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The widespread use of optimization methods in the design phase of District Heating Networks is currently limited by the availability of scalable optimization approaches that accurately represent the network. In this paper, we compare and benchmark two different approaches to non-linear topology optimization of District Heating Networks in terms of computational cost and optimality gap. The first approach solves a mixed-integer non-linear optimization problem that resolves the binary constraints of pipe routing choices using a combinatorial optimization approach. The second approach solves a relaxed optimization problem using an adjoint optimization approach, and enforces a discrete network topology through penalization. Our benchmark shows that the relaxed penalized problem has a polynomial computational cost scaling, while the combinatorial solution scales exponentially, making it intractable for practical-sized networks. We also evaluate the optimality gap between the two approaches on two different District Heating Network optimization cases. We find that the mixed-integer approach outperforms the adjoint approach on a single-producer case, but the relaxed penalized problem is superior on a multi-producer case. Based on this study, we discuss the importance of initialization strategies for solving the optimal topology and design problem of District Heating Networks as a non-linear optimization problem.

Abstract Using country level panel data from East Asia over the period 1998–2011, this paper examines the implications of international production fragmentation-induced intermediate goods trade on the link between energy consumption and carbon pollution. The paper focuses on the interaction effect between energy consumption and trade in intermediate goods on carbon emission. The empirical results presented suggest that international trade in intermediate goods decreases the positive impact on carbon emission of energy consumption. When compared with the trade in final goods, intermediate goods trade contributes to a greater decrease in carbon pollution resulting from energy consumption. These results confirm that the link between energy consumption and carbon pollution in East Asia is significantly affected by international production fragmentation-induced trade in intermediate goods. The results presented in this paper have some important policy implications.

The energy consumption of a data center and hence the carbon footprint from it largely depends on the energy consumption by its active Physical Machines (PMs). Researchers have taken many attempts to minimize the data center energy consumption through the Virtual Machines (VMs) allocation into a minimal number of PMs of homogeneous types. However, the current VM placement strategies do not consider useful information that can be extracted from data logs of data center. This paper presents profile-based VM placement approach to improve energy efficiency of data centers. The approach formulates the energy consumption problem as a profile-based optimization problem. Then, the problem decomposed into multiple smaller ones in a number of intervals. For each intervals, a number VMs and PMs are sorted in terms of resource requirements and energy efficiency respectively. Then, the First Fit-Decreasing(FFD) is adopted to place the sorted VMs to the sorted PMs. Experiments conducted to demonstrate the presented approach with comparisons with the original FFD algorithm. The experimental results have shown that the presented approach can reduce more energy consumption than the original FFD algorithm and is scalable for larger test problems.

Electric water heaters have the ability to store energy in their water buffer without impacting the comfort of the end user. This feature makes them a prime candidate for residential demand response. However, the stochastic and nonlinear dynamics of electric water heaters, makes it challenging to harness their flexibility. Driven by this challenge, this paper formulates the underlying sequential decision-making problem as a Markov decision process and uses techniques from reinforcement learning. Specifically, we apply an auto-encoder network to find a compact feature representation of the sensor measurements, which helps to mitigate the curse of dimensionality. A wellknown batch reinforcement learning technique, fitted Q-iteration, is used to find a control policy, given this feature representation. In a simulation-based experiment using an electric water heater with 50 temperature sensors, the proposed method was able to achieve good policies much faster than when using the full state information. In a lab experiment, we apply fitted Q-iteration to an electric water heater with eight temperature sensors. Further reducing the state vector did not improve the results of fitted Q-iteration. The results of the lab experiment, spanning 40 days, indicate that compared to a thermostat controller, the presented approach was able to reduce the total cost of energy consumption of the electric water heater by 15%. Submitted to IEEE transaction on smart grid

Due to their superior environmental stability, utilization of low‐dimensional perovskites in organometal halide solar cells (OMHSCs) has seen a sharp increase. Herein, a method to form 1D pyrrolidinium lead iodide (PyPbI3) in situ atop photoactive 3D methylammonium lead iodide (MAPbI3) using pyrrolidine posttreatment is reported. As compared with 3D MAPbI3, 1D PyPbI3 has a wider bandgap and is more environmentally stable, and it serves as a tunneling contact to mitigate charge carrier recombination and as a robust barrier against environmental degradation when incorporated into OMHSCs. Accordingly, power conversion efficiencies of the resulting MAPbI3 devices are enhanced from an average of 14.86% ± 0.65% to 15.9% ± 0.58% and their shelf‐life stability is significantly prolonged.

