During these times when we need to conserve all resources because of their limited supply, we have to start thinking about finding other sources of energy that are renewable which we ourselves can make use of in our own homes.
Among all the available sources known to us, the most energy saving system relative to the cost of installation is the hot water solar heater. What do we think about when we talk of solar energy?
We see solar panels that convert the energy to electricity, and these panels are usually called photovoltaic panels. However these panels are not as efficient as we think they are; this system is only 15-20% efficient and it achieves much less result when it is partly shaded by a tree or nearby building or anything that produces shadows across it.
It is also very expensive: an array of panels that is needed to produce 1 kW of energy per hour can cost you around $6000-8000. The solar hot water system, on the other hand, is 60-70% efficient in increasing water temperature. It also costs less, around $2000 to $2500, to create a similar result as the panels.
Remember when you were a kid playing in your backyard, and you decided to take a drink from the garden hose? The first spurt of water that comes out would be noticeably hot, especially if that hose has been under the sun for the whole day. And if you continue to run the water, all the hot water would eventually get out leaving you with cold water that had been kept cool in the underground piping, not exposed to the heat of the sun.
The hot water heater system uses a significant amount of energy to heat the temperature to the warmth we need to use it for bathing and washing dishes.
Now imagine that same garden hose coiled back and forth and placed inside an insulated glass container on top of your house, where it is fully exposed to the sun. This system captures the sun rays, magnifying it. Insulation allows the retention of the maximum amount of heat.
Such a unit is known as flat plate solar collector. Other systems do not use a box but instead makes use of glass tubes to contain the piping inside a vacuum. These are evacuated tube collectors.
The latter performs better in conditions with lower sunlight. Such collectors need not be placed on the roof for direct exposure; sometimes they are seen on the exterior wall or even on the ground.
Let us discuss the two types of hot water solar heaters,
Closed Loop Hot Water Solar Heater
The fluid in the piping of this solar collector type does not ever leave the system never leaves the system and it is not the water that you use in the house.
Typically a glycol-water mix, this fluid is heated, and transfers the heat generated to the water found in a special hot water tank with a heat exchanger inside it. In this case, the heat exchanger takes the form of a big coil of double-walled piping which is exposed to the water in the tank; this allows the heated fluid mix to transfer its heat to the water.
There is a pump that circulates the fluid, there is a transfer of heat to the water, and then the cooled fluid mix is brought back to the collector to be warmed up all over again. Aside from the heat exchanger, there is also an electric back up heating element or a gas burner that will allow for elevation of the temperature if needed.
To run the required pump, you can use a small photovoltaic panel or the normal electrical power in the house. This type of system is used in colder climates where there is great danger of the water in the tank freezing and damaging the pipes.
This allows the system to be used more often during the year, even during the coldest winter months. The presence of the pump actively moves the water around, preventing freezing.
Open Loop Hot Water Solar Heater
This involves the actual water being heated up directly. There are two subtypes in this system: Integrated Collector Storage Systems (ICS) and Convection Heat Storage Systems (CHS).
The ICS System is known more commonly as a batch heater since it heats water in a single batch, and the tank that holds the water is also the solar collector. The tank being used in the ICS has a glass front container surrounding it, which magnifies the energy of the sun hitting the system.
It is a simple system, which makes it a great advantage. This is suitable in moderate climates with strong sunshine.
The CHS System has both a solar collector and a secondary tank. A small amount of water is heated and the energy generated is then transferred to the storage tank water. If the tank is above the collector, it is called a thermo siphon and there is no pump required to drive the circulation, as it is running on a convection system.
What is required in this system is a very strong roof to support both the collector and the second tank. This second system requires less sunshine than the first ICS and can be used in various climates and areas.
The systems that have been previously mentioned are known to be passive mainly because they don’t require pumps to circulate the water, whereas the closed loop is described as active.
Open loop systems are usually used in areas with warmer climates, but if it is used in an ice-prone area, the system needs to be drained during the winter months to prevent freezing of the pipes, and you can only use this system during the warmer months.
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