As the global agenda now has turned to reducing CO2 and supporting/commercializing CO2 credits,
we need to address the carbon foot print of WaterStillar
Calculating carbon footprint
Carbon footprint savings for WaterStillar Wall
The carbon footprint when it comes to heating bathing water electrically, is the same as any other directly heated water boiler. So, we encourage to use solar electrical power to run the Wall system.
A Wall system will produce average 15 liters drinking water average per day. Max is 22 liters.
If we pick a medium scenario (see Tapp reference) each liter will save 250 grams of CO2 when it is replaces bottled water. Over 20 years that amounts to 27.375 kgs of CO2 if the bottled water is tapped locally. If it replaces bottled water that comes from far away, the number is 69.314 kgs
Carbon footprint savings for WaterStillar Family
The carbon footprint savings when a conventional heater is being replaced by a solar collector, will therefore vary depending on where our systems are put up. The 2022 version of WaterStillar Family has a collector that will give 2.619 kWh average per year on 38. latitude (Athens). This number is tested and confirmed by Solar Keymark and a direct conversion of the EU average CO2 is 334 grams will mean (2.629 x 334) app 875 kg of CO2 saved per year or 17.500 kgs in the expected lifetime of 20 years. In Greece the actual number is currently 452 grams, so a Family system in Athens would then save some 23.675 kgs of CO2.
Then a Family system will produce 15 liters drinking water average per day. If we pick a medium (see Tapp reference) scenario each liter will save 250 grams of CO2 when it is replaces bottled water. Over 20 years that amounts to 27.375 kgs of CO2. If it replaces bottled water that comes from far away, the number is 69.314 kgs
Example: Athens, Greece and we replace branded water from France: 92.989 kgs of CO2 savings.
Carbon footprint savings for WaterStillar Works
Assumptions from an actual case in the Middle east (extreme case where oil is used for energy production (= worst case scenario?)
3 year contract
Average monthly production: 351 pcs 5 gallon tanks equal 6.669 litres/month and 222 litres/day
WaterStillar® system with 5 units with electrical supplement heating for nighttime.
Conversion factor oil/CO2: 2,7619
Conversion factor oil based production of electrical power: 1 kwh = 900 gr/ CO2
Average oil consumption for manufacturing/transport/waste pr litre of bottled water = 0,25 litre
Bottled water calculations
3 years production total ((365 x 3) x 222 litres): 243.090 litres
Fossil fuel related to similar amount of bottled water is (243.090 x 0,25 litre): 60.772 litres
Conversion to CO2 is (60.772 x 2,7619): 167.848 kg
WaterStillar Works emissions
During 7-9 hours of daylight the system will be running at 90C and produce between 80-110 litres.
During nighttime (16 hours) the system will be set out to run at 75C-80C to meet the desired production rate, in this case app 100-125 litres.
Maximum electricity consumption during nighttime in 16 hours will be max (16 hours x 2 kwh) 32 kwh – but will most likely be less since the system is thermostat controlled. We assume average is between 20 to 28 kWh – for this calculation we decide 25 kwh.
The electrical consumption for the solar pumps is app 5-10 watts pr hour – or average app 200 watts pr day. This number is so small that it is covered by the assumed the heating energy.
Each KWH produced by using oil in a relatively new plant emits app 900 gr of CO2. This means worst case that daily the WaterStillar production is causing (25kwh x 0,9 kg) 22,5 kgs of CO2
Under the 3 year contract this means ((365 days x 22,5 kgs) x 3 years): 24.637 kg of CO2
All in all under these assumptions
CO2 savings on a 3 year contract: 167.848 – 24637 = 143.211 kgs of CO2 or app 500.000 kgs in 10 years
Calculating the carbon foot print is a rather complicated thing to do. All calculations relies fullt in the assumptions used and in each case in real life, the number will vary.
Example: For WaterStillar Family we know the average yearly solar collector output for the 38. latitude (Athens) since that is proven and tested data by Solar Keymark for that collector in that place. But if the system is placed in southern France, these numbers will change and another CO2 saving will be the actual one. So, the below is our best guess.
Assumptions related to heating bathing water
The carbon footprint for a kWh produced in the world varies. Denmark has the worlds lowest emission of 135 grams per kWh produced, but the EU average is 334 grams. USA's emission is slightly higher 385 grams, whereas the world average is 475 grams.
We are promised that emissions will go down over the next years, so the savings would therefore change for that reason. And yes, some owners will not use all of the hot water, because their children move out in the course of 20 years. And yes, some will have a more efficient heating thechnology for the hot water - but still, the collectors used will collect the energy.
Assumptions related to bottled water
The carbon foot print for bottled water is created by 1) the treatment of the water before being tapped; 2) transportation, storage and cooling of bottles; 3) the plastic bottle itself and 4) waste management of plastic bottles. Transportation and waste are the biggest footprints.
Green America: https://www.greenamerica.org/blog/truth-about-bottled-water