Solar Heating Explained: Understanding How The System Works

When it comes to a solar heating system, it’s important to understand that keeping up with maintenance is the key to keeping your solar hot water equipment in tip-top condition. With proper care, solar heating can provide reliable, renewable energy for over 25 years.

The Basics of Solar Heating

Solar thermal panels, also known as solar collectors, work by absorbing solar radiation and converting it into heat energy. This energy is then used to heat water for domestic or commercial use.

A typical active solar heating system includes:

• A solar collector (either flat plate solar collectors or evacuated tube collectors). An active solar heating system uses mechanical devices, such as pumps and controllers, to actively collect, convert, and supply solar heat.

• A heat transfer fluid, usually a pre-mixed glycol-based liquid

• A solar hot water cylinder or hot water tank

• Heat exchangers are inside the cylinder. Heat exchangers are essential for transferring heat between collectors, storage tanks, and working mediums in various solar thermal system configurations.

• Pumps, valves, a system control panel, and sensors (the control systems). These are characteristic of an active system, which uses mechanical components for forced circulation, as opposed to passive systems that rely on natural convection.

• A storage tank to hold the hot water, ensuring heat storage for later use

These system components work together in a closed loop, using solar power to deliver heat. Active solar heating systems use mechanical components like pumps and controllers to improve efficiency and heat transfer, compared to passive systems, which rely on gravity or convection. Active systems use pumps, controllers, and valves to circulate fluids and enhance heat transfer efficiency.

How Does a Solar Heating System Work?

The process begins with solar panels mounted on your roof. They’re designed to collect solar energy by capturing the sun’s rays and collecting heat, generating thermal energy in the process. This harnesses the sun’s energy for your heating needs.

This heat warms a pre-mixed glycol fluid, which serves as the heat transfer fluid and comes in 10-litre containers. Using a pre-mixed solution reduces the risk of incorrect mixing ratios. If needed, a refractometer can be used to measure fluid strength.

The fluid runs through a sealed, pressurised loop made from either copper or pre-formed corrugated stainless steel, the latter being preferred because it allows for natural expansion and contraction as the system heats and cools.

Cold water enters the system before being heated. This sealed loop connects solar collectors at one end and a twin-coiled hot water cylinder at the other. The heat exchanger inside the cylinder allows the hot solar fluid to heat your domestic water supply, effectively heating water for household use, without mixing. This heated water is then stored in your storage system, ready for use.

Solar thermal panels work by capturing solar energy and transferring it directly to heat water, making them efficient for both domestic hot water and space heating applications.

The system is controlled by a solar thermal pump station. When sensors on the solar collector detect a higher temperature than those on the hot water cylinder, the pump activates and circulates the fluid using a solar heating flexible pipe to copper tube connectors. Once both sensors read the same temperature, the pump switches off, conserving energy and maintaining sufficient heat.

Types of Solar Heating Systems

Solar energy systems come in two main forms under the solar thermal category:

• Solar water heating systems are designed to supply domestic hot water

• Active space heating systems are systems that use mechanical components such as solar collectors, pumps, controllers, and thermal storage to circulate heat transfer fluids and deliver warmth to rooms through underfloor heating or radiator circuits. An active space heating system supplements passive methods by reliably meeting building heating demands, especially when solar gain alone is insufficient.

Active systems for space heating use mechanical devices to circulate heat transfer fluids, making them more efficient and controllable than passive systems.

While most UK homes benefit from solar water heating, larger homes and commercial buildings can boost performance by combining solar with a heat pump, conventional boiler, or even solar-assisted heat pumps, where the primary heat source can be solar, a heat pump, or a conventional boiler, depending on system design. In hybrid setups, these systems can utilise multiple energy sources, including solar, ground heat, and auxiliary systems.

By relying on renewable energy sources, these systems help reduce reliance on fossil fuels and lower environmental impact.

Components of a Solar Heating System

A solar heating system is made up of several essential components that work together to deliver efficient, renewable heat energy for your home. At the heart of the system are solar thermal panels, which are designed to capture solar radiation and convert it into usable heat energy. This heat is then transferred via a heat transfer fluid, typically a glycol-based liquid, circulated through the system by a pump.

