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The current literature on solid oxide fuel cell and internal combustion engine (SOFC-ICE) integration is focused on the application of advanced combustion technologies operating as bottoming cycles to generate a small load share. This integration approach can pose challenges for ships such as restricted dynamic capabilities and large space and weight requirements. Furthermore, the potential of SOFC-ICE integration for marine power generation has not been explored. Consequently, the current work proposes a novel approach of SOFC-ICE integration for maritime applications, which allows for high-efficiency power generation while the SOFC anode-off gas (AOG) is blended with natural gas (NG) and combusted in a marine spark-ignited (SI) engine for combined power generation. The objective of this paper is to investigate the potential of the proposed SOFC-ICE integration approach with respect to system efficiency, emissions, load sharing, space and weight considerations and load response. In this work, a verified zero-dimensional (0-D) SOFC model, engine experiments and a validated AOG-NG mean value engine model is used. The study found that the SOFC-ICE integration, with a 67–33 power split at 750 kWe power output, yielded the highest efficiency improvement of 8.3% over a conventional marine natural gas engine. Simulation results showed that promising improvements in efficiency of 5.2%, UHC and NOx reductions of about 30% and CO2 reductions of about 12% can be achieved from a 33–67 SOFC-ICE power split with comparatively much smaller increments in size and weight of 1.7 times. Furthermore, the study concluded that in the proposed SOFC-ICE system for maritime applications, a power split that favours the ICE would significantly improve the dynamic capabilities of the combined system and that the possible sudden and large load changes can be met by the ICE.

The concern for climate change and energy consumption has increased the demand for renewable energy production considerably. Marine energy sources attract attention because of their high energy den ...

The exploitation of ocean energy is currently recognized as an abundant, geographically diverse and renewable energy source that could benefit European citizens by increasing energy independence, enhancing economic growth, creating jobs, allowing decarbonization or serving as a complement to other renewable sources within the global energy mix. Of the various types of ocean energy (wave, tidal, offshore wind, salinity gradient and thermal gradient), this paper is focused on technologies with which to harness the energy from ocean currents. This energy will have considerable possibilities in the future thanks to its high predictability and its enormous potential for the production of electricity. Most of the review papers concerning tidal energy systems are focused on engineering topics. However, there continues to be limited information as regards other aspects, such as those of an economical, social, political, legislative and environmental nature which, together with their interrelationships, need to be dealt with as a whole in order to detect the key drivers that could affect the success or failure of making tidal energy technologies marketable. The objective of this review paper is to address this gap by providing a detailed strategic analysis based on the most up-to-date literature, reports and guidelines. The paper discusses the different disciplines of which the PESTEL analysis (political, economical, social, technological, environmental and legal) is composed and provides different strategies/recommendations through which to mitigate many of the risks identified in order to facilitate the successful development of these technologies and bring them onto the market. Finally, some recent advances in tidal technologies developed by our research group (GIT-ERM) are also highlighted in the technological part of this paper.

As the technology of hydrokinetic tidal energy conversion looks to exploit smaller markets in the wider ‘blue economy’, innovation is still required to ensure cost competitiveness with other energy sources. A typical assumption of existing techno-economic models of tidal energy converter (TEC) arrays is that TECs positioned to minimise negative hydrodynamic interactions will maximise economic return. That the number of TECs within an array should be chosen to maximise the annual energy production, follows from this assumption. To examine the validity of these assertions for small, area-constrained arrays, a hypothetical model of the relationship of levelised cost of energy (LCOE) to the mean mechanical annual energy production (MMAEP) is developed. The model exhibits three classes of behaviour, determined by the rate of energy lost to interactions as TECs are added to an optimally positioned array; significantly, only one class has greatest MMAEP corresponding to lowest LCOE. To test this model, a contemporary optimisation algorithm is added to the advanced ocean energy techno-economic simulation tool ‘DTOcean’ and applied to arrays of TECs constrained by a 2 ha deployment area. It is shown that the hypothetical LCOE model accurately describes the DTOcean results up to and including 12 TECs deployed. At 13 TECs deployed, the level of TEC interaction increases dramatically, invalidating the hypothetical model. Notably, however, the LCOE is shown to reduce significantly by allowing negative interactions between TECs, reducing by 47.8% from the best non-interacting array. Thus, subject to an improved understanding of the relationship between the environment, TEC reliability and costs, the results indicate that allowing negative interactions between TECs may increase the economically extractable resource of small area-constrained tidal energy sites.

