Industry facilities have every interest in providing themselves with CHP units. However, an optimization of such units for industry applications is needed and represents an issue frequently addressed by research. Wang et al. [25] optimised the performance of different cogeneration plants to be employed in the cement industry, in order to recover exhaust heat. Monte et al. [26] analysed different paper industry production processes, proposing for each of them, technical solutions aimed at increasing the overall efficiency. Cogeneration systems are the most suitable approach, as also noted by Posch et al. [27], who analysed the Austrian case and ascertained that energy costs must be minimized as they are the main factor affecting energy management. Tamburini [28] et al. discussed the upgrading of a multiple effect distillation along with thermal vapour compression desalination plant, comparing steam plant-based solutions differing for the steam extraction pressure. They performed an evaluation based on the current European legislation and came at the conclusion that the amount of CHP electricity increases almost linearly with the number of supplied distillation units, however, they expressed the concern that the primary energy savings are strongly affected by the chosen referred efficiency values.

With regard to industry and cogeneration in Italy, an in-depth characterisation of industrial sectors, significant in CHP field, has been conducted, in order to define specific electrical and thermal consumptions of their production processes. Such a characterisation has been carried out by consulting the most trusted databases related to this field with reference to Italy only:

• Paper mills [29];

• Glass industry [30];

• within both the Italian and European context:

Actual data used to derive this characterization were acquired from Gestore dei Servizi Energetici (GSE), the state-owned company that promotes and supports RES in Italy. Finally, information owned by authors, deduced by activities previously conducted in different industrial sectors, was also reworked for this purpose.

Based on these data, the most interesting production processes have been identified, evaluating the specific energy consumption for each individual stage of the single process as well as for the whole production process.

With reference to the purpose of this paper, which is not going to look in detail at an individual industrial sector relevant for HEC purposes, but rather to provide energy and economic information on HEC applicable technologies, four classes of industrial processes have been defined, characterized by the same heat to electricity ratio (H/E). In each class, there are more industrial processes (Table 1), characterised by different specific thermal (C_s,H) and thus electric demand (C_s,E), therefore, these 10 categories are representative of different industrial sectors. Food sector is present in many categories because, in this field a great number of products, also very different from each other, can be made. Yarn, paper and pharmaceutical industries are the industrial sectors with the highest amount of heat demand.

In [10], [11], numerical assessments were performed in order to determine HEC performances of different power plant solutions. Such evaluations have been further examined in this paper and a summary of results elaborated for the evaluation of the installable power plants according to the particular industrial sector. The following technologies have been taken into consideration:

• Internal combustion engines (ICE): In a cogeneration setup, they are characterised by a power loss factor by heat extraction at a steam turbine (β) equal to 0 and efficiency of non-combined electrical/mechanical energy generation (η_non-CHP,E), equal to electric efficiency (η_E) [10], [11]. It seems important to remember that β must be calculated only for steam condensing extraction turbine-based plants, indeed it gives the electricity loss due to steam extraction for heat. In the simulations conducted in this study, a heat recovery from exhaust gases of the engine and water/oil circuit has been considered, heat is provided as steam, generated by hot fluids from ICE, at a variable temperature between 150 °C and 300 °C (heat from water/oil circuit is used for the first part of water economization). Main energy parameters (E_CHP/E, F/E and PES) have been deduced: such parameters refer to two power plant types, corresponding to small size power plants (SS, Small Size, around 1 MWe) and large size power plants (LS, Large Size, around 15 MWe), respectively. Numerical investigation has been conducted by varying H_CHP/E ratio, recovering progressively more heat from the exhaust gases of the engine, all the way to a minimum limit value established for gas temperature at heat recovery system outlet (about 90 °C);

• Gas turbines (GT): In a cogeneration setup, much like ICE’s, they are characterised by β = 0 and η_non-CHP,E = η_E. In the simulations, a plant configuration made up of a gas turbine and a Heat Recovery Steam Generator (HRSG), fed by exhaust gases from the gas turbine, has been considered, indeed heat is provided as steam at a variable temperature between 150 °C and 300 °C. Main energy parameters (E_CHP/E, F/E and PES) have been deduced: such parameters refer to two power plant types, corresponding to small size power plants (SS, Small Size, around 5 MWe) and large size power plants (LS, Large Size, around 30 MWe), respectively. Numerical investigation has been conducted by varying H_CHP/E ratio, recovering progressively more heat from exhaust gases, up to a minimum limit value established for gas temperature at heat recovery system outlet (about 90 °C);

