Towards Fossil Free Cities—A Supermarket, Greenhouse & Dwelling Integrated Energy System as an Alternative to District Heating

Abstract

The municipality of Amsterdam has set stringent carbon emission reduction targets: 55% by 2030 and 95% by 2050 for the entire metropolitan area. One of the key strategies to achieve these goals entails a disconnection of all households from the natural gas supply by 2040 and connecting them to the existing city-wide heat grid. This paper aims to demonstrate the value of considering local energy potentials at the city block level by exploring the potential of a rooftop greenhouse solar collector as a renewable alternative to centralized district heating. An existing supermarket and an ATES component complete this local energy synergy. The thermal energy balance of the three urban functions were determined and integrated into hourly energy profiles to locate and quantify the simultaneous and mismatched discrepancies between energy excess and demand. The excess thermal energy extracted from one 850 m2 greenhouse can sustain up to 47 dwellings, provided it is kept under specific interior climate set points. Carbon accounting was applied to evaluate the system performance of the business-as-usual situation, the district heating option and the local system. The avoided emissions due to the substitution of natural gas by solar thermal energy do not outweigh the additional emissions consequential to the fossil-based electricity consumption of the greenhouse’s crop growing lights, but when the daily photoperiod is reduced from 16 h to 12 h, the system performs equally to the business-as-usual situation. Deactivating growth lighting completely does make this local energy solution carbon competitive with district heating. This study points out that rooftop greenhouses applied as solar collectors can be a suitable alternative energy solution to conventional district heating, but the absence of growing lights will lead to diminished agricultural yields.