Let's walk through some example calculations for choosing the correct solar thermal system pump. We'll assume it's for a pressurized antifreeze system, so there's no static head to worry about, and we've installed three collectors, about 100 feet of Type L copper piping, one heat exchanger and a variety of fittings and valves.
1. Collector array flow and head
Combining a solar thermal heating system with an existing hydronic installation requires not only plumbing and solar equipment but some extra control gear – both electronic and hydronic – to divert fluid when needed. There are several options available in most cases.
In some situations, you will be able to wire the solar thermal setup into the existing thermostat control system so that the water supply passes through the solar storage tank's exchanger when there's enough heat to do some good.
When you're designing your solar thermal installation, you'll need to choose an appropriate pipe size – one which fits the needs of the system and the available installation space and complexity.
Although it is usually preferable to connect your solar thermal space heating installation into a grid-tied system and have the two work together, it's not always possible. Some retrofits simply do not lend themselves to integration, so you will end up with two separate systems. They can still work together, just not to the same extent.
In air-based systems, it's very important to plan for a collector array of the right size for your needs. It's a difficult calculation for inexperienced installers because you need to strike a balance between the collector output, the amount of thermal mass inside the building and the rate of heat loss from the structure. If you're unfamiliar with calculating thermal mass and heat loss, it's going to be even tougher.
One of the oldest known man-made solar thermal space heating systems was built by the Romans, who constructed radiant floors for their bathhouses over 2,000 years ago. The systems heated the bathing water and the buildings by circulating hot air under the floors, then up through multiple chimneys. Today, radiant floors are not only the most comfortable heating system available, but the most economical – especially when tied into solar thermal heat generation!
It's a no-brainer, but you'd be surprised how many people do not sit down and plan every aspect of their solar thermal installation before they go out and buy materials. Installing a solar thermal system is a huge project with far-reaching ramifications for your home: the equipment will be in place for decades, so you need to get it right or spend years messing around with expensive repairs and adjustments.
High-mass installations use a sand bed or pit underneath the building and a network of Pex tubes to gather, store and deliver heat to a radiant floor. They are extremely economical to run and provide very comfortable heating for the whole home. Remember to complete your installation in spring, so that the system starts gathering heat as soon as possible!
Let's start with a disclaimer: every solar thermal installation project is different, so these are just basic steps to help you on your way. You'll need to consider your specific circumstances at every stage and plan accordingly. Now that we've got that straight, let's look at the first steps in planning a successful solar thermal system!
1. Work out your needs
Active solar thermal installations come in two main types for space heating: liquid-based and air-based. The third type – high-mass systems – is completely different to active systems and deserves separate treatment.
