The sizing of electric power facilities is based on a power budget. This consists fi rstly in determining the power input required to operate each individual piece of equipment. Next, the total power is calculated by adding together the power requirements for equipment likely to be operating simultaneously. The installed capacity is therefore often of vital importance and sized to cover rare events.
Effi cient energy use means fi rstly being aware of its consumption. It is therefore vital when planning a facility to allow for the monitoring of consumption by each family of equipment. The plans should therefore include a general low-voltage panel with a separate set of busbars for each station that is to be monitored together with a meter on each busbar.
This monitoring system should be supplemented by monitoring of equipment operating periods and times and their response to the sensors conditioning their operation (luminance meter for strong lighting, pollution sensor for ventilation systems, etc.). Setting up this type of tool is the only effective way of identifying the most energy-intensive stations and leading considerations of how best to make them more energy-effi cient.
Several major technical choices impact on energy consumption although project constraints do not leave much room for manoeuver. This is the case when deciding on the excavation method, which is closely linked to the site's geotechnical constraints, to the vacuation of rubble and to the potential for the reuse of this rubble. These key choices are made at the upstream studies stage. They also apply to tunnel equipment e.g.
• the number of ventilation plants,
• the number of electricity supply outlets (whether there is an outlet at each portal, intermediate outlets),
• lighting principles: interaction of the choice of road surface with the lighting,
• etc.
7.4.1 Lifecycle analysis
Most of the topics addressed in this document have impacts at local levels, in the direct and immediate environment of the tunnel (noise, contamination of water resources impacted by the tunnel project, pollution air at tunnel portals, vibrations, etc.). The lifecycle analysis (LCA), already discussed in chapter 7.1.2, does not meet these very local concerns: water and air pollution are only integrated through global emission reports. It does, however, make it possible to factor in the overall impact on the environment. It is therefore particularly suitable for topics such as energy consumption or greenhouse gas emissions (GGE). Concerning GGE, the lifecycle analysis is based on the same principles as more widely known method of the Carbon Footprint®. To perform an LCA it is necessary to have a copy of the environmental report for the various materials used. This may be obtained through Environmental and Health Statements (FDES). The LCA tools is standardised to international level, in particular through standards ISO 14040 and ISO 14044 (see chapter 7.6).
7.3
STUDY APPROACH
73
STUDY APPROACH
ASSESSMENT METHODS AND MEANS
The environmental protection criterion must be clearly specifi ed so as to avoid giving rise to a discretionary power.
Although control over consumption is often a question of good sense, as mentioned above, this still requires the use of monitoring tools.
Among the rules of good sense, it is a good idea to check the operating settings for the various systems and equipment. For example, there is no point in setting air-conditioning at 21°C if 25°C will suffi ce. Sometimes, it is better not to turn air-conditioning on at all but, rather, focus on renewing air using mechanical, or even natural means. This does not, however, mean going too far the other way and ignoring the equipment's conditions of operation: lifetimes for leaktight lead batteries (data for 20°C) are halved if the ambient temperature reaches 25°C.
The choice of equipment and technology may also be informed by energy concerns e.g.
• the choice of lighting technology: symmetrical or counter beam,
• the choice of lamps: high-pressure sodium or fl uorescent. When choosing source types, one important criterion is the "lumen/watt" ratio (the higher the ratio the brighter the lamp per 1 Watt of energy consumption). This ratio is usually greater than 100 lumens/Watt for sources used in tunnels. Note that, currently, LED sources have a lumen/watt ratio of approx. 70 lumens/Watt. The various equipment found in tunnels have very different lifetimes. These may vary from a few years (electronic and IT equipment) to several tens of years (electromechanical equipment). It is therefore essential to take careful consideration of an equipment's energy consumption, lifetime and end-of-life (recycling). The Table below indicates the lifetimes for several types of equipment. The values show are averages adapted to fi t the case of tunnels i.e. averages that can vary widely in either direction. Lastly, the equipment operating conditions and the stresses acting on them also impact strongly on the related lifetimes.
The choice of equipment can quickly become very technical. It is not always necessary to target a specifi c product when drafting contracts. The simplest approach is to consider the issue in terms of performance, by defi ning minimum yields for instance. Under the provisions of Article 53 of the French Public Procurement Code, bid selection criteria may be based on environmental considerations and, therefore, focus on energy consumption in particular. These "criteria and their weighting or ranking are indicated in the notice of a competitive public tender or in the tender documents".
7.5
IMPACT LIMITATION MEASURES
Family Sub-assembly lifetime in Average
years Remark(s) Electricity supply / distribution Cells 20 KV 25 Transformers 30 Cables 30 Backup power supply
Generator 25 Révisions intermédiaires
UPS 15 Leaktight lead battery 5 Nickel-cadmium battery 20 Lighting Luminaires 20 Cables ducts 20 Junction boxes 20 Ventilation
Jet fans 15 Révisions intermédiaires
Ventilation plants 25 Y compris équipements annexes (registres, insonorisation) Pumps Pumps 20 Centralised Technical management Pollution
sensors 10 à 15 Suivant le type d'équipement Brightness
sensors 15
PLCs 10 Peuvent être obsolètes au bout de 5 à 6 ans CCTV Cameras 15 Peuvent être obsolètes au bout de 8 à 10 ans Display screen 10 Signalling Counting loops 10 Fixed message panels 20 Variable message panels 15 Telephony Tunnel tel. stations 15 Central exchange hub 25 Radio retransmission Radiating cable 20 Emitters 15 Antennae 20
Table 17: lifetimes for several types of equipment (source: CETU [30])
74
7
Lastly, note a few standards relating to the lifecycle analysis: • standard ISO 14040 "Environmental management -
Lifecycle analysis - Principles and frameworks" that describes the main characteristics of the LCA and the good practices governing the performance of such studies; • standard ISO 14044 "Environmental management -
Lifecycle analysis – requirement and guidelines" that specifi es the requirements and provides the guidelines for performing a LCA;
• standard NF P01-010 that deals with the characteristics of construction products and Environmental and Health Statements (FDES) that specify the implementation conditions for construction products;
• standard NF P01-020 that highlights the main points of the French consensus in terms of the environmental quality of buildings.
Energy consumption is one of the topics that has to be addressed in the impact study for a road infrastructure project. Article L122-3 of the Environmental code states that "[...] for transport infrastructures, the impact study includes an analysis of the collective costs for pollutions and disturbances as well as of the potential benefi ts for local communities together with an assessment of the energy consumption generated by project execution, particularly in terms of any displacements it may cause or prevent".
The commitments made under Grenelle Environment and the ensuing laws specifi cally target energy consumption. The aim of the French programming Law No. 2009-967 of 3 August 2009 relating to implementation of the Grenelle Environment is to ensure "a new sustainable development model that respects the environment and is combined with a reduction in the consumption of energy, water and other natural resources". Accordingly, it targets areas such as construction and transport in general without targeting structures such as tunnels in particular.
[28] Émissions dans l'air en France, substances relatives à l'accroissement de l'effet de serre / CITEPA / update 2009. [29] Guide pour la maîtrise des coûts de fonctionnement des
tunnels routiers / CETU / 2005.
[30] L’instruction technique pour la surveillance et l’entretien des ouvrages d’art (ITSOA), fascicule 40 / CETU / 2011. [31] Guide de la fourniture de l'énergie électrique en tunnel /
CETU / 2002.