• Steam Power Plants with Backpressure Turbine (SPP-BPT): In a cogeneration setup, much like ICE’s and GT’s, they are characterised by β = 0 and η_non-CHP,E = η_E. The herein simulated plant configuration is made up of a fossil fuel boiler (fed by natural gas), a steam turbine and a deaerator. Simulations have been conducted for turbine final pressures in the range from 5 to 40 bars in order to take into account the effects related to the different quality conditions (temperature, pressure) of the heat required by final users. Main energy parameters (E_CHP/E, F/E and PES) have been deduced: such parameters refer to power plant size not smaller than 5 MWe and this numerical investigation has been conducted by varying H_CHP/E ratio, that is varying turbine final pressures in the range from 5 to 40 bar;

• Steam Power Plants with Condensing Turbine (SPP-CT): they are characterised by β > 0 and η_nonCHP,E > η_E. Simulations have been conducted taking into account a plant configuration made of a fossil fuel boiler (fed by natural gas), a steam turbine, a condenser and a deaerator. Pressures are assumed in the range from 5 to 40 bars to include the effects related to the different quality conditions (temperature, pressure) of the heat required by final users. Main energy parameters (E_CHP/E, F/E and PES) have been deduced with reference to power plant size not smaller than 5 MWe. This numerical investigation has been conducted by varying H_CHP/E ratio, that is by varying, for each extraction pressure set, the extracted steam flow rate up to the maximum limit, that in turn is achieved for a mass flow rate at the condenser inlet, not less than 20% the design mass flow rate at the inlet of the turbine;

• Combined Cycle Power Plants (CCPP) with condensing turbine: In a cogeneration setup, they are characterised by β > 0 and η_nonCHP,E > η_E. A plant configuration made up of a gas turbine (similar to the gas turbine LS introduced above), a HRSG with two pressure levels, a steam section with condensing turbine and condenser has been herein taken into account. Simulations have been conducted for extraction pressures in the range from 5 to 40 bar so as to model the effects related to the different quality conditions (temperature, pressure) of the heat required by final users. Main energy parameters (E_CHP/E, F/E and PES) have been deduced: such parameters refer to power plant size not smaller than 50 MWe. Numerical investigations have been conducted by varying H_CHP/E ratio, that is by varying, for each extraction pressure set, the extracted steam flow rate until to the maximum limit, that, in turn, is achieved for a mass flow rate, at the condenser inlet, not less than 20% the design mass flow rate at the inlet of the steam turbine.

The above-illustrated characterisation of cogeneration technologies allowed for determination of the following parameters for each technology: H_CHP/E, F/E, E_CHP/E, and PES. As concerns the choice of such characteristic parameters, the following considerations must be taken into account:

• A range of values for the most significant energy parameters must be defined for each cogeneration technology, by categorising power plants according to their size (ICE and GT) and quality (temperature level) of the produced heat (SPP-BPT, SPP-CT, and CCPP). Such a subdivision derives from the fact that, for ICE’s and GT’s, the quality of heat demanded by users does not affect performance considerably, as they are more sensitive to plant size, instead, quality and quantity of heat produced by solutions employing steam cycles (SPP-BPT, SPP-CT, CCPP) affect their performance considerably;

• Since H_CHP/E ratio varies with cogeneration heat provided to final users, for all technological solutions considered here, a maximum value for H_CHP/E ratio has been chosen (Table 2), this is the case for ICE’s and GT’s, when providing heat involves exhaust gases to be discharged at temperatures in the range from 90 °C to 100 °C and, for ICE’s only, and a heat recovery from water/air/oil systems of about 70%. With respect to condensing steam turbine power plants (SPP-CT and CCPP), H_CHP/E value is correlated to the steam extraction from the turbine, it is possible to have the maximum value of H_CHP/E when a maximum value of steam is extracted, it happens when at least 20% of the mass flow rate entering the turbine passes in the condenser. In SPP-BPT, finally, H_CHP/E value depends only on the quality conditions (steam pressure, temperature) of the heat demanded by the production process; Table 2.

