THE ROLE OF AN ELECTRICITY DISTRIBUTOR
AS A PROMOTER OF ENERGY EFFICIENCY
GB Zorzoli, C. Mirra, A. Messina - Acea S.p.A. Rome, Italy
Today’s advanced conception of energy efficiency aims at warranting the services required by end users by means of an effective fossile fuel consumption, which implies three concurrent targets:
; improving efficiency in the supply system;
; improving efficiency in the end uses;
; developing energy generation by renewable sources.
The electricity supply has a decisive importance for energy saving because of its valence as a base service not only for the efficiency of the end uses, but also for the efficiency of the supply system itself. This means that one important condition to be met is that many options like the development of diffused generation, new network planning techniques, tariffs incentivating the levelling of load curves at the various stages of the supply system, new management tools like GPS based cartography, new equipment like low loss transformers, can give a significant favourable contribution to meet energy saving objectives.
An increase of the energy efficiency is also greatly dependent on the information to all involved parties, on the training of relevant installers and operators, on the use of new technologies, the regulations concerning buildings, household and other appliances and, in general, on legislation supporting the use of renewable energy sources as well as on benefits and/or penalties set up to enforce energy saving actions.
This report gives an overview of the energy efficiency policies currently being implemented in Italy, outlining the role that Acea, as an electricity distributor in Rome for 1.6 million clients, is playing to contribute to improve energy efficiency.
2 Electricity consumption in Italy
The total energy consumption in Italy is typically covered by oil for a 35% share, by coal for about 25 % and natural gas for 21 %.. The primary electricity share is around 19%. The yearly growth factor of electricity consumption from 2000 to 2005 has shown an average trend of 2.2 % (Fig. 1).
Figure 1 Electricity consumption in Italy 2000 - 2005
The distribution of the total consumption is of about 51% for industrial and agricultural usage, 27 for commercial and services and 22 % for the residential sector (Fig. 2).
Figure 2 Sector electricity consumption (%)
A typical winter daily national load curve (Fig. 3) shows a peak to valley ratio of about 1.7, which is suggestive as far as load shifting potential is concerned.
Figure 3 National winter daily load curve
3 The regulatory policies
The European Directive 2006/32/CE on the efficiency of the end electricity uses gives a saving objective of 9% starting from 2008. This sets up a precise commitment for the UE member States. In July 2004 a ministerial Decree has introduced energy efficiency targets electricity and gas distributors must comply with, which can be wholly or partially replaced by purchasing Energy Efficiency Certificates (commonly named "white certificates") from ESCO’s.
Energy efficiency can be promoted by improving either the efficency in end uses, e.g. for
appliances (like low consumption light bulbs), heating and air conditioning (for example heat pumps), the use of thermal insulating materials and so on, or in energy generation (diffused
combined heat and power generation, renewables).
Moreover a November 1999 Decree established an obligation for all operators supplying to the
electrical system more than 100 GWh/year to provide at least 2 % of their fossile fired generation
from renewable energy sources. This requirement will be increased step by step (at present 2.35 %)
and constitutes a strong global incentive to the development of renewable source generation. To the generation by renewable sources is attributed a "green certificate" for every 50 MWh, which can be marketed and bought by producers who cannot meet the percentage requuired by the law. More specifically a program, based on the feed-in rule, to promote photovoltaic installations, is
Other significant actions deserve to be noted:
; certification of new buildings to comply with an energy consumption of the order of 30
Wh/square meter, with respect to the present value of 150/200 Wh/square meter
; the institution of the "energy manager" position for all industrial, commercial and public
administration subjects with a consumption exceeding 10,000 toe (industrial) and 1,000 toe
(commercial and administration).
Further incentives for energy efficiency and renewables development are included in the 2007 Budget Act.
4 Technology and Acea's actions for energy efficiency
4.1 The industrial sector
4.1.1 Public lighting
The energy efficiency solutions for public lighting systems basically concern the light bulbs, power factor compensation and light flux modulation according to predefined time bands. Control of the light flux has been identified as the most effective technique, when compared to voltage regulation, because it avoids possible extinction of the electric arc in the lamps and provides superior performances.
The advantages of the new electronic regulators compared to electromechanical ones are several:
; Increase of the energy efficiency also with reduced losses in the switching circuits
; Almost total elimination of reactive energy components
; Elimination of surge currents at the switching on
; Better ratio of light intensity reduction with respect to the saving in power
; Levelling of the supply voltage against network voltage variations especially during the
night and related energy saving
The available systems are of two types: the first uses power semiconductors to manage the load directly, whilst the second uses an intermediate very low impedance transformer thus decoupling the electronics from the load. These regulators can control higher loads with respect to the first devices.
