McDonald Alternative Energy

Alternative energy

We have a range of alternative energy cylinders for use with renewable heat sources.

Thermal stores can be used to store heat from a variety of sources when available for use when required, including solar thermal and solid fuel boilers. They can be used to provide either domestic hot water only or wet central heating and domestic hot water.

Unvented cylinders provide mains pressure hot water, utilising either solar thermal, ground source or air source heat pumps.

THERMflow provides the flexibility of bespoke design and multiple energy inputs, working at the heart of your heating and hot water system.


It enables the ability to incorporate multiple energy sources to heat the home, as well as meet its hot water demand, to achieve improved efficiencies and cost savings.
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CUBEflow providing the space saving solution for space restricted installations, with the tank design taking up 27% less space than an equivalent cylinder.


The range of copper hot water tanks deliver mains pressure hot water, with both standard and bespoke models that can be heated electrically, or indirectly by a gas or oil boiler, or renewable heat sources.
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The POWERflow, copper unvented hot water cylinder with bespoke design flexibility and suitable for use with solar thermal input in addition to traditional heat sources.


It has revolutionised new build and refurbishment schemes, bringing greater flexibility, increased cost effectiveness and much improved performance.
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The ECOflow copper heat pump cylinder is designed to enhance the performance of Heat Pumps which are increasingly popular as people look to reduce their costs and emissions.


Copper hot water cylinders have been widely recognised as the best and most cost effective solution to use in conjunction with heat pump systems regardless of whether it is an Air or Ground source.
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STEELflow offers a range of high performance unvented cylinders for those on a budget, with models for use with solar thermal and heat pump technologies.


Manufactured from premium grade duplex stainless steel, STEELflow unvented cylinders are produced with McDonald Water Storage uncompromising efficiency and quality standards.
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  • A range of thermal stores specifically designed for use with solar thermal technology and uncontrolled heat sources such as solid fuel
  • Unvented cylinder ranges designed to incorporate solar thermal or heat pump technologies
  • All deliver mains pressure hot water
  • Thermal stores can provide wet central heating
  • Bespoke designed or slimline products available
  • Rectangular design thermal stores for space restricted applications

Our focus is very much on the manufacture of copper hot water cylinders and tanks. Copper provides fantastic benefits including;

  • Ability to kill 99% of bacteria including Ecoli and legionella
  • One of the most efficient conductors of heat
  • Significantly more flexible for manufacturing than other materials
  • Long lifespan due to its amazing resistance to corrosion
  • 100% recyclable


For further information see our brochure The Ultimate Supermetal or visit our Copper Facts page.


Alternative energy is energy that does not come from fossil fuels, and therefore produces little to no greenhouse gases like carbon dioxide (CO2). This means that energy produced from alternative sources does not contribute to the greenhouse effect that causes climate change.

These energy sources are referred to as “alternative” because they represent the alternative to coal, oil, and natural gas, which have been the most common sources of energy. These fossil fuels emit high levels of CO2 when burned to produce energy and electricity.

Alternative energy, however, should not be confused with renewable energy, although many renewable energy sources can also be considered alternative. Solar power, for example, is both renewable and alternative because it will always be abundant and it emits no greenhouse gases.

Renewable energy is generated from natural sources, such as the sun, wind, biomass and water, with renewable energy sources being naturally replenished.

It’s also often referred to as “green energy” and “clean energy” as the process of generating energy from these renewable sources emits no or little greenhouse gases – unlike fossil fuels like coal and oil. Moving away from these traditional sources of energy is a key step in our efforts to take action for climate and combat climate change.

There are a wide range of renewable heat sources suitable for use with hot water cylinders or thermal stores which include;

  • Solar PV (photovoltaic) panels provides electricity that can be used to power immersion heaters (via an inverter) within the cylinder or thermal store.
  • Solar thermal systems use solar panels fitted to a roof, mounted on a free-standing frame or even hung from a wall. The power they generate heats up water that is stored in a hot water cylinder.
  • An air source heat pump uses the heat from the outside air to provide you with heating and hot water – working in a similar way to a fridge but in reverse by extracting energy from the air and using it to warm your home. Heat pumps work in all temperatures and are capable of extracting heat from the air even at low temperatures.
  • Biomass systems burn organic materials, such as wood pellets, chips or logs to provide heating and hot water. This is a lower carbon way of heating compared to fossil fuels like coal and oil as the wood burned in these systems only emits as much carbon as the tree absorbed during the months and years that it was growing.

While domestic unvented cylinders can be manufactured from either copper or stainless steel, the bespoke design flexibility of copper provides the perfect solution where standard stainless steel products cannot fit. With a wide range of diameters available to choose from, and the ability to adjust the tapping positions to suit the installation, it has become the perfect choice for installers.

The POWERflow and ECOflow unvented ranges offer slimline models with as little as 400mm overall diameter, with the STEELflow starting at 475mm diameter.

The THERMflow also offers cylinder sizes from 400mm, with CUBEflow bespoke designed to suit the available space.

You should be aware that an unvented cylinder is a pressurised container and will require regular maintenance just like a gas boiler, to ensure the key safety devices fitted to the system operate correctly.

An annual check is vital to ensure your safety and must be carried out by a qualified engineer. It not only validates the manufacturer’s warranty but also guarantees the cylinder operates efficiently in compliance with industry guidance and Building Regulations.

When It is generally the homeowner or landlord who would identify when the cylinder is due a service, in the same way as a boiler. However it must be a G3 qualified engineer that carries out the necessary service and maintenance checks on the cylinder. Click here to see the full details of unvented cylinder service requirements.

All unvented cylinders are provided with a 25 year manufacturers warranty on the cylinder body against material defects and manufacturing faults, with 2 years on all components.

The main insulation method is high density injection foam, that is then cased to not only maintain the temperature of the store for the maximum period, but also provide an aesthetic finish that is easy to clean. We also offer spray foam insulation on our copper POWERflow and ECOflow where requested.

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