Study of an underground cistern as a thermal storage with HVACR system via heat pump assisted by PV: the case of the IWER building in Pamplona

Resumen

Given the global uncertainty surrounding energy prices and the urgent need to improve energy efficiency in the building sector, sustainable rehabilitation is becoming increasingly important. This is particularly true in the case of Spain, where the building sector is largely outdated. In response to this challenge, the OpenLab European project aims to refurbish the IWER building, a tertiary building located in Pamplona. The proposed HVACR system will be based on heat pumps supported by a large photovoltaic installation and contemplates a singular feature: an existing underground water cistern that can be used as a thermal storage. The use of such storage system can help compensate the inherent lack of flexibility in the energy consumption patterns of buildings in the tertiary sector. The study involves a real-case simulation of a sustainable rehabilitation project, which expands previous general-case studies of solar assisted heat pumps with thermal storage for smaller, primarily residential buildings. To achieve that objective, simulations are performed by the Design Builder software using hourly data analysis. Different sizing and control strategies will be applied to meet the specific needs of the involved tertiary building. The results of the study show three main benefits: a reduction of the total HVACR installed power by using the thermal storage for peak shaving; an improved control of the HVACR production by decoupling production and demand while stabilizing the regime of the heat pumps, and, finally, a maximized photovoltaic self-consumption coupled with a shift of the electricity load to cheaper and more sustainable electricity consumption hours.