Integrating space heating and cooling with the production of domestic hot water can be an intelligent approach to saving costs on the two largest energy requirements in your home. While the use of geoexchange is well understood by most for the space heating and cooling part, the production of domestic hot water is less well understood. Let’s explore how this is possible.
The two standard methods to heat domestic hot water in your home are:
- an instantaneous approach using gas or electricity as the heat source; or
- a storage-based approach using gas, electric element, solar hot water or air sourced heat pump as the heat source.
The selection between instantaneous or storage is typically based on the hot water requirements of your home. In apartments, it could simply be the area available for storage.
The selection between the various heat sources is similarly a function of the availability of gas infrastructure, the hot water requirements of your home, your climate, budget and the availability and expertise of local installers. For example, solar hot water heating utilises a storage-based approach to store the solar energy absorbed during the day for later use.
Geoexchange is another heat source for heating your domestic hot water. It is a storage based approach that can be either a direct or an indirect process as follows:
- Indirect: Use of a desuperheater to supplement a storage-based hot water system; or
- Direct: Use of a water to water Ground Source Heat Pump (GSHP) to directly heat a storage tank.
Indirect Hot Water with a Desuperheater
The indirect approach using a desuperheater has been the most common approach over the past few decades with geoexchange systems. The desuperheater is a small secondary heat exchanger that is an option on your ground source heat pump and is included on about 70-80 % of all units.
It transfers waste heat from the refrigeration cycle of the ground source heat pump into your hot water storage tank (Figure 1 and Figure 2). It is only able to do this while the system is operational which is why it is considered a supplementary system only and a ‘conventional’ storage-based hot water system is still required. It has the potential to save you up to 70 % on your hot water costs depending on usage or hot water, usage of the ground source heat pump and the combination of systems installed.
Figure 1: Water to air GSHP fitted with a desuperheater that transfers heat into a hot water storage tank. Note that the hot water storage tank could be primarily heated by electric element, solar, gas or air source heat pump.
Direct Hot Water with a Ground Source Heat Pump
The direct approach uses a small capacity (typically 4 – 6 kW) water to water ground source heat pump to heat a hot water storage tank (Figure 3). It could be either dedicated to hot water or be able to prioritise hot water while also providing hydronic heating (ie underfloor / radiator heating or pool heating).
Figure 3: Water to water GSHP providing dedicated domestic hot water.
A dedicated hot water system using geoexchange could have its own ground heat exchanger or it could be connected to a common ground heat exchanger with other ground source heat pumps that are providing heating and cooling through the home (Figure 4).
Figure 4: Water to air GSHP providing ducted heating and cooling and water to water GSHP providing dedicated domestic hot water. Note that they are connected to the same Ground Heat Exchanger which can provide system efficiencies in both installation and operation.
There are many options for heating domestic hot water using your geoexchange system. The best system for your home is determined by our design engineers during our residential design process.
Just like your home heating and cooling, a geoexchange hot water heating system is not affected by cold ambient temperatures or the lack of sunshine through a rainy winter. This means consistently high efficiencies all year round.
To find out more about how we can save you money on your hot water heating as well as your home heating and cooling contact us.