  Performance parameters of cogeneration technologies

  		(HCHP/E)max	F/E	FCHP/E	ECHP/E	PES [%]	Cpp [EUR/kW]	FO&M [%]
  ICE	Large size	0.87	2.2	2.2	1.0	23	650	8
  	Small size	1.1	2.5	2.5	1.0	20	1,200	8
  GT	Large size	1.5	2.8	2.8	1.0	22	800	6
  	Small size	1.9	3.4	3.4	1.0	15	1,300	6
  SPP-BPT	LT heat	3.8	5.4	5.4	1.0	12	1,600	4
  	HT heat	7.1	9.0	9.0	1.0	8	1,600	4
  SPP-CT	LT heat	2.5	4.6	4.2	0.86	5	1,800	4
  	HT heat	3.4	5.7	5.2	0.84	2	1,800	4
  CCPP	LT heat	0.60	2.2	1.7	0.78	20	1,000	4
  	HT heat	0.69	2.3	1.8	0.77	18	1,000	4

• F/E and E_CHP/E depend on the chosen H_CHP/E value;

• Concerning PES, for all power plant types, natural gas has been chosen as fuel. To ease into things, adjustments related to weather conditions and to electric grid connection tension values have not been taken into account.

On the basis of such considerations, Table 2 contains the summary of the CHP parameters characterising each cogeneration technology. These parameters are referred to the following power plants sizes: ICE P_e > 100 kW, GT P_e > 1,500 kW, SPP P_e > 3 MW and CCPP P_e > 20 MW.

In addition to these input values, the here-proposed method for power plant sizing requires a set of economic-environmental parameters to determine indicators such as Pay Back Period (PBP), Net Present Value (NPV) to total investment (I) ratio (NPV/I) and CO₂ emissions avoided (CO_2,a) in comparison to separate electricity and heat productions. Some of these input parameters are indicated in Table 2 and are referred, specifically, to costs. Given the difficulty in defining specific cost of a power plant (C_pp), in this paper such parameter has been derived from the specific cost per installed kW for the particular cogeneration technology, including a Balance of Plant (BOP) cost. As for operation and maintenance costs (C_O&M), they have been deduced as a percentage (F_O&M) of the power plant specific cost. All costs-related estimations are based on information available in the literature for the European [42], [43] and the US [44], [45] market, including also the particular Italian context as well as confidential information. The interest rate of invested capital has been assumed in a range 6-10%.

Concerning environmental performance, the specific CO₂ emission factor value has been assumed in accordance with the fuel type adopted (e.g., 55 ton_CO2 /TJ for natural gas).

Finally, in order to carry out economic evaluations, assumptions need to be made with regard to fuel and electricity costs. Such costs depend mainly on the size of industrial users, taxes, excise duties and so on. These parameters have been adopted, with reference to the Italian context regarding energy pricing and size of companies, as follows:

• Cost of electric energy drawn from the grid, 115-200 EUR/MWh [46];

• Cost of natural gas for cogeneration purposes: 28-60 EUR/MWh [46];

• Additional excise duty for natural gas when not utilised for cogeneration purposes: 5 EUR/MWh.

The selection and sizing method for CHP units to be installed in industrial sectors is based on results related to the investigations conducted in the previous sections. In particular, the characterisation of sectors, carried out in the previous paragraph, has enabled to calculate the specific electric and thermal consumption of the most important production processes. In this stage, in order to design the specific power plant, additional parameters are needed:

• Production: This information allows for the quantification of the energy demand (electricity and heat) of the analysed process, since the sectors considered in the study are numerous and small, medium and large companies can be found within the individual sectors, numerical investigations will be parameterised on the basis of production (i.e., small, medium and large production: 1,000, 50,000 and 400,000 ton/year respectively) [47], [48];

• Operating hours: An annual operating period equal to 7,000 hours has been assumed [47], [48];

• Characteristics of process heat: Steam or gases as thermal vector and medium-low temperature level.

The ratio P_t/P_e of the process ‒thermal to electric power ratio, (P_t/P_e)_process ‒can be calculated according to input data of the process (specific thermal and electric consumption, production and operating hours) as displayed in Figure 1a.

Figure 1.

