System 3 - Shallow green heat
The solar thermal energy produced by the photothermal and photovoltaic panels will be stored from spring to autumn in an underground high-temperature storage via hot water heat exchanger, powered exclusively by the photovoltaic panels. A series of boreholes at a depth of about 400 m will gradually raise the temperature of the rock to 70 °C and will constitute the most powerful underground thermal storage of the SYNERGYS project. The heat stored here will be transferred to the low-temperature heat network. This will mimic the operation of a modern district heating network supplying energy-efficient buildings. The heat from here will be transformed to a higher temperature using a high-temperature pump and then used in the district heating system of Litoměřice.
- Photovoltaic panel PV
- Photothermal collector PT
- Air source heat pump ASHP
- High-temperature heat pump - water/water TP
- Field of shallow wells to a depth of 400-500 m WELL 400
- District heating system DHS
- Low-temperature network emulator EM
Photovoltaic panel PV converts sunlight into electricity. Its basic functional element is a photovoltaic cell. The current is proportional to the area of the cell, its efficiency and the intensity of the sun's radiation. For a particular cell, it depends in part on the spectrum of the incident sunlight, which varies throughout the day and year. A photovoltaic panel is usually composed of a number of cells connected in series. Photovoltaic panels commonly available on the market can be divided into crystalline and thin-film.
Photothermal collector PT converts solar radiation into heat energy. The solar radiation falls on the collector´s absorber, which is conductively connected to the collector's pipework. The energy transfer is provided by a heat transfer fluid that flows between the collector and a heat exchanger located in the heat appliance. Photothermal solar collectors are most commonly used for hot water or heating.
Air source heat pump ASHP removes heat from the ambient air and converts it to a higher temperature for heating and hot water. By regulating the compressor's power input, the electrical power of the PV system can be used to drive the compressor and thus produce completely renewable heat.
High-temperature heat pump - water/water TP heats water from the low-temperature heat network to a temperature level usable in the district heating system of Litoměřice.
A field of shallow wells to a depth of 400-500 m WELL 400 will serve as a high-temperature system for interseasonal heat storage. The wells in this field are planned in close proximity to each other so that the rock mass is heated to the operating temperature (up to 70°C) in the shape of a cylinder with a diameter of several tens of meters. The optimal distance of the wells is the subject of numerical simulations and depends mainly on the thermal conductivity and porosity of the rocks and changes in these properties with depth. At this depth, we expect mainly impermeable primordial continental sedimentary rocks - claystone, sandstone and conglomerate.
District heating system DHS supplies heat to buildings in the city of Litoměřice. Its operator is the company ENERGIE Holding a. s. Currently it burns wood chips and coal. From 2027 it should use geothermal energy thanks to the SYNERGYS project.
Low-temperature network emulator EM simulates conditions in modern heat networks. At the same time, it interconnects systems with seasonal storage to supply low-temperature heat to the district heating network via a high-temperature heat pump.
