Publications

This is the eighth annual Progress Report to the Scottish Parliament required by Scottish Ministers under the Climate Change (Scotland) Act 2009. It assesses Scotland’s progress in achieving its legislated targets to reduce greenhouse gas emissions.<br/>Overall greenhouse gas emissions reduced by 3% in 2017 compared to a 10% fall in 2016. The fall was again led by the power sector due in large part to Scotland’s first full year of coal-free electricity generation. Recent performance in other sectors shows only incremental improvement at best and unless emissions reductions are delivered economy-wide Scotland is at risk of missing its new interim target of a 56% reduction in emissions by 2020. Setting a net-zero greenhouse gas emissions target for 2045 represents a step-change in ambition for Scotland. The Scottish Parliament’s 2030 target to reduce emissions by 75% will be extremely challenging to meet. It must be backed up by steps to drive meaningful emissions reductions immediately.<br/>Scotland’s Programme for Government 2019-20 alongside other recent policies sent a clear signal that the Scottish Government is taking its more ambitious targets seriously but there is much more to do.Scotland’s ability to deliver its net-zero target is contingent on action taken in the UK and vice versa.

In this report the Committee sets out how Northern Ireland can reduce its greenhouse gas emissions between now and 2030 in order to meet UK-wide climate change targets.

The report’s key findings are:

• Existing policies are not enough to deliver this reduction
• There are excellent opportunities to close this gap and go beyond 35%
• Meeting the cost-effective path to decarbonisation in Northern Ireland will require action across all sectors of the economy and a more joined-up approach

Overall Northern Ireland’s fair contribution to the UK’s fifth carbon budget requires emissions reductions of at least 35% against 1990 levels by 2030.

Hydrogen jet flames resulting from ignition of unintended releases can be extensive in length and pose significant radiation and impingement hazards. One possible mitigation strategy to reduce exposure to jet flames is to incorporate barriers around hydrogen storage and delivery equipment. While reducing the extent of unacceptable consequences the walls may introduce other hazards if not properly configured. This paper describes experiments carried out to characterize the effectiveness of different barrier wall configurations at reducing the hazards created by jet fires. The hazards that are evaluated are the generation of overpressure during ignition the thermal radiation produced by the jet flame and the effectiveness of the wall at deflecting the flame.<br/>The tests were conducted against a vertical wall (1-wall configuration) and two “3-wall” configurations that consisted of the same vertical wall with two side walls of the same dimensions angled at 135° and 90°. The hydrogen jet impinged on the center of the central wall in all cases. In terms of reducing the radiation heat flux behind the wall the 1-wall configuration performed best followed by the 3-wall 135° configuration and the 3-wall 90°. The reduced shielding efficiency of the three-wall configurations was probably due to the additional confinement created by the side walls that limited the escape of hot gases to the sides of the wall and forced the hot gases to travel over the top of the wall.<br/>The 3-wall barrier with 135° side walls exhibited the best overall performance. Overpressures produced on the release side of the wall were similar to those produced in the 1-wall configuration. The attenuation of overpressure and impulse behind the wall was comparable to that of the three-wall configuration with 90° side walls. The 3-wall 135° configuration’s ability to shield the back side of the wall from the heat flux emitted from the jet flame was comparable to the 1-wall and better than the 3-wall 90° configuration. The ratio of peak overpressure (from in front of the wall and from behind the wall) showed that the 3-wall 135° configuration and the 3-wall 90° configuration had a similar effectiveness. In terms of the pressure mitigation the 3-wall configurations performed significantly better than the 1-wall configuration

Hydrogen embrittlement (HE) has been extensively studied in bulk materials. However little is known about the role of H on the plastic deformation and fracture mechanisms of nanoscale materials such as nanowires. In this study molecular dynamics simulations are employed to study the influence of H segregation on the behavior of intergranular cracks in bicrystalline α-Fe nanowires. The results demonstrate that segregated H atoms have weak embrittling effects on the predicted ductile cracks along the GBs but favor the cleavage process of intergranular cracks in the theoretically brittle directions. Furthermore it is revealed that cyclic loading can promote the H accumulation into the GB region ahead of the crack tip and overcome crack trapping thus inducing a ductile-to-brittle transformation. This information will deepen our understanding on the experimentally-observed H-assisted brittle cleavage failure and have implications for designing new nanocrystalline materials with high resistance to HE.

The Committee’s report ‘The compatibility of UK onshore petroleum with meeting the UK’s carbon budgets’ is the result of a new duty under the Infrastructure Act 2015. This duty requires the CCC to advise the Secretary of State for Energy and Climate Change about the implications of exploitation of onshore petroleum including shale gas for meeting UK carbon budgets.<br/>The CCC’s report finds that the implications of UK shale gas exploitation for greenhouse gas emissions are subject to considerable uncertainty – from the size of any future industry to the potential emissions footprint of shale gas production. It also finds that exploitation of shale gas on a significant scale is not compatible with UK carbon budgets or the 2050 commitment to reduce emissions by at least 80% unless three tests are satisfied.

