Zarrouk S.J.,University of Auckland |
Woodhurst B.C.,University of Auckland |
Morris C.,Station Energy
Geothermics | Year: 2014
Scaling (fouling) has a dramatic impact on the long term operational performance of geothermal heat exchangers. Scaling affects both the flow hydrodynamics and the heat transfer resistance. A review of reported scaling problems in geothermal heat exchangers shows that silicate (pure silica and metal silicate) is the main deposited mineral. Scanning electron microscope images show that: silica deposition at the Wairakei binary plant is very dense as result of molecular (monomeric) deposition. This work attempts to characterize this impact on the binary plant, using long term production data. The geothermal brine flow rate and pressure drop within the plant are useful to assess the plant performance. These are interdependent quantities hence taken alone do not allow a proper understanding of the impact of silica scaling on performance. A new simple model was proposed to quantify the performance impact (resistance) of scaling. The available chemistry data showed that the recent (late 2009) increase in scaling rate and flow resistance is mainly related to the introduction of new wells with high silica content to the production system. Recommendations were given to maintain silica saturation index to less than two and use scaling inhibitors. © 2014 Elsevier Ltd.
Crettanand N.,Station Energy
International Water Power and Dam Construction | Year: 2012
The potential for small storage and pumped storage plants in Switzerland for flexible electricity production is evaluated. In Switzerland, SHP (small hydropower) is defined by an installed capacity of up to 10MW. SHP produced 37700Wh and covered 5.7% of the Swiss electricity production. The technical potential was evaluated by looking primarily at existing and already planned reservoirs to reduce environmental opposition and investment costs. The Canton of Valais was chosen as the unit of evaluation as it has still considerable potential for SHP based on the newly feed-in-remuneration (FIR) projects. The institutional feasibility was studied mainly by looking at the possible remuneration instruments. The results were extrapolated for the whole country based on different criteria and the rule of proportion. The study shows that the technical potential of storage schemes lies mainly with plants on streams. With the introduction of the FIR, the number of such plants will continue to increase and thus offer opportunities for storage applications as well.
Iungo G.V.,Station Energy |
Porte-Agel F.,Station Energy
Journal of Physics: Conference Series | Year: 2014
Aerodynamic optimization of wind farm layout is a crucial task to reduce wake effects on downstream wind turbines, thus to maximize wind power harvesting. However, downstream evolution and recovery of wind turbine wakes are strongly affected by the characteristics of the incoming atmospheric boundary layer (ABL) flow, such as wind shear and turbulence intensity, which are in turn affected by the ABL thermal stability. In order to characterize the downstream evolution of wakes produced by full-scale wind turbines under different atmospheric conditions, wind velocity measurements were performed with three wind LiDARs. The volumetric scans are performed by continuously sweeping azimuthal and elevation angles of the LiDARs in order to cover a 3D volume that includes the wind turbine wake. The minimum wake velocity deficit is then evaluated as a function of the downstream location for different atmospheric conditions. It is observed that the ABL thermal stability has a significant effect on the wake evolution, and the wake recovers faster under convective conditions. © Published under licence by IOP Publishing Ltd.
Lin M.,Station Energy |
Haussener S.,Station Energy
Energy | Year: 2015
Solar-driven non-stoichiometric thermochemical redox cycling of ceria for the conversion of solar energy into fuels shows promise in achieving high solar-to-fuel efficiency. This efficiency is significantly affected by the operating conditions, e.g. redox temperatures, reduction and oxidation pressures, solar irradiation concentration, or heat recovery effectiveness. We present a thermodynamic analysis of five redox cycle designs to investigate the effects of working conditions on the fuel production. We focused on the influence of approaches to reduce the partial pressure of oxygen in the reduction step, namely by mechanical approaches (sweep gassing or vacuum pumping), chemical approaches (chemical scavenger), and combinations thereof. The results indicated that the sweep gas schemes work more efficient at non-isothermal than isothermal conditions, and efficient gas phase heat recovery and sweep gas recycling was important to ensure efficient fuel processing. The vacuum pump scheme achieved best efficiencies at isothermal conditions, and at non-isothermal conditions heat recovery was less essential. The use of oxygen scavengers combined with sweep gas and vacuum pump schemes further increased the system efficiency. The present work can be used to predict the performance of solar-driven non-stoichiometric redox cycles and further offers quantifiable guidelines for system design and operation. © 2015 Elsevier Ltd.
News Article | March 2, 2015
The wave of solar energy has hit Africa and most of the governments are looking into ensuring that the places without electricity are well fed with solar power gadgets. This being a very lucrative market the start-up industry is not left out and their share of innovations has given many African countries a boost in accessing the clean energy electricity. One of this start-up is Station Energy from Senegal. Led by Alexandre Castel, this start-up is looking into structuring an investment fund to finance solar micro-facilities. When they talk about micro-facilities they mean cold rooms, cybercafés, pumping; facilities that will be rented to rural communities. This fund will gather equal distribution of funds and classic investors to build 300 micro-facilities in 5 years. The start-up is looking at giving more than just lighting the houses of individuals. It is looking at helping the rural people access technology through the opening of cybercafés that will run on solar energy. Apart from access to technology the people in the rural areas will be able to run facilities that require electricity. This initiative will assist in modernizing Africa faster than expected. “We can build the product;our team has what it takes. Given the time and money, we can deliver on our promises,” says Castel. The start up has a very able team, consisted of 3 co-founders from technical and entrepreneurial background, cumulating 20-year experience in project management and 10 year in solar energy. They have branches in Ivory Coast and Burkina Faso