Solar Thermal or Solar Water Heating Systems: Using the Sun's Power for Heat

Solar thermal, also known as solar water heating, is a technology that harnesses the heat from the sun to provide hot water for various applications. It is a renewable and environmentally friendly alternative to conventional water heating methods that rely on fossil fuels or electricity.

Solar thermal systems are the perfect choice for DHW heating and central heating backup. By harnessing freely available solar energy, you can save on the use of fossil fuels. What's more, investments in solar thermal energy pay off in just a few years. Essentially, you have the option to use solar energy for heating your domestic hot water (DHW) and as a backup for central heating. Savings on oil and gas are substantial in every case, as you will be able to reduce your annual energy consumption by around 60%. This is the energy that would typically be needed for your daily DHW heating. If you combine the heating of DHW and heating water, you will save about 35% of the overall energy needed annually.

How does solar thermal technology work?

Solar thermal systems typically consist of solar collectors, a heat transfer fluid, and a storage tank.

1. Solar Collectors: They are designed to absorb the sun's energy and convert it into heat. The most common types of solar collectors used in solar thermal systems are flat-plate collectors and evacuated tube collectors. They are typically mounted on rooftops, walls, or ground-mounted structures.
2. Heat Transfer Fluid: A heat transfer fluid circulates through the solar collectors to absorb the heat from the sun. This fluid transfers the captured heat to the storage and distribution system.
3. Heat Storage and Distribution: The heat transfer fluid carries the collected thermal energy to a storage tank or heat exchanger. This storage allows for the use of the captured heat when sunlight is not available, such as during cloudy periods or at night. The stored heat can then be used for space heating, domestic hot water, or other applications.
4. Backup Heating System: In some installations, especially in colder climates or during periods of low solar radiation, a backup heating system (e.g., gas, electric, or oil-based) may be integrated into the system to guarantee heat source even when solar energy is insufficient.
5. Pump and Controls: Circulation pumps are used to move the heat transfer fluid between the collectors and the storage system. Control systems and sensors monitor the temperature and regulate the flow of the heat transfer fluid for optimal performance and energy efficiency.

Let's explore some key aspects of solar thermal technology

What is the solar hot water efficiency in the UK?

A solar thermal system designed for heating water has the capacity to generate approximately 40% to 70% of a four-person household's annual hot water demand. Its efficiency depends on its position on your home, the amount of sunlight it’s able to capture, and the time of year. Generally, upon installation of a solar water heating unit, you can anticipate a reduction of 50% to 80% in your expenses related to water heating. Moreover, because sunlight is free, you are protected against potential fuel shortages and increases in costs.

How much energy can I save with a solar water heater?

On average, a well-designed solar water heating system can provide a significant portion of your hot water needs, leading to notable energy and cost savings over time.

One important area of potential savings is offered by heating domestic hot water (DHW). Utilising solar collectors along with a DHW storage tank proves to be a compelling option instead of relying solely on boilers, especially in the summer. In a detached house, solar energy covers up to 60 percent of the energy required for DHW heating. By integrating DHW and space heating, you can achieve an annual energy saving of about 35 percent. Even in transitional seasons like spring and fall, it's possible to frequently rely on solar energy to support your central heating, allowing you to potentially switch off your boiler.

Solar Thermal Heating & Hot Water Systems

What are the benefits of using solar thermal systems?

Solar thermal systems offer several benefits:

• Endless amounts of energy, which is free of charge.
• Lower carbon emissions and smaller environmental footprint: No CO2 emissions during operation
• Reduced energy bills: up to 60% less energy to heat water, up to 35% less energy for space heating
• Decreased reliance on fossil fuels: Reduced consumption of fossil fuels
• Solar thermal systems can be integrated into existing systems
• Modern systems work efficiently even in winter. They can provide a consistent and reliable source of heat, making them a cost-effective and sustainable choice for both residential and commercial applications.

What are the different types of solar thermal hot water collectors?

There are several types of solar thermal collectors, including evacuated tube collectors, flat-plate collectors and concentrating collectors like parabolic troughs and dish collectors. Each type has its unique design and efficiency characteristics, catering to various needs and geographic locations.

The evacuated tube solar thermal system is the most widely used solar thermal collector. This is the most effective and frequently used method for generating solar thermal energy with an impressive efficiency rate of 70 percent. To illustrate, if the collector produces 3000 kilowatt hours of energy annually, about 2000 kilowatt hours would be employed within the system to heat water.

In heat pipe systems, the liquid used to capture solar heat doesn't move directly through the tubes. Instead, another liquid evaporates in a part called the heat pipe beneath the main heat-collecting part, and this evaporation transfers heat to the solar liquid.

The heat pipes are connected inside the header without containing any liquid. The collector itself only has a small amount of fluid. Additionally, there's a feature called ThermProtect that makes the system shut down automatically if the temperature gets too high. All these things together make sure that the system works really reliably.

