Conflicting Hydraulic Effects of Xylem Pit Structure Relate to the Growth-Longevity Tradeoff in a Conifer Species

Consistent with a ubiquitous life history tradeoff, trees exhibit a negative relationship between growth and longevity among and within species. However, the mechanistic basis of this life history tradeoff is not well understood. In addition to tradeoffs among multiple traits based on resource allocation conflicts, life history tradeoffs may arise from tradeoffs based on single traits under opposing selection. While a myriad of factors likely contribute to the growth-longevity tradeoff in trees, we hypothesized that conflicting functional effects of xylem structural traits contribute to the growth-longevity tradeoff. We tested this hypothesis by examining the extent to which xylem morphological traits (i.e. wood density, tracheid diameters and pit structure) relate to growth rates and longevity in two natural populations of the conifer species ponderosa pine. We examined xylem morphological traits and growth rates at the base of the trunk. As hydraulic constraints arise as trees grow larger, xylem anatomical traits are expected to adjust to compensate for these constraints. We therefore disentangled the effects of size through ontogeny and growth rates on xylem traits by sampling each individual tree at multiple trunk diameters. We found that the oldest trees had slower lifetime growth rates compared to younger trees in the populations we studied, indicating a growth-longevity tradeoff. We further provide the first evidence that a single xylem trait, pit structure, with known conflicting effects on xylem function (hydraulic safety vs. efficiency) contributes to the growth-longevity tradeoff in a conifer species

Regional variation in digital cushion pressure in the forefeet of horses and elephants

In this study, we seek to understand how the digital cushion morphologies evident in horse and elephant feet influence internal and external foot pressures. Our novel use of invasive blood pressure monitoring equipment, combined with a pressure pad and force plate, enabled measurements of (ex vivo) digital cushion pressure under increasing axial loads in seven horse and six elephant forefeet. Linear mixed effects models (LMER) revealed that internal digital cushion pressures increase under load and differ depending on region; elephant feet experienced higher magnitudes of medial digital cushion pressure, whereas horse feet experienced higher magnitudes of centralised digital cushion pressure. Direct comparison of digital cushion pressure magnitudes in both species, at equivalent loads relative to body weight, revealed that medial and lateral pressures increased more rapidly with load in elephant limbs. Within the same approximate region, internal pressures exceeded external, palmar pressures (on the sole of the foot), supporting previous Finite Element (FE) predictions. High pressures and large variations in pressure may relate to the development of foot pathology, which is a major concern in horses and elephants in a captive/domestic environment

Energy Storage - Driving towards a clean energy future

No abstract available

Technoeconomic, environmental and multi criteria decision making investigations for optimisation of off-grid hybrid renewable energy system with green hydrogen production

The current study presents a comprehensive investigation of various energy system configurations for a remote village community in India with entirely renewable electricity. Excess electricity generated by the systems has been stored using two types of energy storage options: lithium-ion batteries and green hydrogen production through the electrolysers. The hybrid renewable energy system (HRES) configurations have been sized by minimising the levelised cost of energy (LCOE). In order to identify the best-performing HRES configuration, economic and environmental performance indicators has been analysed using the multi-criteria decision-making method (MCDM), TOPSIS. Among the evaluated system configurations, system-1 with a photovoltaic panel (PV) size of 310.24 kW, a wind turbine (WT) size of 690 kW, a biogas generator (BG) size of 100 kW, a battery (BAT) size of 174 kWh, an electrolyser (ELEC) size of 150 kW, a hydrogen tank (HT) size of 120 kg, and a converter (CONV) size of 106.24 kW has been found to be the best-performing system since it provides the highest relative closeness (RC) value (∼0.817) and also has the lowest fuel consumption rate of 2.31 kg/kWh. However, system-6 shows the highest amount of CO2 (143.97 kg/year) among all the studied system configurations. Furthermore, a detailed technical, economic, and environmental analysis has been conducted on the optimal HRES configuration. The minimum net present cost (NPC), LCOE, and cost of hydrogen (COH) for system 1 has been estimated to be $1,960,584,$0.44/kWh, and $22.3/kg, respectively

An optimised chemisorption cycle for power generation using low grade heat

The integration of chemisorption cycle with turbine/expander opens up enormous opportunities of recovering low grade heat to meet different energy demands including heating, cooling and power generation. In the present study, a novel advanced resorption power generation (RPG) cycle with reheating process has been proposed for the first time to significantly improve the thermal efficiency and exergy efficiency of the basic RPG cycle. Such a reheating concept is built on the premise of chemisorption monovariant characteristic and identification of the optimal desorption temperature aiming at producing the maximum work output under the given working conditions. The identified optimal desorption temperature might be lower than the available heat source temperature, and the desorbed ammonia vapour is subsequently reheated to the heat source temperature before it undergoes vapour expansion for power generation. This study explored the potential of the proposed advanced RPG cycle and investigated the system performance using three representative resorption sorbent pairs, including manganese chloride – sodium bromide, manganese chloride – strontium chloride, and strontium chloride – sodium bromide, all with ammonia as the refrigerant. The application of reheating concept can improve the total work output of RPG cycle by 10–600%, depending on different sorbent pairs and different heat source temperatures studied in this work, e.g., when the heat source temperature is at 200 °C, the thermal efficiency is increased by 1.4–4.5 times and the exergy efficiency is boosted by 2.0–8.3 times. Another valuable merit of the proposed RPG cycle is that there is a great potential of considerable amount of additional cooling output without compromising the maximum work output, leading to further improvement of system efficiency. Compared to other bottoming cycles for power generations, the proposed advanced RPG cycle exhibits the highest thermal efficiency when the heat source temperature is between 120 °C and 200 °C

