To perform active cooling, the operating system turns on a cooling device, such as a fan. Passive cooling decreases the power consumed by the devices in a thermal zone; active cooling increases power consumption.

A passive heat sink is one with no moving parts. An active heat sink has moving parts. thus the second image is an active heat sink.

Passive heat sinks are those that don’t rely on forced air flow (fans) and are considered more reliable than active solutions. A good example is a heat sink that doubles as the device enclosure. In this example, heat is moved from one or more heat generating components to one or more enclosure walls.

An active heat sink uses an electronic device’s power supply to connect to a fan or a peltier device to actively divert heat away from the components by circulating air to cool the component or conduct heat away from it. Active heat sinks are often used in conjunction with passive heat sinks.

Passive cooling is a building design approach that focuses on heat gain control and heat dissipation in a building in order to improve the indoor thermal comfort with low or no energy consumption. Examples of on-site heat sinks are the upper atmosphere (night sky), the outdoor air (wind), and the earth/soil.

As water evaporates it draws large amounts of heat from surrounding air. Evaporation is therefore an effective passive cooling method, although it works best when relative humidity is lower (70% or less during hottest periods) as the air has a greater capacity to take up water vapour.

Applying passive cooling means reducing differenecs between outdoor and indoor temperatures, improving indoor air quality and making the building both a better and more comfortable environment to live or work in. It can also reduce levels of energy use and environmental impacts such as greenhouse gas emissions.

Reducing Conductive Heat Gain

1. Provide adequate insulation levels.
2. Install radiant barrier in attics.
3. Provide light-colored roof and wall surfaces.
4. Provide attic or roof ventilation.

Here Are 6 Science-Backed Ways to Keep Buildings Cool Without Air Conditioning

1. Windows and shading. Opening windows is a common way people try to cool buildings – but air inside will be just as hot as outside.
2. Paints and glazes.
3. Building materials.
4. Hybrid and phase change materials.
5. Water evaporation.

Best Ways to Cool a House: Downstairs

1. Draw the Blinds. While natural light is great, too much of it can turn your home into a sauna during the summer months.
2. Avoid Using the Stove.
3. Unplug Appliances You’re Not Using.
4. Turn on Bathroom Fans.
5. Opt for Breezy Clothing.
6. Add Outdoor Shade.
7. Switch to No-Heat Lightbulbs.

How to cool down your hot house the old-fashioned way

1. Related: Extreme heat in the garden: How to keep plants healthy with water, shade and mulch.
2. Close the blinds.
3. Don’t generate extra heat.
4. Make your own A/C unit.
5. Adjust your ceiling fans.
6. Use your exhaust fans.
7. Change your bedsheets.
8. Open windows at night.

10 WAYS TO STAY COOL WHILE SLEEPING

1. Sleep in cotton. Cotton is your best friend when trying to keep cool throughout a night’s sleep.
2. Avoid tight clothing.
3. Use fans.
4. Hack your fan for extra cooling.
5. Create a cross-breeze.
6. Take cold showers.
7. Try a cool compress.
8. Keep your bedroom unplugged.

Why Do We Get So Hot When We Sleep? The reason people “sleep hot” has a lot to do with design. Our core temperature drops by a couple of degrees during the night, shedding heat into the surrounding areas, and certain sheets and mattresses trap the heat and moisture around us.