Development of a Pilot Borehole Storage System of Solar Thermal Energy: Modeling, Design, and Installation

Abstract

Borehole thermal energy storage systems represent a potential solution to increase the energy efficiency of renewable energy plants, but they generally have to comply with strict regulatory frameworks, mainly due to the deliberate modification of the subsoil’s natural state. This paper presents the design, testing, and monitoring phases carried out to set up a borehole thermal energy storage (BTES) system able to exploit the excess solar heat from photovoltaic thermal (PVT) collectors. The case study is the refurbishment of a pig nursery barn, hosting up to 2500 weaners, in Northern Italy. This study aims to define a BTES suitable to develop a heating system based on renewable energy, ensuring environmental protection and long-term sustainability. The retrofitting intervention includes the installation of a dual-source heat pump (DSHP), in order to recover the solar heat stored in summer during winter. Specific constraints by the Environmental Authority were as follows: maximum storage temperature of 35 °C, authorization to intercept the shallowest aquifer at a maximum depth of 30 m, obligation of BHE grouting, and the definition of a strategy for continuous measuring and monitoring of the groundwater’s thermophysical properties. The results were used as inputs to optimize the design and installation of the integrated system with PVT, BTES, and DSHP.

Thermal, Electrical, and Economic Performance of a Hybrid Solar-Wind-Geothermal System: Case Study of a Detached House in Hamburg and Sylt, Germany

“…Because of seasonal and daily fluctuations of solar and wind energy, for small-to large-scale applications, electricity generated by solar radiation or wind power is often combined with a battery bank or converted to other forms of energy for storage (e.g., hot water, compressed air [13][14][15]). Specifically, hot water is stored in the form of borehole or aquifer thermal energy storage (BTES [16][17][18] or ATES [19,20]). The main principle is that the excess solar or wind energy generated during the high production time is stored underground in the form of heat, which is then extracted for further use during the low production time.…”