Fuel cell based micro-combined heat and power (CHP) units used for domestic applications can provide significant cost and environmental benefits for end users and contribute to the UK’s 2050 emissions target by reducing primary energy consumption in dwellings. Lately there has been increased interest in the development of systematic methods for the design of such systems and their smoother integration with domestic building services. Several models in the literature whether they use a simulation or an optimisation approach ignore the dwelling side of the system and optimise the efficiency or delivered power of the unit. However the design of the building services is linked to the choice of heating plant and its characteristics. Adding the dwelling’s energy demand and temperature constraints in a model can produce more general results that can optimise the whole system not only the micro-CHP unit. The fuel cell has various heat streams that can be harvested to satisfy heat demand in a dwelling and the design can vary depending on the proportion of heat needed from each heat stream to serve the energy demand. A mixed integer non-linear programming model (MINLP) that can handle multiple heat sources and demands is presented in this paper. The methodology utilises a process systems engineering approach. The model can provide a design that integrates the temperature and water flow constraints of a dwelling’s heating system with the heat streams within the fuel cell processes while optimising total CO₂ emissions. The model is demonstrated through different case studies that attempt to capture the variability of the housing stock. The predicted CO₂ emissions reduction compared to a conventionally designed building vary from 27% to 30% and the optimum capacity of the fuel cell ranges between 1.9 kW and 3.6 kW. This research represents a significant step towards an integrated fuel cell micro-CHP and dwelling design.

Hydrogen and renewable electricity-based microgrid is considered to be a promising way to reduce carbon emissions promote the consumption of renewable energies and improve the sustainability of the energy system. In view of the fact that the existing day-ahead optimal operation model ignores the uncertainties and fluctuations of renewable energies and loads a two-stage energy management model is proposed for the sustainable wind-PV-hydrogen-storage microgrid based on receding horizon optimization to eliminate the adverse effects of their uncertainties and fluctuations. In the first stage the day-ahead optimization is performed based on the predicted outpower of WT and PV the predicted demands of power and hydrogen loads. In the second stage the intra-day optimization is performed based on the actual data to trace the day-ahead operation schemes. Since the intra-day optimization can update the operation scheme based on the latest data of renewable energies and loads the proposed two-stage management model is effective in eliminating the uncertain factors and maintaining the stability of the whole system. Simulations show that the proposed two-stage energy management model is robust and effective in coordinating the operation of the wind-PV-hydrogen-storage microgrid and eliminating the uncertainties and fluctuations of WT PV and loads. In addition the battery storage can reduce the operation cost alleviate the fluctuations of the exchanged power with the power grid and improve the performance of the energy management model.

In the transition to a hydrogen economy it is likely that hydrogen will be used or stored in close proximity to other flammable fuels and gases. Accidents can occur that result in the release of two or more fuels such as hydrogen and natural gas that can mix and form a hazard. A series of five medium-scale semi-open-space deflagration experiments have been conducted with hydrogen natural gas and air mixtures. The natural gas consisted of 90% methane 6% ethane 3% propane and 1% butane by volume. Mixtures of hydrogen and natural gas were created with the hydrogen mole fraction in the fuel varying from 1.000 to 0.897 and the natural gas mole fraction varying from 0.000 to 0.103. The hydrogen and natural gas mixture was then released inside a 5.27-m³ thin plastic tent. The stoichiometric fuel-air mixtures were ignited with a 40-J spark located at the bottom center of the tent. Overpressure and impulse data were collected using pressure transducers located within the mixture volume and in the free field. Flame front time-of-arrival was measured using fast response thermocouples and infrared video. Flame speeds relative to a fixed observer were measured between 36.2 m/s and 19.7 m/s. Average peak overpressures were measured between 2.0 kPa and 0.3 kPa. The addition of natural gas inhibited the combustion when the hydrogen mole fraction was less than or equal to 0.949. For these mixtures there was a significant decrease in overpressures. When the hydrogen mole fraction in the fuel was between 0.999 and 0.990 the overpressures were slightly higher than for the case of hydrogen alone. This could be due to experimental scatter or there may be a slight enhancement of the combustion when a very small amount of natural gas was present. From a safety standpoint variation in overpressure was small and should have little effect on safety considerations.

Development of efficient and affordable photocatalysts is of great significance for energy production and environmental sustainability. Transition metal chalcogenides (TMCs) with particle sizes in the 1–100 nm have been used for various applications such as photocatalysis photovoltaic and energy storage due to their quantum confinement effect optoelectronic behavior and their stability. In particular TMCs and their heterostructures have great potential as an emerging inexpensive and sustainable alternative to metal-based catalysts for hydrogen evolution. Herein the methods used for the fabrication of TMCs characterization techniques employed and the different methods of solar hydrogen production by using different TMCs as photocatalyst are reviewed. This review provides a summary of TMC photocatalysts for hydrogen production.

We present results from hydrogen dispersion simulations from a pressurized reservoir at constant flow rate in the presence and absence of a wall. The dispersion simulations are performed using a commercial finite volume solver. Validation of the approach is discussed. Constant concentration envelopes corresponding to the 2% 4% and 15% hydrogen concentration in air are calculated for a subcritical vertical jet and for an equivalent subcritical horizontal jet from a high pressure reservoir. The consequences of ignition and the resulting overpressure are calculated for subcritical horizontal and vertical hydrogen jets and in the latter case compared to available experimental data.