Steering of fogging: control of humidity: temperature or transpiration

Fogging systems are increasingly used to cool greenhouses and prevent water stress. More recently, fogging systems are applied also in relatively low radiation environments (such as The Netherlands), for a better control of product quality than whitewashing and to reduce need for natural ventilation ¿ thus allowing for higher CO2 concentrations to be maintained in the greenhouse. Most commonly the steering of such systems is done by setting an upper limit to the deficit of specific humidity that, whenever exceeded, triggers the fogging system. In both cases, however, one may wonder whether static and pre-fixed set points are the most effective choice. In the experiment presented in this paper, fogging and venting were controlled with the purpose of steering crop transpiration. The desired transpiration rate was the input of an algorithm that calculated on-line the required humidity and air temperature set points in view of the current weather factors. The set points were then the input of a standard P-controller that calculated vent opening and time of operation of the fogging system. In this paper, the resulting climate and actuator control operations are discussed and compared with a similar greenhouse controlled in a traditional fashion. The study concluded that a desired crop transpiration rate (an all-round indicator of crop well-being) could be used to select dynamic set points for the climate control in a greenhouse equipped with a fogging system

The Efficiency of German Universities Some Evidence from Non-Parametric and Parametric Methods

Due to tight public budget constraints, the efficiency of publicly financed universities in Germany is receiving increasing attention in the academic as well as in the public discourse. Against this background we analyze the efficiency of 72 public German universities for the years 1998 to 2003, applying data envelopment and stochastic frontier analysis. Contrary to earlier studies we account for the faculty composition of universities, which proves to be an essential element in the efficiency of higher education. Our main finding is that East German universities have performed better in total factor productivity change compared to those in West Germany. However, when looking at mean efficiency scores over the sample period, West German universities still appear at the top end of relative efficiency outcomes. --universities,efficiency,data envelopment analysis,stochastic frontier analysis

Fiscal Federalism and Demography

The paper examines the effects of demographic change on federal, state and local governments in Germany with a focus on the expenditure side to answer the question, whether demographic change will induce vertical fiscal expenditure imbalances. We present estimates of the impact of demographic change on public spending based on a decomposition of expenditures into almost 30 categories (functions). Our results suggest that demographic change will indeed result in significant vertical expenditure imbalances between the federal and the subnational government sector as well as within the subnational government sector. In addition, the estimates show that the structure of expenditures by function has to be adjusted considerably in order to avoid deficits as demographically induced increases in expenditures in some important functions, such as pension payments, have to be counterbalanced by exploiting potential savings that arise from demographic change in other functions. --fiscal federalism,demographic change,vertical fiscal expenditure imbalances

Cover materials excluding Near Infrared radiation: what is the best strategy in mild climates?

Only about half of the energy that enters a greenhouse as sun radiation is in the wavelength range that is useful for photosynthesis (PAR, Photosynthetically Active Radiation). Nearly all the remaining energy fraction is in the Near InfraRed range (NIR) and only warms the greenhouse and crop and does contribute to transpiration, none of which is necessarily always desirable. Materials or additives for greenhouse covers that reflect a fraction of the NIR radiation have recently become commercially available. Besides lowering greenhouse temperature, a NIR-excluding cover has quite a few side-effects that may become quite relevant in the passive or semi-passive greenhouses typical of mild climates. For instance, the ratio of assimilation to transpiration (the water use efficiency) should increase. On the other hand, by lowering the ventilation requirement, such a cover may hinder in-flow of carbon dioxide, thereby limiting the photosynthesis rate. In addition, there are obviously conditions where the warming up caused by NIR may be desirable rather than a nuisance. NIR-reflecting materials are becoming available in forms that are suitable for various types of applications, such as permanent, seasonal or mobile. By means of a simulation study, we discuss in this paper the best form of application in relation to the external climate and climate management options availabl

New glass coatings for high insulating greenhouses without light losses - energy saving crop production and economic potentials

More than 90% of the Dutch greenhouse area is covered with single glass. Energy losses through the covering are high during the heating period (winter) but energy requirements are also high during the cooling period (summer) in the case of semi-closed greenhouses. Until now, light losses of insulating coverings prevented growers from using double glass or plastic film. However, increasing energy prices allow new developments. Wageningen UR Greenhouse Horticulture studied the possibilities to use modern glass coatings to increase light transmission and save energy. Several glass types (standard glass, 90+ glass, low-iron glass) were covered with different anti-reflection coatings from different producers. Double glasses were produced; their optical properties were determined. It was possible to produce double glasses with new coatings having a higher light transmission than traditional single greenhouse glass (83-85% for hemispherical (diffuse) light, compared to 82-83% for traditional single glass) and a k-value of 3.6 W m-2 K-1 (compared to7.6 W m-2 K-1 of a traditional single glass). Other double glasses were produced using a combination of anti-reflection and modern low-emission coatings, reaching an even lower k-value of ˜2.4 W m-2 K-1, however, showing a slight light loss (78.5% for hemispherical (diffuse) light). Calculations of greenhouse climate (temperature, humidity, CO2) and energy consumptions year-round were carried out with a validated dynamic climate model. Additionally the effects on tomato production (dry matter) were calculated for the different prototypes of coated and insulated glass. Double materials show the highest energy saving with 25-33%, depending on the composition but also low-emission coatings on single glass decrease the energy use with 15-20%. Economic calculations with current tomato and energy prices showed that single and double glasses with anti-reflection coating currently have the highest potential

