Energy generation: fossil and renewable energy sources

Generation and the Group plants

Acea Produzione, whose share capital is wholly-owned by Acea SpA, manages a series of electricity generation plants:

  • two thermoelectric plants located in the municipal area of Rome; Montemartini (around 80 MW) and Tor Di Valle (around 145 MW), and  
  • 7 hydroelectric plants located in Lazio and Abruzzo (around 120 MW), 

 for around 345 MWe in total of installed power available. 

The traditional generation base is flanked by two waste-to-energy plants located respectively in San Vittore del Lazio and Terni, for total power of 25 MW, destined to double in the next few months, once the revamping work underway has finished. In conclusion, around 46 MW of photovoltaic plants should be considered, installed in central/southern Italy, a significant portion of which (32.5 MW) had however been sold off to RTR Capital, a subsidiary of Terra Firma, towards the end of the year.

Total electricity production in 2012 came to around 652 GWh (544 GWh in 2011). The considerable rise was essentially due to the Salisano plant becoming fully up and running (12 months), after a shutdown for revamping which lasted for most of 2011 and the regular functioning of both the new lines of the waste-to-energy plant at San Vittore del Lazio (+ 46%).

With respect to 2010 and previous years, thermoelectric production of the Tor di Valle plant was almost cancelled out (10.34 GWh produced in the year compared with 176.3 GWh in 2010), essentially consequent to the trend in market prices unfavourable for this type of plant (see Environmental accounts).

 

 The portion generated from renewable sources, with around 530 GWh, was clearly predominant (over 81% of the total), with a contribution of 361 GWh from hydroelectric, 109 GWh from waste-to-energy and 60 GWh from photovoltaic (table No. 74).

Generation from waste-to-energy activities, equating to 218 GWh, although up sharply with respect to the previous year (+ 46%), is still lower than potential, due to both expected revamping of the first line of the San Vittore del Lazio plant, currently underway, and the continuation of the shutdown of the Terni plant, where at the end of 2012 revamping work commenced two years ago concluded.

Around half the 2012 generation from waste-to-energy is considered renewable since it is associated with the combustion of the biodegradable fraction of SUW, in fact equal to 50% of the total.

In conclusion, heat generation and distribution should be recalled: at the Tor di Valle thermoelectric plant, thermal energy was generated for around 88 GWh, used to serve the customer base of around 34,000 inhabitants in the south of Rome (Mostacciano, Torrino, Mezzo Cammino)97 by means of a dedicated district heating network.

Table No. 74- Energy produced, broken down by primary energy source (2010-2012)

TJ (GWh)(*)

primary energy source 2010 2011
2012
diesel (gas oil) 10.116
(2.81)
16.8
(4.7) 
7.0
(1.9)
natural gas (combined cycles and co-generation) 634.7
(176.3)
63.9
(17.8)
37.2
(10.3)
waste-to-energy (50% of total) 226.1
(62.8)
268.9
(74.7)
392.9
(109.1)
total thermoelectric 870.9
(241.9)
349.6
(97.1)
437.3
(121.5)
hydroelectric 1,799.0
(499.7)
1,155.2
(320.9)
1,298.9
(360.8)
waste-to-energy (50% of total) 226.1
(62.8)
268.9
(74.7)
392.9
(109.1)
photovoltaic solar 65.4
(18.2)
185.8
(51.6)
217.5
(60.4)
total renewable 2,090.3
(580.7)
1,609.9
(447.2)
1,909.3
(530.4)
grand total 2,961.2
(822.6)
1,959.5
(544.3
)
2,346.3
(651.8)
(*) 1 GWh= 3.6 TJ

Table No. 75 illustrates the primary sources used, expressed in energy terms (TJ and GWh). The conversion efficiency of Acea photovoltaic panels comes to around 14% (100 kWh of solar energy on the panels, transforms into 14 kWh of electricity).

It can be noted that in the last two years, the percentage of waste-to-energy in the electricity generation mix has increased progressively, demonstrating the technological maturity and efficiency of the two new waste-to-energy lines of the plant running at San Vittore del Lazio. 

The ratio between total electricity generated, indicated in table No. 74, and the potential energy from primary sources used (table No. 75) reveals an average conversion efficiency of around 36% in 2012

97 In detail, district heating serves 34,152 inhabitants (2012 figures) and concerns buildings for the volume of 3,118,962 cubic metres.

