Thermo Dynamics

Thermo Dynamics

What exactly is Thermo Dynamics?
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Thermodynamic Panels

Thermodynamic panels are designed to produce hot water for both domestic and commercial usage. These systems are more formally known as Solar Assisted Heat Pumps. This term helps to explain how and where this type of product fits into the renewable energy spectrum. A thermodynamic panel is a halfway house between a solar panel and a heat pump. The primary purpose of this product is to provide heat energy in the form of hot water predominantly

The products have been developed as a more efficient alternative to air source heat pumps by including the use of solar gain / radiation. This means that a thermodynamic system can benefit from both the ambient air temperature, like a heat pump, as well as the solar radiation, like a solar thermo system.

This best of both worlds approach will often result in an improved COP (coefficiency of performance). These products have been designed with a life expectancy of roughly 20 years by some manufacturers; however they have only really started to take hold in the UK over the last 6-8 years. Initially there was lots of scepticism and uncertainty surrounding this new renewable energy system as it found its feet in the UK. However, in early the first thermodynamic products were granted Microgeneration Certification Scheme (MCS) approval. This dramatically increased consumer and trade confidence.

The Working Principle

An ecological fluid passes through the solar panel at a temperature of -15ºC, thereby allowing the collection of the energy from the sun, rain and wind. As the fluid is running at negative temperatures, it collects the heat from the air by natural convection, working also at night

The fluid is then compressed, in the Solar Box which causes the fluid temperature to increase. The heat is then released into the circulating water by way of a high performance plate heat exchanger.

Finally, the fluid goes through an expansion valve and will evaporate into the aluminium solar panel and the process repeats.

How does a TD System Work?

A thermodynamic system works by sending a very cold liquid refrigerant around a panel on the outside of a property. The temperature of the liquid is approximately -22°C when it enters the panel. As the liquid flows through the veins in the panel it absorbs heat energy from the air surrounding the panel. This is where the term Thermodynamics comes from, as it is a scientific terms used to explain heat energy and its movements. The liquid refrigerant will vaporise into a gas once its temperature reaches approximately -15°C. This is more commonly known as its boiling point. The gas exits the panel and is circulated back to a compressor inside the thermodynamic unit. The compressor job is to compress the gas and send it under pressure through a heating element or plate. When a gas is compressed is gives off heat energy. The heating element is a way of distributing the heat into the store of water. Once the gas has lost its heat it exits the element and passes through an expansion value, which releases the pressure. This drop in pressure and loss of heat energy means that the gas condenses back to a liquid for the cycle to begin again.

The water inside the thermodynamic unit /cylinder is constantly monitored and kept hot by a thermostat. The thermostat will switch the system off once it reaches its required temperature. Most thermodynamic suppliers will set the stored water temperature of a domestic unit at 55°C. This is considered to be sufficiently hot for domestic hot water purposes, yet remaining safe for use. However, this temperature setting can be amended if necessary. Commercial units can be set at much higher temperature if needed.

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Types of TD Systems

There are two main ways that a thermodynamic unit can be set up for a domestic property. The first is to install a small thermodynamic unit, usually no larger than 50cm by 50cm, which is designed to work with a normal hot water cylinder. The water from the standard hot water cylinder is pumped to the thermodynamic unit and is heated over a heating plate. These systems are ideal if you are restricted on space, for example a tight airing cupboard. These systems can be linked up with a maximum of about 250lt cylinder capacity.

The second and more costly thermodynamic system set up is to take out the existing cylinder and replace it with an all in one cylinder/thermodynamic unit. These units come in a range of sizes and cylinder capacities (75, 150, 160, 180, 200, 210, 250, 280, 300, 500lt). This set up is the most efficient way of installing and running a thermodynamic unit, if you have the space. The water is directly heated by a coil/element in the storage tank within the unit. This means there is no heat loss from piping the water to an external heating unit. These systems can be fitted to both vented and unvented hot water systems. Quite often an old copper cylinder with poor lagging is replaced with the new thermodynamic unit, which means because of its modern insulation the heat is also retained more efficiently within the new cylinder. The larger 300lt & 500lt units are more commonly used for places with higher hot water demand, such as restaurants, B&Bs, hotels, hair dressers, farms etc…These larger units would often come with more panels, usually 2 or 4, which helps increase energy absorption and speed up recovery time. Manufacturers typically say that 200lt of water can be heated from normal tap water temperature up to 55°C in approximately 3-4 hours, but once achieved it is then constantly maintained.

