This basically defeated the purpose of the new swimming pool and Bruvel set out to work out a low-cost way of maintaining a more desirable fresh water temperature, as existing refrigeration systems for water are expensive both to install and to run.
This is a common phenomenon for people living in the areas that get really hot. A large and shallow Penrith swimming pool would be an obvious example, considering the record temperature it experienced this summer. The heat from the sun and the outside temperature is by far what heats up the temperature of the water the most. Heat transfer from the sun occurs mainly at the water’s surface, which is why a smaller but deeper pool typically stays quite cool. During the nights, some of the waters heat is transferred to the cooler temperature of the air, but this also occurs mainly at surface level, so much of the heat ends up being retained. This results in a slow but steady increase in temperature over days and weeks.
According to ABC Radio Darwin, the theory behind Mr Bruvel’s invention is to create more surface area for the water during the coolest part of the night, so that more heat can dissipate into the air, resulting in a lowered overall temperature. How does he achieve this? Simply by installing pumps that spray water over the surface of the pool between 2:30 and 5:00 in the morning. As the millions of water droplets fly through the air, their heat is transferred to the outside air before they re-enter the pool.
The word “simply” however, can be quite misleading. Getting the size of the water droplets which are produced by the jets right is critical to the success of the operation, ABC Radio Darwin reports. The relationship between surface area and volume determines how effective the heat transfer will be. The smaller the droplets, the better, but make them too small and they may be carried away by the wind.
And does it work? Mr Bruvel has managed to reduce the temperature of his pool by as many as five or six degrees. He reports that the pool is exposed to the scorching sun all day and used to get to 32 degrees. Now when he times the system to start early in the morning when the ambient temperature is the coolest, Mr Bruvel tends to bring his pool temperature down to about 28 degrees.
Couldn’t he just erect a shade sail to block out the sun? For many people this option would be the cheapest and most straight forward solution. But Mr Bruvel enjoys swimming under the stars at night and doesn’t want to dismantle a heavy shade sail every time.