Reducing local and global emissions is one of the drivers behind the promotion of renewable energy technologies (RETs). Some RET projects (e.g. solar, marine power, and some biomass and wind) usually require supplemental income from carbon credits in order to make them economically viable. This paper presents the mathematical development of nodal marginal CO2 emission metrics for hydrothermal systems. These metrics are obtained from optimal power flow and hydrothermal dispatch models considering hydro uncertainty. The proposed model allows a more accurate assessment of the emission reduction effect of RET projects and the provision of efficient carbon signals to the system. Modeling of hydro reservoirs and intertemporal constraints also allows incorporating the emission mitigation potential of water storage. The concepts of marginal CO2 emissions for hydrothermal systems are first exemplified using a small test system, and then simulations on a real hydrothermal system illustrate how these metrics can inform investment and operational decisions. Theoretical and simulation results show that transmission and hydro storage constraints neglect may provide wrong signals for RET investors, missing the incentives to install in areas where the potential for emissions reduction is higher (where renewable energy displaces a larger amount of coal or diesel). Policy makers can use the proposed model to assess the cost-effectiveness of emission reduction policies.

In a tidal power plant the most important devices are the tidal current turbines that harvest the kinetic energy contained in the tide and convert it into electricity. The number of turbines to install, their spatial configuration, and the connection of submarine cables are critical aspects in the development of marine energy projects. Here, we present a mixed-integer programming methodology to design tidal current farms considering both cost and benefits. We propose a model that solves, concurrently, the turbine’s locations and cable infrastructure by computing the number, locations, submarine connections of tidal turbines, and the tidal current farm’s overall capacity. The proposed model considers location-based costs, including cable routing and loss from wake effect and electrical transmission, to maximize the project’s economic viability. We demonstrate the methodology’s utility by determining the optimal turbines’ configuration in a real-life case study in the Chacao Chanel, Chile. Finally, practitioners can easily implement our methodology using any standard off-the-shelf mixed-integer programming software to evaluate their tidal current farm projects.

The momentum towards reduction of greenhouse gas emissions by reduced use of conventional source in marine power networks as well as significant development of renewable energy resources (RRs) have been the motivating factors for inclusion RRs in hybrid maritime microgrid system (HMμGS) and investigation of consequent frequent control mechanism. This article presents an approach of load frequency control in an independent HMμGS consisting of wind driven generation (WDG), Archimedes wave power generation (AWPG), marine biodiesel generator (MBG), solid-oxide fuel cell (SOFC) energy units, heat pump (HP) and freezer (FZR). The stability of the HMμGS model have been evaluated through the rigorous tests considering non-availability of renewable resources, concurrent random generation of AWPG, load demand, real recorded data of WDG. Comparative performance of several controllers such as PID, PID with filter (PIDN) and PI-(1 + PD) controller are presented with their parameters optimized using genetic algorithmic technique (GA), particle swarm technique (PSO), firefly algorithmic technique (FA), cultural algorithmic technique (CA) and the recent metaheuristic grasshopper algorithmic technique (GOA). The proposed frequency control strategy of HMμGS model is benchmarked by comparative statistical assessment and decision indicators. Finally, sensitivity assessment of GOA tuned PI-(1 + PD) controller under uncertain parametric variations such as; variation of WDG gain, droop factor (R), inertia constant (M) and loading without reoptimizing the optimal base condition values is conducted as an evidence of the sturdiness of the proposed frequency control strategy. The analysis of the results shows that the proposed GOA optimized PI-(1 + PD) control strategy perform much better than other control schemes.

The European Union has a target to reduce greenhouse gas emissions to 80% below 1990 levels by 2050 to keep global warming within 2 °C relative to pre-industrial levels. The more recent Paris climate agreement has a more ambitious target of limiting the temperature rise to well below 2 °C and the EU ambition is growing to become climate-neutral by 2050. This research explores decarbonization options using an innovative analytical approach that combines energy systems analysis and marginal abatement cost curves (MACCs). System-wide MACCs are derived using scenario ensembles from Irish TIMES energy systems model. Decomposition analysis is then used to associate decarbonization options with carbon abatement costs. In addition, energy systems analysis is carried out on the underlying scenario ensembles that are used to generate the MACCs to capture more technological details and to reflect interactions among technologies. The results show that MACCs are highly dependent on model assumptions and the availabilities of bioenergy and carbon capture and storage (CCS) technologies play critical roles. The paper also shows how key mitigation measures can be ranked and classified into categories of resilient (wind energy, CCS, electric vehicles, biofuels), tipping-point (electrifying building heating, biomass plants), and niche (ocean energy) technologies.