Abstract Fuel cell technology has undergone extensive research and development in the past 20 years. Even though it has not yet made a commercial breakthrough, it is still seen as a promising enabling technology for emissions reduction. The high electrical efficiency (Powell et al., 2012, “Demonstration of a Highly Efficient Solid Oxide Fuel Cell Power System Using Adiabatic Steam Reforming and Anode Gas Recirculation,” J. Power Sources, 205, pp. 377–384; Föger and Payne, 2014, “Ceramic Fuel Cells BlueGen—Market Introduction Experience,” 11th European SOFC & SOE Forum 2014, Lucerne, Switzerland, Paper No. A0503; and Payne et al., 2009, “Generating Electricity at 60% Electrical Efficiency From 1-2 kWe SOFC Products,” ECS Trans., 25(2), pp. 231–240) of an solid oxide fuel cell (SOFC)-based fuel cell system and the ability to operate on renewable fuels make it an ideal platform for transition from fossil-fuel dependency to a sustainable world relying on renewable energy, by reducing emissions during the transition period where fossil fuels including natural gas remain a major source of energy. Key technical hurdles to commercialization are cost, life, and reliability. Despite significant advances in all areas of the technology cost and durability targets (Papageorgopoulos, 2012, “Fuel Cells, 2012 Annual Merit Review and Peer Evaluation Meeting,” U.S. Department of Energy, Washington, DC, accessed May 14, 2012, http://www.hydrogen.energy.gov/pdfs/review12/fc_plenary_papageorgopoulos_2012_o.pdf) have not been met. The major contribution to cost comes from tailor-made balance of plant (BoP) components as SOFC-based systems cannot be optimized functionally with off-the shelf commercial items, and cost targets for BoP and stack cannot be met without volume manufacturing (Föger, 2008, “Materials Basics for Fuel Cells,” Materials for Fuel Cells, M. Gasik ed., Woodhead Publishing, Cambridge, UK, pp. 6–63). Reliability issues range from stack degradation and mechanical failure and BoP component failure to grid-interface issues in a grid-connected distributed generation system. Resolving some of these issues are a key to the commercial viability of SOFC-based microcombined heat and power (CHP) systems. This paper highlights some of the technical and practical challenges facing developers of SOFC-based products.

The restructured market for electricity in the UK has experienced a systematic pattern of price spikes associated with the use of market power by the two dominant generators. Partly in response to this problem, the share of capacity owned by any individual generator after restructuring was limited in Victoria, Australia. As a result, a much more competitive market resulted with prices substantially lower than they were under regulation. Nevertheless, an erratic pattern of price spikes exists and the price volatility is a potential problem for customers. This paper argues that the use of a uniform price auction for electricity markets exacerbates price volatility. A discriminatory price auction is proposed as a better alternative that would reduce the responsiveness of price to errors in forecasting total load.

Phosphorus (P) deficiency in some plant species triggers the release of organic anions such as citrate and malate from roots. These anions are widely suggested to enhance the availability of phosphate for plant uptake by mobilizing sparingly‐soluble forms in the soil. Carazinho is an old wheat (Triticum aestivum) cultivar from Brazil, which secretes citrate constitutively from its root apices, and here we show that it also produces relatively more biomass on soils with low P availability than two recent Australian cultivars that lack citrate efflux. To test whether citrate efflux explains this phenotype, we generated two sets of near‐isogenic lines that differ in citrate efflux and compared their biomass production in different soil types and with different P treatments in glasshouse experiments and field trials. Citrate efflux improved relative biomass production in two of six glasshouse trials but only at the lowest P treatments where growth was most severely limited by P availability. Furthermore, citrate efflux provided no consistent advantage for biomass production or yield in multiple field trials. Theoretical modeling indicates that the effectiveness of citrate efflux in mobilizing soil P is greater as the volume of soil into which it diffuses increases. As efflux from these wheat plants is restricted to the root apices, the potential for citrate to mobilize sufficient P to increase shoot biomass may be limited. We conclude that Carazinho has other attributes that contribute to its comparatively good performance in low‐P soils.