The effect of wind power forecasts on balancing power pricing:case Finland

Abstract. In European electricity systems, more and more electricity is produced from renewable energy sources, and in Finland, particularly from wind power. Wind power is intermittent by nature. Most wind power is sold in day-ahead markets, where the sellers are basing their bids on weather forecasts. The intermittency of wind power is expected to shift the trading from day-ahead markets to closer to real time markets, such as intraday and balancing power market markets. This thesis studies the impact of wind power forecast errors, i.e., the surplus or deficit of the actual production compared to the forecasted volume, on the balancing power market prices in Finland. Using data from January 2017 to January 2021, we use the general additive model to study the inference between wind power surplus and the balancing power premium, defined as a difference between the price in the balancing power market and the day-ahead market, to estimate the effect. The main finding is that for up-regulation the balancing power premia respond negatively to wind surplus, and positively for down-regulation, even when controlling for other covariates. To estimate the magnitude of the effect of wind surplus, we calculated the predicted values of balancing power price premium at the 5th and 95th percentiles of wind surplus for both up- and down-regulation. For up-regulation, the predicted values based on the sample, are 30.1 €/MWh and 16.01 €/MWh. For down-regulation, the predicted values based on the sample, were -16.0 €/MWh and -12.0 €/MWh for the 5th and 95th percentiles respectively. Both the results are economically significant.Tuulivoimaennusteiden vaikutus säätösähkön hinnoitteluun : case Suomi. Tiivistelmä. Eurooppalaisissa sähköjärjestelmissä yhä suurempi osa sähköstä tuotetaan uusiutuvan energian tuotantomuodoilla. Suomessa erityisesti tuulivoiman osuus on kasvanut, ja sen odotetaan yhä kasvavan tulevina vuosina. Tuulivoiman tuotanto on luonteeltaan epäsäännöllistä. Suurin osa tuulivoimalla tuotetusta sähköstä myydään vuorokausimarkkinoilla, jolloin tuulivoiman tuottajat perustavat myyntitarjouksensa seuraavan päivän tuotantoennusteisiin. Tuulivoiman epäsäännöllisestä luonteesta johtuen päivänsisäisten markkinoiden ja säätösähkön markkinoiden odotetaan kasvattavan painoarvoaan suhteessa perinteisiin vuorokausimarkkinoihin. Tämä opinnäytetyö tarkastelee tuulivoiman ennustevirheitä, toisin sanoen tuulivoiman yli- tai alituotantoa ennusteeseen verrattuna, ja näiden virheiden vaikutusta säätösähkön markkinahintoihin Suomessa. Käytetty data on vuosilta 2017- 2021, ja vaikutusten arviointiin käytetään epälineaarista GAM-menetelmää (Generalized Additive Methods), jolla arvioidaan tuulivoiman ennustevirheen vaikutusta säätösähkön hinnan ja vuorokausimarkkinahinnan erotukseen, eli niin sanottuun säätösähkön hintapreemioon. Pääasiallinen tutkimustulos on, että ylössäädössä tuulivoiman positiivisen ennustevirheen vaste säätösähkön hintapreemioon on negatiivinen, ja alassäädössä vastaavasti positiviinen, vaikka muut kovariaatit on kontrolloitu. Tuulivoiman ennustevirheen vaikutuksen suuruuden arvioimiseksi laskettiin arvioidut säätösähkön hintapreemiot 5. ja 95. prosenttipisteille. Ylössäädön osalta hintapreemiot ovat 30,1 €/MWh ja 16,0 €/MWh. Alassäädölle preemiot ovat vastaavasti -16.0 €/MWh ja -12,0 €/MWh. Molemmat tulokset ovat taloudellisesti merkitsevi

Optimization of Tc-99m-sestamibi/I-123 subtraction SPECT/CT protocol for parathyroid scintigraphy

