Social enterprises and local government: a scoping study

ACELG has released a new scoping study that explores the relationship between social enterprises and local governments. Entitled Social Enterprises and Local Government: A Scoping Study the paper outlines current knowledge about local governments in Australia and overseas working with social enterprises to achieve collaborative place-based solutions to current challenges facing communities. The research reviews relevant literature in Australia, the US, Canada, the UK and Europe, and finds that very few studies address the actual or potential relationship between local government and social enterprise. This and other conclusions from the research demonstrate that the social enterprise-local government interaction has great potential and needs to be explored more thoroughly. The report was prepared by Dr Robyn Eversole and Mary Duniam from the University of Tasmania’s Institute for Regional Development as an ACELG Partnership Research Scheme Project

Off-design performance of the supercritical carbon dioxide recompression Brayton cycle with NDDCT cooling for concentrating solar power

The aim of this study is to investigate the off-design performance of an air-cooled supercritical carbon dioxide recompression Brayton cycle for concentrating solar thermal power generation. Off-design component models were developed in a system modelling framework. The components were designed for 25 MWe net power generation at ambient temperature 30 °C, with design point cycle thermal efficiency of 46.2%. The off-design performance was investigated for a range of heat source temperatures, ambient temperatures and cycle mass flow rates. Key elements of the off-design control scheme used are independent compressor shaft speeds, fixed low side pressure (assuming inventory control), and fixed turbine speed (for synchronous operation). The cycle can maintain nominal net power generation at 50 °C ambient temperature with increased cycle mass flow rate and turbine inlet temperature. At design point turbine inlet temperature and mass flow rate, net power generation decreases by approximately 10% for each 10 °C increase above the design point ambient temperature. The high design point ambient temperature limits the beneficial effect low ambient temperature. The effect of decreasing the design point ambient temperature was investigated. While this allows higher peak cycle efficiency, it also leads to much greater deterioration of cycle efficiency with increasing ambient temperature

Annual performance variation of an EGS power plant using an ORC with NDDCT cooling

The purpose of this paper is to model an Enhanced Geothermal System (EGS) power plant using an Organic Rankine Cycle (ORC) cooled by a Natural Draft Dry Cooling Tower (NDDCT) and to investigate the influence of the variation of performance of the NDDCT due to changing ambient temperature on cycle performance. The ORC used in this work is the supercritical butene recuperated ORC. The EGS heat source conditions used are those found at the Habanero 1 MW pilot plant in South Australia, with geothermal brine inlet temperature of 220 °C, minimum brine temperature of 80 °C, and brine mass flow rate of 35 kg/s. A one dimensional NDDCT model was developed and integrated into the cycle model, enabling a novel method of coupled analysis of ORC and NDDCT interdependence, which allows analysis of plant performance for varying ambient temperature. The analysis finds that annual average W is 2.82 MWe, the typical daily range of W is 0.62 MWe (±11%), the typical change in W for consecutive days is 0.07 MWe (3%), and the largest is 0.5 MWe (20%). The maximum range at any given time throughout the year, based on historical temperature data extremes is ±31%, but the typical expected range ±10%

LG-Social-Enterprises-Scoping-Study.pdf

This scoping study explores the relationship between social enterprises and local governments with a particular focus on the Australian experience. The paper outlines current knowledge about local governments in Australia and overseas working with social enterprises to achieve collaborative place-based solutions to current challenges facing communities

Comparison of direct and indirect natural draft dry cooling tower cooling of the sCO2 Brayton cycle for concentrated solar power plants

This study investigates the performance of direct and indirect cooling in conjunction with natural draft dry cooling towers (NDDCT) for the heat rejection of a supercritical carbon dioxide (sCO) recompression Brayton cycle. One dimensional models were developed for direct and indirect cooling NDDCTs. The inlet conditions to the heat rejection system that correspond to the peak cycle efficiency for the scenario considered were identified and used to determine the minimum NDDCT size for direct and indirect cooling. The direct cooling configuration requires a smaller tower than indirect cooling, due to the much higher temperature difference between the two fluid streams. When analysed in isolation the direct cooling NDDCT is found to over cool at both high and low inlet temperatures. The direct and indirect dry cooled recompression cycles were analysed at a range of ambient temperatures, using a coupled NDDCT and cycle model approach, in order to represent daily and annual variances. In both direct and indirect configurations, the cycle is overcooled at low ambient temperature, reducing cycle efficiency. A novel bypass arrangement was proposed that allows control of the compressor inlet temperature by reducing heat rejection from the tower, and allows both cycles to maintain peak efficiency at low ambient temperatures. At the design point ambient temperature of 20 °C the cycle efficiency is 49.6%. This is maintained down to 0 °C for both configurations, and drops to 44.7% and 43.8% at 50 °C ambient for direct and indirect respectively

Measurements of crosswind influence on a natural draft dry cooling tower for a solar thermal power plant

Crosswind is a significant concern for natural draft dry cooling towers. The concern is more serious for shorter towers. Therefore, the crosswind influence is a significant threat to the use of natural draft dry cooling towers in concentrating solar thermal power plants, which are generally built at sizes smaller than conventional fossil-fired plants and employ relatively shorter towers. While some numerical studies and small lab-scale test reports exist, very few full scale experimental studies have been reported for conventional cooling towers and none for relatively short cooling towers suitable for renewable thermal power plants. To address this gap, a 20-m tall fully instrumented natural draft dry cooling tower was built by the University of Queensland. The tower was designed to serve a future 1-MWe concentrating solar thermal plant on the same site. Its performance was tested under different ambient temperatures and crosswind speeds. The detailed experimental data of the crosswind condition, air temperature distribution inside and outside of the cooling tower and the cooling performance are presented. The experimental data demonstrate the substantial yet complex impact of the crosswind on cooling tower performance. Significant non-uniformities in air and hot water temperature distributions and strong air vortices inside the tower were observed in high crosswind speeds. Unlike tall cooling towers used in large conventional plants, the cooling tower performance does not monotonously decrease with the increase of the crosswind speed. In fact, after the tower performance drops to its lowest level at a wind speed around 5 m/s, the trend is reversed and further increases in the crosswind speed help the tower performance. Analysis shows that this reversal occurs because the tower heat transfer mechanism changes. As crosswind rises above the critical speed, the airflow inside the cooling tower becomes increasingly controlled by the crosswind instead of the natural draft