An average family of 5 uses 28,000 gallons of hot water a year. It requires a lot of energy to rise water temperature, whether you are using gas or electricity, in both cases, water heating accounts to more than 40% of your utility bill. So by installing a solar water heater, you can reduce your bill by up to 40%. It does not cost any expensive item to build a solar hot water system. With my easy to use step by step guide, you will be able to build your new solar water heater in less than 250$ in your backyard. You will be able to recover this amount in less than 6 months by savings from your utility bill. In addition to this, you are helping the environment by fighting against the issue of global warming.
Solar Hot Water System
It consists of a solar heater panel (1), which absorbs heat from sunlight, a hot water storage tank (2); typically 90 gallon capacity is enough to store hot water for the whole day of an average family, an expansion tank (3), a pump that circulates hot water (4) and a piping network with valves that joins all of these components together.
Let’s get started
We will first construct a solar panel. You need following items for the
construction of a solar panel.
- Wooden blocks (20$)
- Plywood (5$)
- Thin Aluminium foil (5$)
- 10mm diameter copper piping (approx. 10m length) (20$)
- Copper tube cutter (5$)
- A propane torch, solder
- Aluminium brackets, nails
- 90 degree 10mm solder ring copper elbows (10$)
- Clear transparent glass piece 3 ft x 6 ft (10$)
1st step is the construction of a wooden frame in which copper tubing will be installed. A rectangular wooden frame of a size of 3 ft by 6 ft is sufficient for a family of 5 members. You will require two solar panels of this size for a family of 10 members. The wood pieces must have a width of about 5 cm. Now cut two wooden pieces each 3 ft in length. Cut two wooden pieces each 6 ft in length. Nail all the four pieces to make a wooden frame. Drill two holes in the wooden frame at opposite ends as shown in the figure below:
Cut a piece of plywood and an aluminium foil of a size equal to the outside area of the wooden frame. This can be done by placing the wooden frame on plywood and mark the outside boundary of the wooden frame. Glue together aluminium sheet and plywood.
Above two steps are very simple and do not require much time to build. This step requires more attention. Cut a copper tube in to 10 pieces each of length 2.5 ft. Now cut further 9 pieces of copper tube each of length 0.5 ft. Copper tubes can be cut by copper tube cutter easily available at local shop. You may also purchase copper tube cutter from ebay.com.
It’s time now to join pieces of copper tubing. You will require 90 degree copper elbows. You will require 18 elbows to join the pieces of copper tubing we have already cut. To join the tubes you will require solder and propane torch. Solder and propane torch can also be purchased from local store or you can buy it from ebay.com.
Please be careful, propane torch has a high flame temperature, so if you don’t have experience, hire a plumber to do this for you. You will require heat insulated gloves before you start to solder copper pipes.
How to Solder Copper Pipes
• Solder will adhere only to clean copper, so first clean the elbow and the tip of the pipe.
• Rub the joint surfaces with some sandpaper. The scarring will create a more receptive surface.
• Daub a thin coat of flux on both the exterior surface of the pipe end and the interior surface of the elbow. Using a small brush makes this easier, but I just used a rag, myself.
• Join the elbow to the pipe end.
• Now fire up the propane torch. Give the propane torch valve just a slight turn to get the flame going.
• Once you see the flame, you can adjust the intensity. You won't need a high flame for this soldering operation.
• Keeping the torch as upright as you can, begin to apply the flame to the joint.
• Move the flame around the joint to distribute the heat evenly.
• When the copper at the joint starts to change color, it's starting to get hot enough to receive the solder.
• Unwrap some of the solder from its roll.
• Touch the end of the solder to the top of the joint. The solder should begin to melt. If not, heat the joint further.
• If the solder starts to melt, take the flame away and run the solder around the perimeter of the joint, back to the top where you began.
• Some wipe the joint with a wet rag at this point, but, if you do so, make sure you don't jostle the joint.
• Join all the pieces of copper tubing in the same way.
