Ocean wave energy is considered to be one of the important potential renewable energy resources for sustainable development. Various wave energy converter technologies have been proposed to harvest the energy from ocean waves. This thesis is based on the linear generator wave energy converter developed at Uppsala University. The research in this thesis focuses on the foundation optimization and the power absorption optimization of the wave energy converters and on the wave climate modelling at the Lysekil wave converter test site. The foundation optimization study of the gravity-based foundation of the linear wave energy converter is based on statistical analysis of wave climate data measured at the Lysekil test site. The 25 years return extreme significant wave height and its associated mean zero-crossing period are chosen as the maximum wave for the maximum heave and surge forces evaluation. The power absorption optimization study on the linear generator wave energy converter is based on the wave climate at the Lysekil test site. A frequency-domain simplified numerical model is used with the power take-off damping coefficient chosen as the control parameter for optimizing the power absorption. The results show a large improvement with an optimized power take-off damping coefficient adjusted to the characteristics of the wave climate at the test site. The wave climate modelling studies are based on the wave climate data measured at the Lysekil test site. A new mixed distribution method is proposed for modelling the significant wave height. This method gives impressive goodness of fit with the measured wave data. A copula method is applied to the bivariate joint distribution of the significant wave height and the wave period. The results show an excellent goodness of fit for the Gumbel model. The general applicability of the proposed mixed-distribution method and the copula method are illustrated with wave climate data from four other sites. The results confirm the good performance of the mixed-distribution and the Gumbel copula model for the modelling of significant wave height and bivariate wave climate.

Cette thèse présente le développement d'un modèle numérique avancé, capable de simuler les interactions entre des vagues de surface de cambrure quelconque et des corps rigides immergés ayant des mouvements de grande amplitude. Fondé sur la théorie potentielle, il propose une résolution couplée de la dynamique vagues/structure par la méthode implicite de Van Daalen (1993), encore appelée méthode du potentiel d'accélération par Tanizawa (1995). La précision du modèle à deux dimensions est testée sur un ensemble d'applications impliquant le mouvement forcé ou libre d'un cylindre horizontal immergé, de section circulaire : diffraction par un cylindre fixe, radiation par un cylindre en mouvement forcé de grande amplitude, absorption des vagues par le cylindre de Bristol. Pour chaque application, les résultats numériques sont comparés à des résultats expérimentaux ou analytiques issus de la théorie linéaire, avec un bon accord en particulier pour les petites amplitudes de mouvement du cylindre et pour les vagues de faibles cambrures. La génération de vagues irrégulières et la prise en compte d'un second corps cylindrique immergé sont ensuite intégrées au modèle, et illustrées sur des applications pratiques avec des systèmes récupérateurs d'énergie des vagues simples. Enfin, le modèle est étendu en trois dimensions avec des premières applications au cas d'une sphère décrivant des mouvements de grande amplitude / This PhD is dedicated to the development of an advanced numerical model for simulating interactions between free surface waves of arbitrary steepness and rigid bodies in high amplitude motions. Based on potential theory, it solves the coupled dynamics of waves and structure with the implicit method by Van Daalen (1993), also named the acceleration potential method by Tanizawa (1995). The precision of this two-dimensional model is tested on a wide range of applications involving the forced motion or free motion of a submerged horizontal cylinder of circular cross-section : diffraction by a fixed cylinder, radiation by a cylinder in specified high amplitude motions, wave absorption by the Bristol cylinder. In each of these applications, numerical results are compared to experimental data or analytical solutions based on the linear wave theory, with a good agreement especially for small amplitude motions of the cylinder and small wave steepnesses. The irregular wave generation by a paddle and the possibility to add an extra circular cylinder are integrated in the model and illustrated on practical applications with simple wave energy converters. The model is finally extended to three dimensions, with preliminary results for a sphere in large amplitude heaving oscillations

Mediante a crescente necessidade de aumento na oferta de energia elétrica devido à constante elevação na demanda mundial, esta dissertação avalia o desempenho de um sistema conversor de energia de ondas marítimas em energia elétrica. O sistema em análise é o de coluna de água oscilante com turbina de dupla ação instalado na costa. Utiliza-se um modelo regular de ondas como perturbação à dinâmica de uma câmara semi-submersa gerando fluxo de ar através de uma turbina à ar de dupla ação. O sistema final é não linear e com parâmetros variantes no tempo. A dissertação investiga possibilidades para o aumento do rendimento da turbina em diferentes condições de mar através do método de simulação numérica. Após a modelagem física e matemática do sistema escolhido, inicia-se a síntese de um controlador proporcional derivativo para controle da pressão de ar na turbina em torno da pressão ideal de trabalho da mesma. A análise inclui