Solar Thermal

solarthermSolar water heaters, also called solar domestic hot water systems or solar thermal can be a very cost effective way to generate hot water for your home. They can be used in any climate, and the fuel they use (sunshine) is totally free!

How They Work.

Solar water heating systems include storage tanks and solar collectors. There are two types of solar water heating systems: active, which have circulating pumps and controls, and passive, which don’t.

Active Solar Water Heating Systems.

There are two types of active solar water heating systems:

Direct circulation systems
Pumps circulate household water through the collectors and into the home. They work well in climates where it rarely freezes.

Indirect circulation systems
Pumps circulate a non-freezing, heat transfer fluid through the collectors and a heat exchanger. This heats the water that then flows into the home, these are popular in climates prone to freezing temperatures.

Passive Solar Water Heating Systems.

Passive solar water heating systems are typically less expensive than active systems, but they’re usually not as efficient. However, passive systems can be more reliable and may last longer. There are two basic types of passive systems:

Integral collector-storage passive systems
These work best in areas where temperatures rarely fall below freezing. They also work well in households with significant daytime and evening hot-water needs.

Thermosiphon systems.
Water flows through the system when warm water rises as cooler water sinks. The collector must be installed below the storage tank so that warm water will rise into the tank. These systems are reliable, but contractors must pay careful attention to the roof design because of the heavy storage tank. They are usually more expensive than integral collector-storage passive systems.

Storage Tanks and Solar Collectors.

Most solar water heaters require a well-insulated storage tank. Solar storage tanks have an additional outlet and inlet connected to and from the collector. In two-tank systems, the solar water heater preheats water before it enters the conventional water heater. In one-tank systems, the back-up heater is combined with the solar storage in one tank.

Three types of solar collectors are used for residential applications:

Flat-plate collector
Glazed flat-plate collectors are insulated, weatherproofed boxes that contain a dark absorber plate under one or more glass or plastic (polymer) covers. Unglazed flat-plate collectors — typically used for solar pool heating have a dark absorber plate, made of metal or polymer, without a cover or enclosure.

Integral collector-storage systems
Also known as ICS or batch systems, they feature one or more black tanks or tubes in an insulated, glazed box. Cold water first passes through the solar collector, which preheats the water. The water then continues to the conventional backup water heater, providing a reliable source of hot water. They should be installed only in mild-freeze climates because the outdoor pipes could freeze in severe, cold weather.

Evacuated-tube solar collectors
They feature parallel rows of transparent glass tubes. Each tube contains a glass outer tube and metal absorber tube attached to a fin. The fin’s coating absorbs solar energy but inhibits radiative heat loss. These collectors are used more frequently for U.S. commercial applications.

Solar water heating systems almost always require a backup system for cloudy days and times of increased demand. Congenial storage water heaters usually provide backup and may already be part of the solar system package. A backup system may also be part of the solar collector, such as rooftop tanks with thermosiphon systems. Since an integral-collector storage system already stores hot water besides collecting solar heat, it may be packaged with a tank less or demand-type water heater for backup.

Selecting a Solar Water Heater.

Before you purchase and install a solar water heating system, you want to do the following:

Estimate the cost and energy efficiency of a solar water heating system
Evaluate your site’s solar resource
Determine the correct system size
Investigate local codes, covenants, and regulations.

Also understand the various components needed for solar water heating systems, including the following:

Heat Exchangers for Solar Water Heating Systems
Heat-Transfer Fluids for Solar Water Heating Systems

Installing and Maintaining the System.

The proper installation of solar water heaters depend on many factors. These factors include solar resource, climate, local building code requirements, and safety issues; therefore, it’s best to have a qualified solar thermal systems contractor install your system.

After installation, properly maintaining your system will keep it running smoothly. Passive systems don’t require much maintenance. For active systems, discuss the maintenance requirements with your system provider, and consult the system’s owner’s manual. Plumbing and other conventional water heating components require the same maintenance as conventional systems. Glazing may need to be cleaned in dry climates where rainwater doesn’t provide a natural rinse.

Regular maintenance on simple systems can be as infrequent as every 3–5 years, preferably by a solar contractor. Systems with electrical components usually require a replacement part or two after ten years. Learn more about solar water heating system maintenance and repair.

When screening potential contractors for installation and/or maintenance, ask the following questions:

Does your company have experience installing and maintaining solar water heating systems?
Choose a company that has experience installing the type of system you want and servicing the applications you select. Call Planet Energy now for a no obligation assessment and quotation 01427 717311

How many years of experience does your company have with solar heating installation and maintenance? The more experience the better. Request a list of past customers who can provide references.

Is your company licensed or certified?
Having a valid plumber’s and/or solar contractor’s MCS and RECC accreditation is required to obtain the Feed In Tariff.