Knowledge Capture - Pelamis Wave Power Ltd

Overview

July 2015

The zipped report file contains the 'Project Overview', which summarises the outputs of the 5 work packages that comprised Project Secure, and the 'P2 Operations Review', which summarises the activities completed offshore, the metrics used to measure success and areas identified for further work. 

Tank Testing and Scale Models

July 2015

Pelamis undertook many tank testing campaigns with a variety of models at different tanks around Europe.

This work package focused on tank testing and scale model construction. The reports cover the design and construction of the various scale models used by Pelamis and the equipment which is now owned by Wave Energy Scotland. A number of possibilities for future use of these models is given, exploring additional research opportunities. Good experimental practice is covered discussing various existing sets of tank test guides. Validation of numerical model using physical tests is covered with particular focus on the PELs suite developed in-house by Pelamis, covered in more detail in WP04.

A main report as well as supplementary reports are available to download here

• Summary: WES dissemination and capability statement
• Critique of Potential Future Work
• Physical model experimentation, supporting PELs numerical modelling validation.
• Using Pelamis Modelling Tools to Advance the Industry State-of-the-Art

Power Take-Off

April 2016

The extraction of useful energy from ocean waves requires that the waves act on some form of responsive mechanism able to resist the working force that the waves apply and hence transfer net power from the waves. This mechanism by which energy is transferred from the waves and into a useful form in the WEC is known as the power take-off (PTO).

The extent of a PTO system within a WEC is not always clear. In addition to motors, generators, actuators and other energy conversion components it could also be defined to include the bearing and sealing systems required to enable relative motion. Similarly, it could include transformers and other export equipment required to interface to a local electricity grid. For the purposes of this document, however, the boundaries of the PTO are taken to be the structural attachment points of the hydraulic rams at one end and the electrical export connection from the PTO at the other. The bearings, sealing systems are only discussed in limited detail to provide important context, as are the electrical export systems.

A main report as well as supplementary reports are available to download here

• PTO Overview
• PTO System Description and Functional Specification
• PTO System Performance and Reliability
• State of the Art and Onward Development
• PTO Applicability to Other Systems

Mooring and Connections

April 2016

The offshore infrastructure required for mooring a Pelamis WEC consists of a primary and secondary mooring system, machine rapid installation and removal systems, electrical export and communication systems and associated navigational aids and markers. This document gives an overview into the design of these components and systems, including the basis of design and methodologies used, along with specifications for the major components and, where appropriate, the rationale behind certain operational and design decisions as taken by PWP throughout the development of the mooring spread.

A vital consideration for any WEC during the early stages of design is the operations and maintenance strategy and methods for installation and removal of both the WEC itself and the moorings spread. In order to create an economically viable offering as a whole, developers must consider these aspects early in the design and optimisation process. PWP developed a number of innovative systems to enable offshore operations to be conducted with smaller vessels. Moving away from the anchor handling vessels originally used was a step change for PWP and a key learning point in the mooring development process.

PWP found third party verification to be a very valuable process once mooring design had been completed. It provides independent confirmation that the design in in accordance with good industry practice and employs a risk based approach based on Failure Mode and Effect Analysis (FMEA).

A main report as well as supplementary reports are available to download here

• Mooring & Connections Overview
• Moorings & Connections Ops Experience
• Moorings Onward Development
• Moorings Applicability to other Systems

Simulation and Modelling

April 2016

The PELs suite of simulation programs was continuously developed by PWP over the 17 year lifetime of the project. The programs use a variety of formulations adaptable to the task at hand, with respect to the computational effort and levels of detail required for modelling rigid bodies connected by a controlled joint. 

This report discusses the following topics:

• Significant and unforeseen findings
• Approaches to PELS verification studies
• Experimental validation studies
• Full scale validation studies
• Power comparisons
• Summary of experience from full scale testing of Pelamis P2 machines

Tank testing was used to validate the models, and this is covered in the Tank Testing section of this project.

A main summary report as well as supplementary reports are available to download here

• PELs Overview & Critique
• PELs Executables and Knowledge Transfer 
• Tank Testing
• Simulation and Modelling Recommendations
• 7th Scale Model Testing

Economics

April 2016

This report sets out the Pelamis experience with Cost of Energy (CoE) modelling, summarises the various tools developed and results obtained through the programme, and highlights the key insights it gave. It also draws conclusions and recommendations from the experience.

This report is written to provide insight into how the Pelamis models and projections moved and developed with time and with progress of the technology up the TRL scale. The information is captured here to provide assistance in assessing CoE projections for new or earlier stage technologies and to help ensure learning from this experience is realised.

