Cogeneration and turbogas, waiting for hydrogen


Cogeneration remains the best technology for paper mills, even while waiting for a more widespread use of new renewable sources. Digital technology is the perfect ally of energy use optimisation, as it helps balance it all at a time when energy costs are fluctuating.

Industry and energy are inseparable; there is no industrial production without energy management and consumption. Never has this combination been so clear as in the current historical moment. The energy crisis in which European industry is mired accelerates the need to implement the energy mix that has been talked about for years.

Technology is also preparing itself, and in some cases is already ready for new energy sources.

Towards a new energy

The European policy is putting in place substantial and ambitious recovery plans. These include working on the recovery of the EU economy, which was severely tested by the Covid-19 pandemic, but also tackling the serious problem of spiralling price rises, which have been further exacerbated by the Ukrainian-Russian conflict.

At the same time, there is a push for an environmentally sustainable energy policy. Europe is relying heavily, for example, on the use of hydrogen, biogas and CO2 capture technologies. Of the approximately 1.8 trillion EUR earmarked for the Multiannual Financial Framework (2021-2027) and the Next Generation EU, more than 20% is earmarked for these forms of energy, while around 8% will be invested in boosting digitisation.

These figures were provided by Paolo Masiero, manager market development at Solar Turbines, who spoke at Miac 2021 about cogeneration and the role of the new turbogas technology.

An example calculation in various scenarios

The use of cogeneration – a technology that is already widely used in the paper industry – in a normal economic period is the best solution for securing the enormous energy requirements of the paper production cycle.

But it is even more so in a period when energy costs are rising. Masiero compared two different economic conditions, one relating to the second half of 2020 – before the start of the price hike – and one relating to the same period the following year.

«Assuming a cogeneration in Italy based on a Taurus 70 (8MW), serving a production of 73 thousand tons per year of tissue paper and operating in a direct drying configuration, in a context similar to that of the last quarter of 2020 with the cost of natural gas at 0.28 EUR/Sm3 and electricity at 94 EUR/MWh, we have calculated a saving of 3.7 million EUR projected on an annual basis. We then measured how the primary saving in terms of cash flow varies as the energy mix changes. Subtracting a CO2 cost of 65 EUR/ton from the 3.7 million EUR, the operational saving compared to an identical situation without a CHP plant would be more than 1 million EUR. If we add the energy efficiency certificates (EEC) guaranteed by the machine taken as an example, which would be around 2 million EUR per year, the benefit would be around 3 million EUR per year.

Considering the costs for the same period in 2021 – which are constantly rising – the calculations show that the use of cogeneration continues to be profitable. «With the price of electricity rising from 94 to 220 EUR/MWh and gas to 1.46 EUR/Sm3, the saving from a cogeneration plant rises to around 6.7 million EUR. If we subtract from this the cost of CO2, which has risen to almost 100 EUR/MWh, i.e. 4 million EUR, and consider the contribution of EEC, the operating saving would be around 4.5 million EUR, but in this scenario the counterbalance to the saving would be the overall operating costs, which are difficult to sustain».

Despite the changes in energy costs in the meantime and the unknowns that cannot be taken into account, when all is said and done, for energy-intensive industries such as paper mills, cogeneration is still the best solution. What Masiero has done, explains the manager, is just an exercise, a sensitivity analysis – moreover made before energy costs increased to the point of becoming prohibitive – therefore with all its inevitable shortcomings, but able to demonstrate how valuable cogeneration is for the paper industry even in difficult scenarios. «A cogeneration plant, in the paper sector, is absolutely still the most robust and flexible system for reducing operating costs,» he says, «even in energy contexts with significant fluctuations such as those we are experiencing».

The hydrogen project

However, it is also necessary to prepare for a new technological scenario, aimed at energy saving and decarbonisation, in which sources such as hydrogen will become increasingly predominant. This is what Solar Turbines has been doing for some years now.«As of today, our machines,» continues Masiero, «are ready to operate with mixtures of green hydrogen up to 20% volumetric,» which is the percentage expected in the gas mix that will circulate in pipelines in the near future and which, at the moment, is below that percentage.

