[en] Highlights: • We evaluate the impact of daylight saving time on electricity consumption in Mexico. • We use a differences-in-differences econometric approach to evaluate DST. • Our data covers a large period both before and after DST started in Mexico. • Residential savings due to DST represent 0.5% of total electricity consumption. • Savings are larger towards the end of the DST period. -- Abstract: Since the First World War, several countries use daylight saving time (DST). However, evaluations of DST started until the 1970s. Given the difficulties of finding data around the moment in which DST started, econometric studies usually evaluate changes to DST. We have aggregate data on residential electricity consumption in Mexico from 1982 to 2016. DST started in 1996. Therefore, our data covers a large period both before and after DST started. Moreover, DST is in effect only during part of the year (from April to October). Hence, we can evaluate the effects of DST with a differences-in-differences (DID) econometric approach. As far as we know, there is only another DID econometric study using similar data. Such study takes advantage of a short period in which DST was adopted and then repealed in Australia. Since our data covers a larger period, we can control for trends in consumption, calculate savings in different DST months, and run robustness tests. Our estimates indicate that savings due to DST account for 0.5% of total electricity consumption. Nevertheless, the effect of DST is not homogeneous along the period. This is important because estimates based on DST extensions may not reflect the effects of DST itself.

[en] Highlights: • Artificial light pollution (ALAN) is a growing concern for coastal species. • We assessed ALAN effects on a marine isopod in the field and the laboratory. • ALAN disrupted the intertidal distribution of the isopod in the field. • ALAN disrupted the locomotor activity and circadian rhythm in the laboratory. -- Abstract: Coastal habitats, in particular sandy beaches, are becoming increasingly exposed to artificial light pollution at night (ALAN). Yet, only a few studies have this far assessed the effects of ALAN on the species inhabiting these ecosystems. In this study we assessed the effects of ALAN on Tylos spinulosus, a prominent wrack-consumer isopod living in sandy beaches of north-central Chile. This species burrows in the sand during daylight and emerges at night to migrate down-shore, so we argue it can be used as a model species for the study of ALAN effects on coastal nocturnal species. We assessed whether ALAN alters the distribution and locomotor activity of this isopod using a light system placed in upper shore sediments close to the edge of the dunes, mimicking light intensities measured near public lighting. The response of the isopods was compared to control transects located farther away and not exposed to artificial light. In parallel, we measured the isopods’ locomotor activity in the laboratory using actographs that recorded their movement within mesocosms simulating the beach surface. Measurements in the field indicated a clear reduction in isopod abundance near the source of the light and a restriction of their tidal distribution range, as compared to control transects. Meanwhile, the laboratory experiments showed that in mesocosms exposed to ALAN, isopods exhibited reduced activity and a circadian rhythm that was altered and even lost after a few days. Such changes with respect to control mesocosms with a natural day/night cycle suggest that the changes observed in the field were directly related to a disruption in the locomotor activity of the isopods. All together these results provide causal evidence of negative ALAN effects on this species, and call for further research on other nocturnal sandy beach species that might become increasingly affected by ALAN.

[en] Historic estimates of daily global solar irradiation are often required for climatic impact studies. Regression equations with daily global solar irradiation, H, as the dependent variable and other climatic variables as the independent variables provide a practical way to estimate H at locations where it is not measured. They may also have potential to estimate H before 1953, the year of the first routine H measurements in Canada. This study compares several regression equations for calculating H on the Canadian prairies. Simple linear regression with daily bright sunshine duration as the dependent variable accounted for 90% of the variation of H in summer and 75% of the variation of H in winter. Linear regression with the daily air temperature range as the dependent variable accounted for 45% of the variation of H in summer and only 6% of the variation of H in winter. Linear regression with precipitation status (wet or dry) as the dependent variable accounted for only 35% of the summer-time variation in H, but stratifying other regression analyses into wet and dry days reduced their root-mean-squared errors. For periods with sufficiently dense bright sunshine observations (i.e. after 1960), however, H was more accurately estimated from spatially interpolated bright sunshine duration than from locally observed air temperature range or precipitation status. The daily air temperature range and precipitation status may have utility for estimating H for periods before 1953, when they are the only widely available climatic data on the Canadian prairies. Between 1953 and 1989, a period of large climatic variation, the regression coefficients did not vary significantly between contrasting years with cool-wet, intermediate and warm-dry summers. They should apply equally well earlier in the century. (author)

[en] Light pipe systems (LPS) are simple devices that allow the transmission of daylight into interiors of buildings. It is a convenient concept for illumination of windowless parts of buildings. The light performance of this is highly dependent on the solar altitude due to the small inlet aperture. Placing the laser-cut panel (LCP) at the entrance aperture in light pipe system, will increase the light performance during low solar angle. This paper presents the results of light performance a 400mm diameter light pipe integrated with a laser-cut panel at entrance aperture as collector. For that reason, this research adopted an experimental approach to compare the light pipe performance via 1:10 scale model. Two scale models were built. LCP in the form of pyramids was fitted at the entrance aperture of light pipe in different tilted angle 40° and 47.5°. The system has been monitored 30 minutes interval with lux meter to evaluate the improvement light performance on a working plane for 6 days under good sky condition. The results of this experiment shows that LCP with 40° tilted angle performed better than 47.5° tilted angle. The light pipe with LCP as collector the minimum recommended illuminance by Malaysian Standard (MS) 1525:2007 can be achieved as early at 8am. (paper)

