Heat pump thermal battery

Hydrosol image of Stiebel Eltron buffer tanks, larger tanks can be used as a thermal battery.
Heat Pump Hydronic Buffer Tanks, 100 up to 1500 litres

Consider adding a larger heat pump thermal battery (buffer tank) to your heat pump hydronic heating and cooling system. 

This will increase the internal mass of your home for greater thermal storage.

Therefore, your home will benefit in these ways:

  • Moderates the extremes of your indoor temperature range
  • Stabilizes your indoor temperature
  • Balances the temperature better throughout your home
  • Reduces your energy consumption due to the passive warming and cooling effect
  • Maximizes your solar power during the day
  • Particularly beneficial in a southern or inland Australian climate

High Diurnal Variation

High diurnal variation is typical of southern and inland Australia. This is where there are large swings between the day and night time temperatures in winter.

Solid Construction

Ideally, homes in such climates should be built of solid construction with high thermal mass inside the building fabric. The key building element is an insulated concrete slab.

Other dense building elements include internal brick, stone walls and feature walls.

Lightweight Construction

If your home is made of lightweight construction, such as timber framed weatherboard on suspended floor, then consider adding thermal mass in the form of stored water.

If you are considering installing a heat pump hydronic system, you have the opportunity to add a large buffer tank to increase your thermal mass. This is a heat pump thermal battery.

Water is a very good store of thermal energy so increasing the size of the buffer tank is a good way to add thermal mass.

Your heat pump hydronic system needs a buffer tank to operate efficiently and effectively. However, you can increase your buffer tank size to 200, 400, 700 or even up to 1500 litres to create a very large thermal battery.

Heat Pump Cooling

A heat pump has the added benefit over a gas boiler in that it can reverse cycle and provide cooling in summer. It can also be powered by your solar panels during the day.

In summer, your heat pump thermal battery works to keep your home cooler. Switch to cooling mode and your heat pump will operate in reverse, removing heat from inside and transferring it outside.

Heat pump cooling operates in two ways:

  1. Chilled water through fan coil convectors
  2. Cool water through underfloor hydronic systems 

Solar Power

If you are installing solar panels, then adding thermal mass is a more important consideration.

This is because your daytime solar power can be stored in the thermal battery of your buffer tank and building mass that will release it at night.

Heat Pumps

A heat pump will typically produce about 4 times the heat output compared to the power consumed using underfloor hydronic systems at lower temperatures. 

Using radiators, heat pumps will produce about 3.6 – 3.8 times the heat output from the power they consume due to the higher temperatures required.