After joining all the pieces, you will get a network of tubes as shown in figure below:
Allow it to cool down. Then check the copper tube network for any leakage by passing water through it. Then plug one of the sides and continue to pass water from the other side. Any droplet of water on copper tube would indicate leakage. Repeat the solder procedure to fix the leakage.
Attach copper tube network on aluminium sheet using copper tube brackets. You can use 5 copper brackets each equally spaced to fix the tube network on the frame.
Now you need to spray paint the interior of the wooden frame. Black spray paint is used for this purpose. This is an important step, which should not be skipped; efficiency of the solar heater is because of black spray paint. Do not use enamel or any other paint as it will scrap out due to heat and solar heater will become ineffective.
Join inlet and outlet of the copper tube network with two sections of a hose pipe. Flexible pipe should be resistant to UV damage. These two sections should be long enough so that they can come out from the holes drilled in the wooden frame. Buy a slide of glass of any thickness and of the same length and width as that of the wooden frame. Cover the wooden frame with this glass. You can join the glass and frame with hooks available at local store. Care must be taken in
joining the glass with the wooden frame. It should not leave any space in between glass and wooden frame; otherwise dust will deposit inside the solar panel and it will reduce its efficiency.
Your solar panel is ready for action. Now you need a hot water cylinder copper boiler tank, copper tubes for piping (1 inch diameter piping is recommended), a small water pump and a few valves for operating and isolation of the system.
Tank is required to provide hold-up of hot water. A cylindrical tank with a diameter of 2 ft and height of 4 ft (Capacity of 90 gallons) is suitable for a whole day requirement of a family of 5 members. Buy a new or used hot water cylinder copper boiler tank, a new one will cost you about 200$. This tank comes with insulation and fitted copper tubing for
circulation of heated water. You can place this tank at the basement. A figure of hot water cylinder copper boiler tank is shown below:
- Drain off valve for quick drain down of cylinder, pipe work and header tank.
- Water feed from header tank into cylinder.
- Exit/Return of copper coil - connect to boiler/heating circuit/2 or 3 port valve.
- Inlet/Flow of copper coil - from the pipe work of boiler/heating circuit/2 or 3 port valve.
- Copper coil - water heated by solar panel flows threw the coil to heat stored water (acting as an element).
- Electric Element to heat the cylinder as a backup if solar panel is insufficient or during a rainy/cloudy day.
- Tee - Branching off the outlet of the cylinder from open vent 8. Pipe leading up and usually found looping over the header tank acting as an open vent (Never cap or isolate this pipe) needed for expansion.
You will require an expansion tank, it is necessary, it provides the necessary volume of water to start up the system and it allows space for expansion and contraction of water during operation. An expansion tank of 8 litre capacity is sufficient for this purpose. This tank will cost you about 30$. An expansion tank figure is shown below:
You will require a pump to circulate water though the solar panel. A small pump of 2GPM with a head of 5 meter is sufficient for this purpose. You can purchase this pump from your local store or at ebay.com for less than 20$.
All the piping, valves and equipment needs to be assembled according to the figure shown below:
Remember, the solar panel needs to be installed at the roof of the house and the side must face the sun. Location of solar panel is the most important factor for efficient working of solar water heater. Please do not skip any of the valves; all of these valves are very important for safe working of the system. That’s all, enjoy your newly build solar water heater.
Solar Hot Water System Start-up
Fill the expansion tank with cold water up to almost filled level. Add some amount of glycol (anti-freeze) in water, it will prevent water from freezing during winter. It is available in local market as antifreeze mixture. Then startup the pump. The pump will begin to circulate water, you can check water circulation by slightly opening the drain valve at the discharge of pump. Close the drain valve and allow the water to circulate, it will take some time for water in the loop to get heated up. The heater water will transfer heat to cold water inside the hot water cylinder. Within two hours, you will have hot water in hot water tank.
Caution: In very hot climate, solar water heater can make very hot water which can cause damage, so it is advised to turn off solar hot water system in very hot, sunny climate.