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Solar Hot Water Systems

Solar Hot Water (SHW) systems are the first element of the renewable energy systems that a homeowners should consider. Its technology is pretty simple and already proven reliable in long term installations. It is becoming popular due to the shortest payback time in terms of cost vs. benefit. They surpass the photovoltaics (PVs) since they can usually pay off for themselves in a relatively short period of time (3-5 years).

Note: SHW systems are currently being installed as a standard equipment on most newly built houses in Europe and are becoming ever more popular in the States.

Solar Hot Water system works on a very simple principle of capturing the sun's heat through collectors placed on your roof and storing it in water tanks for your hot water needs, or even heating your home.

The SHW system the consists of few simple components. First are the solar collectors that you usually mount on the roof or in some other un-shaded area. These collectors are connected via a set of pipes to the heat exchanger and the hot water tank somewhere in your home. The pipe system is usually filled with a solution of water and glycol (to prevent freezing) and powered with a pump that circulates the glycol solution through the collectors and the heat exchanger (in a closed-loop antifreeze type). When the sun shines on your collectors, it heats the fluid in the pipes embedded in the collector and hot fluid is then circulated from the collectors down to the heat exchanger. Heat exchanger then transfers that energy into the water tank that is part of your house water system. Water is heated with this free sun energy and can then be used for you house consumption, such as showers, dishwashing, laundry or even hydronic floor heating systems.

Measure of material's heat-conducting properties: Heat conduction rate per unit surface area per unit temperature difference between its two sides.

How do I convert U-Value from SI units to English units?

Divide the SI number by 5.678. For example, If U=1.4 W/m²K in SI units, then 1.4/5.678 = 0.246 Btu/hr-sf-°F in English units.

Conversely to convert from English to SI, multiply by 5.678:  0.246*5.678 = 1.4 W/m²K.

What is R-Value?

R = 1/U-Value

A measure of the capacity of a material, such as insulation, to impede heat flow, with increasing values indicating a greater capacity

There are a few different designs of SHW systems that can be installed, each with its own advantages and disadvantages: single (or multi) tank closed-loop drainback system (above), closed loop antifreeze, solar batch, thermosyphon and open-loop direct. Your system installed or designer can help you select the system best suited for your situation.

Until few years ago, the installation of the SHW was an involved process. It required a careful design of the system, sizing of the collectors, pumps and heat exchangers to accommodate the needs of that particular household. It also required a certified plumber to size, fit and connect all the pipes, fill and pressure test the system. There are many system providers today that greatly simplify this process. SHW systems now come with pre-sized collectors and pre-assembled components including integrated tanks and heat exchangers along with pumps and control systems that come as a package to fit your home needs. Most of these new technologies again come from Europe.

Explore following web sites of some of the system manufacturers such as Heliodyne (www.heliodyne.com), Stiebel Eltron (www.stiebel-eltron-usa.com), Viessmann (www.viessmann-us.com), Apricus Solar (www.apricus-solar.com), Oventrop (www.oventrop-na.com), Conergy (www.conergy.com), Schuco (www.schuco-usa.com) ... to find out more about their products.