Eco-sustainable routing of power lines for the connection of renewable energy plants to the Italian high-voltage grid

Rodolfo Araneo 0 1 Salvatore Celozzi 0 1 Chiara Vergine 0 1 0 C. Vergine National Transmission Network , Terna S.p.A., Rome, Italy 1 R. Araneo (&) S. Celozzi DIAEE, Electrical Engineering Division, University of Rome ''La Sapienza'' , Rome, Italy Routing of high-voltage electric transmission lines for the connection of renewable energy-distributed generation plants is a critical issue from an environmental point of view. A standard methodology that accounts for multiple perspectives, influence factors and is able to mediate between weighted constraints can be a useful tool for the regulating bodies that are involved in approval processes. The methodology can be an effective support to increase reliability, save consumers' money and mitigate the unavoidable impacts of the lines on the population living nearby. In this paper we investigate the suitability of a procedure employed by Terna, the Italian high-voltage transmission system operator, to identify the corridors where to route new overhead transmission lines with the lowest environmental impact. The methodology is based on the subdivision of all the relevant constraints dictated by environmental issues and territory legislations in four main classes. A real case study concerning the design and connection of a wind farm placed near Collarmele, in the center of Italy, shows the effectiveness of the proposed methodology. - Governments and companies are investing large efforts in developing technologies to improve clean renewable energy sources [3, 6] due to several economic and environmental reasons [1, 4, 5, 7, 12, 17, 24, 29, 31, 32]. The energy savings and the promotion of renewable energy sources are an essential part of the European energy policy [13, 19, 21, 23, 26] aimed at ensuring competitiveness, sustainability and security of energy supply, as well as their integration with the best environmental practices to reduce emissions of CO2 and other greenhouse gases [20]. According to the European Energy Roadmap for moving toward a competitive low-carbon economy, a secure, competitive and decarbonized energy system in 2050 is possible [1416]. In this framework, in recent years, the development of renewable energy in Italy has experienced an extremely strong growth, boosted by an effective incentive system. The GSE, the state-owned company which promotes and supports renewable energy sources in Italy with the Italian Regulatory Authority for Electricity, Gas and Water (AEEG) estimated on December 2011 that nearly 250,000 connection requests had been accepted on April 2011, corresponding to about 196 GW of power. Nevertheless, on closer view of these requests, 42 GW was related to plants already connected, 14 GW to plants under construction and 140 GW to plants that had not yet been approved for construction and operation. This is a clear evidence that the authorization process was, and still is, a decisive step for the construction of a new plant for renewable energy generation. Thus, the feasibility study prior to the beginning of the process itself is even more crucial. The feasibility of a new plant [22, 25, 30], especially if its nominal rated power is so high to request a connection to the high-voltage (HV) transmission network operated by Terna S.p.A., the Italian Electrical Transmission System Operator, is conditioned by the capability of the network to accept the new power production. This comprises, from a technical point of view, the identification of a new or existing electric substation to which the plant can be connected and the identification of a suitable land corridor through which to route the new transmission line [27, 28]. The proper design of the new connection infrastructure from a prescribed start point to a prescribed end point is the real critical point in the authorization process, rather than the power plant itself. In fact, it is well-known that local populations are often hostile to the routing of new power lines, because they do not perceive any direct benefit from their installation and have serious concerns about their health, landscape and property values [3335]. Overhead power lines are large linear elements in the landscape. Their scale is usually much larger than that of objects in close proximity, e.g., houses and trees, so that their major effect is likely to be the visual intrusion of the towers on the corridors through which the lines are routed. Moreover, their construction may disturb sites of natural interest, requiring new access tracks and causing during their life periodic disturbance due to maintenance operations. Consequently, the optimal goal in building new transmission lines is to effectively minimize the negative impacts on people and environment while ensuring safety, reliability and cost savings for the utility. It has been observed that the existing energy models and research tools usually employed in the design of new plants have low concerns on land use, landscapes and biodiversity. Consequently, it would be difficult to provide comprehensive decision support by using only these tools. However, suitable energy models, ecological assessment models and multi-criteria approaches have been proposed with great potential for interlinking. A comprehensive framework for the assessment of environmental impacts is provided by Strategic Environmental Assessment (SEA), which is developed for environmental impact analysis for policies, plans and programs [18]. In this paper, we investigate the feasibility, from an environmental point of view, of the methodology applied by Terna S.p.A in siting a new overhead power line for a wind farm located in the center of Italy. The methodology is based on the subdivision of all the relevant constraints (dictated by environmental issues and territory legislations) in four classes: Exclusion, Rejection, Problem and Attraction. Consequently, the procedure is named ERPA. The subdivision is performed on structured processes and is based on the use of geographic information systems (GIS) analysis concepts. The GIS system can assemble large data quantities of the various factors into a meaningful analysis outputting the results graphically. The results, either visually or statistically, help to convey the corridor where the new connecting line can be routed at minimum environmental cost. The ERPA framework enables the inclusion of relevant environmental information into decision making. Within the ERPA framework, the significant constraints on the environment that are taken into account include the specific issues regarding biodiversity, population, human health, soil, water, cultural heritage, landscape and the interrelationships between the above constraints. The wind farm The case study involves the construction of a wind farm with installed capacity of 16 MW placed in the territory of the two municipalities, Cerchio and Aielli, located in the province of LAquila in the Italian central region Abruzzo, as shown in Fig. 1. In (...truncated)