For our project on sustainability we decided to look at ways in which to save water whilst showering. The two main issues focused on are the wastage of water and heat before the user has even begun to shower and opportunities, during the shower, in which the water need not be running. Can we make significant reductions to the environmental impact of showering, without implementing considerable behavioural change?
To decipher if simple sensors and coding can make a difference, a survey was taken outlining the showering behaviour of the average person. From this survey it was discovered that the average shower takes 48.1 seconds to get warm, taking in account the activities these people do whilst waiting for the shower to heat up, this means that the water is running, already hot, for 32.6 seconds unnecessarily. Once in the shower the participants were spending 2.1 minutes away from the water; again, letting in run without need.
Taking an average ml/s reading of various showers – a shower runs 77ml of water per second. From various energy and water supply companies it was found that 1kWh costs an average of 18.01p (in the Bristol area) and 1 litre of water will cost you 0.3p. Knowing that a 7.5kW shower uses 1.25kW in 10 minutes, it is possible to calculate just how much water and energy is wasted when we shower.
Over a year (12.2*365 = 4453) 4453 LITERS of water and (0.33*365 = 120.5) 120.5kWh of energy are being wasted by just ONE person wasting water whilst showering
By halting the flow of water once it has reached the desired temperature, alerting the user that the shower is ready and disallowing the stream to continue when no one is underneath the showerhead; we can significantly reduce the amount of energy and water wasted whilst showering.
We endeavoured to create a shower head that reduces energy and water consumption. To achieve this our product would stop the flow of water once it has reached the optimal temperature and only release water once a person is detected to be underneath the shower head.
This is the first look at our circuit. There are 4 main components;
- Solenoid valve
- Ultra-sonic sensor
- Relay switch
The solenoid valve is the part that can control the flow of water, once power is passed through the component the valve opens. As ours is a 12v solenoid (Arduino Uno’s use 5v), we also plugged in a separate 12v power supply. The relay switch protects the Arduino from the extra power but bypassing it straight to the solenoid, this means that it does not affect any of the other components. Thus, controlling the solenoid valve without jeopardising the rest of the circuit. An ultra-sonic sensor can detect the distance of the nearest object, informing the s product that the user is within range. Finally, the thermistor measures the temperature of the water, which kickstarts the code.
Here you can see our circuit working (in this video we have used a red LED to represent the solenoid valve for a clearer display). The valve stays open as the shower turns on – this is to allow time for the water to warm up before requiring the user to stand underneath it (no one wants to stand under freezing cold water). Once the thermistor recognised the required temperature has been met, the solenoid valve closes. After this point the water will only flow if the user is detected below the ultra-sonic sensor. Therefore, you can see in the video that the valve opens and closes as motion passes past the sensor. If the water runs cold again, the thermistor will sense this, the valve will open and water will flow.
https://www.youtube.com/watch?v=u1DxXLQrffU This shows the same circuit with the solenoid added, if you listen carefully you can hear the valve opening and closing.
In our display unit we angled the ultra-sonic sensor to represent the placement of the sensor in the actual product, which would be just below the shower head.
At this stage we had the all of the components working, apart from our solenoid valve was reading the wrong way around – we have a video of this, with the intention to switch the code later to have the correct solenoid function https://youtu.be/M8W7rpvQq4k
From this point we needed to change the code regarding the distance of the ultra-sonic reading, the solenoid function and the temperature gage (purely just for ease of presentation purposes).
Here is a flow chart of our code and the code itself
Seeing as the most power consuming part of our circuit is the solenoid valve, we will base our calculations upon this. The Arduino itself and the sensors do not take up a lot of power, therefore, in comparison to the solenoid valve they are negligible.
From looking at the specs on the solenoid valve we are using, we can see that it takes 8.5 watts of power. The solenoid valve only consumes power when the valve is open (when someone is standing under the shower and when the water is running cold)
Taking results from the earlier background research we can analyse whether our product will save more energy than it consumes.
Average shower time – 10mins
Average time away from water – 2.1mins
Average time under water – 7.9mins
Average heating up time – 48.1s
Time spent with the solenoid open = (7.9*60) +48.1 = 522.1 seconds of 8.5 watts
Energy = Power x Time. Therefore 8.5 * 522.1 = 4437.85 Joules (J)
4437.85J = 0.0012327361111 kWh or 1.23×10^-3 kWhs
The wastage we are saving (in energy alone) is 0.33kWh per shower – therefore, adding in the energy cost of our product – it will save you 0.329kWhs per shower, 120kWhs per year and 480kWhs per household per year
To properly analyse the data we took from our earlier survey, we took a look at two specific candidates; one that wasted a lot of water and one that didn’t waste much at all. As this survey was anonymous the names have been fabricated.
Time taken for shower to warm up: 30 seconds
Activity done whilst waiting: Phone scrolling for 1 minute
Shower length: 17.5 minutes
Time spent out of the water: 5 minutes
Total time of water flow wasted: 5.5minutes (330 seconds)
77ml/s. (77*330 = 25410ml) 25.4l of water wasted per shower. Showering uses 1/480kWh in energy per second. (330*(1/480) = 0.69kWh per shower.
Year-long: (0.69*365 = 250.9kWh) (25.4*365 =9271l) (250.9*(18.01p per kWh) = 4518.7) (9271*(0.3p per litre) = 2781.3) (2781.3 + 4581.7 = 7363)
In a year, Chloe will save 259kWhs of energy, 9271 litres of water and £73.63 – Very cost and energy effective
Age: 45 – 54
Time taken for shower to warm up: 120 seconds
Activity done whilst waiting: Brush teeth 2.5 minutes
Shower length: 9 minutes
Time spent out of the water: 0 minutes
Total time of water flow wasted: 30 seconds
77ml/s. (77*30= 107ml) 0.12l of water wasted per shower. Showering uses 1/480kWh in energy per second. (30*(1/480) = 0.06kWh per shower.
Year-long: (0.06*365 = 22.8kWh) (0.12*365 =43.8l) (22.8*(18.01p per kWh) = 410.6) (0.12*(0.3p per litre) = 0.036) (0.036+ 410.6 = 410.6)
In a year, Jackie will save 22.8Kwh of energy, 0.12 litres of water and £4.10 – Not very cost and energy effective
Adding extra energy saving features to a shower head can dramatically reduce the environmental impact of taking a shower.
We would look to build this product into excising electric shower units; as they already contain solenoid valve and a power supply, only the shower head . Again, reducing the energy and material consumption of the product. It uses considerably less energy than the vast amount saved, especially in a house-hold which uses the shower 4 time daily.