The optimal design and operation strategy of renewable energy-CCHP coupled system applied in five building objects

Abstract(#br)Combined cooling, heating, and power (CCHP) is an economic and eco-friendly technology to mitigate energy issues with remarkable energy efficiency improvement. This study formulates a mixed integer nonlinear programming (MINLP) model for a combined CCHP system coupled with renewable energy, i.e. RCCHP system, which is applied in five different buildings to evaluate the economic and environmental performance under two optimization modes. Net present value (NPV), internal rate of return (IRR) and dynamic payback period (DPP) are introduced as economic indexes, while CO 2 emission reduction rate (CER) is considered as the environmental indicator to determine the optimal combination, capacity, and operation strategies for energy technologies. Results indicate that a combination of electricity purchased at valley period during night with power generated by the combined heating and power (CHP) unit coupled with wind turbine in peak period during daytime is cost-optimal which also enables higher energy efficiency. Meanwhile, the feed-in tariff as well as the uncoordinated electrical and thermal loads both show a significant impact on real-time operation strategies. Compared with the reference separate production (SP) system, the combined system shows better performance when applied to shopping mall under both optimization modes, e.g., with NPV up to 67.65 and 46.61 million RMB, IRR up to 20.70% and 25.10%, and the minimum DPP is 5.49 and 4.82 years under NPV and IRR maximization, respectively

Sufficient numbers of early germ cells are essential for female sex development in zebrafish.

The sex determination for zebrafish is controlled by a combination of genetic and environmental factors. The determination of sex in zebrafish has been suggested to rely on a mechanism that is affected by germ cell-derived signals. To begin our current study, a simplified and efficient germ cell-specific promoter of the dead end (dnd) gene was identified. Utilizing the metrodinazole (MTZ)/ bacterial nitroreductase (NTR) system for inducible germ cell ablation, several stable Tg (dnd:NTR-EGFP(-3'UTR)) and Tg (dnd:NTR-EGFP(+3'UTR)) zebrafish lines were then generated with the identified promoter. A thorough comparison of the expression patterns and tissue distributions of endogenous dnd and ntr-egfp transcripts in vivo revealed that the identified 2032-bp zebrafish dnd promoter can recapitulate dnd expression faithfully in stable transgenic zebrafish. The correlation between the levels of the germ cell-derived signals and requirement for maintaining the female fate has been also explored with different durations of the MTZ treatments. Our results revealed the decreasing ratios of female presented in the treated transgenic group are fairly associated with the reducing levels of the early germ cell-derived signals. After the juvenile transgenic fish treated with 5 mM MTZ for 20 days, all MTZ-treated transgenic fish exclusively developed into males with subfertilities. Taken together, our results identified here a simplified and efficient dnd promoter, and provide clear evidence indicating that it was not the presence but the sufficiency of signals derived from germ cells that is essential for female sex development in zebrafish. Our model also provides a unique system for sex control in zebrafish studies

Gonadal expression of the <i>dnd^+3’UTR</i>:NTR-EGFP and <i>dnd^-3’UTR</i>:NTR-EGFP transgene in adult zebrafish.

<p>Anatomical views of the gonadal expression of the NTR-EGFP transgene are presented in A-D; Views of NTR-EGFP trangene expression and histological features with HE staining in the cyosectioned gonadal tissue are presented in E-H and I-L; A and B) Expression of the transgene in zebrafish ovary (A) and testis (B) in <i>dnd^+3’UTR</i>:NTR-EGFP transgenic fish at 100 dpf; C and D) Expression of the transgene in zebrafish ovary (C) and testis (D) in <i>dnd^-3’UTR</i>:NTR-EGFP transgenic fish at 100 dpf; E and F) NTR-EGFP transgene expression in the cryosections of the ovary (E) and testis (F) of the F1 progenies of <i>dnd^+3’UTR</i>:NTR-EGFP transgenic fish at 100 dpf; G and H) NTR-EGFP transgene expression in the cryosections of the ovary (G) and testis (H) of the F1 progenies of <i>dnd^-3’UTR</i>:NTR-EGFP transgenic fish at 100 dpf; I-J) histological features with HE staining for the I-J) shows the HE staining for the cryosections of the ovary (I) and testis (J) of the F1 progenies of <i>dnd^+3’UTR</i>:NTR-EGFP transgenic fish at 100 dpf; K-L) shows the HE staining for the cryosections of the ovary (K) and testis (L) of the F1 progenies of <i>dnd^-3’UTR</i>:NTR-EGFP transgenic fish at 100 dpf; Fluorescence was observed in the oocytes at all stages (E, G, I, K) and in spermatocytes(sc) and sperm(sp) (F, H, J, L).</p

Detection of the transcripts of <i>dnd</i> and <i>ntr-egfp</i> transgene in transgenic fish at different developmental stages.

