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