based cogenerative plant. Fabio Armanasco*, Matteo Marzoli *, Luigi Colombo **, Giovanni Corbella*** * ** * In the last ten y generation. T kW power sy electric power suppl in co-generation s available is characterized by both to replace boilers and to satisfy In particular, traditional power sy In this paper an experi following, The co-generative plant installed at CESI RICERCA co The maxim and m The water circuit consists of two separable rings: • • Figure 1 shows a si To perform quantities: com dr (primary different operating conditions to sim In particular the following Fi

63° Congresso Nazionale ATI Palermo, 23-26 Settembre 2008 CESI RICERCA POLITECNICO DI MILANO, **UNIVERSITÀ DEGLI STUDI DI PAVIA ears energy technology has been more and more oriented to the so-called distributed his deals with small-scale power generation technologies (typically in the range of 3 to 1,000 ) located close to the end users to provide an alternative to or an enhancement of the traditional electric stem. It is generally accepted that centralized electric power plants will remain the major source of y for the future. Generated distribution, however, coupled with heat production, such as ystems, may further improve cost-effectiveness. On this subject, the lowest size currently an electrical power generation of about 30 kW: these systems are thus suitable the electrical energy demand of a building. co-generative plants based on micro-turbines may present total efficiency higher than that of a stem, in spite of its much lower electrical efficiency (usually less than 30%). mental characterization of a micro-co-generative plant will be presented. In the both a system description and the experimental protocols developed are summarized. S.p.A. is mainly composed of a micro-turbine, a gas mpressor, a dry cooler, a plate heat exchanger and a control panel. micro-turbine, a Turbec T100, can produce up to 167 kW heat power, 110 kW electrical power and a um temperature of the heated water of 130°C, depending of course on inlet conditions, as temperature ass flow rate. the plate heat exchanger line, which connects the micro-turbine with the district heating of CESI RICERCA S.p.A.; the dry cooler line, which allows the simulation of a variable heat load. mplified scheme of the plant. a complete energetic characterization, the system is equipped of suitable measurement instrumentation integrated in a PLC control system. In particular temperature, pressure and mass flow rates were acquired and monitored respectively in seven, three and two measurement sites by resistance thermometers PT100 (class A), piezo-resistive transducers (class 0.5% std) and electromagnetic flow meters (accuracy ±0.25%). The whole arrangement allows the real-time calculation of the following bustion heating power, electrical power, co-generative heating power, heat load at the air yer, electrical efficiency, thermal efficiency, first principle efficiency, second principle efficiency, PES energy saving index) and thermal limit. Moreover the control system enables the definition of ulate heat loads and study the consequent response of the micro-turbine. programs are available: gure 1. Scheme of the co-generative plant.

• program B (base or security program): it is an automatic procedure which ensures that the dry cooler dissipates all the heat power generated; • program A1: the electrical power produced and the water temperature at the outlet of the micro-turbine are set manually by an operator; all the heat is dissipated; • program A2: the heat load to be dissipated and the water temperature at the outlet of the micro-turbine are set manually by an operator: consequently, the micro-turbine is forced to regulate the electrical power to follow the required heat generation. We may distinguish the experimentation as follows: • tests to follow the electrical production, the aim of which is the energetic characterization of the plant; the results of this investigation, based on program A1, have been presented at the ASME-ATI Conference 2006. • tests to follow the thermal demand, oriented to simulate variable thermal load, based on program A2, which are the object of the present paper. Operative conditions were realized by varying the set-point temperature at the outlet of the micro-turbine in the range 60 – 90°C, with 5°C step. For each step, the heating power dissipated was varied in the range 70 – 170 kW, with 10 kW step. The variation of the thermal load was provided by the regulation of the three-way valve at the inlet of the air dryer. All the quantities listed above were evaluated: as an example, in Figure 2 the behavior of power that the absorbed by (in the order of so electrical set Bey ly test conditions in order to attain stationary variation of t 50 60 70 80 90 100 P el [kW ] A This work h Agree Energy 2007

40 70 80 90 100 110 120 130 140 150 160 170

the electrical power P el is reported as a function of the thermal load Q th for a water temperature at the micro-turbine outlet of 75°C. The curves are parameterized by the electrical set point, that is the maximum electrical micro-turbine can generate (notice that the effective power is lower, because 4.2 kW are the compressor and other auxiliaries). It can be noted that little variations of the electric power me kW) may result in large variations of thermal power (some tens kW), so that the point is maintained until the relative reduction of the rotation regime is lower than about 5%. ond this threshold, the micro-turbine is forced to reduce the electrical power generation within a range ing between the technical minimum (50 kW) and the electrical set point. The time needed to change the operation is estimated on average as 300 s for a 10 kW step he thermal load. Q th [kW] Pel-set point=60 kW Pel-set point=70 kW Pel-set point=80 kW Pel-set point=90 kW Pel-set point=100 kW Figure 2. Behavior of the electrical power production P el versus thermal load Q th at 75°C water temperature. cknowledgement as been financed by the Research Fund for the Italian Electrical System under the Contract ment between CESI RICERCA and the Ministry of Economic Development – General Directorate for and Mining Resources stipulated on June 21, 2007 in compliance with the Decree n. 73 of June 18, .