o comparativo entre os resultados do sistema com e sem controlador e a avaliação de robustez utilizando ondas com amplitude variável. O trabalho apresenta ainda propostas de otimização do sistema para trabalhar em condições similares a região de Pecém no Brasil. Pelos resultados obtidos nas simulações, conclui-se que o rendimento e a robustez do sistema podem melhorar utilizando um sistema controlado. O rendimento do sistema poderá ainda ser otimizado para a região de instalação. / Facing the growing necessity in increasing the electrical energy offer due to the constant rise in worldwide demand, this work evaluates the performance of an ocean wave energy converter into electrical energy. The system under analysis is an oscillating water column with dual action turbine installed in a shore. A regular wave model is used as disturbance to the semi-submerged air chamber dynamic generating an air flow through the dual action air turbine. The final system is nonlinear and contains time varying parameters. This work investigates, through numerical simulation, possibilities to increase the turbine efficiency under different ocean conditions. After the physical and mathematical modeling, it is synthesized a proportional derivative controller to control the air pressure in the turbine around its ideal working pressure. The analysis of results includes a comparison between results obtained for the system with and without controller and a robustness evaluation with amplitude variation in ocean waves. The work also presents optimization proposals for the system working in conditions similar to the Pecém region in Brazil. By the results obtained with simulation, it is concluded that the efficiency and robustness were improved for the controlled system. It is observed that the efficiency can be optimized for the installation area.

O princípio operacional do dispositivo de galgamento consiste de uma estrutura que utiliza uma rampa para direcionar as ondas incidentes para o reservatório. A água armazenada retorna para o oceano após a passagem por uma turbina que está acoplada a um gerador de energia elétrica. O presente trabalho propõe dois estudos numéricos a respeito de um conversor de energia das ondas do mar do tipo galgamento. Para ambos os casos, o objetivo do estudo é a aplicação do método Design Construtal na definição da melhor forma para a rampa de modo a maximizar a massa de água que entra no reservatório, conduzindo a uma maior geração de energia elétrica. O grau de liberdade b/B, isto é, a razão entre a base superior e a base inferior da rampa trapezoidal, foi otimizado, mantendo-se fixos a área total do tanque de ondas, a área da rampa e as características da onda. Para a análise numérica do princípio de funcionamento deste dispositivo foi empregado um domínio computacional tridimensional (3D), gerado através do software GAMBIT, onde o conversor é acoplado a um tanque de ondas regulares. A solução das equações de conservação e a equação do transporte da fração volumétrica foi realizada com o código comercial de Dinâmica dos Fluidos Computacional FLUENT, que é baseado no Método de Volumes Finitos (MVF). Aplica-se o modelo multifásico Volume of Fluid (VOF) no tratamento da interação água-ar. Para o primeiro estudo, as características da onda regular empregada estavam em escala de laboratório. Os resultados mostraram que houve uma razão ótima (b/B)o = 0.43, que maximiza a quantidade de água que entra no reservatório para o caso estudado. Para ambos os casos, a razão ótima foi encontrada para o extremo inferior do grau de liberdade, além dos resultados apontarem um aumento significativo na massa admitida no reservatório e, por consequente, um maior aproveitamento das ondas incidentes. / The operational principle of an overtopping device consists of a structure which utilizes a ramp to direct incident waves to the reservoir. The stored water returns to the ocean after passing through a turbine that is coupled to an electric generator. This work proposes two numerical studies of a WEC of sea waves of the type overtopping. In both cases, the objective of the study is the application of Constructal Design method to define the best geometry of the ramp which maximizes the mass of water entering the reservoir, leading to increase the generation of electricity. The degree of freedom b/B, that is, the ratio between the upper base and the lower base of the trapezoidal ramp, has been optimized, keeping fixed the total area of the wave tank, the area of the ramp and the wave characteristics. For the numerical analysis of the working principle of this device it was used a three-dimensional computational domain (3D) generated by GAMBIT software where the device is inserted to a tank of regular waves. The solution of conservation equations and equation of transport of the volumetric fraction was carried out with the Commercial Code of Computational Fluid Dynamics FLUENT, which is based on Finite Volume Method (FVM). It was applied the multiphase model Volume of Fluid (VOF) in the treatment of the interaction water-air. For the first study, the characteristics of the employed regular wave were on a laboratory scale. The results showed that there were an optimal ratio (b/B)o = 0.43, which maximizes the amount of water entering the reservoir for the case study. For the second study, the characteristics of the regular wave were employed at actual scale and the results showed that there was an optimum ratio (b/B)o = 0.38, which maximizes the amount of water entering the reservoir for the case study. In both cases, the optimum ratio is found for the extreme lower of freedom of degree and the results showed a significant increase in the mass allowed in the reservoir and, consequently, larger use of the incident waves.

