Geocooling potential of borehole heat exchangers' systems applied to low energy office buildings

Abstract

The potentiality of geocooling (i.e. free cooling) with borehole heat exchangers is analysed for low energy\ud office buildings. The borehole heat exchanger field is coupled to a heat pump in winter and to the cold\ud distribution system in summer through a flat plate heat exchanger. The cooling requirement satisfied by\ud a direct heat transfer into the ground through the borehole heat exchangers is so-called geocooling.\ud A dynamic system model has been developed to simulate the building, the emission of thermal energy\ud through thermally activated building systems, the technical installation including the borehole heat\ud exchanger field and the interconnected thermal interactions. Thermal comfort requirements determine\ud the building energy needs and the size of the ground coupled system. A methodology is presented for\ud best system design.\ud Building design, system technical feasibility and limits of the ground coupled system are discussed and\ud result from the analysis of the numerous system simulations. Geocooling potential depends on the\ud quality of the building design and its heat emission. The importance of the ground thermal conductivity\ud and the ground recharge ratio on the system design are highlighted. Simple design sizing keys are\ud proposed for a fast pre-sizing of a borehole field

A Methodology for Defining Electricity Demand in Energy Simulations Referred to the Italian Context

“…For these reasons, other suitable sources were considered. Among these, the Swiss Technical Worksheet SIA 2024 [33] was successfully adopted in previous works of the authors (i.e., Pahud et al in [34]). It constitutes the main Swiss official reference for building system sizing (heating, ventilation, air conditioning, lighting, etc.)…”

Experimental testing of cooling internal loads with a radiant wall

“…However, regarding primary energy intensity VAV used 20 % more energy, as TABS provided cooling without any vapour compression cycle, just using a ground heat exchanger. A method for pre-sizing boreholes to apply geo-cooling was defined for office buildings [10]. The method highlighted the requirement of low energy buildings, using a building with TABS as case study.…”

Geocooling with integrated PCM thermal energy storage in a commercial building

“…Annual system seasonal performance factors (SPFs) of up to 20 have been observed in case studies [10]. This technology has been shown to be feasible for cool climatic regions [11], as well as for buildings in Switzerland [7] and Germany [6]. An investigation of heat transfer in a ground heat exchanger for different climates indicates that geocooling might be feasible in warmer Mediterranean climates [6].…”

“…Pahud et al [7] investigated the use of geocooling for a low-energy office building in Switzerland. Cooling was supplied via massive concrete slabs between floors which had plastic pipes embedded in them, through which water flowed from the ground heat exchanger.…”

“…This temperature difference can be exploited using a borehole heat exchanger and a heat transfer fluid (HTF) to provide cooling to building HVAC systems. This 'free' cooling can be used to offset the electricity consumption of air conditioners and reduce overall building energy consumption [7].…”