Feasibility study of seasonal solar thermal energy storage in domestic dwellings in the UK

Seasonal solar thermal energy storage (SSTES) has been investigated widely to solve the mismatch between majority solar thermal energy in summer and majority heating demand in winter. To study the feasibility of SSTES in domestic dwellings in the UK, eight representative cities including Edinburgh, Newcastle, Belfast, Manchester, Birmingham, Cardiff, London and Plymouth have been selected in the present paper to study and compare the useful solar heat available on dwelling roofs and the heating demand of the dwellings. The heating demands of space and hot water in domestic dwellings with a range of overall heat loss coefficients (50 W/K, 150 W/K and 250 W/K) in different cities were calculated; then the useful heat obtained by the heat transfer fluid (HTF) flowing through tilted flat-plate solar collectors installed on the dwelling roof was calculated with varied HTF inlet temperature (30 °C, 40 °C and 50 °C). By comparing the available useful heat and heating demands, the critical solar collector area and storage capacity to meet 100% solar fraction have been obtained and discussed; the corresponding critical storage volume sizes using different storage technologies, including sensible heat water storage, latent heat storage and various thermochemical sorption cycles using different storage materials were estimated

Bioenergy production from pretreated rice straw in Nigeria: An analysis of novel three-stage anaerobic digestion for hydrogen and methane co-generation

The response to Nigeria's energy inadequacies and waste management issues is projected in this research to be achieved with hydrogen and methane co-produced from pretreated (PT) rice straw (RS) in a three-stage digestion process. This study also demonstrated a novel pretreatment (PTM) agent to improve biological energy recovery from RS. The objectives were accomplished using acidogenic and methanogenic procedures in batch, semi-continuous and continuous systems after pretreating RS with chemical/potash extract (PE) followed by a biological agent. At the same time, the energy assessments were done using data from the laboratory study and the literature. The research findings indicated that at the acidogenesis stage, specific hydrogen yield was insignificant when chemical agents and PE were employed alone. However, the daily H2 production increased when the PT RS residues were enzymatically hydrolysed with NaOH-PT (114 NmL H2 g−1 TS d−1) and PE-PT (103 NmL H2 g−1 TS d−1) RS substrates having the highest values at steady states and raw RS producing the least (30 NmL H2 g−1 TS d−1). In the methanogenesis phase, chemical/ PE PTM followed by enzymatic hydrolysis of RS improved the daily specific methane production by 18%, 31.7% and 41.5% for HCl, PE and NaOH-PT RS residues. The methane production efficiency was 80% for NaOH, 75% for PE, and 68% for HCl RS PT samples, while the raw RS was 48%. The total output energy expressed in electricity and thermal production using combined cooling, heat, and power (CCHP) showed that NaOH and PE-PT RS digesters gave the highest electricity (892.43 and 852.00 KWhelect. tonne-1 TS) and thermal (1194.10 and 1140 KWhtherm. tonne-1 TS) yield respectively. Similarly, the cooling fluid in KWhcool produced per tonne of TS RS was 835.57, 798.00 and 741.66 for NaOH, PE and HCl PT RS samples. Finally, whereas the Firmicutes, especially the Clostridium, Ruminococcus and Thermoanaerobacterium, were the dominant microbial community in acidogenic digestates, the Euryarchaeota typified by Methanobacterium, Methanosarcina and Methanosaeta were the principal phyla for most methanogenic reactors

The Development and Application of Organic Rankine Cycle for Vehicle Waste Heat Recovery

The development of engine waste heat recovery (WHR) technologies attracts ever increasing interests due to the rising strict policy requirements and environmental concerns. Organic Rankine Cycle (ORC) can convert low medium grade heat into electrical or mechanical power and has been widely recognized as the most promising heat-driven technologies. A typical internal combustion engine (ICE) converts around 30% of the overall fuel energy into effective mechanical power and the rest of fuel energy is dumped through the engine exhaust system and cooling system. Integrating a well-designed ORC system to ICE can effectively improve the overall energy efficiency and reduce emissions with around 2–5 years payback period through fuel saving. This book chapter is meant to provide an overview of the technical development and application of ORC technology to recover wasted thermal energy from the ICE with a particular focus on vehicle applications

Techno-economic analysis on a small-scale organic Rankine cycle with improved thermal driven pump

Acknowledgments: This research was supported by European Union’s Horizon 2020 Research and Innovation Programme under grant number (895767) and National Natural Science Foundation of China under contract number (51606118).Peer reviewedPostprin