Particulate number and NOx trade-off comparisons between HVO and mineral diesel in HD applications

The increase in worldwide greenhouse gas emissions and costs for fossil fuels are forcing fuel suppliers and engine manufacturers to consider more sustainable alternatives for powering internal combustion engines. One very promising equivalent to mineral diesel fuel is hydrotreated vegetable oil (HVO) as it is highly paraffinic and offers similar combustion characteristics. This fuel offer the potential of not requiring further engine hardware modification together with correspondingly lower exhaust gas emissions and better fuel consumption than mineral diesel. In this paper the spray and combustion characteristics of HVO and its blends are investigated and compared with mineral diesel (European standard). Evidence of the reported reductions in NOx emissions has proven contradictory with some researchers reporting large reductions, whilst others measured no differences. This paper reports the results from comparison of three different experimental tests methods using diesel/HVO binary fuel blends. The macroscopic spray characteristics have been investigated and quantified using a constant volume spray vessel. Engine performance and exhaust emissions have also been characterised using a HD diesel engine in its original configuration (mineral diesel fuel-ready) and then in a recalibrated configuration optimised for HVO fuel. The results show that the engine injection control and also the fuel quality can influence the formation of NOx and particulate matter significantly. In-particular a potential pilot injection proved highly influential upon whether NOx emissions were reduced or not. When optimising the fuel injection, a reduction in NOx emissions of up to 18% or reductions of PN of up to 42–66% were achieved with simultaneous savings in fuel consumption of 4.3%

Assessing the techno-economic viability of a trigeneration system integrating ammonia-fuelled solid oxide fuel cell

In recent years, ammonia has gained traction as a clean fuel alternative and a promising energy carrier. In this study, a trigeneration system fuelled by ammonia has been conceptualised, integrating a solid oxide fuel cell stack for power generation, a hot water unit for heating, and an NH3-H2O absorption chiller for cooling. The main objective of this study is to conduct a comprehensive techno-economic feasibility assessment of the proposed trigeneration system. The system's performance was analysed for a UK supermarket requiring electricity, heating, and cooling. A detailed sensitivity analysis was performed to investigate the influence of significant operating parameters, including current density, fuel utilisation factor, and cell temperature, on the system's performance. The system can deliver maximum power, heating, and cooling outputs of 357.6 kW, 257.9 kW, and 46.99 kW, respectively. The trigeneration system is projected to achieve its highest exergy efficiency at 60.94%, with a maximum fuel energy saving ratio of 47.67%. The lowest levelised cost of energy (LCOE) is estimated to be £0.1232 per kWh. This study's objective is also aligned with United Nations Sustainable Development Goal (SDG) No. 7, which aims to achieve “Affordable and Clean Energy”

The impact of disruptive powertrain technologies on energy consumption and carbon dioxide emissions from heavy-duty vehicles

Minimising tailpipe emissions and the decarbonisation of transport in a cost effective way remains a major objective for policymakers and vehicle manufacturers. Current trends are rapidly evolving but appear to be moving towards solutions in which vehicles which are increasingly electrified. As a result we will see a greater linkage between the wider energy system and the transportation sector resulting in a more complex and mutual dependency. At the same time, major investments into technological innovation across both sectors are yielding rapid advancements into on-board energy storage and more compact/lightweight on-board electricity generators. In the absence of sufficient technical data on such technology, holistic evaluations of the future transportation sector and its energy sources have not considered the impact of a new generation of innovation in propulsion technologies. In this paper, the potential impact of a number of novel powertrain technologies are evaluated and presented. The analysis considers heavy duty vehicles with conventional reciprocating engines powered by diesel and hydrogen, hybrid and battery electric vehicles and vehicles powered by hydrogen fuel cells, and free-piston engine generators (FPEGs). The benefits are compared for each technology to meet the expectations of representative medium and heavy-duty vehicle drivers. Analysis is presented in terms of vehicle type, vehicle duty cycle, fuel economy, greenhouse gas (GHG) emissions, impact on the vehicle etc.. The work shows that the underpinning energy vector and its primary energy source are the most significant factor for reducing primary energy consumption and net CO2 emissions. Indeed, while an HGV with a BEV powertrain offers no direct tailpipe emissions, it produces significantly worse lifecycle CO2 emissions than a conventional diesel powertrain. Even with a de-carbonised electricity system (100g CO2/kWh), CO2 emissions are similar to a conventional Diesel fuelled HGV. For the HGV sector, range is key to operator acceptability of new powertrain technologies. This analysis has shown that cumulative benefits of improved electrical powertrains, on-board storage, efficiency improvements and vehicle design in 2025 and 2035 mean that hydrogen and electric fuelled vehicles can be competitive on gravimetric and volumetric density. Overall, the work demonstrates that presently there is no common powertrain solution appropriate for all vehicle types but how subtle improvements at a vehicle component level can have significant impact on the design choices for the wider energy system

