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Although hydrothermal carbonization of biomass components is known to be mainly governed by reaction temperature, consistent reports on the effect and statistical significance of process conditions on hydrochar properties are still lacking. The objective of this research was to determine the importance and significance of reaction temperature, retention time and solid load on the properties of hydrochar produced from an industrial lignocellulosic sludge residue. According to the results, reaction temperature and retention time had a statistically significant effect on hydrochar ash content, solid yield, carbon content, O/C-ratio, energy densification and energy yield as reactor solid load was statistically insignificant for all acquired models within the design range. Although statistically significant, the effect of retention time was 3-7 times lower than that of reaction temperature. Predicted dry ash-free solid yields of attained hydrochar decreased to approximately 40% due to the dissolution of biomass components at higher reaction temperatures, as respective oxygen contents were comparable to subbituminous coal. Significant increases in the carbon contents of hydrochar led to predicted energy densification ratios of 1-1.5 with respective energy yields of 60-100%. Estimated theoretical energy requirements of carbonization were dependent on the literature method used and mainly controlled by reaction temperature and reactor solid load. The attained results enable future prediction of hydrochar properties from this feedstock and help to understand the effect of process conditions on hydrothermal treatment of lignocellulosic biomass.

Thermophilic co-digestion of sewage sludge with three different doses of trapped grease waste (GW) from the pre-treatment of a WWTP has been assessed in a CSTR bench-scale reactor. After adding 12% and 27% of grease waste (on COD basis), the organic loading rate increased from 2.2 to 2.3 and 2.8 kgCOD m-3 d-1 respectively, and the methane yield increased 1.2 and 2.2 times. Further GW increase (37% on COD basis) resulted in an unstable methane yield and in long chain fatty acids (LCFA) accumulation. Although this inestability, the presence of volatile fatty acids in the effluent was negligible, showing good adaptation to fats of the thermophilic biomass. Nevertheless, the presence of LCFA in the effluent worsens its dewatering properties. Specific methanogenic activity tests showed that the addition of grease waste ameliorates the acetoclastic activity in detriment of the hydrogenotrophic activity, and suggests that the tolerance to LCFA can be further enhanced by slowly increasing the addition of lipidrich materials.

Abstract A simple, transient model for the characterization of the dynamic thermal performance of solar thermal collectors was developed and experimentally validated. The proposed model equation is linear with respect to the input parameters and does not require any treatment for ordinary differential equations (ODEs). The temperature distribution in the fluid flowing inside the collector is described by means of the piston flow and finite increment concepts. The dynamic effect, for a given flow rate, is expressed by the heat transport time and is based on the effective thermal capacity of the collector. The results reveal that the characteristic parameters involved in the model agree reasonably well with the experimental variables obtained from standard steady-state measurements. After a calibration process the model can well predict the thermal performance of a solar thermal collector, for a specific weather data set.

Artículos en revistas Energy, and particularly electricity, has played and will continue to play a very important role in the development of human society. Electricity, which is the most flexible and manageable energy form, is currently used in a variety of activities and applications. For instance, electricity is used for heating, cooling, lighting, and for operating electronic appliances and electric vehicles. Nowadays, given the rapid development and commercialization of technologies and devices that rely on electricity, electricity demand is increasing faster than overall primary energy supply. Consequently, the design and planning of power systems is becoming a progressively more important issue in order to provide affordable, reliable and sustainable energy in timely fashion, not only in developed countries but particularly in developing economies where electricity demand is increasing even faster. Power systems are networks of electrical devices, such as power plants, transformers, and transmission lines, used to produce, transmit, and supply electricity. The design and planning of such systems require the selection of generation technologies, along with the capacity, location, and timing of generation and transmission capacity expansions to meet electricity demand over a long-term horizon. This manuscript presents a comprehensive optimization framework for the design and planning of interconnected power systems, including the integration of generation and transmission capacity expansion planning. The proposed framework also considers renewable energies, carbon capture and sequestration (CCS) technologies, demand-side management (DSM), as well as reserve and CO2 emission constraints. The novelty of this framework relies on an integrated assessment of the aforementioned features, which can reveal possible interactions and synergies within the power system. Moreover, the capabilities of the proposed framework are demonstrated using a suite of case studies inspired by a real-world power system, including business as usual and CO2 mitigation policy scenarios. These case studies illustrated the adaptability and effectiveness of the framework at dealing with typical situations that can arise in designing and planning power systems. info:eu-repo/semantics/publishedVersion