Sizing method for cogeneration units integrated in industrial sectors

Next step is the application of the elaborated sizing criterion, which is founded on two fundamental hypotheses:

• Heat made available by the cogeneration unit has to be used at its most, in order to have a full harnessing of the maximum H_CHP/E ratio of the cogenerator, allowing for the achievement of the best HEC performances;

• Electricity has not to be exported to the national grid, therefore, the plant is designed according to an electric power equal at most to that required by the process.

Then the (P_t/P_e)_process ratio has to be compared to (P_t/P_e)_technology ratio of the specific cogeneration technology and, if the process ratio prevails:

it means that the chosen cogeneration technology will be capable of satisfying the electric demand of the process, but not the thermal demand, therefore, the cogeneration unit will be designed according to electric power of the process and auxiliary boilers will satisfy the additional thermal demand of the process.

However, if the result of the comparison is the following:

it means that the chosen cogeneration technology will be capable of satisfying completely the thermal demand of the process, but not the electric demand, therefore, the cogeneration unit will be designed according to thermal power of the process while additional electricity, to satisfy electric demand of the process, will be drawn from the national grid.

The implementation of the above-described criterion, as visible also in Figure 1b, allows the design of both the cogeneration unit [electric power, useful (cogeneration) thermal power and fuel thermal power] and auxiliary boilers (that is, the calculation of thermal power correlated to the production of heat in auxiliary systems) and enables the calculation of the electric power drawn from the grid. In order to quantify fuel thermal powers, the Italian reference efficiency values have been adopted (which are used in the calculation of a national HEC parameter, they are equal to 0.82/0.9 and represent average conventional efficiencies of typical Italian heat systems in the case of direct use of exhaust gases and in the case of steam/hot water production, respectively).

Once the sizing of cogeneration unit is finalized, CHP energetic performances, in terms of PES, can be assessed for the chosen technology.

Upon completion of the energy design of the cogeneration unit, the following step consists in the evaluation of economic-environmental parameters of the power plant, both in the absence and in the presence of the cogeneration unit. By means of the estimation of the annual cash flow, economic saving, PBP and the ratio of NPV to the investment (NPV/I) can be quantified.

Avoided CO₂ emissions can also be assessed evaluating both fuel emission factor and fuel thermal energies.

Table 3 displays main energy, economic and environmental results. This table is composed of 10 horizontal blocks, representing industrial process here analysed, each horizontal block is composed of three rows, each row represents a production (that is, size of the production process).

This table is then composed of five vertical blocks, representing cogeneration power plants herein analysed, each vertical block is composed of five column, each column represents respectively electric power and four cogeneration performance parameters.

Some cells of this table are green and they contain numbers, while other ones are white and they do not contain numbers. In this last case, it means that no integration is possible between industrial process and power plant for technological reasons.

In this paragraph, results can be analysed through horizontal blocks:

• Low-heat-requirement production sectors (H_CHP/E = 0.5);

• CHP-1 process: CHP-1 process cannot be coupled with any cogeneration technology if it is characterised by small production [lower than 1,000 ton/year)]. Indeed, in this case, maximum cogeneration plant size would be lower than 10 kWe. In the case of industrial processes with medium production (about 50,000 ton/year), cogeneration plant size is so small that only ICE’s are a suitable solution, in fact, they are the only technological solutions installable when the cogeneration plant sizes are about 150 kWe. In this case, performance parameters show a PES value of about 20%, a PBP of almost 3 years and an economic profitability equal to 0.8, the reduction in CO₂ emissions with respect to separate production is about 15%. Even in the case of industrial processes with large production (about 400,000 ton/year), cogeneration plant size (about 1.4 MWe) is so small that only ICE’s are a suitable solution. In this case, performance parameters are exactly equal to the previous ones.

• CHP-2 process: CHP-2 process cannot be coupled with any cogeneration technology if characterised by small production (lower than 1,000 ton/year). Indeed, in this case, maximum cogeneration plant size would be lower than 30 kWe.

  In the case of industrial processes with medium production (about 50,000 ton/year), cogeneration plant size is so small (1.4 MW) that only ICE’s are a suitable solution. In this case, the performance parameters show a PES value of about 20%, a PBP of almost 3 years and an economic profitability equal to 0.8, the reduction in CO₂ emissions with respect to separate production is about 15%.

