Planning the installation and use of the DustIQ
This chapter describes the best locations to place the DustIQs and how to make the best of the acquired data.
Where to place DustIQ in the PV plant
Measuring dust and soiling ratio is a new field of science. There are many opinions about it, but there is no large history
of data and experience in measurements. Although the spot measurement of DustIQ is very precise, it is wise to do
interpretation and use common sense when extrapolating the measurement value to the whole PV plant, or a part of it,
for decision making. The measurement value thus is true, the only question is, whether this value is representative for the
PV park.
For giving a good representation of soiling across the PV plant, one should place multiple DustIQs across the plant. In fact,
the
IEC61724-1:2017
Standard for PV system performance (Monitoring) prescribes that one should have as many dust-
sensors as irradiance sensors. This makes intuitive sense: it follows the same logic as irradiance that also is not constant
across a solar plant, and one has to have sufficient measurements to make a valid interpretation. For the number of
DustIQs, one can thus follow the own policy for the number of pyranometers. Of course, every additional DustIQ adds up
to a better overall measurement. For 1 MW plants, 1 DustIQ placed in the middle could do, whereas for larger plants – say
25 MW- one could imagine the one in the middle, and one near each corner could be a logical choice to understand the
soiling pattern across the plant.
Soiling is a different phenomenon than irradiation, and also very site specific. Where you normally expect the same
average irradiation value for all pyranometers at a solar plant, this is not necessarily true for DustIQs: if the wind always
blows from the east, one could expect more soiling (and thus another cleaning interval policy) at the east side of that solar
plant. When wind direction changes over seasons, this pattern could shift during the year. Also, it is known that the very
ends of an array, and the bottom row of an array (closest to the ground), typically suffer more from soiling than the rest
of the PV modules. Therefore, better not place DustIQs here for cleaning policy, unless your purpose is to learn and study
soiling behaviour.
Again, soiling is a new scientific area, especially when applied to solar plants. Kipp & Zonen will build up the application
data base along with the users, in order to set standards for best practices. When installing the DustIQs, it makes sense to
follow up the instrument readings over a period of weeks, and do visual inspection as to reassure yourself on
representative values. DustIQ is designed in such a way, that you can easily dismount it, and put it at another location,
where you trust it to give the most representative information for your purpose. DustIQs can be placed at the side, and at
the top of PV modules, in the middle of an array or at the sides. Horizontal in
not
advised at soiling is uneven in the vertical
direction, influencing the PV module output. Kipp & Zonen has introduced DustIQ-array-fillers, in order to install the
DustIQ in the middle of a row and in the middle of an array, without making gaps in the array.
