Jeffrey, Henry

Forehand, David

Winskel, Mark

Kerr, Paul

Energy Technology Partnership

Wave Energy Scotland

University of Edinburgh

2024-02-19T11:41:04Z

2024-02-19T11:41:04Z

2024-02-19

While wave energy has been under development for over 40 years, as of 2023 it has not reached commercialisation. The wave energy sector has yet to develop a low-cost device that can demonstrate a level of reliable long-term electricity generation. At present, cost of energy estimates for early wave energy arrays are around an order of magnitude higher than mature renewables such as wind and solar PV. Improvements in the wave energy sector’s economic performance are therefore necessary for it to be competitive with other forms of low-carbon electricity supply. Performance improvements could come through incremental improvements which come alongside the scale-up and deployment of the technology. These incremental improvements are illustrated by the experience curve, where unit costs fall as a function of cumulative deployment. This experience curve relationship has been demonstrated in several mature, fully commercial, forms of renewable energy technology, such as solar PV and wind. Over time, the aggregation of these incremental improvements can make an initially expensive technology far more cost-competitive. These incremental cost reductions are derived from several ‘learning effects’, including: learning by doing, economies of volume, economies of scale and incremental technology innovation. Alternatively, the performance improvements needed for the wave energy sector could come in part through radical technology innovation. This would entail a significant redesign of wave energy converters or their subsystems. In contrast to the incremental improvements alongside deployment, radical innovation could lead to a step-change in the performance of wave energy. Technologies such as direct conversion (which was studied in this thesis) could be enablers of radical innovation in the wave energy sector. This research investigates if radical innovation could enable low-cost wave energy, and if direct conversion technologies may have potential to deliver radical innovation in the wave energy sector. To carry out this investigation, the research was broken down into three main parts. The first part of the research had the aim of evaluating the level of subsidy investment that may be required to enable cost-competitive wave energy. This would consider incremental, deployment-related cost reductions, or cost reductions through radical innovation. To do this, a learning investment model was developed for the wave energy sector. Learning investment was calculated as the additional investment to subsidise the deployment of wave energy in comparison to the cost of an incumbent form of generation. This is similar to the total subsidy through market-pull policy mechanisms. To develop a baseline cost reduction scenario for the wave energy sector, representing incremental cost reductions achieved alongside deployment, the experience curve approach was used. LCoE estimates for early commercial wave energy arrays, and estimated learning rates from the literature, were used to develop the baseline scenario. Following this, a set of alternative cost reduction pathways were developed that also included step-change cost reductions through radical innovation. These innovations were represented as discontinuities in the baseline wave energy experience curve. The level of innovation cost reduction, cost to develop and time to develop the radical innovations in these scenarios was based on data from wave energy innovation programmes and sector guidance documents. The learning investment model was then used to evaluate the investment associated with both the baseline incremental cost reduction scenario and the scenarios that included radical innovation. The results from the first part of the research were that, for the wave energy sector to achieve a target LCoE of 100 EUR/MWh (representing the cost of an incumbent technology) through deployment-related cost reductions under the baseline assumptions, around 59 billion EUR is required in learning investment. However, this represents a lower limit to this investment, using baseline assumptions which are themselves relatively optimistic. If less optimistic assumptions are used, still within the range given in the literature, this total learning investment could be several hundreds of billions of EUR to achieve the LCoE target. When step-change cost reductions were introduced as a result of radical innovation, a large reduction in the total level of learning investment to achieve the LCoE target was observed in comparison with the base case deployment-only cost reduction scenario. These reductions in learning investment far outweighed the estimated cost of carrying out innovation programmes. This highlights that if the objective is to reach low-cost wave energy at the lowest possible public investment, supporting innovation programmes, even with low success rates, may offer the lowest cost pathway. A journal article was published based on the work that is presented in Part A of this thesis. This explored the learning investment associated with deployment and innovation related cost reduction scenarios for the wave energy sector. Direct conversion technologies (DCTs) are a class of technology that directly convert mechanical energy to electrical energy. This class of technology has been identified as a potential enabler of radical innovation for the wave energy sector by several funding organisations. The second part of the research aimed to develop an assessment process to evaluate the potential of DCTs for wave energy applications, and then apply this process to a selection of DCTs. To do this, a set of measurable design agnostic parameters were identified which could indicate a DCT’s potential in several areas required for a high-performance wave energy converter. These assessment parameters were based on the conversion efficiency, energy density, material cost, lifetime energy output, durability and embodied carbon of the conversion technologies. A screening process was then developed where minimum performance levels were set for these parameters to indicate viability of a DCT in wave energy applications. Once the screening process was developed, six direct conversion technologies were assessed using the process: dielectric elastomer generators (DEG), dielectric fluid generators (DFG), piezoelectric polymer generators, piezoelectric ceramic generators, triboelectric generators