The purpose of this study was to optimize effective, but technically challenging Tc-99m-sestamibi/I-123 subtraction SPECT/CT protocol for parathyroid scintigraphy. An anthropomorphic parathyroid phantom was set up using a small sphere, a thyroid phantom and a thorax phantom with clinical range of activities of 1231 and Tc-99m. SPECT/CT acquisitions were performed using three collimators (Low Energy High Resolution (LEHR), Low Energy Ultra High Resolution (LEUHR) and Medium Energy Low Penetration (MELP)) and two energy window settings. Images were reconstructed with a combination of four different numbers of iterations and with or without scatter correction. Images were subjected to visual and quantitative evaluation. The effect of collimator, energy window selection and reconstruction parameters had a significant effect on visual appearance and adenoma contrast in parathyroid Tc-99m-sestamibi/I-123 subtraction SPECT/CT. Symmetrical energy windows and ultra-high resolution collimator yielded best results with some improvement with scatter correction.Peer reviewe

Coulomb blockade in one-dimensional arrays of high conductance tunnel junctions

Properties of one-dimensional (1D) arrays of low Ohmic tunnel junctions (i.e. junctions with resistances comparable to, or less than, the quantum resistance $R_{\rm q}\equiv h/e^2\approx 25.8$ k$\Omega$) have been studied experimentally and theoretically. Our experimental data demonstrate that -- in agreement with previous results on single- and double-junction systems -- Coulomb blockade effects survive even in the strong tunneling regime and are still clearly visible for junction resistances as low as 1 k$\Omega$. We have developed a quasiclassical theory of electron transport in junction arrays in the strong tunneling regime. Good agreement between the predictions of this theory and the experimental data has been observed. We also show that, due to both heating effects and a relatively large correction to the linear relation between the half-width of the conductance dip around zero bias voltage, $V_{1/2}$, and the measured electronic temperature, such arrays are inferior to those conventionally used in the Coulomb Blockade Thermometry (CBT). Still, the desired correction to the half-width, $\Delta V_{1/2}$, can be determined rather easily and it is proportional to the magnitude of the conductance dip around zero bias voltage, $\Delta G$. The constant of proportionality is a function of the ratio of the junction and quantum resistances, $R/R_{\rm q}$, and it is a pure strong tunneling effect.Comment: LaTeX file + five postscript figure

Effect of Carbon Nanotube Aqueous Dispersion Quality on Mechanical Properties of Cement Composite

An effect of the quality of carbon nanotube (CNT) dispersions added to cement on paste mechanical properties has been studied. High-quality dispersions of few-walled CNT (FWCNTs) were produced in two steps. First, FWCNTs were functionalized in a mixture of nitric and sulfuric acids (70 wt.% and 96 wt.%, resp.) at 80 ∘C . Second, functionalized FWCNTs were washed out by acetone to remove carboxylated carbonaceous fragments (CCFs) formed during CNT oxidation. Mechanical test results showed 2-fold increase in the compressive strength of the cement paste prepared from the dispersion of acetone-washed functionalized FWCNTs, which is believed to occur due to the chemical interaction between cement matrix and functional groups (–COOH and –OH). Utilisation of unwashed FWCNTs led to a marginal improvement of mechanical properties of the cement pastes, whereas surfactant-treated functionalized FWCNT dispersions only worsened the mechanical properties.Peer reviewe

Effect of the Tunneling Conductance on the Coulomb Staircase

Quantum fluctuations of the charge in the single electron box are investigated. The rounding of the Coulomb staircase caused by virtual electron tunneling is determined by perturbation theory up to third order in the tunneling conductance and compared with precise Monte Carlo data computed with a new algorithm. The remarkable agreement for large conductance indicates that presently available experimental data on Coulomb charging effects in metallic nanostructures can be well explained by finite order perturbative results.Comment: 4 pages, 5 figure

Carbon Nanotube/Nanofibers and Graphite Hybrids for Li-Ion Battery Application

To improve the electrical conductivity of negative electrodes of lithium ion batteries, we applied a direct CVD synthesis of carbon nanomaterials on the surface of graphite particles. To prepare a catalyst, two alternative approaches were utilized: colloidal nanoparticles (NPs) and metal (Ni and Co) nitrate salt precursors deposited on the graphite surface. Both colloidal and precursor systems allowed us to produce carbon nanofibers (CNFs) on the graphite surface with high coverage under the optimum CVD conditions. Electrical measurements revealed that the resistivity of the actual electrodes fabricated from CNFs coated graphite particles was about 40% lower compared to the original pristine graphite electrodes.Peer reviewe

