case study: Devon Cliffs

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The Problem

Bourne Leisure wanted to save energy and reduce carbon emission, however the quality of the water in the pools and the health and safety of their customers was paramaount inthe decision making process. Bourne Leisure approached APDS to help them save money on energy by examining and reporting on the control philosophy for their pools. It is well understood that slowing a motor via an inverter on a variable torque application leads to savings on energy. Using their extensive knowledge of pool filtration systems and understanding the periods of heavy usage APDS identified areas where savings could be achieved.

The Solution

APDS recommended fitting inverters to the pumps feeding the pool filters. These operate by trapping dirt and debris in the sand filter and returning clean water back to the swimming pool. This is achieved by pumping pressurised water through a large cylindrical chamber filled with filter sand. The slower you pump the water through (within reason due to the pump curve) the better the filtration. In the past this was achieved by reducing the diameter of the feed pipes and introducing a control valve to limit the flow. In working out the flow rate required you have to consider the size of pool and the use. Leisure pools of a certain depth need to be turned over at least once every 1½ hours. Combine this with the maximum number of bathers the filter was designed for and peak occupation you can calculate speed reduction. Further changes in speed can be made at night when the pool is empty. Energy costs and varying rates often mean that maximum filtering can be done overnight when rates are lower.

 

The Result

The savings per 18.5kW pump were £4,899 per annum, giving a payback period of under 6 months.
The actual savings exceeded those predicted in the energy report as the motor speed could be accurately mapped to pool utilisation.

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