• Energy Research

Abstract Domestic hot water usage (DHW) accounts for a significant share of energy consumption in different types of buildings. Achieving a detailed characterization of domestic hot water usage profiles is of great relevance, as this information will allow for a more reliable assessment of the energy efficiency of systems and buildings. A deeper knowledge of the features of demand profiles will allow for the design of innovative control strategies based on consumption patterns. In this study, the authors review recent works on hot water consumption profiles in different types of buildings and then synthesize available information for the accurate estimation of the energy consumption resulting from DHW use. Water draw-off consumption patterns specified in national and international technical standards are reviewed and influential parameters on water consumption are identified, including climatic conditions, seasonality, building type and socio-economic factors. State-of-the-art modelling tools for generating DHW usage profiles are summarised and new research lines are then proposed, taking into account the caveats in the current characterization and modelling of DHW consumption in buildings.

This paper describes an analysis of a variable speed heat pump (VSHP), which responds to direct load control (DLC) signals to provide grid frequency regulation (GFR) ancillary service, while ensuring the comfort of building occupants. A data-driven dynamic model of the VSHP is developed through real-time experimental studies with a time horizon ranging from seconds to hours. The model is simple, yet still sufficiently comprehensive to analyze the operational characteristics of the VSHP. The DLC scheme is then experimentally applied to the VSHP to evaluate its demand response (DR) capability. Two control methods are considered for a practical implementation of the DLC-enabled VSHP and a further improvement of the DR capability, respectively. Additionally, a small-signal analysis is carried out using the aggregated dynamic response of a number of DLC-enabled VSHPs to analyze their contribution to GFR in an isolated power grid. For experimental case studies, a laboratory-scale microgrid is then implemented with generator and load emulators. We show that the DLC-enabled VSHP can effectively reduce grid frequency deviations and required reserve capacities of generators.

Abstract In this study, a procedure was applied for the performance of real-time emissions measurement at engine transient tests. The measurement of gaseous emissions from raw exhaust was done according to the standard ISO16183:2002 and the particulate mass emission was determined by an alternative method based on the measurement of smoke opacity and hydrocarbon emission during the transient test for further conversion to particulate mass. The method for calculating particle mass was validated by comparison with experimental data obtained by application of the standard gravimetric method. A measurement strategy, including engine preconditioning and control of ambient temperature, was applied to improve measurements. For the analysis of results, the time misalignment of the measurements was corrected by the calculation of the delay times produced as a result of the measurement systems configuration. The measurement procedure was applied to two cases of cycles UDC: with and without glow plug inside the cylinder of a light duty Diesel engine. The time evolution of each pollutant was analyzed to get understanding of which stages of the cycle produce more pollution and the comparison between both cycles was done by using the exhaust emissions integrated during the tests.

Abstract This paper presents a study on the characterization of the performance of a water-to-water heat pump of 40.5 kW fixed heating capacity under different cycling conditions scenarios. Semi-virtual laboratory experiments were conducted to analyse the influence of inertia from 1.23 to 24.7 L/kW on the efficiency of the heat pump operating at partial load. Different parameterizations in standards were compared to assess their ability to predict the energy efficiency degradation caused by cycling. Performance deterioration at part load was found to be highly dependent on inertia conditions, with non-negligible start-up parasitic effects detected for the heat pump under study, particularly for decreasing inertia. Results suggest that current standards for characterising the performance of systems at partial load, such as the European EN14825, should be reviewed to account for the influence of inertia on equipment performance and for the potential occurrence of start-up efficiency losses for water-to-water heat pumps. An expression is derived in this study for the start-up losses degradation coefficient C d and a single parameterization accounting for different sources of efficiency losses is proposed, together with a simple method to determine degradation coefficients from reduced experimentation.

Abstract This study uses a building energy performance simulation to investigate the impact of predicted climate warming and the additional issue of building ageing on the energy performance for a library in Turin, Italy. The climate and ageing factors were modelled individually and then integrated together for several decades. Results from the climate-only simulation showed a decrease in the building heating energy usage which outweighed the increase in the on-site cooling energy demand occurring in a warming scenario. The study revealed a high sensitivity of energy performance to building ageing, in particular due to HVAC (Heating, Ventilation and Air Conditioning) equipment efficiency degradation. Building ageing was seen to negatively affect the energy performance as it induced a further increase of the cooling energy usage in a warming climate, while it also counteracted the reduction of the heating energy usage resulting from warming. Simulations on the combination of mitigation techniques showed a number of potentially retrofit measures that would be beneficial for buildings to avoid an increase in the cooling energy usage due to climate warming. The combination of these retrofit techniques showed a potential decrease of 87.3% in the final cooling energy usage for the considered building.