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Gas bill shock triggers revolution in energy-efficient aquatic centre design

As Australian councils struggle to pay sky-high gas bills to heat and cool their aquatic centres, pressure is building to find cheaper and less carbon-intensive ways to keep these treasured community facilities open.

Australia might be a leader on building energy performance but one niche building type appears to have fallen through the cracks: the local aquatic centre.

According to experts, historically cheap gas prices and the absence of a carbon tax has spawned a fleet of energy-hungry aquatic facilities across the country. These facilities, which typically consist of indoor pools and other functions such as gyms and cafes, can consume up to seven times more energy per floor area than the average commercial office building.

This could soon change, with councils now facing enormous bills thanks to rising gas prices that aren’t expected to decline.

One source from a metropolitan Victorian council told The Fifth Estate that the council’s energy bill had increased by more than 60 per cent compared with 2014-2017 averages.

Fortunately, there’s growing evidence to suggest it’s possible to design and retrofit aquatic centres to dramatically improve energy efficiency.

Northern Environmental Design director Jonathan Duverge, whose PhD focussed on energy efficiency in aquatic centres, says Europe leads the way on aquatic centre design.

Higher energy costs have prompted the design of better performing buildings, he explains, with, for example, minimal use of glass.

“It’s very rare to see an aquatic centre with floor-to-ceiling glass surrounding it… Europe is really looking at the design.”

By contrast, large swathes of glazing are common in Australian aquatic centres. While it might look attractive, sky lights and floor-to-ceiling glazing attracts condensation. If not managed correctly, glare can also be dangerous inside an aquatic centre.

Steel framing is also common in Australian aquatic centres, creating thermal bridges and attracting condensation and rust.

Duverge says that in Australia it’s rare for designers to consider how much energy the facility is going to use – it’s all about making them “tall and shiny”.

It doesn’t help that fully-glazed domes are recognised by the industry as tender-winning designs, he adds.

He says also people don’t understand the effect of evaporation and heat loss that occurs in an indoor pool.

“They treat it as an office building.”

He says the evaporative effect has a big impact on energy consumption, but is rarely taken into consideration.

“I think people just try to do calculations in terms of heating but neglect the effect of evaporation. That’s not really accurate.”

Another common problem is that aquatic centre staff are not trained or don’t understand how HVAC systems work, opening windows and doors when it becomes too hot rather than adjusting the HVAC.

Duverge is seeing change in the industry as councils start to feel the financial and ethical pressure, with many declaring a climate emergency and looking for opportunities to decarbonise their operations.

Capturing heat energy

For RMIT senior industry fellow Alan Pears, an energy efficiency expert who’s been looking into the energy performance of aquatic centres since the 1990s, the key issue for aquatic centres is that they flush out enormous amounts of heat energy that is costly to produce.

Most of the thermal energy going into an aquatic centre is used to heat the air around the pool, followed by the pool water itself which is heated to around 27-29 degrees Celsius. The warm water from the pool evaporates, absorbing large amounts of energy, producing water vapour and making the pool facility hot and steamy.

Air extraction fans are required to suck out the hot, humid air and the energy it contains at an astounding rate. Air equivalent to four to 10 times the volume of the building is exhausted and replaced by outdoor air every hour.

The good news is there’s a tried and tested technology that can capture and upgrade this escaping heat energy for another use – the heat pump.

How it works

A heat pump is an electrical device that extracts heat from one place and transfers it to another. Refrigerators and air conditioners are both heat pumps ­but only for cooling. The heat pump cycle is fully reversible, and can provide heating in winter and cooling in summer.

Unlike traditional heating equipment that only generates heat, the pumps extract heat from the environment – as per the laws of thermodynamics, where even cold air, heat or other materials actually contains a lot of heat energy.

In an aquatic centre, a heat pump is particularly attractive as it is able to capture the large amounts of waste heat energy from humid exhaust air and “pump” it back into the pool, all while using a relatively small amount of electricity.

This all ends up far cheaper because, although the price per unit of energy is more than gas, a heat pump is much more efficient than a gas boiler in this kind of setting.

A heat pump’s energy efficiency is measured by its Coefficient of Performance (CoP), which is the amount of heating or cooling provided by a heating or cooling unit to the energy consumed by the system. A top-of-the-line heat pump can have a CoP as high as 9.5 to 11 (950-1100 per cent), compared with traditional gas boilers that have an expected efficiency of around 50-75 per cent.

The efficiency of heat pumps increases again if used as an integrated building-wide system for both heating and cooling. This makes the technology even more attractive for aquatic centres because different spaces and pools are heated at different temperatures. For example, a gym needs to be at a comfortable temperature for exercising, while a pool in the same centre needs to be about 30 degrees.

Pears says that once you start running the numbers, heat pumps “look pretty good,” with lower maintenance and running costs offsetting the higher capital costs over time.

Councils turn to ammonia heat pumps

SmartConsult renewable energy consultant Derek Harbison believes low-charge ammonia heat pumps are a good option for those aquatic centres considering the shift away from gas.

Harbison, who has been acting as an intermediary between councils and the refrigeration industry, says the technology is proven and already used in other building types in Australia, such as commercial buildings and cold stores. A key benefit of these systems is that they rely on a “natural” refrigerant that doesn’t contribute to global warming.

Critically, he says a fully integrated and optimised system has the potential to make an aquatic centre 80 per cent more efficient when compared with a comparable gas system.

Harbison has been approached by multiple councils from Victoria and NSW interested in alternatives to gas for heating and cooling their aquatic centres.

Rooftop solar and a tight thermal envelope

Heat pumps are only part of the story. Once electricity is needed to run heating and cooling, rooftop solar and battery storage becomes an appealing proposition, especially given the vast roof space available on an aquatic centre.

A tighter building envelope will also require a smaller capacity heat pump, meaning that an optimised facility will make a heat pump look more attractive upfront. Although it’s possible to retrofit heat pumps into aquatic centres, the best results undoubtably come from a facility designed for high thermal performance.

Smaller pools have problems, too

Although the biggest pools are run by councils, similar energy-performance problems are experienced in smaller home indoor pools and indoor pools in apartment blocks.

Rehabilitation pools and healthcare facilities have an even tougher time because their pools are run at high temperatures.

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