R&D Towards Commercialization of Sea Wave Slot Cone Generator (SSG) Overtopping Wave Energy Converter: selected topics in the field of wave energy

Global energy needs are likely to continue to grow steadily for the next two and a half decades (International Energy Agency, 2006). If governments continue with current policies the world’s energy needs would be more than 50% higher in 2030 than today. Over 60% of that increase would be covered in the form of oil and natural gas. Climate destabilizing carbon-dioxide emissions would continue to rise, calling into question the long-term sustainability of the global energy system. More vigorous government policies in consuming countries are steering the world onto an energy path oriented to reduce the consumption of fossil fuels and related greenhouse-gas emissions and to the development of Renewable Energy Sources (RES). Diversification of RES is fundamental in such a path to ensure sustainability. In this contest wave energy can provide great contribution, having its worldwide resource been estimated to be up to 10 TW (Engineering Committee on Oceanic Resources 2003; Cruz et al. 2008); depending on what is to be considered useful, this may cover from 15% to 60% of the World energy demand calculated for 2006. Indeed, together with the overall trend of all renewable energies, wave energy has enjoyed a fruitful decade. Improvement of technologies together with financial support at different levels gave space to new ideas, bringing the research to gamble on different concepts. While innumerable projects went through an initial testing phase that lasts 5-10 years, only few of them reached the sea prototype testing and eventually commercialization. After the phase of R&D developers had spent at least 15 mill Euro in average (Kofoed et al. 2008).

Good ideas can fail between the R&D and market stage. This event is described by Tom Delay, Head of the Carbon Trust, as “falling into the valley of death”. This is the stage where the wave energy sector is. The limited ability of many ventures to attract private financing is certainly one of the major barriers. However, it is also very often a symptom of other underlying, and more fundamental issues. In reality, ventures fail to obtain funding because there are significant gaps between what the ventures are offering to investors and what the potential investors are seeking (Murphy and Edwards 2003). When risks associated to the investment is high, simply the deals often don’t look very attractive. It is indeed necessary to reduce information gaps or asymmetries between ventures and private investors, and to promote an accelerated shift from a technology to a market focus.

This Thesis is presented as a collection of works published by the author on her research on the Sea wave Slot cone Generator wave energy converter. These include 1 accepted and 2 submitted journal papers; 7 peer-reviewed conference papers. The results are based on laboratory tests, numerical simulations and feasibility studies. Research presented in this Thesis contributes to reduce the technical and non-technical risks associated to the wave energy sector and promotes accelerated shift from technology to market focus. This has been done by using the R&D steps for a specific wave energy converter as an example of best practice for wave energy development towards commercialization.

The Sea wave Slot cone Generator (SSG) is a multilevel wave energy converter. Incoming waves overtop the structure and the water is temporarily stored in reservoirs at a higher level than sea water level. This water is returned through specially designed low head hydro turbines powering electrical generators. The device has been subject to 6 years of R&D at the Department of Civil Engineering of Aalborg University, involving the hydraulic performance such as geometric optimization for power capture and feasibility of the SSG-breakwater application. The issues under research led to close collaboration with Technical University of Munich (DE), for the turbine control and strategy; IKM Elektro for the operating procedures and generators (NO); WAVEenergy AS for the commercialization of the concept (NO); DNV for the insurance of the structure (DK); and Delta marine Consultants for the SSG-breakwater design (NL).

At the present stage of development of the SSG device, economical feasibility and reliability are at the first places on the ranking issues. The efficiency optimization is linked with the cost of the produced electricity. In the SSG device most of the optimization is done on the geometry as this has the biggest impact in the captured power and has the larger uncertainties. At the same time, the largest cost for the device is the structure itself and therefore the amount of concrete utilized for its construction. Prediction of wave loading is indeed influencing both the reliability of the device and the final cost of electricity.

The most promising application for the SSG device is into breakwaters for harbor protection. Aspects related to the construction have also being reviewed in this work. The research carried out on this application demonstrated the device is economically feasible and competitive to OWC devices with the same application, offering moreover additional improvements to the protection.

Finally it must be noticed that due to the relative young stage of development of the entire sector (at least 10 years behind the offshore wind sector) frameworks and regulations for wave energy development are not fully ready. The majority of the Companies involved are small and unable to undertake time consuming consents processes. This may be the case also for the Environmental Impact Assessment (EIA) process. For this reason a study aimed at the simplification of the EIA of WECs, with particular reference to the scooping process, has been concluded. Based on the results, the potential environmental impact of the SSG device has been preliminary assessed.