Table No. 75 - POTENTIAL ENERGY, BROKEN DOWN BY PRIMARY ENERGY SOURCE USED (2010-2012)

TJ (GWh)(*)   
primary energy source2010
20112012
Diesel (gas oil) 39.0
(10.8)
64.4
(17.9)
27.0
(7.5)
natural gas (combined cycles and co-generation) 1,542.8
(428.5)
197.6
(54.9)
141.1
(39.2)
Waste-to-energy 2,227.7
(618.7)
2,378.2
(660.6)
3,273.8
(909.4)
Hydroelectric 2,122.2
(589.5)
1,370.5
(380.7)
1,571.7
(436.6)
photovoltaic solar 468.0
(130.0)
1,325.8
(368.3)
1,553.9
(431.6)
Grand total 6,399.7
(1,777.5)
5,336.5
(1,482.5)
6,567.5
(1,824.3)
(*) 1 GWh= 3.6 TJ

Certain descriptive data of the Group’s thermoelectric and hydroelectric plants are provided in table No. 76 and in the subsequent fact sheets. The waste-to-energy and photovoltaic plants are by contrast described in the pertinent sections (also see the Environmental Accounts).

Table No. 76– ACEA PRODUZIONE ELECTRICITY PLANTS

Thermoelectric plants Hydroelectric plants
Tor di Valle plant: combined cycle section(*) (Rome)
Natural gas fuel – gross output 125.7 MW
A. Volta Castel Madama plant (Rome)
gross output 9.4 MW
Tor di Valle Plant: co-generation section (**) (Rome)
Natural gas fuel – gross output 19.3 MW
G. Ferraris Mandela plant (Rome)
gross output 8.5 MW
Montemartini plant (Rome)
Diesel fuel – gross output 78.3 MW
Salisano plant (Rieti)
gross output 24.6 MW
  G. Marconi Orte plant (Viterbo)
gross output 20 MW
Sant’Angelo plant (Chieti)
gross output 58.4 MW
Cecchina plant (Rome)
gross output 0.4 MW
Madonna del Rosario plant (Rome)
gross output 0.4 MW
grand total: gross output 345 MW
(*) The combined cycle unit of the Tor di Valle Plant is equipped with bleeding facilities on the steam turbine (**) The co-generating turbogas unit at Tor di Valle is open-cycle in type and supplies the district heating service to the districts of Torrino Sud, Mezzocammino and Mostacciano.

hydroelectric production

A. Volta Castel Madama Plant (Rome)

Plant type Run-of-river water
Type of use of energy produced Coverage of basic needs
Rated output 9.4 MW
Capacity of the basin or reservoirs interlocked 148,000 m3
Available head (from concession) 40.29 m
Maximum derivable delivery 25 m3/s
Gross electricity produced in 2012 15.55 GWh

G. Ferraris Mandela Plant (Rome)

Plant type Run-of-river water
Type of use of energy produced Coverage of basic needs
Rated output 8.5 MW
Capacity of the basin or reservoirs interlocked 6,400 m3
Available head (from concession) 27.15 m
Maximum derivable delivery (from concession) 30 m3/s
Gross electricity produced in 2012 10.26 GWh

Salisano Plant (Rieti) 

Plant type Run-of-river water (aqueduct)
Type of use of energy produced Coverage of basic needs
Rated output 24.6 MW
Available head 85.94 m Capore
242.50 m Peschiera
Maximum derivable delivery (from concession) 5.5 m3/s Capore
10 m3/s Peschiera
Gross electricity produced in 2012 175.94  GWh

G. Marconi Orte Plant (Terni) 

Plant type Run-of-river water
Type of use of energy produced Coverage of basic needs
Rated output 20 MW
Capacity of the basin or reservoirs interlocked 6 million m3
Available head (from concession) 11.45 m
Maximum derivable delivery (from concession) 180 m3/s
Gross electricity produced in 2012 48.07 GWh

Sant’angelo Plant (Chieti)

Plant type Reservoir
Type of use of energy produced Coverage of peak needs
Rated output 58.4 MW
Capacity of the basin or reservoirs interlocked 83.30 million m3 Bomba
21 million m3 Casoli
Available head (from concession) 141.20 m
Maximum derivable delivery (from concession) 40 m3/s
Gross electricity produced in 2012 108.77 GWh

hydroelectric production - minor plants 

CECCHINA (ROME)

Plant type Run-of-river water (aqueduct)
Type of use of energy produced Coverage of basic needs
Rated output 0.4 MW
Maximum derivable delivery (from concession) 1.1 m3/s
Available head (from concession) 30 m
Gross electricity produced in 2012 0.95 GWh

MADONNA DEL ROSARIO (ROMA)

