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Types of Solar Collectors UK: A Comprehensive Overview

solar collectors

Solar collectors are a key component of solar thermal systems, helping to harness the sun's energy and convert it into usable heat for residential and commercial applications. In the UK, interest in solar collectors has grown as individuals and businesses seek clean, sustainable energy sources to reduce their carbon footprint and energy costs.

There are several types of solar collectors available, each suited to different settings and requirements. The most common type is the flat-plate collector, typically used in residential buildings where hot water demand is high. These collectors consist of an absorber, a transparent cover, and insulation, efficiently capturing and retaining the sun's energy for heating purposes. Another popular option is the evacuated flat-plate collector, which offers a more advanced design and increased efficiency in certain conditions .

When exploring solar collector options in the UK, it is crucial to consider factors such as geographical location, available sunlight, and specific energy needs. By selecting the appropriate type of solar collector, users can maximise the benefits of solar thermal systems in terms of energy savings, reduced carbon emissions, and long-term sustainability.

Fundamentals of Solar Collectors

Solar collectors are essential components of solar thermal systems designed to harness the sun's energy and convert it into heat. There are two main types of solar collectors used in the UK, namely flat plate collectors and evacuated tube collectors. Each collector type has its advantages and unique features, making them suitable for different applications.

Flat Plate Collectors

Flat plate collectors are the most common type of solar collector in residential applications. They consist of three primary components: an absorber, a transparent cover, and insulation. The absorber is responsible for capturing the sun's energy and converting it into heat, while the transparent cover allows sunlight to pass through and protects the absorber from the elements. Insulation minimises heat loss, ensuring the system operates efficiently.

Flat plate collectors are notable for their simplicity and durability. They can be mounted on various surfaces, including roofs, walls, or ground installations. Some advantages of flat plate collectors include:

  • Lower cost compared to evacuated tube collectors
  • Straightforward installation and maintenance
  • Robust design suitable for different climate conditions

Evacuated Tube Collectors

Evacuated tube collectors are more advanced and typically more efficient than flat plate collectors. They feature a series of glass tubes with a vacuum surrounding the absorber. The vacuum acts as an insulator, reducing heat loss and making the collector efficient even in cold or cloudy conditions. There are two main types of evacuated tube collectors: direct flow collectors and heat pipe collectors.

Direct flow collectors have a fluid-filled absorber within the vacuum tubes that directly transfers heat to the system. Heat pipe collectors, on the other hand, use a heat pipe and a heat exchanger to transfer heat from the absorber to the fluid. Evacuated tube collectors are advantageous for several reasons:

  • Higher efficiency, particularly in colder climates
  • Flexible orientation, maximising solar exposure
  • Minimal heat loss due to vacuum insulation

It is important to consider the specific requirements of your property and climate when selecting a solar collector type. Both flat plate collectors and evacuated tube collectors can provide significant energy savings and reduce dependence on fossil fuels for heating needs.

Types of Solar Collectors in the UK

In the UK, solar collectors play an essential role in harnessing solar energy for various purposes. Based on their structure and functionality, there are three main types of solar collectors: unglazed collectors, glazed collectors, and concentrating collectors. Each of these types has unique features, advantages, and applications.

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    Unglazed Collectors

    Unglazed collectors are the simplest form of solar collectors, often used for low-temperature applications such as pool heating. These collectors do not have a transparent cover or insulation, making them less efficient in colder climates. The primary advantage of unglazed collectors is their low cost and easy installation. Some common examples include:

    • Solar pool heating panels
    • Air collectors for space heating

    Although their efficiency is lower compared to other types of solar collectors, unglazed collectors can still provide significant energy savings in the right applications.

    Glazed Collectors

    Glazed collectors are more advanced and efficient compared to unglazed collectors. They comprise an absorber, a transparent cover (usually solar safety glass), and insulation to protect against heat loss. The most common type of glazed collector is the flat plate collector, which is widely used in residential buildings for hot water demand.

    Flat plate collectors are designed with different absorber types:

    1. Flat plate collectors with meandering tubes
    2. Flat plate collectors with grid-like pipes

    Another type of glazed collector is the evacuated tube collector, which features two main subcategories: direct flow collectors and heat pipe collectors.

    Concentrating Collectors

    Concentrating collectors use mirrors or lenses to concentrate sunlight onto a smaller absorber area, resulting in higher temperatures and increased efficiency. These collectors are mostly used for industrial or large-scale applications. Concentrating collectors can be classified into three types:

    • Parabolic trough collectors
    • Central receiver (tower) systems
    • Parabolic dish collectors

    While concentrating collectors can provide high thermal efficiencies, they are more complex and have higher installation and maintenance costs compared to flat plate or evacuated tube collectors, making them less suitable for residential use.

    Sizing and Efficiency of Solar Collectors

    Factors Affecting Efficiency

    Solar collector efficiency depends on several factors that impact the conversion of solar radiation into usable heat energy. The angle and orientation of the collectors, temperature difference between ambient and working temperature, and weather conditions such as cloud coverage are essential considerations. Additionally, the absorber's construction material and the European standard EN 12975 are important indicators of efficiency, which can be found in the appliance's datasheets.

    Comparing Solar Collectors

    There are two main types of solar collectors found in solar thermal systems:

    • Glazed flat plate collectors
    • Evacuated tube collectors
      • Direct flow collectors
      • Heat pipe collectors

    When comparing these collectors, it is crucial to evaluate their efficiencies based on performance, cost, environmental factors, and ease of installation. Spectral-splitting photovoltaic-thermal solar collectors are an emerging technology that has shown potential for higher efficiency by directing different parts of the solar spectrum to suitable receivers.

