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UWE Bristol Engineering showcase 2015

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Rhys Jones-Mathias<br />

Beng Mechanical <strong>Engineering</strong><br />

Project Supervisor<br />

Dr Aruna Palipana<br />

Harnessing Energy from draining the pool<br />

Energy Harnessing and Recovery in Gymnasiums<br />

Pool water is replaced every seven to ten days meaning that around 562500<br />

Litres of water at 29°C drains out from the building. It may be possible to<br />

recover some of that heat using heat exchangers. However the time in which<br />

the draining would take place, outside of the facilities operating times,<br />

means that there may not be a demand for preheated water on the site.<br />

height of the water changes as the pool drains.<br />

As the height decreases the volume flow rate and therefore the mass flow<br />

rate also decreases.<br />

Figure 9 shows how the power produced will change as the height of the<br />

water falls<br />

1.2<br />

1<br />

Effect of Change of height on Power<br />

0.8<br />

Height of Water (m)<br />

0.6<br />

The energy produced based on an<br />

average power output of 294.2 W is:<br />

PPPPPPPPPP . tttttttt<br />

EEEEEEEEEEEE kkkkk =<br />

1000<br />

0.4<br />

0.2<br />

0<br />

700<br />

600<br />

500<br />

400<br />

300<br />

200<br />

100<br />

0<br />

Power (W)<br />

Recovering Waste heat from grey water<br />

Heat exchangers are used to transfer heat from one medium to<br />

another. For this application the heat exchanger could be used<br />

to transfer heat from the greywater from the showers to pre<br />

heat the water which is going to be used in the showers.<br />

The main disadvantage of the parallel flow heat exchanger is<br />

that the cold fluid exiting the heat exchanger can never<br />

exceed the lowest temperature of the hot fluid and tends to<br />

the temperature of the hot fluid leaving the heat exchanger.<br />

This is a distinct disadvantage if the purpose of the heat<br />

exchanger is to raise the temperature of the cold fluid.<br />

Pre heated warm,<br />

21.23°C<br />

Max Temp. leaving<br />

the shower at 45 °C<br />

Greywater in, 28 °C<br />

Mains Water<br />

entering, 12 °C<br />

As a result of<br />

observations and<br />

calculations it is<br />

possible to conclude<br />

that the temperature of<br />

the water entering the<br />

heat exchanger will be<br />

raised from to 21 °C<br />

Project summary<br />

An investigation was undertaken into David Lloyd<br />

Leisure Cardiff to identify current energy saving areas<br />

of the facility where energy is available and could be<br />

harnessed. Examples of where energy had the<br />

potential to be harnessed were elliptical machines in<br />

the gymnasium and the spin studio. Another aspect<br />

of the study was to identify where energy was being<br />

wasted and could be recovered. Areas that were<br />

considered were the hot tub and showers.<br />

Project Objectives<br />

Identify areas in the chosen gymnasium facility where<br />

energy could be harnessed, with greater emphasises<br />

on recovering waste heat energy as a result of the<br />

previous research;<br />

Identify current energy saving methods;<br />

Identify technology which could harness this energy;<br />

Identify how much energy could be harnessed;<br />

To look into the ways in which the chosen gymnasium<br />

reduces their energy consumption and possible<br />

technology which could be implemented to reduce<br />

their energy costs.<br />

Project Conclusion<br />

Overall it is difficult to harness and recover a<br />

meaningful amount of energy although both are<br />

possible. The high initial costs mean that the<br />

outcome of this study show it would not be<br />

financially viable at this time. For example, time to<br />

pay back the capital cost of retrofitting the spin<br />

studio would most likely be longer than the service<br />

life of the equipment. However, as fossil fuels reduce<br />

further, there will inevitably be an increase in the<br />

amount of research and development into energy<br />

harnessing and recovery. This will hopefully lead to a<br />

reduction in the cost of the technology which is<br />

currently available.<br />

Figure 8<br />

Greywater out, 16 °C

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