Chick, J.P.

Harrison, G.P.

Thomson, R.C.

As renewable energy technologies continue to develop, questions are arising over the environmental impacts associated with the process of converting low-carbon energy sources into electrical power. In order to make informed decisions for future developments of the energy system, and to confidently evaluate environmental impacts for market trading, it is necessary to develop a detailed understanding of the indirect life cycle impacts of renewable power generation from the manufacture, operation and decommissioning of generators and network infrastructure.The Pelamis is emerging as a leading wave energy converter, with a new commercial-scale site currently under development off the coast of Shetland in the UK. This research applies process-based Life Cycle Assessment (LCA) to the Pelamis to systematically analyse resource use and emissions to the environment at each stage of its life cycle. While LCA has already been applied to a range of energy technologies and networks [1-5], to date very few studies have been carried out in the marine renewables sector, and even fewer of these consider the broad range of environmental impacts tending to only concentrate on carbon emissions and embodied energy [6-9].Further to presenting the new analysis, this work will investigate the effect of practitioner decisions on LCA results. In 2007 a carbon and energy audit was carried out on the Pelamis P1 device [7]. This found that the carbon intensity was 23 g CO2/kWh, comparable to a large wind turbine. Early results from the new full LCA suggest that it may produce a higher figure. Such variations in results could be due to variations in practitioner assumptions, methodology and primary data sources. This research will highlight the assumptions that have the most significant impact on the results, and will suggest best practice guidelines for future analyses of renewable generators.1. Odeh, N. A. and Cockerill, T. T., Life cycle analysis of UK coal fired power plants. Energy Conversion and Management 2008. 49: 212-220.2. Riva, A., D'Angelosante, S. and Trebeschi, C., Natural gas and the environmental results of life cycle assessment. Energy 2006. 31: 138-148.3. Vestas Life cycle assessment of offshore and onshore sited wind power plants based on Vestas V90-3.0MW turbines, 2 Edn. Vestas Wind Systems A/S, Randers, Denmark 2006.4. Harrison, G. P., Maclean, E. J., Karamanlis, S. and Ochoa, L. F., Life cycle assessment of the transmission network in Great Britain. Energy Policy 2010. 38: 3622-3631.5. Jones, C. I. and McManus, M. C., Life-cycle assessment of 11 kV electrical overhead lines and underground cables. Journal of Cleaner Production 2010. 18: 1464-1477.6. Douglas, C. A., Harrison, G. P. and Chick, J. P., Life cycle assessment of the Seagen marine current turbine. Proceedings of the Institution of Mechanical Engineers Part M-Journal of Engineering for the Maritime Environment 2008. 222: 1-12.7. Parker, R. P. M., Harrison, G. P. and Chick, J. P., Energy and carbon audit of an offshore wave energy converter. Proceedings of the Institution of Mechanical Engineers Part a-Journal of Power and Energy 2007. 221: 1119-1130.8. Soerensen, H. C., Naef, S., Anderberg, S. and Hauschild, M. Z., Life Cycle Assessment of the Wave Energy Converter: Wave Dragon International Conference on Ocean Energy, Bremerhaven, Germany 2006.9. Cavallaro, F. and Coiro, D., Life Cycle Assessment (LCA) of a marine current turbine for cleaner energy production 3rd International Conference on Life Cycle Management, Zurich 2007

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     Edinburgh Research Explorer                                      Life Cycle Assessment in the Marine Renewable Energy SectorCitation for published version:Thomson, RC, Harrison, GP & Chick, JP 2011, Life Cycle Assessment in the Marine Renewable EnergySector. in LCA report - Instruments for Green Futures Markets: Proceedings from the LCA XI InternationalConference, October 4-6, 2011, Chicago, IL, United States. American Center for Life Cycle Assessment, pp.120-125, LCA XI, Chicago, United States, 4/10/11.Link:Link to publication record in Edinburgh Research ExplorerDocument Version:Peer reviewed versionPublished In:LCA report - Instruments for Green Futures MarketsGeneral rightsCopyright for the publications made accessible via the Edinburgh Research Explorer is retained by the author(s)and / or other copyright owners and it is a condition of accessing these publications that users recognise andabide by the legal requirements associated with these rights.Take down policyThe University of Edinburgh has