| Work Detail |
Solar pre-cooling is the use of residential photovoltaic systems to run air conditioners to pre-cool residential and commercial buildings. It offers benefits in terms of mitigating low minimum demand on electricity grids, flattening the net demand profile of the grid and reducing electricity bills.
Australian researchers have studied how rooftop PV generation used to run air conditioners (ACs) to pre-cool residential and commercial buildings can improve cost savings for households, while mitigating the so-called duck curve.
The proposed solar precooling concept, which the scientists developed in previous research, views the thermal mass of buildings as a virtual battery that could be used to crowd out or reduce demand spikes caused by air conditioning systems. It can be applied to all types of buildings that have an AC unit and can be more beneficial if the surplus PV generation during the day is used to pre-cool the building instead of importing electricity from the grid. The AC unit is turned on before peak demand hours with lower thermostat setpoints to pre-cool the thermal mass and indoor air in the home.
“In our previous study, we only simulated precooling,” Shayan Naderi, lead author of the research, told pv magazine . “The novelty of our new work consists in using the measured demand for AC, the photovoltaic generation and the load profile of homes, and grouping them according to their type of load. We have also calculated the benefits of solar pre-cooling for different groups of homes and types of buildings.”
The analysis took into account the grid feed-in charges currently paid in Australia for residential rooftop PV generation, three different categories of residential building types called 2-, 6-, and 8-star homes representing old, new, or renovated homes. , respectively, and their net demand profiles. For each category, three different build weights were simulated for Adelaide, Melbourne, Sydney and Brisbane.
The analysis also took into account the reduction of maximum demand, the mitigation of minimum demand, the reduction of import peaks, the improvement of self-consumption and cost savings. It was carried out with a data set provided by the energy monitoring and management service provider Solar Analytics Pty. Ltd, which includes hourly data of net demand, AC demand and photovoltaic generation of 349 households during the period from 1 December 2018 and February 28, 2019.
“The temporal pattern of PV generation and household demand are contributing factors to solar pre-cooling potential,” the researchers noted. “There is a significant difference between the overall magnitude of the excluded AC hourly average net demand profiles between houses.”
They identified four dominant groups of AC-excluded net demand profiles in the 349 households and stated that only one of the groups, representing only 3% of households, does not offer technical and economic potential for solar pre-cooling. “The other three clusters, representing 97% of the solar homes analysed, have net demand excluding duck-shaped AC and offer demand profile improvement through solar pre-cooling,” they stated, noting that these results are achieved regardless of the energy efficiency of the building.
The improvement of the “flattened” demand profile is mainly due to the mitigation of the minimum demand, with a maximum capacity of the photovoltaic system of 4 kW. The action of solar pre-cooling, for its part, turned out to be limited mainly by the size of the AC and the surplus of PV generation, and not by the thermal comfort of the occupants.
The research results were reported in the article “ Clustering-based analysis of residential duck curve mitigation through solar pre-cooling: A case study of Australian housing stock ”. Solar Pre-Cooling: An Australian Housing Stock Case Study), published in Renewable Energy . The research group consists of scientists from the Commonwealth Scientific and Industrial Research Organization (CSIRO) and the University of New South Wales (UNSW). |
