Hi @jamesburbridge great work.
The draft Prize Design shows a great deal of thought has gone into this complex and challenging topic (air pollution). It identifies many key points and parameters, and poses some interesting questions.
Some initial thoughts to this are presented below.
The phrase “prevention is better than cure” can be applied to air pollution generally, in the sense that it is usually much easier to capture emissions at source, or not generate them in the first place (rather than trying to suck out pollutants over a vast area).
Given that this challenge attempts to do the latter the above paragraph is still useful because it allows us to consider the following:
- How long will it be before most emissions at source are prevented? (years)
- Over what area would a solution actually be deployed? (hot spots, selected roads, wider areas)
- What types of environment would the solution be deployed in? (urban, suburban, rural)
The XPRIZE community have shown that removing pollutants from ambient, outdoor, air represents a huge technical challenge. This is what XPRIZEs focus on (audacious challenges) but with point 1 in mind: how long would it actually take to deploy a fully working infrastructure and would project completion dates pass the point at which emissions at source have been prevented - thus rendering the approach obsolete before its completion?
For example, emissions from vehicles will be significantly reduced (in clean zones) within the next 10 years, and significantly reduced in many urban areas within 20 years (thanks to low and zero emission vehicles, e.g. electric). Assuming an XPRIZE challenge of 3 years, legal and urban planning of 3 years, and a contractual and construction time of 3 years, the first solutions deployed might only deliver ~10 years of useful service across a wide urban area before they were no longer needed (due to emissions at source being eliminated). In the case of clean zones they might be obsolete before installation has been completed. Other emission sources exist, of course, but it is reasonable to assume that these too will be prevented within the next 10 to 20 years - via technological and policy based solutions.
If, on the other hand, we assume time to deployment is not an issue then we can consider points 2 and 3. These ambitious projects might have more chance of success if their scope is focused on a few limited areas where the greatest environmental/health impact is expected: hot spots where many pedestrians are exposed to pollution. Pollution levels, from traffic, can be higher near busy roads and intersections; and in street “canyons” (streets with high buildings both sides of the road, trapping air pollution). Pollutant concentrations are also greatly affected by the weather, particularly the wind and vertical air currents. On days with no air movement pollution levels escalate. So potentially a limited number of hot spots could have their pollutant concentrations kept below legal limits. If the operational factors (e.g. energy and cost) were high then the devices might only be activated when those locations exceed legal limits (e.g. at times of high traffic flows and unfavourable weather).
Having said that, the above overlooks those scenarios where wide spread pollution is produced by a combination of factors from different emission sources (e.g. traffic locally and further afield, industry, power generation, secondary pollution (photochemical smog), and agricultural and forest fires). This might require a much larger and expensive deployment of the proposed technology. That challenge might be too great (but we don’t know unless we try).
With the above in mind, here are some comments on specific aspects of the draft prize design…
Re: AQI to <50
Different countries have different air quality index algorithms and values, and these are subject to change as epidemiological studies learn more and national governments make their own intreprations of what is “safe”. Recommendation: use specific values and units (e.g. micro-grams per metre cubed) for each pollutant concentration to avoid those ambiguities. Using international values might be useful: WHO air pollution limits / recomendations.
Re: Total PM removed
● Metric = micrograms of PM removed from ambient air
● Alternatively, or in conjunction, could be measured as a rate (i.e. PM removed per minute or hour)
Assuming the technology presents a given area to the polluted air (e.g. as a fan’s intake, or a static surface), it has to extract pollution at a comparable rate to that of the (local) emissions source, or the rate of pollutant delivery (by wind and diffusion). For example, a canyon type street (with no wind) might have to extract pollutants at a similar rate to the total vehicle emissions on that street - but if only part of the street has the clean air technology fitted then it might have to extract pollutants at a faster rate. Admittedly, this complicates matters because we have to know how the technology will be deployed spatially. So rate of extraction might be required, e.g.:
micrograms of pollutant per unit surface area (of the technology’s interface) per minute.
Re: Total Gases removed
Similar to PM (above).
Re: Minimum Length of Time Tested
To test durability and operation under a wide range of weather conditions the longer the better. Testing in extremes of weather is relevant (summer, sun, hot, winter, cold, windy, no wind, atmospheric inversion layer, fog). Yes: include maintenance (and pollutant removal) aspects in the test cycle.
Re: Energy usage
Yes: assess energy consumption (per mass of pollutant extracted?) and the technology’s own environmental impact (emissions, etc.).
Re: Land Use / Footprint
Needs to be assessed (and see example above with canyon street).
Re: Waste Disposal
It might be useful to know how the collected waste is extracted from the device, how easy it is to do, and how often. For example, would a lane on a street have to be closed while the waste is extracted? Is the process risk free? What are the costs?
Re: Water Usage
If a technology proposes flushing the waste down the drains then the environmental impact of that should be considered [consult the relevant waste water authority].
All costs are of interest (capital, installation, operation and maintenance), but it’s always difficult justifying whether a proposed environmental solution is worth it. For the purposes of the challenge, if all other factors are equal amongst competitors’ solutions then cost might be the deciding factor. Perhaps a maximum viable cost could be crudely estimated by looking at something like the London congestion pricing and its new emissions related charge (specifically) and using that as a guide to derive a maximum cost for a technology. [Assuming a scenario where vehicle emissions are the primary concern. Not sure how to approach other (more complex) scenarios.]
Re: Monitoring - Reporting - Modeling
This might be a separate, but worthwhile, XPRIZE. It could be independent of the air cleaning technology prize. Although the infrastructure for an air cleaning approach would need to monitor that the air cleaning technology is working efficiently and air quality levels are maintained as expected.
Re: Waste Conversion Bonus Prize/Points
In the “upcycling” world we might want to turn the waste into a useful form. (Whilst being careful what it is used for, as some pollutants are toxic and will probably remain so.) Depending on the actual scale of deployment though, the quantity of waste might be relatively small.