Clean Air Removal - Testing/Validation

The Clean Air team is working feverishly to develop the Pollution Removal Prize Design and want to solicit feedback from the community on what the final phase of testing can and should look like.

The (preliminary) way we imagine this going is as follows: teams submit paper proposals describing their solution, how it would work and what new innovation is embedded within. XPRIZE and our judging panel would review submissions and advance the most compelling/promising proposals.

Fast forward roughly 12-18 months and those promising/compelling solutions arrive at our semi-finalist testing facility. The semi-finalists’ solutions will be tested within an environmental chamber of approximately 100m3 for the ability to remove PMs and PM precursors (O3, NOX, SOX, NH3) from the chamber in a 30-60 minute period. In this round of testing, we want to validate that the team’s solution does in fact work and could, with additional work, meet the challenge of the final round of testing. We anticipate utilizing particle counters (to quantify the number of particles captured of different sizes) and other standard regulatory-grade air monitoring equipment to measure precursor levels before and after intervention. Judges would review the data and again select the most promising solutions to move onto the Finals.
(Note that these details are subject to change)

Fast forward another 12-18 months and teams show up at a different XPRIZE testing facility. Now we are playing with some ideas about how we want to do this, but curious to get the community’s thoughts.

  1. Outdoor testing - we’ve been thinking of this in two ways:
  • true outdoor, live environment testing or
  • an environmental testing chamber erected in a live environment and using outdoor air
    How might we test the first example? We’ve been taking some cues from 'Urban-scale SALSCS, Part I: Experimental Evaluation and Numerical Modeling of a Demonstration Unit" and thinking a number of aerosol monitors in and around the solution might do the job, but what other avenues might we have to test and validate different types of removal systems?
  1. Scale - what if we skipped using outdoor air and instead performed another environmental chamber test, only substantially larger? Say 10x or 100x. What volume of air would be a significant achievement for a solution to clean in a period of time? Would proving new levels of large-scale indoor air pollution filtration move us closer to achieving ambient air pollution removal?

Some good options there for testing @jamesburbridge

An environmental chamber offers the advantage of a controlled, repeatable, scenario that presents each competitor with identical conditions. It also allows us to monitor many parameters in a reliable way - and probably provides the fairest method for comparing the efficiency of each device (under a range of conditions, and for each of the given pollutants).

A real-world outdoor test, across all seasonal parameters and weather conditions, would be useful to test the robustness and effectiveness of devices in reality. However, we cannot guarantee all extremes would occur over say one year, and given that each device would be in a different location we cannot ensure equal and fair test conditions. So perhaps an environmental test chamber that can generate a range of conditions (e.g. temperature, wind speed, and humidity) is the best way to do this.

If the chamber is large enough then we might be able to also mock up some urban street infrastructure, to which devices might (or might not) be attached.

PS: It is likely that different technologies will be used to deal with PM, compared to the gaseous precursors. So we might want to reflect on how we prioritise each of these pollutant objectives [which is a common problem in air pollution].

Hi @bartc , @hopkepk , @rgschreib , @swihera , @carlbozzuto ,
Please let us know your thoughts on a viable testing scenario for an emission removal technology.


The chamber idea for the first set of tests sounds good to me. Since this first test is more or less a proof of principle test, having a controlled chamber that is the same for all competitors makes comparisons somewhat easier for the judges. I still think there needs to be some throughput in the chamber. I would suggest a fan with the capacity to turn over the air in the chamber something like 50 - 100 times in the hour of testing. A 100 m3 box is on the order of 3500 ft3. Even with 100 times turnover, the volumetric flow rate would only be 6000 cfm. The weight of air treated would only be 420 lb/min. Ambient air in the US is 12 micrograms/m3. A 100 m3 box would contain 1200 micrograms of particulates, or 1.2 milligrams. Presuming the air was recycled (ie closed loop), the most that could be collected would be 1.2 milligrams. That would be asking a lot for the measuring equipment. Of course the air in the box could be spiked with additional particulate to increase the concentration. Let’s assume we can add 1.2 grams of particulates (properly sized). That could give us the opportunity to distinguish the differences in performance of the various systems to be tested. We should be able to distinguish differences of some number of centigrams in what was collected. Some kind of mass balance would be nice to assure ourselves that the testing was valid (ie the amount captured is roughly equal to the amount reduced in the concentration of particulates in the gas stream).

