5 Effects of Solar Insolation To Consider When Installing Hazardous Areas Wireless Technology
Solar insolation is not insulation! Sometimes these two terms can get confused.
Solar insolation is the incident solar radiation onto an object. Specifically, it is a measure of the solar energy incident on an area over a period of time. Typically expressed as either:
- Kilowatt-hours per square metre (kWh/m2); or
- Watts per square metre (W/m2)
The energy from solar radiation can either be absorbed or reflected by an object. When the radiation is absorbed, it is converted into thermal energy and the object will heat up. If you have ever sat on a hot metal park bench in summer and burnt the back of your knees, then you have experienced firsthand the effects of radiation absorption. The metal structure of the bench has absorbed the solar radiation, which has heated the material making it hot to touch.
When selecting a hazardous area enclosure to house electronic equipment it is important to consider the following four aspects in combination:
1&2. Solar insolation and ambient temperature
Solar radiation will heat the enclosure and this heat will then transfer to the electronic equipment housed within it. Many areas of the world are susceptible to this occurrence. In hotter climates, it is not unusual to have daytime temperatures easily over 35oC (95oF) with solar radiation peaking at 800W/m2. Extronics have calculated that 800W/m2 can increase the internal temperature of an enclosure by 6oC (11oF).
3. Heat dissipation from the electronic equipment
When electronic equipment is housed within an enclosure the equipment’s electrical energy will often be converted and dissipated as heat energy due to inefficiencies. This heat energy will also heat up the internal temperature of the enclosure. For example, a device that consumes 30W can create an internal temperature rise of 11oC (20oF) depending on the size of enclosure chosen.
The ability of an object to reflect solar insolation is called the albedo effect. For visible colours, darker colour has a low albedo effect, they absorb more insolation, and lighter colours have a high albedo effect or higher rate of reflection. For example, snow reflects 85-90% of insolation, whereas asphalt reflects only 5-10%. Extronics have calculated that the internal temperature of an enclosure can be 7oC (13oF) to 9oC (16oF) hotter when using a darker colour enclosure compared to a shiny white colour.
Therefore, to calculate the total internal temperature of an enclosure the following need to be summed together.
Total internal temperature = Ambient temperature + effect of solar insolation + effect of dissipated heat + enclosure colour
Electronic equipment can be rated around 50oC (122oF). So, what is the issue? When you add all the effects together you could well be above the electronic equipment’s temperature rating!
For example: Total internal temperature = 35oC + 6oC + 11oC + 7oC = 59oC (138oF)
The iWAP XN3 has been designed to take these environmental factors into account to help ensure electronic equipment housed within its enclosure remains within its published temperature rating.
As well as providing superior corrosion resistance the iWAP XN3 is powder coated with a glossy white finish giving it a high albedo. In addition, the cooling fins added to the enclosure design removes between 8oC (14oF) and 10oC (18oF) from the internal temperature according to Extronics testing calculations. This gives the enclosure the best possible chance to reflect solar insolation.
Marine grade aluminium was chosen as it also provides exceptional corrosion resistance. Additionally, Aluminium has higher thermal conductivity, compared to other materials, allowing heat energy to be conducted away quickly.
5. Internal equipment layout
Extronics has decades of knowledge and experience of how to architecturally layout electronic equipment within an enclosure to ensure that any heat is evenly distributed to prevent hotspots. For example, equipment that may be more susceptible to heat is placed lower down in the enclosure where the temperature is cooler. The iWAP XN3 comes in 4 sizes which can accommodate most sizes of electronic equipment inside it. Selecting the most compact size must always be balanced against having sufficient space to safely dissipate all heating effects.
Based on the wattage of the electronic equipment to be housed within the enclosure, your ambient temperature and location in the world, Extronics can calculate the anticipated internal temperature rise within its iWAP XN3 enclosure. Extronics can then work with you to select the most suitable enclosure size to ensure that your valuable equipment remains within the manufacturer’s published temperature range.
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