Feasibility Assessment of a Hybrid System Combining the Wind Power and High-temperature Aquifer Thermal Storage for Regional Heating

Wind curtailment is a particularly acute challenge to wind energy integration in China. Since wind energy is intermittent and unpredictable, and its generation may not coincide in time with usage demands, its large-scale inclusion will introduce adjustment difficulties to power grids or regional heating network and large-scale wind curtailment problems can also occur. The addition of energy storage to wind energy generation can be a key solution to this problem.

High temperature aquifer thermal energy storage (HT-ATES) is a cost-effective and suitable technology to store large amounts of energy, and has been increasingly used for heating of buildings. It has been demonstrated as an efficient and stable tool to buffer the seasonal imbalance and significantly contribute to reduce greenhouse gas emissions.

Here we proposed a novel coupling strategy to combine wind power with HT-ATES for regional heating. The excess wind energy is firstly transformed for boiling water, which is then injected into the medium-deep aquifer for storage. In Winter time, the stored water is thereby extracted for heating. Based upon this hybrid system, the objective of smooth heat delivery can be achieved, and the problem of the instability in wind energy generation is solved while waste is prevented.

To achieve a comprehensive analysis of the feasibility of the hybrid system and the estimation of its thermal performance, a surface-to-subsurface model is established via the integration between TRNSYS and OpenGeoSys(OGS) platform. TRNSYS is applied to simulate the conversion from wind energy to thermal energy, while OGS focuses on the modeling of hydro-thermal coupled transport in the subsurface. The coupling is achieved via the input/output data exchange. The integrated model provides new insight into the thermal recovery efficiency of the whole system and allows us to decipher the relative importance of the controlling parameters.

The results obtained from the model show that the 600 kW wind turbine and HT- ATES hybrid system can provide around 4 GWh of the energy capacity after the 10^th cycle, and the thermal recovery factor can be achieved up to 80%, which indicates a techno-economical promising perspective for the wide replication of the hybrid system.