Plant type Run-of-river water (aqueduct)
Type of use of energy produced Coverage of basic needs
Rated output 0.4 MW
Maximum derivable delivery 0.825 m3/s
Available head (from concession) 43 m
Gross electricity produced in 2012 1.26 GWh

thermoelectric production

Tor Di Valle Plant - combined cycle (ROME)

Fuel type Natural gas
Type of use of energy produced Mid-merit (electricity) and district heating (thermal energy)
Rated output of a.c. generators 41.04 MW turbogas No. 1
41.04 MW turbogas No. 2
43.6 MW Steam Unit
Plant surface area 35,000 m2
Chimney stack height 30 m
Quantity of fuel consumed in 2012 408.474 kNm3
Gross electricity produced in 2012 1.09 GWh
Total gross efficiency in 2012 25.23%

Tor di Valle Plant – co-generation (Rome)

Fuel type Natural gas
Type of use of energy produced Coverage of peak needs (electricity) and district heating (thermal energy)
Rated output of a.c. generators 19.32 MWe
Chimney stack height 20 m
Quantity of fuel consumed in 2012 3.328 kNm3
Gross electricity produced in 2012 8.05 GWh
Total gross efficiency in  2012 26.54% only electricity 72.87% with heat recovery

Montemartini plant (Rome) 

Fuel type Gas oil (diesel) with low sulphur content
Type of use of energy produced Coverage of peak needs
Rated output of a.c. generators 26.1 MW Turbogas No. 1
26.1 MW Turbogas No. 2
26.1 MW Turbogas No. 3
Chimney stack height 1 x 13.35 m + 2 x 20 m
Quantity of fuel consumed in 2012 0.76 Ml
Gross electricity produced in 2012 1.94 GWh
Total gross efficiency in 2012 25.95%

The figures concerning the installed capacity are broken down by energy source and indicated in table No. 77. There was an essential confirmation of the previous year’s situation.

Table No. 77 - Group installed electric power broken down by energy source (2010-2012)

(MW)    
Energy source 201020112012
Diesel (gas oil) 78.3% 78.3% 78.3%
natural gas (combined cycles and co-generation) 144.9 144.9 144.9
Waste-to-energy (*) 20 25 25
Hydroelectric 139.3 121.7 121.7
photovoltaic solar (**) 25 52 46
Grand total 407.5 421.9 415.9
(*) As already occurred in 2011, during 2012 the Terni WtE plant was shut down for completion of the revamping work, while the San Vittore del Lazio plant was only considered for the two lines running. (**) The decrease in the installed power of the PV, in 2012, was due to the start of disposal of the assets.

The availability indexes for Acea Produzione plants by installation and the average output in the last three years, confirmed as positive on average, are shown in tables 78 and 79.

 

Table No. 78 - Availability indexes for Acea Produzione plants (2010 - 2012)

Energy source Plant Overall availability(%) Scheduled unavailability (%) Unscheduled unavailability(%)
   2010 2011 2012 2010 2011 2012 2010 2011 2012
Natural gas Tor Di Valle (combined cycle - CCGT) 89.5 95.2 95.9 5.6 0.0 0.0 5.0 4.8 4.1
Tor Di Valle (co-generation section) 89.1 99.2 99.4 1.3 0.8 0.0 9.6 0.0 0.6
Diesel Montemartini 91.4 99.9 100.0 1.9 0.0 0.0 6.7 0.1 0.0
Hydroelectric Salisano 99.4 37.1 99.3 0.4 62.9 0.1 0.2 0.0 0.6
S. Angelo 86.9 86.9 92.3 3.7 8.4 4.1 9.4 4.6 3.6
Orte 99.0 69.3 75.5 0.9 30.6 17.8 0.1 0.1 6.8
Castel Madama 97.0 99.4 98.5 2.1 0.5 1.5 0.8 0.2 0.0
Mandela 95.3 97.5 99.4 1.9 0.3 0.2 2.8 2.2 0.4
Minor installations 67.7 94.7 85.2 0.0 0.1 0.0 32.3 5.2 14.8
NB: the figure for the hours of scheduled/unscheduled unavailability cannot be provided as the indexes are calculated taking into account partial shutdown and load limits as well.

The following definitions must be taken into account in order to correctly interpret the figures provided in Table 78:

  • overall availability (%); this index refers to the period in which a plant or section thereof is available to produce energy, including periods it was not operational due to electricity market needs. It is obtained from the ratio between the available energy - equal to the difference between the maximum energy which can be generated and the unavailable energy (see following points) and the maximum energy which can be generated in the month.
  • scheduled unavailability (%): this index refers to the period in which a plant or section thereof was unavailable due to scheduled events (maintenance, etc.). It is obtained from the ratio between the energy unavailable during the scheduled event and the maximum amount of energy that can be generated in the month.
  • unscheduled unavailability (%): this index refers to the period in which a plant or section thereof was unavailable due to fault. It is obtained from the ratio between the energy unavailable during the fault event and the maximum amount of energy that can be generated in the month.

