Photosystem I Inhibition, Protection and Signalling: Knowns and Unknowns

Photosynthesis is the process that harnesses, converts and stores light energy in the form of chemical energy in bonds of organic compounds. Oxygenic photosynthetic organisms (i.e., plants, algae and cyanobacteria) employ an efficient apparatus to split water and transport electrons to high-energy electron acceptors. The photosynthetic system must be finely balanced between energy harvesting and energy utilisation, in order to limit generation of dangerous compounds that can damage the integrity of cells. Insight into how the photosynthetic components are protected, regulated, damaged, and repaired during changing environmental conditions is crucial for improving photosynthetic efficiency in crop species. Photosystem I (PSI) is an integral component of the photosynthetic system located at the juncture between energy-harnessing and energy consumption through metabolism. Although the main site of photoinhibition is the photosystem II (PSII), PSI is also known to be inactivated by photosynthetic energy imbalance, with slower reactivation compared to PSII; however, several outstanding questions remain about the mechanisms of damage and repair, and about the impact of PSI photoinhibition on signalling and metabolism. In this review, we address the knowns and unknowns about PSI activity, inhibition, protection, and repair in plants. We also discuss the role of PSI in retrograde signalling pathways and highlight putative signals triggered by the functional status of the PSI pool.

Comprehensive Survey of Seismic Hazard at Geothermal Sites by a Meta-Analysis of the Underground Feedback Activation Parameter afb

Global efforts to tame CO2 emissions include the use of renewable energy sources, such as geo-energy harnessing. However, injecting pressurised fluids into the deep underground can induce earthquakes, hence converting CO2-related risk into seismic risk. Induced seismicity hazard is characterised by the overall seismic activity afb that is normalised by the injected fluid volume V and the parameter b of the Gutenberg–Richter law. The (afb,b) set has so far been estimated for a dozen of reservoir stimulations, while at least 53 geothermal fluid stimulations are known to exist, based on our survey. Here, we mined the induced seismicity literature and were able to increase the number of estimates to 39 after calculating afb from related published parameters and by imputing b with its expectation where this parameter was missing (0.65 ≤ b ≤ 2.9, with mean 1.16). Our approach was a two-step procedure: we first reviewed the entire literature to identify seismic hazard information gaps and then did a meta-analysis to fill those gaps. We find that the mean and median afb estimates slightly decrease from afb ≈ −2.2 to afb = −2.9 and −2.4, respectively, and that the range of observations expands from −4.2 ≤ afb ≤ 0.4 to −8.9 ≤ afb ≤ 0.4, based on a comprehensive review unbiased towards high-seismicity experiments. Correcting for potential ambiguities in published parameters could further expand the range of possibilities but keep the mean and the median relatively close to original estimates, with afb ≈ −2.3 and −2.4, respectively. In terms of the number of earthquakes induced (function of 10afb), our meta-analysis suggests that it is about half the number that could previously be inferred from published afb estimates (i.e., half the seismic hazard). These results are hampered by high uncertainties, demonstrating the need to re-analyse past earthquake catalogues to remove any ambiguity and to systematically compute afb in future geothermal projects to reduce uncertainty in induced seismicity hazard assessment. Such uncertainties are so far detrimental to the further development of the technology.

Renewable energy policy around the globe

Renewable energy systems (RESs) have an inherent quality of achieving independence Vis a Vis useful energy harnessing for self or localized use. At larger scale the renewable energy system allows the power generation and distribution without a significant harm to the environment. Propagation and proliferation of RESs and the Renewable Energy Technology (RET), collectively demand an effective policy making infrastructure to be in place to ensure their penetration locally and globally. Renewable Energy Policies have a great impact on how readily these systems are adopted by the investors and market, how efficient these systems are which is dependent on the research and development (R&D) of RESs, how effectively the country or region copes with the scourge of environmental harm with the use of RESs. Renewable Energy Policies also have an impact on how costly these technologies are and how these technologies fiscally benefit common man, investors and industries. Efficiency enhancement, stability and intelligent management of grids integrated with RES are also renewable policy dependent. This paper thoroughly and critically examines the importance of renewable energy policy. not just at domestic or national level but also at global level. It discusses in detail the core ingredients of renewable energy policy which were adopted in the past, which are being adopted now and which should be adopted in future. This paper also discusses policy, business and financial models; importance of tariff formulation, incentives and subsidies and a few factors which may pose a risk to the development and adoption of RESs. At the end a few suggestions have also been made which, if adopted, would help promote the RESs proliferation across the globe at a rapid pace and would ensure energy security, sustainable development and environmental conservation.

Thermal Pollution Mitigation and Energy Harnessing of the Condensation Process of an Olive Oil Extraction Refinery: A Case Study

This paper presents a model to assess strategies for bettering a hexane condensation system from an olive oil extraction refinery in Portugal’s mountainous north. The water used as a cooling fluid is discharged with a higher temperature than the mountain river, provoking the deterioration of the aquatic flora and fauna, leading to high environmental impact. The model allowed the comparison of solutions for different temperatures of discharge for summer and winter and possible heat recovery back to the factory. The current condensation system power is 1.838 MW and consists of a four-walled pond of 115.3 m3 that cools down the submerged hexane pipes. Nudging in the pond’s structure leads to the introduction of internal channels to increase the turbulence, thus increasing the hexane–water heat exchange rate. Heat recovery of 19.38 kW is possible for the water coming from the pond in the drying bagasse process inside the factory, before discharge into the river. However, the model demonstrates that the decrease in temperature after the heat recovery process falls short of avoiding thermal pollution, leading to complementary actions such as shading the channel or changing the discharge velocity or angle to mitigate the thermal pollution locally.

Design and simulation of piezoelectric nano cylindrical hollow structure for energy harnessing applications

This article investigates piezoelectric materials for harnessing vibrational energy. A nano hollow cylindrical structure based on various piezoelectric materials was designed and utilised to generate the voltage. An accurate and efficient model is developed here, so as to optimized the efficiency of the piezoelectric energy harvester. This work analyses the piezoelectric actuator deflection and involves the Eigen frequency computation. A measurement methodology for investigating the mechanical and electrical behaviour of vibrational harvester's was modelled and analysed by finite element method using COMSOL software. The energy harvesting structure was developed and tested with different piezoelectric materials to attain appreciable voltage through a small deflection. The Simulated results predicts that for the same pressure range, different piezoelectric materials have the different output voltage and Eigen frequencies. The maximum voltage was observed for Barium Titanate (3.0847 V at 250 µm), along with poled Polyvinylidene fluoride. In addition, a comparison was made with different piezoelectric materials ideally suited to intelligent cantilever structure. For optimizing the performance of the piezoelectric energy harvester an accurate and efficient model is required, which was developed in this simulation study. A high voltage value with a small deflection through a cylindrical hollow structure was designed and tested using various piezoelectric materials in this study.