Solar power is by far the most abundant renewable energy source. However, at present its use is limited by the high cost of solar cells, so that we continue to obtain most of our power from fossil fuels. Polymer (plastic) solar cells are an exciting research field that aims to address this problem, as polymer solar cells could be made by simple manufacturing processes such as roll to roll coating. The result would be much lower cost solar cells, with much lower energy of production. Most research to date has focussed on the efficiency of such solar cells, and good progress has been made, leading to efficiencies approximately two thirds of commercial amorphous silicon solar cells.In this proposal we address the most important remaining issue, namely understanding and enhancing the lifetime of polymer solar cells. To do this we will combine advanced photophysical, morphological and chemical analysis of solar cells before, during and after operation to gain new insight into the factors controlling degradation of such cells. This will provide a solid foundation for developing strategies for extending the solar cell lifetime in the later part of the project.The operation of polymer solar cells depends critically on the nanometre scale arrangement of the materials, so we will use sophisticated electron tomography techniques to study the nanoscale morphology and how it changes with device operation. This will be complemented by optical and electronic measurements performed in-situ on operating solar cells. A further innovation will be to make nanoscale perforation of an encapsulation layer and combine it with electron beam techniques to study local degradation with nanometre resolution. This challenging programme requires collaboration between world-leading research groups in St Andrews, Changchun, and Glasgow to access the range of expertise and facilities to make major progress, and will lead to a new UK-China collaboration.

The UK is planning to make massive investments in offshore wind farms which will result in several fleets of similar wind turbines being installed around the UK coastline. The economic case for these wind turbines assumes a very high technical availability, which means simply that the turbines have to be working and ready to generate electricity for nearly all of the time. Not achieving this availability could well result in large economic losses. Unfortunately there is relatively little operational experience of offshore systems on which to base the estimates used. The systems may turn out to behave in unexpected ways by failing earlier than expected, or by proving more difficult to maintain. Even well-known systems can behave differently when used in new environments, which is why reliability databases often indicate ranges of failure behaviour rather than single number estimates. Availability is difficult to model because, in addition to the unknown impact of different environments, there is often a period of adjustment in which operators and manufacturers adapt their processes and systems to the new situation, leading to the potential for availability growth. However, with a new fleet of turbines there is also an aging process as they all grow older together which could lead to lower availability. The economic case for offshore systems depends a lot on whether high enough availability can be achieved, particularly in the early years of operation which are important for paying back the investment costs. This project looks at the degree of uncertainty there is in availability estimates for offshore wind turbines. This uncertainty is not one that averages out when there are a large number of turbines, because it has a systematic affect across all the turbines in a wind farm and therefore leads to corresponding uncertainty in the overall availability across the wind farm. This type of uncertainty is often called state-of-knowledge uncertainty and only gets reduced by collecting data over the longer term. Even if we are not yet able to collect operational data, we can still gain an understanding of the sources of state-of-knowledge uncertainty. Mathematical models can help us understand how different sources of uncertainty affect the uncertainty about availability, and to find out which ones we should be most concerned about. That, in turn, will help researchers to focus their energies on resolving the issues that ultimately have the biggest impact.In this project, operations researchers will work together with engineers and other researchers in the renewables sector, in order to build credible mathematical models to help answer these questions. Doing that requires the development of new mathematics, particularly in the way we represent how uncertainties are affected by different environmental and engineering aspects. It requires us to find better ways of getting information from experts into a form that we can use in the mathematical models, and it also requires us to find new ways of running the models on a computer.

