Energy Yield Estimation Research Articles

Efficiency model for photovoltaic modules and demonstration of its application to energy yield estimation

A new method has been proposed [W. Durisch, K.H. Lam, J. Close, Behaviour of a copper indium gallium diselenide module under real operating conditions, in: Proceedings of the World Renewable Energy Congress VII, Pergamon Press, Oxford, Elsevier, Amsterdam, 2002, ISBN 0-08-044079-7] for the calculation of the annual yield of photovoltaic (PV) modules at selected sites, using site-specific meteorological data. These yields are indispensable for calculating the expected cost of electricity generation for different modules, thus allowing the type of module to be selected with the highest yield-to-cost ratio for a specific installation site. The efficiency model developed and used for calculating the yields takes three independent variables into account: cell temperature, solar irradiance and relative air mass. Open parameters of the model for a selected module are obtained from current/voltage ( I/ V) characteristics, measured outdoors at Paul Scherrer Institute's test facility under real operating conditions. From the model, cell and module efficiencies can be calculated under all relevant operating conditions. Yield calculations were performed for five commercial modules (BP Solar BP 585 F, Kyocera LA361K54S, Uni-Solar UPM-US-30, Siemens CIS ST40 and Wuerth WS11003) for a sunny site in Jordan (Al Qawairah) for which reliable measured meteorological data are available. These represent mono-crystalline, poly-crystalline and amorphous silicon as well as with copper–indium-diselenide, CuInSe 2 PV modules. The annual yield for these modules will be presented and discussed.

Energy crops: current status and future prospects

AbstractEnergy crops currently contribute a relatively small proportion to the total energy produced from biomass each year, but the proportion is set to grow over the next few decades. This paper reviews the current status of energy crops and their conversion technologies, assesses their potential to contribute to global energy demand and climate mitigation over the next few decades, and examines the future prospects. Previous estimates have suggested a technical potential for energy crops of∼400 EJ yr−1 by 2050. In a new analysis based on energy crop areas for each of the IPCC SRES scenarios in 2025 (as projected by the IMAGE 2.2 integrated assessment model), more conservative dry matter and energy yield estimates and an assessment of the impact on non‐CO2 greenhouse gases were used to estimate the realistically achievable potential for energy crops by 2025 to be between 2 and 22 EJ yr−1, which will offset∼100–2070 Mt CO2‐eq. yr−1. These results suggest that additional production of energy crops alone is not sufficient to reduce emissions to meet a 550 μmol mol−1 atmospheric CO2 stabilization trajectory, but is sufficient to form an important component in a portfolio of climate mitigation measures, as well as to provide a significant sustainable energy resource to displace fossil fuel resources. Realizing the potential of energy crops will necessitate optimizing the dry matter and energy yield of these crops per area of land through the latest biotechnological routes, with or without the need for genetic modification. In future, the co‐benefits of bioenergy production will need to be optimized and methods will need to be developed to extract and refine high‐value products from the feedstock before it is used for energy production.

Energy yield of passive stall regulated fixed speed wind turbine with optimal rotor speed

This paper presents a lucid mathematical deduction of optimal rotor speed to maximize the energy yield of wind machines with passively stall regulated Fixed Speed Scheme (FSS). The power captured at a particular wind speed is dictated by the turbine characteristics in conjunction with the type of drive (variable speed or fixed speed). However, the energy yield estimation requires knowledge of wind speed frequency distribution. Studies have revealed that the probability density function could be fairly represented by Weibull distribution with wind velocity being suitably scaled. Considering these facts, the concept of Maxima Energy Indicator (MEI) for FSS has been developed from first principles to obtain optimal rotor speed ( w opt ) numerically. Alternatively, MEI is further simplified using Incomplete Gamma Function which forms the mathematical solution for w opt . It turns out that w opt of FSS varies with location owing to changes in Weibull parameters. Therefore, it is deceptive to compare the energy yields of FSS with its counterpart Variable Speed Scheme (VSS) without taking into consideration the optimum rotor speed of FSS. With this motivation, computations have been performed which compare the annual yields of both the alternatives, the rotor speed of the low cost stall regulated FSS being optimized.

The simplest method for calculating energy output and Gurney velocity of explosives

Two correlations are introduced for calculating Gurney velocity as a useful parameter for thermochemical estimation of explosive energy output. For C a H b N c O d explosives, only the chemical composition of high explosive as well as its condensed or estimated gas phase heat of formation, which later is calculated by group additivity rules, is needed for calculating Gurney velocity. The introduced simple correlations in the present work may be applied to any explosive that contains the elements of carbon, hydrogen, nitrogen and oxygen with no difficulties at any loading density. There is no need to use any assumed decomposition reaction in present work. Gurney velocity are calculated for different pure and explosive formulations and compared with measured Gurney velocity at specified loading density. The results show that the agreement is good for present method as compared to previous correlations.