[en] The structure of a modified photo detecting head with a photoresistor and spectral sensitivity V is put to consideration. The characteristics of the spectral sensitivity and the cosine error of the photodetector are shown. An electronic measuring transducer with linear dependence of the output voltage on the illumination was developed for the head. The structure of a 3-channel system for synchronous measurement and recording of the illumination within the range 0-100 klx with maximum relative error of +- 5% is presented

[en] Two optically brightened commercial papers were subjected to 72 hours continuous exposure to graphic arts daylight simulating fluorescent lamps at 1.4 and 4.4 klux. At the higher illuminance level, a CIELAB colour difference of 1.0 was reached in approximately 3 and 50 hours for the two papers. The colour differences produced by the 1.4 klux exposure were greater than that predicted by assuming a linear relationship between intensity and colour change, by a factor of 1.8.

No abstract available

[en] Highlights: ► Estimation of diffuse horizontal and vertical (N, S, E, W) illuminance at Madrid. ► Monthly mean of hourly values are obtained based on a data series of 26 years. ► Tables representing the climatic behavior of diffuse illuminance are given. ► Empirical luminous efficacy models with local coefficients are used. ► The influence of the nubosity on the illuminance levels have been analyzed. - Abstract: The overall objective of this work is to provide diffuse illuminance availability at Madrid (Spain) through a statistical analysis of illuminance values corresponding to a long-term data series. The illuminance values are obtained from irradiance measurements by means of different empirical models for luminous efficacy. The values of diffuse illuminance on a horizontal and on vertical surfaces facing the four cardinal points are estimated and the different aspects related to daylight availability in an area with specific climatic conditions are analyzed. The experimental data consist of global and diffuse irradiance measurements on a horizontal surface provided by the National Meteorological Agency in Spain (AEMET) for Madrid. These data consist of hourly values measured in the period of 1980–2005. The statistical results derived correspond to a daylight typical year for the five surfaces considered. This information will be useful to building experts to estimate natural illumination availability when daylighting techniques are applied in building design with the main aim of electric energy savings.

[en] Highlights: • Load data shows that the temperature effect is both non-linear and non-homogenous. • Time properties of economic activity directly translate into the shape of load curves. • Economic activity also affects the way temperature influences the electricity load. • A model for hourly electricity load with differentiated temperature effects by time of day is proposed. • The proposed model captures well the higher sensitivity of electricity demand to temperatures in the “active” state. -- Abstract: This paper proposes a model for short-term electricity load with differentiated temperature and daylight effects by time of day, which are determined by variations in intraday economic activity. The relationship between electricity load and economic activity implies that the electricity demand response to changes in exogenous variables like temperature is non-linear as well as non-homogeneous along the day. The proposed framework, a smooth transition regression model with double threshold (LSTR2), models the observed intraday patterns in load curves to explicitly capture the effect of the circadian rest-activity cycle on the distinct responses of electricity demand to temperature and daylight variations throughout the day. The model shows that the sensitivity of demand to low temperatures is significantly larger in the “active” compared to the “rest” state. If temperatures decrease from 10 °C to 0 °C, electricity demand in the “active” state increases by 960.5 MW h per 1 °C decrease, but by only 26.6 MW h per 1 °C decrease in the “rest” state. When temperatures are higher, in the “rest state” demand decreases by 602.9 MW h per 1 °C if temperature falls from 26 °C to 21 °C, while in the “active” state demand only decreases by 323.6 MW h per 1 °C variation.

[en] Many countries have experimented with daylight saving time (DST) to save energy and to align human activities more closely to the daily cycle of light and darkness. Using a novel methodology, we estimate the year-round energy savings to be obtained from advancing Indian Standard Time (IST), from the introduction of DST, and from dividing the country into two time zones. We find that the option of advancing IST consistently saves more energy than the corresponding DST option, which in turn saves more energy than the corresponding time zones option. This is because the energy benefits of advancing IST accrue for the entire year throughout the country, whereas the benefits of DST are confined to summer months and the benefits of two time zones are largely in the lower energy consuming eastern region. We recommend advancing IST by half-hour to being six hours ahead of UTC. This confers the advantages of DST and time zones without their disadvantages and is forecast to save more than 2 billion kWh of electricity every year during evening peaks that are difficult to supply. While these results are India-specific, similar exercises would be useful to many other countries. - Highlights: ► Advancing IST (YRDST) consistently saves more energy than the corresponding DST. ► DST consistently saves more energy than dividing India into two time zones. ► There are also many non-energy benefits of advancing IST. ► Results are for India; countries with DST may find it useful to consider YRDST.