The importance and urgency of reducing carbon dioxide emissions has received much publicity. Electricity generation is responsible for 38% of carbon emissions world wide. Of all sources of global warming electricity generation is probably, technologically, the most easily replaced by carbon free sources. Electricity from sunlight using the photo-voltaic effect, which we will refer to as solar PV, was very much a niche application as little as 15 years ago. However in the last decade silicon solar PV technology has developed with astonishing speed so that today it is the cheapest form of electricity generation in most countries within 45 degrees of the equator. Equally importantly the cost of manufacture is decreasing by 24% for each doubling of production volume, much faster than most products. At the moment Solar PV provides only 2.6% of the world's electricity (in kWh) although a higher percentage in some countries (eg 7.9% in Germany, 5.4% in India). There are a number of factors which delay the take up of this technology. The biggest difficulty is intermittency in countries like the UK where peak load does not match peak solar output necessitating pumped storage hydro or other rapid start up generation which adds to the cost. In tropical and sub-tropical countries solar generation matches the load much better and it is these countries in which electricity demand is increasing most rapidly. However in general there is a reluctance to invest in Solar which in part is due to Solar being regarded as an unproven technology and questions regarding long term reliability of a capital intensive system with a costing based on a projected life of >25 years. It is well known that silicon solar cells degrade. There are two commercially important mechanisms. One is due to a reaction involving boron and oxygen which happens very quickly reducing the efficiency by ~2% in the first 24 hours of operation. This is well enough understood for specialists to be on the way to developing ways of minimising the effect and demonstrating stability. The other mechanism is called "light and elevated temperature degradation" (LeTID). It takes months or sometimes years to produce a degradation of between 2 and 5%. The higher the light intensity and the higher the temperature the faster the degradation although there are large variations between different materials and solar cell designs which are not at all understood despite much behavioural data. The aims of this project are to develop a fundamental understanding of the degradation mechanism, to test proposed methodologies for reducing or eliminating LeTID and to use our understanding of the degradation mechanisms involved to develop meaningful accelerated life tests. Experimental work will be done in Manchester using test devices fabricated by us in Manchester and by the University of New South Wales (Australia). The prime techniques used will be optical, chemical and electrical measurements in Manchester and the Australian National University (Canberra) supported by modelling work at the University of Aveiro (Portugal). These will include lifetime spectroscopy, Deep Level Transient Spectroscopy and variants, admittance spectroscopy, low temperature photo-luminescence, time resolved photo-luminescence, Raman spectroscopy, hydrogen measurements and Secondary Ion Mass Spectroscopy. Materials and devices samples will be supplied by two manufactures active in the silicon solar field.

In order to mitigate the effects of climate change, governments, private companies and individual citizens are taking action to reduce emissions of greenhouse gases (GHGs). Our project will provide new information that can be used to better evaluate the change in emissions that result from these actions. We will help the UK government track the effectiveness of emissions reductions policies that have been implemented to meet the targets laid out in the Climate Change Act (2008), which mandates that GHG emissions are reduced by 80% below 1990 levels by 2050. The UK has played a major part in recent scientific and technological advances in emissions reporting and evaluation. Its GHG emission inventory, which is compiled based on data relating to human activities and rates of emission from each activity, is world-leading. Furthermore, the UK is one of only two countries that regularly submits a second estimate of emissions, those derived from atmospheric measurements, as part of its annual United Nations Framework Convention on Climate Change (UNFCCC) submission. This second "top-down" estimate can be used to assess where uncertainties lie in the inventory and where further development is needed. However, limitations exist in our scientific knowledge and in our technical capabilities that prevent the UK, or any other country, from further improving its emissions reports through the incorporation of atmospheric data. Through the NERC Greenhouse Gas & Emissions Feedback programme, which ended in 2017, we demonstrated the ability to quantify the UK's net national GHG fluxes using atmospheric observations. However, we have not yet been able to separately estimate fossil fuel and biospheric carbon dioxide sources and sinks, or determine the major sectors driving changes in the UK's methane emissions. This proposal will develop new science to address these needs, and pave the way towards the next generation of GHG evaluation methodologies. Our work will span four key areas: 1) Improving models of emissions from individual source and sink sectors to determine when and where GHG emissions to the atmosphere occur from both natural and anthropogenic systems. 2) Utilising new surface and satellite atmospheric GHG observations, such as isotopic measurements of methane and carbon dioxide, and measurements of co-emitted or exchanged gases (oxygen, carbon monoxide, nitrogen dioxide and ethane) to provide information on emissions from different sectors. 3) Utilising enhanced model-data fusion methods for making use of these new observations and for better quantifying uncertainties. 4) Integrating data streams to determine the highest level of confidence in the UK's emissions estimate. To improve the transparency of national reports, scientists and policy makers have been strongly advocating for the combination of such methods in the reporting process. The UNFCCC, at its 2017 Conference of Parties, acknowledged the important role that emissions quantified through atmospheric observations could have in supporting inventory evaluation (SBSTA/2017/L.21). Through our close links to the inventory communities in the UK and around the world, the IPCC and to UK policy makers, we can ensure that our work will be used to update and improve the UK's GHG submission to the UNFCCC and will showcase methods of best-practice.

