Solar Hot Water Saves Energy

Thermal collector for solar hot water

If you are like me, you may have wondered about the variety of different solar systems that you can install on a home or business.  For years, I didn’t know the difference between solar panels, solar roof tiles and thermal collectors for solar hot water. I found that, once you know a little about these various solar power systems, you can decide what is best for your life and your budget.

Personally, I am probably most intrigued with the concept of solar hot water.  Three basic components comprise solar hot water systems:  collection, storage and distribution.  There are a number of different solar hot water heating systems to consider, which depend in part on your climate, the amount of hot water you use (cooking, bathing and washing clothes and dishes), and overall location.  As with solar panels, you will want to make sure that the thermal collectors for your solar hot water system are not blocked by vegetation, and are properly tilted towards the sun.

Did you know that people with solar hot water systems can save up to 80% of their domestic hot water energy?  That is an incredible statistic!  Of course, businesses that need a lot of hot water, like car washes, laundromats and breweries can benefit greatly from the energy savings from a solar hot water installation.

Once you decide on a proper location on your roof for thermal collectors, you will need to determine which solar hot water system is best for you.

Another example of thermal collectors on a home

A closed loop glycol system is the one with which I am most familiar.  This is because, although my home is located in a sunny Central Oregon city, it gets very cold in the winter months.  The closed loop glycol solar hot water system is best for homes in locations where temperatures can drop.  The glycol solution helps prevent freezing water from clogging up the system.

With a closed loop glycol system, a thermal collector is warmed by radiant energy from the sun.  Once the collector is warmer than the water being heated, a pump starts circulating the water to heat it evenly.  This continues until the storage tank reaches its maximum set temperature, or until the thermal collector is no longer warmer than the water in the tank.  Because there is pressure involved with the closed loop glycol system, the unit will have to include an expansion tank, pressure gauge and pressure relief valve, for safety measures.  Once installed, this solar hot water system runs reliably for years, with the only exception of periodic changing of the glycol solution.

Solar hot water tanks are much like ordinary tanks

The most basic solar hot water system is the drainback system.  In this system, the water is not pressurized.  It works in a manner similar to the closed loop glycol system.  The thermal collectors are warmed by the sun; once the collector is warmer than the water in the tank, a pump circulates the water until maximum heating is achieved.  These are so simple and affordable that drainback systems are usually the first type considered when a homeowner desires to install a solar hot water system.  Plus, they can be a do-it-yourself project for more ambitious people (not me – I am going to hire someone!)

The last type of solar hot water heater is a thermosiphon.  This involves a water tank filled with potable (drinkable) water on a roof with southern exposure.  Pressurized water from your well, or from the local water utility company fills up the tank.  Solar hot water heating takes place entirely within the thermosiphon tank, which is fitted with thermal collectors.  Not surprisingly, this type of solar hot water system is not recommended for climates that experience any freezing temperatures.  They are extremely affordable to install and simple to maintain.

So, now you know that you want a solar hot water system, and you’ve decided on the type of system.  Your final decision is what type of thermal collector will you purchase?  Flat plate or vacuum tube?

Generally speaking, flat plate thermal collectors are the least expensive, are durable and lightweight.  They can be used for any of the solar hot water systems.  Flat plate collectors resemble windows in that they have a frame and tempered glass top.  Underneath the glass is insulation and an absorber plate, covered in black paint to draw in even more UV light.  Solar hot water systems work well with flat plate collectors, which can raise the water temperature to 180 degrees F.

Example of vacuum tube thermal collectors

On the other hand, use of vacuum tube thermal collectors may be more efficient for your solar hot water system than flat plate thermal collectors because heat loss back to the air outside is minimized.  This is because they implement a tube-shaped collector fitted with two walls of glass.  The air inside the glass is removed to leave a vacuum.  Vacuums insulate better than the glass part of the flat plate collectors.  The vacuum tube contains a copper absorber that heats the fluid in the solar hot water system.  Another advantage is that vacuum tube thermal collectors produce solar hot water in cool, cloudy regions.  Flat plate thermal collectors cannot.

Are you ready to sign up?  Still need convincing to install a solar hot water system?  How about using the generous federal and state tax credits available for going green!  With energy savings up to 80%, you’ll soon recoup your valuable investment.

Tags: solar hot water, solar water system, thermal collectors