Cette thèse s’inscrit dans le cadre du 12ème appel à projet du Fonds Unique Interministériel (FUI) lancé par l’Etat au premier semestre 2011. Le projet « EM BILBOQUET » a été colabellisé par les pôles de compétitivité Mer Bretagne, Mer PACA et Tenerrdis. Il consiste en la réalisation d’un nouveau système de génération d’électricité issue du mouvement relatif entre deux corps flottants, mus par la houle. Dans cette thèse, nous nous sommes intéressés au contrôle optimal à appliquer sur la génératrice via les convertisseurs statiques, afin d’extraire le maximum d’énergie de la houle incidente. Dans un premier temps, nous avons établi les équations dynamiques régissant le comportement de la structure dans la houle en adoptant les hypothèses de la théorie potentielle. Pour ce faire, nous avons développé un code de calcul spécifique, basé sur une résolution du problème linéaire de tenue à la mer, par des méthodes dites semi-analytiques. Ce code de calcul permet de déterminer les coefficients hydrodynamiques nécessaires à l’écriture de l’équation dynamique dans le domaine fréquentiel, mais aussi dans le domaine temporel via une modification de la formulation de Cummins. Cette dernière nous permet ainsi, dans un second temps, de formuler le problème de maximisation de l’énergie récupérée comme un problème d’optimisation où la variable à optimiser est le couple résistant de la génératrice. Le problème est résolu en temps réel en adoptant une résolution par algorithme dit à horizon fuyant. / In this thesis, we perform a study on a self-reacting point absorber, project FUI 12 “EM BILBOQUET”, in order to optimise energy extraction from incoming waves. Main researches use seabed for providing reference to a floating body, called buoy. However, as it is well-known that ocean energy is greater far away from the shore, sea-depth becomes a constraint. In this thesis a damping plate attached to a spar keel is proposed to allow the floating body to react against it. Energy resulting from the relative motion between the two concentric bodies i.e. the buoy and the spar is harnessed by a rack-and-pinion, which drive a permanent magnet synchronous generator through a gearbox. In the first part of the thesis we have developed a wave-to-wire model i.e. a model of the whole electro-mechanical chain from sea to grid. To this purpose we have developed our own hydrodynamic code, based on linear potential theory and on a semianalytical approach, solving the seakeeping problem. The hydrodynamic coefficients obtained such as added mass, radiation damping, and wave excitation forces are required for solving the dynamic equation based on Cummins formulation. The second part of the thesis focuses on the self-reacting point-absorber optimal control strategy and the Model Predictive Control (MPC) formulation is proposed. Objective function attempting to optimise the power generation is directly formulated as an absorbed power maximisation problem and thus no optimal references, such as buoy and/or spar velocity, are required. However, rather than using the full-order WEC model in the optimisation problem, that can be time-consuming due to its high order, and also because of the linear assumptions, we propose the use of a “phenomenologically" one-body equivalent model derived from the Thévenin’s theorem.