Nitrogen compounds are essential for life. They are needed to make many biological compounds including proteins, amino acids, DNA and ATP (the 'fuel source' of cells), without which no living organism could survive. Nitrogen is particularly important because it often limits food production, while high levels of N compounds in the environment lead to serious pollution problems. By supplying N fertilizers, farmers greatly improve their yields. This has been essential to feed the growing world population over the last century, with N fertilizers estimated to sustain ~3.5 billion people, almost half of humanity. While the increased manufacture and mobilization of reactive N sources can be seen as a great feat of 'geoengineering', there have been many unintended consequences. A growing human population needs more food, so more fertilizers, especially as we now eat more animal products per person. The result is a complex web of pollution issues, threatening water, air and soil quality, altering climate balance and impacting on ecosystems and human health. In addition to the loss of N from farms, other sources cannot be forgotten. These include air emissions from burning, and losses to water from sewage systems. Overall, human alteration of the global N cycle makes for a multi-issue problem that ranks alongside climate change as one of the great challenges of the 21st century. The European Nitrogen Assessment has estimated that N pollution alone causes 70-320 billion Euro per year of damage across the EU (Nature, 14 April 2011,472,159). Given the wide diversity of nitrogen loss pathways into the environment, there are many potential solutions. In a recent report 'Our Nutrient World' led by CEH for the United Nations Environment Programme (UNEP, launched Feb 2013), 10 key actions were identified which would contribute to better nutrient management, simultaneously helping to meet food security goals while reducing the pollution of air, land and water, with multiple benefits for ecosystems, climate and human health. However, 'Our Nutrient World' also identified that there is currently no global international agreement that links the many benefits and threats of nitrogen. As a result, there is also no coordinated scientific assessment and support process to quantify and demonstrate these linkages. This gap is now being addressed by the International Opportunities Fund (IOF) of the NERC through its support for a new endeavour "Pump priming to towards the International Nitrogen Management System" - or 'INMSpp' for short. The central idea is that a scientific support system is needed that can provide the evidence needed to show how joined-up management of the global nitrogen cycle will deliver multiple benefits, and to be able to evaluate options that policy makers may wish to consider. Already there is a developing ambition for INMS as reflected by the invitation from the UN Global Environment Facility (GEF) for the NERC Centre for Ecology and Hydrology (CEH) to work with UNEP to develop a concept to establish a future INMS approach. Ultimately this would be a major endeavour, linking indicators, models and datasets to allow evaluation of possible international agreements. The INMS pump priming project provides a key step towards this eventual goal. As one of the key challenges to establish model chains from source to impact to mitigation and adaptation the INMSpp project has taken on the task of working out how integrated global modelling of the nitrogen cycle should be developed. The project will bring together a global consortium to examine how models can be joined up to demonstrate the net benefits of better nitrogen management. This will be a key resource as the INMS approach is developed. The outcome is the prospect to show how linking up different international environmental agreements can build common ground, simultaneously supporting food and energy security and a cleaner environment.