made every reasonable effort to ensure that Edinburgh Research Explorercontent complies with UK legislation. If you believe that the public display of this file breaches copyright pleasecontact openaccess@ed.ac.uk providing details, and we will remove access to the work immediately andinvestigate your claim.Download date: 05. Apr. 2019Life Cycle Assessment in the Marine Renewable Energy Sector R Camilla Thomson, Gareth P Harrison, John P Chick1 1Institute for Energy Systems, School of Engineering, University of Edinburgh, Edinburgh, UK  Abstract  Reliable figures for the life cycle impacts of power generation are needed to inform developments of the energy system and enable market trading of environmental credits. Marine energy is likely to form a significant part of the future energy mix in the UK and the Pelamis wave energy converter is emerging as one of the most promising devices in this sector. This study examines the environmental impacts of the Pelamis. By comparison with the results of an earlier carbon and energy audit for the same device, the implications of practitioner decisions on LCA results are investigated, specifically with regards to the allocation method for dealing with materials recycling. Keywords: Life cycle assessment, wave energy, recycling methods, renewable energy, carbon emissions  Introduction  The drive to reduce Greenhouse Gas (GHG) emissions has led to the development of new technologies to harness renewable energy. In the UK marine energy has the potential to supply around 20% of electricity demand, so significant developments are occurring in the marine renewables sector (Callaghan and Boud, 2006). However, while marine energy sources are themselves ‘carbon-free’, there are wider environmental impacts associated with the process of converting this energy into electrical power. In order to make informed decisions for future developments of the energy system, and to confidently evaluate environmental impacts for market trading, it is important to develop a detailed understanding of the life cycle impacts that arise indirectly due to the manufacture, operation and decommissioning of generators and network infrastructure.  Unlike conventional power generation and wind power there is little consensus on the general design of wave and tidal energy converters. New technologies are constantly emerging and few full Life Cycle Assessments (LCAs) have been carried out to date. Some high-level analyses, however, have been published, assessing the embodied carbon and energy of the material content of marine devices (Banerjee et al., 2006; Woollcombe-Adams et al., 2009). This paper details a full LCA of the Pelamis, one of the most promising devices in this sector (Figure 1). The analysis follows the framework described in the ISO 14040 series of standards, which allows a number of practitioner assumptions (ISO, 2006).  Figure 1: The Pelamis (PWP, 2011)  The results are compared to an earlier carbon and energy audit of the same device to examine how variations in assumptions and methodology, specifically that of recycling allocation, affect LCA results (Parker et al., 2007). The findings will be used to better inform comparisons of the environmental impacts of different marine energy technologies. Developed by Pelamis Wave Power Ltd, the P1 version of the Pelamis wave energy converter was successfully installed at the world’s first commercial wave farm at Aguaçadoura, Portugal, in 2008. The experience has been fed into the second-generation P2 device currently on test at the European Marine Energy Centre. Several commercial projects for the P2 are under development, and lease agreements have been agreed for two Scottish farms comprising around 70 devices (PWP, 2011).  The Pelamis is a semi-submerged snake-like offshore wave energy converter. The P1 version is 120 m long, 3.5 m in diameter and rated at 750 kW. It has four cylindrical sections linked by three Power Conversion Modules (PCMs) at the hinged joints. The moorings allow the Pelamis to face into the oncoming waves and the joints flex vertically and horizontally as the wave front passes (Figure 2). This motion is resisted by hydraulic rams that pump high-pressure oil into hydraulic motors, in turn driving generators. The resistance of the rams can be tuned to maximise power capture in small sea states while protecting the device from potentially damaging storm waves. Figure 2: Side view of Pelamis (Parker et al., 2007)   Goal and Scope  In 2007 an in-depth life cycle carbon and energy audit of the Pelamis P1 device was published by Parker et al. (2007). It found that the energy and carbon intensities