Renewable energy sources are essential to our future, not only because they generally minimize harm to our environment but are also a relatively free source of energy that are available for generations to come. Wind and solar energy are proven sources of renewable energy, but both are highly variable. On the other hand, water wave energy is relatively persistent in locations around the world. Many researchers have tried to capture the energy of ocean waves, some were successful, but most were not. Harnessing wave energy is not a simple matter. One must design systems that can withstand the extreme forces of waves, the corrosive nature of salt water, and biofouling effects that can impact the system, while safely extracting energy from waves. This thesis presents the process followed in developing a new system to capture wave energy that has the potential to overcome many of the problems faced by other wave energy convertors (WEC). The concept of the design consists of a floating compliant structure that utilizes a mechanical system to harness water wave energy. The floating system can house several mechanical systems within the same structure, improving its power production and utilizing a greater area on the sea surface. The methodology uses linear wave theory to simulate different wave conditions to calculate the available energy to the system. This model provides estimates of the orbital motion of water particles which can be used to quantify the motions that such a system will undergo. The model can also be used to calculate the forces acting on the structure assuming rigid conditions. As with wind and solar power the wave energy greatly varies depending on the wave conditions, making the design of the structure much more difficult. The designed system must be capable of generating energy at low and high wave conditions and surviving extreme wave events.

Le secteur de l’énergie houlomotrice s’appuie fortement sur la modélisation mathématique et la simulation d’expériences physiques mettant en jeu les interactions entre les ondes et les corps. Dans ce travail, nous avons développé un modèle d’interaction de fidélité moyenne vague-corps pour la simulation de structures tronquées flottantes fonctionnant en mouvement vertical. Ce travail concerne l’ingénierie de l’énergie marine, pour des applications telles que les convertisseurs d’énergie de vague (WEC) à absorption ponctuelle, même si ses applications peuvent aussi être utilisées en ingénierie maritime et navale. Les motivations de ce travail reposent sur les méthodes standard actuelles pour décrire l’interaction corps-vague. Cellesci sont basées sur des modèles résolvant le flux de potentiel linéaire (LPF), du fait de leur grande efficacité. Cependant, les modèles LPF sont basés sur l’hypothèse de faible amplitude et ne peuvent pas répresenter les effets hydrodynamiques non linéaires, importants pour le WEC opérant dans la région de résonance ou dans les régions proches du rivage. En effet, il a été démontré que les modèles LFP prédisent de manière excessive la production de puissance, sauf si des coefficients de traînée sont calibrés. Plus récemment, des simulations Reynolds Averaged Navier-Stokes (RANS) ont été utilisées pour les WEC. RANS est un modèle complet et précis, mais très coûteux en calcul. Il n’est ni adapté à l’optimisation d’appareils uniques ni aux parcs énergétiques. Nous avons donc proposé un modèle de fidélité moyenne basé sur des équations de type Boussinesq, afin d’améliorer le compromis entre précision et efficacité. Les équations de type Boussinesq sont des modèles d’ondes intégrées en profondeur et ont été un outil d’ingénierie standard pour la simulation numérique de la propagation d’ondes non linéaires dans les eaux peu profondes et les zones côtières. Grâce à l’élimination de la dimension verticale, le modèle résultant est très efficace et évite la description temporelle de la limite entre la surface libre et l’air. Jiang (2001) a proposé un modèle de Boussinesq unifié, décomposant le problème en deux domaines : surface libre et corps. Dans cette méthode, le domaine du corps est également modélisé par une approche intégrée en profondeur - d’où le terme unifié. Récemment, Lannes (2016) avait analysé de manière rigoureuse une configuration similaire dans une équation non linéaire en eaux peu profondes, en déduisant une solution exacte et semi-analitique pour des corps en mouvement. Suivant la même approche, Godlewski et al. (2018) a élaboré un modèle de flux d’eau peu profonde encombrée. [...] Dans cette thèse, nous développons les résultats présentés par Eskilsson et al. (2016) et Bosi et al. (2019). Le modèle est étendu à deux dimensions horizontales. Le modèle 1D est vérifié à l’aide de solutions fabriquées et validé par rapport aux résultats publiés sur l’interaction vague-corps en 1D pour les pontons fixes et corps en mouvement de soulèvement forcé et libre. Les résultats des preuves de concept de la simulation de plusieurs corps sont présentés. Nous validons et vérifions le modèle 2D en suivant des étapes similaires. Enfin, nous mettons en oeuvre la technique de verrouillage, une méthode de contrôle de mouvement du corps pour améliorer la réponse au mouvement des vagues. Il est démontré que le modèle possède une excellente précision, qu’il est pertinent pour les applications d’ondes en interaction avec des dispositifs à énergie houlomotrice et qu’il peut être étendu pour simuler des cas plus complexes. / The wave energy sector relies heavily on mathematical modelling and simulation of the interactions between