3 Search Results

This paper analytically investigates and compares the performance of a proposed ‘all-natural’ NH₃/CO₂ cascaded booster system to a conventional R404A direct expansion system as well as to an ‘all-CO₂’ system with multi-ejector unit and flooded evaporator. Performance comparison is made based on the annual combined COP and Life Cycle Climate Performance (LCCP) for operation in selected cities of Middle East and India. Our results show that in extreme warm climate, the energy efficiency of the proposed configuration exceeds that of all-CO₂ configuration by a maximum of about 12.23% and the total emissions are lower by up to 11.20%. However, themore » all-CO₂ multi ejector system performs better in cold and mild warm climate. In the NH₃/CO₂ cascade, the high temperature NH₃ system can be designed to be isolated from the accessible locations of the supermarket. Here, the work presented is expected to help adoption of natural refrigerants such as CO₂ and NH₃ for commercial application in extreme warm climate conditions prevailing in many cities of Middle East and India.« less

The WAter Cycle Multi-mission Observation Strategy – EvapoTranspiration (WACMOS-ET) project has compiled a forcing data set covering the period 2005–2007 that aims to maximize the exploitation of European Earth Observations data sets for evapotranspiration (ET) estimation. The data set was used to run four established ET algorithms: the Priestley–Taylor Jet Propulsion Laboratory model (PT-JPL), the Penman–Monteith algorithm from the MODerate resolution Imaging Spectroradiometer (MODIS) evaporation product (PM-MOD), the Surface Energy Balance System (SEBS) and the Global Land Evaporation Amsterdam Model (GLEAM). In addition, in situ meteorological data from 24 FLUXNET towers were used to force the models, with results from both forcing sets compared tomore » tower-based flux observations. Model performance was assessed on several timescales using both sub-daily and daily forcings. The PT-JPL model and GLEAM provide the best performance for both satellite- and tower-based forcing as well as for the considered temporal resolutions. Simulations using the PM-MOD were mostly underestimated, while the SEBS performance was characterized by a systematic overestimation. In general, all four algorithms produce the best results in wet and moderately wet climate regimes. In dry regimes, the correlation and the absolute agreement with the reference tower ET observations were consistently lower. While ET derived with in situ forcing data agrees best with the tower measurements (R² = 0.67), the agreement of the satellite-based ET estimates is only marginally lower (R² = 0.58). Results also show similar model performance at daily and sub-daily (3-hourly) resolutions. Overall, our validation experiments against in situ measurements indicate that there is no single best-performing algorithm across all biome and forcing types. In conclusion, an extension of the evaluation to a larger selection of 85 towers (model inputs resampled to a common grid to facilitate global estimates) confirmed the original findings.« less