The heat transfer fluid carries the collected heat to a heat exchanger, where the energy is used to heat water or air for space heating or domestic hot water. A storage tank is included to store excess heat energy, ensuring you have hot water or heating available even when the sun isn’t shining. The system is managed by a control system that regulates the flow of heat energy, optimising performance and efficiency.

To ensure consistent comfort, many solar heating systems also include a backup heating system, such as a conventional boiler or a heat pump. These backups provide supplemental heat during periods of low solar energy availability, such as during extended cloudy weather or at night. Together, these components create a reliable and sustainable heating system that maximises the benefits of solar energy for your home.

Solar Water Heating

Solar water heating systems are one of the most popular and effective ways to harness solar energy for your home. Using solar thermal panels, these systems capture solar radiation and convert it into heat energy, which is then used to heat water for everyday use. The main components include a solar collector, a hot water cylinder, and a pump that circulates the heat transfer fluid throughout the system.

The solar collector absorbs the sun’s energy and transfers the heat to the fluid, which then flows through a heat exchanger inside the hot water cylinder. This process efficiently heats your household water, providing a reliable supply of hot water while significantly reducing your energy bills and carbon footprint. In many cases, solar water heating systems can meet a large portion of your home’s hot water needs, especially during the summer months.

Solar water heating systems may be eligible for the Renewable Heat Incentive (RHI), which offers quarterly payments for seven years based on the amount of renewable heat generated. This not only helps offset installation costs but also rewards you for choosing a sustainable, energy-saving solution for your home.

Seasonal Performance and Backups

Although solar water heating systems work well for 80–90% of the year, UK weather means performance drops during winter. In cold climates, solar heating systems may require special adaptations or integration with other technologies to maintain efficiency. In the heating season, additional sources may be needed, such as:

• A natural gas or oil boiler

• A 230v immersion heater

• A solar PV panel setup with a smart controller to redirect surplus power to the hot water cylinder, generating electricity for heating

• The ambient heat from your central heating system

These hybrid setups, which can combine thermal solar panels with other systems, ensure access to hot water year-round, maximising your system’s flexibility while still reducing your carbon footprint.

Installing Solar Thermal Panels

When installing solar thermal panels, roof orientation, angle, and size all play a role in performance. A south-facing roof with minimal shade is ideal. Flat plate solar collectors are more common in the UK and are easy to mount on pitched roofs. Evacuated tube collectors offer greater efficiency, particularly in cooler climates or where space is limited.

It’s also important to ensure your solar hot water cylinder is appropriately sized to store enough hot water when solar energy is available. Hot water usage patterns should be considered to ensure adequate storage and system efficiency. Integration with your existing heating system should be considered early in the design phase.

Heat exchangers are essential for transferring heat between solar collectors, storage tanks, and the heating system. In forced-air heating systems, a heating coil can be installed in the ductwork to transfer heat from solar-heated liquids to the air in your building.

Building Codes and Regulations

Before installing solar thermal panels, it’s crucial to ensure your solar heating system complies with all relevant building codes and regulations. These rules are in place to guarantee the structural integrity of your installation, adherence to electrical standards, and compliance with local zoning restrictions. Homeowners should always check with their local authorities to understand the specific requirements for their area, as these can vary widely.

In addition to government regulations, you may also need to consider local council planning permissions and any restrictions imposed by conservation areas or listed building status that could affect your ability to install solar thermal panels. Securing these before starting your project will help you avoid costly delays and ensure your solar heating system is safe, efficient, and fully compliant. By following these guidelines, you’ll not only protect your investment but also help minimise your carbon footprint through responsible installation practices.

Solar Heating System Maintenance

Solar hot water maintenance is simple but crucial. Regularly monitor the pressure system gauge: if the pressure drops below 2 bar, your system won’t operate effectively. In hot conditions, the temperature of the fluid may increase by up to 50%. As it cools back to ambient temperature, the pressure should stabilise. If it doesn’t, you may have a solar heating system leak.