waves and floating bodies. In this work, we have developed a medium-fidelity wave-body interaction model for the simulation of truncated surface piercing structures operating in heave motion, such as point absorbers wave energy converters (WECs). The motivation of the work lies in the present approach to wave-body interaction. The standard approach is to use models based on linear potential flow (LPF). LPF models are based on the small amplitude/ small motion assumption and, while highly computational efficient, cannot account for nonlinear hydrodynamic effects (except for Morison-type drag). Nonlinear effects are particularly important for WEC operating in resonance, or in nearshore regions where wave transformations are expected. More recently, Reynolds Averaged Navier-Stokes (RANS) simulations have been employed for modelling WECs. RANS is a complete and accurate model but computationally very costly. At present RANS models are therefore unsuited for the optimization of single devices, not to mention energy farms. Thus, we propose a numerical model based built on Boussinesq-type equations to include wave-wave interaction as well as finite body motion in a computationally efficient formulation. Boussinesq-type equations are depth-integrated wave models and are standard engineering tool for numerical simulation of propagation of nonlinear wave in shallow water and coastal areas. Thanks to the elimination of the vertical dimension and the avoidance of a time-dependent computational the resulting model is very computational efficient. Jiang (Jiang, 2001) proposed a unified Boussinesq model, decomposing the problem into free surface and body domains. Notably, in Jiang’s methodology also the body domain is modeled by a depth-integrated approach –hence the term unified. As all models based on Boussinesq-type equations, the model is limited to shallow and intermediate depth regimes. We consider the Madsen and Sørensen model, an enhanced Boussinesq model, for the propagation of waves. We employ a spectral/hp finite element method (SEM) to discretize the governing equations. The continuous SEM is used inside each domain and flux-based coupling conditions are derived from the discontinuous Galerkin method. The use of SEM give support for the use of adaptive meshes for geometric flexibility and high-order accurate approximations makes the scheme computationally efficient. In this thesis, we present 1D results for the propagation and interaction of waves with floating structures. The 1D model is verified using manufactured solutions. The model is then validated against published results for wave-body interaction. The hydrostatic cases (forced motion and decay test) are compared to analytical and semi-analytical solutions (Lannes, 2017), while the non-hydrostatic tests (fixed pontoon and freely heaving bodies) are compared to RANS reference solutions. The model is easily extended to handle multiple bodies and a proof-of-concept result is presented. Finally, we implement the latching technique, a method to control the movement of the body such that the response to the wave movement is improved. The model is extended to two horizontal dimensions and verified and validated against manufactured solutions and RANS simulations. The model is found to have a good accuracy both in one and two dimensions and is relevant for applications of waves interacting with wave energy devices. The model can be extended to simulate more complex cases such as WEC farms/arrays or include power generation systems to the device.

Video monitoring of beaches is becoming the preferred method for observing changes to nearshore morphology. Consequently this work investigates a new technique for predicting the probability of inundation that is based on measuring runup variation using video. Runup is defined as the water-level elevation maxima on the foreshore relative to the still water level and the waterline is defined as the position where the MWL intersects the beach face. Tairua, and Pauanui Beaches, on the north east coast of the North Island of New Zealand, were used as the field site in this study and represent two very different beaches with the same incoming wave and meteorological conditions. Tairua is most frequently in an intermediate beach state, whereas Pauanui is usually flatter in nature. In order to rectify runup observations, an estimate of the runup elevation was needed (Z). This was estimated by measuring the variation of the waterline over a tidal cycle from time-averaged video images during a storm event and provided beach morphology statistics (i.e. beach slope (α) and beach intercept (b)) used in the rectification process where Z=aX+b. The maximum swash excursions were digitized from time-stacks, and rectified to provide run-up timeseries with duration 20 minutes. Field calibrations revealed a videoed waterline that was seaward of the surveyed waterline. Quantification of this error gave a vertical offset of 0.33m at Tairua and 0.25m at Pauanui. At Tairua, incident wave energy was dominant in the swash zone, and the runup distributions followed a Rayleigh distribution. At Pauanui, the flatter beach, the runup distributions were approximately bimodal due to the dominance of infragravity energy in the swash signal. The slope of the beach was a major control on the runup elevation; runup at Pauanui was directly affected by the deepwater wave height and the tide, while at Tairua there was no correlation. Overall, the results of the study indicate realistic runup measurements, over a wide range of time scales