  In the case of industrial processes with large production (about 400,000 ton/year), cogeneration plant sizes are so high that all cogeneration technologies analysed in this paper are possible suitable solutions. ICE’s and GT’s are characterised by sizes in the range 6-13 MWe, steam power plants (coupled with processes requiring heat at lower temperature) are characterised by electric power values between 3-5 MWe, CCPP’s (coupled with processes requiring heat at lower temperature) are characterised by electric power values of about 20 MWe. HEC performance parameters exhibit a PES value lower than the threshold value only for SPP-CT and higher (12-23%) for all the other technologies. Economic performance parameters show a PBP of barely more than 1 year for ICE’s (LS) and an interesting economic profitability for ICE’s and combined cycles (2.7), even though SPP-BPT have the greatest economic profitability (2.9). Environmental performance parameters show a substantial reduction in CO₂ emissions for ICE’s and combined cycles. It is clear that SPP-CT are a solution to be discarded (PES lower than the threshold value), ICE seems the preferable technological solution, but also CCPP’s are able to attain good performance, albeit with quite small power plant sizes.

All the above-discussed results are also displayed in Figures 2-5, in which it is possible to compare different technological solutions for the analysed industrial sectors. Obviously, with respect to Table 3, energetic, economic and environmental performance parameters are not graphically depicted for those sectors in which none or only one power plant solution is viable. The following paragraphs summarise the main conclusions for each class of production processes.

Figure 2.

Energy Performance (PES)

Figure 3.

Economic Performance (NPV/I)

Figure 4.

Economic Performance (PBP) [years]

Figure 5.

Environmental Performance (CO_2,a) [%]

Production processes with low heat requirement (H_CHP/E = 0.5), that is CHP-1 and CHP-2, cannot be integrated with any cogeneration power plants when production are low (lower than 1,000 ton/year). For the same industrial processes with medium and large production, cogeneration plants based on ICE represent a good solution, CCPP’s appear interesting only if industrial processes (CHP-2) are characterised by specific thermal consumption of about 200 kWh/ton and by production higher than 400,000 ton/year.

Production processes with medium heat requirement (H_CHP/E = 1.0), can be integrated with gas turbines and/or ICE’s when industrial processes are characterised by specific thermal consumption in the range 100-1,300 kWh/ton and by low/medium production (1,000-50,000 ton/year). All the analysed cogeneration technologies are suitable for industrial processes characterised by specific thermal consumption in the range 750-3,000 kWh/ton and by large production (400,000 ton/year): gas turbines turn out to be the best solution, while ICE’s, despite providing similar performances, do not seem particularly appropriate since the resulting plant size would require multiple engines instead of a single large unit (the resulting size is too big for a single unit), CCPP’s attain good performance, although slightly worse than GT’s.

Production processes with high heat requirement (H_CHP/E = 2.0), can be integrated with cogeneration plants based on GT’s and/or ICE’s when they characterised by small specific thermal consumption (100 kWh/ton) and by medium/large production (50,000-400,000 ton/year) or by higher specific thermal consumption (500-1,500 kWh/ton) and by small/medium production (1,000-50,000 ton/year). All the analysed cogeneration technologies are suitable for industrial processes characterised by specific thermal consumption in the range 500-1,500 kWh/ton and by large production (400,000 ton/year): GT’s and/or ICE’s (in a configuration with multiple engines instead of a single large unit) prove to be the best solutions, CCPP’s attain good performance only for production processes with high heat requirement (specific thermal consumption of 1,500 kWh/ton), although slightly worse than GT’s.

In this paragraph, results have been analysed by using vertical blocks revealing important observations. In fact, with respect to the individual technologies, the following considerations can be drawn:

• Almost all the analysed production processes can be coupled with ICE-based cogeneration plants, when this cogeneration plant type is not feasible, all the other ones are also not feasible, for high cogeneration plant sizes (higher than 50 MW), when matched to production processes with medium/high thermal demand and with large production, other cogeneration solutions could become more competitive (gas turbines or combines cycle power plants) even if they exhibit worse economic and environmental performances, as ICE’s must adopt a configuration with multiple engines;

• GT’s can be proposed in various applications, although to a lesser extent than those of ICE’s, and, in some cases, especially for plant sizes larger than 50 MW, they can provide economic performance parameters (PBP and NPV/I) higher than those attained by ICE’s;

• Technologies based on SPP-CT and backpressure turbine are feasible only in the case of industrial processes characterised by large production, SPP-CT never reach the threshold value for PES and are characterised by lower economic performance parameters than SPP-BPT, SPP-BPT appear to be competitive for industrial processes showing a very high heat demand and significant production;

• CCPP’s can be proposed only for those industrial processes characterised by large production and they generally exhibit economic performance parameters (PBP and NPV/I) higher than those provided by SPP-BPT, but lower than those of GT’s and ICE’s.

