By Gladys Rodriguez,2014-03-30 21:40
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Renewable energy for public transport can contribute on both fronts providing a sustainable, clean and attractive alternative to the private car.


    Pat Bell, BE, MIEI

    ENTRAC - Energy Transport Actions

    85 Rail Park, Maynooth, Co. Kildare, Ireland

    Tel/Fax: +353-1-6289329, Email:

    Jim O’Malley, BSc, CEng, MIMechE

    ENTRAC - Energy Transport Actions

    65 Heatherview, Sligo, Ireland

    Tel/Fax: +353-71-61027, Email:

    Wilhelm Bodewigs, Dipl. Ing.

    Sligo Town Centre Partnership

    20 John Street, Sligo, Ireland

    Tel/Fax: +353-71-50095, Email:


Most European cities are experiencing ever growing traffic conditions leading to increasing problems of

    congestion and emission levels with a consequent loss of quality of life. This is particularly true of tourist

    destinations most of which suffer from seasonal peaks in their traffic levels. One of the most effective

    ways of tackling this problem is to take an integrated approach of introducing more environmentally

    friendly vehicles and simultaneously encouraging a modal shift from private transport to public transport.

    Renewable energy for public transport can contribute on both fronts providing a sustainable, clean and

    attractive alternative to the private car. This paper will review these renewable options, which fall into

    two broad categories of biofuels and electric vehicles powered by renewable energy sources. The options

    will be considered in the context of an ALTENER funded feasibility study undertaken in Sligo.

Sligo is a small city in the North West of Ireland with a population of 20,000 projected to double to

    40,000 when the city is upgraded to a regional urban growth centre. Traffic congestion has already grown

    rapidly in recent years and is set to continue in line with projected population, economic and tourist

    growth. Public transport is underdeveloped. Sligo Corporation is urgently considering its approach to

    these problems and is anxious to do so in a sustainable way. It co-operated with the Sligo Town Centre

    Partnership to secure ALTENER funding to carry out a feasibility study into the use of renewable energy

    for local public transport.

In particular, the study is focusing on using small-scale hydro-electricity from the Garavogue river which

    runs through the city from Lough Gill. The electricity could be used to charge stationary battery

    installations which in turn would be used as rapid recharge stations. An innovative flywheel powered

    ultra-light tram will be considered, integrated with other forms of transport such as electrically assisted


    Key words:

    transport, renewable energy, biofuels, hydro-electricity, electric vehicles, ultra-light tram, tourism, Sligo


ENTRAC is an engineering consultancy specialising in energy efficient and sustainable actions with

    particular emphasis on transport. ENTRAC is experienced in carrying out investigations and evaluations

    for national and local governments, large corporations and the European Commission to which it also

    gives technical support.


    One of the most effective ways of tackling this

    Sligo is a small city in the North West of Ireland problem is to take an integrated approach of with a population of 20,000 projected to double to introducing more environmentally friendly vehicles 40,000 within 15 years when the city is upgraded to and simultaneously encouraging a modal shift from a regional urban growth centre. It is the focal point private to public transport. Renewable energy for of the region due to its geographic location and low public transport can contribute on both fronts density structures in regional habitation. The main providing a sustainable, clean and attractive traffic corridor is North-South due to the restrictions alternative. The renewable options considered fall of the Atlantic to the West, Lough Gill to the East into two the broad categories of biofuels and electric and the river Garavogue which, coincidentally, are vehicles powered by renewable energy sources [2]. also major tourist attractions.

     2.1 Biofuels This corridor links both the North and West of Biodiesel produced from vegetable oil is technically Ireland and also Northern Ireland with North West very feasible. In Ireland the most likely form would Ireland. A considerable amount of the traffic into the be rape methyl ester (RME) as rapeseed is the only area is related to tourism. The area is often referred oil crop commercially produced; sunflower oil is to as Yeats Country as it featured prominently in the more common in Southerly regions. Pilot projects poetry and writings of W.B. Yeats. Lough Gill, for indicated that it is particularly suited to tourist example, contains the famous “Lake Isle of applications. For example, a 12.8m cruiser used Innisfree”. County Sligo also contains one of the biodiesel for 6 months with no technical problems richest concentrations of prehistoric monuments in and two shuttle buses in a national park were also Western Europe. enthusiastically received. However, it was concluded

     that biodiesel produced from rapeseed will remain Traffic congestion has grown rapidly in recent years too expensive in the near future and that, in addition, and is set to continue in line with projected the supply is too variable on the agricultural side [3]. population, economic and tourist growth. Investment in transport infrastructure and public transport have not kept up with the pace of development. Sligo

