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Due to the increasing use of intermittent renewable generation, the power grid requires more flexible resources to balance supply and demand of electricity. Steam systems with turbine-generators, which are widely used in industries, can be operated flexibly to support the power grid. Yet, the available amount of flexibility of industrial steam systems is still not clearly quantified. This study presents the method to quantify electricity generation flexibility of a typical industrial steam system with a steam turbine-generator and process heat demands. The proposed method is introduced based on a real case of an integrated pulp and paper mill in Austria. An integrated mathematical model representing the combined electricity and steam system is developed to simulate the behaviour of the on-site energy system to quantify the potential flexibility provision. Flexibility is represented as the maximum upward and downward changes in the imported electricity from the public power grid. The results demonstrate that it is possible to aggregate the flexibility of the industrial facility as a lookup table. Also, the results reflect key factors that limit the flexibility at different operating points of the turbine-generator.

Industrial multi-energty-systemslike paper mills can provide flexibility services to existing ancillary servicemarkets or to the intra-day market. The paper presents a precise model of the CHP andsteam system of a paper mill. By means of this model the possible flexibility provision of theMES depending on the state of operation could be quantified as operational boundaries forupward and downward regulations. The result show that the steam system has more capacitiesfor downward regulations than upward regulations, which indicates different capabilities inproviding services like aFRR and mFRR to the market. In the next step the improvement of thesteam system by the installation of a steam accumulator will be investigated in terms of steam losses, network cost savings, and additional flexibility provision. While the technologies of steam systems and steam accumulators seem to be well proven,some tariffs for system utilisation and renewables contribution might yet be improved to bettersupport the participation of industrial (net) consumers of electricity in markets for electricalflexibility.In particular, provision of negative balancing energy will result in an increase of consumption and may cause additional consumption peaks. The operator of the industrial facility will becharged for additional peak consumption on monthly basis according to the Austrian Electricity SystemCharges Ordinance Section 5. Section 5 (9) regulates the system utilisation charge forbalancing service providers at a fairly reduced rate. Unfortunately, this reduced rate is only available for balancing service provision but does not apply for any schedules related to dayahaed or intraday markets. &nbsp