Integrating a Reed Bed System
Building a home and trying to build an integrated water cooling, reed bed system. Location has sub-tropic climate (Wet-hot summer/Dry-cool Winter).
Max temp = 30 Celsius (Dew point = 20 Celsius, Min Temp = 15 Celsius)
Basic design principles(Check Attachment) :
1. First tank is 8KL, made with concrete and underground with open top. This tank is 3.5′ deep and top 1′ is gravel/media material. Water level will be at 3′. So 2.5′ height of just water and .5′ height of water + gravel. This tank will have multiple aerators at the bottom to create movement and also to continuously improve water quality.
2. 2nd tank is 20KL. Same configuration as 1st tank in terms of depth, gravel, aerators and other parameters.
3. Water is continuously rotated between the two tanks plus the aerators around the tanks keeps the water disturbed.
4. Heat exchange will happen at 20Kl tank which is effectively 85′ long. Inlet and outlet is 6″ PVC pipe and exchange happens through 16X1″ PVC pipe laid in parallel near the floor of the tank.
5. Air is continuously recirculated from home through this PVC pipe system with outside air mixed at variable rate(depending on outside temp). Dehumidifier may be added inline to improve RH. Dew point does not look like a concern based on location weather profile. Air exits from the highest point in the home and cold air enters from under floor vents.
6. Home construction style is SCIP/3D EPS so I consider good insulation. Going for sealed windows and double glazed on South/West facing windows(North Hemisphere) to minimize load.
7. Area to cool is 2800 sqft with 10′ ceiling.
1. Tanks have 28 KL of total water in the system at any point of time. 3-4% of water will be refreshed every day. Most of the water change will happen during operation time. 1-1.5% of water will be lost by evapotranspiration(plants) and evaporation. Rest will overflow to percolator.
2. Total energy to raise 1 Celsius temperature of water is 32.56 KWh. Think I will have between 5-10 Celsius margin before I get concerned. So that is around 150-300 Kwh of energy that can be transferred everyday.
3. Ground heat transfer, evaporation and water rotation should keep the water from heating too much. Also think during night time with continuous water rotation, water temp should reset. Night lows are close to 15 and if I can take water even close to 20 every night, I should be good for next morning.
4. Evaporation of few 100 Liter of water everyday will not be an issue as can be compensated with daily intake of treated greywater.
5. PVC as a heat exchanger is not traditional but copper will eventually react with the not perfectly clean water(Kill plants). Also this research (https://www.sciencedirect.com/science/article/pii/S2666016420300116) suggests that over time in recirculating systems the difference between PVC and metal is not substantial.
Decent livable environment. Not looking for 18 Celsius conditioned air but want the system to keep the home comfortable.
Would like to know the feasibility of the solution? The tanks will anyway exist as a way to have a tertiary water reservoir and maybe do some hydroponics on the top layer.
See attached image for high level design
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