     Corporation is urgently considering its approach to these problems and is anxious to do so in a sustainable way and in co-operation with local business. With this objective it co-operated with the Sligo Town Centre Partnership to secure ALTENER funding to carry out a feasibility study into

     sustainable solutions to the traffic problems [1]. The

     aims of the project are to: ? Examine the utilisation of renewable energy for local public transport ? Confirm that the river Garavogue is a suitable power source for such a transport system ? Create an example of excellence for new urban


     Figure 1: Biodiesel fuelled cruiser on the Shannon 2. RENEWABLE ENERGY FOR CLEAN SUSTAINABLE TRANSPORT A cheaper alternative which can be considered in the shorter-term is waste cooking oil. Its properties are Most European cities are experiencing ever growing more variable than those of pure unused oils so traffic conditions leading to increasing problems of quality control of the incoming oil, as well as the congestion and emission levels with a consequent ester produced from it, will be important. loss of quality of life. This is particularly true of Nevertheless, this is an option that could be of tourist destinations most of which suffer from particular interest in tourist areas. A good collection seasonal peaks in their traffic levels. system is necessary and can contribute to solving a

waste disposal problem as its use in animal feed is

likely to be more restricted in the future.

     Biogas is produced from organic waste as a by-

    2.2 Renewable energy for electric vehicles product of sewage treatment and has similar

    Wind energy is a widely available source of properties to compressed natural gas (CNG) as a

    renewable energy particularly in NW Ireland which vehicle fuel. The use of biogas is particularly

    has one of the most favourable wind regimes in attractive from the point of view of greenhouse gas

    Europe where there has been a number of wind farm abatement as no net CO2 is produced and would

    developments in recent years [6]. have potential applications in many tourist locations.

     London Underground, interestingly, has identified offshore wind power as a long term strategic energy source and the use of local wind energy is seen as a possible development in Sligo harbour in a second phase of the project.

    Solar energy for transport is a novel concept in

     Europe. One example is the photovoltaic (PV) recharging station for electric vehicles in Palermo where 95 electric vehicles were purchased under ZEUS. The PV modules form the roof of a cantilever structure which shades the electric vehicles while they are charging and keeps them cool. The plant produces enough electricity each year to drive the vehicles about 90,000 km. This is an unlikely option

     though for Sligo given its Northerly latitude.

     Figure 2: Biogas refuelling in Stockholm Stockholm has four refuelling sites for biogas with the fuel being produced at a sewage treatment facility and distributed to the refuelling stations by truck. Under the THERMIE project ZEUS,

     Stockholm introduced over 200 biogas vehicles and

     increased the production of biogas significantly [4]. At a national level in Ireland there is significant potential to produce biogas from the biomethanation of domestic, industrial and agricultural wastes and considerable quantities are vented from landfill sites. For the purposes of this project however it was concluded that a suitable form of biogas would not

     be available locally in the short to medium term. Ethanol is another petrol alternative which is being Figure 3: Photovoltaic recharging in Palermo used, notably in Sweden, in various forms such as E85 (a blend of 85% ethanol and 15% petrol), E10 and E5 [5]. It is currently available at 8 refuelling Hydro-electricity is the most likely and convenient

    sites in the Stockholm region. source of renewable electricity for Sligo. It is the

     most readily available, with the potential to utilise There is a long tradition in Ireland of growing barley the river Garavogue which runs through the centre for the brewing and distilling industries and sugar of the city from Lough Gill to the sea. This option beet for the sugar industry. In recent years there has will now be examined in more detail. been significant production of potable alcohol from whey residues but is not expected to be available for

    biofuel purposes in the near future.