of the generated energy were 293 kJ/kWh and 23 gCO2/kWh generated. This paper expands the analysis to a full life cycle inventory and impact assessment. The results of the two studies are compared to investigate the effect of practitioner assumptions, and the comprehensive results also highlight the components, materials or life cycle stages with the largest environmental impacts. The system boundary of the current study encompasses the entire life cycle from “cradle-to-grave” (Figure 3). Physically this includes the device, its moorings and sub-sea connecting cable, but excludes all downstream electrical components. The functional unit is one kilowatt-hour of output power (1 kWh), with a calculation reference flow of 1 Pelamis device. Figure 3: Pelamis Life Cycle  To facilitate comparison with the analysis carried out by Parker et al. (2007), the fundamental assumptions and base data have been retained. In line with this it is estimated that the power output of a single device installed at a typical site off the coast of Scotland will average 2.97 GWh/year over the 20-year design life. The successful installation at Aquaçadoura found that the Pelamis performed as expected, so this assumption is still considered valid (PWP, 2011). The study assumes that all major components and sub-components are manufactured in the UK and subject to UK energy statistics and transport distances. The typical wave farm is within 200 miles of a commercial port.  The study was carried out with SimaPro (version 7.2 PhD). Life cycle inventory data was mostly sourced from the Ecoinvent database, which is recognised as one of the most comprehensive sources of such data in Europe (Ecoinvent, 2010). Data not available within Ecoinvent was sourced from alternative datasets or literature. The EDIP 2003 impact assessment method was applied, as it includes a broad range of impact categories and was developed for use with Ecoinvent data, minimising inaccuracies caused by mismatches.  Life Cycle Inventory Analysis (LCI) The quantities of raw materials, processing and manufacturing methods, and transportation were based on figures derived from the manufacturer’s own records (Parker et al., 2007).  The main structure of the Pelamis is formed from cylindrical steel tube sections with sand used as ballast. The mooring and cabling system includes several plastic components. Electrical equipment, housed in the nose tube, collects and transforms the power to high voltage for export to shore. The hydraulic power-take-off, generators and control equipment are located in the PCMs.  A mass-based analysis was carried out for the structure, hydraulic system and mooring components (Table 1). Such data was not available for the pre-fabricated components, such as fixings and electrical items, and sourcing detailed LCI data for these is time-consuming, so cut-off criteria were defined to exclude inputs without a significant environmental impact (ISO, 2006). These criteria were applied to a preliminary cost-based analysis of carbon emissions and energy consumption, finding that the transformer, main generators and switchboard should be included in the study. Other pre-fabricated components were excluded as they contributed less than 1% to the total impacts.  Table 1: Material quantities in the Pelamis P1 Stock Material Mass (kg) Steel 561954 Sand 475722 Stainless Steel 550 Nylon 6 416 Polyurethane 343 Glass Reinforced Plastic (GRP) 90 PVC Pipe 55 The next life cycle stage involves the transportation of components from the manufacturing plant to the dockyard for final assembly. A range of sea vessels are then used for installation of the moorings and power cabling, sea trials, tow to site and latching to the moorings. Annual maintenance operations also involve the use of sea vessels. Data for this stage was based on manufacturer estimates, as a complete picture of real operation and regular maintenance has not been registered to date. These estimates are understood to be conservative, with the key aim of confirming and ensuring survivability. The device itself has very few operational requirements, as remote monitoring and control is entirely computer-based, onshore, so no allowance has been made for the small environmental impacts of this. Ecoinvent includes mass-distance data for freight transport. Other processes and sea vessel operations were approximated from fuel consumption data. It is expected that decommissioning will involve sea vessel operations associated with the recovery of all hardware. The waste will be split into two streams, with the majority of metals being recycled (90%), and the remainder of the waste going to landfill. UK-specific LCI data for landfill is not readily available so average European data was selected from the European Life Cycle Database (v2.0). Where this was not available the emissions were approximated using Ecoinvent data for Switzerland.  