Many people love summers but most hate the heat. Therefore, air conditioners have been one of the most favourite electrical appliances in the dog days of summer. Nonetheless, air conditioners consume enough electricity and manufacturers have been fiercely fighting to diminish the electricity consumption of air conditioners.
If you notice carefully, you’d find many air conditioner advertisements that focus on low electricity consumption. It is important because saving energy is not only important for environmental sustainability, but electrical appliances also need to be light on the pocket.
Now, if we say air conditioners can run without electricity too, will you be impressed? Definitely! Meet Aaswath Raman and his colleagues of Stanford University who have built an air conditioner that does not need electricity to cool the surroundings.
But before we actually talk about this awesome device, let’s see how much electricity does an AC consume?
Presently, AC models of various ratings are available. The better the rating, the better it saves the energy. The low-rated model usually consumes more electricity. A regular Air Conditioner used for residential purpose has a 5,500 – 14, 000 BTU/hour range. During peak summer, the climate is hot, and a higher-rated AC is recommended to purchase by experts.
The electricity charges are based on the units of consumption, usually, 1 unit of electricity is consumed when the energy consumption equals 1 Kilowatt hour. Here is a simple illustration of energy consumption by air conditioners:
To understand, let’s say 10 quantity of 100 Watt bulbs when switched on for 10 hours consumes 10 X 100 W X 10 H = 10, 000 watt hour = 10 kilowatt hour = 10 units. Similarly, an AC with 2,000 Watt power input if operated for about 8 hours per day will consume: 2,000 watt x 8 hours = 16 kilowatt hour = 16 units
This is enough electricity for a common household. But, in office facilities and big buildings, the electricity consumption is much higher. Simultaneously, the need to save electricity is more applicable too.
With 15 % of electricity in U.S. buildings being dedicated to keeping things cool, Raman’s cooling method is going to create a real dent in energy consumption on a global scale. That is also why an air conditioner that runs automatically, without consuming electricity is good news in many ways.
The interesting technique which Raman’s device employs is called radiative cooling. It is the same method by which our planet loses heat to space. The method’s main point is the fact that Earth’s atmosphere lets a very specific subset of heat pass through it by radiation. The subset is of the far-infrared wavelengths ranging from eight to 13 microns. Any device that can reflect the ambient heat and light in that range of wavelengths will actually shoot heat through back into the outer space.
Generally, it is believed that radiative cooling works best at night. But since that is during off-peak hours, we need something that can work during broad daylight. Raman and his team have been in discussions because they have constructed a radiative cooler that works during the day when energy consumption is at its peaks.
Raman’s radiator is known as the photonic radiative cooler. It is built with seven alternating layers of silicon dioxide and hafnium oxide stacked on a reflective inner layer of silver.
The seven layers are of a different, precise thickness that range between 13 and 688 nanometers. A nanometer is the unit of spatial measurement that is 10-9 meter, or one billionth of a meter. The precision thickness and all of the layering allow the material to reflect about 97 percent of sunlight and heat that falls on it. The device also sends the infrared light at the atmosphere’s transparency frequency back to space.
Raman has already tested an experimental cooler on a rooftop in Stanford, Calif., and the device has worked. The photonic radiative cooler successfully kept the temperatures roughly 9 degrees Fahrenheit lower than the ambient air temperature. This may seem to be a very modest temperature drop, but the advantage is that it didn’t require any electric energy.
Raman’s cooler was of the size of a beanbag toss board. Hence to work in real conditions, the process would have to be adjusted and modified to work on buildings. Moreover, hafnium and silver are quite expensive; therefore we may need some other alternative materials.
The cooler works best when it is placed on a rooftop with a clear view of the sky, so it may not probably completely replace air conditioning devices currently in use. Also, during peak summers and in places with high temperatures, people will look for more temperature drop than just nine degrees.
Raman’s device may not be perfect in all regards, but it has proved that it’s certainly possible to save enough of household expenses in energy consumption. That is really good news because when applied to global scale, the acceptance of such an electricity-free cooler could mean saving billions of dollars on energy expenses.
Moreover, since it just needs to be placed on the rooftop to shield the facilities from ambient heat, there is not much invasion to our privacy as well. It also doesn’t generate any greenhouse gases, which is a good sign for environment protectionists. This is particularly important because greenhouse gases affect the Ozone layer that saves us from Ultraviolet Lights negatively.
Raman’s experimental AC is a new chapter in both air conditioning and energy efficiency domains. But we may need to wait for some days to get a practical version of the cooler applicable in day to day life. But that doesn’t make the achievement weaker. We know that there is a way to cool our homes and offices that is completely natural and needs no electricity. That is why Raman’s cooler is really cool.