UWE Bristol Engineering showcase 2015

Rhys Jones-Mathias
Beng Mechanical Engineering
Project Supervisor
Dr Aruna Palipana
Harnessing Energy from draining the pool
Energy Harnessing and Recovery in Gymnasiums
Pool water is replaced every seven to ten days meaning that around 562500
Litres of water at 29°C drains out from the building. It may be possible to
recover some of that heat using heat exchangers. However the time in which
the draining would take place, outside of the facilities operating times,
means that there may not be a demand for preheated water on the site.
height of the water changes as the pool drains.
As the height decreases the volume flow rate and therefore the mass flow
rate also decreases.
Figure 9 shows how the power produced will change as the height of the
water falls
1.2
1
Effect of Change of height on Power
0.8
Height of Water (m)
0.6
The energy produced based on an
average power output of 294.2 W is:
PPPPPPPPPP . tttttttt
EEEEEEEEEEEE kkkkk =
1000
0.4
0.2
0
700
600
500
400
300
200
100
0
Power (W)
Recovering Waste heat from grey water
Heat exchangers are used to transfer heat from one medium to
another. For this application the heat exchanger could be used
to transfer heat from the greywater from the showers to pre
heat the water which is going to be used in the showers.
The main disadvantage of the parallel flow heat exchanger is
that the cold fluid exiting the heat exchanger can never
exceed the lowest temperature of the hot fluid and tends to
the temperature of the hot fluid leaving the heat exchanger.
This is a distinct disadvantage if the purpose of the heat
exchanger is to raise the temperature of the cold fluid.
Pre heated warm,
21.23°C
Max Temp. leaving
the shower at 45 °C
Greywater in, 28 °C
Mains Water
entering, 12 °C
As a result of
observations and
calculations it is
possible to conclude
that the temperature of
the water entering the
heat exchanger will be
raised from to 21 °C
Project summary
An investigation was undertaken into David Lloyd
Leisure Cardiff to identify current energy saving areas
of the facility where energy is available and could be
harnessed. Examples of where energy had the
potential to be harnessed were elliptical machines in
the gymnasium and the spin studio. Another aspect
of the study was to identify where energy was being
wasted and could be recovered. Areas that were
considered were the hot tub and showers.
Project Objectives
Identify areas in the chosen gymnasium facility where
energy could be harnessed, with greater emphasises
on recovering waste heat energy as a result of the
previous research;
Identify current energy saving methods;
Identify technology which could harness this energy;
Identify how much energy could be harnessed;
To look into the ways in which the chosen gymnasium
reduces their energy consumption and possible
technology which could be implemented to reduce
their energy costs.
Project Conclusion
Overall it is difficult to harness and recover a
meaningful amount of energy although both are
possible. The high initial costs mean that the
outcome of this study show it would not be
financially viable at this time. For example, time to
pay back the capital cost of retrofitting the spin
studio would most likely be longer than the service
life of the equipment. However, as fossil fuels reduce
further, there will inevitably be an increase in the
amount of research and development into energy
harnessing and recovery. This will hopefully lead to a
reduction in the cost of the technology which is
currently available.
Figure 8
Greywater out, 16 °C