    river at low water flows. This would mean that 3. DEVELOPMENT OF HYDRO-

    returning migratory fish would be able to pass ELECTRICITY RESOURCE IN SLIGO

    rapidly upriver and not be stressed by having to wait

    in Sligo Bay. 3.1 The hydro-electricity resource

     The Garavogue river runs through the centre of the

    3.3 Future potential city from Lough Gill which is 3km upstream and

    Potential available power is directly related to the 6.5m above sea level. In the past there were two

    flow of water and the head. The average head at the mills situated in the stretch of river which runs

    upper weir has been increased from under 1m to through the city centre. The river is tidal below the

    1.5m and the long term mean flow on the river has second or lower weir as it opens out to the Atlantic.

    been measured at 10.54 m3/sec (excluding fish pass). In a national survey carried out in 1898 the total

    This gives a potential available power at this weir of effective hydro potential of the river in Sligo city

    about 120 kW. was estimated to be 200kW continuously. Over the

     past 100 years all the hydro installations were let go

    The upper weir is still classed as a low head site and into disuse [7].

    either a Kaplan turbine or an Axial Flow turbine from Newmills Hydro have been identified as being best suited and requiring little modification to the existing civil works. Their advanced guide vane and runner blade control systems ensure the highest possible efficiency output from the turbines over a wide range of flows [8].

     This completes the first part of the energy chain i.e. river (hydro) energy to turbine to generator to electric energy. To extend this energy chain to electric vehicle it is necessary to insert energy storage and vehicle charging elements into the chain at this point. 3.4 Energy storage and electric vehicle charging

     The main option envisaged is for the hydro- electricity to feed directly to a storage system consisting of a battery bank which would be used for

     the charging of electric vehicles. Modern battery

    systems are highly sophisticated with microprocessor Figure 4: Lake Isle of Innisfree

     controls and are maintenance free. The modular

     units are safe and compact and integrated HVAC

    equipment maintains an optimum environment for 3.2 Recent developments

    To meet the increased demands for water in a maximum performance and long life. Such a system growing city, a new water storage scheme is would also enable fast charging of electric vehicles currently under construction. This has involved the with minimal impact on the local grid. upper weir being replaced and raised in height (adjustable) and a new fish pass being installed. At Mains-based fast charging systems are also being the same time a new hotel development is taking developed, both conductive and inductive. All these place at the site of the old mill adjacent to the weir. options will be studied in more detail including Sligo Corporation insisted in the planning sizing, distribution and backup. More detailed permission for this development that the old mill economic analysis has also still to be undertaken race be preserved, thus retaining the possibility of including the study of storage and charging systems reinstalling a hydro scheme. in Luxembourg and Stockholm.

    Commercial developments at the lower weir have 4. ELECTRIC VEHICLE OPTIONS left the mill race unusable without intervention works. However the Fishery Authorities are keen 4.1 Electric vehicle procurement that this weir and fish pass are restored as it would In recent years a wide variety of electric vehicles result in a reasonable depth of retained water in the have been coming on the market ranging from

    bicycles to buses. But various obstacles have minibuses and electric minibuses were examined. hindered their widespread use such as their high cost, The findings of the THERMIE project lack of infrastructure and a lack of sufficient SAGITTAIRE and a previous study by the authors incentives to boost early market penetration. [9] lead to the conclusion that a suitable hybrid-

     electric minibus is not yet commercially available. A To remove these obstacles the ZEUS project got more likely option in the short term might be the involved in purchasing and putting into use over electric minibus Tecnobus demonstrated in Florence

