eXergiemaschine optimizes use of solar heating - Hotel Drei Quellen Therme
Optimal use of solar energy: eXergiemaschine as a temperature boost in hotel operation
Since summer 2025, the „Hotel Drei Quellen Therme“ has primarily been using solar energy: 170 PVT modules supply electricity and heat, making the use of fossil fuels less necessary. To ensure that the solar heat can be used optimally, a eXergiemaschine temperature to around 65 °C and cools the hybrid modules at the same time. This increases both the heat yield and PV electricity production.
- LocationHotel Drei Quellen Therme in Bad Griesbach im Rottal (Therme district)
- ObjectHotel with around 100 rooms, its own restaurant and wellness area
- The challengeFossil fuels are to be replaced by renewable energy.
- SolutionThe hotel installed PVT collectors that supply PV electricity and solar heat. A system of low and high temperature storage tanks and a eXergiemaschine ensure an increase in heat yield and PV electricity production
- Functionality of the eXergiemaschine in the project: The low-temperature heat drawn from the PVT modules is used by the eXergiemaschine is raised to approx. 65 °C and a system of three 1000-liter cylinders is charged. Hot water heaters or heating circuits can be operated from here. At the same time, the eXergiemaschine effectively cools the return flow to the PVT modules. This increases the heat yield and power generation efficiency.
- ResultThe hotel's own natural gas-fired combined heat and power plant and the peak-load oil boiler will have to run less often in future and the hotel management expects electricity and gas costs to be halved.
Find out more about this project and how the eXergiemaschine works in our detailed reference article: Hotel Drei Quellen Therme optimizes use of solar heating with the eXergiemaschine
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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