Relative to the larger scale test facility, I would tend to lean toward an outdoor facility. I don’t know exactly how many participants will be involved at this stage, but even at 10 times the flow rate, we would still be looking at a fairly small amount of air (around 2 ton/hr). A small gas turbine (around 10 Mw) moves about 3 ton/min of air. A Solar Saturn 20 gas turbine of 1.2 Mw moves about 0.42 ton/min. With the small amount of air flow, there is no particular reason why all of the test units could not be in the same location. There would have to be some spacing requirement, but that should not be a problem. Presuming that we are still looking at ambient air capture, the test should be conducted with ambient air. The problem will be that there may be a significant amount of particulate capture, but the overall ambient air concentration will not change much. Atmospheric mixing will still be significant. Certainly the exhaust air will have a lower concentration of particulates. However, that air will mix with the local air, whose concentration will overwhelm the small amount of air being processed. The real value of testing outdoors is to see the real impact of varying ambient conditions on the unit operations. The impact of rain immediately comes to mind. For argument’s sake, suppose the collection device uses filter paper to collect the particulates (ie blow the air over filter paper). Water and filter paper do not hold up well. The paper shreds and the device is no longer effective. Materials of construction will be important for any device that is expected to run for the longer term. Corrosion will always be an issue. Winter operation is always problematical. While it is true that the device can be housed to offer some protection from the elements, there still has to be an air intake and a clean air exhaust. Again, if we are talking about ambient air cleaning, then the amount of particulate collected per volume of air treated will be the key parameter.

Hi @peterstyring , @Joonas , @Ananya_Roy , @sagnikdey , @djaffe , @mskoehle ,
Join the discussion to let us know your thoughts on how the final round of testing should look like.

Great points again @carlbozzuto :slight_smile:
The evaluation/monitoring team will sure need to reflect on how they will measure the quantities of particulate removed from the air. It’s going to be challenging :slight_smile:

On a wider point @jamesburbridge, it might also be worth reflecting on how the proposed technologies, and their associated methodologies, deal with the particulates they collect. This might give a hint to how much PM was collected and methods to measure it. It’ll also be interesting to assess if the PM waste disposal processes are effective, efficient and safe.

Hello @ET_Tony , @jwangjun , @Adaryani , @rohan9602 , @mprakhar , @JosieAtCapture ,
We would like to have more feedback from diverse individuals. join the discussion to share your views on the testing/ validation of PM Removal solutions. Thanks.

Copy Pasting Dr. Hopke’s comment:
A couple of issues that you need to decide on.

To win the prize does one have to present an idea and a scaled down model to demonstrate its potential or does there need to be a full scale demonstration of its effectiveness?

Model tests are easy. Find one of the groups with a large aerosol chamber (>20 m3) where well characterized aerosols can be generated involving several compositions (vehicle dominated, biomass combustion dominated, dust dominated, etc.) with sufficient measurement capabilities that size dependent behavior of the system can be assessed.

Full scale gets more difficult (and expensive). I could envision using a large domed stadium like the Georgia Dome, Superdome or AT&T Stadium and generating an indoor aerosol using things like fireworks and using an effective array of monitoring equipment (including power consumption) to assess its removal capabilities.

However, I could also environ a planning solution where you design an urban landscape that encourages dispersion, reduces emissions by coordinated traffic control, proper public transport, etc) that reduces pollution without an active control system. This solution can only be tested via simulation and then the question is how to get independent validation of the results. I would expect the contestants to submit a simulation showing a comparison between a business-as-usual scenario and their modified urban design solution. However, they could obviously bias their model to make their solution look better than it is (whether done intentionally or unintentionally). Thus, there would have to be a way to independently test their design for its effectiveness. There would be groups who could build the necessary computer models but it would not be quick or cheap to do so. It might also be possible to build physical models that would allow measurements, but would that be required as part of the submission or done by an independent 3rd party (my preference) to assess the design.

Thus, there are some issues for you to decide. Does the solution have to be a physical device? It would certainly be possible to design efficiency and effectiveness tests for such devices even at various scale levels. If planning and design would be allowed, then it is much more difficult to assess the feasibility of these approaches and obviously they would be applicable to new cities and be very difficult to apply to existing problem areas.

If you want to get into more details, let me know @jamesburbridge

@jamesburbridge , @TerryMulligan
Just seen this article today:
Graphene-titanium catalyst lays foundation for smog-eating concrete

This, and similar approaches, would need to be tested in a realistic scenario. For example, how would it perform when exposed to particulate pollutants, and other (biological) substances that cover the faces of buildings, over a long period? Perhaps this raises the value of real world outdoor testing [after the initial chamber tests].