Climatological investigation for solar-power stations in the Swiss Alps

An extended measuring campaign has been performed to obtain all the relevant climatological data at a representative power plant located in the Swiss Alps, as a basis for studying the technical and economic feasibility of solar power stations in Switzerland. The data include the irradiations: direct normal, global normal, global horizontal, diffuse horizontal and global inclined at 30, 45 and 60° to the South. From the results, it is concluded that suntracking photovoltaic panels would receive 1.7 times more energy per square metre per year than solar thermal systems converting the direct normal irradiation only. Unexpectedly high global irradiation values in southwards-directed, 60° inclined planes confirmed the enhancing effect of snow reflection, leading to a valuable extra output of panels in winter. Snow and cloud-side reflection occasionally caused peak values of the global normal irradiation, far exceeding the solar constant of 1367 W/m2 (up to 2000 W/m2). The irradiation data are supplemented by wind, rainfall, ambient temperature and humidity measurements. Some solar spectra were also acquired at the end of the project. They contribute to the correct selection of the panel type. Highly resolved measurements of the direct normal irradiation were used to perform simulations of the volumetric receiver of a solar thermal power station.

Plasma-spray coated rare-earth oxides on molybdenum disilicide - High temperature stable emitters for thermophotovoltaics

Selective emitters for thermophotovoltaics consisting of intermetallic alloy MoSi2 substrate with plasma-spray coated rare-earth oxides ytterbium oxide Yb2O3, Yb-doped garnet Yb1.5Y1.5Al5O12, and erbium oxide Er2O3 have been successfully tested till 1650 °C. The emitters are fully operable in an oxygen containing atmosphere, are highly thermal shock stable, and show good selective emitting properties. Shielding the high out-of-band emittance of the MoSi2 substrate with a 4 [mu]m thick Pt intermediate layer has resulted in reduced radiation power and emittance of the rare-earth oxide film due to multiple reflections at the interfaces. The novel technique of vacuum plasma-spray coated rare-earth oxide films on MoSi2 is a promising way for the production of effective and high temperature stable selective thermophotovoltaic emitters.Thermophotovoltaics MoSi2 Rare-earth oxide Plasma-spray coating Selective emitter

High-performance selective Er-doped YAG emitters for thermophotovoltaics

Selective emitters for thermophotovoltaics have been produced by vacuum plasma-spray coating of erbium doped garnet Er1.5Y1.5Al5O12 and Er2O3 on the intermetallic alloy MoSi2. The emitters are fully operable in an oxygen-containing atmosphere at a temperature of 1600 °C, are highly thermal-shock stable, and show good selective-emitting properties. The film thickness of the rare-earth oxide was varied between 200 and 600 [mu]m and an optimal thickness for maximum selectivity was found. Measurements with Si and GaSb photocells have been performed in order to evaluate the optimal combination emitter - photocell for real thermophotovoltaic systems.78.20.-e Thermophotovoltaics MoSi2 Rare-earth oxide Er-oxide Plasma-spray coating Selective emitter GaSb photocell Si photocell

Modelling and degradation study on a copper indium diselenide module

This paper illustrates the testing of a commercially available copper indium diselenide (CIS) module under real operating conditions, and the development of a semi-empirical model. The tests were carried out under different cell temperature, solar radiation and air mass conditions. A semi-empirical efficiency model was adopted to correlate 1168 measured data sets before degradation. The data was then transformed to validate the appropriateness of the model. Identical tests were repeated after one year's exposure to sunlight. The effect on the efficiency model was then investigated. In particular the change in STC efficiency and temperature coefficient will be discussed as an example of application of the efficiency model. Following detailed analysis of the results, it is suggested that the PV industry broadens disclosure of module parameters in future technical data published

Efficiency and Annual Output of a Monocrystalline Photovoltaic Module under Actual Operating Conditions

This work covers extensive outdoor testing of a mc-Si module from Jumao Photonics (JM-050W-S4-G). All tests were performed at PSI’s Solar Test Facility. The location of PSI represents a typical site in the Swiss Midland. The module was fixed on a sun tracker and tested under clear sky conditions as well as under a cloudy sky. During testing, the global-normal irradiance varied between 56 and 1087 W/m2, the cell temperature between 9 and 67°C, and the relative air mass between 1.1 and 9.6. About 2000 current/voltage characteristics were automatically acquired, leading to the efficiency as a function of irradiance, cell temperature and air mass. The data were used to develop a new efficiency model to calculate the efficiency under all relevant operating conditions. The model contains six parameters. They were determined by applying non-linear fitting techniques. Applying mathematical transformations reported on earlier, measurements and the efficiency model can be compared and validated in two-dimensional representations. The module shows a modest efficiency behavior over the irradiance range (bad part-load efficiency). The STC efficiency (referred to the active cell area) was found to be 12.6%, corresponding to an STC module output power of 45.5 W (manufacturer: 50 W). An efficiency maximum of 12.7% was found at 832 W/m2. The efficiency linearly decreases with temperature. Its temperature coefficient was found to be –0.0507 percentage points/°C. Regarding the impact of air mass, the efficiency exhibits a maximum value of 12.7% at an air mass of 3.77. The module shows fairly good red light sensitivity in the late afternoon.link_to_subscribed_fulltex

Methane emission from a Swiss lake: A full year cycle

International audienceThe build-up of methane has been monitored occasionally over three years and monthly during a full yearís cycle in Lake Rotsee (Lucerne, Switzerland). Concentrations and carbon isotopic composition of methane has been used to describe the sources and losses of methane in the water column. High methane concentrations (up to 1mM) were measured in fall (over several years) in the anoxic water layer. Aerobic and anaerobic methane oxidation in the water column later in the year could be shown. Methane oxidation rates were highest in the interface between oxic and anoxic water layers around 8- 10 m depth. The profile of carbon isotopic composition of methane showed strong indications for methane oxidation at the same depth. Anaerobic methane oxidizers ANME-1 and ANME-2 and aerobic methane oxidizing bacteria (MOB) were detected using FISH at the interface. Trying to sequence the responsible organisms, however, was only successful for the aerobic methanotrophs detecting Methylomonas and Methylobacter. A search for mcrA, the gene for anaerobic methane oxidation, will reveal whether this process is really occurring. An estimation of methane emissions to the atmosphere during stratification showed an average flux of 6.7 mg/m2/d. However, during lake turnover in October to December direct eddy covariance flux measurements above the lake surface showed a higher emission of 16 mg/m2/d