Installing a solar water panel system at home is a good way to cut down on your electricity bill. But before you go out and buy the first system you see, here are a few things to consider to help you find the best solution for your situation.

Panel Size And Numbers

Most solar water panels are roughly one meter wide by two meters long. Typically, you will need about one to three of these panels to heat the water, but obviously it depends on what size tank you plan to install. If you use a reputable installer, they will know how many panels you will need.

If you already have a solar hot water system, but it is not producing enough hot water, it is a good idea to get additional panels instead of replacing the entire system. To ensure the new panels fit with the current setup, try to use the same installer who sold you the initial system.

Panel Technology

Solar water panels come in two main types: evacuated tube and flat plate technology.

Evacuated tubes or “concentrated collectors” have two benefits: they can make more heat when the sun is weak and they are less vulnerable to frost damage in winter. The disadvantages of using evacuated tube panels is that the tubes are more expensive and they tend to be more brittle (but they can be easily replaced).

Flat plate technology has been around the longest, making it the cheapest and most widely used. Although it is less efficient at heating water in cloudy or windy conditions, it’s sturdy design and quick return on investment lends it to being a good option in hot, sunny climates.

Tank Location

There are two ways your solar water panel system can be setup: either with the tank on the roof, or with it separate from the panels.

Roof mounted tank: “Passive Solar Water Heater”

With this system the tank is mounted directly above the solar water panels. The advantage of this system is that it uses natural physics for  the water to flow, making it very affordable -- as hot water rises up the tank, it is replaced by cool water from the mains, which then flows through the collectors, and into the tank as it is heated.

Other than the aesthetic problems with a roof-mounted tank, it may not be a viable option if the tank is too far from where the hot water is needed. The further the water has to travel, the cooler it gets, which results in a lot of wasted hot water.

Indoor tank: “Split Solar or Active Water Heater”

With this system only the solar collectors are on the roof, with the tank located where you current tank is. To get the heated water into the tank, a small electrical pump is needed. Although energy is used to power the system, the indoor tank is better insulated, keeping the water warmer for longer.

The advantage of this system is that you can place the tank close to where the water is needed, making it more efficient at delivering hot water quickly. Furthermore, the pump has a built-in frost protection monitor, where if the collectors get too cold, warm water from the tank is pumped back into them, preventing them from freezing over.

The the only disadvantage of the split system is that it tends to be more expensive.

This video shows how an active system works:

Panel Coating

A solar water panel can be coated in various ways, which determine its efficiency and longevity:

The lowest grade coating is black paint. Although it is cheap, it requires a lot of solar energy to heat the water. It may be okay to use it in hot, sunny regions, but it will produce little heat in temperate, cooler climates.

Anodized or “selective” coatings are the most popular option for domestic water heating systems. The collectors are anodized with either aluminum oxide or copper. When seen under a microscope, these coatings create  hills and valleys, resulting in a larger surface area for the sunlight to penetrate.  Although the coatings can be damaged easily, they are protected by glass, helping them last for years.

An advanced technology used throughout households in the United States is black chrome. This coating is also very efficient at absorbing sunlight, making it a good option if you do not have a sun-facing roof.

The only problem with black chrome is its health risks in the manufacturing process. This has made it less popular for European manufacturers that use better technologies -- such as anodized coatings.

Frost Tolerance

In cold climates frost can be an issue. Heavy frost in winter can freeze and expands the water in the panels, causing them to crack. You can prevent this in two ways: frost valves and closed-loop systems.

Frost valves perform better when you only have the occasional frost. How they work is as the temperature drops, the valves open up, releasing water out of the panels, and averting damage. Before getting any frost valve, make sure it has a warranty against frost damage.

A Closed-loop system is ideal if you live a region that experiences a lot of frost. With the system, glycol is heated in the panels and then transferred to a heat exchanger to heat the water. Although the system is more expensive, glycol never freezes, even in the coldest temperatures.

Conclusion

When buying and installing a solar water panel heating system, ask yourself the following questions, to help you decide which setup to get:

1. How many people are in the household? -- since the average person uses fifty liters of hot water a day, this will determine the number of panels and size of tank needed.
2. How far away are the showers and other hot water outlets from the roof? -- a split solar water heater is better in a double-story house.
3. What direction and how much sunlight does the roof get? -- this will determine what type of coating on the panels to get.
4. Is there a lot of heavy frost in winter? -- if not, then a frost valve is sufficient.
5. What is my budget? -- this is the deciding factor on the quality of system you can afford to get.

As you can see, there are lot of things to consider when getting a solar water panel system for home. Hopefully, with this knowledge, you will be able to buy the right system for your needs, without getting ripped off in the process.

Originally posted 2008-11-27 16:03:39.

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