    Sizing Considerations

    Sizing solar collectors is essential to ensure that the system provides adequate hot water supply while avoiding oversizing or undersizing issues. Factors such as the size of the property, daily hot water consumption, and geographical location must be taken into account. Furthermore, solar collector sizing depends on the type of collector, efficiency, and the specific energy requirements for a building.

    In the UK, domestic water heating accounts for around 6% of total national delivered energy use. An average three-bedroom semi-detached house emits around 4,200 kg of CO2 per year, with hot water responsible for 864 kg of that total. Proper sizing of solar collectors can significantly reduce these emissions and save energy.

    Installation and Maintenance

    Site Selection

    When considering the installation of solar collectors in the UK, it's important to select the right site to maximise solar radiation absorption. The South West of the UK has the highest level of solar radiation, making it an ideal location for solar thermal systems.

    Roof-Mounted vs Ground-Mounted

    There are two common mounting options for solar collectors: roof-mounted and ground-mounted. Roof-mounted collectors are often more popular for domestic purposes due to their space-saving benefits and increased exposure to sunlight. Ground-mounted collectors can allow for easier maintenance access and the ability to adjust the angle throughout the year.

    Maintenance and Cleaning

    Maintenance and cleaning are crucial for the efficient performance of solar collectors. Solar thermal systems require periodic checks and servicing by qualified personnel to ensure proper operation and longevity. This includes inspecting mounts, seals, and connections, as well as maintaining the appropriate fluid levels and pressure within the system.

    Additionally, the cleanliness of solar collectors directly impacts efficiency. Over time, dust, dirt, and debris accumulate on the surface of collectors, reducing their ability to absorb sunlight. Regular cleaning of collectors helps maintain their efficiency and maximise energy production. However, caution is recommended during cleaning, especially for roof-mounted systems, to ensure safe access and avoid potential damage to the collectors.

    UK Policies and Incentives

    Feed-in Tariffs

    In the UK, the Feed-in Tariffs (FITs) scheme was designed to support the deployment of renewable electricity generation systems, including solar photovoltaic (PV) installations. It was introduced in 2010 and provided payments to individuals, businesses, and organisations for producing their own green electricity. The FITs scheme, however, was closed to new applicants on 31 March 2019, and is no longer available for new solar PV installations.

    The Renewable Heat Incentive

    The Renewable Heat Incentive (RHI) is another UK incentive supporting the transition to low-carbon heating. This scheme focuses on promoting technologies such as solar thermal systems and collectors. Eligible solar thermal technologies under the RHI include glazed flat plate solar collectors and evacuated tube solar collectors.

    Under the RHI, both domestic and non-domestic property owners can benefit from financial support for generating renewable heat. This encourages the adoption of solar thermal technology across various sectors in the UK.

    UK Climate Change Policies

    One of the key components of UK climate change policy is the commitment to achieving net-zero greenhouse gas emissions by 2050. In order to accomplish this goal, the government has implemented several policies and strategies, some of which directly impact and support the solar industry.

    • The Clean Growth Strategy: Launched in 2017, this strategy focuses on the decarbonisation of energy generation and consumption, with specific measures to promote renewable energy solutions, including solar power.
    • UK Solar PV Strategy: As part of the broader renewable energy policy, the UK Solar PV Strategy aims to enable the growth and development of the solar industry in the UK, addressing issues such as grid connectivity and financial incentives.

    These policies and incentives collectively contribute to the growth and adoption of solar collectors and renewable energy systems throughout the UK, aiding in the country's pursuit of a greener future.


    In the United Kingdom, various types of solar collectors are utilised to harness solar energy for different purposes. Solar collectors can be classified into two main categories: non-concentrating and concentrating collectors. Non-concentrating collectors, such as flat plate collectors and evacuated tube collectors, have the same size interceptors and absorbers, making them suitable for residential and commercial applications.

    On the other hand, concentrating collectors have larger interceptors than absorbers, focusing sunlight on a smaller area to generate a higher temperature. These types of collectors are more suitable for industrial applications where high temperatures are required.

    Researchers have been exploring novel technology such as spectral-splitting photovoltaic-thermal solar collectors which can generate both electricity and thermal energy simultaneously, potentially increasing efficiency.

    Solar collectors can contribute to significant energy savings and a reduction in CO₂ emissions when effectively integrated into a building's energy system. In the UK, the Energy Technology List (ETL) offers a comprehensive database of eligible solar thermal collectors, and financial incentives such as the Renewable Heat Incentive encourage their adoption.

    In summary, solar collectors are a vital component for harnessing solar energy in the United Kingdom, and continuous advancements in technology can only improve their efficiency and applicability across various sectors.

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    Mark McShane
    Content Writer
    Mark McShane is a seasoned professional in the solar industry and the owner of Skills Training Group, a leading provider of solar training and education. With years of experience in the field, Mark has developed a deep understanding of the latest trends, technologies and best practices in the industry. His expertise and passion for solar energy have helped countless professionals develop the skills and knowledge needed to succeed in the fast-growing field of solar energy. Whether you’re an aspiring solar professional or an experienced industry veteran, Mark is an excellent resource for anyone looking to enhance their skills and knowledge of the solar industry.
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