Solar thermal systems are different from solar PV systems as they use the sun’s heat to generate hot water or steam, which can then be used for space heating, cooling, or domestic hot water.

Solar thermal systems are most commonly used in commercial and industrial applications but are becoming more popular for large residential properties.

As a renewable energy source, solar thermal can help to lower your energy bills and your carbon footprint.

In this article, we’ll take you through a step-by-step guide on how to install a solar thermal system.

There are two main types of solar thermal systems:

1. Active solar thermal systems rely on pumps or fans to circulate a fluid (usually water or glycol) around the collector to transfer the heat to the storage tank or heat exchanger.

2. Passive solar thermal systems rely on convection and natural circulation to circulate the fluid. They are usually cheaper and easier to maintain than active systems but are less efficient.

Let’s look at the installation process….

Solar Thermal Installation

What is a solar thermal installation?

Solar thermal technology employs solar energy to generate heat, which is then carried via a network of pipes into your home or business.

Solar thermal panels are combined with a boiler, collector, or immersion heater to make up a solar thermal system.

Related: Do Solar Lights Work In Winter? – The Ultimate Guide

The Solar Thermal Collector Installation

Step 1

The first thing you need to do is speak to at least 3 solar thermal installation contractors who are MCS-accredited in order to get the best deal.

Make sure you get a variety of quotes to compare before making your final decision.

Step 2

They will book to carry out a comprehensive survey of your property in order to ascertain whether it is suitable for a solar thermal installation.

This survey will take into account the amount of sunlight that hits your property, as well as the orientation and angle of your roof.

In essence, a solar thermal survey is a plumbing survey with a few extra steps. The contractor will take into account the existing pipework in your property and make sure that it is up to standard and able to cope with the additional heat that solar thermal will generate.

They will also check the structural integrity of your property and make sure that it can support the weight of the solar panels.

If scaffolding is needed, the contractor will organize for this to be erected prior to the installation.

Step 3

If you decide to go ahead with the installation, you will likely have to pay a deposit and a date will be set for the work to begin.

Step 4

The solar thermal installation process itself is relatively straightforward.

The contractor will install a series of brackets onto your roof and then fit the solar thermal panels to these brackets.

Once the solar panels are in place, they will be connected to your existing plumbing via a series of pipes.

These pipes will carry the heat generated by the sun from the solar panels into your home or business.

Solar thermal wall

If needed, your contractor may install a thermal wall. This is a wall that is specifically designed to store heat.

Thermal walls are most commonly found in commercial properties, as they can be used to generate a significant amount of heat.

Solar walls, like Trombe walls or solar chimneys, are one approach to building energy-efficient buildings.

These walls link exterior construction with interior mechanisms in order to utilize solar energy for heating and ventilation.

Heat storage / hot water cylinder installation

Step 5

If you don’t need a new boiler, you’ll just have to install the twin coil water cylinder, pump, and system control panel.

This can be completed in the loft or on the upper level of the property. In some cases, additional plumbing work may be needed at this stage.

A new thermal store / hot water tank will be required to keep the heat produced by the solar thermal collector.

Although this tank is larger than a conventional immersion heater tank, it can be used in place of the old one (if present).

This tank will be connected to:

  • The existing header tank (if present)
  • The solar thermal collector
  • Electric immersion heater (element inside the tank)
  • The cold water mains
  • Your boiler (if you have one)
  • Temperature sensors for managing the whole system.
  • An expansion vessel (unvented models only)

Plumbing In The Solar Thermal System

Step 6

There are three major elements that make up the solar thermal plumbing system:

  • The pumping station
  • The expansion tank
  • Specially insulated pipes

The pumping station

These units are usually made of injection-molded foam that both insulates and mutes the sound. include filling ports, as well as a kit for installation in the front compartment.

Installation of the station will require that the pumping station be constructed (usually near to the water tank); this is where the system pump for the closed-loop solar thermal system is installed, as well as control equipment.

The expansion tank

The expansion tank prevents the thermal expansion of water in home hot water systems. It absorbs the extra volume of water generated by the hot water heater.

The pre-pressurized steel tank has an expansion membrane that keeps air/water contact for long system life.

The expansion tank will be placed near to the water tank and pumping station, ensuring that components are not harmed by pressure changes.

Specially insulated pipes

Since the collector’s temperature must stay below 180°F (82°C), your contractor will need to install specific insulation that can endure high temperatures for at least 180 days and at least 250 days on the pipes from the collector to the heat exchanger.

It doesn’t matter what kind of insulation you use; all that matters is that it can withstand high temperatures.

Between the pumping station and the solar thermal collector, insulated pipes will be installed.

This is the ‘flow and return pipe,’ which contains the heat transfer fluid. The pipe insulation is also installed at this point.

To ensure high system efficiency, the distance between the thermal store tank, pumping station, and collector must be kept to a minimum.

The Electrics and Control System

Step 7

The heat generation meter must be MCS-certified, and it measures the amount of heat generated by your solar system based on how much liquid heat is flowing.

The meter is necessary for calculating Renewable Heat Incentive payments.

The electrics will have to be installed by a trained electrician and will supply electricity to both the control equipment and the immersion heater element.

Installation of control equipment may differ significantly based on the specific system you choose, but most of these systems are automated, increasing the maximum amount of heat possible from the collectors to the thermal store at predetermined intervals.

Pressurizing the System

Step 8

The closed-loop system will be filled with the unique heat transfer fluid, which is designed for solar heating systems that operate at temperatures up to 200°C.

It contains specially reversibly evaporable anti-corrosion chemicals to protect all metals found in solar heating systems. It also serves as an anti-freeze down to temperatures as low as -25.


What Is A Solar Thermal Pump Station?

Solar thermal systems may have pump stations to regulate the temperature in their hot water storage. The signal from the regulator activates the pump inside the components. For optimum circuit management, the solar thermal system must be properly filled with heat-conducting oil.

To what temperature can solar water heaters heat water?

The maximum temperature ratings for solar collectors are 180°F (82°C) for flat plate and liquid systems, and 210°F (99°C) for evacuated tube systems. These are the temperatures that the solar fluid can achieve, but the temperature of the water in storage will be lower.

How does a heat exchanger work?

The heat exchanger is used to transfer heat from the solar fluid to the water in storage. This can be done in a number of ways, but the most common method is to have the solar fluid flow through pipes in the storage tank, thereby heating the water indirectly.

Can I use an existing hot water tank?

You can, but it is not recommended. The solar system will work best if it has its own dedicated storage tank that is sized specifically for the system. This will ensure that the entire tank is used for solar storage and that the solar fluid has enough room to circulate properly.

How long do solar thermal systems last?

Solar thermal systems are designed for long life, typically 20 years or more. The collector panels have an expected life of about 30 years, while the other components have an expected life of 10-15 years. Regular maintenance will help to extend the life of the system.

What are the maintenance requirements?

Solar thermal systems require very little maintenance. The most important thing is to keep an eye on the fluid level in the storage tank and add more fluid if necessary. You should also have the system checked by a qualified technician every few years to make sure everything is working properly.

In Summary

So there you have it. A walk-through of what’s involved in a solar thermal installation.

This is by no means a complete guide but should give you a good idea of the process and what to expect.

About the Author

Passionate about helping households transition to sustainable energy with helpful information and resources.

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