High density sensor network system for air quality studies at Heathrow airport

Lead Research Organisation: University of Hertfordshire
Department Name: Science and Technology RI

Abstract

Overview The overall scientific objective is to demonstrate the potential of low cost sensor network systems for characterising air quality in the urban environment at an appropriate granularity in order to understand the factors which influence pollutant distributions on local scales. The ultimate aim is develop and demonstrate a sensor network system* methodology which, when appropriately deployed, can contribute to scientific, economic, public policy and regulatory issues, crossing climate change, human (health) responses, as well as air quality on local and regional scales. As well as demonstrating a generic capability, the intention of this application is to address a number of specific scientific and ultimately legislative issues relevant to London Heathrow Airport. We therefore propose to deploy a high-density air quality sensor network system in and around London Heathrow Airport for an extended period. This will use state of the art low cost sensors for selected gases and for size speciated aerosols, providing an unprecedented data-set for use in a range of activities and outcomes. Air Quality and Human Health The World Health Organisation (WHO) reported in 2005 on the effects of air quality on human health and identified the relative contributions to mortality from different components of air pollution. The strongest correlations with health were found to be particulate matter (PM), followed by O3 and NO2; for example it was estimated that a reduction in the PM10 annual mean exposure to 20 ug m-3 would lead to a reduction of 22,000 attributable deaths per year in Europe. The report also identified a substantial reduction in the quality of life for millions of citizens with pre-existing respiratory and/or cardiovascular disease. However, the magnitudes of health impacts per incremental increase in pollutant levels vary between studies, in part due to imperfect knowledge of human exposure particularly within urban locations and complex, multi-source transport infrastructures. The problem lends itself to a high density, long term network of air quality monitoring to refine our understanding of the drivers of the health impacts, and better understand potential mitigation options. London Heathrow Airport There is also a strong political aspect. In 2004 the DfT established technical panels of experts to strengthen and update the assessment of air quality around Heathrow Airport in response to the Airport Transport White Paper 'The Future of Air Transport'. This identified key planning issues with respect to compliance with air quality standards. Deployment of a Sensor Network at London Heathrow Airport Miniaturised low cost measurement methodologies are now available for measurements of a range of chemical species and aerosols at concentrations observed in the urban environment, while infrastructures also exist for GPS (positioning) and GPRS (mobile phone data transfer). The proposed primary sensor network would consist of a series of ~60 sensor units combining NO, NO2, CO, O3, CO2, hydrocarbons, SO2, size speciated aerosols, temperature and RH, allowing deployment along the (14 km) perimeter of Heathrow airport at intervals of a few 100 m. Additional sites would be co-located with static AURN sites in neighbouring Boroughs, and on a campaign basis mobile sensors would be deployed. The project also aims to bring complex mathematical techniques to provide innovative ways of calibrating the sensor network, and sophisticated methods for storing and displaying the data obtained. State of the art computer modelling of pollution levels around Heathrow would also be undertaken, with the aim of producing a more refined tool for assessing the potential impacts, e.g. of airport expansion. The intention is that the sensor network would be developed during the first year of the project, deployed during the second year, with major data analysis during the third year.

Publications

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Hesse E (2012) Modelling diffraction by facetted particles in Journal of Quantitative Spectroscopy and Radiative Transfer

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Stanley, W (2013) A Low-Cost Optical Particle Counter for Networked Deployment in UK Aerosol Society Annual Conference

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Stopford, C (2011) A Miniature Airborne Particle Classifier (APC) in European Aerosol conference

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Ulanowski Z (2012) Retrieving the size of particles with rough and complex surfaces from two-dimensional scattering patterns in Journal of Quantitative Spectroscopy and Radiative Transfer

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Ulanowski ZU (2014) Dust layer profiling using an aerosol dropsonde in International Conference on Atmospheric Dust, Castellaneta Marina, Italy

 
Description Although the overall project was to investigate the effects of air pollution around a major airport (Heathrow), our contribution was the development of low-cost aerosol monitors that could be deployed in a large network of sensors (>60 units). Such aerosol sensors were traditionally far too expensive (£1,500 to £12,000) each, to be deployed in such networks. Our new sensors were built at a cost of ~£150 each, and provide high quality particle size and concentration data that could be used in subsequent detailed data analysis relating to air quality assessment, source apportionment, and epidemiological effects.
Exploitation Route The sensor technology we developed has now been patented worldwide and has been licensed for commercial manufacture by Alphasense Ltd, Essex UK, a leading manufacture of gas sensors. Mass production is underway with considerable levels of pre-production orders from overseas distributors etc.
Sectors Environment,Healthcare

URL http://www.herts.ac.uk/research/stri/research-areas/cair/particle-instruments-and-diagnostics/low-cost-particle-detectors
 
