Solar Water Heating: Overview

An Introduction to Solar Water Heating – the Other Solar Technology!

By now, we hope you’ve already heard this under-reported fact: solar water heating is a renewable energy technology with a BIG bang for your buck! Why do people overlook this affordable and proven option? Solar water-heating technology may have gotten off to a bad start in the public eye when inexperienced installers in the past poorly installed systems that later failed or never performed up to expectations. Another reason: there is still a lack of public awareness and understanding of the technology.

How They Work

An example of solar water heating at its most basic level is a garden hose left out in the sun. When you turn on the spigot, the first water to come out of the hose is warm since it’s been baking in the sunlight. A solar water collector works in a similar fashion. Water flows through tubes housed in a solar collector. Throughout the day, a sensor monitors the difference in water temperature between the water in the storage tank (inside the home) and the water in the collector (typically mounted on the roof). At a preset temperature difference, the sensor triggers a pump to circulate the water through the collectors where it absorbs solar heat. In summer months, a solar hot water system can meet all your household hot water needs! Over the course of the year, the system can cover up to 85% of your hot water needs. The typical investment is about $3,000 to $6,000, not including installation. Be sure to investigate tax credits and rebates in your area which can help reduce that initial investment.

Types of Systems

A primary factor in identifying the type of system you need is your location. If you are in an area where it could ever freeze –EVER- then you’ll need a “closed-loop” system. Closed-loop systems are also referred to as “indirect” systems. In a closed-loop system, the fluid that is being heated in the solar collector isn’t the actual water you’ll use; it’s a mixture of water and food-grade propylene glycol that doesn’t come into contact with your domestic water. This glycol-water mixture won’t freeze in the collector—a situation that could burst the piping. This sun-heated fluid then gives its heat to your domestic water supply through a heat exchanger.

If you live in a climate that never freezes --EVER-- you can use an “open-loop”, or “direct” system. An open-loop system is slightly less complex than a closed-loop system, and the potable domestic water is itself sent through the solar collectors to be heated directly. There are also “thermosiphon” systems available. These systems rely on the principle that hot water rises. In thermosiphon systems, the collector and an integrated water tank are located on your roof. As the water heats up in the collector, it will rise to the tank above it. The thermosiphon system is a “passive” system, meaning it does not require a pump.