Focus on heat boosters for the heat pump and efficient home stations
KfW-55: Efficient water heating with eXergiemaschine and heat pump
- Commissioning: 2021
- System version: eXergiemaschine
- KFW 55 residential building
- Special feature: Heat booster for heat pump; home stations
In the new KFW 55 house with twelve residential units, an air heat pump is installed for heating, which also supplies heat for hygienic hot water preparation at a high temperature level with the help of the downstream eXergiemaschine. The eXergiemaschine takes thermal energy from the low-temperature cylinder, which is charged by the heat pump and serves the heating circuits, raises the temperature and feeds the heat at approx. 60 °C into a high-temperature cylinder.
Home stations are installed directly at the apartments: they draw the heat for hot water preparation from a heating water circuit. This is supplied by the high-temperature cylinder, but does not come into contact with the drinking water: inside the home stations are heat exchangers that work as instantaneous water heaters and ensure a strict separation between heating water and drinking water. As soon as hot water is tapped in the home, the heat exchangers heat fresh, cool drinking water to around 55 °C and make it available quickly.
Further references
Frequently asked, simply explained
From a physical point of view, energy is always conserved. However, it consists of usable parts, the exergy, and not directly usable parts, the so-called anergy.
Energy = exergy + anergy
In technical thermodynamics, exergy refers to the part of the energy that can perform work. In heating technology, exergy is the part that leads to heat flows due to the higher temperature level and thus makes space heating and domestic hot water heating possible in the first place.
Exergy, the proportion of energy that determines whether heat is usable, must be given greater focus. After all, exergy optimization is the key to system efficiency.
If the different temperature ranges of a well-stratified water storage tank are completely mixed, the water ends up with a uniform average temperature.
The energy content of the storage tank remains unchanged. During this process, the hot water transfers its heat to the colder water. This means that the exergy that existed at the higher temperature level compared to the average temperature and was required, for example, for
which would be necessary to heat drinking water, has disappeared, irretrievably, irreversibly. Exergy has become anergy. Anergy is energy that can no longer be used (without a new supply of energy). Only by using auxiliary means (e.g. electricity) can it be used again.
exergy arise.
In contrast to energy, exergy can therefore be reduced or even completely destroyed.
The varmeco fresh water technology uses instantaneous water heaters to heat domestic hot water only when required, eliminating the need to store it in a domestic hot water tank and inhibiting the growth of germs (e.g. legionella). The integrated VarCon211 controller only activates the charging pump when drinking water is required, which saves energy and ensures hygiene at the same time.
Thanks to the separation of heating and domestic hot water and adaptive control, the system adapts optimally to daily requirements. The circulation pump control keeps the domestic hot water at the right temperature and prevents the proliferation of legionella bacteria, ensuring a high level of hot water comfort and safety.
The eXergiemaschine recycles waste heat that escapes unused in many businesses and turns it into usable heat. It raises the temperature of the waste heat to a usable level and simultaneously cools the lower part of the heat storage tank, which improves the efficiency of the heat sources. This efficient use saves energy and is easy on both the wallet and the environment.
The eXergiemaschine is a special heat pump that enables high source temperatures and a wide temperature spread. This makes it an ideal partner for renewable energy systems, such as solar thermal and hybrid modules, which work more efficiently and supply more energy.
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