Below is an installation at Gower, Swansea completed by Solar Save Renewables in August 2023, using the highly efficient vacuum tube collectors based on the heat pipe principle with ThermProtect. Viessmann solar collectors are also designed for an exceptionally long service life.

Upgrading an Old Solar Thermal Installation in Gower, Swansea

What is the difference between solar thermal and solar photovoltaic (PV) systems?

Solar thermal systems focus on capturing and utilising solar energy for heat, while solar photovoltaic (PV) systems convert sunlight directly into electricity. Solar thermal is more suited for heating applications, while PV is ideal for generating electricity.

How much does it cost to install a solar thermal system?

The cost of installing a solar thermal system varies based on factors such as system size, type of collector, location, and installation complexity. However, typically, you can anticipate a cost ranging from £3,000 to £8,000 (inclusive of a discounted 5% VAT). These figures include installation costs and all parts (solar collectors, control panel, pipes, hot water tank).

The overall cost of your system will be impacted by the specific type and quality of panels you select, as well as factors such as the complexity and age of your water system, required plumbing adjustments, or the potential need for scaffolding. Further costs might arise from the integration with current systems.

While upfront costs can be significant, the long-term savings on energy bills often make solar thermal systems a worthwhile investment.

For an average 3–4 bedroom house, how many collectors and what size water cylinder would be necessary to meet the daily hot water demand?

The system size (collectors and water cylinder) depends on how much hot water you need for your home. A simple guideline is 1m² per person in the building. Usually, solar collectors are 2-3m² each. So, for an average 3–4-bedroom house, 2 collectors are needed.

Considering that each person uses about 50 liters of hot water daily, a regular 4-bedroom house would need a 200-liter tank.

Can solar thermal systems be used for space heating?

Absolutely, solar thermal systems can be used for space heating. Solar thermal systems harness the energy from the sun to heat a fluid (such as water or air), which is then used to provide heat for various applications, including space heating. However, it's important to note that the effectiveness of solar thermal systems for space heating can vary based on the location and climate. In areas with plenty of sunlight and hot weather, these systems can be quite beneficial. In colder climates or areas with limited sunlight, additional heating sources might still be necessary during periods of low solar energy availability.

How efficient are solar thermal systems compared to traditional heating methods?

Solar thermal heating is different from using fossil fuels because it uses the sun's energy, which is unlimited, clean, and free. New heating systems can work with solar panels to heat water and add warmth to your home's heating. This type of heating is called solar thermal heating. It's not the same as making electricity from sunlight, which is called photovoltaics. Solar thermal systems can be highly efficient, especially for heating applications, and can outperform many traditional heating methods in terms of energy efficiency and sustainability.

Here are the good things about solar heating:

• Lots of free energy
• No pollution when it's working
• Saves money – up to 60% less energy to heat water and up to 35% less for heating your home
• Uses less polluting fuels
• Can be added to existing systems
• Even works well in winter with modern systems.

What maintenance is required for solar thermal collectors?

Solar thermal systems have a big plus: they're not expensive to run and require minimal maintenance, unlike regular heating systems. Once installed, you don't need to do much – just do periodic check for leaks, clean the collector surfaces, and ensure proper fluid levels. And the best part is, you don't have to pay for fuel, so you save money over time. This makes solar thermal systems a smart choice for people who want heating that's both affordable and good for the environment.

How long does a solar thermal system typically last?

A well-maintained solar thermal system can last 20 to 30 years or more, depending on the quality of components and regular maintenance. At Solar Save Renewables, we prioritise top-quality solar thermal products, which is why we have specifically chosen to work with Viessmann. Their solar collectors are designed for an exceptionally long service life. This is guaranteed by the use of high-grade, corrosion-resistant materials, such as glass, aluminum, copper, and stainless steel. The absorber is an integral part of the vacuum tube. This protects it from weather influences and contamination, and ensures high energy yields for years to come.

Can I integrate solar thermal into my existing heating or hot water system?

Yes, Solar thermal can be integrated into existing systems through a heat exchanger, which transfers the collected solar heat to your existing distribution system.

Can solar thermal systems be used in combination with other renewable energy sources?

Yes, solar thermal systems can be integrated with other renewable sources like solar PV or wind power to create hybrid energy solutions.

What materials are used in solar thermal collectors, and are they recyclable?

Solar thermal collectors typically use materials like metals, glass, and insulation, many of which are recyclable.

Can solar thermal systems be used in off-grid or remote areas?

Yes, solar thermal systems can be an excellent choice for off-grid or remote areas, providing a reliable source of heat without the need for extensive infrastructure.

If you have any questions please do not hesitate to contact us here

We assess how solar thermal heating can fit your home and work with your current heating or suggest the best solution.

We specialise in installing solar panels designed for heating hot water in Carmarthenshire, Pembrokeshire, Ceredigion, Swansea, South, and Mid Wales.