Quantum Conductance of the Single Electron Transistor

The quantum conductance of the single-electron tunneling (SET) transistor is investigated in this paper by the functional integral approach. The formalism is valid for arbitrary tunnel resistance of the junctions forming the SET transistor at any temperature. The path integrals are evaluated by the semiclassical method to yield an explicit non-perturbation form of the quantum conductance of the SET transistor. An anomaly of the quantum conductance is found if the tunnel resistances are much smaller than the quantum resistance. The dependence of the conductance on the gate voltage is also discussed.Comment: 4 pages including some mathe details of cond-mat/990806

Magnetic-field-dependent zero-bias diffusive anomaly in Pb oxide-n-InAs structures: Coexistence of two- and three-dimensional states

The results of experimental and theoretical studies of zero-bias anomaly (ZBA) in the Pb-oxide-n-InAs tunnel structures in magnetic field up to 6T are presented. A specific feature of the structures is a coexistence of the 2D and 3D states at the Fermi energy near the semiconductor surface. The dependence of the measured ZBA amplitude on the strength and orientation of the applied magnetic field is in agreement with the proposed theoretical model. According to this model, electrons tunnel into 2D states, and move diffusively in the 2D layer, whereas the main contribution to the screening comes from 3D electrons.Comment: 8 double-column pages, REVTeX, 9 eps figures embedded with epsf, published versio

Single-Walled Carbon Nanotube Network Field Effect Transistor as a Humidity Sensor

Single-walled carbon nanotube network field effect transistors were fabricated and studied as humidity sensors. Sensing responses were altered by changing the gate voltage. At the open channel state (negative gate voltage), humidity pulse resulted in the decrease of the source-drain current, and, vice versa, the increase in the source-drain current was observed at the positive gate voltage. This effect was explained by the electron-donating nature of water molecules. The operation speed and signal intensity was found to be dependent on the gate voltage polarity. The positive or negative change in current with humidity pulse at zero-gate voltage was found to depend on the previous state of the gate electrode (positive or negative voltage, respectively). Those characteristics were explained by the charge traps in the gate dielectric altering the effective gate voltage, which influenced the operation of field effect transistor.Peer reviewe

Comparison of ultrasonographic, radiographic and intra-operative findings in severe hip osteoarthritis

Aim of this study was to assess the US findings of patients with late-stage hip OA undergoing total hip arthroplasty (THA), and to associate the US findings with conventional radiography (CR) and intraoperative findings. Moreover, the inter-rater reliability of hip US, and association between the US and Oxford Hip Score (OHS) were evaluated. Sixty-eight hips were included, and intraoperative findings were available on 48 hips. Mean patient age was 67.6 years and 38% were males. OA findings—osteophytes at femoral collum and anterosuperior acetabulum, femoral head deformity and effusion—were assessed on US, CR and THA. The diagnostic performance of US and CR was compared by applying the THA findings as the gold standard. Osteoarthritic US findings were very common, but no association between the US findings and OHS was observed. The pooled inter-rater reliability (n = 65) varied from moderate to excellent (k = 0.538–0.815). When THA findings were used as the gold standard, US detected femoral collum osteophytes with 95% sensitivity, 0% specificity, 81% accuracy, and 85% positive predictive value. Concerning acetabular osteophytes, the respective values were 96%, 0%, 88% and 91%. For the femoral head deformity, they were 92%, 36%, 38% and 83%, and for the effusion 49%, 85%, 58% and 90%, respectively. US provides similar detection of osteophytes as does CR. On femoral head deformity, performance of the US is superior to CR. The inter-rater reliability of the US evaluation varies from moderate to excellent, and no association between US and OHS was observed in this patient cohort.</p