«Our technology development roadmap, depending on the availability of hydrogen at network and distribution level, envisages machines capable of burning 100% hydrogen by 2030 without the need for water injection catalysts to reduce NOx emissions».

With regard to CO2, the Caterpillar group, of which Solar Turbines is a member, completed in 2021 the acquisition of a company that has developed a turbine fume recirculation technology capable of increasing the carbon dioxide concentration of flue gases. This makes it possible to install smaller and much more efficient CO2 abatement systems, CCUS.

Doing more with less through digital solutions

Another key element of Solar’s projects concerns energy optimisation, what Masiero defines very effectively as «doing more with less» and which, more than ever, has become an essential strategy for companies.

«We have focused on three objectives: to improve the operational part of the machine, but linked to the production system, so it is no longer considered as a stand-alone technology but as part of its context; to make profitability sustainable; and to utilise the benefits of plant flexibility».

Here is the example of a company in the pharmaceutical chemical sector that was a customer of Solar Turbines. The company was characterised by the discontinuous operation of the machines during the week, due to frequent changes in production, and production stops at the weekend, while keeping the power plant in continuous operation. Although the company was able to manage the plant very well, so much so that, despite the highly irregular trend, it had a thermal efficiency of around 82%, the need was to optimise its operation. The choice was therefore to digitalise the system.

First of all, «we added more tools and made the power plant and turbine communicate with the company’s production ERP (Enterprise Resource Planning) system. At the same time, we put the system in communication with the external environment, i.e. with the network and all the request signals coming from it. This allowed us to optimise the flows and understand how to manage them. The effect was, first of all, a reduction in the operating hours of the staff responsible for running the plant, freeing up manpower and reducing the direct costs allocated to the plant. Secondly, we were able to increase the plant’s hours of availability, according to real needs, while at the same time reducing scheduled and unscheduled downtimes, determining the most appropriate times to interrupt production».

Even more interesting, however, was the implementation of the system’s ability to manage the plant’s performance. The system «no longer just records whether the turbine is on or off, how much it is producing compared to what is required, but shows the real-time costs of how much is being produced with a given piece of equipment, how much electricity costs at a given time compared to the price of the same on the grid and its fluctuations. Basically, it allows the system to communicate with the outside world and to make the system decide on “make or buy” options, i.e. whether and when it is more convenient to use the energy produced internally or to sell it on the grid as excess».

The effect of decarbonisation

The same implementation concerned the management of carbon dioxide, «again we have parametrized the CO2emissions of the thermal power plant system with the country’s emissions and the cost of CO2 at a given time». These complex parameters have enabled the company to manage the power station, further optimising its production set-up.

This digitalised management «allowed, especially when the average price of electricity rose suddenly, to better support the company in managing grid exports with appropriate contracts, going from 1,800 MWh/year to 3,500 MWh/year that could be exported directly to the national grid. The result has been a significant increase in direct cash flows on the management of the power plant».

When all is said and done, the chemical-pharmaceutical company, which already had an optimised power plant capable of operating at 82% efficiency before Solar Turbines’ intervention, has seen a marginal increase in benefits of around 200,000 EUR per year, «a figure capable of providing an acceptable payback on the digitisation system,» comments Masiero. And that’s not all, because «the most interesting fact is that, by allowing the turbine to operate at the points of optimal energy than could previously be done with manual management of the system, there has been a reduction in CO2 emissions of around 1.5%».

The use of digital systems therefore offers a number of advantages, plus a final one that benefits the resilience of the entire electricity grid. In the Italian and European electricity market, the possibility of participating in dispatching services is emerging, which can be very interesting for companies. «Renewable energies are increasingly present in the grid and the time mix of these sources compared to fossil fuels has more weight,» says the manager. The problem with renewable energies, however, is that they are unpredictable and cannot be planned for. This is where the role of cogeneration comes into play. «A smart cogeneration plant, i.e. one that is intelligently connected to an external environment, can indirectly support the penetration of renewables – and consequently decarbonisation – as it makes up for the lack of energy when these sources are not active».