Levelised Cost of Storage for Pumped Heat Energy Storage in comparison with other energy storage technologies

Future electricity systems which plan to use large proportions of intermittent (e.g. wind, solar or tidal generation) or inflexible (e.g. nuclear, coal, etc.) electricity generation sources require an increasing scale-up of energy storage to match the supply with hourly, daily and seasonal electricity demand profiles. Evaluation of how to meet this scale of energy storage has predominantly been based on the deployment of a handful of technologies including batteries, Pumped Hydroelectricity Storage, Compressed Air Energy Storage and Power-to-Gas. However, for technical, confidentiality and data availability reasons the majority of such analyses have been unable to properly consider and have therefore neglected the potential of Pumped Heat Energy Storage, which has thus not been benchmarked or considered in a much detail relative to competitive solutions. This paper presents an economic analysis of a Pumped Heat Energy Storage system using data obtained during the development of the world’s first grid-scale demonstrator project. A Pumped Heat Energy Storage system stores electricity in the form of thermal energy using a proprietary reversible heat pump (engine) by compressing and expanding gas. Two thermal storage tanks are used to store heat at the temperature of the hot and cold gas. Using the Levelised Cost of Storage method, the cost of stored electricity of a demonstration plant proved to be between 2.7 and 5.0 €ct/kW h, depending on the assumptions considered. The Levelised Cost of Storage of Pumped Heat Energy Storage was then compared to other energy storage technologies at 100 MW and 400 MW h scales. The results show that Pumped Heat Energy Storage is cost-competitive with Compressed Air Energy Storage systems and may be even cost-competitive with Pumped Hydroelectricity Storage with the additional advantage of full flexibility for location. As with all other technologies, the Levelised Cost of Storage proved strongly dependent on the number of storage cycles per year. The low specific cost per storage capacity of Pumped Heat Energy Storage indicated that the technology could also be a valid option for long-term storage, even though it was designed for short-term operation. Based on the resulting Levelised Cost of Storage, Pumped Heat Energy Storage should be considered a cost-effective solution for electricity storage. However, the analysis did highlight that the Levelised Cost of Storage of a Pumped Heat Energy Storage system is sensitive to assumptions on capital expenditure and round trip efficiencies, emphasising a need for further empirical evidence at grid-scale and detailed cost analysis

Modelling of hydrogen blending into the UK natural gas network driven by a solid oxide fuel cell for electricity and district heating system

A thorough investigation of the thermodynamics and economic performance of a cogeneration system based on solid oxide fuel cells that provides heat and power to homes has been carried out in this study. Additionally, different percentages of green hydrogen have been blended with natural gas to examine the techno-economic performance of the suggested cogeneration system. The energy and exergy efficiency of the system rises steadily as the hydrogen blending percentage rises from 0% to 20%, then slightly drops at 50% H2 blending, and then rises steadily again until 100% H2 supply. The system's minimal levelised cost of energy was calculated to be 4.64 £/kWh for 100% H2. Artificial Neural Network (ANN) model was also used to further train a sizable quantity of data that was received from the simulation model. Heat, power, and levelised cost of energy estimates using the ANN model were found to be extremely accurate, with coefficients of determination of 0.99918, 0.99999, and 0.99888, respectively

The potential of decarbonising rice and wheat by incorporating carbon capture, utilisation and storage into fertiliser production

This paper aims to evaluate the reduction on greenhouse gas emissions in rice and wheat and their supply chains by incorporating carbon capture, utilisation, and storage into fertiliser production mainly from ammonia process, which is the section of fertiliser that produces the most carbon dioxide. Greenhouse gas emissions of these grains without carbon capture, utilisation and storage are provided from the results of life cycle assessment in the literatures. After that, a carbon dioxide emission from fertiliser production is quantified. The alternative considered for utilisation is enhanced oil recovery and it is compared with conventional way of oil production. The effect of carbon capture, utilisation, and storage in greenhouse gas reduction are presented in term of rice and wheat’s supply chains to make people conscious about the use and optimisation of food. The reduction of greenhouse gas is around 6-7% in rice supply chain e.g. rice milk, spoons of uncooked rice and 14-16% in wheat supply chain e.g. pasta, one slice of bread. Although the alternative with carbon dioxide storage demonstrates marginally higher greenhouse gas reduction, enhanced oil recovery may offer economic incentive from additional oil production that could reduce the cost of rice and wheat

Technoeconomic and environmental performance assessment of solid oxide fuel cell-based cogeneration system configurations

