Thermal heat store cylinders
A thermal store is a cylinder, tank, or vessel used to manage and store heat until it is required. The stored water is not directly fed to the hot water taps or a shower from the thermal store, which is how it differs from a typical hot water cylinder. Instead, heat is transferred from the thermal store water to the domestic water as it passes through a stainless steel pipe heat exchanger coil within the vessel . Thus, a thermal store cylinder has the capacity to rapidly transfer a large amount of heat, enabling homeowners to quickly fill a bath or take a mains-pressure shower.
Thermal store cylinders are the ideal or perfect solution to combine various multiple heat sources, such as gas or oil boilers, solid fuel, biomass, heat pumps, or solar thermal, to deliver domestic hot water and central heating water to provide space heating using suitable radiators or an underfloor central heating system, and maximise energy efficiency.
How does a thermal store work ?
The thermal energy is kept in a hot water cylinder. Instead of potable hot water (tap water), which is what you would find in a traditional hot water cylinder, the tank is filled with central heating hot water. As such, a thermal store cylinder works in the opposite manner from standard hot water cylinders.
Cold water flows through a coil, which is made of duplex stainless steel construction, inside the thermal store cylinder, which is surrounded by hot central heating water, indirectly warming the water to produce hot tap water. The thermal stores hot water is then cooled to a safe temperature through blending down, normally to 38C to 40C temperature from the coil with a thermostatic mixing valve.
The result is mains pressure hot water without the requirements of unvented cylinders that require qualified personnel to fit, certify to the building regulations, and maintain. Thermal stores don’t require this, as they heat hot water on demand.
Thermal stores can be powered by an oil boiler, a solid fuel or wood burning stove, in some instances, the heat source is a conventional boiler, normally gas or oil boilers. However, more recently, renewable heat sources have become an increasingly popular way of heating these hot water cylinders, such as solar energy as the heat source, or a biomass boiler installation, which uses the thermal store for two reasons:
Biomass boilers, wood-fuelled
1. As a buffer tank for the heating circuit, as when you use a thermal store, you will be storing energy for periods when you require central heating, ensuring that you have heating even if the biomass boiler system goes out or stops operating. The thermal store works by managing and storing heat until it is required, with high insulation materials to retain the heat generated.
2. This point is particularly prevalent in relation to biomass boilers that use logs for fuel. As they are designed and manufactured to burn batch quantities of logs, when used in this manner, these boilers operate at a high efficiency level, rather than burning small quantities sporadically throughout the day, which reduces the heat energy efficiency dramatically. So by using a thermal store cylinder, you maximise the system efficiency for both the heating circuit and the domestic hot water for your property and benefit from mains pressure hot water.
Solar energy sources
Solar thermal or solar voltaic (heating the thermal stores via electric immersion heater or heaters) are also ideal for heating thermal store cylinders by keeping the water heated by a solar thermal heating system in reserve for use later, when there is little or no solar energy available.
For use during the winter, it is advised to incorporate an electric immersion heater so the water can be heated directly. This can be powered by mains electricity at a reduced rate. A property with a wind turbine, hydroelectric, or solar PV systems get the benefit of “free” energy, as well as them being green energy sources install.
Thermal store sizing
Sizing a thermal store, depends on three elements – The kW power being absorbed by the heated water ,the temperature of this water and the flow rate of the heating system, this directly relates to the volume of DHW produced – with the following chart showing the volume of DHW water with a temperature rise of 35C.
Combining fuel sources ensures a thermal store cylinder full potential.
Thermal stores reach their full potential when they employ a variety of heat inputs, with either a single coil, a twin coil , or direct heating.
The thermal store can use a high-efficiency solar energy input during the day to heat the water inside the store.
It is also possible to connect a wood burner, which is generally lit in the evening, to the system, raising the temperature of the water heated by solar during the day in the thermal store.
A traditional gas boiler or an immersion heater can support all of this.
Additionally, for even greater energy efficiency, a low carbon or renewable electricity source could be connected to the immersion element to supply direct heat input to the thermal store cylinder, reducing the need for the fossil fuel boiler and resulting in lower operating costs for the property.
Thermal store hot water cylinders
For the best thermal store cylinders on the UK market, please don’t hesitate to contact our technical sales team on 01202 822221 or click here for our email contact form.