Recycling of waste materials has a significant effect on the environmental impact of a device, as the use of recycled materials avoids the greater impact of primary material production. This results in an environmental credit. Marine energy converters may be responsible for both the consumption and creation of recycled materials, so it is not immediately clear where this environmental credit should be applied. Currently there is no consensus on the most appropriate methodology for allocating the benefits of recycling, as it can be applied to the product that uses the recycled material, the product that produces the recyclable scrap, or both products (Jones, 2009).  The recycled content approach is one of the most commonly applied allocation methods, as it is used in the assessment of cradle-to-gate impacts of materials for LCI datasets. All credit is allocated to the product that uses the recycled material, as recycling is of no benefit without the resulting material being consumed. However, recycled materials could not exist without a primary product to generate them, and therefore it could be argued that the recycling credit should be allocated to the product that is recycled. This can be calculated using closed loop substitution, the method recommended by the International Iron and Steel Institute (IISI, 2002). This was the method applied by Parker et al. (2007).  The 50:50 method is a compromise that recognises that both the upstream and downstream products are necessary for recycling, and assumes that half of the benefit goes to each product (Jones, 2009). The 50% figure is fairly arbitrary and open to discussion, but it does ensure that the results of different studies can be combined without double-counting. This is the only method that achieves the goal of promoting sustainable design that minimises primary material use and maximises recyclability of materials at the end-of-life.  In order to examine the effects of applying these different methods, the results are presented for all three: The Recycled Content (RC) method, the substitution method (Sub) and the 50:50 method (50:50). Table 2: Results of life cycle impact assessment Impact potential Total Impact potential Total RC Sub 50:50 RC Sub 50:50 Global warming (gCO2e/kWh) 30 24 27 Hazardous waste (mg/kWh) 2.3 1.4 1.8 Acidification (x10-3 m2/kWh) 2.9 2.6 2.7 Slags/ashes (mg/kWh) 3.7 3.7 3.7 Ozone depletion (μgCFC-11e/kWh) 2.3 2.2 2.3 Human toxicity    Ozone formation    Air (m3/kWh) 640 480 560 Vegetation (m2.ppm.h/kWh) 0.42 0.38 0.40 Water (m3/kWh) 1.6 0.63 1.1 Human (x10-5 pers.ppm.h/kWh) 2.8 2.6 2.7 Soil (x10-3 m3/kWh) 5.5 4.6 5.0 Eutrophication    Ecotoxicity    Terrestrial (x10-3 m2/kWh) 5.3 5.0 5.2 Water chronic (m3/kWh) 10 9.5 9.9 Aquatic (N) (mgN/kWh) 21 20 20 Water acute (m3/kWh) 1.9 1.7 1.8 Aquatic (P) (mgP/kWh) 9.8 8.2 9.0 Soil chronic (x10-3 m3/kWh) 2.9 2.4 2.7 Radioactive waste (μg/kWh) 470 390 430 Bulk waste (g/kWh) 7.9 10 9.0 Results All results are presented in relation to the functional unit of 1 kWh of output power. The life cycle inventory produces data for the energy consumption associated with the device (Table 3), giving an energy intensity of 311-381 kJ/kWh, which corresponds to a payback time of 21-25 months. Over 90% of this embodied energy is associated with the manufacturing stage, mostly due to the steelmaking process.  Table 3: Energy intensity Life Cycle Stage Energy Intensity (kJ/kWh) RC Sub 50:50 Materials & Manufacture 348 402 375 Assembly & Installation 11 11 11 Operations & Maintenance 19 19 19 Decomg. & Disposal 3 -121 -59 TOTAL 381 311 346 Figure 4: Life cycle stage analysis (RC method) 0% 20% 40% 60% 80% 100%Global warming 100aOzone depletionOzone formation (Vegetation)Ozone formation (Human)AcidificationTerrestrial eutrophicationAquatic eutrophication EP(N)Aquatic eutrophication EP(P)Human toxicity airHuman toxicity waterHuman toxicity soilEcotoxicity water chronicEcotoxicity water acuteEcotoxicity soil chronicHazardous wasteSlags/ashesBulk wasteRadioactive wasteResources (all)Materials and Manufacturing Assembly & InstallationOperation & Maintenance Decommissioning & Disposal The full environmental impacts of the Pelamis are summarised in Table 2 on the preceding page. The GWP is of particular interest: 24-30 gCO2e/kWh. Taking the carbon intensity of the offset grid electricity as the 5-year average of 0.499 kgCO2/kWh, in accordance with Defra/DECC guidelines (Hill, 2009), carbon payback will be achieved in 12-14 months. This will be shorter if the device offsets only marginal carbon intensive generation.  