Experimental and numerical study of a PCM solar air heat exchanger and its ventilation preheating effectiveness

This article presents a PCM solar air heat exchanger integrated into ventilated window developed to maximize the use of the solar energy to pre-heat the ventilated air. The system is designed to improve the indoor air quality and thermal comfort by continuous pre-heated air supply at a reduced energy use through the capturing and storing of solar energy. This study examines the thermodynamic behavior of the system both experimentally and numerically. This entails a full-scale experiment in climate boxes to study the thermal storage and heat release ability of the facility. Accordingly, a numerical model combining heat transfer and buoyancy derived laminar flow and nonlinear thermal properties of the PCM is built and validated with the experimental data. The model is then used for configuration optimization of the PCM solar air heat exchanger to maximize the solar energy storage and the ventilation pre-heating effectiveness. The results show that for a 6-h solar charging period, the optimum PCM plate depth is 90 mm and the optimum air gap thickness is 6 mm. The same configuration can be used for both summer night cooling and winter solar energy storage applications. The total stored/released latent heat after one charging period is 93.31 MJ/m3.</p

Peningkatan Hasil Belajar Siswa pada Pembelajaran Matematika Tentang Penjumlahan dengan Media Kartu Bergambar

: The problem of this research is one how the improvement of teacher`s ability in mathematics learning about addition of the number with flash card to students learning result in grade one B of Sekolah Dasar Negeri 05 Kendawangan Kabupaten Ketapang?, two how the improvement of teachers ability to do mathematics learning about addition of the number with flash card to students learning result in grade one B of Sekolah Dasar Negeri 05 Kendawangan Kabupaten Ketapang?, three how much the improvement of students learning result on mathematics learning of the number with flash card to students learning result in grade one B of Sekolah Dasar Negeri 05 Kendawangan Kabupaten Ketapang. The purposes of this research are: a. to know the improvement of teacher`s ability to student learning result in grade one B for the first semester at Sekolah Dasar Negeri 05 Kendawangan Kabupaten Ketapang regency on mathematics learning, b. To know the improvement of teacher`s ability in planning of mathematics learning about addition of the number with flash card to student learning result in grade one B at Sekolah Dasar Negeri 05 Kendawangan Kabupaten Ketapang, c. To know the improvement of student learning result on mathematics learning about addition of the number with flash card in grade one B at Sekolah Dasar Negeri 05 Kendawangan Kabupaten Ketapang. This research uses a descriptive form of classroom action, and the nature of the research using collaboration the procedure described action research, namely planning, implementation, observation, reflection. The subjects of this research is in grade one students. The result of research on student learning result in the first cycle average about 69,09 and the second cycle increase by 80,45

Data-Driven Key Performance Indicators and Datasets for Building Energy Flexibility: A Review and Perspectives

Energy flexibility, through short-term demand-side management (DSM) and energy storage technologies, is now seen as a major key to balancing the fluctuating supply in different energy grids with the energy demand of buildings. This is especially important when considering the intermittent nature of ever-growing renewable energy production, as well as the increasing dynamics of electricity demand in buildings. This paper provides a holistic review of (1) data-driven energy flexibility key performance indicators (KPIs) for buildings in the operational phase and (2) open datasets that can be used for testing energy flexibility KPIs. The review identifies a total of 81 data-driven KPIs from 91 recent publications. These KPIs were categorized and analyzed according to their type, complexity, scope, key stakeholders, data requirement, baseline requirement, resolution, and popularity. Moreover, 330 building datasets were collected and evaluated. Of those, 16 were deemed adequate to feature building performing demand response or building-to-grid (B2G) services. The DSM strategy, building scope, grid type, control strategy, needed data features, and usability of these selected 16 datasets were analyzed. This review reveals future opportunities to address limitations in the existing literature: (1) developing new data-driven methodologies to specifically evaluate different energy flexibility strategies and B2G services of existing buildings; (2) developing baseline-free KPIs that could be calculated from easily accessible building sensors and meter data; (3) devoting non-engineering efforts to promote building energy flexibility, such as designing utility programs, standardizing energy flexibility quantification and verification processes; and (4) curating datasets with proper description for energy flexibility assessments.Comment: 30 pages, 14 figures, 4 table

Sustainable and energy-efficient domestic hot water systems:A review

For a very long time activities related to efficient domestic hot water (DHW) production and distribution have been neglected and left behind due to an insignificant share in total energy use for buildings. It is in recent years that DHW has emerged as one of the key energy factors in the total energy use in buildings and its share is continuously increasing as energy use in other segments is continuously decreasing, for example space heating, ventilation, and energy for lighting. It becomes suddenly undeniable that efforts in the field of energy-efficient DHW must be strengthened, and as such, there is increased activity in the field. However, the work reported is very dispersed and fragmented. The objective of this review article is to collect and present recent works related to improve performance of a DHW system in terms of energy. The scope and content of the paper aims to address the topics of high relevance to the field, these are shift towards the new situation in which DHW becomes a significant energy use responsible factor in buildings, distribution and weighting of losses related to DHW sys-tems and purpose of DHW use. The article focuses on novel actions to obtain energy-efficient DHW in the following domains: DHW production, DHW distribution and circulation, wastewater heat recovery, and control strategies. The article finishes with conclusions

Validation of a new method to estimate energy use for space heating and hot water production from low-resolution heat meter data

One of the initiatives to reach the European decarbonization goal is the roll-out of smart heating meters in the building stock. However, these meters often record the total energy usage with only hourly resolution, without distinguishing between space heating (SH) and domestic hot water (DHW) production. To tackle this limitation, this paper presents the validation of a new methodology to estimate the SH and DHW from total measurements in different building types in three countries (Denmark, Switzerland, and Italy). The method employs a combined smoothing algorithm with a support vector regression (SVR) to estimate the different heating uses. The estimation results are compared with the different countries' DHW compliance calculations. The comparison showed that the compliance calculations outperformed this method by considering the validation dataset characteristics

Preliminary reduction of chromium ore using Si sludge generated in silicon wafer manufacturing process

In order to promote the recycling of by-product from Si wafer manufacturing process and to develop environment-friend and low cost process for ferrochrome alloy production, a basic study was performed on the preliminary reduction reaction between chromium ore and the Si sludge, comprised of SiC and Si particles, which is recovered from the Si wafer manufacturing process for the semiconductor and solar cell industries. Pellets were first made by mixing chromium ore, Si sludge, and some binders in the designed mixing ratios and were then treated at different temperatures in the 1116°C–1388°C range in an ambient atmosphere. Cordierite and SiO2 were confirmed to be formed in the products after the reduction. Additionally, metal particles were observed in the product with Fe, Cr, and Si components. It is found that temperatures above 1300°C are necessary for the reduction of the chromium ore by the Si sludge. The reduction ratio for Fe was evaluated quantitatively for our experimental conditions, and the proper mixing ratio was suggested for the pre-reduction of the chromium ore by the Si sludge. This study provides basic information for the production of ferrochrome alloys on the pre-reduction of chromium ore using Si sludge