With the focus these days is on renewable clean energy, a solar hot water heater system might be worth considering, especially since the sun certainly qualifies as renewable and clean! The trick is to know how they work, how well they work, the types available, how much they cost, along with your home variables such as climate, roof space and available sunny areas.
Here's a quick Q & A to answer some often asked questions about a solar water heater system so you can be the educated consumer when you start looking to either replace your hot water system and/or go green.
How does a solar hot water heater system work?
It' s pretty simple: sun heats your water the way it would if you put a glass of iced lemonade in the sun for a while, but on a bigger scale with a little more technical help.
The parts of the solar water heater system are a tank (sometimes more than one) and a “collector”, which is connected to the tank . Basically the collector is a unit that heats the water from the sun's radiant heat with help from heat conducting materials built in. Collectors are usually placed on a raised area, like your roof. The tanks, of course, hold the water and are placed in a sunny place. That's your basic system.
Collector types differ from flat plates to insulated glazed boxes to solar tubes, and the best type of collection system for you depends on the size of your house, your climate and your hot water use pattern.
I've heard of active and passive systems, what's the difference?
An active solar hot water heater system has circulating pumps and controls to move the water through your home either directly or indirectly.
- Direct circulation systems uses pumps (usually electric-powered) to circulate the heated water from the collectors throughout your home and work best in climates that don’t freeze.
- Indirect circulation systems work best in climates that have freezing temperatures. The pumps move a nonfreezing heat transfer liquid through the collectors and heat exchanger to heat the water as it moves through your home.
A passive solar water heater system doesn't use any other form of energy or pumps and depends on the ‘greenhouse effect' – that hot water rises above cold. As you can imagine, this type of system is not as efficient as an active system, but it can last longer, be more reliable and is “greener' than active systems because no other energy source is needed.
The two basic and best home systems right now are:
- Thermosphon system is less costly than the Integral system (below) but because the collector must be installed below the storage tank so the warm water can rise into the tank, placement on the roof can be an issue.
- Integral collector hot water system is better in areas without freezing temperatures during the year, which limits their use in the northern half of the U.S.
Am I Going to Need a Back up Hot Water System?
Yes. According to a report by the U.S. Department of Energy, a solar hot water heating system “almost always” requires a gas or electric back up hot water system for cloudy days or times of high demand. Your climate is going to make a big difference – solar hot water heating system does a reasonably good job in the summer of the Northern U.S if you have a good sunny place for the collector and tank, but not nearly as well in the winter. If you live in the Northwest U.S., for instance, or along certain areas of the Great Lakes that have a high proportion of cloudy days compared to sunny days, a solar hot water heater system may not make sense for you.
Is a Solar Hot Water Heater System Cost Effective?
A solar hot water heater system can save you hot water heating energy costs, but not as much as you might think, especially in colder, grayer climates. A map from the Energy.gov gives a good picture of geographic differences that can affect cost efficiency of a solar hot water heater system. Savings range anywhere from 50 to 80% of your water heating energy bill.
Consider this against the cost of the system and installation, which can be high. But both the Federal government and states have some energy incentives for Energy Star rated solar hot water heating systems.
It's best to calculate the savings for your home, usage, geographic location and other variables at Energy.gov
What's the Bottom Line on a Solar Hot Water Heater System?
It can get a little complicated when factoring in location, type of system, household hot water usage, cost of acquiring and installing a system, and projected savings. If going green by using the sun's energy is part of an over all plan for your home, then using photovoltaic panels that work by converting solar power to electricity for your whole home, including your hot water heater, may be a better bet.
Your best bet is to do the research at reliable online sites and speak with a solar power expert before you make a decision to include a solar hot water heater system in your green house plan.