A full-scale thermo-hydraulic simulator for the characterization of building heat cost allocation methods

Abstract

Abstract. An innovative heat accounting method for apartment buildings, named EcoThermo, based on the estimation of water flow rates at each radiator by thermo-hydraulic modelling of the hot water distribution system, has been developed in the framework of the EU Programme FP7-SME-2012. In order to validate this approach and to compare it with conventional Heat Cost Allocators (HCA), a full-scale thermo-hydraulic simulator has been recently built at INRIM. This INRIM test facility represents a real-scale hot water heating system consisting of a gas-fired boiler and 40 radiators of different characteristics, mimicking a four-story residential building. Each radiator is equipped with an electromagnetic flow meter and a pair of short-stem Pt100 PRTs immersed in the water flow for inlet and outlet water temperature measurement, such that the radiator thermal output can be determined by direct metering, providing an accurate reference value against which indirect allocation methods can be compared and assessed. The paper describes in detail the INRIM thermohydraulic simulator, highlighting its design features and metrological capabilities and discussing key results of the investigations carried out so far on different heat accounting approaches. The accuracy of the EcoThermo model has also been assessed against direct heat metering and HCA approach.

A comprehensive review on heat accounting and cost allocation in residential buildings in EU

“…Optimum installation position of HCAs at a radiator height of about 60% has been demonstrated Bozzini et al [121] Test on HCAs in a "vertical" hot water distribution network of 10 radiators of different types, materials and installation conditions Authors found relative deviations with respect to the reference share of radiator heat consumption, up to 30% When heat consumptions are shared, compensation of systematic errors occur as far as the radiators within the same building are similar for type, material, shape, dimensions, installation, operative conditions Saba et al [27] Metrological reliability of HCAs and ITCs Uncertainty of heat sharing of about 11% at critical conditions could decrease to about 3% in optimal ones Dell'Isola et al [28] On field experimental comparison of direct and indirect heat accounting systems (HCAs and ITCs) HCA accuracy is comparable with the one of DHMs (share error in the whole heating season of about 3.0% for HCAs vs 1% for DHMs), Share error in the whole heating season of about 7.1% for ITC-DDC and of about 8.2% for ITC-TC, error becomes unacceptable (up to 12.4%) for heating plants handled differently or in case of very low energy consumption.…”

“…The alternative use of DHMs and IHASs implies some consequences in terms of consumer protection. Accuracy of IHASs could range from 3.0% to 12.4% [26] and up to 30% [27] while in different operating conditions it ranges from about 2.7 % to about 11.7 % [28]. Moreover, only DHMs are currently regulated by legal metrology [29], therefore they can be used both for measuring thermal energy at the point of supply and also for sub-metering of energy consumption within the building.…”