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Solar Hot Water Panels

Solar Hot Water 

The production of solar hot water is one of the most cost-effective solar power house applications; typically reducing conventional water heating cost by about two-thirds.  However, a solar heating system can save as much as 85% on hot water cost in some climates, which can be as much as 25% of total home energy costs.  All solar applications provide the dual benefit of reducing fossil power expenses and reducing the associated fossil fuel environmental impacts of conventional energy generation.  These are essential solar energy facts to understand for decision making.

The two main components of virtually all solar water-heating systems are solar panels which serve as the heat collectors, and a storage tank.   A fluid of some type (which is often water) is used to move the heat from the collector to its point of heat transfer, storage or usage.  The type of fluid and way it is handled will depend on how the hot water is used and the system employed to transport the fluid and transfer the heat.

There are two types of solar hot water systems; active and passive, but active systems are the most common.  The three main home uses of active solar hot water systems are to heat water for consumption, space heating, and heating swimming pools.  There are three types of solar panels (collectors) used in solar hot water systems, but the most common is the flat plate collector.

Active solar hot water systems

Active solar hot water systems use electric pumps, and controllers to circulate water (or other fluids) through the collectors. There are two categories of active solar hot water systems:

  1. Direct-circulation systems which employ pumps to circulate pressurized potable water through the panels (the heat collectors). These systems are suitable only for areas that do not have extended periods of hard freezing.

  2. Indirect-circulation systems pump a non-potable heat-transfer fluid through collectors. Heat exchangers transfer the heat from the fluid to the potable water. The two most common indirect systems are:

    • The antifreeze system which employs a heat transfer fluid that is usually a mixture water and a non-toxic food-grade propylene glycol.

    • The drainback system, which is a good choice in colder climates, pumps water through the collectors. The water in the collector drains back into a weather-protected reservoir tank when the pumps stop.

    Illustration of an active, closed loop solar water heater. A large, flat panel called a flat plate collector is connected to a tank called a solar storage/backup water heater by two pipes. One of these pipes is runs through a cylindrical pump into the bottom of the tank, where it becomes a coil called a double-wall heat exchanger. This coil runs up through the tank and out again to the flat plate collector. Antifreeze fluid runs only through this collector loop. Two pipes run out the top of the water heater tank; one is a cold water supply into the tank, and the other sends hot water to the house.

Passive solar hot water systems

Passive solar hot water systems use thermosyphon and gravity to naturally circulate water as it is heated.  Due to the absence of electrical components, passive systems require less maintenance, and have a longer useful life span. The two main types of passive systems are:

  1. Integral collector storage systems: also known as ICS or “batch” systems, are good for areas that rarely experience freezing, in homes that have significant daytime and evening hot-water needs; but not predominantly morning needs.  They have one or more black storage tanks inside a glazed insulated box.  Cold water is first preheated in the solar collector tanks and then continues to a conventional water heater.

  2. Thermosyphon systems: use the natural convection of warm water rising to circulate water from the tank through the collectors as water in the collector heats and rises naturally into the tank above.  To conceal it from view, the storage tank is often placed in the house’s attic of the solar power house. These systems are moderately priced, cost effective and reliable. Below is a skematic of a thermosyphon system:

Illustration of a passive, batch solar water heater. Cold water enters a pipe and can either enter a solar storage/backup water heater tank or the batch collector, depending on which bypass valve is opened. If the valve to the batch collector is open, a vertical pipe (which also has a spigot drain valve for cold climates) carries the water up into the batch collector. The batch collector is a large box holding a tank and covered with a glaze that faces the sun. Water is heated in this tank, and another pipe takes the heated water from the batch collector into the solar storage/backup water heater, where it is then carried to the house.

Flat-plate solar hot water panels (collectors)

The solar power home hot water applications of consumption, space heating and pool heating only require temperatures at or below 180°F which is in the heating range of flat-plate panels.  Although evacuated-tube collectors can reach temperatures higher than 200°F, their cost is approximately double that of flat-plate panels. Therefore, flat-plat are almost exclusively used in these applications.

As depicted below,a flat-plate collector is typically an insulated box with a glass or transparent plastic cover and a black absorber plate.

Graphic of the components that make up a Flat-plate collector. The lower layer contains insulation, followed by an absorber plate and the flow tubes. The top layer is the glazing. The components are encased in a glazing frame. There is an inlet and a outlet connection at either end.


Solar pool heating collectors are typically unglazed as in figure below.

Graphic of the components that make up an unglazed Solar Collector.

A steadily increasing environmental awareness coupled with a steadily growing do-it-yourself interest, has motivated more and more people to build their own solar water heating and other solar systems from scratch or to buy easy to install kits.  DIY solar water heating systems are usually much cheaper than commercial ones, and installation costs can usually be avoided as well. With the help of a good DIY solar energy program it is now very affordable and a very easy task to have you own solar power home.
 
The DIY GreenDIYengery alternative energy package displayed on the right is better than most and among the best.  It is well explained, easy to use, and reasonably priced.  So if you have interest in a DIY solar project check it out and see if it works for you.

Solar Hot Water

Technorati Tags: passive solar water heater, pool solar panel, residential solar panels, solar energy facts, solar hot water heater, solar hot water heating, Solar Hot Water Panels, solar pannel, solar pool heaters, Solar Power House

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    [...] based solar home heating systems use the same solar hot water panels and other components as are used to produce solar hot water for domestic consumption.  [...]

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    [...] the roof or in the swimming pool. When it comes to solar panels, there are two types and these are; solar thermal collectors and photovoltaic modules. The latter generates electricity while the former generate [...]

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