In many remote areas, expensive fossil fuels such as diesel are used to meet local electricity demand. However, their environmental impact is significant. Consequently, some of these areas have started to use hybrid systems that combine renewable energy sources and fossil fuel generation, such as wind-diesel systems, although wind is not feasible in some remote locations and fossil fuels remain the only resource in these areas. Fortunately, offshore renewable energy sources are available in many remote areas close to the ocean. In order to understand the feasibility of using offshore renewables in remote oceanic areas, we recently conducted a systematic study by developing an integrated model. This model includes a supply module, demand module, environmental impact module, and integrating module. Using this model, we mainly study the reduction in emissions resulting from offshore renewable energy penetration in local energy systems. In this article, we present this integrated model and an example study of tidal energy in the Southern Alaska community of Elfin Cove, which relies on diesel fuel for all of its electricity requirements. With 56 kW of tidal power penetrating the energy system, we found that almost 12,000 gallons of diesel fuel are displaced per year. This results in an annual emissions reduction of almost 244,000 lb CO 2 and about 1400 lb CO, as well as considerable reductions of PM-10, NO x , and SO x . The newly developed integrated model is expected to be used to analyze other aspects of tidal energy (and offshore renewable energy in general) in remote areas. For example, since the electricity demand in some remote areas varies significantly throughout the year, we recommend that tidal power should be used with a storage system.

Pacific Island Countries (PICs) have a huge renewable energy potential to meet their energy needs. Limited resources are available on land; however, large amount of ocean energy is available and can be exploited for power generation. PICs have more sea-area than land-area. Tidal current energy is very predictable and large amount of tidal current energy can be extracted using tidal current energy converters. A 10 m diameter, 3-bladed horizontal axis tidal current turbine (HATCT) is designed in this work. Hydrofoils were designed for different blade location; they are named as HF10XX. The hydrodynamic characteristics of the hydrofoils were analyzed. A thick hydrofoil with a maximum thickness of 24% and a maximum camber of 10% was designed for the root region. The maximum thickness of hydrofoils was varied linearly from the root to the tip for easier surface merging. For the tip region, a thinner hydrofoil of maximum thickness 16% and maximum chamber 10% was designed. It was ensured that the designed hydrofoils do not experience cavitation during the expected operating conditions. The characteristics of the HF10XX hydrofoils were compared with other commonly used hydrofoils. The blade chord and twist distributions were optimized using BEM theory. The theoretical power output and the efficiency of the rotor were also obtained. The maximum power at the rated current of 2 m/s is 150 kW and the maximum efficiency is 47.5%. The designed rotor is found to have good efficiency at current speeds of 1–3 m/s. This rotor has better performance than some other rotors designed for HATCT.

The energy in flowing river streams, tidal currents or other artificial water channels is being considered as viable source of renewable power. Hydrokinetic conversion systems, albeit mostly at its early stage of development, may appear suitable in harnessing energy from such renewable resources. A number of resource quantization and demonstrations have been conducted throughout the world and it is believed that both in-land water resources and offshore ocean energy sector will benefit from this technology. In this paper, starting with a set of basic definitions pertaining to this technology, a review of the existing and upcoming conversion schemes, and their fields of applications are outlined. Based on a comprehensive survey of various hydrokinetic systems reported to date, general trends in system design, duct augmentation, and placement methods are deduced. A detailed assessment of various turbine systems (horizontal and vertical axis), along with their classification and qualitative comparison, is presented. In addition, the progression of technological advancements tracing several decades of R&D efforts are highlighted.

The global attention has always been focussed on the adverse environmental impacts of conventional energy sources. In contrast nonconventional energy sources, particularly the renewable ones, have enjoyed a ‘clean’ image vis a vis environmental impacts. The only major exception to this general trend has been large hydropower projects; experience has taught us that they can be disastrous for the environment. The belief now is that minihydel and microhydel projects are harmless alternatives. But are renewable energy sources really as benign as is widely believed? The present essay addresses this question in the background of Lovin's classical paradigm, which had postulated the hard (malignant) and soft (benign) energy concepts in the first place. It critically evaluates the environmental impacts of major renewable energy sources. It then comes up with the broad conclusion that renewable energy sources are not the panacea they are popularly perceived to be; indeed in some cases their adverse environmental impacts can be as strongly negative as the impacts of conventional energy sources. The paper also dwells on the steps we need to take so that we can utilize renewable energy sources without facing environmental backlashes of the type we got from hydropower projects.