Demographic Change and Public Sector Budgets in a Federal System

This paper examines the effects of demographic change on public finances in a federal system. We develop a simple methodical procedure to measure the effect of demographic changes on public revenues and expenditures. We apply our method to the local, state and federal government sector as well as on the social security system in Germany. Our results suggest that demographic change will lead to significant vertical fiscal imbalances between the different layers of government. In addition we show, that subnational governments can generate a demographic dividend whereas the social security system and the federal government have to carry an additional burden due to ageing.fiscal federalism, demographic change, sustainability of public finances

Effects of anti-transpirants on transpiration and energy use in greenhouse cultivation

Greenhouse production in North-West Europe consumes a lot of energy. The energy is needed for heating the greenhouse and controlling air humidity. Transpiration of a crop increases the energy use. The aim of this study was to explore the possibilities for the application of anti-transpirants to save energy by reducing crop transpiration without reducing crop yield. Literature and model calculations were used to explore the effects of increased leaf resistances on transpiration, energy use and production in tomato, cucumber and sweet pepper. In literature a large number of compounds are described that act as anti-transpirant. A two to five fold increase in stomatal resistance can be expected from treatment with anti-transpirants. Model calculations for tomato showed that increasing the stomatal resistance (from 2 to 5 times) throughout the whole year leads to substantial yield reduction: crop growth was reduced by 6-19%, while transpiration by 15-42% and consequently energy use by 9-16%. However, in the winter period (beginning of October/end of March) the growth reduction was only 0.3-1.3%, as in this period light levels are low and CO2 concentrations in the greenhouse are relatively high. Raising the (maximum) set-point for CO2 concentration from 1000 ppm to 3000 ppm, increased the actual concentration during day-time from 892 to 1567 ppm (flue gases were the only source of CO2). When the application of anti-transpirants was combined with raising the set-point for CO2 concentration, the model showed no growth reduction due to the application of anti-transpirants, while the annual energy use was reduced by 5.5-10.4% in tomato. Similar results were obtained for sweet pepper (5-9% energy saving) and cucumber (2-5% energy saving). These model calculations show that increasing stomatal resistance by anti-transpirants during the winter period may potentially save a substantial amount of energy (2-10%), without affecting yield of vegetables such as tomato, cucumber and sweet pepper. It is concluded that increasing the stomatal resistance by anti-transpirants in wintertime may lead to substantial energy saving due to the reduced transpiration and need for humidity management, without yield reduction. Such model calculations are useful to analyse beforehand the chances of a good combination of energy saving and yield loss of a possible application. Experiments will be needed to verify the result

Demographic Change and Federal Systems: Some Preliminary Results for Germany

The paper examines the effects of demographic change on federal, state and local government expenditures in Germany. Public spending is decomposed into almost 30 categories (functions) and simple estimates of age cost profiles are derived. Using population forecasts and assuming timeinvariant age cost profiles we estimate the effects of the ageing of the Germany society on the level and structure of expenditures at the three layers of governments. Our results show that subnational governments - state and local governments - can expect demographic savings whereas the federal government will live to see a worsening of its fiscal stance. Thus one should expect that significant vertical expenditure imbalances will arise that - if institutional settings are left unchanged - will ask for an adjustment of revenue distribution within the federation. --Fiscal Federalism,Demographic Change,Vertical Fiscal Imbalances

Public education spending in the German Länder: adjustment to demographic shocks, politics, and cost efficiency

In this dissertation, I examine three major aspects of Germany's education system from an empirical public finance perspective. First, I analyse the effects of strong demographic shifts by considering how the East German Länder responded to the rather dramatic decline in the number of students in primary schools (1993-2002). The demographic shock is a consequence of collapsing birth rates after German Reunification. Previous results from the literature, which rely on data from rather stable demographic periods, suggest that public resources are incompletely adjusted to shrinking cohort size such that large reductions in the student population translate into important increases in spending per student and not in significant reductions of public resources allocated to education. Evidence from a panel of 5 East German Länder over the 1993-2006 period suggests, however, that resource adjustments have been considerable, especially in the years when student cohorts were actually decreasing. Adjustments have been less tight in the period when student numbers stagnated such that the 50% decrease in cohort size has translated into a 25% increase in the teacher/student-ratio. Second, I test whether partisan theory can help to explain the practise of ability-tracking in West Germany. The analysis starts from the empirical observation that in the German education system – where tracking is practised very early compared to other OECD countries – the correlation of parent’s education or income with their children’s track choices is very strong. Thus, students whose parents have a high-education background have significantly higher probabilities of attending a high-ability track. Partisan theory states that political parties when in office pursue the interests of their members and electoral constituencies. Political parties representing highly educated households should therefore support the practise of ability-tracking and advocate higher education spending on the tracks for good students. Evidence from a panel of 10 West German Länder over the 1979-2006 period suggests that German political parties support tracking if they represent high-education households and oppose tracking if they represent lower educated households. The results also suggest that political parties tend to allocate public resources towards the track in which party members’ or party electorate’s offspring is overrepresented. Third, research-oriented higher education in Germany is almost exclusively provided by the public sector, which highlights the importance of measuring university cost efficiency, because market exit and entry – which ensure efficient resource use in the private sector – virtually do not exist (see e.g., Hanushek, 2002). Based on a panel of 70 German public universities over the 1998-2003 period I provide evidence about the factors that benefit efficient resource use in the German higher education landscape. I analyse whether relatively liberal university regulation improves the cost efficiency of public universities as suggested in the literature (see Aghion et al., 2008). The results show that liberal university regulation indeed contributes to more efficient use of resources. Moreover, I find that a prosperous private economic environment seems to reduce university costs

Adverse Childhood Experiences In Special Education

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