Technical assessment of the use of a small-scale wind power system to meet the demand for electricity in a land aquafarm in Taiwan

Due to the widespread aquaculture at coastal area in Taiwan and high wind power potential in the sites, it is worthy to carry out the technical potential assessments of small-scale wind power system used for aquaculture in Taiwan. The present work analyzed wind power potential, described the practical installation, measured the actual energy output, verified the reliability of the energy output estimation method and elucidated important considerations associated with the use of this estimation method. The relationship between the actual energy generated and the wind speed characteristics were thus introduced. The power quality produced by a small-scale wind power generator was also evaluated.

A pulsed hydrogen fluoride amplifier initiated by vibrational excitation of HF molecules by laser radiation

An H2 — F2 amplifier initiated by a resonant vibrational excitation of HF molecules by a pulsed hydrogen fluorine laser is theoretically simulated. Numerical calculations are performed with allowance for an inhomogeneity of the initial HF concentration that appears due to specific features of preparing the experimental laser mixture. The estimated energy output for a mixture of H2 : F2 : O2 : He = 100 : 600 : 30 : 100 Torr is 10 — 20 JL-1 for an average initial HF pressure along the amplifier axis of 0.1 — 0.5 Torr. The laser-radiation energy gain on a length of 4 m is 5 — 10.

Energy output estimation for small-scale wind power generators using Weibull-representative wind data

Estimation of energy output for small-scale wind power generators is the subject of this article. Monthly wind energy production is estimated using the Weibull-representative wind data for a total of 96 months, from 5 different locations in the world. The Weibull parameters are determined based on the wind distribution statistics calculated from the measured data, using the gamma function. The wind data in relative frequency format is obtained from these calculated Weibull parameters. The wind speed data in time-series format and the Weibull-representative wind speed data are used to calculate the wind energy output of a specific wind turbine. The monthly energy outputs calculated from the time-series and the Weibull-representative data are compared. It is shown that the Weibull-representative data estimate the wind energy output very accurately. The overall error in estimation of monthly energy outputs for the total 96 months is 2.79%.

Alternative Foraging Strategies and Resource Allocation by Male and Female Wandering Albatrosses

Allocation processes play a central role in life history theories. Yet very few studies have been carried out on the link between foraging and life history in the context of allocation of resources. Here we report a study examining the relationship between foraging and allocation of resources in the Wandering Albatross Diomedea exulans of Crozet Islands. We simultaneously studied individual foraging strategies at sea and differential allocation to reproduction and storage by measuring the energy supplied to chicks and the variation of body mass of the adult. Satellite tracking and continuous monitoring of nest attendance by adults showed that while rearing a chick Wandering Albatrosses have two specific alternative foraging strategies. They either forage in short trips, short in duration and close to the colony over the southeastern slope of the peri-insular shelf, or in long trips far from the colony in the oceanic waters north of Crozet. On average, birds made five successive short trips before making a long trip. Chicks received a meal every 1.8 d and were fed with fresh prey, 72% squid and 24% fish, and a liquid fraction composed of oil and water. During short trips birds appear to rely to a great extent on Moroteuthis ingens, a squid species probably available in large numbers at the southeastern edge of the Crozet shelf. The measure of energy flows indicates that 74% of the energy delivered to the chick comes from short trips, whereas only 33.8% of the total energy is gained at sea during these trips. Males spent a greater proportion of their time foraging in short trips than females, and consequently chicks received 61.3% of their meals from males and 38.7% from females. Adult birds tended to lose mass after short trips and to lose more mass with increased duration of short trips, whereas they gained mass after long trips. They initiated long trips when their body mass was low. Although Wandering Albatrosses are able to provision their chicks at a rapid rate because of the proximity of an abundant resource, birds still have to forage far from the colony to restore their body condition. Estimates of energy yield explain this paradox, as they suggest that the rate at which prey is caught during short trips in shallow waters is half that during long trips in oceanic waters. The significance of the twofold foraging strategy in relation to food availability and foraging efficiency is discussed.