All of these regulators can be remotely controlled, adding additional operation flexibility. The saving values shown in Fig. 4 are ideal in the sense that they refer to a high level of flux regulation, for an average lighting time of 4,110 hours per year.
Figure 4 Energy saving in lighting installations
4.1.2 District heating and climate services
District heating in Italy has so far been implemented only in large and medium sized cities (37), always using the heat from combined heat and power plants.
However the growth trend in the last years is about 7% , showing an increasing interest for this type of energy service.
Considering only towns with a population exceeding 25 thousand citizens, the potential of district heating is estimated more than 700 millions of cubic meters, only for the residential sector. If this potential were to be totally exploited, the resulting saving of primary energy would be around 1.8 millions toe per year, corresponding to 27% of the substituted conventional system consumption. Since a long time Acea is committed to the application of high efficiency and low environmental impact solutions, for energy supply services.
In particular Acea has implemented one of the first residential heating systems in Italy, supplied by a cogeneration plant equipped with a heat storage unit, which has contributed to match the electricity generation for the peak demand with the heating profile required by the supplied urban district.
The plant is operating since the first eighties and is at present being further expanded. In the last years, due to the constantly increasing demand of air conditioning in summer, tied also to a strong restart of the urban development, Acea, in cooperation with major home builders, has developed solutions for centralized production of heating and cooling services in new residential complexes.
The goal of these solutions, beside the optimization of the primary energy consumption, is to minimize the electricity usage, thus improving the efficiency and the reliability of the local electric network, by the implementation of diffused generation.
According to this concept, some different projects have been developed, based on tri-generation plants (electricity, heat and cooling) of reduced size, linked to distribution circuits of limited capacity.
These projects typically make use of small endo-thermal cogenerators with lythium bromide absorbers to provide cold water for the summer air conditioning.
The cogenerator covers the base thermal and refrigerating load (by the absorber), whilst load variations are coped with by conventional systems.
An interesting variant, concerns the exploitation of low enthalpy geothermal sources. In this case, the basic plant employs heat pumps exchanging heat with a thermal well made by water spilled from and possibly returned to an underground stream.
The availability of thermal sources with a practically constant temperature from 15 to 18 ?C allows the highest performance levels for both summer and winter operation and, accordingly, the best results from the energy efficiency point of view.
In the average an italian family of four persons consumes about 8 kWh of electric energy per day, itemized as shown in Table 1, and could save about 10 - 15 % on the consumption of household appliances.
Moreover many improvements can be obtained as far as heating is concerned, giving the clients information and advice to reduce energy consumption, via leaflets and Web site such as:
; choosing "A" rated appliances (such as fridges and washing machines);
; installing good insulation and heating controls;
; using condensing boilers
; using low energy light bulbs wherever possible
; moving furniture away from radiators, filling gaps with sealant, insulating the hot water tank
; fitting thermostatic radiator valves to administer heating
; adopting window panes with double glasses
Table 1 Share of electricity consumption by household appliances
Appliance Share of electricity consumption
Water boiler 20%
Water boiler 11%
Electric oven 4%
Other appliances 15%
The above mentioned actions will be even more enforce following what envisaged by the Action
Plan for Energy Efficiency issued by the European Commision on Ocotber 19 2006.
The Commission will begin, in 2007, the process of adopting minimum energy performance standards (eco-design requirements) in the form of implementing Directives for 14 priority product groups including boilers, water heaters, consumer electronics, copying machines, televisions, standby modes, chargers, lighting, electric motors and other products, in accordance with the time table shown in Fig. 5.
These Directives will also include, to the possible extent, indications of future requirements, e.g., 5 years later, in order to prepare manufacturers for the new requirements in the design cycle. The Commission will ensure that appropriate measuring methods will be developed on time through CEN/CENELEC or other appropriate means. Products that do not meet the agreed minimum requirements may not be put on the market.
Figure 5 UE Directive implementation time table
4.2.1 Gas heaters certification
Since many years Acea provides a service for the periodic certification of gas heaters, as appointed operator for the Municipality of Rome.
This activity beside ensuring the safety of the gas heaters, is an effective mean to improve the their efficiency and to channel information to the clients on energy saving.