    1000 zero and low emission vehicles. The vehicles under the THERMIE project JUPITER. A number of were purchased through a common procurement these buses have also come into service in Liverpool process which has already resulted in the price of under JUPITER-2 and their performance will be some electric vehicles, such as the Citroën Berlingo closely monitored [10]. van and Fiat Elettra car, coming down to the same level as their conventional equivalents. There is a Particular interest has been shown in the ultra light growing interest from third parties in the ZEUS tram developed by the UK project partner Parry common procurement process and this will be People Movers Ltd. The principal features of this followed with interest by the project. system are its low infrastructure cost and unique

     flywheel energy storage. This low voltage system 4.2 Electrically assisted bicycles combined with regenerative braking results in a very A small fleet of electrically assisted bicycles is being low energy requirement. made available for hire with support from the INTERREG programme (through Energy Challenge - a joint Republic of Ireland/Northern Ireland initiative). With the input of ADFC, the German partner in the project, a bike station and a bike infrastructure is currently being designed. Sligo is linking up with Northern Ireland Electricity (NIE) to promote the acceptance of these bicycles and

     demonstrate their potential to replace the private car

     for travel to school, shopping and work.

     Figure 6: Parry light tram If used as the only source of power, the flywheels need to be recharged at electrical supply points up to 2km apart which would be ideally suited to the system of energy storage envisaged. All-in-all it is an extremely environmentally friendly system being quiet running, emission free and requiring no

     overhead or underground cables on the street. This

     enables the tram system to be installed with minimal disruption and to run either on segregated rail or in traffic [11]. 5. SUSTAINABLE MOBILITY FOR SLIGO Figure 5: Electric bicycle Sligo urgently needs a transport plan which will integrate infrastructure development with clean public transport and satisfy the mobility needs of its 4.3 Public transport and ultra light tram options citizens in a sustainable manner. As the main emphasis of the project is on local public transport, options such as hybrid-electric

The project is studying the concept of an urban (Swedish Transport and Communications transit corridor based on the ultra light tram system Research Board,, 1998

     [6] Turbowinds technical sheets. outlined above. This would integrate with a small urban bus system using the Rendezvous-concept [7] Maguire & Bracken. Hydro Electric Potential at whereby arrival and departure times of buses are Sligo Weir, 1981 highly co-ordinated [12]. The public bus operator, [8] Newmills Hydro. Water Turbines. Bus Éireann, has just initiated Sligo’s first urban bus service which is a positive step and the railway [9] P. Bell, J. O’Malley & L. Dauby. Hybrid station has been identified as an ideal interchange Vehicle rd UITP International point making it the transport node for local, regional Development in Europe, 53Congress, Toronto, May 1999 and national public transport. [10] JUPITER-2 newsletters. Conversely, a controversial plan for a National [11] The Challenge of Ultra Light Rail. strategic road corridor would involve the destruction Tramways and Urban Transit, No. 733, Jan 1999 of over 50 houses and some historic warehouse [12] Assoc. of Town Centre Management, London. buildings at the old dock, cut the train and bus Integrated Transport for Town Centres, 1999

    stations off from the city centre and would not [13] Planning Dept., University College Dublin.

    Sligo 2020 Vision, 1998 integrate with public transport or other mobility measures. Sligo is the only city in Ireland with no

    out-of-town shopping centre and all city centre

    shopping areas are within walking distance. A

    previous report identified city centre streets suitable

    for giving priority to public transport and

    pedestrians over the private car [13]. The transit

    corridor outlined above would incorporate all

    relevant types of mobility interchange such as: Park

    & Ride, bicycle to bus, train to tram, train to bicycle,

    tram to bicycle, etc.


While the ALTENER study is not complete, the

    indications are that there would be sufficient hydro-

    electricity to supply the intended mix of passenger

    electric transport vehicles in the urban environment

    of Sligo. This would feed into the centre of the

    transit corridor, with wind energy feeding into both

    ends of an extended corridor in the longer term, thus

    providing a unique, innovative and autonomous

    system in the Irish urban landscape.


     [1] P. Bell, J. O’Malley & W. Bodewigs.

    Renewable Energy for Local Public Transport,

    REBUILD, Barcelona, Oct 1999

     [2] Connaught Regional Energy Study. DG XVII

    Regional and Urban Energy Planning, 1995

     [3] B. Rice. Promotion of the Use of Vegetable Oil

    as a Diesel Engine Fuel Extender/Replacement

    in Ireland. ALTENER, April 1995

     [4] ZEUS newsletters.

     [5] T. Månsson. Clean Vehicles With Biofuel, KFB

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