ALTERNATIVE FORAGING STRATEGIES AND RESOURCE ALLOCATION BY MALE AND FEMALE WANDERING ALBATROSSES

Allocation processes play a central role in life history theories. Yet very few studies have been carried out on the link between foraging and life history in the context of allocation of resources. Here we report a study examining the relationship between foraging and allocation of resources in the Wandering Albatross Diomedea exulans of Crozet Islands. We simultaneously studied individual foraging strategies at sea and differential allocation to reproduction and storage by measuring the energy supplied to chicks and the variation of body mass of the adult. Satellite tracking and continuous monitoring of nest attendance by adults showed that while rearing a chick Wandering Albatrosses have two specific alternative foraging strategies. They either forage in short trips, short in duration and close to the colony over the southeastern slope of the peri-insular shelf, or in long trips far from the colony in the oceanic waters north of Crozet. On average, birds made five successive short trips before making a long trip. Chicks received a meal every 1.8 d and were fed with fresh prey, 72% squid and 24% fish, and a liquid fraction composed of oil and water. During short trips birds appear to rely to a great extent on Moroteuthis ingens, a squid species probably available in large numbers at the southeastern edge of the Crozet shelf. The measure of energy flows indicates that 74% of the energy delivered to the chick comes from short trips, whereas only 33.8% of the total energy is gained at sea during these trips. Males spent a greater proportion of their time foraging in short trips than females, and consequently chicks received 61.3% of their meals from males and 38.7% from females. Adult birds tended to lose mass after short trips and to lose more mass with increased duration of short trips, whereas they gained mass after long trips. They initiated long trips when their body mass was low. Although Wandering Albatrosses are able to provision their chicks at a rapid rate because of the proximity of an abundant resource, birds still have to forage far from the colony to restore their body condition. Estimates of energy yield explain this paradox, as they suggest that the rate at which prey is caught during short trips in shallow waters is half that during long trips in oceanic waters. The significance of the twofold foraging strategy in relation to food availability and foraging efficiency is discussed.

Leucocyte and erythrocyte counts during a multi-stage cycling race ('the Milk Race').

Venous blood samples were taken from eight competitors in mid-evening after a racing day, and in the early morning before the next day's race, three times during the course of the Milk Race, 1992. These were used to gather information about the changes in circulating leucocyte levels in response to the exceptionally high sustained daily workload required during a major multi-stage race. The primary objective was to provide knowledge of 'normal' values against which future clinical judgements of abnormality might be made in these unusual circumstances. During the race, estimated energy output was about 25 MJ (6000 kCal)/day. The mean total circulating leucocyte numbers (per litre of blood), and those of individual leucocyte classes (neutrophil, lymphocyte, monocyte, eosinophil and basophil) were all inside the normal range both in the morning and in the evening. Evening counts were, however, 30-50% higher than morning counts, for all classes except eosinophils. We conclude that individual clinical decisions about leucocyte levels can best be made using normal (sedentary man) values if a morning sample is taken.

Financial Analysis of Solar Energy Applications with Endogenous System Sizing

AbstractThis paper is concerned with analysis of economic feasibility of solar energy systems. Methodology for estimating energy output from different sized systems is briefly presented, and this is used to determine technical coefficients for a mixed integer model which optimizes the size of the solar heating unit for a particular use. An empirical example of hot water heating on a Georgia dairy is presented. Cost curves are provided for the dairy example to illustrate the effect of sizing on the economic feasibility of solar heating and to elucidate the structure of the optimal sizing decision.

Circulatory Strain, Estimated Energy Output and Catecholamine Excretion in Norwegian Coastal Fishermen

Abstract Circulatory strain and energy output were determined in 24 Norwegian coastal fishermen during a total of 35 work-days by indirect assessment based on computerized analysis of the continuously recorded heart rate by portable tape recorders. Urinary excretion of catecholamines was assayed as an index of stress response. The average, estimated energy expenditure of all activities on board during the whole day amounted to the equivalent of 0·9–1·11/min oxygen uptake and corresponded to 34–39% of the fishermen's maximal aerobic power with occasional peaks up to 80%. The heart rate exceeded 50% of the fishermen's heart rate reserve for 9–23% of the observation periods. The most strenuous activities were pulling in the seine with a power block (oxygen uptake up to 2·7 1/min) and unloading the catch, taxing the subjects by more than 50% of their maximal aerobic power for two-thirds of the duration of these activities. Continuous monitoring of the heart rate revealed the intermittent character of practically all activities on board. In a parallel study the circulatory strain, energy output and catecholamine excretion were investigated in eight catch handlers on land during a total of 12 work-days. Handling the catch entailed a mean oxygen uptake of 0·9 1/min, corresponding to about 34% of the maximal aerobic power of the workers, with peak values considerably lower and of shorter duration than in the fishermen. The average (median) urinary excretion of norepinephrine (NE) and epinephrine (E) during the work-day was high in both investigated groups, 72 ng/min NE and 24 ng/min E in the fishermen, and 59 ng/min NE and 15 ng/min E in the catch handlers. The epinephrine excretion in the fishermen was significantly higher (p≤0·01) than in the catch handlers.

Blood levels of adrenergic amines during exercise.

Blood levels of adrenergic amines during exercise.