ACEA is involved in the development of a 5 MWe CHPP fueled by wooden material residues. Since 65,000 ton/yr will be approximately required, a back-up from wooden material supplied by Italian traders will be provided. District heating (along with air cooling in summer by means of absorption chillers) will mainly concern the nearby buildings, but could eventually be extended to other users. Table 2 summarizes the main characteristics of the plant.
Table 2 Biomass CHPP data
Electric Power 5 MW
Biomass average heating power 2,500 kcal/kg
Biomass supply 65,000 ton/yr
Availability 7,500 hr/yr
Heat supply 8,000,000 kWhth/yr
Chill supply 6,600,000 kWhf/yr
The CHPP, which should be in operation by 2009, is to be considered as a first step in the ACEA plan to seize all the existing opportunities, also with reference to:
; the availability of low cost biomass produced by Short Rotation Forestry technology;
; the development of biomass gassifiers whose output purity fits the specifications required by
Diesel engines, so as to lower the size of cogeneration plants having biomass as a primary
As a first step to have ACEA acquainted with PV technology, a 49.3 kWp system (Table 3) is being installed on the roof of a building within the frame of the first Decree providing incentives for PV technology.
Table 3 Main characteristics of the PV system
Peak power 49.3 kW
Material Polycristalline Silicon
Expected electricity generation 60,000 kWh/year
The additional incentives for renewables included in the 2007 Budget Act (see above) include a rule for new buildings, which will have to install at least 0.2 kWp per each dwelling unit, and the alike Rome municipality prescriptions for new housings are opening an interesting market, Acea is getting ready for, having in mind to cover a relevant share of the future market of PV equipped buildings, which as an electric distributor will make their integration in the distribution network easier.
The focus on PV applied to buildings is leading ACEA to investigate the potential of the thin film technology which, besides promising sensitive cost reductions, can more easily integrated on building surfaces. As a matter of fact it allows production of modules:
; having chromatic uniformity
; having variable shape and/or size
; being transparent, if required
; even being flexible.
; aesthetically agreeable configurations
; efficient thermal and acoustic insulations
; effective wet seals
; water and snow tightness.
Within the above mentioned strategy some applications of PV thin films to buildings are foreseen in the near future as a step towards a more comprehensive commitment in that field. 4.3.3 Advanced developments
A cooperation agreement with the Università La Sapienza (Rome) involves ACEA in a joint applied research program on advanced prime drivers for diffused generation, down to microgeneration:
; a gas fueled 100 kW microturbine;
; a gas fueled 5 kW PEM fuel cell.
Both systems, installed in the Università La Sapienza in Rome and linked to specific end uses, will be operated to test their performance, mainly with reference to their reliability and costs in comparison with more conventional prime drivers for diffused generation down to microgeneration.
4.4 Automatic remote meter and network management
Systems for automatic meter management when improved by extending their scope also to the supervision of medium and low voltage distribution networks, like the one developed by Acea, can provide substantial contributions to energy efficiency, essentially by two different and somewhat concurring processes:
- the application of time of use tariffs
- the reduction of losses on the meters and the supply network
First of all the digital meters have a lower self consumption with respect to traditional electromechanical meters (one or two Watts less per meter).
This in the case of the Acea system being commissioned for 1.6 million clients, leads to a yearly saving of about 14 GWh.
Secondly the new meters give the clients useful information on their usage (load profiles, consumption trends) enabling them to "feel" what they are doing and select the best tariff option for their supply.
The first process uses the leverage of energy price inducing the client to shift his usage of energy intensive appliances to off peak hours thus producing two effects:
- the client becomes aware of his interest in managing the more energy consuming usages
(water heater and washing machines)
- he can also verify the effects of a clever use of his appliances (for instance lowering the
washing temperature for his laundry)
The second process depends on the distributor really knowing how his network is operated, by monitoring the load on the MV/LV transformers, recording the transformer and user load profiles and making energy balances between the energy supplied to the low voltage network and the energy registered by the supplied meters.
In this way it is possible to configure the electricity network in an optimal way, reducing energy losses significantly.
The report gives an overview of options which can be undertaken by an energy utility to contribute to energy saving.
The regulatory framework is of course a prime factor to promote and support the improvement of energy efficiency, however, to be fully exploited, it requires the involvement of many operators, among which the energy utility can be of great importance.
The electricity distributor has also significant options to save energy in its own trade and specific focus has been given to the potential of remote network control and meter management systems, of public lighting technologies and of diffused generation, to achieve energy efficiency goals.