Energy storage as the key to modern heating concepts

The discussion about renewable energies is no longer just about the generation of electricity or heat. At least as important is the question of how this energy can be stored sensibly and made available for use at a later date.

Particularly in the interaction between photovoltaics, solar thermal energy and heating systems, storage technology determines whether efficiency gains actually translate into everyday life. Buffer storage tanks are thus increasingly becoming the focus of modern energy concepts for residential and commercial buildings. While photovoltaic systems supply electricity and solar thermal systems generate heat, the real challenge lies in decoupling generation and use in terms of time. The sun is not always available when hot water or heating is needed. This is exactly where large-volume storage solutions come in, which can absorb surplus energy and release it again as needed.

Citrin Solar and its focus on storage technology

The company Citrin Solar, based in Moosburg near Munich, specialises in precisely this area. The manufacturer develops and produces solar thermal collectors and buffer storage tanks for heating and drinking water systems. The range extends from compact solutions for single-family homes to very large-volume storage tanks for complex systems. What is striking is the clear focus on thermal storage as the central interface between different energy sources. The focus of the trade fair presentation is a new buffer storage tank, which is being introduced under the name EOS Speicher. Technically, it is a stratified storage tank that is specifically combined with a special device. This design is intended to convert excess electricity from photovoltaic systems directly into usable heat and store it in the storage tank. The approach differs significantly from classic hot water storage tanks, where uncontrolled mixing often leads to efficiency losses.

Converting PV surplus into heat in a sensible way

The core principle of the system lies in controlled temperature stratification. Cold water is heated in the lower part of the storage tank until a defined temperature is reached. Only then is the heated water transferred to the upper part of the buffer storage tank. This means that hot water at a high temperature is immediately available for use, instead of keeping large quantities of water at a lukewarm temperature. Compared to pure battery storage, this offers a decisive advantage: the amount of energy that can be stored in hot water is very high and can be reused with little loss. Hot water and heating are among the largest energy consumers in buildings. In this way, surplus PV electricity can be used directly in the areas where it is actually needed. Typical application scenarios for this form of energy storage include:

• Use of photovoltaic surpluses for hot water production
• Support of heating systems through thermal storage
• Reduction of electricity feed-in in favour of self-consumption
• Combination with existing heating and solar systems

Solar thermal energy as a supplement to photovoltaics

Another focus is on the in-house production of solar thermal collectors. These are produced at the factory in Moosburg and are available in various sizes. The operating principle is classic but proven: a frost-proof solar fluid circulates through the collector, is heated by solar radiation and transports the energy to the buffer storage tank in the building. There, the heat is used either for hot water production or to support heating systems. The difference to photovoltaics is fundamental, but particularly interesting in terms of their interaction. While photovoltaic systems generate electricity, solar thermal systems supply heat directly. Both systems serve different energy flows, but can be linked together via a central storage tank. This creates an integrated overall system that provides electricity and heat as needed.

Vertical integration and system approach

Citrin Solar pursues a clear system approach. In addition to manufacturing solar thermal collectors and storage tanks, the company also offers the installation of complete photovoltaic systems – from the basement to the roof. Although the PV modules themselves come from external manufacturers, they are integrated into the overall system from a single source. The aim is to achieve coordinated interaction between all components, with storage technology playing a central role. Another noteworthy feature is the high proportion of manufacturing carried out in-house. The solar thermal collectors are not purchased from third parties, but are produced entirely in-house. This enables close control over quality, materials and technical development. In the field of storage technology in particular, it is clear that small design details can have a major impact on efficiency and everyday usability.

Thermal storage as an underestimated component

In the public debate on energy transition and building technology, heat pumps and photovoltaic modules are often at the forefront. Storage solutions, on the other hand, are often considered a secondary aspect. In fact, however, they are a decisive factor in the economic efficiency and practicality of modern systems. Without sufficiently dimensioned and intelligently designed storage systems, much of the potential of renewable energy is wasted. The approach of converting surplus electricity into heat and storing it in buffer storage tanks opens up new possibilities. Especially in times of high PV yields in summer, energy can be used for hot water or even for later heating support. Thermal storage systems thus take on a similar role to batteries, but with significantly lower costs per kilowatt hour stored. Against this backdrop, it becomes clear why manufacturers such as Citrin Solar are not focusing solely on collectors or modules, but on the interaction of all components. Storage technology is becoming the linchpin of modern heating and energy systems – and determines how much of the energy generated actually reaches the building.