Manufacturing and maintenance shipping operations are significant contributors across all categories (Figure 4). It can be seen in Figure 5 that the substitution method generally gives the most optimistic results, due to the average recycled content of European steel being around 40% (Classen et al., 2009), and the assumed recycling rate for waste being 90%. Figure 5: Effect of recycling method on results 0% 50% 100% 150% 200%Global warming 100aOzone depletionOzone formation (Vegetation)Ozone formation (Human)AcidificationTerrestrial eutrophicationAquatic eutrophication EP(N)Aquatic eutrophication EP(P)Human toxicity airHuman toxicity waterHuman toxicity soilEcotoxicity water chronicEcotoxicity water acuteEcotoxicity soil chronicHazardous wasteSlags/ashesBulk wasteRadioactive wasteResources (all)Recycled Content 50:50 Method Substitution Method Effect of Practitioner Assumptions This study was carried out to a higher level of detail than that published by Parker et al. (2007), with a different software tool and different LCI datasets. In particular freight transport and waste treatment were dealt with more comprehensively. However, a comparison of the analysis results shows that it is the recycling method that has the most significant effect. If the recycled content method is applied, the results of the current study are approximately 30% greater than those found by Parker et al. However, by applying the same substitution method as that used in the earlier study, the difference is reduced to approximately 5% (Table 4). The inclusion of all greenhouse gases increases the carbon intensity by 3-6%. Table 4: Comparison of results Impact Current study Parker et al. GWP (g CO2-e/kWh) 24 - CO2 Emissions (g/kWh) 23 23 Embodied Energy (kJ/kWh) 311 293 Conclusions This paper presents a detailed Life Cycle Assessment of the Pelamis wave energy converter. It expands an earlier carbon and energy audit to a full assessment of environmental impacts. The resulting carbon intensity of 24-30 gCO2e/kWh generated and energy intensity of 311-381 kJ/kWh generated compares well with the earlier study. It highlights that the choice of recycling method can significantly affect the LCA results so it is important that assumptions about recycling credit are clearly stated for future studies in this sector. As the 50:50 method provides an average of both figures it is considered to be the most appropriate for marine energy converters.  References Banerjee S., Duckers L.J., Blanchard R., Choudhury B.K. (2006): Life Cycle Analysis of Selected Solar and Wave Energy Systems. National Conference on Advances in Energy Research, Bombay. Callaghan J., Boud R., (2006): Future Marine Energy. The Carbon Trust, Available from http://www.carbontrust.co.uk/Publications/pages/publicationdetail.aspx?id=CTC601&respos=0&q=ctc601&o=Rank&od=asc&pn=0&ps=10. Classen M., Althaus H.-J., Blaser S., Scharnhorst W., Tuschmid M., Jungbluth N., Emmenegger M.F., (2009): Ecoinvent Centre - Life Cycle Inventories of Metals - Data v2.1. Swiss Centre for Life Cycle Inventories. Ecoinvent, (2010): Ecoinvent database v2.2. Swiss Centre for Life Cycle Inventories, Available from http://www.ecoinvent.org/home/. Hill N. (2009): 2009 Guidelines to Defra/DECC's GHG Conversion Factors: Methodology Paper for Emission Factors. Department for Environment, Food and Rural Affairs. IISI (2002): World Steel Life Cycle Inventory - Methodology Report 1999/2000. International Iron and Steel Institute, Brussels. ISO, (2006): BS EN ISO 14040  Environmental management - Life cycle assessment - Principles and framework. UK, British Standards Institute. Jones C.I. (2009): Embodied Impact Assessment: The Methodological Challenge of Recycling at the End of Building Lifetime. Construction Information Quarterly, 11(2), pp. 140-146. Parker R.P.M., Harrison G.P., Chick J.P. (2007): Energy and carbon audit of an offshore wave energy converter. Proc. IMechE Part A: J. Power and Energy, 221(A8), pp. 1119-1130. PWP, (2011). Pelamis Wave Power. Retrieved June 2011, from http://www.pelamiswave.com/. Woollcombe-Adams C., Watson M., Shaw T. (2009): Severn Barrage tidal power project: implications for carbon emissions. Water and Environment Journal, 23(1), pp. 63-68. 

Life Cycle Assessment in the Marine Renewable Energy Sector

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Life Cycle Assessment in the Marine Renewable Energy Sector

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