Table No. 79 - Average output of the Acea Produzione plants (2010-2012)

Plant average output 2010 (%) average output 2011 (%) average output 2012 (%)
Tor Di Valle (combined cycle - CCGT) 42.8 40.7 n.a. (*)
Tor Di Valle (co-generation section) 74.9 73.6 72.9
Montemartini 25.9 26.1 26.0
Salisano 85.9 85.8 88.0
S. Angelo 79.0 79.0 70.5
Orte 98.6 98.6 98.6
Castel Madama 82.7 83.0 82.6
Mandela 91.4 91.4 91.4
Minor installations 57.1 58.1 62.1
(*) The extremely low levels of production reported in the year under review do not make it possible to calculate a significant output indicator

Waste-to-energy    

Both the production of Waste derived Fuel (WDF) and the treatment of the same in dedicated plants are recovery processes aspiring to integrated policies for the management of the waste which tends to limit its conferral to landfills.

The waste-to-energy process, classified as per section IV of Italian Legislative Decree No. 152/2006 under recovery operations (RI), therefore represents a rational closure of the waste management cycle especially in the cases where reuse of the organic materials deriving from the separate collection of municipal waste is not economically advantageous.

Waste-to-energy activities in Acea are entrusted to A.R.I.A, which carries the same out via two plants located in San Vittore del Lazio and Terni.

The San Vittore del Lazio plant (FR), which will be able to treat around 320,000 tons a year of WDF once revamping work has been completed, carries out a significant role in the management of municipal waste in the Lazio Region. During 2012, the plant treated roughly 218,000 tons of WDF and produced around 218 GWh of gross electricity thanks to the full bringing onto stream of two of the three waste treatment plants envisaged as of 2015.

The installation, which had already implemented an environmental management system compliant with both the UNI EN ISO 14001:2004 standard and the European EMAS Regulations, extended said system to the two new lines at the end of 2011. Furthermore, in 2012 the certification audit of the safety management system as per OHSAS 18001:2007 was carried out with a positive outcome.

Table No. 80 - SAN VITTORE DEL LAZIO WASTE-TO-ENERGY PLANT: RUNNING FIGURES (2011-2012)

    2011 2012
WDF treated (*) t 158,557 218,256
gross electricity produced (GWh) 149.43 218.24
electricity efficiency (**) (%) 23.0 24.0
recovery capacity (***) (MWh/t) 0.9 1.0
(*) Together with the WDF, the plant uses natural gas (3,056,153 Nm3 in 2012) as auxiliary fuel to constantly maintain optimum conditions in the combustion chamber. (**) Ratio of gross electricity produced to total energy load introduced with the waste used. (Lower calorific value of the waste considered conventionally as 15,000 kJ/kg) (***) Ratio of gross electricity produced to quantity of waste treated.

The Terni plant has a single waste-to-energy line with a potential of 52 MWt and uses paper industry pulper as fuel, a particular residue from the processing of cellulose for the production of paper, from which the sole resource technically still usable is recovered: energy. At the end of December 2012, the plant was started up again after a shutdown of around two years for the performance of revamping work.

SAO’s waste management services: sustainable management of waste  

SAO (Servizi Ambientali Orvieto), operates in the waste management sector via its own treatment, recovery and disposal plants located in Pian del Vantaggio, Orvieto (TR). It manages a landfill for non-hazardous waste and a selection, cleansing and composting plant, also seeing to the municipal hygiene services for a number of municipalities in the Province of Terni.

In line with the Acea Group’s environmental policy, SAO SpA handles the activities seeking to pursue the maximum recovery of the materials, favouring the production of energy from renewable sources and the reduction of waste to be sent to landfills.

In detail, during 2012 the following took place:

  • the launch of the first phase of expansion of the landfill run in the Municipality of Orvieto.
  • the doubling of the operations of the plant for exploiting energy from biogas produced by the landfill, which will make it possible to achieve a total of 2MW. 

The completion of a new anaerobic treatment line for organic waste is envisaged for July 2013, which will make it possible to produce electricity from the combustion of biogas released by digestion.

SAO operates in accordance with an integrated Environment and Safety Management System certified in accordance with the UNI EN ISO 14001:2004 and OHSAS 18001:2007 standards. It also holds EMAS registration.