and, importantly, during storm events. However, comparisons of videoed runup and empirical runup formulae revealed larger deviations as the beach steepness increased. Furthur tests need to be carried out to see if this is a limitation of this technique, used to measure runup. The runup statistics are consistently higher at Tairua and suggests that swash runs up higher on steeper beaches. However, because of the characteristics of flatter beaches (such as high water tables and low drainage efficiencies) the impact of extreme runup elevations on such beaches are more critical in regards to erosion and/ or inundation. The coastal environment is of great importance to Māori. Damage to the coast and coastal waahi tapu (places of spiritual importance) caused by erosion and inundation, adversely affects the spiritual and cultural well-being of Māori. For this reason, a chapter was dedicated to investigating the practices used by Māori to protect and preserve the coasts in accordance with tikanga Māori (Māori protocols). Mimicking nature was and still is a practice used by Māori to restore the beaches after erosive events, and includes replanting native dune plants and using natural materials on the beaches to stabilize the dunes. Tapu and rahui (the power and influence of the gods) were imposed on communities to prohibit and prevent people from free access to either food resources or to a particular place, in order to protect people and/ or resources. Interpretations of Māori oral histories provide insights into past local hazards and inform about the safety and viability of certain activities within an area. Environmental indicators were used to identify and forecast extreme weather conditions locally. Māori knowledge of past hazards, and the coastal environment as a whole, is a valuable resource and provides a unique source of expertise that can contribute to current coastal hazards management plans in New Zealand and provide insights about the areas that may again be impacted by natural hazards.

Although oscillating water column type wave energy devices are nearing the stage of commercial exploitation, there is still much to be learnt about many facets of their hydrodynamic performance. This research uses the commercially available FLUENT computational fluid dynamics flow solver to model a complete OWC system in a two dimensional numerical wave tank. A key feature of the numerical modelling is the focus on the influence of the front wall geometry and in particular the effect of the front wall aperture shape on the hydrodynamic conversion efficiency. In order to validate the numerical modelling, a 1:12.5 scale experimental model has been tested in a wave tank under regular wave conditions. The effects of the front lip shape on the hydrodynamic efficiency are investigated both numerically and experimentally and the results compared. The results obtained show that with careful consideration of key modelling parameters as well as ensuring sufficient data resolution, there is good agreement between the two methods. The results of the testing have also illustrated that simple changes to the front wall aperture shape can provide marked improvements in the efficiency of energy capture for OWC type devices.

A wave energy converter has been constructed and its function and operational characteristics have been thoroughly investigated and published. The wave energy converter was installed in March of 2006 approximately two kilometers off the Swedish west coast in the proximity of the town Lysekil. Since then the converter has been submerged at the research site for over two and a half years and in operation during three time periods for a total of 12 months, the latest being during five months of 2008. Throughout this time the generated electricity has been transmitted to shore and operational data has been recorded. The wave energy converter and its connected electrical system has been continually upgraded and each of the three operational periods have investigated more advanced stages in the progression toward grid connection. The wave energy system has faced the challenges of the ocean and initial results and insights have been reached, most important being that the overall wave energy concept has been verified. Experiments have shown that slowly varying power generation from ocean waves is possible. Apart from the wave energy converter, three shorter studies have been performed. A sensor was designed for measuring the air gap width of the linear generator used in the wave energy converter. The sensor consists of an etched coil, a search coil, that functions passively through induction. Theory and experiment showed good agreement. The Swedish west coast wave climate has been studied in detail. The study used eight years of wave data from 13 sites in the Skagerrak and Kattegatt, and data from a wave measurement buoy located at the wave energy research site. The study resulted in scatter diagrams, hundred year extreme wave estimations, and a mapping of the energy flux in the area. The average energy flux was found to be approximately 5.2 kW/m in the offshore Skagerrak, 2.8 kW/m in the near shore Skagerrak, and 2.4 kW/m in the Kattegat. A method for evaluating renewable energy technologies in terms of economy and engineering solutions has been investigated. The match between the technologies and the fundamental physics of renewable energy sources can be given in terms of the technology’s utilization. It is argued that engineers should strive for a high utilization if competitive technologies are to be developed.