Building a solar-powered water heater is your first step in reducing energy dependence; participate in greenhouse emission reduction and saving money on energy bills.
Keep in mind when you build a homemade solar water heater that solar energy can provide the needed power for your domestic hot water needs, but it greatly depends on geographic location, collector orientation, panel size, and your designing and DIY skills.
Moreover, you should be proud, not only because you are using "free" and renewable energy, but because you are contributing to saving the environment from greenhouse gases and other pollutants.
The passive solar hot water systems are what we are going to introduce you here, as they are simple, easy to make and economical for your budget.
The main passive solar water heaters components are; storage tank, solar collector to absorb solar heat and back up energy source. Of course, there are other elements, valves, pipes...
To design and build this kind of a solar water heating system it can be a very simple and challenging DIY project at the same time.
Also, keep in mind that success of your solar powered water heater depends on its ability to collect, save, store and transfer solar energy, even when there is no direct sunlight when there is only diffuse radiation from a sun (cloudy periods for example).
Before you start building your first or second solar power water heater, it is good to know that there are two types of passive systems:
The first thing you should consider when building solar water heaters is the location of your collectors or panels. You need sun exposure and lots of it. So, install the system in a sunny spot. The best location is on the roof of your house. If it faces south, better. It can also be a free-standing one.
If you are using the solar-powered water heater mainly during the summer, install the solar panel at the angle - closer to horizontal. The highest heat absorption and the most efficient heat transfer is when the sunlight is coming perpendicular to the solar collector.
That means the slope of the panel can be changed based on what part of the year is when it is used and the place of the site.
To gain even more solar heat you can build reflectors, like polished aluminum or mirrored panels, usually parabolic in shape to concentrate the sunlight on the tubes or in the tank.
The solar collector has to be effective, to attract enough sun heat, to retain and transfer it to the fluid. The easiest way to make your solar powered water heater effective is to paint it black. This works great when it is sunny outside, but what to do at night or during the colder days?
Put your solar water heater in a tight, insulated box with the glazing on the top facing the south, so that it can attract even more solar energy. Multiple glazing is also desirable to keep collected heat inside the panel or a box.
Glass is the best for glazing, actually tempered glass, but you can apply other materials like fiberglass and acrylic, but be sure to select one which can handle temperatures of up to 220 F (90 C).
Tips: An insulated box has to be well sealed, so hot air cannot escape. The movable insulation (shutter controlled by the actuator or small motors), or simple blanket, on top of the glazing, can be used to keep the temperature during the night and reduce the heat loss.
Based on your hot water needs and other requirements, plan and design the collector with the right size. To provide enough hot water consider building a collector with no more than 2.5 gallons per sq ft or 100 l per 1 m2 of the panel.
Make the necessary plumbing work and connections. This refers to connections between the collector panel and the plumbing system, so it is as efficient as possible, with the reduced distances wherever possible and putting the insulation. The idea is to reduce heat loss through the heating system.
For the long life of your solar powered water heater you should also consider; freeze protection, corrosion protection, proper drainage, maintenance, and servicing. For example, for protection, use copper whenever it is possible and as much as you can as it is corrosion resistant.
To prevent tank corrosion, prepare the exterior surface for painting and use the appropriate primer and finish coats. For inside protection, you can use the sacrificial anode. Spend even more money on quality elements as you want to build a solar-powered water heater that will last.