The integrated Severn barrage scheme could provide more than 8% of the current electricity requirements of England and Wales. The project would be well within the limits of current technology, cost slightly in excess of £1010, with a construction period approaching 10 years. Electricity could be generated from the tidal aspect of the scheme at 6·0 p/kWh at an 8% discount rate taken over the 120 year technical lifetime of the system (or ∼8·3 p/kWh at an 11% discount rate taken over a 40 year period). Electricity derived from the wind and wave energy harnessing-systems could be generated at between 4·4 and 8·8 p/kWh at an 11% discount rate over the 25 year lifetime of the systems. The simple pay-backs of the various schemes are wind ∼7 years; wave ∼10 years; and tidal ∼14 years, i.e. all well within the respective economic lifetimes of the systems. The inclusion of a public road along the top of the barrage would not only prove a national asset but also a source of income. There are numerous additional regional/national benefits (e.g. increased tourism, flood protection, additional employment, improved economy, etc.) associated with the construction and running of the barrage that should be considered when determining what Government assistance should be provided to encourage private financial investment in this desirable part of our national infrastructure. Once constructed, the barrage would be generating cheap, clean electricity for most of the next century.

As devices move from full-scale prototype to commercial installations, it is important that developers have detailed knowledge of the tidal energy resource. Therefore, the spatial distribution of the tidal currents over the northwest European shelf seas has been examined to improve understanding of the tidal-stream energy resource. Using a three-dimensional hydrodynamic model (ROMS) at ∼1 km spatial resolution, and applying device characteristics of the Seagen-S turbine, we show that the ratio of the amplitudes of the M2 and S2 tidal currents can lead to significant variability in annual practical power generation – variability that is not accounted for when considering only the mean peak spring tidal velocities, as is generally the case in resource feasibility studies. In addition, we show that diurnal inequalities (governed by K1 and O1 tidal constituents) and tidal asymmetries (governed by the relationship between M2 and its compound tide M4) over the northwest European shelf seas can further affect power generation at potential high-energy sites. Based on these variabilities, the spatial distribution of the tidal-stream ‘capacity factor’ has been calculated. We find that mean peak spring tidal velocities can under-estimate the resource by up to 25%, and that annual practical power generation can vary by ∼15% for regions experiencing similar mean peak spring tidal velocities, due to the influence of other tidal constituents. Therefore, even preliminary resource assessments should be based on annual average power density, rather than peak spring tidal velocity.

highlights � Waves are frequently aligned at an oblique angle to the tidal current. � Wave angle must be considered for realistic oceanographic conditions. � Waves have a significant impact on the tidal stream energy resource. � The net tidal resource is reduced by � 10% per metre wave height increase. abstract When selecting suitable sites for tidal stream energy arrays a wide range of factors must be considered, from the magnitude of the tidal stream resource, to realistic oceanographic conditions. Previous compu- tational and laboratory-scale investigations into the impact of waves upon tidal turbines (such as turbine blade loadings) and turbine arrays (such as array configuration) typically assume that waves propagate ''inline'' to the tidal current (waves following or waves opposing the tidal current with a 20 tolerance limit). We investigated the wave climate at typical tidal stream energy sites across the British Isles. The wave climate was simulated at 18 sites using a 7-year (2005-2011) SWAN wave model simulation of the northwest European shelf seas. The principal semi-diurnal lunar constituent (M2) was also esti- mated at these sites using the three-dimensional ROMS tidal model. A significant proportion of the wave climate (between 49% and 93% of the time), including extreme wave events (>10 m wave heights), was found to be propagating in a direction which was ''oblique'' to the major axis of tidal flow (i.e. waves which propagate at an angle to the tidal current with a 20 tolerance limit) at all 18 selected sites. Fur- thermore, the average ''inline'' wave climate was 2.25 m less in height and 2 s less in wave period in com- parison to the oblique wave climate. To understand the direct effect of waves upon the tidal stream resource, the dynamically wave-tide coupled COAWST modelling system was applied to an idealized headland case study, which represented the typical tide and wave conditions expected at first generation tidal stream energy sites. Waves were found to alter the simulated tidal velocity profile, which, because tidal stream power is proportional to velocity cubed, reduced the theoretical resource by 10% for every metre increase in wave height (R