Concerning the individual parameters analysed, the following considerations can be drawn:

• PES: If excluding SPP-CT e, all analysed technologies display a PES value > 10% in the different fields of application. Of course, in the selection of the most appropriate technological solution for the application, it is important to take into account incentives granted for the operation in HEC regime. In Italy, such incentives are provided on the basis of a parameter comparable to PES (however, adopting reference efficiencies typical of the Italian context), therefore, a cogeneration plant solution displaying the maximum value for PES would be preferable. Among all the considered applications, ICE’s feature the highest PES values, CCPP’s are characterised by good values for PES, in some applications even higher than those of GT’s, SPP-CT never allow for an operation in HEC regime (obviously considering the natural gas as fuel);

• PBP: In several applications, ICE’s show the lowest values for PBP, immediately followed by GT’s, CCPP’s are characterised by good values for PBP, in certain applications even better than GT’s, steam power plants are characterised by higher values for PBP, especially in the condensing turbine configuration;

• NPV/I: GT’s are the top power plants only in a few sectors, in all of the other applications, all technologies appears to be nearly equivalent, with the exception of SPP-CT, small-sized ICE’s are characterised by quite low values for NPV/I parameter;

• Avoided CO₂ emissions: ICE’s are the most competitive power plants in almost all the analysed sectors, also GT’s and combined cycles involve substantial reductions in CO₂ emissions with respect to separate production, steam power plants, especially with condensing turbine, display the weakest environmental performances.

With respect to the individual analysed processes, in order to identify the technologies most suited to the specific application, TKPI has been defined for the herein-proposed cogeneration solutions, it is expressed through the relation indicated below:

and it can be calculated for each of the identified technological solution. It’s value cannot exceed 4 and the maximum values (minimum in the case of PBP), indicated in the formula above, refer to the maximum (minimum) value of each parameter, as can be inferred from Table 3. The total key performance indicators are shown in Figure 6 and the following considerations can be drawn according to processes requirements:

Figure 6.

Total key performance indicator

• Production processes with low heat requirement (H_CHP/E = 0.5) and small production, cannot be matched with any cogeneration plant, in all other cases, ICE’s, providing the best energy-related, economic and environmental performances, are the more suitable solution, even though CCPP’s could appear interesting for industrial processes characterised by specific thermal consumption of about 200 kWh/ton and by production larger than 400,000 ton/year;

• Production processes, with medium heat requirement (H_CHP/E = 1.0), specific thermal consumption in the range 100-1,300 kWh/ton and small/medium annual production, can be matched with cogeneration plants based on gas turbines and/or ICE’s. When specific thermal consumption is in the range 750-3,000 kWh/ton and production is large, all cogeneration technologies are feasible: gas turbines and CCPP’s appear to be the most beneficial solutions, ICE’s, even though their performances are similar to those of GT’s, could not be particularly appropriate, considering that the resulting plant size would involve the installation of multiple engines;

• Production processes, with high heat requirement (H_CHP/E = 2.0) and small/medium annual production, can be coupled with cogeneration plants based on GT’s and/or ICE’s, such solutions appear to be the only viable ones for industrial processes characterised by low specific thermal consumption (100 kWh/ton) and by large annual production. Industrial processes characterised by specific thermal consumption in the range 500-1,500 kWh/ton and by large annual production can be coupled with all cogeneration technologies: GT’s and/or ICE’s appear to be the most beneficial solutions, also CCPP’s can attain good performance when integrated in production processes with high demand for heat (specific thermal consumption of 1,500 kWh/ton);

• Production processes, with very high heat requirement (H_CHP/E = 3.0) and small/medium annual production, cannot be practically coupled with cogeneration plants, with the only exception of ICE’s in the case of medium production, these industrial processes, with large annual production, can be matched with all cogeneration technologies, except for CCPP’s: GT’s, ICE’s and SPP-BPT are the most appropriate solutions, SPP-CT could also be proposed, featuring, however, significantly worse energy, economic and environmental performances.