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thermal-stores-horizontalHartwell Manufacturing Ltd has been designing Thermal stores and buffer vessels for the green energy market for the last 10 years.  A typical Thermal Store would be manufactured from boiler grade mild steel plate, with internal sparge pipes and deflector plates which prevent the flow bypassing the stored water.  Due to the temperature range and pressure within the system Hartwell would manufacture the stores to a PD5500 Cat 2 standard.   It is possible to manufacture these to PD5500 Cat 1 and Cat 3 also. These are a fully insured and witnessed vessel.  It is possible in certain applications to manufacture these from Stainless Steel.

Thermal stores can be found in a variety of systems including domestic hot water (DHW), heating (LTHW,MTHW & HTHW), and process applications. The main theory behind Thermal Stores is to heat the vessel through periods of low demand and release the heat through high demand.  The ongoing focus today on sustainability has resulted in an ever increasing demand for renewable energy systems, with thermal storage being one of the critical elements of any heating or cooling scheme.

Retaining the heat is as critical as producing the heat, which is why Hartwell also offer the complete insulation and cladding of these vessels.  Hartwell can offer shop built tanks pre-insulated and clad ranging from 100 litres – 160,000 litres.  Hartwell Manufacturing has just been involved in manufacturing one of the largest site built domestic heating thermal stores in Britain 350,000 litre designed and manufactured insulated and clad within an existing building.

Hartwell are able to offer :

  • Design
  • Manufacture, shop or site built
  • Insulate and clad, shop or on site in aluminum, stainless or even corrugated
  • Deliver anywhere in the country
  •  Site inspection with one of our Appointed Persons
  • Lift plan
  • Erection by our experienced lift supervisors.

Thermal Stores

Thermal stores enable your organisation to become extremely energy efficient. By collecting and storing heat energy from an extensive range of different sources, the energy can then be used to heat a space or depending on your requirements, to heat liquids.

A thermal store is also known as an accumulator tank and can be used to collect heat energy from various different sources. Renewable sources such as solar panels, wind turbines, heat pumps and biomass boilers can all be connected to the thermal store. Energy is then held within until it is required whether that be immediately or later on.

Hartwell Manufacturing have been around for more than three decades providing clients with manufacturing, fabrication and mechanical services. We have been offering thermal stores and buffer vessels to both the green energy market or any industry looking to take a more environmentally friendly approach to their operations.

About Our Stores

A typical Hartwell Manufacturing Ltd thermal store will be manufactured with boiler grade mild steel plate for maximum efficiency. As a result of temperature ranges within the thermal vessel, the store would be manufactured to a PD5500 Cat 2 standard, however both Cat1 and Cat 3 are also available where required. Our vessels are fully witnessed and insured and can in certain instances also be fabricated from stainless steel.

With an ever increasing focus on being environmentally friendly and sustainable, our thermal stores are designed to collect heat energy in times of low demand when a surplus is generated. This can then be stored and used in times of high demand rather than relying on other, less cost and fuel efficient methods.

Heat retention is of course the most important characteristic of a thermal store. As such, Hartwell offer cladding and insulation to ensure our vessels perform to optimal levels.


We are able to offer pre-insulated tanks ranging from 100 litres all the way up to 160,000 litres and in some instances beyond. As a testament to our capabilities, Hartwell Manufacturing was recently involved in the manufacture of one of Britain’s largest domestic heating thermal stores. The 350,000 litre store was created to be installed within an existing building.

Our Capabilities

Hartwell Manufacturing Ltd is the perfect company to assist your organisation in becoming more sustainable. Not only are our thermal stores tried and tested but they can also be created to your exact specifications and we can complete the process for you from design to install.

Your relationship with Hartwell Manufacturing would include:

  • Thermal Store Design
  • Shop Manufacture or Site Build
  • Shop or on Site Insulation in Aluminium, Stainless Steel or Corrugated
  • Countrywide Delivery
  • Site Inspection
  • Full Lift Plan
  • Site Erection by our Experienced Supervisors

Get In Touch
To discuss your thermal store project and take the first step towards a more sustainable, energy efficient organisation, why not call one of our representatives today? We can talk you through the entire process and even plan a site visit.

Hartwell Manufacturing are a privately owned company, who have been providing high-quality machining and fabrication services to the industry, since 1974.

Get in touch today!
01924 262825

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