4 Steps to Basic Solar Thermal Design
I’m sure you’ve noticed that as fuel and electricity prices continue to rise, the interest in solar hot water (SHW) systems is also continuing to increase, and your customers may be asking about it. Why? It’s a simple, basic, and proven technology that has been around forever.
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If you’re interested in selling and installing solar how water systems, you’ll need to understand the basics of design so that you can perform proper site visits and understand what drives the costs of the systems.
There are four basic steps in designing a pressurized, anti-freeze based solar hot water system. The details of each step can get more involved than what I’ve written here, but these are the basics.
1) Make sure the roof has solar access and enough room for collectors. Solar access is simply exposure to the sun from 9 am to 3 pm all year round and within 25 degrees, east or west, of true south. It’s best not to have any shading at all, but solar thermal collectors are much less susceptible to shading than photovoltaic systems. If you do have some shading, you can often compensate by installing larger collectors.
How much room do solar collectors take up? Flat plate collectors are typically larger, with an average size of four feet by eight feet.
2) Next, you need to measure hot water usage. Typically, one person uses 20 gallons of hot water per day. This is a good rule of thumb. This number could be less — if there are five people living in a home, they will probably only use 80 to 90 gallons instead of the expected 100. However, some people could use far more water daily, and some could use far less. It is key to collect this information during the site visit.