Solar Thermal Panels: Free Hot Water

One of the easiest ways to make the switch to renewable energy in your home or business is with a solar hot water system. Solar thermal panels allow you free, nearly unlimited hot water for bathing, laundry, dishes and endless commercial uses. Homeowners often install solar panels to heat swimming pools and spas.

On the commercial side, some car washes now use solar hot water. Breweries and garden nurseries are also among businesses that can benefit from cheap hot water from solar thermal panels. Green hotels and spas also cut their massive energy usage by using solar energy to heat water required for a myriad of uses - pools, washing sheets and towels, and guest bathing requirements.

Compared to solar electric (photovoltaic or PV) panels, solar thermal panels are typically more affordable, and your return on investment is shorter. Not only that, but solar hot water systems are eligible for a number of government rebates, tax credits and other incentives. Solar power is going mainstream these days as people look to save money, as well as the planet!

Ready to consider tapping into free hot water with solar thermal panels? Read on!

If you are looking to save energy and money, one of the biggest power hogs in the home is an electric or natural gas hot water system. With solar thermal panels and a specialized solar hot water tank, you can instantly see a reduction in utility bills for little money upfront.

In fact, solar hot water systems are both cheaper and more efficient than PV solar panels. When you consider federal and state tax incentives, credits and rebates, homeowners can recoup their investment in as little as two years, although the average ROI is about 4-8 years. Because solar thermal collectors use radiant solar energy, they are more than three times more efficient than photovoltaic panels. That means for every hour of sunlight, you are able to convert three times as much energy for use within your home or business.

The California Energy Commission estimates that, by installing a solar hot water system, the typical household can cut 60-70% off their annual water heating expenses!

There are several components of a solar hot water system, none of which are too complex. If you hire a professional to help with installation, you can have free hot water within a day.

Generally speaking, you need the following:

• Solar thermal panels (also known as solar collectors)
• Mounting system for the solar thermal panels - they are usually installed on rooftops
• Solar storage tank - in other words, your new solar hot water tank
  
• Water pump and controls (not required for passive or thermosyphon systems)
  
• Heat exchanger and expansion tank (only for closed-loop solar hot water systems)
• Isolation valve
• Backup Water Heater
• Tempering valve - to make sure your solar heated water doesn't get too hot!
  

Depending on the type of solar thermal panels (solar collectors) and solar hot water system you install, the mechanics of heating water with solar energy are fairly simple. Two general types of solar hot water systems exist: passive and active.

As the name implies, a passive solar thermal panel hot water system does not require pumps, but rather uses thermal dynamics to move hot water through cold water (heat rises, remember?) With an active system, you need electrical pumps and controls to move cold water through the solar thermal panels into the storage tank.  Additional equipment means more expense and maintenance.

Let's start with active/pump-driven systems, of which there are two from which to choose for residential purposes: direct or indirect circulation. In warm climates, direct circulation systems simply pump the cold water through the solar thermal panels where radiant heat from the sun warms it. From there, the water is pumped into the holding tank for use. Since the water is heated directly by radiant energy, it is called an "open-loop " system.

If you live in a colder area of the world where freezing temperatures are often experienced, use an indirect active pump system. Instead of water pumped through the solar collector, a heat transfer liquid (which resists freezing) circulates through the panels as well as a heat exchanger, gets warmed and then transferred to the storage tank where the water is heated by the warmed-up heat transfer liquid. These are often called "closed-loop " systems.

With passive solar hot water systems, no pumps or other mechanical devices are required, which often make them cheaper and more affordable for homeowners. Again, there are two general types of passive systems: batch systems (also called Integral Collector Storage, or ICS) and thermosyphon (also spelled thermosiphon) systems.

The latter are the more commonly used by households. They rely on thermodynamics and require both the solar collector and storage tank to be placed on the rooftop (hot water rises from the panels to the storage tank).

No matter which type of solar hot water system you use, most people keep a back-up hot water tank for days where there is low UV light and/or when solar energy cannot heat enough water for your requirements.

There are several types of solar thermal panels that can be used with solar hot water systems. Like the systems themselves, the panels you select will depend on your climate and hot water needs.

Flat-plate solar collectors look much like their PV solar panel cousins. Unglazed, flat glass or plastic plate coverings fit over an insulated box in which a dark absorber plate is placed. These solar thermal panels are often used for swimming pools and spas.

ICS or Batch Collector-Storage panels are characterized by black tanks or tubes, also in an insulated box. As cold water passes through the tanks or tubes, it is warmed by radiant energy, and from there flows toward the storage tank for use.

Evacuated tube solar collectors are commonly used for commercial solar hot water applications. They consist of parallel rows of glass tubes and also include metal absorber tubes attached to a fin.

There are many reasons you may want to use renewable energy to heat the water for household domestic uses:

• Protection against rising electricity and/or natural gas costs
• Pay for the cost of the system only, and not for the energy to heat water
• Quick return on investment (ROI) in a matter of years
• Adds value to your home
  
• Live with a smaller carbon footprint
• Federal, state and/or local rebate and incentive programs help defray the costs and lower your tax burden
• Low maintenance over the life of the system (about 20-30 years)
  

There are a number of DIY solar hot water systems available.  It can be a relatively simple weekend project, depending on the type of solar collectors you select, and whether you are going with an active or passive system.

For closed-loop systems and those requiring pumps and heat exchangers, it is recommended that you hire a professional solar thermal system contractor.  Paying just a bit more for the service can save you headaches later.  Contractors can even help you maximize your tax savings or apply for rebates!

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