Description The particle detection technology developed for the NERC Airborne Particle Classifier project is now being exploited in the NERC Network of Sensors project 'High density sensor network system for air quality studies at Heathrow airport', NE/1007296/1 (Universities of Cambridge, Hertfordshire, Manchester, Imperial, plus NPL and CERC). This project saw more than 60 of the Hertfordshire particle detectors positioned in a ground-breaking project around the perimeter of Heathrow airport to undertake long-term ambient aerosol monitoring (alongside trace gas monitoring) and the effects of these pollutants on public health. The low-cost Optical Particle Counting technology developed in this project has been licenced to Alphasense Ltd and is now in commercial production with sales worldwide.
First Year Of Impact 2014
Sector Environment,Healthcare
Impact Types Societal,Economic

 
Description Commercial funding
Amount £98,000 (GBP)
Organisation Alphasense 
Sector Private
Country United States
Start 11/2014 
End 11/2015
 
Description Research funding for 'Pocket PM' personal air quality sensor development
Amount £86,000 (GBP)
Organisation Alphasense 
Sector Private
Country United States
Start 02/2017 
End 02/2018
 
Description Low cost air quality sensor development. 
Organisation Alphasense
Country United States 
Sector Private 
PI Contribution Arising directly from research carried out in the 'High density sensor network system for air quality studies at Heathrow airport' Project (NE/1007296/1) we have designed a range of compact and ultra-compact sensors for ambient particle monitoring. Licensed to Alphasense in 2013, these devices are now being manufactured as the commercial OPC-N2 air quality PM sensor and OPC-R1 wearable air quality sensor. Like conventional optical particle counters, the OPC-N2 measures the light scattered by individual particles carried in a sample air stream through a laser beam. These measurements are used to determine the particle size (related to the intensity of light scattered via a theoretical calibration based on Mie scattering theory) and particle number concentration. Particle mass loading- PM2.5 or PM10, are then calculated from the particle size spectra and concentration data, assuming density and refractive index. Most conventional OPCs employ narrow inlet tubes (and often an additional 'sheath-flow' of particle-free air) to physically constrain the airborne particles to the more uniform central part of the laser beam and ensure accurate sizing. Such instruments must incorporate both an air-pump sufficiently powerful to draw the sample aerosol through the narrow inlet tube and a particle filter upstream of the pump to avoid pump contamination and ultimate blockage. The result is a unit with relatively high current consumption and regular maintenance to replace the pump protection filter (frequent in dirty atmospheres). The OPC-N2 uses a fundamentally different approach that removes the need for both a pump and replaceable particle filter. Instead, the patented OPC-N2 uses a combination of a custom-designed elliptical mirror and dual-element photodetector to create a 'virtual sensing zone' in free space at the centre of an open scattering chamber. The sensing zone and its surrounding space is then illuminated by a thin ribbon-shaped laser beam. Particle-laden air passing unconstrained though the scattering chamber traverses the laser beam both within and outside the sensing zone, but only those particles traversing within the sensing zone are 'validated' by the dual-element detector and counted/sized by the OPC electronics. The result is a new OPC that uses only a miniature low-power fan to generate the required particle flow through the sensing volume. This, and the removal of the requirement for a pump and particle filter extends considerably potential unattended field deployments and reduces maintenance. The OPC-N2 classifies each particle size, at rates up to ~10,000 particle per second, adding the particle diameter to one of 16 "bins" covering the size range from ~0.38 to 17 µm. The resulting particle size histograms can be evaluated over user-defined sampling times from 1 to 10 second duration, the histogram data being transmitted along with other diagnostic andenvironmental data (air temperature and air pressure) via an SPI interface to a host computer.
Collaborator Contribution Alphasense have taken the prototype sensors developed at the University of Hertfordshire and re-engineered them to be suitable for mass production, using injection moulded parts and low-cost optical components. They have continued to work with Hertfordshire on the development of user software for data analysis and interpretation. They have also engaged with major organisations such as the United Nations Environment Programme (UNEP) who are using the Alphasense products in networks of air quality sensors to be deployed in numerous African cities in the coming years (see: http://www.airqualitynews.com/2015/09/02/unep-launches-low-cost-monitoring-unit/).
Impact Alphasense has engaged with major organisations such as the United Nations Environment Programme (UNEP) who are using the Alphasense OPC-N2 low-cost air quality sensors in networks to be deployed in numerous African cities in the coming years (see: http://www.airqualitynews.com/2015/09/02/unep-launches-low-cost-monitoring-unit/). OPC-N2 air quality monitors have (by early 2018) been sold to public and research organisations in more than 70 countries worldwide.
Start Year 2013
 