An introduction and timeline of modelling techniques used, how they evolved into a comprehensive set of economic modelling tools as experience with real full scale machines was gained is given. This includes discussion on how initially optimistic projections become progressively more realistic. Also provided is a high level description for the primary set of economic modelling tools produced with and for utility partners and how they were validated with real machine data and the experience gained from them. The level of validation of the various inputs is summarised alongside the resulting error bounds. Where appropriate, this has been generalised to form a recommendation for confidence bounds in similar calculations.

Cost Metrics for WEC Machine Elements

April 2016

The cost metrics presented throughout this document are derived or estimated from known Pelamis P2 costs for components that were selected based on optimising the Levelised Cost of Energy (LCoE) for the Pelamis as a whole. 

All of the costs included in this document are discussed in more detail in the relevant cost metrics reports:

• PTO Cost Metrics covers PTO system costs as well as costs associated with the main structural elements
• Mooring & Connection Systems Cost Metrics provides further information on the basis of the moorings and electrical infrastructure costs.

The lowest up-front cost of components does not necessarily lead to the most commercially beneficial project and so a balance must be achieved. For example, doubling up on component to provide redundancy and fault tolerance may provide huge cost savings over the life of the project due to increased availability. 

The additional drivers, as well as cost, that need to be considered when selecting components include:

• WEC availability
• Reliability
• PTO efficiency
• Power Capture
• Impact on O&M costs and strategy. 

Separate pages detail cost metrics and costs in their most practical form for individual components, systems, assemblies, or component types within the following sub-systems:

• Pelamis Main Structural Components
• PTO Primary Transmission Components
• PTO Energy Storage Components
• PTO Secondary Transmission Components
• Miscellaneous Additional Components
• Mechanical Mooring Components
• SubSea Electrical Infrastructure

Pricing details were accurate at the time of writing in 2015, but should now be considered out of date. Supplier names have been redacted. 

PTO Cost Metrics

April 2016

The Pelamis P2 hydraulic PTO system comprised three main parts: primary transmission, secondary transmission, and the energy storage that lay between them. This report details the assumptions, costs and some of the various options for the three system parts. The majority of the costs used in the analysis are the actual costs for the P2-002 machine procured in 2010, however some costs associated with the earlier P2-001 machine have been used where required. 

Appropriate cost metrics are derived for each of the major components and their associated parts, and are presented throughout the document. For the primary PTO components, cost per unit weight or volume is likely the most relevant metric for each of the different types of technology described.

For the secondary PTO system, the cost per kW of electrical rated power is provided where possible or additional metrics such as cost per generator have been defined. In each section the scalability of the particular system in question has been discussed. Due to the modular nature of the energy storage and secondary systems, they lend themselves well to scaling up.

The cost breakdown includes hydraulic cylinders, manifolds and piping, control and instrumentation. Sample costs for a secondary PTO system of different electrical ratings ranging from 205kW to 1MW are also given.

This report gives more context and description to the PTO costs in the High Level Cost Metrics report.

Pricing details were accurate at the time of writing in 2015, but should now be considered out of date. Supplier names have been redacted. 

Mooring and Connection Cost Metrics

July 2015

This report looks at the Pelamis P2 mooring system and the cost metrics associated with the major components therein. The P2 mooring system was a chain based catenary spread incorporating electrical export and communication components.

The catenary mooring system utilised standard embedment anchors, with chain lines on the sea bed to give the required spring force, and synthetic tethers rising up through the water column to the machine connection point. The necessary equipment to enable the rapid connection and disconnection of the Pelamis WEC to/from its moorings was located at this connection point. This connection point included a remotely operated locking system to allow both mooring and electrical connections to be made in a single unit. The Tether Latch Assembly (TLA) costs are broken down to show elements including the wet-mate connector, dynamic cable and mechanical components.

The majority of costs used in this report are those for moorings components for the P2 mooring spreads deployed at the EMEC site in Orkney in 2010 and 2011 with the actual purchases being made from 2009 onwards. Some items in the system were replaced over the course of the P2 operations programme, procured as spares, or for ongoing operations and these later costs have been included if appropriate.
Each major component in the Pelamis mooring system is considered in the document and the most appropriate cost metric for that component defined. Appropriate metrics for each of the major components are then brought together to provide example costings for three indicative systems, namely;

• Single device with passive yaw system
• Single device with active yaw system
• 10 machine farm with active yaw system

This report gives more context and description of the mooring and connection system costs in the High Level Cost Metrics report. 

Pricing details were accurate at the time of writing in 2015, but should now be considered out of date. Supplier names have been redacted.