What is a TD System made of?

A thermodynamics panel is roughly about the size of a standard door, 2m by 1m. The panels are made from anodised aluminium. The anodizing is an electrochemical process that converts the surface of the metal panel into a non-corrosive, durable finish. Inside the property / premises there would be a main unit. This unit consists of two sections, one of which holds the electronics and working parts, the other contains a water storage area. Thermodynamic units come in lots of different sizes dependent on the amount of water needed and storage capacity. Inside the unit you would find a compressor, circuit board, wiring, heating plate or element, expansion value and a backup immersion heater. Some units also come with a secondary coil built into the storage tank so that the existing boiler or additional heat source can be connected up.

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The Benefits of thermo Dynamics?

  • water up to 55ºC
  • Aluminium Solar Panel with high corrosion resistance
  • Retro fits to existing cylinder.
  • Compatible with both vented and unvented systems
  • Very compact unit
  • 5 year manufacturers guarantee for the solar panel
  • High Performance Plate Heat Exchanger Suitable for DHW
  • Circulation Pump Suitable for DHW
  • No maintenance required
  • Environmentally friendly fluid
  • Significantly reduces carbon emissions
  • The Solar Panel can be mounted on the wall, or roof
  • The Solar Box can be hung on the wall or be place on the floor
  • No glass or other fragile materials
  • Fine European and internationally recognized brand

Yes. The fluid passes through the panel at very low temperatures. It can therefore receive more solar energy than a normal liquid, even on days without sun or at night. Because of this thermo difference, the solar panel can capture the heat existing in the environment and transmit it to the water.

Maintenance is non-existent and the fluid does not need to be recharged.

Find out more

Running Costs

The running cost of each thermodynamic unit is dependent on the size of the unit and compressor within, the volume of water being heated, the length of pipe run to the panels, the amount of hot water the property requires. Domestic systems will require between 300-450w of power when in use. An average domestic house would have approximately 200lt of storage capacity; this means that if the thermodynamic unit was running for 6 hours a day (2x complete fill & heating of 200lt tank) the unit would cost you approximately 30p. Most providers state that a typical house would expect to pay between £40-60 per year in electrical running cost. Commercial units will typically range between £150-£500 per year to run, dependent on specific hot water requirements.

The Maintenance

Thermodynamic systems do not need any maintenance. This is because they have very few moving parts and are a sealed system. Once the gas lines and panel/s have been correctly installed and filled with the refrigerant there should be no need to top up or maintain the system in the future. A qualified F-Gas engineer should vac down the entire system (suck all air out of the system) prior to inserting the refrigerant. This process removes imperfections such as particles of dust or water vapour, which could hamper the performance of the unit. Once the refrigerant is put into the system a pressure test should then be undertaken to determine the correct level of refrigerant needed and to check for any leaks. We always use a qualified F-Gas engineer.

Method One of Panel Mounting

The most common and often cheapest way of installing a thermodynamic panel is to wall mount. This is achieved by using 6 stainless steel brackets that fix directly to an external wall. If multiple panels are needed for larger installations the thermodynamic panels can be racked. This is because they do not need sunlight to operated, and will work as long as there is sufficient air movement around the panels. Thermodynamic panels can be installed onto a roof. This type of installation is very similar to how Solar PV panels are installed. Stainless steel runners will go along the roof for the panels to sit on and attach too. These runners are then attached to the joist via a metal clasp that slides under the tiles.

The First Mounting Method

thermo Dyanmics Panel Mounting Method 1

Method Two of Panel Mounting

Panels can be installed on a flat roof using specially made a-frames. The panels must be louvered to a minimum of 15 degrees so that water can run off.

The Second Mounting Method

thermo Dyanmics Panel Mounting Method 2

Will a Thermo Dynamic System add

There is no concrete evidence to suggest with certainty that a thermodynamic system will add value to your property. However, since the introduction of the EPC (Energy Performance Certificate), which all properties must have when, being bought or sold, consumer awareness of properties energy performance has greatly improved. If a property comes with a low EPC grade this could suggest to the buyer that investment may be needed to improve its energy efficiency once bought. In 2016 the first thermodynamic units were incorporated into SAP calculations, which meant that they would have an effect on a buildings energy rating.

Value to my house?

