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Comparing the Cost of Renewable and Non-Renewable Water Heating

If you look at the cost of installing an electric heater and compare it to a solar thermal system, you may wonder why you would bother with the latter. A solar water heater can cost more than five times the price of an electric setup, though rebates and government schemes can reduce that by almost half. However, the initial installation costs don't take your annual savings into account... and that's where solar heaters come into their own.

Solar Thermal Investment

Different people like to look at the same investment in different ways. Some people like to consider the return on investment over the entire life of the system (or a part of it), which we look at in this article. Other people prefer to think about how it affects their monthly cash flow. We'll look at the cash flow approach here.

Evacuated Tube Collectors

The most obvious problem with flat plate collectors is the relatively large sheet of glass taking up one whole side of the construction – glass that can't be insulated without stopping the sunlight from heating the absorber plate. To solve this problem, evacuated tube collectors were invented.

Evacuated Tube Collector Parts

Much like flat plate collectors, evacuated tube collectors have a solid, durable, insulated frame with one glazed side which contains absorbers. In this case, the absorbers are individual transparent tubes rather than a single, flat plate under a pane of glass.

The Best Solar Collector

No matter which manufacturer you ask, they'll all tell you they have the best solar collector. They may even tell you that theirs is the most efficient. There's a good chance that they're right, too – and wrong at the same time.

How Efficient is a Solar Collector?

As you should already know, choosing the most efficient collector for your solar thermal installation is more about your situation, location and climate than it is about just picking the top-rated one off a list.

Sizing Pumps in Solar Thermal Systems

One of the most complicated components to size in any solar thermal installation is the pump (or pumps if your chosen schematic requires more than one). All solar thermal pumps are centrifugal models, using vanes or paddles which spin within an enclosed space to create pressure. Your choice of pump will depend on the type of system and two measurements: flow and head.

How to Size a Solar Thermal Space Heating System

A solar thermal space heating installation with storage is one of the most complicated systems to size. There are so many variables: storage size, collector array size, expansion tank size, piping size, heat exchanger size and heat load requirements. There are two ways of working out how big everything needs to be: the complex mathematical way or by rules of thumb.

How to Size a Solar Thermal Space Heating Collector Array

Space heating with solar thermal installations revolves around Btus. If you've sized the heat generation part of your system already, you'll be familiar with this. The next step is to work out how big the collector array needs to be.

Flat Plate Collector Structure

The oldest, simplest and most common solar thermal collectors are flat plate collectors. They have a robust design that can withstand temperatures falling well below zero and rising well above most climate norms (they work fine at around 180°F or 82°C). It's no surprise that they're the base to which all other, more complex collectors are compared.

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