Title AN IMPROVED LOW COST APPARATUS AND METHOD FOR THE DETECTION OF A FLUID-BORNE PARTICLE 
Description An apparatus for the detection of a fluid-borne particle (10) in an optically defined particle sensing zone, the apparatus comprising: i) a scattering chamber (40); ii) a means for providing a sample of fluid (34), containing the fluid-borne particle, in the form of a flow through the optically defined particle sensing zone;iii) A means for generating a beam of radiation (12) through the optically defined particle sensing zone;iv)a single reflector or refractor (14) means having a primary focus (16) within the optically defined particle sensing zone and a secondary focus (20) located outside the beam of radiation; v) a detector means comprising a first photosensitive detection area (26) a second photosensitive detection area (29); vi) a means for deriving area from the radiation detected by the first photosensitive detection area and second photosensitive detection area of the detection means wherein the single reflector or refractor means is adapted to direct radiation scattered from the fluid borne particle passing through the beam of radation within the optically defined particle sensing zone to the detection means located at the secondary focus of the single reflector or refractor means and the optically sensing zone comprises a first and a second zone. 
IP Reference WO2012056217 
Protection Patent granted
Year Protection Granted 2012
Licensed No
Impact The particle detection technology developed for the NERC Airborne Particle Classifier project is now being exploited in the NERC Network of Sensors project 'High density sensor network system for air quality studies at Heathrow airport', (Universities of Cambridge, Hertfordshire, Manchester, Imperial, plus NPL and CERC). This project will see more than 70 of the Hertfordshire particle detectors positioned in a ground-breaking project around the perimeter of Heathrow airport to undertake long-ter
 
Title Detection of a fluid-borne particle using optical scattering 
Description Detecting the size and concentration of fluid-borne particles using optical light scattering. A flow of particles 10 passes through laser beam 12 in a scattering chamber. A single reflector or refractor means such as an elliptical or spherical mirror 14 is positioned such that its primary focus 16 lies on the axis of the laser beam 12 in an optically defined particle sensing zone. Scattered light from the particles in the optically defined particle sensing zone is reflected by mirror 14 to photo-detector 24 placed at the secondary focus 20 of the mirror 14. The photo-detector 24 comprises two photosensitive detection areas 26, 28. Means are provided for deriving data from the radiation detected by the first photosensitive detection area 26 and second photosensitive detection area 28 of the detection means. Therefore the elliptical mirror 14 and photo-detector 24 provide a method of optically defining a sensing zone within the illuminating laser beam. 
IP Reference GB2484930 
Protection Patent granted
Year Protection Granted 2012
Licensed No
Impact The technology has been licensed to Alphasense Ltd (Braintree, UK) who are now manufacturing products such as their OPC-N2 PM sensor which is being sold worldwide.They are being supplied to the Change London 'AirSensa' project that will eventually comprise a network of 10,000 sensors across London, possibly the largest air quality network in the world. (http://www.changelondon.org/projects.php# ). They are also being used in the UNEP (United Nations Environment Programme) initiative, funded by
 
Title Detection of fluid-bourne particles 
Description An apparatus for the detection of a fluid-borne particle in an optically defined detection zone, comprises a scattering chamber 3, a fan 1 for providing a sample of fluid, containing the fluid-borne particle, in the form of a flow through the optically defined detection zone and a laser beam generator 5 for generating a beam of radiation through the optically defined detection zone 5. There is also a first reflector or refractor means 8a, a second reflector or refractor means 8b; a first detector means 11; a second detector means 12 and a means for deriving data from the radiation detected by the first and second detection means. 
IP Reference GB2474235 
Protection Patent granted
Year Protection Granted 2011
Licensed No
Impact The technology is sufficiently cheap to allow multiple fog monitors to be deployed across an area. This opens up new opportunities for studying fog formation and lifetimes, aiding hazard weather warnings and the development of fog dispersion methodologies.
 
Title Second Generation Low-Cost Particle Counter 
Description An apparatus for the detection of a fluid-borne particle (10) in an optically defined particle sensing zone, the apparatus comprising: i) a scattering chamber (40); ii) a means for providing a sample of fluid (34), containing the fluid-borne particle, in the form of a flow through the optically defined particle sensing zone; iii) A means for generating a beam of radiation (12) through the optically defined particle sensing zone; iv) a single reflector or refractor (14) means having a primary focus (16) within the optically defined particle sensing zone and a secondary focus (20) located outside the beam of radiation; v) a detector means comprising a first photosensitive detection area (26) a second photosensitive detection area (29); vi) a means for deriving area from the radiation detected by the first photosensitive detection area and second photosensitive detection area of the detection means wherein the single reflector or refractor means is adapted to direct radiation scattered from the fluid borne particle passing through the beam of radiation within the optically defined particle sensing zone to the detection means located at the secondary focus of the single reflector or refractor means and the optically sensing zone comprises a first and a second zone. 
IP Reference US2013229655 
Protection Patent granted
Year Protection Granted 2013
Licensed No
Impact The low-cost OPC technology is now being commercially produced by Alphasense Ltd, Essex UK. (http://www.alphasense.com/index.php/air/) by the name 'OPC-N2'. Units are being provided to the Change London 'AirSensa' project (http://www.changelondon.org/projects.php) that will ultimately see 10,000 networked OPC-N2 units deployed across London to monitor air quality. The units have also been selected by the United Nations Environment Programme, funded by the World Bank, for deployment in third-wor