Residential solar water heating - measurement and verification case studies

Abstract: South Africa is currently experiencing an electricity crisis. This, combined with the high levels of solar irradiation as well as the power utility’s need to reduce the country’s peak demand through DSM (Demand Side Management), has promoted the installation of solar water heaters (SWHs) in homes across the country. This paper presents three case studies which were M&V’d according to the IPMVP (International Performance Measurement & Verification Protocol). The methodology used does not require baseline measurements since the baseline is calculated from continuous measurements of thermal energy delivered by the newly installed SWHs and estimation of standing losses of the replaced electric water heater (EWH). This allows the homeowner to go ahead with the installation of the SWH without waiting for M&V to establish a baseline for the EWH which is being replaced. This method is preferred by homeowners and the DSM utility alike, since the installation of the SWH is not delayed by M&V. A measurement system including an electric power meter, inlet and outlet water temperature probes, ambient temperature probe, flow meter and GSM modem were developed to measure the service level and performance of the SWH. This measurement system along with a method for modelling the usage of an EWH are crucial to the M&V methodology employed. This paper describes the type of systems investigated, the M&V metering, M&V methodology, and the payback period of each system. The sensitivity of the savings with respect to EWH standing losses is investigated. This case study provides valuable information for those interested in studying or performing M&V on SWHs

A refined baseline methodology for large scale lighting retrofit projects

Abstract: The residential sector is one of the major consumers of energy produced in the world. According to International Energy Balances (IEA, 2013), the residential sector demand represents about a quarter of the primary energy used in the world. Therefore, most energy efficiency programmes targeting large savings on a national or regional level pay particular attention to the opportunities in the residential sector. Lighting retrofitting on a large number of sites constitutes one of the most used strategies of energy conservation in the residential sector. However, given the large number of sites involved in this type of project, conventional measurement and verification (M&V) techniques based on the audit of each site, are not cost effective. Often, a statistical assessment approach based on the audit of a limited number of sites is the methodology used to mitigate the cost and the logistical challenges associated with the project. The major challenge in projects of this nature is to accurately estimate the energy consumption of a large number of sites using the measurement performed on a sample of sites selected from the overall population. In this research, baseline methodologies used in a selected number of light retrofitting projects have been analysed and, based on the observations made during this analysis, some improvements are suggested. The proposed methodology has been tested on a number of residences located on the premises of the University of Johannesburg. This paper describes the existing baseline methodologies and presents the improvements suggested to enhance the credibility of M&V results. The key results of the experimental phase of this project are also presented in this paper

Residential solar water heating - measurement and verification case studies

Abstract: South Africa is currently experiencing an electricity crisis. This, combined with the high levels of solar irradiation as well as the power utility’s need to reduce the country’s peak demand through DSM (Demand Side Management), has promoted the installation of solar water heaters (SWHs) in homes across the country. This paper presents three case studies which were M&V’d according to the IPMVP (International Performance Measurement & Verification Protocol). The methodology used does not require baseline measurements since the baseline is calculated from continuous measurements of thermal energy delivered by the newly installed SWHs and estimation of standing losses of the replaced electric water heater (EWH). This allows the homeowner to go ahead with the installation of the SWH without waiting for M&V to establish a baseline for the EWH which is being replaced. This method is preferred by homeowners and the DSM utility alike, since the installation of the SWH is not delayed by M&V. A measurement system including an electric power meter, inlet and outlet water temperature probes, ambient temperature probe, flow meter and GSM modem were developed to measure the service level and performance of the SWH. This measurement system along with a method for modelling the usage of an EWH are crucial to the M&V methodology employed. This paper describes the type of systems investigated, the M&V metering, M&V methodology, and the payback period of each system. The sensitivity of the savings with respect to EWH standing losses is investigated. This case study provides valuable information for those interested in studying or performing M&V on SWHs

A refined baseline methodology for large scale lighting retrofit projects

Abstract: The residential sector is one of the major consumers of energy produced in the world. According to International Energy Balances (IEA, 2013), the residential sector demand represents about a quarter of the primary energy used in the world. Therefore, most energy efficiency programmes targeting large savings on a national or regional level pay particular attention to the opportunities in the residential sector. Lighting retrofitting on a large number of sites constitutes one of the most used strategies of energy conservation in the residential sector. However, given the large number of sites involved in this type of project, conventional measurement and verification (M&V) techniques based on the audit of each site, are not cost effective. Often, a statistical assessment approach based on the audit of a limited number of sites is the methodology used to mitigate the cost and the logistical challenges associated with the project. The major challenge in projects of this nature is to accurately estimate the energy consumption of a large number of sites using the measurement performed on a sample of sites selected from the overall population. In this research, baseline methodologies used in a selected number of light retrofitting projects have been analysed and, based on the observations made during this analysis, some improvements are suggested. The proposed methodology has been tested on a number of residences located on the premises of the University of Johannesburg. This paper describes the existing baseline methodologies and presents the improvements suggested to enhance the credibility of M&V results. The key results of the experimental phase of this project are also presented in this paper

Body mass index and complications following major gastrointestinal surgery: A prospective, international cohort study and meta-analysis

Aim Previous studies reported conflicting evidence on the effects of obesity on outcomes after gastrointestinal surgery. The aims of this study were to explore the relationship of obesity with major postoperative complications in an international cohort and to present a metaanalysis of all available prospective data. Methods This prospective, multicentre study included adults undergoing both elective and emergency gastrointestinal resection, reversal of stoma or formation of stoma. The primary end-point was 30-day major complications (Clavien–Dindo Grades III–V). A systematic search was undertaken for studies assessing the relationship between obesity and major complications after gastrointestinal surgery. Individual patient meta-analysis was used to analyse pooled results. Results This study included 2519 patients across 127 centres, of whom 560 (22.2%) were obese. Unadjusted major complication rates were lower in obese vs normal weight patients (13.0% vs 16.2%, respectively), but this did not reach statistical significance (P = 0.863) on multivariate analysis for patients having surgery for either malignant or benign conditions. Individual patient meta-analysis demonstrated that obese patients undergoing surgery formalignancy were at increased risk of major complications (OR 2.10, 95% CI 1.49–2.96, P < 0.001), whereas obese patients undergoing surgery for benign indications were at decreased risk (OR 0.59, 95% CI 0.46–0.75, P < 0.001) compared to normal weight patients. Conclusions In our international data, obesity was not found to be associated with major complications following gastrointestinal surgery. Meta-analysis of available prospective data made a novel finding of obesity being associated with different outcomes depending on whether patients were undergoing surgery for benign or malignant disease