All modern solar thermal systems use these bits of equipment. Thermostats control individual parts of the system, although they're not used to control the main flow through a solar loop. Unions are the joins in the piping.
It may seem a novel concept to heat your domestic water supply with a refrigerant, but it's not so odd when you really think about it. After all, the area behind the refrigerator in the kitchen is pretty warm, so surely there's a way to turn this to your advantage?
A variety of valves are used in solar thermal installations, each type serving an individual purpose. It's important to choose the right valve for the right job.
Swimming pool heating is the single most popular use of solar thermal systems: more collectors are sold for this purpose in the USA than for any other installation. In fact, solar pool heating is so popular that, on average, seven pool collectors are sold for every flat plate or evacuated tube model.
Why are they so popular? Because they're cheap, simple and save lots of money – a solar thermal system for a seasonal pool can pay for itself in as little as two or three years!
Before you decide which kind of system you're going to install, it's important to understand the basic terms used to describe them.
An open loop or direct system is the simplest: the domestic water actually enters the solar collectors and is heated by them before heading back to the storage tank.
Indoor swimming pools have exactly the same heat load throughout the year. A solar thermal setup can provide 50% of the load in winter and 100% in summer – the amount varies because there's less solar radiation in winter to generate heat. In general, an indoor pool solar thermal installation is sized to generate the right amount of heat on the best possible day: this ensures that the system never overheats.
A pressurized system should really be referred to as a "closed-loop pressurized antifreeze solar thermal system" – the two-word version is much simpler and more common! Pressurized systems are the most flexible type of solar hot water installation and, consequently, are the most common worldwide.
Much like seasonal swimming pools, spas and hot tubs can profit enormously from solar heating systems. This is especially true if you're installing a solar thermal system for your domestic hot water supply or space heating because the tub or spa can act as a shunt load, using excess output from the household system.
A pressurized solar hot water system almost always follows a standard layout, which is one of the reasons most manufacturers are able to offer simplified kits for residential installations.
In most parts of the world, space heating systems are installed in every home. They provide warmth and comfort during the colder part of the year. Unfortunately, the vast majority of these systems rely on grid-tied, non-renewable power sources to provide that heat. In a bid to reduce our environmental impact – not to mention our operating costs – we can use the sun's power to provide space heating.