and magnetostriction generators. The results of part two of this research were that, of the six technologies that were assessed, four were rejected (piezoelectric polymer, piezoelectric ceramic, triboelectric and magnetostriction generators), as they demonstrated that they could not meet the required cut-off values in one or more of the assessment parameters. The other two technologies (dielectric elastomer and dielectric fluid generators) were allowed to pass the screening process as neither demonstrated that they could not meet the required cut-off values in any parameters. However, the process highlighted that there is limited publicly available data for some of the assessment parameters for both technologies — especially the parameters that required data on fatigue lifetime. This highlights that, of the technologies evaluated, only dielectric elastomer generators (DEGs) and dielectric fluid generators (DFGs) could be considered as viable options as an innovative technology for wave energy applications (using the cut-off values that were adopted in the screening process). Based on the parameters where comparable data existed, the most promising of these technologies was dielectric elastomer generators. Another significant benefit of having developed the process is its repeatability. The process was designed around parameters that should be measurable and relevant to a generic DCT that is considered for wave energy applications. Therefore, it can be used to assess other DCTs that are in future considered for wave energy applications, or to re-assess a technology if more data becomes available. The third part of this research aimed to carry out a more in-depth evaluation of how the most promising DCT, identified in Part B of the research, could be developed for large-scale wave energy applications. As mentioned above, only dielectric elastomer generators and dielectric fluid generators were not rejected by the screening process. Of these two technologies DEGs were identified as the most promising DCT, based on the available comparable data. Part three of the research investigates the barriers to the development of dielectric elastomer generators for wave energy applications, along with actions that could be taken to address these barriers. To do this, the potential barriers to DEGs were identified though a literature review. As noted in Part B, in some areas there is limited data on DEGs for wave energy applications, given the sector’s maturity. Therefore, to build upon the literature review, expert opinion was solicited by carrying out a series of semi-structured interviews with experts in the field of dielectric elastomer generators and wave energy. These interviews were used to identify what the experts saw as key barriers to DEG WEC development, and add any barriers not captured by the literature review. The interviews were also used to gather expert opinion on what actions could be taken to address the barriers to DEG WECs, how difficult these actions may be to carry out, and if the experts believed there was a prioritisation in which the barriers should be addressed. In the literature review, four high-level categories of barrier were established for DEG WECs. These were: Performance of the DEG, Manufacturing the DEG at scale, System integration for DEG WEC and Environmental effects of DEG. Within these categories, 13 subcategories were identified. During the semi-structured interviews, the experts were asked if these categories and subcategories covered the main barrier areas for DEG WECs. Eight of the nine experts agreed with the categories, with only one key barrier that did not fit in the original categories identified by the experts. During the course of the interviews, 33 key barriers were identified by the experts, with 35 actions identified that would address these barriers. Several common barriers and actions were identified by different experts, which highlighted areas of consensus. These also had large agreement with the literature review. This points towards clear barriers that need to be broken down for dielectric elastomer wave energy converter development, and actions that form the basis of future R&D activities that should be taken to address these. However, for some of the barriers and actions there was less consensus between the experts. For these barriers and actions, further work to help form consensus, such as workshops including a wider range of experts, may be beneficial in establishing appropriate R&D actions. Overall, the barriers and actions identified over the course of the literature review and semi-structured interviews highlighted the diverse range of barriers to DEG WEC development. The need for strong multidisciplinary collaboration, especially between industry and research organisations, was highlighted by several interviewees in order to address these barriers. This emphasised that ongoing communication, and a shared vision for the development of the technology between key stakeholders, would probably be beneficial in furthering dielectric elastomer-based wave energy conversion. To summarise, the first part of this thesis establishes the potential benefits that radical innovation could bring to the wave energy sector, in terms of reducing the total investment in wave energy deployment required to achieve cost-competitive wave energy. The second part develops an evaluation process to identify direct conversion technologies that may be enablers of radical innovation in the wave energy sector and uses this process to assess six direct conversion technologies. The third part of the thesis carries out a more detailed evaluation of the most promising of these technologies, dielectric elastomer generators, with regard to the key barriers to the technology’s development and the actions that could be taken to overcome these barriers.

https://hdl.handle.net/1842/41457

http://dx.doi.org/10.7488/era/4189

en

The University of Edinburgh

Kerr, P., Noble, D. R., Hodges, J., & Jeffrey, H. (2021). Implementing Radical Innovation in Renewable Energy Experience Curves. Energies, 14(9), 2364. https://doi.org/10.3390/en14092364

wave energy

wave energy converter

Innovation

Cost Reduction

experience curve

Learning Curve

learning rate

learning investment

Dielectric elastomer

Dielectric fluid

Piezoelectric materials

Triboelectric

Magnetostriction

technology assessment

Radical innovation for the wave energy sector: an investigation of the potential of direct conversion as an enabling technology

Thesis or Dissertation

Doctoral

PhD Doctor of Philosophy