The transformation of electricity network users from passive to active agents, as a result of decreasing costs of distributed energy resources, requires several adaptions, one of which is revising the distribution network charges. Often current network charge designs do not ensure network cost recovery and lack to incentivize efficient network investments and usage. New network charge methodologies are required to guide and incentivize customers in an efficient way while maximizing system economic efficiency. This paper proposes an efficient methodology that ensures network cost recovery while promoting efficient usage of the network as well as efficient network investments. The proposed network charge design consisting of two components: a peak coincidence network charge (PCNC) and fixed charge. The PCNC is a forward-looking charge as it considers the cost of future network reinforcements required and assigned to consumers during peak hours of the network utilization. Fixed charges allocate the residual of the network costs following Ramsey-pricing principles. This paper compares the outcome from economic optimum customers response to four different network charges: (i) volumetric charges (ii) fixed charges (iii) peak demand charge (iv) fixed charges + PCNC. Two case studies for two different load profiles are simulated using linear programming on Matlab to minimize their total costs within each charges design, considering the possibility of buying electricity from the grid and investing on onsite generation or curtail load. Finally, the paper highlights through the case studies how customer s response is highly influenced by different network charge designs, and compare the consequences of these responses in terms of network cost recovery and total system costs. The paper concludes with practical issues that need to be considered for the implementation of the proposed network charges design. info:eu-repo/semantics/draft

Abstract In order to optimize battery performance, different geometries have been evaluated taking into account their suitability for different applications. These different geometries include conventional, interdigitated batteries and unconventional geometries such as horseshoe, spiral, ring, antenna and gear batteries. The geometry optimization was performed by the finite element method, applying the Doyle/Fuller/Newman model. At 330 C, the capacity values for conventional, ring, spiral, horseshoe, gear and interdigitated geometries are 0.58 A h m −2 , 149 A h m −2 , 182 A h m −2 , 216 A h m −2 , 289 A h m −2 and 318 A h m −2 , respectively. The delivered capacity depends on geometrical parameters such as maximum distance for the ions to move to the current collector, d _max, distance between of current collectors, d _cc, as well as the thickness of separator and electrodes, allowing to tailor battery performance and geometry for specific applications.

The objective of this paper is to propose a novel methodology to compute the benefit obtained by individual users from each of the transmission expansion projects within an expansion plan. Benefits computed should be coherent with the technical and economic principles that underlie the development of the expansion plan. Thus, this methodology is based on the idea that the benefits produced by each project of a plan should be determined considering all projects jointly, instead of individually. Some benefits obtained by users from projects evolve continuously with the deployment of the expansion plan, while others are discrete, since they occur at certain points of the deployment of this plan. A separate Aumann-Shapley game is solved to allocate continuous benefits, and each discrete one. In the second case, the standard Aumann-Shapley algorithm for the allocation of benefits is modified to cope with the fact that the function of each user s benefits is not continuous with the size of projects deployed. A 9-Bus case study is used to compare the methodology proposed with existing ones. The results show that the methodology proposed is able to overcome problems detected in other methodologies, providing more accurate and sound results. The good properties of the methodology proposed make it applicable to problems related to network expansion regulation, such as the cost allocation of new investments. Although the methodology proposed is particularized to electric power systems, its concept and fundamentals can also be applied in other energy sectors, such as gas. info:eu-repo/semantics/draft

Artículos en revistas The goal of this paper is to assess the sustainability of electricity production from winter cereals grown in one of the most important Spanish agricultural areas, Castilla y León Region, situated in central-northern Spain. This study analyses greenhouse gases (GHG) emissions and energy balances of electricity production in a 25 MWe power plant that was powered using straw biomass from three annual winter cereals (rye, triticale and oat) grown as dedicated energy crops. The results of these analyses were compared with those of electricity produced from natural gas in Spanish power plants. Assessments were performed using a wide range of scenarios, mainly based on the biomass yield variability obtained in demonstration plots of twelve different winter cereal genotypes. Demonstration plots were established in two different locations (provinces of Soria and León) of the Castilla y León Region during two crop seasons (2009/2010 and 2010/2011) using common management practices and input rates for rain-fed agriculture in these regions. Our results suggest that production of electricity from winter cereals biomass combustion yielded considerable reductions in terms of GHG emissions when compared to electricity from natural gas. Nevertheless, the results show that low biomass yields that are relatively frequent for Spanish farmers on low productivity lands may produce no significant reductions in GHG in comparison with electricity from natural gas. Consequently, the agronomic management of winter cereals should be re-examined in order to find potential improvements that achieve better energy balances and greater reductions in GHG emissions on land which is relatively uncompetitive in terms of crop yields and on existing low productivity scenarios. info:eu-repo/semantics/publishedVersion