Atmospheric extinction coefficients and night sky brightness at the Xuyi Observation Station

We present measurements of the optical broadband atmospheric extinction coefficients and the night sky brightness at the Xuyi Observation Station of Purple Mountain Observatory. The measurements are based on CCD imaging data taken in the Sloan Digital Sky Survey＇s g, r and i bands with the Xuyi 1.04/1.20m Schmidt Telescope for the Xuyi Schmidt Telescope Photometric Survey of the Galactic Anticenter （XSTPS-GAC）, the photometric part of the Digital Sky Survey of the Galactic Anti-center （DSS-GAC）. The data were collected during more than 140 winter nights from 2009 to 2011. We find that the atmospheric extinction coefficients for the g, r and i bands are 0.69, 0.55 and 0.38 mag/airmass, respectively, based on observations taken on several photometric nights. The night sky brightness determined from images with good quality has median values of 21.7, 20.8 and 20.0 mag arcsec-2 and reaches 22.1, 21.2 and 20.4mag arcsec-2 under the best observing conditions for the g, r and i bands, respectively. The relatively large extinction coefficients compared with other good astronomical observing sites are mainly due to the relatively low elevation （i.e. 180 m） and high humidity at the station.

Seasonal coolth storage system for residential buildings in Australia

Night sky cooling is explored as an alternative to the conventional cooling technologies using fossil fuels. The night sky cooling method is based on the long wave radiation of unglazed collectors to the sky at night. An evaluation of the night sky cooling system is present for a residential building in three cities of Australia, namely Alice Springs, Darwin and Melbourne. The system comprises an unglazed flat plate solar collector integrated with borehole storage. It uses night sky radiation to reduce the temperature of the ground near to the boreholes. The system was simulated with TRNSYS, a transient simulation program. The simulation results for adequately sized systems show that night sky radiation is able to reduce the coolth storage borehole temperature and the proposed system is able to meet the cooling load of the residential building simulated in three locations. Borchole lengths of 270, 318 and 106 m are required for coolth storage with 90, 260 and 14 m2 collector area for heat rejection in Alice Springs, Darwin and Melbourne, respectively. At the 20th simulation year, the proposed system is able to achieve a system cooling coefficient of performance of 2.2 in Alice Springs, and 2.8 in Darwin and Melbourne.

THE SIMULATION ANALYSIS OF A PROPOSED‘HYDRONIC RADIATOR’SYSTEM TOWARDS LOW COST HOUSING OPERATION IN TEMPERATE AND HOT TROPICAL CLIMATES

Fuel poverty is one of the global concerns affecting not only users’financial capacity or affordability for maintaining housing operation but also the occupants’health and wellbeing.Space heating and cooling require a relatively large amount of domestic energy use in housing.Therefore,this study was formed with the aim to propose an innovative approach to utilising free,clean renewable sources of energy applicable to the space heating and cooling of housing in both cold and hot regions.Accordingly,housing test facilities based in Melbourne,Australia,and Kuching,Malaysia,were selected and used for this study that examined the thermal performance of a proposed‘hydronic radiator’(HR)system through simulation and onsite measurements.The geothermal heat capacity of a‘vertical ground heat exchanger’(VGHE)installed in the house in Melbourne was examined previously by the authors and the VGHE measured data was also applied to this HR performance simulation.The water that circulates through the HRs is heated by sunlight and VGHE or cooled by night sky radiation.This study drew conclusions that the sole utilisation of renewable sources through these proposed HR space heating and cooling systems can provide thermally accessible or comfortable indoor living environments in both heating or cooling dominant regions.Thus,fuel poverty issues may be alleviated through HR system application.The HRs can remove a‘sensible’portion of metabolic heat,but they cannot effectively contribute to the‘latent’heat removal.Thus,the future potential use or effect of‘flow-through’HRs,which are integrated into a underfloor air distribution(UFAD)plenum,was also dsicussed in this study.In the test house located in Melbourne,the flow-through HR UFAD system is currently under development.Therefore,the performance will be measured once the system has come into operation for further testing.