy running hours. Being the energetic and environmental benchmark for the European paper industry is highly rewarding in itself, and is seen as a positive asset by customers. The cogeneration installation is a prime example of a reliable technology that can provide its services for many years.
Cogeneration is still one of the better options to save primary energy and to reduce greenhouse gas emissions.
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