<p>Endogenous <i>dnd</i> or exogenous <i>ntr-egfp</i> transcript was detected using RT-PCR. A) endogenous <i>dnd</i> (a) or exogenous <i>ntr-egfp</i> (b) transcript detected in the fish body at different developmental stages. B) Endogenous <i>dnd</i> (middle) or exogenous <i>ntr-egfp</i> (bottom) transcript detected in various tissues from adult fish at 120 dpf. Transcripts of <i>β-actin</i> were amplified from the same samples as an internal control to test the quality of the cDNA template.</p

The sufficient number of early germ cells required for the female fate sustain in zebrafish.

<p>The <i>dnd^-3’UTR</i>:NTR-EGFP transgenic juvenile siblings were treated with 0.2% DMSO solution from 18 dpf to 39 dpf (con), or 5 mM MTZ/0.2% DMSO solution from 18 dpf to 39 dpf (3-week treatment group), from 25 dpf to 39 dpf (2-week treatment group), and from 32 dpf to 39 dpf stages (1-week treatment group). Total RNA of 5 fish were collected at 39 dpf from each groups. A) relative <i>dnd</i> expression levels via quantitative real-time PCR in fish from each groups; B) numbers of the male and female of the rest fish in each groups at their 70 dpf stage. The letters a, b, c, represent the statistically significant difference among groups (<i>p<0.001</i>, student T-test). The results represent 3 independent lines.</p

Generation of the transgenic zebrafish with the NTR-EGFP expression under the control of zebrafish <i>dnd</i> promoter.

<p>A) genomic structure of zebrafish dnd gene, including 5’UTR region, 4 exons and 3’ UTR region identified for its PGC-specific presence in the fourth exon. The positions for the region in zebrafish DNA sequence BX890575.23 are labeled in blue. The position sites for the region used related to the transcriptional starting site of <i>dnd</i> are labeled in black. B) schematic representation of the transgenic construct containing the 5’-<i>dnd</i>:<i>ntr-egfp-3’UTR of dnd-</i>3’ fragment flanked by I-Sce1 sites. C) Schematic representation of the transgenic construct containing the 5’-<i>dnd</i>:<i>ntr-egfp</i> without <i>dnd-</i>3’ fragment flanked by I-Sce1 sites. D) Fluorescence microscopic image showing EGFP-expressing PGCs of a F0 progeny at 72 hpf. E) in situ hybridization signals <i>of vasa</i> probe showing the position of PGC at 72 dpf.</p

The absence of females developed from MTZ-treated transgenic juveniles.

<p>The <i>dnd^-3’UTR</i>:NTR-EGFP transgenic or wild-type sibling control juveniles at 18 dpf were treated with 5 mM MTZ/2% DMSO or 2% DMSO solution for 20 days. The sex ratios of adult fish at 120 dpf were recorded for each of the groups after treatment. A) No female recorded in the groups from 3 independent transgenic lines, line 1 (MTZ1), line 2 (MTZ2) and line 3 (MTZ3) after MTZ-treatment. Various sex ratios of the transgenic fish after DMSO-treatment as the controls were recorded. B) Various sex ratios recorded in the groups of wild-type zebrafish after MTZ-treatments for different periods, 10-day (MTZ1), 20-day (MTZ2), 25-day (MTZ3), or DMSO-treatment for 25 days. The total numbers of fish were labeled under each group.</p

Induced cell death in transition gonads of the <i>dnd</i>:NTR-EGFP transgenic fish via MTZ treatments.

<p>The MTZ-induced cell death were evaluated by an <i>in situ</i> cell death assay in the transition gonads of the <i>dnd</i>:NTR-EGFP transgenic fish at 26 dpf stage after 1 week MTZ treatment. Transgenic fish at 18 dpf were treated with 5 mM MTZ/0.2% DMSO or 0.2% DMSO solution for 1 week. The fish were cryosectioned at 6μm for <i>in situ</i> TUNEL assay. A-D) transition gonad after MTZ treatments with apoptosis signals under fluorescent microscope (red fluorescence, A), merge images under fluorescent microscope and white light microscope (B), DAPI staining (C), HE staining (D); E-H) transition gonad in control groups with apoptosis signals under fluorescent microscope (red fluorescence, E), merge images under fluorescent microscope and white light microscope (F), DAPI staining (G), HE staining (H); The white frame indicates the gonad position.</p

Several transgenic zebrafish for germ cell visualization <i>in vivo</i>.

<p>Several transgenic zebrafish for germ cell visualization <i>in vivo</i>.</p