Large-scale unit commitment under uncertainty: an updated literature survey

The Unit Commitment problem in energy management aims at finding the optimal production schedule of a set of generation units, while meeting various system-wide constraints. It has always been a large-scale, non-convex, difficult problem, especially in view of the fact that, due to operational requirements, it has to be solved in an unreasonably small time for its size. Recently, growing renewable energy shares have strongly increased the level of uncertainty in the system, making the (ideal) Unit Commitment model a large-scale, non-convex and uncertain (stochastic, robust, chance-constrained) program. We provide a survey of the literature on methods for the Uncertain Unit Commitment problem, in all its variants. We start with a review of the main contributions on solution methods for the deterministic versions of the problem, focussing on those based on mathematical programming techniques that are more relevant for the uncertain versions of the problem. We then present and categorize the approaches to the latter, while providing entry points to the relevant literature on optimization under uncertainty. This is an updated version of the paper "Large-scale Unit Commitment under uncertainty: a literature survey" that appeared in 4OR 13(2), 115--171 (2015); this version has over 170 more citations, most of which appeared in the last three years, proving how fast the literature on uncertain Unit Commitment evolves, and therefore the interest in this subject

Lithium doped zinc oxide based flexible piezoelectric-triboelectric hybrid nanogenerator

Piezoelectric and Triboelectric hybrid nanogenerators (PTENG) have attracted scientific attention due to their ability to efficiently harvest mechanical energy. Thus, they have been promoted as a potential replacement of conventional energy generation devices and stress sensors. In this study, we report a cost-effective unpoled PTENG composed of a Polyvinylidene fluoride matrix with insertion of surface modified Lithium Doped Zinc Oxide (Li–ZnO) Nanowires (NWs) and Multiwalled Carbon Nanotubes (MWCNTs) as a piezoelectric film, along with Polydimethylsiloxane (PDMS)- Polytetrafluoroethylene (PTFE) co-polymers on thin Aluminium (Al) film as a triboelectric layer. The device was tested with variable load conditions to examine its capability of functioning as a nanogenerator as well as a pressure sensor. The results indicate that surface modification enhances piezoelectric response while reducing the probability of a surface dielectric hindrance due to thinner Polyethylene glycol surface film on Li–ZnO NW. The linear response to applied stress enables the device to be used as load measuring module. Maximum output voltage under constant load was found to be 60.1 V and current production was 75 μA. Under constant-frequency load, PTENG exhibited a high degree of micro-stresses. Hence it continuously produced electricity. This demonstration shows that PTENG can be utilized as a real-life superior power generation device and self-powered transducer

Polymer Based Triboelectric Nanogenerator for Cost-Effective Green Energy Generation and Implementation of Surface-Charge Engineering

Performance of triboelectric nanogenerators for harvesting mechanical energy from the ambient environment has been limited by structural complexity, cost-effectiveness, and mechanical weakness of materials. Herein, a cost-effective vertical contact separation mode triboelectric nanogenerator using polyethylene (PE) and polycarbonate (PC) in a regular digital versatile disc is reported. This cost-effective nanogenerator with simplified structures is able to generate an open-circuit voltage of 215.3 V and short-circuit current of 80 μA. The effects of the distance of impact and the air gap between the triboelectric layers have also been tested from 3 to 9 cm, and 0.25 to 1 cm, respectively. It is determined that 0.5 cm is the optimal air gap. The nanogenerator is also tested in different real-life scenarios including stresses produced by a moving car, walking, and a rolling skateboard over the nanogenerator. The surfaces of the triboelectric layers are further modified by surface-charge engineering which induced a 460% increase in the output power. These tests reveal a significant electrical response and mechanical stability under stress. In summary, this study demonstrates that the relatively inexpensive PE and PC triboelectric pair has the potential to be used for highly efficient, mechanically robust triboelectric nanogenerators

Polar Travel

No abstract availabl

Travel Writing and the Desert

No abstract availabl

Eighteenth-century travel writing

No abstract available