Leaks can occur at pipe joints, either on the roof or around the pump station. If a leak is suspected:

1. Drain the old fluid safely

2. Replace any damaged or broken components

3. Refill with new heat transfer fluid

4. Re-pressurise using the system control panel to manufacturer-specified levels

Repairs and Replacement Parts

From worn seals to faulty sensors, any part of your solar system can wear out over time. That’s why we stock a wide range of solar water heating system spare parts, including:

• Solar collectors and mounting brackets

• Pumps and flow meters

• Controllers and sensors

• Pre-mixed glycol fluid

• Pipes, fittings, and connectors

If you’re struggling to identify the issue, our support team can assist in sourcing the correct part to get your solar heating system back up and running quickly.

Financial Benefits and Energy Savings

Solar water heating is a proven way to lower your energy costs and environmental impact by utilising natural energy from the sun. While the Renewable Heat Incentive has closed to new applicants, solar remains a solid long-term investment. When combined with solar PV, you can generate electricity and use the excess energy to heat water—effectively creating a dual-use solar energy setup.

For more information on the costs, benefits, and available funding schemes for solar water heating, consult the Energy Saving Trust, which offers guidance and advice on energy-saving solutions.

Incentives and Financing

Adopting solar heating systems is more affordable than ever, thanks to a range of incentives and financing options. In the UK, the Renewable Heat Incentive (RHI) scheme provides financial support to households and businesses that install renewable heat technologies, including solar thermal systems. This incentive offers regular payments based on the amount of renewable heat your system generates, making it easier to recoup your investment.

Many solar panel installers also offer flexible financing options or discounts for solar water heating systems, helping to spread the upfront costs over time. Additionally, government grants and tax credits may be available to further reduce the expense of installing solar thermal panels. By taking advantage of these incentives, you can lower your energy bills, make your home more energy-efficient, and contribute to a greener future—all while enjoying the benefits of a modern solar heating system.

Reducing Your Carbon Footprint

Solar heating systems are a powerful way to reduce your carbon footprint and support a more sustainable lifestyle. By installing solar thermal panels, you harness renewable energy from the sun to provide hot water and heating for your home, cutting down on the need for fossil fuels and lowering greenhouse gas emissions. Solar water heating systems not only help you save on energy bills but also offer a reliable, eco-friendly source of hot water year-round.

Choosing to install solar thermal panels is a significant step toward reducing your household’s environmental impact. With the latest solar technology, you can enjoy the comfort of modern heating systems while making a positive contribution to the planet. Every home that adopts solar heating brings us closer to a cleaner, more energy-efficient future.

Why Choose Solar PV Systems?

At Solar PV Systems, we specialise in providing high-quality solar thermal and solar PV solutions. Whether you’re a homeowner or an installer, we’re here to support you with everything you need to get the best from your solar heating system.

Long-Term Reliability

We only supply products we trust, built to perform and made to last. Our solar thermal panels, solar PV kits, and components are backed by long service lifespans, with many designed to operate efficiently for 25 years or more.

Everything You Need, All in One Place

We stock a wide range of components, from full solar hot water systems to individual parts like collectors, pump stations, control panels, and pre-mixed heat transfer fluid. If you’re maintaining an existing setup or building a new one, we’ve got you covered.

Systems That Work Around You

Our systems are designed to integrate with a variety of existing heating systems, including conventional boilers, immersion heaters, and heat pumps. We offer flexible solutions that work for your home or business, whatever the size or layout.

Expert Advice When You Need It

We understand that no two installations are the same. That’s why we offer a consultancy service to help you plan the right setup, choose the right components, and get the best performance from your system.

Fast Delivery and Personal Support

With most items in stock here in the UK, we can get parts to you quickly. If you’re not sure what you need, or you’ve run into a problem with your system, just get in touch – we’ll help you find a solution.

Whether you’re installing solar thermal panels for the first time or keeping your current system running smoothly, we’re here to help you every step of the way.