CarbonetiX conducted an energy and water audit at the Ringwood Aquatic Centre at the end of 2008 as part of the Maroondah City Council’s greenhouse reduction strategy. During the audit the implementation of pool covers was recommended. The pool covers have a number of positive applications to an aquatic centre that will result in reduced operating cost and usually a better-managed environment.

Following our recommendations the council purchased and installed the pool covers during the middle of 2009. Since then CarbonetiX has been monitoring the gas bills to ascertain the actual savings achieved from this measure. This short report reviews the results up to date which has been a year (July 2009 to June 2010) since the Ringwood Aquatic Centre has begun using the pool covers.

In order to estimate the savings achieved a mathematical model was developed that correlated gas usage of the pool based on average temperature data from the Bureau of Meteorology, up until the time that the blankets were installed.

Using this model, the estimated gas consumption was then predicted based on weather data, for the months after installation of the pool cover. The graph below shows the results:

The graph shows little savings in the cooler months, but significant savings in the warmer months of November through to February. Based on 12 months of data (July 2009 to June 2010), actual gas use after the pool blankets were installed is 1,235 GJ lower than that predicted by the model. This represents a gas saving of around 8%.

The pool hall heating controller is set to maintain the pool hall at 28 degrees C. However temperature logging in August 2009 showed the pool hall temperature dropping to below 20 degrees overnight (see table below). Clearly the boilers cannot maintain the 28 degrees in cooler months. Any energy the boilers are saving on heating the pool water is now diverted to put more energy into heating the air in the pool hall. This is indicative of a pool that has:

• leaky pool hall
• No heat recovery on exhausted air
• An undersized pool hall heating system

In explaining why the pool blankets give large savings in summer and no savings in winter, we hypothesize that in summer that outside temperatures are sufficiently warm for the air handling system to easily maintain the temperature set point of 28 or 29 degrees overnight in the pool hall. Energy in heating the pool water saved by the pool blanket does not need to be pumped into heating the pool hall, leading to a significant gas saving.

However in winter, the boilers cannot maintain the pool hall at the set temperature. Any energy the boilers are saving on heating the pool water is now diverted to put more energy into heating the air in the pool hall.