• Energy Research
• 7. Clean energy close
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Short-term load forecasting is an essential instrument in power system planning, operation and control. Many operating decisions are based on load forecasts, such as dispatch scheduling of generating capacity, reliability analysis, and maintenance planning for the generators. Overestimation of electricity demand will cause a conservative operation, which leads to the start-up of too many units or excessive energy purchase, thereby supplying an unnecessary level of reserve. On the contrary, underestimation may result in a risky operation, with insufficient preparation of spinning reserve, causing the system to operate in a vulnerable region to the disturbance. In this paper, semi-parametric additive models are proposed to estimate the relationships between demand and the driver variables. Specifically, the inputs for these models are calendar variables, lagged actual demand observations and historical and forecast temperature traces for one or more sites in the target power system. In addition to point forecasts, prediction intervals are also estimated using a modified bootstrap method suitable for the complex seasonality seen in electricity demand data. The proposed methodology has been used to forecast the half-hourly electricity demand for up to seven days ahead for power systems in the Australian National Electricity Market. The performance of the methodology is validated via out-of-sample experiments with real data from the power system, as well as through on-site implementation by the system operator.

AbstractHerein, we present ultrasmall delafossite‐type Mg‐doped CuCrO2 nanocrystals prepared by using hydrothermal synthesis and their first application as photocathodes in efficient p‐type dye‐sensitized solar cells. The short‐circuit current density (Jsc) is notably increased by approximately 27 % owing to the decreased crystallite size and the enhanced optical transmittance associated with Mg doping of the CuCrO2 nanocrystalline sample. An open‐circuit voltage (Voc) of 201 mV, Jsc of 1.51 mA cm−2, fill factor of 0.449, and overall photoconversion efficiency of 0.132 % have been achieved with the CuCr0.9Mg0.1O2 dye photocathode sensitized with the P1 dye under optimized conditions. This efficiency is nearly three times higher than that of the NiO‐based reference device, which is attributed to the largely improved Voc and Jsc. The augmentation of Voc and Jsc can be attributed to the lower valance band position and the faster hole diffusion coefficient of CuCr0.9Mg0.1O2 compared to those of the NiO reference, respectively, which leads to a higher hole collection efficiency.

Electricity generation systems have traditionally been evaluated using only a limited number of economic or environmental indicators, for example capital investment, generation cost or carbon dioxide emissions. Moreover, the evaluations have generally been restricted to performance within the geographic boundary of the power station. This paper reports a sustainability assessment of power generation from Australian fossil fuels, notably black coal, brown coal and natural gas. A range of key sustainability indicators incorporating environmental, economic and social performance are included. The system boundary incorporates fuel extraction, fuel transport to the power station, generation of power, and transmission of electricity to the point of use. Most commonly employed existing technologies and some promising advanced technologies for power generation are considered. The cases of exporting Australian LNG and black coal to Japan for power generation in that country have also been considered. No one fuel or technology system was superior or inferior for every indicator. However the following generalizations can be made: Natural gas combined cycle systems have advantages for the majority of environmental and economic indicators, brown coal has an advantage in terms of value added, and black coal has relatively poor safety performance.

Abstract The use of electric bus fleets has become a topical issue in recent years. Several companies and municipalities, either voluntarily or to comply with legal requirements, will transition to greener bus fleets in the next decades. Such transitions are often established by fleet electrification targets, which dictate the number of electric buses that should be in the fleet by a given time period. In this paper we introduce a comprehensive optimization-based decision making tool to support such transitions. More precisely, we present a fleet replacement problem which allows organizations to determine bus replacement plans that will meet their fleet electrification targets in a cost-effective way, namely considering purchase costs, salvage revenues, operating costs, charging infrastructure investments, and demand charges. We account for several charging infrastructure options, such as slow and fast plug-in stations, overhead pantograph chargers, and inductive (wireless) chargers. We refer to this problem as the electric bus fleet transition problem, and we model it as an integer linear program. We apply our model to conduct computational experiments based on several scenarios. We use real data provided by a public transit agency in order to draw insights into optimal transition plans.

AbstractNutrient enrichment can simultaneously increase and destabilise plant biomass production, with co‐limitation by multiple nutrients potentially intensifying these effects. Here, we test how factorial additions of nitrogen (N), phosphorus (P) and potassium with essential nutrients (K+) affect the stability (mean/standard deviation) of aboveground biomass in 34 grasslands over 7 years. Destabilisation with fertilisation was prevalent but was driven by single nutrients, not synergistic nutrient interactions. On average, N‐based treatments increased mean biomass production by 21–51% but increased its standard deviation by 40–68% and so consistently reduced stability. Adding P increased interannual variability and reduced stability without altering mean biomass, while K+ had no general effects. Declines in stability were largest in the most nutrient‐limited grasslands, or where nutrients reduced species richness or intensified species synchrony. We show that nutrients can differentially impact the stability of biomass production, with N and P in particular disproportionately increasing its interannual variability.

AbstractWhile perovskite solar cell (PSC) efficiencies are soaring at a laboratory scale, these are most commonly achieved with evaporated gold electrodes, which would present a significant expense in large‐scale production. This can be remedied through the use of significantly cheaper carbon electrodes that, in contrast to metals, also do not migrate through the device. To this end, the present work investigates simple‐to‐prepare aluminum‐supported carbon electrodes derived from commercially available, inexpensive materials that can be applied onto various hole‐transporting materials and enable photovoltaic performances on par with those provided by gold electrodes. Successful integration of the new carbon‐based electrode into flexible devices produced by a roll‐to‐roll printing technology by both pressing and lamination is demonstrated. However, temperature cycling durability tests reveal that the use of carbon electrodes based on commercial pastes is hindered by incompatibility of adhesive additives with the key components of the PSCs under heating. Resolving this issue, tailor‐made graphite electrodes devoid of damaging additives are introduced, which improve the PSC stability under temperature cycling test protocol to the level provided by benchmark gold electrodes. The study highlights current challenges in developing laminated carbon electrodes in PSCs and proposes strategies toward the resolution thereof.

Because of the near-term risk of extreme weather events and other adverse consequences from climate change and, at least in the longer term, global fossil fuel depletion, there is worldwide interest in shifting to noncarbon energy sources, especially renewable energy (RE). Because of possible limitations on conventional renewable energy sources, researchers have looked for ways of overcoming these shortcomings by introducing radically new energy technologies. The largest RE source today is bioenergy, while solar energy and wind energy are regarded as having by far the largest technical potential. This paper reviews the literature on proposed new technologies for each of these three RE sources: microalgae for bioenergy, photolysis and airborne wind turbines. The main finding is that their proponents have often underestimated the difficulties they face and the time taken for their introduction on a very large scale.