1. Purpose and Design
The primary objective of this study was to supply a complete heating solution to a residential building. To achieve this, the researchers designed an integrated system that effectively harnessed solar energy and stored it in boreholes for later use.
Solar Energy Harvesting
- Solar-Thermal Collector: The heart of the system was a solar-thermal collector. This device captured sunlight and converted it into heat energy.
- Energy Collection: The collector absorbed solar radiation, raising the temperature of a heat transfer fluid (usually water or a glycol-water mixture).
- Efficiency: The efficiency of the collector was critical for maximizing energy capture. Factors like orientation, tilt angle, and surface material influenced its performance.
Borehole Thermal Energy Storage (BTES)
- Boreholes: Vertical boreholes were drilled into the ground, typically reaching depths of several hundred meters. These boreholes acted as thermal reservoirs.
- Heat Exchange: During sunny periods, excess solar energy was used to heat the fluid circulating through the boreholes.
- Thermal Mass: The surrounding earth served as a massive thermal storage medium, allowing the system to store energy efficiently.
- Heat Transfer Fluid: The same fluid used in the solar collector circulated through the boreholes, transferring heat to or from the ground.
2. Numerical Simulation and Performance
- Dynamic Simulation: Researchers performed a time-dependent dynamic simulation over a year. They considered hourly weather data, seasonal variations, and a 10-minute time step.
- Energy Mismatch Solution: The solar-BTES system addressed the mismatch between energy demand and supply. During sunny days, excess energy was stored in the boreholes. When demand exceeded solar availability (e.g., at night or during cloudy days), the stored energy was retrieved.
- Expandability: The heat capacity of the system could be expanded by drilling additional boreholes and connecting them to the existing network.
- Efficiency: Larger BTES systems were found to be more efficient, with a high recovery rate of up to 83%.
Conclusion
The integration of solar energy and borehole storage holds immense promise for sustainable heating solutions. As technology advances and awareness grows, we can expect more innovative applications like the solar-BTES system to revolutionize energy use in buildings.
