Heat pumps have transformed the environmental control management of modern swimming pools?
First developed three decades ago, heat pump technology is the super hero of environmental control that has simply transformed the management of modern swimming pools.
Such is the level of sophistication that now, 30 years on, for each kW of electrical energy used to operate the latest dehumidification units from industry pioneers, Calorex, up to 3.5 kW of energy are recovered ?the only humidity control system which recovers more energy than it uses.
On a typical municipal leisure centre with a 25m learner pool, a heat pump based system can save over 250 tonnes of CO2 emissions per annum compared to a recuperator based air handling unit.
In this energy-conscious, budget-dominated age, it would take a brave pool operator, or a rather aged ostrich, to bury their heads in the sand, when it comes to a quick fix solution that will not only save energy, but will also reduce running costs and all for a minimal capital outlay that will see pay-back within a matter of years.
Local authorities and leisure operators are under more pressure than ever to demonstrate efficient and effective energy efficiency with a backdrop of reports that suggest current atmospheric levels of the greenhouse gases, carbon dioxide and methane, are higher now than at any time in the past 650,000 years. Another recent study reports that for the last 150 years, sea levels have been rising twice as fast as in previous centuries.*
Recreation and leisure is one of the top three in the highest carbon emissions league table according to the Carbon Trust, the body that provides free, practical advice to business and public sector organisations to help reduce energy use.
The Carbon Trust says business has the opportunity to take a new approach to delivering products and services to consumers in order to substantially increase carbon emissions reduction.
Taking a pro-active lead, British manufacturer, Calorex, is a privately owned company that is constantly striving to improve the carbon footprint for businesses both within the recreation sector but also to a broad scope of business sectors from manufacturing to information technology. Employing around 120 staff at its Essex base Calorex has traded and grown successfully for more than 25 years. The company provides the very latest heating and ventilation heat pump systems for indoor and outdoor pools and has a world-wide customer base to prove it.
Using heat pump technology to maximise energy efficiency is core to Calorexâs product range and close to the companyâs heart with company figurehead, Tony Bowen, the current president of the UK Heat Pump Association.
Calorex systems have been successfully installed up and down the UK and all over the world where pool managers tackle the perpetual challenge of balancing the need for high water temperatures and the excess of humidity and condensation caused by evaporation from the pool surface.
Unchecked, not only does this cocktail create an unpleasant environment for swimmers and poolside staff, if moisture levels remain uncontrolled, the building fabric and its content will suffer untold damage.
Much more than just a question of poor housekeeping, the consequences of not controlling humidity in swimming pools is potentially catastrophic. Testimonies to this include such recent tragedies as the Moscow pool disaster that claimed more than 27 lives with over 100 injured.
A typical leisure centre pool can contain up to a million litres of water heated to around 30Â°C. Water evaporates from the surface at a rate of hundreds of litres every hour. Evaporated water needs to be removed or it will turn to condensation that will immediately start to cause problems.
Pre-heat pumps, that valuable energy would have just been expelled to the outside atmosphere. Heat pumps cleverly provide the means of recovering that energy. Air is passed through the evaporator, a finned coil, where it is continuously cooled. The water vapour is condensed to give up its latent heat and runs away as water.
At normal pool temperatures, 2 kWh of latent heat is recovered for every three litres of water vapour condensed. The air temperature has been lowered by the removal of sensible heat to enable the dehumidification process to proceed and both the sensible and latent energy come together in the refrigerant gas. This is now raised to a higher temperature by the compressor and used to heat the pool water as well as the pool air.
When the humidity rises above the target level, a compressor is switched on, together with the integral heat pump circuit and the heat recovery dehumidification process starts. Latent and sensible energy available in the moist air is recovered and returned to the pool water and air, via the built-in heat exchangers.
If the recovered energy is insufficient to meet the water and/or air heating load, the unitâs integral low pressure hot water heat exchangers redress the balance.
As an added bonus, the system cleverly takes care of the pool environment by incorporating automatic fresh air control. Introduction of fresh air that also passes through the heat recovery process at up to 70% of recirculated air is kept to a minimum to satisfy occupancy and dilution demands, reducing to virtually zero during unoccupied periods. Should natural solar gain increase the air temperature of the pool hall, the units can even provide air conditioning by dissipating unwanted heat into the exhaust air.
Off The Shelf
A thermodynamic heat-recovery dehumidifier comes complete with a control panel, air temperature and humidity and water temperature sensors, pool air and pool-water heat exchangers ?in fact everything necessary to control the pool environment, and it will fit into a plant room space substantially smaller than that needed for a conventional system.
Because the complete unit is in one insulated case and has been factory tested and set-up, it is very simple to fit. All controls and sensors are inside, and it only requires a three-phase power supply, connection to the LPHW headers, connection to the pool water circuit, condensate drain and duct connections. A commissioning engineer is provided at start-up to ensure all is well.
When the overall costs of using a heat-pump, heat-recovery dehumidifier are considered, it is important to remember that heat-pump dehumidifiers will recover sensible and latent heat that will be returned back into the pool water giving an efficiency of 300% to 350%. Passive units cannot do this, offering only 50% to 60% when external air temperatures are favourable.
Modified office AHU units are far less efficient than dedicated heat pump units in swimming pool heat recovery. They are also not designed for a swimming-pool atmosphere, which is reflected in their operating life. In fact, dedicated swimming-pool equipment will always give better service than something simply âcobbled together?for individual jobs.
Systems for wet leisure environments are specialist because they need to be designed to tolerate the harsh environment of a pool hall and its associated water treatment chemicals, such as chlorine. All components have to be specially selected resulting in extensive use of coatings, treatments and plastics.