Full-size solar panel daylight reflectance test

Related services Daylight reflectance

We are able to test the daylight reflectance of full-size solar panels. Shown below is an example.

All typical commercial solar panels can be tested, including panels greater than 1.2 m x 2.4 m in size. The results reported are the same as our standard daylight reflectance testing service (sample report). Due to the extra effort in handling such large and heavy samples, some large-size sample surcharge is applicable.

Import Optics user database into LBNL WINDOW

Related services Glass optical & thermal properties

We have a post on how to import user IGDB format file into LBNL optics. The next step is to import the user database created into LBNL WINDOW for further calculations. Please refer to the steps below for the operations.

Step 1. Set the user database as the optical data source

In the “File” -> “Preference” -> “Optical Data” tab, browse the Optics user database file and set it as the optical data source, as shown below.

Step 2. Import glass optical data from Optics user database

In the glass library (“Libraries” -> “Glass”), click “Import” (in the “List” view). In the pop-up window, set the format as “IGDB or Optics User Database”, as shown below. The optical data entries in the Optics user database can then be imported in the next pop-up window.

Our instrument: heat flow meter

We are a Singapore-based third-party test laboratory, providing lab test services of material optical & thermal properties. We use Thermtest HFM-100 heat flow meter, with the following key information.

Thermtest HFM-100 heat flow meter

Key specifications:

  • Preferred sample size: 300 mm × 300 mm
  • Maximum sample thickness: 100 mm
  • Plate temperature range: -20 – 70 °C
  • With high thermal conductivity kit

Related lab services

±0.001 rounding discrepancy in specular daylight reflectance calculation

Related services Daylight reflectance

In the daylight reflectance test, the specular daylight reflectance is calculated as:

Specular daylight reflectance = Total daylight reflectance – Diffuse daylight reflectance

Due to the rounding operations, the reported specular specular daylight reflectance could be:

Specular daylight reflectance = Total daylight reflectance – Diffuse daylight reflectance ± 0.001

Shown below is an example result set, with this ± 0.001 discrepancy:

  • Total daylight reflectance = 0.216 (21.6%)
  • Diffuse daylight reflectance = 0.200 (20.0%)
  • Specular daylight reflectance = 0.015 (1.5%)

Some customers expect that the specular daylight reflectance should be 0.216 – 0.200 = 0.016 (1.6%) and suspect that there is a typo in the test report.

Our daylight reflectance test reports are generated by in-house software automatically. The ±0.001 discrepancy is not due to a calculation mistake or a typo, but due to the rounding operations, as illustrated in the table below:

Before roundingAfter rounding
Total daylight reflectance0.21560.216 (21.6%)
Diffuse daylight reflectance0.20040.200 (20.0%)
Specular daylight reflectance0.01520.015 (1.5%)

Weather monitoring with Delta OHM HDMCS-100 all-in-one weather station

Related instruments Weather stations

Shown below is a Delta OHM HDMCS-100 all-in-one weather station installed at a construction site for weather monitoring.

The instrument measures the following 6 quantities:

  • Wind speed
  • Wind direction
  • Temperature
  • Humidity
  • Pressure
  • Rainfall

The data are automatically uploaded to Delta OHM cloud via 4G. The end users can conveniently view the results with a web browser.

The initial hardware wiring and software configurations were performed by OTM and the end users just needed to do some simple last-step mechanical mounting.

Preparing samples for luminance contrast test

Related services Luminance contrast

The luminance contrast test is always in terms of two samples in a pair, typically one bright color sample and one dark color sample. There are two scenarios for sample preparation:

  • Side-by-side flat surfaces
  • TGSI studs on a flat surface

Side-by-side flat surfaces

For side-by-side flat surfaces, two flat-panel samples need to be submitted. Shown below is an example:

The preferred sample size is 100 mm x 100 mm or slightly smaller. The maximum sample size is 300 mm x 300 mm. Only 1 pair of samples (2 pieces) are needed and it is optional to provide additional samples as the backup.

TGSI studs on a flat surface

For Tactile Ground Surface Indicator (TGSI) studs on a flat surface, it is possible to submit the samples as either integrated samples or loose samples.

Integrated samples

Shown below is an example of an integrated sample of TGSI studs on a flat surface:

The preferred sample size of the integrated sample is 100 mm x 100 mm or slightly smaller. The maximum size is 300 mm x 300 mm. Only 1 sample is needed and it is optional to provide additional samples as the backup.

Loose samples

It is possible to submit TGSI studs and flat surface samples separately, without fixing them. Shown below is an example.

It is recommended to provide 2 – 5 loose TSGI stud samples.

For the flat surface sample, the preferred sample size is 100 mm x 100 mm or slightly smaller. The maximum size is 300 mm x 300 mm. Only 1 sample is needed and it is optional to provide additional samples as the backup.

The difference between NFRC winter and summer U-values

Related services Glass optical & thermal properties

Listed in the table below are the standard NFRC winter and summer environmental conditions:

Environmental conditionNFRC winterNFRC summer
Outdoor air temperature-18 °C32 °C
Outdoor wind speed
(convection)
5.5 m/s
(26 W/m2K)
2.75 m/s
(15 W/m2K)
Outdoor sky temperature-18 °C32 °C
Outdoor sky emissivity11
Indoor air temperature21 °C24 °C
Indoor convectionASHRAE/NFRC inside modelASHRAE/NFRC inside model
Indoor room temperature21 °C24 °C
Indoor room emissivity11

These are the standard environmental conditions defined in the NFRC standards and widely used by the industry. It is possible to define local environmental conditions and use them in a specific region.

In the US, the NFRC winter U-value is used (called U-factor and with the imperial unit).

In Singapore, the NFRC summer U-value is typically used, and, in our test reports, both the winter and summer U-values are reported.

For most glasses, the summer condition U-value is smaller than the winter condition Value. The main reason is that the outdoor wind speed in the summer conditions is lower and it results in a lower outdoor side convective heat transfer rate.