If you are thinking of selling your house after having installed a thermodynamic system it may be possible to keep the system and take it to your next property. This is very much dependent on the type of system purchased and its set up. Thermodynamic systems are not designed to replace an existing boiler, just switch the domestic hot water off, therefore if a system were uninstalled the property could revert back to the existing boiler / heat source. Not all providers offer this option, and if they do consumers would have to factor in the additional labour cost of uninstall and reinstallation.

The Planning Permissions

The installation of thermodynamic panels in England and Wales is classified as ‘permitted development’ which means that no planning permission is needed. There are however a few exceptions to this rule. If you are looking to install on a Listed Building you must take the necessary steps to obtain planning permission through your local council. If you live in an AONB (Area of Outstanding Natural Beauty) it is advised that you discuss your plans and panel positions with the local authority. If you live in a conservation area no planning permission is needed, however the panel/s must not be visible from the main highway / front of house.


MCS (Microgeneration Certificate Scheme) is the government backed approval of renewable technologies for application in the UK. Thermodynamic panels were first included on the MCS register back in 2013. The panels were however quickly rescinded from this approval, due to a false classification, resulting in them being de-registered. This removal from the MSC register knocked consumer confidence in the technology; however what consumers were not told was that the panels were registered under the wrong classification of renewable energy, Solar thermo. In 2015 MCS created a new category specifically for thermodynamic panels known as ‘Solar Assisted Heat Pumps’. The first thermodynamic panel manufacturers and products achieved MCS approval in early 2016. This approval has helped the thermodynamic panel industry to flourish over the coming year. Furthermore news was released mid 2015 that Solar thermo would be losing its RHI (Renewable Heat Incentive) payments in early 2017. This helped to further strengthen the appeal of thermodynamic systems over the ageing technology of solar thermo.


Although thermodynamic panels are now MCS approved they do not qualify for RHI. Therefore the systems cost effectiveness needs to be judged on its energy savings along. Although an RHI payment would be good for consumers the general consensus among thermodynamic manufacturers is that they don’t want to repeat the turmoil of the Solar PV industry, with subsidies being given and then reduced / taken away. They hope that the systems will still make financial and commercial sense without payment assistance from the government. This will help to create a more stable industry able to stand on its own two feet, without being propped up by the government. Early signs of this seem positive.

Potential savings of a TD System

The savings for each individual thermodynamic system will widely vary, based on energy consumption, hot water consumption. There are a few things you can do to maximise your systems performance, such as: Panels can be placed up to about 20m pipe run from the unit, however reducing this run can help save on the electrical running cost. If you can face the panels towards south in an open area you will also benefit from extra performance, due to solar gain. The average ambient air temperature will also play a part in the overall performance of each system.

Despite these variances thermodynamic units appear to have a very low running cost, with manufactories displaying figures of 300w – 450w of electrical consumption when in use. This means that it would cost you between 3-4 pence per hour to run a thermodynamic unit. Systems typically only run for a few hours a day as when the water reaches temperature the unit will automatically turn off. Therefore the equation for working out savings would be as follows:

Domestic Hot Water Cost - Running Cost = Total Savings

The main variable in the equation is the domestic hot water cost. For some this is hard to decipher as it is all lumped into a gas, oil, electric or LPG bill. This will also vary based on the number of people in the property, hot water usage, boiler set up (combi or cylinder) and hot water system type (unvented or vented). Combi boilers will have a lower percentage of hot water on the bill compared to a cylinder system, as they only heat hot water on demand, whereas cylinders heat and maintain the entire water volume within. As an average guidance hot water can represent between 30-40% of a typical domestic properties fuel bill.

Cost of a thermo Dynamic System

Potential differences in the initial costing’s will vary from project to project. For example, plumbing costs may be higher if the building has a complicated or antiquated water system. The installation costs could be significantly higher if scaffolding is required. The size of system (number of panels and water cylinder capacity) you will need depends on the hot water demand of your home. The average person will use around 50 litres of hot water each day; a normal 3/4 bedroom house would require a 200 litre unit/cylinder.

We have the experience and the correct installation teams and qualified F-Gas engineers. Thermodynamic systems shouldn’t be installed by conventional plumbers alone. This is why the DIY thermodynamic panel market doesn’t really exist.

Technical Drawings

thermo Dyanmics Diagram Table
thermo Dyanmics Diagram

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