Earth-to-air heat exchangers: applicability, design conditions and technical-economical convenience

The EPBD, together with other acts and funding programs, strongly promotes the passive strategies in order to achieve, above all in summer, indoor comfort conditions, reducing or avoiding the active air-conditioning. The adoption and the design of these strategies are not indifferent to the specific boundary conditions. In this paper, the performances achievable adopting an earth-to-air heat exchanger for an air-conditioned building are evaluated for winter and summer. The analysis has been carried out on varying the main boundary conditions related to the environmental context, the soil, the tube properties and connected behaviours of the airflow crossing it. Several control strategies have been simulated too, in order to propose the most suitable design criteria for each climate. The fan electrical energy represents a design critical aspect, requiring an accurate evaluation, in order to achieve the maximum thermal exchange and limiting the pressure drops inside the buried pipes. Otherwise, the use of an EAHX can be also penalizing.