In this study, an innovative energy solution to fulfil the electricity and heating needs of a mixed community, including residences, a commercial building, and a small brewery has been investigated. The primary objective is to comprehensively analyse the technoeconomic, and environmental aspects of a UK-based solid oxide fuel cell (SOFC) energy hub designed for local-scale electricity and heating demands. This present study investigates two different configurations: (a) SOFC-based cogeneration and (b) SOFC-heat pump cogeneration configuration. These configurations are modelled to provide year-round electricity and heating for a local scale application and are evaluated using hydrogen and natural gas as fuels. A thorough environmental assessment is also conducted for SOFC and SOFC-heat pump system configurations fuelled by natural gas. The hydrogen fuelled SOFC-heat pump configuration outperforms other system configuration with energy efficiency of 96%. Meanwhile, the hydrogen-fuelled SOFC cogeneration system yields maximum exergy efficiency at 61.51%. The natural gas-powered SOFC-heat pump cogeneration system yields the lowest levelized cost of energy (LCOE) at 0.1603 £/kWh, in comparison to the higher LCOE of 0.213 £/kWh for the alkaline hydrogen-fuelled system. The natural gas-fuelled SOFC system emits 0.3352 kg/kWh of CO2, with even lower emissions of 0.275 kg/kWh for the SOFC-heat pump system configuration

Techno-economic analysis of solid oxide fuel cell-based energy systems for decarbonising residential power and heat in the United Kingdom

This study examines the feasibility of using hydrogen as a clean energy source for residential consumers in the UK through a low-carbon energy hub. Two cases were compared: a solid oxide fuel cell (SOFC) integrated combined heat and power (CHP) system fuelled by natural gas and hydrogen; and a SOFC–heat pump (HP) integrated CHP system fuelled by natural gas and hydrogen. The study used the actual electricity and heating demands of a UK cluster to model the CHP systems. The results indicate that the SOFC-based CHP system with hydrogen as fuel is more energy-efficient than the natural gas-fuelled system, with energetic efficiencies of 92.12% and 66.98%, respectively. The study also found that the system incorporating a heat pump is more economically viable, regardless of the fuel source, with the hydrogen-powered system equipped with a heat pump having a levelised cost of energy (LCOE) of 0.2984 £ per kW h. The study also evaluated the environmental impact of the natural gas-powered SOFC and SOFC–HP systems, with estimated levelised CO2 emissions of 0.308 kg per kW h and 0.213 kg per kW h, respectively. The study's findings provide insights into the potential of hydrogen as a cleaner energy source for residential consumers in the UK and highlight the importance of exploring low-carbon energy alternatives

The development and testing of a free-piston engine generator for hybrid electric vehicle applications

In this work, we present some of the first experimental results along with simulation results obtained in developing and testing a novel dual-piston free-piston engine generator (FPEG), designed for electric- vehicle (EV) range-extender or hybrid powertrain applications. The benefits of a high-efficiency, compact and lightweight design of the proposed range-extender are presented. The technical details and experimental set-up of a two-cylinder prototype and its instrumentation are also outlined. Results are presented for simulation and recent test programmes carried out across both 2-stroke and 4-stroke operational modes. The methods associated with engine control are detailed alongside key post-processed engine characteristics

Demonstration system of pumped heat energy storage (PHES) and its round-trip efficiency

Among the known energy storage technologies aiming to increase the efficiency and stability of power grids, Pumped Heat Energy Storage (PHES) is considered by many as a promising candidate because of its flexibility, potential for scale-up and low cost per energy storage unit. Whilst there are numerous demonstration systems under development, as it stands the only PHES demonstration system to be realised at scale is located in Hampshire, UK. This paper aims to present the results and analysis obtained from its commissioning and testing as part of an on-going study. The system was designed to offer a nominal power size of 150 kWe and energy storage capacity of 600 kWhe for an 8-hour storage cycle. This work presents evidence of the system Round-trip efficiency (RTE), which is considered as a fundamental performance metric for large-scale energy storage technologies. Recorded Pressure-Volume (P-V) measurements from recent heat pump/engine testing at part-load offers useful insight in terms of overall performance. Models are also developed to simulate the system to finally predict the performance at full-load conditions. The system and principle of operation are described first, followed by mathematical modelling outlining heat transfer mechanism and associated key losses involved in thermodynamic processes within components, and finally results are presented and compared at different operating conditions using different working gases. The results show good agreement with earlier studies, which indicate that expected electricity-to-electricity RTE is quite comparable to other mature technologies such as Pumped Hydropower Storage and Compressed Air Energy Storage. The cyclic operation of the system is also discussed. One-off storage cycle results in lower RTEs compared to a load-levelling cyclic operation where the efficiency is significantly improved due to stable packed-bed behaviour and better utilisation after an initial transient state